# M³ amplifier build discussions thread



## amb

Now that people are beginning to receive their boards and parts, it's good time to close out the "M³ project announcement" thread and start anew here.

 Have fun building your new amps! 
	

	
	
		
		

		
			





 Must-read links for builders:
amb's M³ site
Morsel's M³ site


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## MisterX

Quote:


 Have fun building your new amps! 
 

Can't, they are not here yet. 
	

	
	
		
		

		
		
	


	




 Do you know of a source for the Wima MKS-2 1uF C2/C8's? 
 Mouser doesn't stock them and as such you have to order 110 of them. 
	

	
	
		
		

		
		
	


	



 I am gonna order them anyhow but the other people might like to know of a source for them

 If you want to split half the order email me.


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## amb

Quote:


  Originally Posted by *MisterX* 
_Do you know of a source for the Wima MKS-2 1uF C2/C8's?_

 

Does it have to be Wima? You can substitute with Vishay-Roederstein MKT1817 1uF box caps, mouser part #75-MKT1817510064.

 Edit: I just checked and Mouser has Wima MKS-2 1uF 63V 10% in stock:
 Mouser #505-MKS21/63/10, minimum order quantity is 10, but since you need 9 per board, it's not a problem. Also, they have Wima MKS-2 1uF 100V 10% #505-MKS21/100/10 in stock and available in single quantities (or multiples of 10/100/500, etc).


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## MisterX

Nope... they don't have to be wimas by no stretch of the imagination.

 Do you know how that works though? 

  Quote:


  Originally Posted by * buyers first question* 
_I don't want those green looking caps can you replace them?_


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## ub312g0d

In AMB's MMM building guide it shows that the rca's ground must be connected to the volume pot via the case. Im planning on a wooden case so was wondering if it would be necesary to connect the two inside of the case?


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## MisterX

As I rech over ond check the status of the fume extractor I have to wonder WTH was I thinking.... 
 Thanks for reminding me that 63 volt caps also fit.


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## amb

Quote:


 I don't want those green looking caps can you replace them? 
 

LOL.


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## amb

Quote:


  Originally Posted by *ub312g0d* 
_In AMB's MMM building guide it shows that the rca's ground must be connected to the volume pot via the case. Im planning on a wooden case so was wondering if it would be necesary to connect the two inside of the case?_

 

The volume pot's body needs to be grounded or else you'll induce hum when you touch the volume knob. If your front panel isn't metal to connect the pot body to the signal ground, then you should add a small length of wire, secure it to the pot body (loosen one of the ALPs pot's screws on the back and hook the wire onto it before tightening it again, then solder the other end to one of the IG pads nearby).


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## phobus

Quote:


 0.100" 2-circuit pin header, plug and crimp terminals 
 

I'm not sure what to order from digikey. Can anyone help me with part numbers please?

 Thanks


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## amb

Quote:


  Originally Posted by *phobus* 
_I'm not sure what to order from digikey. Can anyone help me with part numbers please?_

 

Look further down the parts list page, under "Connectors", and it shows you the options. You would use these if you want to be able to unplug all connections and remove the PCB without desoldering any wires. If this is not an issue then you could simply solder the wires directly to the PCB pads.


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## Edwood

LOL, are the Wima MKS-2's really that much better than the Vishay Roederstein's?


 Other than being more color coordinated with Cerafines?

 -Ed


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## Syzygies

Anyone who wandered into this thread by accident, *start here:*

Amb's M³ Page 
Morsel's M³ Page

 So, any reason those of us who want to put off dealing with the power supply issue for now can't just use a series of two lead acid batteries? RadioShack sells tiny ones, my barbeque pit computer uses a "lawn & garden" battery, sort of a 1/3 size car battery.

 Wouldn't this sound better than all but the best regulated supplies? Or is there a current issue?

 I'd have to check, a fully charged pair might exceed 27 volts. That's an issue with many op amps, as amb notes.

 (There is a spectrum for lead acid batteries. Car batteries put out amazing amounts of current briefly to start the engine, but don't like repeatedly being fully drained. Marine batteries are in between, golf cart batteries are the other extreme, like to be taken fully down and back up hundreds of times. Has to do with internal distance between plates. My dad uses golf cart batteries for his solar panels on his summer cabin.)


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## stadams

Is anyone working on a BOM that includes all the parts recommendations by amb? If there was a general consensus on suppliers, maybe narrowing it down to three or four, the BOM would not be to bad. An interactive Excel spreadsheet would be nice. And for those lucky enough to not have Excel maybe a .pdf file would be nice. Although you would have to calculate the prices by hand when using the .pdf file.

 Later,


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## ub312g0d

syzygies, I cant see any reason why 2 sealed lead batteries in series. Im not sure about how much power the little rat shack ones have in them but any of the larger sized ones would be nice for testing and act like the perfect power supply. Seems like a decent solution for testing and such anyway. Hell, It would even be "portable" if you did. Just put it all in a backpack and hope the straps dont get ripped off.
 Of course if they're putting out that much voltage fully charged just watch what opamps you put in there, but of course you mentioned that already.


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## fool

Quote:


  Originally Posted by *Syzygies* 
_Anyone who wandered into this thread by accident, *start here:*

Amb's M³ Page 
Morsel's M³ Page
_

 

Thanks! Until this thread I didn't realized the MMM project had progressed this far. 
	

	
	
		
		

		
		
	


	




 -fool


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## pabbi1

My current plan is to build two amps. The first configuration is with a STEPS set at 32v for OPA637 /627, and bass boost. The second will be with AD8610 and I happen to have one of these GHOF 1-28, 28v, 1a laying around, and plan to case it seperately. 

 Good, bad or ugly?


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## amb

pabbi1, 28V will take you close to the absolute maximum voltage rating of the AD8610 even after accounting for the voltage drop of the cap multiplier Q5 transistors and D1 diode. You're leaving little margin for error. Be sure that the power supply really puts out no higher than 28V under any circumstance or you'll risk blowing opamps.

 For everyone's reference, D1, Q5+ and Q5- should drop about 0.8V each. So that's a total of 2.4V drop. While 28V - 2.4V = 25.6V seems safe (AD8610 is rated at max 27.3V), prudence dictates allowing about 2V minimum for error.


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## pabbi1

Thanks... but 1.0a is OK? Any other way to reduce the voltage a bit, like adjusting D1, or Q5?


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## Syzygies

Quote:


  Originally Posted by *amb* 
_For everyone's reference, D1, Q5+ and Q5- should drop about 0.8V each. So that's a total of 2.4V drop. While 28V - 2.4V = 25.6V seems safe (AD8610 is rated at max 27.3V), prudence dictates allowing about 2V minimum for error._

 

So I fully charged my barbecue pit lead acid battery tonight, and it measured just under 14V. That's 28V for two, drops to no more than 26V by amb's computation, that's just barely safe.


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## amb

Quote:


  Originally Posted by *pabbi1* 
_Thanks... but 1.0a is OK? Any other way to reduce the voltage a bit, like adjusting D1, or Q5?_

 

There is nothing to adjust on these. Just measure your psu's output voltage to make sure it really is 28V and not 28.xV where x is a large fraction, and you'd be ok. If you're a little over, you could double up on D1 (i.e., put two 1N4001 diodes in series) to drop the voltage a bit more.

 1A rating is fine, as long as you're not cranking the bias to exceed that.


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## palchiu

Dear AMB,

 Is this a good idea? 
 Use two car battery makes a 24V to amp?
 If it's possible, hope can gets more clean sound.

 Thanks!

 Pal


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## amb

Quote:


  Originally Posted by *palchiu* 
_Is this a good idea? 
 Use two car battery makes a 24V to amp?
 If it's possible, hope can gets more clean sound._

 

While it's possible to do that, you have to make sure that the car batteries aren't putting out more than what the opamps could tolerate. Also, even car batteries will eventually become discharged, and they do not like to be completely and repeatedly discharged (will shorten the lifespan). So, you will have to put the batteries on a charger when you aren't using the amp. To me that seems like a major inconvenience.

 I also don't think a car battery will really offer "cleaner sound" than a good regulated power supply. A car battery actually could be noisier than a regulated power supply. While I haven't done any noise testing of a car battery myself, I point you to the following article about voltage regulator noise. The part of interest is at the end of Page 4, where a lead-acid battery is tested for noise. Car batteries are of the lead-acid variety, and this test shows worse noise performance than a regulated power supply under load:
http://www.tnt-audio.com/clinica/reg..._noise1_e.html


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## pabbi1

To implement bass boost, only the pot and cbb are required? Any additional shunt/jumper?


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## MisterX

Quote:


  Originally Posted by *amb* 
_Edit: I just checked and Mouser has Wima MKS-2 1uF 63V 10% in stock:
 Mouser #505-MKS21/63/10, minimum order quantity is 10,_

 

They lied .... got to order at least 50 of them. 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by * Ed* 
_LOL, are the Wima MKS-2's really that much better than the Vishay Roederstein's?_

 

No... in fact i prefer the green ones but try dispelling the myth that Wimas are the best 5 times a day and it gets old real fast. 
	

	
	
		
		

		
		
	


	



 Sometimes it's easier when you don't provoke the questions.


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## amb

Quote:


  Originally Posted by *pabbi1* 
_To implement bass boost, only the pot and cbb are required?_

 

Yep.

  Quote:


 Any additional shunt/jumper? 
 

Nope.


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## palchiu

Thanks! AMB


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## pabbi1

Where are the 2w R9 available?


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## MisterX

Mouser #262-1.0 among others.


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## pabbi1

I meant other than Xicon... is that all that's available? Everything esle I have is Vishay (or Holco), and wanted to keep that, if at all possible.


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## z2trillion

What does changing the value of R9 to 10 ohms do the sound? It changes the output impedance of the amp right?


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## amb

pabbi1, if you must use Vishay-_something_ (although I am not sure why that is important), there is Vishay-BC PR02 series 1 ohm 2W metal-film resistors for R9. Mouser #594-5083NW1R000J

 z2trillion, do not change R9 to 10 ohms. If you do you won't be able to properly adjust the bias of the MOSFETs without also changing the value of R7. Changing R9 to 10 ohms will increase the output impedance somewhat, but more importantly it will reduce available voltage swing because of the voltage drop across them will be 10x compared to 1 ohm given a particular quiescent current setting.


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## pabbi1

Thanks, AMB, just trying to be consistent... otherwise, I'd always have that nagging feeling, especially as no one ever *recommends* Xicon.


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## Nisbeth

Quote:


  Originally Posted by *MisterX* 
_No... in fact i prefer the green ones but try dispelling the myth that Wimas are the best 5 times a day and it gets old real fast. 
	

	
	
		
		

		
			



_

 

My bet is that the myth started in the US because they're made in Europe and they're hard to get 
	

	
	
		
		

		
		
	


	



 Over here where even "ye olde electronics shop around the corner" has them, no one seem to think much of Wima caps (except me, but that's because I'm a fashion victim who likes the color 
	

	
	
		
		

		
		
	


	




)

 /U.


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## thrice

Quote:


  Originally Posted by *MisterX* 
_ the green ones but try dispelling the myth that Wimas are the best 5 times a day and it gets old real fast. 
	

	
	
		
		

		
		
	


	



 Sometimes it's easier when you don't provoke the questions. 
	

	
	
		
		

		
		
	


	


_

 

LOL-testify!


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## morsel

I like the blue BC Components (now a division of Vishay) film caps.


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## jamont

Here's a look at mine in progress:






 I've done everything except the output transistors and bass boost, I need mounting hardware for the heatsinks before proceeding.

 Next step is to mount the output transistors, check things out and do the biasing, check the offset, then do some listening tests and measurements.

 At that point, I may adjust the gain, and when that's set, I'll figure out what to use for the bass boost.

 Thanks to morsel and amb for another great project!


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## amb

jamont, looks great!


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## jamont

Quote:


  Originally Posted by *amb* 
_jamont, looks great! 
	

	
	
		
		

		
		
	


	


_

 

Thank you!

 BTW, do you think it matters if the heatsinks are attached with self-tapping screws or is it preferable to tap the heatsinks and use machine screws? My thought offhand was that self-tapping screws would be easier and should be fine since I won't be disconnecting the heatsinks after final assembly.


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## DigiPete

jamont said:
			
		

> Here's a look at mine in progress:
> 
> 
> 
> ...


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## amb

Quote:


  Originally Posted by *jamont* 
_do you think it matters if the heatsinks are attached with self-tapping screws or is it preferable to tap the heatsinks and use machine screws?_

 

Either is fine as long as it's mechanically secure.


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## jamont

Quote:


  Originally Posted by *DigiPete* 
_ouuuu, ahhhh!!! I like the blue 
	

	
	
		
		

		
		
	


	




 What parts did you order to get blue, also what caps did you choose if one might ask?_

 

Resistors are Xicon MF 1/4 W and MO 2W, trimpots are Bourns 3296W, small caps are BC 370 and BC 416, electrolytics are Nichicon UPW. I wasn't trying to get everything blue, it just came out that way.


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## amb

Quote:


  Originally Posted by *jamont* 
_I wasn't trying to get everything blue, it just came out that way._

 

Accidentally stylish!


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## n_maher

Quote:


  Originally Posted by *jamont* 
_Here's a look at mine in progress:_

 

jamont,

 And idea what the total parts cost was? I know that there are a bunch of us waiting to see how much this is going to hurt. 
	

	
	
		
		

		
		
	


	




 Thx,

 Nate


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## morsel

Nice job so far, Jamont. I see you are using my beloved BC caps. 
	

	
	
		
		

		
		
	


	




 Go with self-tapping screws, as they are convenient and the heat sinks are unlikely to be removed.


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## jamont

Quote:


  Originally Posted by *n_maher* 
_And idea what the total parts cost was? I know that there are a bunch of us waiting to see how much this is going to hurt. 
	

	
	
		
		

		
		
	


	


_

 

I had most resistors, caps, and opamps on hand already, so I've spent under $100 so far, mostly on the board and related parts. If you're starting from scratch it should be comparable with the PPA, maybe a bit less.


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## jamont

I've got the heatsinks mounted and I'm setting the bias now. I'm wondering about the opamp bias measurement, shouldn't we be measuring the voltage across R5 rather than R7?


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## morsel

Quote:


 I'm wondering about the opamp bias measurement, shouldn't we be measuring the voltage across R5 rather than R7? 
 

Yes, use R5. You just found a typo in amb's documentation.


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## amb

Quote:


  Originally Posted by *morsel* 
_Yes, use R5. You just found a typo in amb's documentation._

 

Oops, thanks for catching that. 
	

	
	
		
		

		
			





 Now fixed.


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## jamont

Here's the board on the desktop, coming to thermal equlibrium for the final bias checks:






 Next step will be to hook up temporary input/output jacks for testing.

 Eventually it will wind up in a custom Pars-metal case (I hope), but that's a ways off.


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## Magsy

Quote:


  Originally Posted by *jamont* 
_Here's the board on the desktop, coming to thermal equlibrium for the final bias checks:






 Next step will be to hook up temporary input/output jacks for testing.

 Eventually it will wind up in a custom Pars-metal case (I hope), but that's a ways off._

 

Ohh I'm jealous, hope my board has arrived by the time I get home


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## steinchen

Quote:


  Originally Posted by *Magsy* 
_Ohh I'm jealous, hope my board has arrived by the time I get home 
	

	
	
		
		

		
		
	


	


_

 

we have to wait a further week due to custom process time etc, I'm afraid :/


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## jamont

I've hooked up in and out for testing. The offset is 1.6 mV on one channel, less than 1 mV on the others. I'm not really concerned about the 1.6 mV, but I'd like to get it under 1 mV like the others - any suggestions?

 I took a quick look on the scope and the square wave response is outstanding, the best I've seen on a DIY amp, no question. There is not a hint of overshoot. At the highest frequency of my dipy function generator (150kHz), the leading edge is becoming just slightly rounded (I'm using the 33pf caps). Great stability and bandwith, excellent engineering job on this!

 With AKG K501's and AT A900's, the sound is excellent, as expected. I'll leave detailed listening rewiews to those more qualified, but this appears to me to be a potential PPA killer.


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## amb

Hi jamont, congratulations!

 1.6mV DC offset is very low and there is no need to worry about it. Short of swapping opamps there is really nothing you could do to reduce it further.

 As you state your amp is already a superb performer. If for some reason you want to make the square wave even more "square" in the ultrasonics, see the notes on the my parts list web page about further optimizing the value of the L and R channels' compensation caps based on the opamp you're using and the voltage gain.

 Happy listening!


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## jamont

Quote:


  Originally Posted by *amb* 
_1.6mV DC offset is very low and there is no need to worry about it. Short of swapping opamps there is really nothing you could do to reduce it further.

 As you state your amp is already a superb performer. If for some reason you want to make the square wave even more "square" in the ultrasonics, see the notes on the my parts list web page about further optimizing the value of the L and R channels' compensation caps based on the opamp you're using and the voltage gain._

 

Thanks for your comments! I'm impressed by all the work you did tweaking C1 for different opamps, but I think I'll leave it as is unless I find a need for a low power RF amplifier


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## Ic3Floe

Quote:


  Originally Posted by *n_maher* 
_jamont,

 And idea what the total parts cost was? I know that there are a bunch of us waiting to see how much this is going to hurt. 
	

	
	
		
		

		
		
	


	




 Thx,

 Nate_

 

I second that request. Total bill was how many "bones?"


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## thrice

Here we go:
















 I don't think my iPod Earbuds have ever sounded so good


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## individual6891

Looking good thrice


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## amb

Coolness thrice. Another M³ is born!


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## n_maher

I have an excel spreadsheet of one possible configuration of an MMM with bass boost. I'd love to have someone check it before putting it up for public consumption. It's pretty basic but it does hot link you to all the parts and sources everything from either or AMB or Mouser (minus the case, knobs and ins/outs). 

 PM me if you're up for the task, also it'd make a good starting point for someone looking to compare configurations and costs and I'm happy to give it to whoever wants it.

 Nate


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## amb

Quote:


  Originally Posted by *n_maher* 
_(excel spreadsheet)
 PM me if you're up for the task, also it'd make a good starting point for someone looking to compare configurations and costs and I'm happy to give it to whoever wants it._

 

I can have a look. Send it to me.


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## Syzygies

Quote:


  Originally Posted by *n_maher* 
_for public consumption._

 

I always assumed anything put up here was for public design review, one only "consumes" what one understands, at one's own risk.

 In any case, my spreadsheet is in progress as I pick parts, I'd love to see yours if you think you're done.


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## n_maher

amb has the spreadsheet for review. I'll be happy to share it with everyone else after any comments are taken under consideration.

 And my only fear about releasing it right now would be that I made some idiotic mistake and that some unknowing individual might waste time and money as a result. 

 Nate


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## MisterX

Let me share what I put together so far
 (resistor part numbers are not provided)
 Mouser
 --------------------------------------------------------------------------
 BIAS-OP 652-3296W-1-102 
 BIAS 652-3296W-1-502 

 C1 80-C315C330J1G 
 C2/C8 505-MKS21/63/10 (*you got to order 50*)
 C3 80-C315C221J1G 
 C4/C5 647-UPW1H101MPD (100uF 50 volt)
 C6 505-MKP20.1/100/5 
 C7 647-UPW1H331MPH (330uF 50V)
 Cbb 505-MKP20.22/100/5 

 R9 262-1.0 (Xicon) 594-5083NW1R000J (Vishay) 



 Q2/Q5+ 511-2N3904 (ST) 
 Q5- 511-2N3906 (ST) 
 Q3/Q4 512-2N5486 
 Q6 512-2N5484

 D1 512-1N4001GP
 TLE 595-TLE2426CLP

 Aavid-Thermalloy 531202B00000 (2") 532-531202B00
 TO-220 heat sink mounting Kit 532-4880 (S) (M)
 Thermal grease (wakefield) 567-120-2
 DIP Socket 575-113308



 Digikey
 --------------------------------------------------------------------------
 BIAS-OP 3296W-102-ND
 BIAS 3296W-502-ND

 C1 399-1949-ND 
 C2/C8 BC1622-ND
 C3 399-1901-ND 
 C4/C5 P10323-ND (100uF 50 volt)
 C6 BC2054-ND 
 C7 P11258-ND (330uF 50V)
 Cbb BC2062-ND

 Q1+ IRFZ24N-ND
 Q1- IRF9Z34N-ND
 Q2/Q5+ 2N3904RLRAOSCT-ND (OnSemi cut tape)
 Q5- 2N3906RLRAOSCT-ND (OnSemi cut tape)


 R9 P1.0W-2TR-ND (ECG series) 
 D1 1N4001GICT-ND 

 OPAMP AD8610AR-ND
 AD8065AR-ND
 AD843JN-ND 
 AD845JN-ND 
 OPA637AP-ND 
 OPA627AP-ND

 TLE 296-1994-1-ND (TLE2426CLPR)

 Heat sink Aavid-Thermalloy 531102B00000 HS284-ND
 Thermal grease HS243-ND
 DIP Socket ED5308-ND
 Aries 08-350000-10 A724-ND


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## amb

I have updated my parts list page with Mouser and Digi-key part numbers under the "Parts Recommendations & Options" section. Check it out.


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## steinchen

both Q3 and Q4 are 2n5486, do I have to pick (hand select) a jfet for Q4 with IDSS min > IDSS max of Q3 ? Or take a different combination (2n5484/2n5486 or 2n5486/pn4392) ?


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## amb

Quote:


  Originally Posted by *steinchen* 
_both Q3 and Q4 are 2n5486, do I have to pick (hand select) a jfet for Q4 with IDSS min > IDSS max of Q3 ? Or take a different combination (2n5484/2n5486 or 2n5486/pn4392) ?_

 

Don't use the 2N5484 here. The Idss would be too low for the intended application.

 If you want to hand pick, use the 2N5486 with the higher Idss for Q4, however this is not critical, because there is a 1K pot to dial up desired current.


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## thrice

Sometimes I just can't wait 
	

	
	
		
		

		
			





 So I went and ordered a Par-Metals case, here are some pics:

 Par-Metals Series 20 case 12"W X 3"H X 8"D (20-120803 it think?)















 I'm using the 1.5" heatsinks so keep that in mind. With 1.5" Heatsinks and .75" standoffs you get about .5" clearance from the top of the case. To the left is a STEPS board for reference.

 Some issues:

 1). The holes in the PCB for mounting screws do not line up with the ones pre-drilled into the case. Keep in mind there are only two predrilled holes in the case for mounting so you would have to drill two new ones anyway. The holes in the case are roughly 6" apart (center of hole to center of hole running the depth of the case) while the holes on the PCB are roughly 6.5" apart.

 2). If you are using the ALPS pots for volume and bass boost and you want them to mount in the center of the panel, you're going to have to mount the board as close to the front panel as possible which means drilling through the bottom plate as well as the front frame for the front panel.

 Just thought people would like to see some pics.


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## Pars

Those bastages sent you MY case! 
	

	
	
		
		

		
		
	


	




 Seriously, I have had that exact case on order also since Friday, Feb. 25th (12x8x3, natural anodize, countersunk screws, no top vents).

 Chris


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## thrice

Quote:


  Originally Posted by *Pars* 
_Those bastages sent you MY case! 
	

	
	
		
		

		
		
	


	




 Seriously, I have had that exact case on order also since Friday, Feb. 25th (12x8x3, natural anodize, countersunk screws, no top vents).

 Chris_

 

Oh my has top vents and the screws are not countersunk...just a stock job, crazy thing is I ordered it on Monday...that's fast!


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## n_maher

If anyone would like an excel spreadsheet that lays out all of the major components that you would need to populate an MMM board just PM me your email address. Or if someone with FTP ability would like to host it that would be nice. 

 The spreadsheet offers one possible combination of parts that have been reviewed by a member of the design team. It is by no means the cheapest or the most expensive that you could select. And it is a long way from being as comprehensive as the PIMETA spreadsheet that was circulated a while ago. It does however, offer hot-links to all of the mouser parts that you need. So just click the spreadsheet, add to Mouser order, and you're on your way. It also makes maximum use of amb's audio shop, obviously you can get some of these parts from other vendors if you choose to do so. [edit] It also includes all of the required resistors for the stock MMM gain configuration. [/edit]

 Last but not least, I reserve the right to stop offering this spreadsheet if I get 100PM's. I work full time in addition to being a Head-fi addict so please allow a day or so before you send me another PM.

 Nate


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## Nisbeth

I can host it. Sent you a PM 
	

	
	
		
		

		
		
	


	





 /U.


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## n_maher

Nisbeth should have the spreadsheet now. Please hold off on sending PM requests until we see if hosting it on Nis's site will be sufficient.

 N


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## Nisbeth

File is up: http://www.nisbeth.dk/uffe/files/head-fi/mcubed-bom.xls


 /U.


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## MisterX

Quote:


  Originally Posted by *thrice* 
_1). The holes in the PCB for mounting screws do not line up with the ones pre-drilled into the case. Keep in mind there are only two predrilled holes in the case for mounting so you would have to drill two new ones anyway. The holes in the case are roughly 6" apart (center of hole to center of hole running the depth of the case) while the holes on the PCB are roughly 6.5" apart.
_

 


 Those holes are for mounting the feet.


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## thrice

Quote:


  Originally Posted by *MisterX* 
_Those holes are for mounting the feet. 
	

	
	
		
		

		
		
	


	


_

 

I knew that.


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## Syzygies

I asked this in the announcement thread, but I never got an answer, and now it's time to buy.

 I definitely am going to populate D1. Can I use a Schottky diode, as long as the voltage specs are good enough? Or is it noisier than the 5 cent 1N4001 specified for D1?


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## amb

Quote:


  Originally Posted by *Syzygies* 
_I definitely am going to populate D1. Can I use a Schottky diode, as long as the voltage specs are good enough? Or is it noisier than the 5 cent 1N4001 specified for D1?_

 

Yes, you could use a schottky diode for D1, as long as it's rated at least 50V and 1A. Also make sure whatever you choose would actually fit on the pcb.

 That said, since D1 is only for reverse voltage protection and not rectification, I could only think of one reason why you would use a schottky, and that is to choose one with a lower forward voltage drop (Vf) than the ~0.8V of the 1N4001. I had done some looking a while back, and could not find a schottky offering significantly lower Vf and rated at 1A or more. Maybe I didn't look hard enough, if you find a suitable schottky then I'd like to know which one.


----------



## MisterX

Edit: pics removed

 I had a throw away Hammond 1455 T in the junk box and figured why not. 
 To echo what what was posted earlier... the square wave performance is very good from this amp and my DCoffset levels are a little higher then I usually see but they are still in the ok range.


----------



## amb

Quote:


  Originally Posted by *MisterX* 
_I had a throw away Hammond 1455 T in the junk box and figured why not._

 

Ooooh, all those Cerafines... 
	

	
	
		
		

		
		
	


	




  Quote:


 To echo what what was posted earlier... the square wave performance is very good from this amp and my DCoffset levels are a little higher then I usually see but they are still in the ok range. 
	

	
	
		
		

		
		
	


	



 

Curious. My prototype with AD8610s measure -0.1mV, +0.1mV and 0.0mV DC offset on the L, R, and G channels.


----------



## escher

on the parts list guide, C1 is listed as:

 multilayer ceramic capacitor 33pF 100V

 but the DigiKey part number given later down in the page (BC1007CT-ND) is rated only at 50V. Is it okay to use a 50V cap here or should i use a 100V? It doesn't look like digikey stocks the Vishay/BC 33pF in a 100V variety; i could of course go with another brand.

 [edit, another question]

 in the C7 caps, is there any advantage to using either size? (12.5mm or 18mm)


----------



## amb

Quote:


  Originally Posted by *escher* 
_on the parts list guide, C1 is listed as:

 multilayer ceramic capacitor 33pF 100V

 but the DigiKey part number given later down in the page (BC1007CT-ND) is rated only at 50V._

 

A 50V rated cap is fine.


----------



## amb

Quote:


  Originally Posted by *escher* 
_in the C7 caps, is there any advantage to using either size? (12.5mm or 18mm)_

 

Probably not in any sense that you could measure or hear. Use the appropriate size and number of capacitors to achieve the total target capacitance (this will depend on which brand/line of capacitor you use).


----------



## Nisbeth

Further to my last post, Nate submitted a more in-depth list of parts (panel components and crossfeed circuit). This files is now uploaded to http://www.nisbeth.dk/uffe/files/hea...rtssources.xls





 /U.


----------



## amb

Quote:


  Originally Posted by *Nisbeth* 
_Further to my last post, Nate submitted a more in-depth list of parts (panel components and crossfeed circuit). This files is now uploaded to http://www.nisbeth.dk/uffe/files/mcu...rtssources.xls_

 

Nice list, although for this amp I would not recommend using any 1/8" jacks (either for input or output). Also, I would like to see Molex KK headers and/or terminal blocks added for the main pcb (perhaps marked as optional).

 Some of the items like LEDs and jacks, etc., can be had from Mouser instead of Digi-key or Parts Express. Since most of the first section uses Mouser, it would be nice to keep as many items from the same vendor as possible.

 Since the list contains such options as a crossfeed board, perhaps a section on the PSU would be nice.


----------



## n_maher

Geez, cut a guy some slack 
	

	
	
		
		

		
		
	


	




. I'm in the process of tweaking the spreadsheet to use as many Mouser links as possible. As I stated on the revised version, the additional information comes direct from Sanaka's PIMETA spreadsheet. I'll be making it more and more MMM specific as time allows and as I get closer to placing my own order.

 Look for a new version with all optional parts having hot-links some time later this week. Also, I'll add a full parts rundown for a standard 24V STEPS (just built one so it's already done) along with an Elpac WM080.

 I'll add the MOLEX headers as well to the main body of work.

 N


----------



## jamont

Quote:


  Originally Posted by *MisterX* 
_I had a throw away Hammond 1455 T in the junk box and figured why not. 
 To echo what what was posted earlier... the square wave performance is very good from this amp and my DCoffset levels are a little higher then I usually see but they are still in the ok range. 
	

	
	
		
		

		
		
	


	


_

 

Very nice work! What opamps are you using?
  Quote:


  Originally Posted by *amb* 
_Curious. My prototype with AD8610s measure -0.1mV, +0.1mV and 0.0mV DC offset on the L, R, and G channels._

 

I am also using 3xAD8610 and have one channel noticeably higher than the other two. Although the outlier is still fine at 1.6 mV, this amp is so good that I'm going to fiddle with it a bit when I get a moment and see if I can bring it in line with the other two.


----------



## MisterX

Quote:


 Very nice work! 
 

Thank you. 
	

	
	
		
		

		
		
	


	




  Quote:


 What opamps are you using? 
 

OPA637/627 combo. 

 DC offset numbers are---->
 Left = .87mV
 Ground = .32mV
 Right = 1.9mV

 It kinda surprised me because I matched the resistors to stupid levels (.001%) but I have noticed that Q1+ runs noticeably hotter then rest so.....


----------



## jamont

Quote:


  Originally Posted by *MisterX* 
_DC offset numbers are---->
 Left = .87mV
 Ground = .32mV
 Right = 1.9mV

 It kinda surprised me because I matched the resistors to stupid levels (.001%) but I have noticed that Q1+ runs noticeably hotter then rest so....._

 

I only matched mine to < 0.1%, and I have L and G < 0.1 mV, but R = 1.6 mV. Could a slight mismatch in the output transistors account for what MisterX and I see?


----------



## morsel

amb recently pointed out that the OPA604 works with ±24V power rails. This allows for a 48V supply with 50WV capacitors, which should provide over 30Vpp output swing, making it a great choice for driving the K1000. We would like to hear your opinions on the sound of the OPA604 in M³.


----------



## Syzygies

I used inexpensive resistors on a MINT the other day, to see how it sounded for friends who wanted best bang-for-buck, and matched them on a $50 RadioShack meter to its precision. I got better DC offset than my PIMETA, using 0.1% Vishay-Dale that I tried to match, but pretty much came already matched to the precision of the meter.

 MisterX, what meter did you use, and how many resistors?

 There's a famous math problem behind resistor matching: The "Birthday" problem. With 30 people in a room there's likely to be two people with the same birthday. Buy a bag of twenty resistors, there's likely to be an amazing match among two of them. A more interesting question is what one's high/low inventory levels should be, to always find good enough matches from what's left after years of cherry-picking and restocking.


----------



## escher

Quote:


  Originally Posted by *amb* 
_Nice list, although for this amp I would not recommend using any 1/8" jacks (either for input or output)._

 

why are 1/8" jacks not recommended for this amp?


----------



## amb

Quote:


  Originally Posted by *escher* 
_why are 1/8" jacks not recommended for this amp?_

 

Because 1/8" jacks are typically compromised in quality. They are used on portable gear to save space, and space is not an issue on the M³. Also, I have not come across any 1/8" jack that is isolated, and you must use an isolated jack for the output if the front panel is metal.

 For home audio equipment, the standard is still RCA input jacks and 1/4" headphone output jack(s).


----------



## amb

Quote:


  Originally Posted by *jamont* 
_I only matched mine to < 0.1%, and I have L and G < 0.1 mV, but R = 1.6 mV. Could a slight mismatch in the output transistors account for what MisterX and I see?_

 

On my prototype I didn't even bother with matching anything. I just used arbitrary MOSFETs and RN55D resistors from my piles, so maybe it's dumb luck 
	

	
	
		
		

		
			





 .

 Anyway, try swapping the opamps between the L and R channels and see if the DC offset moves with the opamp. That might be telltale.


----------



## jamont

Quote:


  Originally Posted by *amb* 
_On my prototype I didn't even bother with matching anything. I just used arbitrary MOSFETs and RN55D resistors from my piles, so maybe it's dumb luck 
	

	
	
		
		

		
		
	


	




 .

 Anyway, try swapping the opamps between the L and R channels and see if the DC offset moves with the opamp. That might be telltale._

 

Yes, this was the obvious thing to try and it worked! I now have all offsets < 0.3 mV, and I am happy.


----------



## MisterX

I swapped the opamps amongst the channels and it got worse on the left side... said screw this and dropped in some OPA637 B grade opamps and of course the offset dropped considerably. 

 .09mV on the right. 
 . 12 mV on the left. 

 Replaced the OPOS637s with some 8610s and everything was good the first time. 
 Go figure huh? 

 FYI Gain = 8.5 but they showed no other signs of instability. 

  Quote:


 MisterX, what meter did you use, and how many resistors? 
 

Fluke 8840AF
 # of resistors depends on the value. 
 The 1 meggers and 100 ohmers were the worst 
 (it took close to 50 100 ohmers to get a good matched set at that tolerance)


----------



## amb

Quote:


  Originally Posted by *MisterX* 
_(it took close to 50 100 ohmers to get a good matched set at that tolerance)_

 

I salute your insanity. 
	

	
	
		
		

		
		
	


	



 IMHO the only ones worth matching in this amp are the gain resistors in the feedback loop, but with 1% resistors the worse you're going to do without matching is a very small fraction of a dB difference between channels, which is probably much smaller than the tolerances of any headphone.


----------



## MisterX

Quote:


 IMHO the only ones worth matching in this amp are the gain resistors in the feedback loop 
 

Agreed.... but no matter what I/we think it all comes back to the whole "can I upgrade those green looking caps" thing again.


----------



## Voodoochile

Quote:


  Originally Posted by *MisterX* 
_Agreed.... but no matter what I/we think it all comes back to the whole "can I upgrade those green looking caps" thing again. 
	

	
	
		
		

		
		
	


	


_

 

I hate that for you, man. 
	

	
	
		
		

		
		
	


	



 I do feel your pain.

 Nice looking work, guys. I'm still gathering some parts for mine, so nothing of interest to report here. I just ordered the board this morning (doh!), but have about 3/4 of the other parts on hand.


----------



## Magsy

I'm almost done now, spent about 3hrs today and got everything on bar the output transistors and electrolytics.

 I'm 200 miles from home and won't be back until Sunday, my Cerafines are probably waiting on my door mat now 
	

	
	
		
		

		
		
	


	




 Oh the agony...I guess I'll just have to stare at it for a little while longer imagining what it will sound like 
	

	
	
		
		

		
		
	


	




 Build went fine but I there is a small mistake in Amb's parts list..

 R2, R3, R4G, R6 | *8* | 1/8W 1% metal film resistor 1KΩ 

 I used 9 resistors, so either I've put one somewhere I shouldn't or Amb counted one short


----------



## amb

Quote:


  Originally Posted by *Magsy* 
_R2, R3, R4G, R6 | *8* | 1/8W 1% metal film resistor 1KΩ 

 I used 9 resistors, so either I've put one somewhere I shouldn't or Amb counted one short 
	

	
	
		
		

		
		
	


	


_

 

Thanks, yep, was a mistake and it's fixed now.


----------



## Magsy

I'm using a pot for bass boost, so should I populate rbb? I read that it should be equal to the pot, so 50k in mycase but I'm sure I read elsewhere on the site to not use rbb if you have the pot control..


----------



## amb

Quote:


  Originally Posted by *Magsy* 
_I'm using a pot for bass boost, so should I populate rbb? I read that it should be equal to the pot, so 50k in mycase but I'm sure I read elsewhere on the site to not use rbb if you have the pot control.._

 

Don't populate Rbb if you're using a bass boost pot.


----------



## Magsy

Quote:


  Originally Posted by *amb* 
_Don't populate Rbb if you're using a bass boost pot._

 

Thanks mate!


----------



## Akku

I am waiting for the board (a long way to Italy), in the meanwhile some questions (maybe silly).
 If I don't want the bassboost option I just need to bridge across sbb. Right?
 What the purpose of C2? Can I use some 1uF BG non polar caps I have laying in my drawer?
 Why polypropilene for C6? As long as they are PS bypass caps, why not cheaper polyester? (Off course I have this stuff lying in my drawer too).
 Thanks everybody.


----------



## morsel

You can use polyester film. The only caps worthy of polypropylene are Cbb and perhaps C2, although that is debatable since it doesn't really do much. C2 bypasses the variable impedence of Q2, the Vbe multiplier, but we were unable to hear or measure a difference with or without C2. Perhaps better ears and test equipment than ours will reveal a difference.


----------



## amb

Quote:


  Originally Posted by *Akku* 
_If I don't want the bassboost option I just need to bridge across sbb. Right?_

 

Yes.

  Quote:


 What the purpose of C2? Can I use some 1uF BG non polar caps I have laying in my drawer? 
 

C2 is for improving the tracking between the N and P channel output devices at higher frequencies. I suggest using film caps here rather than electrolytics.

  Quote:


 Why polypropilene for C6? As long as they are PS bypass caps, why not cheaper polyester? 
 

Polyester may not have good enough HF characteristics.


----------



## Akku

Thanks Morsel and AMB.


----------



## steinchen

M³ assembled and running fine 
	

	
	
		
		

		
			










 Panasonic FM electrolytics, Wima MKS 4.7uF film, Vishay Dale 0.1% nonmagnetic resistors, 3x ad843kn, 2.5" heatsinks, matched mosfets (dc offset 2mV / 3mV), atm 80mA bias current, going to push it to 110mA, C1=10pF, polypropylene Orange Drops for bass boost






 first thing I recognized was the easy deep black rocksolid bass 
	

	
	
		
		

		
		
	


	




 overall sound is very easy with much detail. Even with "only" 30V and ad843's the M³ is driving my K1000 very fine 
	

	
	
		
		

		
		
	


	




 (the HD600 anyway) I don't see any reason to go up to 36V or use opa604. Finally I found an amp to kick the ass of my K1000 :thumbsup

 Unfortunately I'll be on the road tomorrow all day long, so intensive tests have to wait until Sunday.

 Many thanks to Morsel and amb, you designed a great amp that really rocks


----------



## amb

Cool steinchen, those tall heat sinks make the board look like a serious power plant 
	

	
	
		
		

		
		
	


	




 .


----------



## morsel

Congrats on your amp, steinchen. 
	

	
	
		
		

		
		
	


	




 Glad M³ is driving your K1000 well.

  Quote:


 Polyester may not have good enough HF characteristics. 
 

I'm comfortable bypassing with polyester caps. They have a venerable history in the audio community for this very purpose. Having said that, if anyone finds conditions where polyester is insufficient, please let us know. In any case, using polypropylene isn't going to hurt. C2 and C8 don't have to be 1µF, .1µF is OK too, so you can use .1µF polypropylene for all the film caps except Cbb, which is better off with .22µF if you want a 20-80Hz bass boost range. So, my bottom line for C2, C6, & C8, .1-1µF polyester or polypropylene is all good, you don't have to follow our exact recommendations.


----------



## legodude

Hi

 I am going to use this mount kit. Do I need to apply thermal compound still or no? If so, where do I apply the thermal compound?

 Also, where are you guys buying your hardware for mounting the heatsink to the board?

 thanks in advance


----------



## amb

Quote:


  Originally Posted by *legodude* 
_I am going to use this mount kit. Do I need to apply thermal compound still or no? If so, where do I apply the thermal compound?_

 

Put the thermal compound on both sides of the insulator. You don't need to put a lot, just a thin film is enough. If you use too much goo, when the insulator is pressed down between the MOSFET and the heat sink, it will ooze out the side and make a mess.

  Quote:


 Also, where are you guys buying your hardware for mounting the heatsink to the board? 
 

Your local hardware store should have what you need. Either use #4 self-tapping screws, or tap the holes on the heat sinks with a #4-40 tap about 1/2" deep, and then use #4-40 machine screws.


----------



## MisterX

The OnSemi Linear and switching voltage regulator handbook has a pretty decent guide for heastsinks and "goo" and other related stuffs. 
 There is a "better" one but I can't find it. 
	

	
	
		
		

		
		
	


	





  Quote:


 Put the thermal compound on both sides of the insulator. You don't need to put a lot, just a thin film is enough. If you use too much goo, when the insulator is pressed down between the MOSFET and the heat sink, it will ooze out the side and make a mess. 
 

Nice post. 
	

	
	
		
		

		
		
	


	




 I would add that it's usually a good idea to mount the MOSFET's to the heatsinks.....screw the heatsinks down and then solder them to the board so you are not stressing the leads.


----------



## jasonhanjk

In this rightmark analyser loopback page, http://www.amb.org/audio/mmm/rmaa_mmm_v_loopback.html .

 How much watt use when this measurement in perform?


----------



## Nisbeth

Quote:


  Originally Posted by *amb* 
_ Either use #4 self-tapping screws, or tap the holes on the heat sinks with a #4-40 tap about 1/2" deep, and then use #4-40 machine screws._

 

AMB, will the board (and the heatsinks) accept M3-screws (no pun intended 
	

	
	
		
		

		
		
	


	




)


 /U.


----------



## thrice

Here's a link to the builds page of my completed M³:

http://www5.head-fi.org/forums/showt...42#post1287142


----------



## MisterX

Very nice amp Thrice.


----------



## amb

Quote:


  Originally Posted by *Nisbeth* 
_AMB, will the board (and the heatsinks) accept M3-screws (no pun intended 
	

	
	
		
		

		
		
	


	




)_

 

Yes it will.


----------



## amb

Quote:


  Originally Posted by *jasonhanjk* 
_In this rightmark analyser loopback page, http://www.amb.org/audio/mmm/rmaa_mmm_v_loopback.html .

 How much watt use when this measurement in perform?_

 

It's whatever the RMAA software does. If you're not familiar with the RMAA software, you simply press a button and it performs a series of tests automatically, analyzes the data and displays the results. I don't know specifically what output level it performs each tests in, and it's difficult for me to measure them because the test tones are complex and short in duration, but I'm sure it's nowhere near full output.


----------



## legodude

hi

 I have one more question. In case I put a lot of thermal compound and it goos out on the sides, is it going to conduct through it?


----------



## SDA

That depends on the thermal compound. Some thermal compounds are electrical insulators, others, well, aren't. Honestly, I'd say that the safest solution is just to avoid using too much thermal compound. After all, temperature-wise, less is better; the goal is to fill in the tiny cracks and gaps on each surface, not to make a sandwich. If you intend on using very little but just want to be as careful as possible, you could always look for a compound that's specified as an electrical insulator.


----------



## silvervarg

I have tried several thermal compunds on computer CPU's, and can recommend Arctic Silvers Ceramique. It is easy to work with compared to most others and it is non-conductive and has very good thermal characteristics.
 On top of this it is relatively cheap and easy to find on computer stores that sells CPU heatsinks.


----------



## jasonhanjk

Quote:


  Originally Posted by *amb* 
_It's whatever the RMAA software does. If you're not familiar with the RMAA software, you simply press a button and it performs a series of tests automatically, analyzes the data and displays the results. I don't know specifically what output level it performs each tests in, and it's difficult for me to measure them because the test tones are complex and short in duration, but I'm sure it's nowhere near full output._

 

Guess Rightmark is still in it's infancy stage... Normally 10mW to maintain a good THD reading is required...


----------



## amb

Quote:


  Originally Posted by *jasonhanjk* 
_Guess Rightmark is still in it's infancy stage... Normally 10mW to maintain a good THD reading is required... 
	

	
	
		
		

		
		
	


	


_

 

10mW is a power output figure and it varies with load, given a certain output voltage: P = V^2 / R

 I run my tests with 33 ohm dummy loads at the output of the amp, for 10mW into 33 ohms it works out to just under 0.6Vrms. On the other hand, with a 330 ohm load the amp will be making only 1mW at the same voltage, and have to output over 1.8Vrms to make 10mW. RMAA doesn't vary the gain based on load, so the 10mW figure is a bit nebulous.

 At any rate, I think the M³'s 0.001% THD result is pretty good whatever the level is 
	

	
	
		
		

		
		
	


	




 .


----------



## jasonhanjk

True. MMM is really good... 
	

	
	
		
		

		
		
	


	




 Since adjusting Rightmark volume would create more problem, there is another way of doing this. By varying the load resistor, you can get the required testing 10mW. An osciloscope is needed to measure the -1dB voltage first though.

 If it can reach 100mW, guess what. You guys should form a company and make yourself rich...


----------



## morsel

Once you start doing it for money, it is no longer fun, plus it is hard to make much money selling headphone amps.


----------



## amb

Morsel is absolute right. It's fun when it's not a job. 
	

	
	
		
		

		
		
	


	




 BTW the M³ has no trouble producing 100mW of output. In fact it could deliver a few watts of power into an 8 ohm speaker if a capable power supply is used. With efficient speakers you can get a roomful of sound.


----------



## jasonhanjk

Ummm. Yes and no.

 Let's see how MMM goes a few months later.


----------



## pabbi1

Quote:


 It's fun when it's not a job. 
 

There are other times the fun comes to a screeching halt...

 The M³ was fully assembled, and entering final check.

 STEPS putting out 32.0v - check.
 Resistance between power rails - check.
 Resistance between pins 4 & 7 (and each to O) - check.
 OPA627 inserted into G, and power on - 29.9v between 4 & 7 - check
 Voltage across R5G - 25.2v... uhhhh
 Voltage across R5G with BIASG maxed - 22.4v (or so) - FUBAR.

 Immediate power down, and check R5G - 99.9.... K. ICK.

 Simply cannot explain - no excuse. 

 OK, so all R5 and R8 were immediately replaced (carefully) with 100 ohm, but I lifted (burned off if more appropriate) a pad on R5R, one on R5G, and one on R8G-, even exercising extreme care. 

 Not surprisingly, power rails have a short. The good news is that the TP just below C5L (as well as pin 4 and Pin 7) to OL is not shorted. Same for C5R, pin 4, and pin 7 to OR. But, each is shorted on G.

 Are there any additional troubleshooting tips to determine whether the problem is with R5 or R8, or both?

 What is the workaround for the abominated pad?


----------



## amb

Seems like you're using too hot a soldering iron (and/or heating the pads for too long) to be doing damage like that. What are you using?

 Also, check carefully for solder bridges. The R5 and R8 resistors are not anywhere near signal ground so they're probably unrelated.


----------



## pabbi1

Yes, I was using the RS Solder Station on the 40w setting to uninstall...

 Could this be from a toasted component? And why just the G side? Flux has been removed, but I'll look again for solder bridges.

 Edit: No solder bridges - opinions about how to procede?


----------



## phobus

Got my lunchbox M³ finished and it sounds great. 

 Thank you to Team M³!

 Pics here: http://www6.head-fi.org/forums/showp...&postcount=378


----------



## amb

Quote:


  Originally Posted by *phobus* 
_lunchbox M³_

 

Very cute!

  Quote:


  Originally Posted by *pabbi1* 
_Could this be from a toasted component? And why just the G side? Flux has been removed, but I'll look again for solder bridges.
 Edit: No solder bridges - opinions about how to procede?_

 

When you say that there is a short from a power rail to "G", are you referring to the power rail that feeds the MOSFETs (before the capacitance multiplier) or the rail that feeds the opamps? Which rail? And where is "G" exactly?


----------



## pabbi1

G, as I called it, is the ground channel, as in RxG, QxG, CxG, QxG.

 Ok, I need to start from the beginning. When I measure between V+, and V- (on a Molex connector), I get a "1" on the 2000K scale. Immediately.

 When I measure the 4 & 7 pins to IG, I get resistance (takes a while to interpolate down).

 What should I be measuring to test the V+ V- issue? 

 Please disregard my previous spurious "guesses".


----------



## amb

Quote:


  Originally Posted by *pabbi1* 
_Ok, I need to start from the beginning. When I measure between V+, and V- (on a Molex connector), I get a "1" on the 2000K scale. Immediately._

 

Try a lower resistance scale on your meter, like 200 ohms. The measurement should read something across V+ and V- due to charging up the bank of C7 capacitors, but should slowly go to "infinite". In fact, instead of measuring across V+ to V- on the connector, measure between the N-channel and P-channel MOSFET mounting tabs (this corresponds to the drain pins of the MOSFETs). This takes D1 out of the equation. If you still get a low and constant resistance reading, then your MOSFETs are probably toast on that channel. You can also verify this by measuring resistance between the drain and source pins of each MOSFET.

 I am a little concerned because you had your BIAS pot maxed at one point. There should almost never be a need to go to max on that pot. You should always start from the minimum (fully counter-clockwize) position. Also, before you even fiddle with that pot, you need to get the BIASOP pot set properly to establish an 5mA current through the Vbe multiplier (start with the BIASOP pot set to middle). This is all spelled out step-by-step on my site.

  Quote:


 When I measure the 4 & 7 pins to IG, I get resistance (takes a while to interpolate down). 
 

You're seeing the charging effect of the C5 capacitors. With the opamps removed from sockets, this should also go to "infinity" on a low resistance scale.


----------



## primer

What size screws should I use to secure the heatsinks to the board?


----------



## MisterX

Quote:


  Originally Posted by *amb* 
_Your local hardware store should have what you need. Either use #4 self-tapping screws, or tap the holes on the heat sinks with a #4-40 tap about 1/2" deep, and then use #4-40 machine screws._

 

Nuff said?


----------



## amb

primer, seeing that you're in Australia, you would probably use metric hardware. This means 3mm self-tapping screws or M3 machine screws after tapping the heat sinks.


----------



## primer

Thanks, I have some M3 machine screws but they seems to be a bit big but maybe I bought the wrong ones. Back to the hardware store tomorrow.


----------



## amb

Quote:


  Originally Posted by *primer* 
_Thanks, I have some M3 machine screws but they seems to be a bit big but maybe I bought the wrong ones. Back to the hardware store tomorrow._

 

The heat sink holes have no threads, so the M3 machine screws would be "too big" unless you use a tap and drill to make the threads.


----------



## steinchen

metric self tapping screws are available with 2.2mm, 2.9mm, 3.5mm, ...

 3.5mm would be too big, the 2.9mm (x 9.5mm length) fitted well on my M³

 if you want to bother with tapping threads you must tap M3 threads and pick M3 machine screws (12x)


----------



## phobus

My hardware store didn't have self tapping screws that small, but did have a tap bit for my drill. The bit was only $5, and it was easy enough to drill the threads into the heatsinks.


----------



## Magsy

Quote:


  Originally Posted by *phobus* 
_My hardware store didn't have self tapping screws that small, but did have a tap bit for my drill. The bit was only $5, and it was easy enough to drill the threads into the heatsinks._

 

Just for reference I managed to cram some 3mm self tappers in my heatsinks today. They didn't go in too easily but I think that was more to do with the length (12mm)


----------



## Magsy

My cerafines have got lost in the post and today I finally run out of patience. I have a working M³ now, it has only 3x470uf Pana FC's and 7 Jamico (urgh) 100uf, all 25v
	

	
	
		
		

		
		
	


	




 Despite that it sounds pretty good!! Early days yet, with only about 4hrs of runtime but it has more depth and punch than my pimeta, its not a massive jump though.

 My trimpots had no 'clicks' which confused me some, I was turning them as per the guide waiting for a click that wasn't forthcoming 
	

	
	
		
		

		
		
	


	




 Anyway, I have it all running with 85mv/5mv of bias and 637/627's.

 I have a question though but probably a very stupid one so don't laugh!

 Amb says to measure the voltage at the opamp pins and it should be the same as the psu but less a volt or two (I have no diode). When I measure mine it reads 9.6v but my psu is putting out about 20.5v.

 Is this right? Part of me says its fine because the TLE is splitting the power, so it should be +-9-10v, I suppose I'm not sure if my meter should show the full voltage? Is my M³ healthy?


----------



## individual6891

Voltage should be fine..


----------



## amb

Quote:


  Originally Posted by *Magsy* 
_My cerafines have got lost in the post and today I finally run out of patience. I have a working M³ now, it has only 3x470uf Pana FC's and 7 Jamico (urgh) 100uf, all 25v
	

	
	
		
		

		
		
	


	


_

 

As long as you're not going to power the amp with a PSU over 24V then you're fine with 25V rail caps.

  Quote:


 My trimpots had no 'clicks' which confused me some, I was turning them as per the guide waiting for a click that wasn't forthcoming 
	

	
	
		
		

		
		
	


	



 

Depending the brand of trimpot the "click" may be more felt than heard. Even then, it may be just a subtle feel.

  Quote:


 Amb says to measure the voltage at the opamp pins and it should be the same as the psu but less a volt or two (I have no diode). When I measure mine it reads 9.6v but my psu is putting out about 20.5v. 
 

When I say measure the voltage at the opamps I refer to the voltage across pins 7 and 4 (not relative to virtual ground). If you're measuring at pins 7 and 4 relative to virtual ground then you should have 19.2V across. This gives 1.3V drop from your PSU's 20.5V which is about right.


----------



## Magsy

Quote:


  Originally Posted by *amb* 
_As long as you're not going to power the amp with a PSU over 24V then you're fine with 25V rail caps.


 Depending the brand of trimpot the "click" may be more felt than heard. Even then, it may be just a subtle feel.


 When I say measure the voltage at the opamps I refer to the voltage across pins 7 and 4 (not relative to virtual ground). If you're measuring at pins 7 and 4 relative to virtual ground then you should have 19.2V across. This gives 1.3V drop from your PSU's 20.5V which is about right._

 

I have another set of 35v Cerafines coming which will be going in! 
	

	
	
		
		

		
		
	


	




 May well of been a light bump in the travel, I was using pocket tool (little un) to twiddle them.

 Not sure what I have done with the voltage readings, I was measuring one probe in pin4 and one in pin 7 and it was reading half voltage. I've just checked and its reading 18.8v now! I was measuring without the opamps in earlier, it must of been that?

 By the way, thanks for the great product, site/guide and support, its been a pleasure start to finish


----------



## amb

Quote:


  Originally Posted by *Magsy* 
_Not sure what I have done with the voltage readings, I was measuring one probe in pin4 and one in pin 7 and it was reading half voltage. I've just checked and its reading 18.8v now! I was measuring without the opamps in earlier, it must of been that?_

 

Yeah, you have to have at least one opamp in place to do that measurement. Without any load the cap multiplier that supplies the rails won't be biased and you won't read the correct voltage.


----------



## phobus

Quote:


  Originally Posted by *Magsy* 
_Early days yet, with only about 4hrs of runtime but it has more depth and punch than my pimeta, its not a massive jump though.

 Anyway, I have it all running with 85mv/5mv of bias and 637/627's._

 

I've been running mine for 4 days now, and I have a similar setup to you. I'm running with 637bp/627bp and 108mv/5mv, and I have to say that the MMM is a BIG jump over the Pimeta for me 
	

	
	
		
		

		
		
	


	




, so much so that I gave the Pimeta to my uncle. Hope to compare with the PPA v2 soon 
	

	
	
		
		

		
		
	


	




 Anyways, I'm trying the AD843JN opamps right now, and they definately don't sound as good as the 637BPs to me. However from these forums, it seems a lot of people like the 843s better. Should I change any settings on my M3 to accomodate these opamps?


----------



## amb

Quote:


  Originally Posted by *phobus* 
_Anyways, I'm trying the AD843JN opamps right now, and they definately don't sound as good as the 637BPs to me. However from these forums, it seems a lot of people like the 843s better. Should I change any settings on my M3 to accomodate these opamps?_

 

Even though I list some optimizations for the C1 value on my site (based on opamp choice and gain), it is there for academic interest. It affects the behavioe of the amp way up in the ultrasonics and is for those who want to tinker with the amp to get the best square wave performance. I doubt that there would be any audible difference.

 I don't think there are any tweaks in this amp that would affect the fundamental sonic signature of the opamp, and it's boils down to personal preference and how it might synergize with your headphone and source combination. If you like the OPA637s better, then stick with them. At the same PSU voltage, the OPA6x7 will give you a bit more output voltage swing than the AD843. This means more headroom before clipping.


----------



## amb

Anyone else got a working M³ yet (other than myself, jamont, thrice, MisterX, phobus, steinchen and Magsy)? I'd like to see some pics and hear about your impressions.


----------



## Voodoochile

I'm covering my job and also the job of a co-worker who moved on, so I am not getting squat done that is not directly tied to the day job. {*snif*}


----------



## pabbi1

Quote:


 Anyone else got a working M³ yet ? 
 

Well, I'm still struggling... someone alert the media.

 Got the trimpots adjusted (per your setup instructions), but no sound (through some cheapie functional headphones). All the readings are dead on, and tweaked after warming up. Nothing was alarming, or unexpected.

 How can I tell if I'm getting output with the meter? 

 If it will help, I can post pics tonight. Perhaps I have some other bone headed wiring issue.

 Otherwise, I'm 85% through the second board (without the resistor value faux pas), so maybe tonight.


----------



## thrice

Quote:


  Originally Posted by *pabbi1* 
_Well, I'm still struggling... someone alert the media.

 Got the trimpots adjusted (per your setup instructions), but no sound (through some cheapie functional headphones). All the readings are dead on, and tweaked after warming up. Nothing was alarming, or unexpected.

 How can I tell if I'm getting output with the meter? 

 If it will help, I can post pics tonight. Perhaps I have some other bone headed wiring issue.

 Otherwise, I'm 85% through the second board (without the resistor value faux pas), so maybe tonight._

 

Try out some of the suggestions in this article:

http://www.tangentsoft.net/audio/trouble.html


----------



## Magsy

After buying crap caps yesterday my Cerafines arrived today! 
	

	
	
		
		

		
		
	


	



 So in true headfi fashion I made the most of my lunch hour and got them on.

 Sooo sexy.... 
	

	
	
		
		

		
		
	


	

















 All it needs now is a once over with some Isoprop and putting into a case. The heatsinks are warmer than I thought, I wouldn't fancy no vents with this setup.

 I'm really impressed by the bass boost, it seems to work nothing like bass boost you get on the average hifi. It's much more subtle and seems to be effective over a tighter range - more focused, all in all really useful.

 Will be back with real impressions once its burned in/I'm used to it


----------



## amb

Quote:


  Originally Posted by *pabbi1* 
_Got the trimpots adjusted (per your setup instructions), but no sound (through some cheapie functional headphones). All the readings are dead on, and tweaked after warming up. Nothing was alarming, or unexpected._

 

Can you list what you measured at each channel's output for DC offset? What voltage drops were measured across the R5 and R9 resistors? Also, try measuring the voltage across the collector and emitter pins of Q2 for each channel. What do you get? Do the MOSFETs get warm? What is your PSU voltage and what do you measure across pins 7 and 4 on the opamps, as well as from pin 7 and 4 to IG?

  Quote:


 How can I tell if I'm getting output with the meter? 
 

I assume you do not have the board mounted in a case yet, and the volume control pot body is not connected to ground. If all your measurements are ok (especially DC offset), then plug in a pair of headphones without any input connected. You'll hear hum as you touch the volume pot shaft (use no knob for this, or a metal knob) when the pot is turned part-way up. This will be a clue that the amp is outputting a signal that is "induced" from the input (your body). If you hear nothing, then there is probably something wrong with the wiring to your headphone jack.

 At any rate, some close-up pics of the board (top and bottom) and wiring to the jacks might be helpful for us to diagnose your problem.


----------



## pabbi1

Here are my measurements (L-R-G):

 STEPS: 32.0v

 Across R5: 0.503v - 0.503v - 0.504v
 Across R9: 80.1:79.2mv - 79.8:79.9mv - 80.0:79.0mv
 Pins4&7: 29.4v - 29.4v = 29.4v
 Pin 4 to IG: 14.7 - 14.7- 14.7
 Pin 7 to IG: 14.7 - 14.7- 14.7
 IG to O: (-.5mv) - (-.3mv) - .1mv
 Q2 7.26v - 7.25v - 7.28v

 BTW, it sounds great.

 Sorry for the drama... but, I swear all I did was solder the ground from the two Alps screws to IG. Beats me... but, bottom line success. And, this was the (self inflicted) messed up board.


















 Not sure the steel metal divider (from the bottom of an old Carver CDP) is necessary, but what the heck.

 Already (most way through the first SACD), I have had a dozen 'never heard that before' moments. And, that's with Alice in Chains... I immediately notice significantly more presence, air and detail... which is probably just the OPA637 (627 in Ground) vs the OPA2132.

 Is there an alleged 'burn in' time? 

 I'll withhold detail listening results until the weekend, or 40 hours of listening time, whichever comes first.... 
	

	
	
		
		

		
		
	


	




 And, we owe you, Ti, and in equal measure, Morsel, for bringing this to fruition. Awesome job.


----------



## amb

Pabbi1, I am glad that everything worked out ok. Your voltage measurements are indeed spot-on. Congratulations! The Sun computer chassis is definitely an interesting application.

 Allow the amp to burn-in for some time (maybe leave it on continuously for a few days). It does seem to improve the sound. Since you have a spacious enclosure you might try tweaking up the MOSFET quiescent current a bit, try 100mA - 120mA and see if you hear any difference.


----------



## phobus

Nice Sparc-M³!! I see theres room for maybe a silent cooling fan in the back ?


----------



## MisterX

Quote:


  Originally Posted by *phobus* 
_Nice Sparc-M³!! I see theres room for maybe a silent cooling fan in the back ? 
	

	
	
		
		

		
		
	


	


_

 

Been there, done that and then disabled the fan. 
 It was to noisy. 

 Well that and there was no need for it either. 
	

	
	
		
		

		
		
	


	








 Nice work pabbi1!


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## ub312g0d

I have one of those old sun cases lying around, never really thought of using it as a case though. I assume that you painted it black instead of keeping it that ugly grey. Lots of extra room though in that case. I say go for like 4" heatsinks and crank up the bias to the extreeeme.


----------



## rjkdivin

If you are using the TO-220 mounting kits to mount the MOSFETs to the heat sink, is it advised to use thermal compound also? Or is the small electrical isolator pad an efficient thermal conductor by itself?


----------



## amb

Quote:


  Originally Posted by *rjkdivin* 
_If you are using the TO-220 mounting kits to mount the MOSFETs to the heat sink, is it advised to use thermal compound also? Or is the small electrical isolator pad an efficient thermal conductor by itself?_

 

The insulator pads are good thermal conductors, but in order to work properly they must adhere completely to the surfaces of the TO-220 device and the heat sink.

 Some of these insulator pads are slightly "soft" and will conform to the small imperfections of the TO-220 device and heat sink mounting surfaces, giving good heat conductivity. These do not require the use of thermal compound. Others (like the common mica-based insulators) do require the use of heat sink compound. The compound fills the micro-gaps between the layers, assuring maximum heat transfer.

 It won't hurt to use some regardless of insulator type. Don't use too much, though. just a very thin film is enough.


----------



## morsel

Congrats on your amp, pabbi1!

 rjkdivin, I favor silicone TO-220 insulators because they don't need messy heat sink grease and don't crack like mica.


----------



## rjkdivin

Thanks AMB and Morsel....just what I needed to know, and conforms with what I was thinking. The isolators with the TO-220 kits are pretty soft and should conform nicely.

 My first M3 is coming along well. I'm waiting on some caps from Mouser that were back ordered, but should be able to start mounting as soon as I figure out what case to use.


----------



## Magsy

MrX, are you saying that two big holes in the back of the hammond is enuff to keep temps under control?


----------



## pabbi1

Quote:


  Originally Posted by *ub312g0d* 
_I have one of those old sun cases lying around, never really thought of using it as a case though. I assume that you painted it black instead of keeping it that ugly grey. Lots of extra room though in that case. I say go for like 4" heatsinks and crank up the bias to the extreeeme._

 

Well, I am going to crank the bias to about 110 (medium between AMB's suggested 100-120 range) tonight to see if there is anything to be gained, so to speak.

 As for the case, it's actually a Sun 911 (though 811 would do fine as well) external SCSI, since the SPARC has a slot for the floppy. I mainly wanted the cage to mount the STEPS vertically, and the switched IEC, vents, and metal shielding make great extras. 

 As for the color, it's actually a vinyl dye, which penetrates the vinyl/plastic, comes in every color imaginable, and works extremely well. Best of all, it was $13, including the vinyl dye. Several are on Ebay today at $25 or less.

 I did notice the tiniest bit of buzz between songs last night with the volume cranked to 12 o'clock (straight up), but I get no hint with the music. There is an isolation mat (from Tangent) between the front half of the board and the case, so I don't think anything is contacting the board from the bottom (1/2" standoffs). The RCAs are _not_ grounded to the case, as that is a glued in piece of Macassar ebony.


----------



## amb

Quote:


  Originally Posted by *pabbi1* 
_I did notice the tiniest bit of buzz between songs last night with the volume cranked to 12 o'clock (straight up), but I get no hint with the music. There is an isolation mat (from Tangent) between the front half of the board and the case, so I don't think anything is contacting the board from the bottom (1/2" standoffs). The RCAs are _not_ grounded to the case, as that is a glued in piece of Macassar ebony._

 

If you're talking about an audible noise through the headphones rather than a mechanical vibration in the case, then it's possibility a grounding issue. The case should be connected to signal ground somewhere in order for the case to act as a shield (and only at one place to avoid a ground loop). The input RCA jacks is the recommended location where the signal ground would connect to the case, because it is convenient (most people could just mount the RCA jacks directly without using insulators). In your case you could run a wire.

 Make sure your power supply is completely isolated, though. This means the V+ and V- outputs from the PSU should not be connected to the case, nor should the IEC AC power earth connection. This is "Method 1" as described in the "Wiring & ground" page on my M³ site.

 When done right the amp should be completely silent regardless of volume control setting, unless your source has noise output of its own.


----------



## pabbi1

Oops. The case/cage is grounded to the IEC, so I'll undo that, and run a wire to the RCA. The STEPS is mounted about 3/4" from the cage (on plastic offsets), as well as the base of the case, so nothing is touching metal anywhere.


----------



## morsel

Quote:


 (and only at one place to avoid a ground loop) 
 

It is more important to ground the case and volume pot housing to signal ground than worry about not grounding the case at more than one point. Audible ground loops within the case are highly unlikely given the short distance and case shielding, whereas not grounding either case or volume pot housing at all will cause serious problems. The bass boost pot housing does not have to be grounded. Just making the priority clear.


----------



## guzzler

I think I'd have to agree with Tangent on this grounding issue. It is completely reckless not to ground a metal chassis to the AC ground, if you are taking the mains input directly to it. This is the first consideration, and your design has to work around it, not the other way round. It's never happened to me that the case has gone live, but I don't want to risk it for the case of simplifying the grounding scheme a little and saving a pound on some components. The real problem is the use of virtual grounds, as they're floating and hence can't be connected directly without issue. I think in the interests of safety, Method 1 should be removed entirely from the excellent MMM documentation

 g


----------



## morsel

Guzzler: We live in the USA, with lower AC voltage and different regulations on grounding than Europe. Most stereo equipment in the USA is only 2 wire. If you want to wire AC ground to the case, fine, but we are not going to try to force everyone to do it that way. Be sure to use a ground loop breaker if you do.


----------



## pabbi1

Should the STEPS still be grounded to the IEC?


----------



## amb

To chime in on Morsel's comment, what's important in DIY when working with AC power, is to know that there are potentially hazardous voltages involved, and to make sure that all such wiring are done with great care and integrity to prevent a problem from occuring. There should not be any exposed live AC wiring within the case. This means using heat-shrink tubing and insulated connectors for all such wiring. All connections and PCBs should be mechanically secure with no chance of working loose under even severe vibrations.

 Since most commercial stereo gear do just fine with a 2-wire AC cord as Morsel states, I don't think Method 1 should be removed, because it is a valid and simple way to achieve the intended purpose. If your country of residence has special regulations about this matter, then please take that into consideration.

 The power supply and AC wiring is not technically a part of the M³ project, I defer builders to read further documentation provided by your power supply vendor and other relevant sources.


----------



## amb

Quote:


  Originally Posted by *pabbi1* 
_Should the STEPS still be grounded to the IEC?_

 

Yes. If my memory serves me, the AC mains filtering on the STEPS board needs this connection. The STEPS pcb itself has no connection between the AC earth terminal and anything else on the board other than the filter. Tangent's STEPS site seems to be under construction at the moment and I can't load the schematic diagram, so you should check this for yourself. If you're using method 1, just make sure you don't also connect AC earth to the case. If you're using method 2, then connect AC earth to the case, but use the ground breaker as I describe on my site. I think the diagrams should make it clear how to wiring everything.


----------



## pabbi1

Grounding the RCAs took out the buzz... all is dead quiet (when it should be)... and glorious the rest of the time.

 I'm breaking my vow of silence on the sound. the bass boost is a marvel, guys. As a bass player, it is criminal when worthy bass lines are mixed down / out, and the boost (even at 30%) really puts some balls back in the music. Your implementation is subtle, sweet, and tight - just like a good figured bass line.

 Current observation: Ritual de lo Habitual, Janes Addiction. Splendid.


----------



## guzzler

We have two prong equipment as well, but it's double insulated around the mains section to comply with that. You'd certainly know it when 110V hit you if it happened to come in to contact, be each to his own I suppose 
	

	
	
		
		

		
		
	


	




 btw, not a slight on the project at all, looks wonderful if I had time or money to do one... Roll on Xmas 2005 
	

	
	
		
		

		
		
	


	




 g


----------



## Magsy

For me this was a reason to keep the stuff in two boxes, I can have the 240v contained within one box which is grounded to earth and another box which can be grounded to whatever I need.


----------



## skyskraper

justy pulled the trigger on the boards and most of the rest of the parts 
	

	
	
		
		

		
		
	


	




 time to see what this baby can do


----------



## rjkdivin

For any of you building, or planning to build the TEPS to power your M3, please be aware that Tangentsoft is in the process of updating their support materials to conform to their v1.2 pcb. The Parts List, Assembly Guide, and Parts Selection Guide have been updated. The Stuffing Guide and Schematic are currently off-line, so are probably being changed also.

 One big change.....the Line Filter Choke L1 has been changed from a three pin to a 2 pin configuration and the space on the pcb is smaller. The old L1 part number will not fit on the new board (I found out the hard way).

 The photos used in the Assembly Guide are now showing the correct pcb.


----------



## rjkdivin

To AMB:

 The Welborne power supply is a dual rail unit, and it is putting out pretty near exactly 24v per rail for me. You earlier suggested that this PS might be used with the M3 by using the V- and V+ outputs and ignoring the ground. The potential accross the V- and V+ is 48v. Should I look into swapping out a couple of resistors to drop the voltage, or did I missunderstand your earlier suggestion? What is the maximum voltage you would recommend into the M3?

 This is a pretty nice PS, but takes up a bit more room than the TEPS because it has an off pcb toroid....and of course double the number of components for the dual rails.

 I haven't gotten my TEPS powered up yet because I'm waiting for the new choke (see prior post).


----------



## amb

rjkdivin, 48V from rail to rail is too high for all except the OPA604 opamp.
 When I suggested the Welborne PS1 supply I had +/-12V in mind for a total
 of 24V. See the power supply page on my M³ site for a table of
 maximum supply voltages allowed for each opamp type.

 Since all the rail capacitors are specified at 50V, 48V is the practical limit
 on how high you should go even if you find an opamp that could take more.

 You could indeed reduce the voltage of the supply by changing the values 
 of the R1, R2, R3 and R4 resistors on the Welborne PS1 board. The
PS1 documentation has info on what values to use.

 Alternatively, you could just use half of the Welborne PS1 supply (i.e., take the +24V and ground and leave the -24V unused).


----------



## rjkdivin

Thanks AMB....thats pretty much what I thought. I wish I had though of it before I soldered in the resistors.....but they should come out ok. I had already looked at the Welborne documentation and changing out 4 resistors to get to 24v between V- and V+ should be a snap. I would hate to leave half of the PS idle when the resistors are so cheap.


----------



## amb

rjkdivin, one other thing. Since the Welborne PS1 comes with a dual 22V secondary 1.5A power transformer, this means that for +/-12V output the two voltage regulators will each have to drop approximately (22V * 1.4142 - 12V) = 19V. Assuming 300mA of total quiescent current draw from the amp, then each regulator will be dissipating close to 6W. The Welborne PS1 does have fairly hefty looking heat sinks on the regulators but the heat has got to go somewhere, so you should thus plan your case ventilation accordingly.

 If the PSU heat is a real problem then you might consider substituting the power transformer with one with a lower secondary voltage. For example, a dual 15V secondary (or 30VCT) transformer will drop the power dissipation on the regulators in half.


----------



## skyskraper

ive been wondering, with a dual rail supply, how safe is it to ignore the ground and simply take the + and - connections and turn it in to a single supply? i was thinking about doing this with a +/-15v supply i have (using 7X15's) to simply have a single 30v supply. 

 would this be cool for a MMM?


----------



## amb

Quote:


  Originally Posted by *skyskraper* 
_ive been wondering, with a dual rail supply, how safe is it to ignore the ground and simply take the + and - connections and turn it in to a single supply? i was thinking about doing this with a +/-15v supply i have (using 7X15's) to simply have a single 30v supply. 

 would this be cool for a MMM?_

 

It will work just fine. In fact, in early prototyping work of the M³, before I bought myself an adjustable bench supply, I was doing just what you described, using a 7812/7912 regulator pair that I had to make a 24V supply.


----------



## skyskraper

awesome


----------



## pabbi1

Ok, I've been listening for almost a week with the MOSFETs biased to 105ma, and the sound is spectacular.. still catching details here and there.

 On to amp #2 - I'm still _very_ unsure of the AD8610 mountings, so.... would it hurt to do the initial setup with OPA627/637, THEN try the 8610s?

 The P/s is a rock solid 28v, so, if my 1st amp is any indication, that should yield about 25.6v to the opamps - still an ok margin(?), or is there something I can do (AMB previously mentioned additional diodes, but...) to increase my margin of error a bit?

 The entire exercise was to have one amp maxed for OPA (32v) and one for AD (28v). The Opa has bass boost, the AD does not. The Opa has RK27s, and the AD a stepped attenuator (which wouldn't fit with a bass boost pot). The Opa has silver wire, the AD has OFC copper. 

 I'm struggling with SOIC all around, since I cannot get a MINT (ok, actually my 2nd attempt / 2nd board) to work... but mayhaps my new (to me) EC 2002 will help... IF I can get the right temp.

 I'm at about $400 for parts for _both_ amps (total), befort the PARS case, which I probably won't use anyway (found another 911 case for $20 locally), since my P/s is 3.25" tall.


----------



## amb

Quote:


  Originally Posted by *pabbi1* 
_On to amp #2 - I'm still _very_ unsure of the AD8610 mountings, so.... would it hurt to do the initial setup with OPA627/637, THEN try the 8610s?_

 

Sure, you could do that. Changing opamps on the M³ won't affect the bias adjustments.

  Quote:


 The P/s is a rock solid 28v, so, if my 1st amp is any indication, that should yield about 25.6v to the opamps - still an ok margin(?), or is there something I can do (AMB previously mentioned additional diodes, but...) to increase my margin of error a bit? 
 

With OPA627/637s installed, measure the voltage across pins 7 and 4 of the opamp. If it's below 26V then it's safe for the AD8610s, since they are actually rated for 27.3V absolute max.

  Quote:


 I'm struggling with SOIC all around 
 

When soldering SOIC chips, use a low-wattage iron (20W is plenty, even 15W is ok, or set an adjustable iron to mid-low setting), preferably one with a fine "screwdriver" style tip. Treat the pads with a solder flux pen, and then place the chip over the pads. Secure the chip using a locking tweezer or some kind of spring clip while adjusting the position so it's aligned correctly. I use a magnifying glass desk lamp to have a better view. Apply some heat to a lead/pad and use a very small amount of solder. Do the opposite corner and then do the rest of the leads. Use heat sparingly, only enough to melt the solder and have it flow evenly. A little "wiping" action with your soldering iron tip will help even the solder out. After you're done soldering, clean off the flux with isopropyl alcohol and check connectivity with your multimeter.

 Here is a photo of a AD8610 nicely soldered onto a browndog adapter:


----------



## rjkdivin

Okay....maybe a pipe dream....or maybe even a bad idea....would appreciate any feedback!

 I've been considering mounting an M3 in a small form factor PC case like a micro-ATX or mini ITX along with a power supply, a transport, and a DAC along with a selectable input between the transport and outside source input jacks.

 This would be like a souped up, high end, semi-portable, walkman that you could move around your home without being stuck to a room with a system, or a source component.

 Of course you would want a power supply that could supply the M3, transport and DAC, so compatible voltages and amperage would be a concern. I was thinking of a dual rail regulated supply with one rail for the M3 and the other for the transport and DAC, but I have done no research on the transport or DAC requiremnts.

 That brings me to my next question....does anyone have a suggestion for sources for appropriate transports, and for either off the shelf bare DAC units or DIYs with pcbs?


----------



## amb

Quote:


  Originally Posted by *rjkdivin* 
_That brings me to my next question....does anyone have a suggestion for sources for appropriate transports, and for either off the shelf bare DAC units or DIYs with pcbs?_

 

Have a look at this thread:
http://www6.head-fi.org/forums/showthread.php?t=102583

 Use a separate PSU regulator branch for the analog and digital circuits, and keep the grounds separate too.


----------



## Jaypetermen

I am looking for a PS which will fit an aluminum enclosure that measures 6W x 8D x 2.5H (Option A form Par-Metals M3 Enclosure Group Buy.) and will provide appropriate output to power both the M3 (24VDC +) and a DAC (12VDC). The DAC may be the Scott Nixon TubeDAC.

 Any ideas?


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_I am looking for a PS which will fit an aluminum enclosure that measures 6W x 8D x 2.5H (Option A form Par-Metals M3 Enclosure Group Buy.) and will provide appropriate output to power both the M3 (24VDC +) and a DAC (12VDC). The DAC may be the Scott Nixon TubeDAC._

 

How much current draw will there be on the 12VDC circuit from the TubeDAC?


----------



## rjkdivin

Quote:


  Originally Posted by *Jaypetermen* 
_I am looking for a PS which will fit an aluminum enclosure that measures 6W x 8D x 2.5H (Option A form Par-Metals M3 Enclosure Group Buy.) and will provide appropriate output to power both the M3 (24VDC +) and a DAC (12VDC). The DAC may be the Scott Nixon TubeDAC.

 Any ideas?_

 


 The Wellborne Labs PS-1 Power Supply is a nice little dual rail unit and the torroid is mounted off pcb so you could theoretically use different voltage control resistors and a different toroid for each rail. However, it has a common ground for the two rails. AMB could better comment on the potential problems associated with that.

 Mine is working perfectly, and I have set it up for 15v. outputs at each rail, and will bypass the ground and power one M3 from both rails. In will fit easily in the 6x8x2.5 case. If you select toroids at less than 3" accross, you could squeeze two of them in.

 By the way, Avel-Lindberg (avellindberg.com) has an excellent selection of toroids. They are not sold by Mouser or Digi-Key, and Parts Express has a limited selection, but Avel will sell direct over the phone....I ordered 2 units and they were most happy to take the order.


----------



## rjkdivin

I have, as mentioned in my prior post, a Wellborne Labs PS-1 working perfectly.

 My TEPS however is another matter. It is outputting only about 7.2v, and occasionally will buid up to about 10v., then drop again. I used all of Tangents recommended parts including the LM317TNS regulator. I have double checked all of the resistor values, and orientations for the diodes and electrolytics, and have found nothing.

 It is outputting 44.4vac at TP 1 and 2 (at the transformer). It is outputting 62.8 vdc unregulated at TP 3 and 5 (at the filter capacitors). These seem to be correct, so it seems the problem is in the regulator circuitry????

 At TP 4 and 5, I get only 7.2vdc, and should be getting in the neighborhood of 24v. The VSET is a 500ohm unit and can not come anywhere near adjusting this difference. R4 is currently at 2.2kohms, and R3 is at 121ohms.

 Any ideas from any of the electrical wizzards where I might look for the problem???

 Thanks anyone!


----------



## amb

Quote:


  Originally Posted by *rjkdivin* 
_The Wellborne Labs PS-1 Power Supply is a nice little dual rail unit and the torroid is mounted off pcb so you could theoretically use different voltage control resistors and a different toroid for each rail. However, it has a common ground for the two rails. AMB could better comment on the potential problems associated with that._

 

Yup, the common ground is a problem, because if you use one rail (the positive rail) as the power for your headphone amp, then you're left with the other rail which is negative voltage. Most likely not what you want for DAC power.

 As for your STEPS problem, your description does sound like something is wrong with the regulator itself. Double check to make sure all capacitors and diodes are installed with the proper polarity and all resistor values are actually what you think they are. What effect, if any, is there when turning the Vset pot?


----------



## rjkdivin

Quote:


  Originally Posted by *amb* 
_As for your STEPS problem, your description does sound like something is wrong with the regulator itself. Double check to make sure all capacitors and diodes are installed with the proper polarity and all resistor values are actually what you think they are. What effect, if any, is there when turning the Vset pot?_

 


 Thanks AMB, for your help. 

 I have tripple checked my resistor and capacitor values, and diode and electrolytic polarities....all seem to be correct. The VSET pot does nothing when turned. I am no longer getting spikes up to the 10v range, but when I turn it on, it now goes no higher than about 6.9v. and immediately starts dropping slowly. After a minute or two it is down to 6.1v. When I turn it off, it drops slowly for about 15 sec., then faster after that.


----------



## MisterX

Sounds like C7 is backwards....

http://www6.head-fi.org/forums/showthread.php?t=73550


----------



## rjkdivin

Quote:


  Originally Posted by *MisterX* 
_Sounds like C7 is backwards...._

 

Thanks Mr. X.....That was it.....it is absolutely rock solid at 24v now. I was not aware that tantalums had polarity, so I missed that one.


----------



## Jaypetermen

Quote:


  Originally Posted by *amb* 
_How much current draw will there be on the 12VDC circuit from the TubeDAC?_

 

I do not know for sure. However, Scott’s web page lists the following options: 

 -#1 use a 12VDC wall wart or pre-regulated 12 - 15VDC supply. 

 As you noted on your site is rated at 0.33A. I also read, on another forum, that this DAC will perform better with a good PS.

 -#2 use a 9 - 12VAC transformer as now the dac has a protection diode for the DC supplies (reverse volt protection). This creates a half wave rectifier for an ac only feed. 

 -#3 a single 12V SLA Battery, you provide the battery and charger 
	

	
	
		
		

		
			





 The diode protection in circuit makes the battery use safe from accidental reversals. 

 Scott Nixon also offers the 3Xac, which is a 12VAC 3A toroidal power supply. However, I do not think that it is a kit.

 Any way, this is what sparked my interest in the TubeDAC. I believe that this is like Scott's option #2 but I do not know how to execute this with purchasing the 3Xac.

 I would like to run three enclosures; one with a M3, another with the amp's PS ((S)TEPs or WL PS-1) and a third with the DacTube. All enclosures would be Option A from the Par-metals group.

 The question that baffles me is, where is the DACs PS to go?


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_I would like to run three enclosures; one with a M3, another with the amp's PS ((S)TEPs or WL PS-1) and a third with the DacTube. All enclosures would be Option A from the Par-metals group.
 The question that baffles me is, where is the DACs PS to go?_

 

The solution is to mount two power supplies in one case. The Option A case is a bit too small for two STEPS boards, so that option is out.

 One possibility is a STEPS for the M³ amp, and then a Velleman K1823 for the Scott Nixon TubeDac. You could either use a separate power transformer for the K1823, or "share" the secondary of the onboard transformer on the STEPS. The smaller footprint of the K1823 board should allow you to mount both power supplies in the same "option A" Par Metal case. Note that you'll need to add a heat sink to each of the K1823's LM317 voltage regulators. Also you may need to replace the C4 capacitor on the K1823 with 63V voltage rating.

 Another option is to use two K1823s, one for the M³ and one for the TubeDac, either with a shared power transformer or separate transformers. Same caveat for the heat sinks and C4 capacitors.

 A third option is to use two Welborne PS1s, but I am unsure whether this would fit the Option A case, either with separate transformers or shared. I don't have a PS1 to measure, so I don't know the actual PCB dimensions (the Welborne website and doc doesn't specify this). Maybe rjkdivin could measure his PS1 board?


----------



## rjkdivin

Quote:


  Originally Posted by *amb* 
_Maybe rjkdivin could measure his PS1 board?_

 

The Welborne PS-1 is 4 13/16" Long x2 3/8" Wide x 1 1/4" Tall with a little less than 3/16" clearance allowed underneath. The capacitor banks and heatsinks are inset from the long edges about 1/16".

 The PS-1 does not have an on-board transformer. The one supplied with mine is a Avel-Lindberg that measures 2 15/16" in diameter by about 1 3/16" tall with mounting hardware. I am actually replacing it with one that is a little over 3" in diameter....when it arrives.

 Avel has a pretty good selection....better than Mouser or Digi-Key, and will sell direct by phone:

http://avellindberg.com/transformers...mers_index.htm


----------



## Jaypetermen

What do you think that shiggins did here? It looks like Scott's option #2?

 -#2 use a 9 - 12VAC transformer as now the dac has a protection diode for the DC supplies (reverse volt protection). This creates a half wave rectifier for an ac only feed. 

 In this configuration I may not need a separate PS, just one transformer to step the 110VAC down to 12VAC? 

 I may be able to find a transformer than would fit on top of the enclosure?

 The concern would be the quality of the 12VAC right?


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_What do you think that shiggins did here? It looks like Scott's option #2?_

 

Why don't you ask shiggins yourself? His post does not show any pictures or details of the power to the TubeDac. Half-wave rectification gives a fairly poor-quality DC, I don't know whether the TubeDac has onboard regulation or how it tolerates such. Anyway this is straying off-topic because now we're no longer talking about M³ stuff.


----------



## DigiPete

Can the opamps be different on the ground channel compared to the L,R (i.e. 8610 on ground and 827s on L,R)? If you can do it, is there a downside to doing so?

 Thanks
 DigiPete


----------



## amb

Quote:


  Originally Posted by *DigiPete* 
_Can the opamps be different on the ground channel compared to the L,R (i.e. 8610 on ground and 827s on L,R)? If you can do it, is there a downside to doing so?_

 

Yes, you can use a different opamp on the ground channel than the L & R channels. The only downside is that it subtly alters the symmetry between the the positive and negative side as "seen" by the headphones. Different opamps have slightly different transfer functions (i.e., non-linearities) and other characteristics. These will no longer cancel out at the transducers, as would be if the opamps were the same.

 BTW I think the AD8610 and the output MOSFETs have great synergy together. You might also try the AD8065 which IMHO is also very good. I'd use other opamps only if I want to run a higher power supply voltage than 24V.


----------



## primer

Had everything working fine and sounding brilliant yesterday but today I'm not too sure. Had it going for over an hour and it was perfect. Decided to twist all the connecting wires, turned it on .... sparks and bit of smoke and now it doesn't work. Must had some wires caught under the board ... not sure. Where do I start? I'm just a novice. Running with a external 24v regulated power supply 1) LED turns on 2) C7 caps measures 23.5v 3) No voltages across the opamps 4) No voltages across C5 caps 5) C4 neasures 23.5v

 I think sparks and smoke was between C5G, C4 and TLE area. Remember I just a novice in amps and electronics. 

 Cheers


----------



## MisterX

I would pull the tle and make sure there is not a direct short between the + and - rails before you replace it


----------



## amb

primer, sounds like you shorted out something and either Q5+, Q5- or maybe the TLE blew out. Can you be more specific in describing "no voltage at opamp"? Measure the voltage across pins 7 and 4 of each opamp, and then at each of these pins relative to IG. What do you get? Also, measure the voltage between the base and emitter pins of Q5+ and Q5-, you should get about 0.65V on each of these.


----------



## primer

Voltage across pins 7 and 4 = 0.01v on L, R and G. Pins 7 and 4 relative to IG is 0.00v on L, R and G. Can you explain the base and emitter pins of Q5+ and Q5-?


----------



## amb

Quote:


  Originally Posted by *primer* 
_Voltage across pins 7 and 4 = 0.01v on L, R and G. Pins 7 and 4 relative to IG is 0.00v on L, R and G._

 

This sounds a lot like Q5+ and Q5- both popped, but before I declare that with certainty, you should check for short circuits first. Pull the opamps from their sockets, with the power disconnected, measure the resistance between pins 7 and 4 at each socket, and then at pins 7 and 4 to IG. Set your meter to the 2K ohms scale, you should get a brief reading due to the C5 capacitors charging from the meter current, but it should then settle to an infinity ("OL") reading. If you get this then there is no short circuit.

  Quote:


 Can you explain the base and emitter pins of Q5+ and Q5-? 
 

See the pin-out diagram of the 2N3904 and 2N3906 transistors. (C = collector, B = base, E = emitter)

 What connecting wires were you "twisting" and what wires (exposed?) touched the board below?


----------



## primer

Quote:


  Originally Posted by *amb* 
_This sounds a lot like Q5+ and Q5- both popped, but before I declare that with certainty, you should check for short circuits first. Pull the opamps from their sockets, with the power disconnected, measure the resistance between pins 7 and 4 at each socket, and then at pins 7 and 4 to IG. Set your meter to the 2K ohms scale, you should get a brief reading due to the C5 capacitors charging from the meter current, but it should then settle to an infinity ("OL") reading. If you get this then there is no short circuit._

 

There is resistance between pins 7 and 4 at L, R and G sockets.

  Quote:


 What connecting wires were you "twisting" and what wires (exposed?) touched the board below? 
 

Not sure of which wires but I noticed there were exposed wires under the board.

  Quote:


 measure the voltage between the base and emitter pins of Q5+ and Q5-, you should get about 0.65V on each of these. 
 

Not sure whether I measured correctly. Base and emitter : Q5+ = around 23.5v Q5- = 0v


----------



## amb

Quote:


  Originally Posted by *primer* 
_There is resistance between pins 7 and 4 at L, R and G sockets._

 

Constant resistance? If so what are the values that you read?

  Quote:


 Not sure of which wires but I noticed there were exposed wires under the board. 
 

Well, I know you're a newbie, but I hope you have leared from this that loose and haphazard wiring is bad. All wiring should be well insulated and securely routed so none of this "accident" could happen.

  Quote:


 Not sure whether I measured correctly. Base and emitter : Q5+ = around 23.5v Q5- = 0v 
 

You've looked at the pin-out diagrams of the transistors, right? Then you should be able to identify each of the transistors' pins. Then, with your meter set to Volts scale, carefully place each of your meter probes on the base and emitter pins, respectively, and read the voltage. That's simple enough, no?

 If you actually measured correctly, and those are indeed the voltages you got, then it would appear that both transistors are blown, in different ways.

 BTW, if you want meaningful help you've got to give better and more detailed info than "not sure" this and "not sure" that...


----------



## primer

Quote:


  Originally Posted by *amb* 
_Constant resistance? If so what are the values that you read?_

 

Reading at M ohm level starts over 3m and dropping at L, R and G.

  Quote:


 Well, I know you're a newbie, but I hope you have leared from this that loose and haphazard wiring is bad. All wiring should be well insulated and securely routed so none of this "accident" could happen. 
 

I was stupid and impatient.

  Quote:


 You've looked at the pin-out diagrams of the transistors, right? Then you should be able to identify each of the transistors' pins. Then, with your meter set to Volts scale, carefully place each of your meter probes on the base and emitter pins, respectively, and read the voltage. That's simple enough, no?

 If you actually measured correctly, and those are indeed the voltages you got, then it would appear that both transistors are blown, in different ways.

 BTW, if you want meaningful help you've got to give better and more detailed info than "not sure" this and "not sure" that... 
	

	
	
		
		

		
		
	


	



 

Sorry about the "not sure" bit. What threw me was the fact that, if it's blown then I shouldn't be getting a reading. Voltage reading between the base and emitter pins with no power supply for Q5+ = 1.15v and Q5- = 0.00v


----------



## amb

Quote:


  Originally Posted by *primer* 
_Reading at M ohm level starts over 3m and dropping at L, R and G._

 

OK, that's to be expected. I did say to use your meter in the 2K ohm scale to do this measurement...

  Quote:


 Sorry about the "not sure" bit. What threw me was the fact that, if it's blown then I shouldn't be getting a reading. Voltage reading between the base and emitter pins with no power supply for Q5+ = 1.15v and Q5- = 0.00v 
 

You were measuring voltage with the power off? That's not going to do much good... you'd be measuring the residual charge in the capacitors.


----------



## primer

Thank you amb for your help and patience. Replace Q5+ and Q5- and its back working. Went through the setup phrase and after half an hour, my measurements are

 Power supply 24v

 L - R - G

 R5: 0.500v - 0.500v - 0.500v
 R9: 75.2mv - 74.9mv - 74.8mv

 Pins 4 & 7: 21.5v - 21.5v - 21.5v
 Pins 4 to IG: 14.7v - 14.7v - 14.7v

 Its ironic that I ordered an extra Q5+ and Q5-. It was the ones I had to replace. Maybe there's a moral to it after all. Thanks again for your help amb, it was much appreciated. Cheers


----------



## amb

primer, the pin 4 to IG measurement looks a bit too high. It should be half the voltage of what's between pin 7 and pin 4. What does your pin 7 to IG voltage look like?


----------



## primer

Quote:


  Originally Posted by *amb* 
_primer, the pin 4 to IG measurement looks a bit too high. It should be half the voltage of what's between pin 7 and pin 4. What does your pin 7 to IG voltage look like?_

 

Sorry my mistake, I wrote my measurements down against pabbi1 and must have copied the wrong figures across.

 L - R - G

 Pin 4 to IG: 10.7 - 10.7 - 10.7
 Pin 7 tp IG: 10.7 - 10.7 - 10.7

 Thanks for your concern.


----------



## amb

primer, ok, those numbers look great. I am glad you have it all sorted now. Check the DC offset voltage at the outputs and if they look good, then it's time for some great music.


----------



## Jaypetermen

Quote:


  Originally Posted by *amb* 
_Yes, you can use a different opamp on the ground channel than the L & R channels. The only downside is that it subtly alters the symmetry between the the positive and negative side as "seen" by the headphones. Different opamps have slightly different transfer functions (i.e., non-linearities) and other characteristics. These will no longer cancel out at the transducers, as would be if the opamps were the same.

 BTW I think the AD8610 and the output MOSFETs have great synergy together. You might also try the AD8065 which IMHO is also very good. I'd use other opamps only if I want to run a higher power supply voltage than 24V._

 

Would the AD8065 be used on all three channels like the AD8610?


----------



## thrice

Quote:


  Originally Posted by *Jaypetermen* 
_Would the AD8065 be used on all three channels like the AD8610?_

 

Yes, it would. The OPA637 and OPA228 are the only two Op amps amb has listed in his parts list that cannot be used in the ground channel.


----------



## Magsy

Mine is going in a case soon but something has just hit me. Amb is recommending to connect IG to the case but currently I don't have this option.

 My case will be all alu, the input and dc jacks are isolated but the pots and headphone jack are not (the switchcraft 6.35mm one I've designed around doesn't look insulated.)

 Is this going to be a problem? With a bit of fiddling I think I can isolate the pots, using some washers and tape


----------



## amb

Magsy, the "Wiring & ground" section of my site is pretty specific about what you should do, complete with diagrams. Are you not using _any_ of the recommended schemes? The headphone jack "ground" is the output of the ground channel. It should not come into contact with any other grounds and I don't recommend tying it to the case even if you isolate everything else from the case.

 Can you describe exactly what you're trying to do?


----------



## Magsy

Sorry I have read it but I was hoping I could do something different? Which is stupid because you are the expert and I'm not 
	

	
	
		
		

		
		
	


	




 Its not a major problem but I have spec'd my FPE panel with a thread tapped for this  jack. Its not insulated and I've only just realised there is an insulated version.

 I wanted to use this jack because its a lot smaller that the usual neutrik and had nice small threads I could tap in the panel.

 I realise this is a mistake now, I'll work around it somehow because I want to keep the flush jack look on the panel. Perhaps I can get threads tapped to match the insulated (plastic bushed) version.

 Thanks Amb


----------



## WSE819

Completed board decided to test with elpac power supply (steps under construction). Performed initial setup powered up, supply voltage drops to 3v. Checked obvious things solder brigdes component placement ect. Checked resistance V+ V- 2k range infinit, check caps climbs to infinit, pind 4 and 7 show resitance climbing to infinite. Thinking of pulling Q5s to isolate , If this fails to resolve problem thinking of pulling mosfets next. Any Ideas?


----------



## amb

WSE819, how are you measuring the voltage (3V)? Between V+ and V-? Did you set all the BIAS and BIASOP trimpots to their initial setup positions (as documented on my site) before powering-up?


----------



## WSE819

setup as per your instructions , 3v is at the power input.


----------



## amb

Quote:


  Originally Posted by *WSE819* 
_setup as per your instructions , 3v is at the power input._

 

If that's the case, it seems something is drawing too much current to cause the Elpac to "shutdown". Double check to make sure all parts are installed with proper polarity and pin-outs again. Are you using the specified BJTs, JFETs and MOSFETs? If not, what are you using and are the pin-outs compatible?

 Also, when you got the 3V, are the opamps installed in their sockets?


----------



## WSE819

All stock parts the ones I did not purchase from you came strait from your cook book, checked with and without ground opamp installed no diifeance. Led lights up and then dies as caps charge. It would seem logical to isolate power from opamps first , mosfets second, and then see if there is a problem with rails themself.


----------



## Ob3ron

What type of standoffs are people using (or will be using) to mount their MMM to a Par Metals or similar case?

 From what I understand, my options are:
  Quote:


 1) Male-Female Threaded Hex Standoffs (Digikey 4314K-ND)

 This would mean that I'd need to put threaded holes in the bottom of the case. Uses short screws to hold the board to the standoff.

 2) Non-threaded Spacers (Digikey 1454CK-ND)

 Again, I'd have to put threaded holes in the bottom of the case, only this time it'd be for the long screws going from the pcb through the spacers.

 3) Plastic Clip type Standoffs (Mouse 534-1929A)

 No threading holes... just drilling. No screws either. 
 

Option #3 seems the best to me since it sounds like the least hassle and I can't see any disadvantages... but it is my first time building anything so I'm sure I'm overlooking something 
	

	
	
		
		

		
			





.

 If I were to go with 1 or 2, how would I go about threading the holes I drill in the bottom of the case?


----------



## amb

Quote:


  Originally Posted by *WSE819* 
_All stock parts the ones I did not purchase from you came strait from your cook book, checked with and without ground opamp installed no diifeance. Led lights up and then dies as caps charge. It would seem logical to isolate power from opamps first , mosfets second, and then see if there is a problem with rails themself._

 

How much total C7 rail capacitance did you install? Maybe the initial charge-up current is too large for the Elpac.


----------



## WSE819

It would depend on how high you want raise the board ( if you are mounting your pots on the board itself). I use the standoffs to mount computer motherboards it seems I always have bunch of them laying around. Another option, I buy aluminum spacers home depot and chuck in the drill to arrive at a custom hight and cut the screw to corispond.


----------



## WSE819

I used 9 330uf caps,I could back a few out but I don't think that is top much.


----------



## amb

Quote:


  Originally Posted by *Ob3ron* 
_What type of standoffs are people using (or will be using) to mount their MMM to a Par Metals or similar case?
 ..._

 

Don't bother threading the holes in the case. The case bottom is not thick enough to make any threading effective. Just drill standard round holes and:

 1. Use spacers with machine screws and hex nuts, or,
 2. Use female-female threaded standoffs and short machine screws on both ends.

 Plastic clip-type standoffs are usually too flimsy, might pop-off or break over time.


----------



## amb

Quote:


  Originally Posted by *WSE819* 
_I used 9 330uf caps,I could back a few out but I don't think that is top much._

 

You'd be surprised at how much inrush current 3000uF can generate...

 One other thing to check, are your BIAS trimpots installed the right way in? If not, fully-counterclockwise rotation would mean _maximum_ bias on the MOSFETs.


----------



## WSE819

Well I was using elpac in PPA with 2000uf , I will try backing off a few caps. Trim pots are installed correctly. I could power it off of steps from PPA but I would prefer to make sure there is not problem first.


----------



## rjkdivin

I have one of my M3s up and running.....very cool! Need to make some casing decisions now.

 A question however.....during initial setup I am reading only 15.0vdc across pins 4 and 7 of the opamps instead of the approx. 22vdc I should have there (my STEPS is putting out exactly 24vdc). I am able to adjust to .5vdc across the R5s, reading between .05 and 1.5mv dc between Is and Os, and I can easily adjust to 80mv dc across the R9s. The ac between Is and Os is running at .14mv instead of .10mv.

 Is the low voltage at 4-7 OPAMPs a problem?


----------



## amb

Quote:


  Originally Posted by *rjkdivin* 
_A question however.....during initial setup I am reading only 15.0vdc across pins 4 and 7 of the opamps instead of the approx. 22vdc I should have there (my STEPS is putting out exactly 24vdc). I am able to adjust to .5vdc across the R5s, reading between .05 and 1.5mv dc between Is and Os, and I can easily adjust to 80mv dc across the R9s. The ac between Is and Os is running at .14mv instead of .10mv.

 Is the low voltage at 4-7 OPAMPs a problem?_

 

There should be about 0.8V drop on D1, and about 2.4V drop across Q5+ and Q5-. With a 24V input you should still have ~20.8V. So, yeah, 15V is definitely low. Are all three opamps installed when you made this measurement? If not, then check it again with all three opamps in place. If it's still low, check the voltage between the collector and emitter pins of the Q5+ and Q5- transistors to see what they are.


----------



## rjkdivin

Quote:


  Originally Posted by *amb* 
_There should be about 0.8V drop on D1, and about 2.4V drop across Q5+ and Q5-. With a 24V input you should still have ~20.8V. So, yeah, 15V is definitely low. Are all three opamps installed when you made this measurement? If not, then check it again with all three opamps in place. If it's still low, check the voltage between the collector and emitter pins of the Q5+ and Q5- transistors to see what they are._

 


 With all the OPAMPS out, the resistance across the V+ and V- rails is 41Mohm, and the resistance across pins 4-7 on all three opamp sockets is 11.3Kohm. With the ground opamp in, and with all three opamps in and powered up, the voltage at pins 4-7 of all three opamps is 15.0vdc. The voltage across Q5+ and Q5- is .788vdc.


----------



## amb

Quote:


  Originally Posted by *rjkdivin* 
_With all the OPAMPS out, the resistance across the V+ and V- rails is 41Mohm_

 

The 41M ohm reading is not real meaningful except to indicate that there is no short circuit. You're essentially reading whatever small residual charge there is in the C7 capacitors interacting with your meter.

  Quote:


 the resistance across pins 4-7 on all three opamp sockets is 11.3Kohm. 
 

This is a bit interesting. Does it measure 11.3K ohm both ways (i.e., does it read the same if you reverse the meter leads)? The only resistance shunted across the opamp supply rails is the TLE2426's internal resistor divider, although the 11.3K ohm seem too low to be from that. Are all your C5+ and C5- capacitors installed in the proper polarity? Maybe one or more of these are backwards.

  Quote:


 With the ground opamp in, and with all three opamps in and powered up, the voltage at pins 4-7 of all three opamps is 15.0vdc. The voltage across Q5+ and Q5- is .788vdc. 
 

0.788V is in fact about right for the drop across each of the Q5s, but then if you're only measuring 15VDC across the opamp rails, then the MOSFET rails must be at 15V + (0.788V * 2) = ~16.6V. Add the 0.8V drop across D1 and the voltage across V+ and V- should be at most ~17.4V, far short of the 24V. Something is not adding up... Check the output voltage of the STEPS again while everything is powered up and connected.

 Also, what do you get if you measure the voltage across the drain leads of the N and P channel MOSFET? You could simply put the test probe on the metal tabs of each pair of the MOSFETs for this measurement.


----------



## rjkdivin

Quote:


  Originally Posted by *amb* 
_The 41M ohm reading is not real meaningful except to indicate that there is no short circuit. You're essentially reading whatever small residual charge there is in the C7 capacitors interacting with your meter.


 This is a bit interesting. Does it measure 11.3K ohm both ways (i.e., does it read the same if you reverse the meter leads)? The only resistance shunted across the opamp supply rails is the TLE2426's internal resistor divider, although the 11.3K ohm seem too low to be from that. Are all your C5+ and C5- capacitors installed in the proper polarity? Maybe one or more of these are backwards.


 0.788V is in fact about right for the drop across each of the Q5s, but then if you're only measuring 15VDC across the opamp rails, then the MOSFET rails must be at 15V + (0.788V * 2) = ~16.6V. Add the 0.8V drop across D1 and the voltage across V+ and V- should be at most ~17.4V, far short of the 24V. Something is not adding up... Check the output voltage of the STEPS again while everything is powered up and connected.

 Also, what do you get if you measure the voltage across the drain leads of the N and P channel MOSFET? You could simply put the test probe on the metal tabs of each pair of the MOSFETs for this measurement._

 

Okay, now my novice electrical skills are showing through (hey I'm a structural engineer 
	

	
	
		
		

		
			





 ). I think I solved the mystery....I believe I was measuring between pins 4 and 6 on the opamps instead of pins 4 and 7....just not counting them correctly. When I measure the correct pins, I get 21.7vdc on all three....all is well.

 But to answer your other questions......the 11.3kohm measurement on the opamp sockets was the same regardless of lead orientation....but of course it was apparently pins 4-6 instead of 4-7. All C5+ and C5- orientations are correct. Voltage on the MOSFET rails is 23.27vdc. Output, under load from the STEPS is 24.1vdc currently (no pun).

 Sorry AMB to have wasted your time!


----------



## amb

rjkdivin, cool, I'm glad it's just a false alarm rather than an actual problem. All is well, then. Time to listen to some tunes!


----------



## pabbi1

I have posted my long threatened review of the m³ here.

 Feel free to dogpile, embellish or counterpost as you see fit. I think the broader amp community needs some feedback on what Ti (amb) and Morsel have done. I for one, am digging the heck outta my OPA637 amp.

 al


----------



## morsel

Thanks for your kind and gracious words. Glad you are enjoying your amp. Feel free to threaten us anytime.


----------



## amb

Hi pabbi1, that's a great review. It makes all the work we did seem worthwhile 
	

	
	
		
		

		
		
	


	




 .


----------



## Akku

A question 'bout part selection.
 Is it important that the bass boost pot has an overall impedence of 50K?
 I understand it is used just as a variable resitor so the resistence "seen" from the input circuit is variable too anyway.
 Can I go for a cheaper pot? I don't plan to use the bass boost very much and I plan to put a switch to defeat it.
 P.S.
 For the volume I ordered a 10K ladder att.
 P.P.S.
 Sorry for my english. I hope I made my questions clear


----------



## Magsy

I recently tried some AD843's and they are quite something. They may ultimately have a little less resolving power than the 637 but they make virtually any music listenable.

 I've been a little displeased that since building the M³ a lot more music sounded rough or overly harsh at the top. The AD843's have really cured that, bought some more bass and done something (good I think) to the soundstage, I can't put my finger on it exactly but its more spacious for sure. I would still like a little more vocal presence but thay maybe my cans or source, I'm opamp rolling in the 0404 to try and cure it...

 There was one problem I had with them though, they need voltage! I had clipping quite easily at 23v, maybe I'm deaf as I was well past 12 o clock but it wasn't there with the 637's (or it was masked better)

 I moved up to 28-29v and that has fixed it, no more clipping 
	

	
	
		
		

		
		
	


	




 Well worth a shot if you feel like a fiddle.

 Also I've tried 80-140ma of bias and I cannot really hear a difference (just curious). Heat production goes up quickly though, on 140ma and 28v I couldn't touch the sinks for more than 15secs.


----------



## pabbi1

At 32v, with the 637s, I don't think there was any noticeable difference between 80ma of bias and 105ma.


----------



## morsel

Akku: The value of the bass boost pot should be in harmony with the rest of the bass boost components. 50K provides 0 to 15dB of bass boost with the default component values. Use the bass boost calculator at one of the M³ sites to play around with those values. A cheaper pot should be OK. There is no need for a bass boost defeat switch when using a pot as it is self-defeating at 0 Ohms.


----------



## amb

Quote:


  Originally Posted by *Akku* 
_(bass boost)
 Can I go for a cheaper pot?_

 

You should use one that has good tracking between channels so that you won't have problems with uneven boost.


----------



## Akku

Thank you AMB and Morsel. I am looking forward to listen to your work (still collecting parts)


----------



## WSE819

Well I guess if I take credit for my success its only fare I live up to my screw ups. I got stuck on onother project this weekend, but late last night (2am) I had an epiphany, I had checked all components at least 2-3 times but never checked mosfets.Sure enough droped a mirror in and I had switched inner pair. Resoldered them in correctly everthing checked out fine , peformed initial setup no more than .5 millavolt offset. Pluged in a set of headphones an enjoyed some music. Good thing I am at work today and can sleep (hope our network on the west coast doesn't go down). Thanks for your help, Once cased I will do a comparison with my PPA w Phil's dyno buffers and M3 and keep the winner. My first impressions are the percussion is much more dynamic , I was concerned bass boost may color sound but it is much more subtle. Thanks for a great project, I am up to 5 headphone amps I am begining to give them rabbit names.


----------



## amb

Quote:


  Originally Posted by *WSE819* 
_Sure enough droped a mirror in and I had switched inner pair. Resoldered them in correctly everthing checked out fine_

 

I am sure you won't be the only one with this mistake, the markings on the MOSFETs are hard to read.

  Quote:


 Once cased I will do a comparison with my PPA w Phil's dyno buffers and M3. 
 

That should be an interesting comparo. 
	

	
	
		
		

		
		
	


	




  Quote:


 I am up to 5 headphone amps I am begining to give them rabbit names. 
 

LOL


----------



## Super-Gonzo

In the section entitled "Notes about R3 and R4" on AMB's mmm site: 
http://www.amb.org/audio/mmm/parts.html 

 AMB mentions that the bass boost pot can be used as a variable gain control. Would it be possible to drop the volume pot altogether, and just use variable gain to control the volume of this amp? 

 See PS Audio's variable gain amps as an example:
http://www.psaudio.com/products/gcc_...amplifiers.asp

 If technically viable, wouldn't this result in better SNR performance, throughout the volume range?


----------



## amb

Super-Gonzo, the variable-gain method as described on my site does not allow you to completely mute the audio. Even if you set R4 = 0 (which I do not recommend, because many opamps don't work well without _some_ resistance in the feedback loop) the minimum setting will still give you a gain of 1. For many headphones and sources, that is actually fairly loud without a volume control at the input.

 As for S/N ratio, the noise floor of the M³ is so low, it shouldn't be an issue at all.


----------



## morsel

A volume control spans from maximum gain to zero volume. A gain control spans from maximum gain to unity gain. Most of the range of a volume control is below unity gain, so a gain control is no substitute.


----------



## Super-Gonzo

Quote:


  Originally Posted by *morsel* 
_A volume control spans from maximum gain to zero volume. A gain control spans from maximum gain to unity gain. Most of the range of a volume control is below unity gain, so a gain control is no substitute._

 

This being the case, what is it exactly that psAudio is doing with their "Gain control" amplifiers?


----------



## Super-Gonzo

Quote:


  Originally Posted by *amb* 
_Super-Gonzo, the variable-gain method as described on my site does not allow you to completely mute the audio..._

 

AMB, given a variable gain with a wide range, say 2-17 as mentioned on your site, what capacity caps would you reccomend for C1L and C1R (given the default ad8610 opamp)?


----------



## z2trillion

Quote:


  Originally Posted by *Super-Gonzo* 
_This being the case, what is it exactly that psAudio is doing with their "Gain control" amplifiers?_

 

Might they be using the opamp in an inverting mode, this would allow them to acheive below unity gains. Just a guess.


----------



## amb

Quote:


  Originally Posted by *Super-Gonzo* 
_AMB, given a variable gain with a wide range, say 2-17 as mentioned on your site, what capacity caps would you reccomend for C1L and C1R (given the default ad8610 opamp)?_

 

You can use the default of 33pF, or to be extra conservative, go to 47pF. The latter will ensure that the square wave response to be ring-free, at the expense of slightly reduced bandwidth (but will still be far beyond the audio spectrum).

  Quote:


 This being the case, what is it exactly that psAudio is doing with their "Gain control" amplifiers? 
 

Without seeing a schematic diagram I don't know. Their marketing blurb on the "Gain Cell" is pure hogwash, because there is no way to program the gain of an amplifier without varying some sort of resistance.


----------



## Super-Gonzo

Thanks for the advice!


----------



## skyskraper

gotten most of my M³ done. a minor pita was the fact that i could only get 3w resistors locally (didnt want to risk 1w), theyre bigger then the board gives space for and the ceramic caps i got were a bit bigger then the board has space for. a minor annoyance forsaking only neatness 
	

	
	
		
		

		
			





 you can see here 

 but here's where my M³ is up to atm:




 just waiting on some self tapping screws, panduit crimper, and pcb jumpers, all to be brought home by housemate from work, before i get stuck in to setting the thing up


----------



## morsel

Don't use electrolytic caps instead of metallized film for C2 & C8. 
	

	
	
		
		

		
		
	


	




 Why not mail order the correct parts instead? At least use the same yellow films as C6.


----------



## individual6891

Would 1W be ok in that position morsel?


----------



## morsel

P = IV = I²R = V²/R

 for R=1, P = I² = V²

 That makes it easy to calculate power dissipated by the output resistor.

 You can get away with 1W output resistors if you are using high impedance or high efficiency headphones, but I would not want to limit my amp that way.

 edit: 1W is OK for most headphones, but it is nice to have some headroom. To keep the resistor at a reasonable temperature it should be running at no more than 1/2 rated power.


----------



## skyskraper

morsel: theyre bipolars and theyre temporary until the proper caps arrive in a week or so 
	

	
	
		
		

		
		
	


	




 for 20c each its no skin off my noce


----------



## MisterX

New case plus a condor Power-One PSU. 
 Needless to say the hammond case (with the fan) went right in the trash.


----------



## phobus

WOW!!! More pics!!


----------



## pabbi1

Nice... where did you get the case?


----------



## MisterX

lol.... That case was a adventure to say the least. 
 It came from Ebay. 
 It was like $50 and shipping from Thailand was also $50. 
	

	
	
		
		

		
		
	


	



 (the same case retails for like $170 here in the US)
 But there was a major catch.
 It was 16" long when I got it so I busted out the Dremel and cut the top in half. 
	

	
	
		
		

		
		
	


	









 I think the results were worth the effort.


----------



## amb

MisterX, very nice!


----------



## wistily

Sorry if this has already been answered, but what would be an appropriate case (with or without psu) for the M3 that could be bought in Europe (par metal don't even answer my mails 
	

	
	
		
		

		
			





 ) ?


----------



## Magsy

Hammond have one, its listed in amb's M³ webpage.

 I bought direct from Hammond UK - £14


----------



## rjkdivin

You might also try Lansing Instrument Corp. It is in New York, and I don't know if they ship to Europe, but they will sell direct....there is a faxable order form available on their web site: 

http://www.lansing-enclosures.com/index.html

 Their Gray Box line is pretty nice with side vent slots and your choice of Black or Silver anodized. The B2H12-V02 will fit the M3 with a power supply, while the B2H08-V02 will fit the M3 alone.


----------



## n_maher

It's all happening...






 Should start testing with a power supply tonight. Had no web access last night so I couldn't double check anything that I was doing :nervous:.


----------



## skyskraper

hehehe im just waiting for the panduit crimp gun so i can set mine up and start listening. its the last 5% that takes 95% of the time ;D


----------



## Jaypetermen

Quote:


  Originally Posted by *Magsy* 
_Its not a major problem but I have spec'd my FPE panel with a thread tapped for this  jack. Its not insulated and I've only just realised there is an insulated version.:_

 

I am also trying to keep the front panel clean. Currently, here is my alternative. However, I am not sure that it is appropriate either?

 Did you find a suitable insulated jack, which can to threaded into the front panel?


----------



## wistily

Magsy and rjkdivin, thanks for the case's advices.


----------



## individual6891

Wow an MMM ... MrX M³ Masterpiece






 Do you have the link to the ebay seller / another on of those cases? Sure looks spliffy


----------



## Magsy

I've been spending most of my time finalising the panel, I thought I'd come back to finding a jack later (which is going to be a mistake!)

 I couldn't find anything off hand, I already have those neutrik jacks though. The nut is way to big for the look I want, the thread is big and plastic too, I'm not sure a 4mm panel will hold it nicely without the front nut?

 I'll have a look when I get home...

PDF 90kb

 My panel is looking like this at the moment, almost done. Had to move the pot holes inward which I didn't like but they won't fit the case other wise. I know the 'h' in headphone should be uppercase, its on my list.. 

 Sorry its a PDF but it looks terrible as a raster (jpg etc)


----------



## n_maher

Magsy,

 Mind if I ask what you're using for a power switch? It looks HUGE!

 Nate


----------



## Jaypetermen

Outstanding front panel Magsy.


----------



## Magsy

Thanks!

 Its a 20mm hole for this 





 I have mock tested most of the panel but not the switch yet (printed on acetate/transparency - works well!)
 I have a 20mm here on a PSU and it looks ok...

 I REALLY want to use one of these:









 They are piezo activated momentary switches, pricey though and I don't think I can be bothered to build another circuit and psu just to make my fancy switch work


----------



## individual6891

Quote:


  Originally Posted by *Magsy* 
_Thanks!

 Its a 20mm hole for this 





 I have mock tested most of the panel but not the switch yet (printed on acetate/transparency - works well!)
 I have a 20mm here on a PSU and it looks ok...

 I REALLY want to use one of these:









 They are piezo activated momentary switches, pricey though and I don't think I can be bothered to build another circuit and psu just to make my fancy switch work 
	

	
	
		
		

		
		
	


	


_

 


 The components for the M3 minus opamps costs the same as that switch ~£40 from RS 
	

	
	
		
		

		
		
	


	




 Nice panel - what case?


----------



## MisterX

Quote:


 Do you have the link to the ebay seller / another on of those cases? 
 

http://search.ebay.com/_W0QQfgtpZ1QQ...ssZpatinthouch


----------



## skyskraper

here is my idea for a front panel. its just so hard to decide on the colous


----------



## MisterX

Quote:


  Originally Posted by *skyskraper* 
_here is my idea for a front panel. its just so hard to decide on the colous 
	

	
	
		
		

		
		
	


	


_

 

Blew with black graphics.


----------



## Magsy

Quote:


  Originally Posted by *individual6891* 
_The components for the M3 minus opamps costs the same as that switch ~£40 from RS 
	

	
	
		
		

		
		
	


	




 Nice panel - what case?_

 

Indeed!
	

	
	
		
		

		
		
	


	




 I really want that switch but they don't come in black and I cannot justify the cost, maybe if it was a more expensive amp!
 That said the panels, like yours are hitting 40 euros each which is rather a large chunk of the total cost!

 Its going to be the largest Hammond in black, the top lid is hopefully going to be waterjet cut with the large M³ logo to let the heat out. I have not got a price for that yet - I wonder if FPE can make a cut from a hpgl?

 Colour is hard to choose, I should of gone silver (because the edges of the panel) but I already had the case in black


----------



## skyskraper

ok now we're working 
	

	
	
		
		

		
		
	


	




 sounding good so far. will leave it to settle in for an hour or two and then listen properly 
	

	
	
		
		

		
		
	


	




 currently running it at the stock amb reccomended settings with a 29v supply coming in, opa627's, and the rest u can sort of see from my pic. awaiting tread boards and enclosure for final testing and assembly.


 notes:
 setup really easy with amb's site. 
 this is a warm sucker, u guys werent kidding 
	

	
	
		
		

		
		
	


	



 love the dual outputs. 
 my current gain of 7.5 doesnt seem to be enuff for my akg's and source, up to 11 we go.
 love the two input positions each with multiple options, will prob use them to daisy chain my source back out to a mixer/input/speakers/whatever. 
 havent used bass boost yet, but will experiment with it once ive tested the amp properly without it. 

 happy so far, great work morsel and amb


----------



## skyskraper

question about output impedance loading. not so much for using high or low z cans, but using two at the same time. 

 i have a 55ohm pair and 64 ohm pair that are my two primary cans that i have hooked up all the time. by ohms law connecting both in parallel means the amp sees a 20ohm load. by my calculations, putting 120ohm resistors on both outputs the amp will see a combined loard of around 59 ohms. 

 will the amp enjoy driving a load of 59 ohms moreso then 20 ohms to the point that it will be audible? or is it pointless messing about with my amp that wont yield any real change?


----------



## amb

The M³ has no problem driving 20 ohm loads. In fact, it could drive even lower impedances with ease (such as speakers), as long as the PSU is capable of supplying the needed current. The robust output stage is one of the hallmarks of this amp, so you don't need to worry about it.

 The only issue with two dissimilar headphones in parallel is that one would likely to play louder than the other at a given volume control setting. Since your two cans are not _too_ far off in impedance, and assuming that they are comparable in efficiency, then this may not be a problem either.


----------



## skyskraper

excellent. i didnt think id notice a real world difference in performance. the volume thing is no problem really either


----------



## n_maher

Another successful M³ build burning in now...






 Big thanks to amb and morsel, it sounds fantastic right out of the gate. Now if that case would just show up...

 Nate


----------



## rjkdivin

Quick question regarding minimum recommended wire guage for connecting the Vol and Bass Boost pots to the PCB. One of my M3 builds requires this option due to case configuration.


----------



## MisterX

22 Guage is fine.


----------



## wistily

Newb question: C6 in 0.1uF/63 V is out of stock at digikey.
 Can i take a 0.1uF/160 V (ref BC2091-ND) instead ?
 What is lead spacing ?


----------



## amb

Quote:


  Originally Posted by *wistily* 
_Newb question: C6 in 0.1uF/63 V is out of stock at digikey.
 Can i take a 0.1uF/160 V (ref BC2091-ND) instead ?
 What is lead spacing ?_

 

Lead spacing is the distance between the two leads. The holes on the board for C6 are designed for 0.200" (5mm) lead spacing. The BC2091-ND cap has 10mm lead spacing, so it won't fit. There is nothing sacred about the 0.1uF capacitance, though. For example, you could use 0.11uF/63V with 5mm LS (Digikey BC2055-ND) and it would work just as well.


----------



## skyskraper

with an ambient room temperature of 23c aka 73.5f my mosfets have settled in to a temperature of 45-48c aka 113-118f.

 this is out in the open with no enclosure, with 80ma thru the mosfets and 5ma thru the jfets. 

 does this sound about right?

 nb: i took the readings with my dmm's temp probe. not the most accurate but still gives a fairly good indication of the ballpark.


----------



## wistily

Ok, thanks AMB.
 Now, for the choice of the led, and rled.
 I'm a little confused 
	

	
	
		
		

		
		
	


	



 On the online led resistor calculator:
 Voltage supply is 24V ?
 Where can i find led current ? It's not written in digikey's description.
 And for the calc v²/R, what means voltage dropped ? Is it (Voltage supply)-(led forward voltage) ?


----------



## amb

Quote:


  Originally Posted by *skyskraper* 
_with an ambient room temperature of 23c aka 73.5f my mosfets have settled in to a temperature of 45-48c aka 113-118f._

 

Yes, that's ~25C heat rise, which is no big deal. It will heat up more when cased up, but the MOSFETs (due to the negative temp coefficient) will self-reduce their currents. This is why you could actually dial up a bit more than 80mA when it's out in the open, so that it would settle to 80mA when closed up in the case.


----------



## amb

Quote:


  Originally Posted by *wistily* 
_On the online led resistor calculator:
 Voltage supply is 24V ?_

 

Yes, or whatever you select as your PSU's output voltage. See my M³ web site's "power supply" section.
  Quote:


 Where can i find led current ? It's not written in digikey's description. 
 

This is typically in the LED's datasheet. There is actually a fairly wide leeway with this, most LEDs will operate over anywhere from 1mA to 5mA. Some will be brighter than others (the more current, the brighter it gets).

  Quote:


 And for the calc v²/R, what means voltage dropped ? Is it (Voltage supply)-(led forward voltage) ? 
 

Yes.

 The default 10K ohm resistor value works well enough with a wide range of LEDs that you could just use that to start with. With a 24V supply and assuming a 2V LED forward voltage, it gives you 2.2mA of LED current. Only if it's too bright or too dim, then you could make an adjustment to the resistor value.


----------



## skyskraper

excellent, just wanted to check im on the money 
	

	
	
		
		

		
			





 if using the 2" heatsinks, what would be the reccomended current for the mosfets to start off with? im assuming a 25% increase would be a good but conservative figure.


----------



## amb

Quote:


  Originally Posted by *skyskraper* 
_if using the 2" heatsinks, what would be the reccomended current for the mosfets to start off with? im assuming a 25% increase would be a good but conservative figure._

 

The quality of case ventilation would be an important factor when you want to dial up more quiescent current than the 80mA default. This is a variable that's difficult to estimate and is best determined via experimentation. 2" heat sinks has more mass to dissipate the heat from the MOSFETs, but that heat must escape the case somehow. The MOSFETs are quite rugged and could operate at high temps, but if the inside of the case gets too hot, the other parts (opamps, resistors, caps, etc.) may begin to de-rate and not perform at their best.


----------



## Gumpy

Can someone tell me what the power output of the M3 amplifier is. I'd like to use a circuit similar to this to power my 95 db/watt speakers. I've been using a 3.5 watt 2A3 SET amp to power these speakers for the last 3 years.

 Also, can someone tell me why the M3 amp has the 1 ohm resistor (R9) on the source pin of the mosfets and this circuit does not:

http://www.redcircuits.com/Page2.htm


----------



## morsel

M³ should drive 8 Ohm speakers at about 4W without requiring additional heat sinking or studlier source resistors. The 1 Ohm source resistors help balance the complementary output and provide a convenient way to measure output bias current.


----------



## amb

Quote:


  Originally Posted by *Gumpy* 
_Can someone tell me what the power output of the M3 amplifier is. I'd like to use a circuit similar to this to power my 95 db/watt speakers. I've been using a 3.5 watt 2A3 SET amp to power these speakers for the last 3 years._

 

The maximum power output is directly related to the PSU voltage and current capability. For primarily speaker use, I recommend using a 36V power supply rated at 3A, and opamps that could handle the voltage (see the power supply page at my M³ web site). You should also increase the total C7 rail capacitance to 6000uF and upgrade D1 to a 1N5401. With this configuration you should have a very healthy 6W per channel (into 8 ohms) power amplifier.

 Right now I am listening to music via an M³ amp driving a pair of bookshelf speakers in my bedroom. It's quite impressive what this little "headphone amp" could do!

  Quote:


 Also, can someone tell me why the M3 amp has the 1 ohm resistor (R9) on the source pin of the mosfets and this circuit does not:
http://www.redcircuits.com/Page2.htm 
 

As morsel stated, the source resistors provide better balance between the N and P channel MOSFETs, they also improve thermal stability.


----------



## SHLim

Quote:


  Originally Posted by *amb* 
_The maximum power output is directly related to the PSU voltage and current capability. For primarily speaker use, I recommend using a 36V power supply rated at 3A, and opamps that could handle the voltage (see the power supply page at my M³ web site). You should also increase the total C7 rail capacitance to 6000uF and upgrade D1 to a 1N5401. With this configuration you should have a very healthy 6W per channel (into 8 ohms) power amplifier.
_

 

Hi AMB,

 Will be good if this info can be added to your M³ tweaks page.


----------



## Gumpy

Actually for about a month I've been using a gainclone to drive those 95 db/watt speakers. I've been powering that gainclone with 6 12V sealed lead acid batteries which gives me +-36V. 

 I have some OPA2604's but I also have some OPA445's stashed away. They're supposed to accept -+45v.

 Thanks to everyone for the help.


----------



## amb

Quote:


  Originally Posted by *SHLim* 
_Will be good if this info can be added to your M³ tweaks page._

 

OK, will do.


----------



## andante

I am currently in considering building an M3 amp.

 I haven't found much discussion for opamps for use in M3. According to Tangent's website, his favourites seem to be either OPA627/637 or AD843. He thinks that AD8610 can sound a bit harsh.

 Is there a reason that AD8610 is the default opamp, or would other mentioned opamps be better alternatives?

 I currently have Chaintech AV710 as a source and AKG 240M for headphones, but I plan on probably upgrading to HD580/600 and maybe getting a under-$100 external DAC. I mostly listen to jazz/classical/acoustic/vocal music.

 Thanks.


----------



## amb

Quote:


  Originally Posted by *andante* 
_I haven't found much discussion for opamps for use in M3. According to Tangent's website, his favourites seem to be either OPA627/637 or AD843. He thinks that AD8610 can sound a bit harsh.

 Is there a reason that AD8610 is the default opamp, or would other mentioned opamps be better alternatives?_

 

Opamps choice is largely a personal preference kind of thing. The difference amongst them sonically really isn't as big as most people on these forums describe them to be. There are some differences for sure, but very subtle. Many people have preconceived notions of what certain opamps are supposed to sound like based on what they read, and psychologically they reinforce this upon themselves when they do comparisons. However, I find that under blind test conditions much of this difference evaporates.

 The reason why the AD8610 is the default choice is because it is both Morsel and my preference. It measures very well and sounds very good. I also think that it makes good synergy with the MOSFETs.


----------



## skyskraper

ive currently got my m3 mated to k240s with opa627 opamps and it sounds great. i suspect a "brighter" chip like the 8610 would do an even better job with the k240's. 

 the consensus seems to be the 8610 provides a great sound and isnt too expensive at all. without browndogs/mounting its about 1/3rd of the price of the opa627.

 i got my opa627's mainly because it was easily available locally to me, whereas the 8610's werent. havent gotten the ad's yet simply because i havent had the spare money to do so when i've ordered from tangent/amb.


----------



## andante

skyskraper, I noticed on your website that you used "fake alps" pots. Are you referring to these stepped pots:

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

 They would cost $5 less then getting regular alps pots, and since they are sold in pairs, they could be used for both bass boost and volume.

 Any reason to not get these?

 Thanks.


----------



## amb

Quote:


  Originally Posted by *andante* 
_skyscraper, I noticed on your website that you used "fake alps" pots. Are you referring to these stepped pots:

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW_

 

More info about the fake Alps pots can be found in this thread:
http://www.head-fi.org/forums/showth...threadid=11704

 The ones that you link to above do look like the fake ones. One telltale sign is the "RH27" designation. The real Alps blue velvets that we know and love are RK27.


----------



## skyskraper

yep same ones, i bought em to try out completely forgetting about the fake deal, i thought it's still a cheap enough price to not get hugely upset. at the time i wasnt going to be ordering from tangent and amb didnt have his site ready to go yet, proper blue velvets are very pricey down under, more then double the price these two upstanding members charge for them!

 as i said, no complaints. its pretty good actually. but i'm not likely gonna go out of my way again for them in the future. 

 if its only $5 difference id say go for the real deal. and you'll get em at the same time as your other parts too


----------



## jasonhanjk

5 dollar for one is a rip off. If you know who's who, you can get the same immitation a dollar each.


----------



## n_maher

Well, I needed an excuse to avoid the dreaded "American Idol" that was dominating my TV and wanted a temporary enclosure for my M³ so that I could loan it to a friend with a pesky cat while I'm on vacation next week.

 The results, one heck of a mint-tin amp... and yes, it's designed to run with the top off. The top merely serves as a cover to keep the internals safe while it's stored. It's too pretty to look at not to show off.

 Here's what I came up with:












 [edit]Link to a few more pics


----------



## MisterX

Nice casework!


----------



## amb

Quote:


  Originally Posted by *n_maher* 
_The results, one heck of a mint-tin amp..._

 

The mother of all mint-tin amps


----------



## looser101

With a couple small hinges and a prop rod to keep the lid open at a 45 degree angle while in operation....it might just be the ultimate low buck DYI case.

 -R-


----------



## phobus

Quote:


  Originally Posted by *n_maher* 
_The results, one heck of a mint-tin amp... and yes, it's designed to run with the top off._

 

Nice work! I think you might be able to run it with the top on if you are willing to put some holes in that cool tin 
	

	
	
		
		

		
		
	


	




 On second thought, the prop rod idea is probably better.


----------



## n_maher

In a couple of week's time this amp will get transplanted to one of the "group-buy" cases. I've got some special plans for that case though, it won't be all metal is all I'll say 
	

	
	
		
		

		
		
	


	




.

 This was merely a temporary measure and good fun at that. I've got almost enough spare parts for another M³ so I'll keep this case around just in case.

 Have I mentioned lately how much I love how this amp sounds!

 N


----------



## SHLim

Will appriciate some advice for my 1st headamp project. Have build a diy power amp and now need a preamp to go with it. I have received my M3 pcb and plan to use it as home stereo preamp with headphone jack. 
 The preamp will have voltage gain = 1.6, dB=4.0 with no bass boot. Will this work with M3? From my calculation R4=3.32K and R3=5.62K. is that all I need? 
 I plan to use a 4PDT switch that will allow me to switch between headphone and power amp. The part I am not sure is the earth to power amp, where should I connect that to? 

 Will start with a wallwart ps and if nothing exploded, will buid an internal Steps using 15VA +/-12v transformer (part # 70052) into 24V. Will this be overkill for the voltage gain that I plan to have?

 TIA,
 Sam


----------



## amb

Quote:


  Originally Posted by *SHLim* 
_The preamp will have voltage gain = 1.6, dB=4.0 with no bass boot. Will this work with M3? From my calculation R4=3.32K and R3=5.62K. is that all I need?_

 

If I understand you correctly, you want the M³ to serve as a preamp as well as a headphone amp, right? If so, and assuming it will have normal line-out level source(s) connected to its input, then a voltage gain of 1.6 may be too low for many headphones, and definitely low for most power amps of significant power output. Most standalone active preamps' internal line stage have a gain around 10 (20dB).

  Quote:


 I plan to use a 4PDT switch that will allow me to switch between headphone and power amp. The part I am not sure is the earth to power amp, where should I connect that to? 
 

The "pre-out" connections to the power amp should have their ground connected to the signal ground (i.e., IG on the M³ board). Only the headphone output should have its "ground" connected to the output of the ground channel (OG).

 Edit: BTW, you don't need to use a 4PDT switch. Just a DPDT should be enough. There is no need to switch the grounds.


----------



## SHLim

Quote:


  Originally Posted by *amb* 
_If I understand you correctly, you want the M³ to serve as a preamp as well as a headphone amp, right?_

 

Yap

  Quote:


  Originally Posted by *amb* 
_If so, and assuming it will have normal line-out level source(s) connected to its input, then a voltage gain of 1.6 may be too low for many headphones, and definitely low for most power amps of significant power output. Most standalone active preamps' internal line stage have a gain around 10 (20dB)._

 


 Voltage gain of 1.6 will be sufficient for my AKSA100n power amp, it has the gain of 32. I am currently using a 10K DACT attenuator to control the volume and been using it for more than 6 month without major complain. BTW, the AKSA TLP preamp only has gain of 0.95 and the AKSA GK1 preamp has gain of 2.3 and a lot of users even drop it to 1.6. As for headphone well I only have a not so glamorous DT660 which is quite sensitive and I don’t listen in high volume anyway. 


  Quote:


  Originally Posted by *amb* 
_
 The "pre-out" connections to the power amp should have their ground connected to the signal ground (i.e., IG on the M³ board). Only the headphone output should have its "ground" connected to the output of the ground channel (OG) 

 Edit: BTW, you don't need to use a 4PDT switch. Just a DPDT should be enough. There is no need to switch the grounds. _

 

Thanks for that 
	

	
	
		
		

		
		
	


	




 Sam


----------



## Jaypetermen

Quote:


  Originally Posted by *amb* 
_Right now I am listening to music via an M³ amp driving a pair of bookshelf speakers in my bedroom. It's quite impressive what this little "headphone amp" could do!_

 

What is the efficiency of your bookshelf speakers and is the M³ stock? 

 How do you wire the speaker to the M3? 1/4" phone plug split into separate left and right channel cables, with a shared ground?


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_What is the efficiency of your bookshelf speakers and is the M³ stock?_

 

Yes, except that I am powering it with a 3A bench supply adjusted to 36V. The speakers are around 88dB SPL/W/m. It plays quite nicely at levels that won't disturb my neighbors 
	

	
	
		
		

		
		
	


	




 . 

  Quote:


 How do you wire the speaker to the M3? 1/4" phone plug split into separate left and right channel cables, with a shared ground? 
 

Yes. I made a 1/4" phone plug to four female banana jack adapter for this, although in my next M³ build I'll probably just mount binding posts on the rear panel of the case.


----------



## Jaypetermen

Quote:


  Originally Posted by *amb* 
_Yes, except that I am powering it with a 3A bench supply adjusted to 36V._

 

At 36V are you are not using the AD8610AR? 

  Quote:


  Originally Posted by *amb* 
_..., although in my next M³ build I'll probably just mount binding posts on the rear panel of the case._

 

Would you need the switch the outputs, if you have both a 1/4" phone jack and speaker binding posts or just disconnect the unused device (cans or speakers)?

 Same question with inputs, can you run multiple inputs in parallel or should they be switched?


----------



## ub312g0d

There is no need for a switch when using multiple outputs, its just like a Y-splitter. You do a need a switch or a little bit of extra non mmm related circuitry for multiple inputs.


----------



## Magsy

I have them wired off a switching headphone jack, so when the plug is pulled the rear outputs go live (pre or speakers)


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_At 36V are you are not using the AD8610AR?_

 

Of course not, that would have fried the AD8610s. I have a bunch of different opamps to roll... 
	

	
	
		
		

		
			





  Quote:


 Would you need the switch the outputs, if you have both a 1/4" phone jack and speaker binding posts or just disconnect the unused device (cans or speakers)? 
 

One could use "switched" headphone jacks, these are jacks that have built-in switches (switches to headphones when you plug them in, or routes to the speaker outputs when unplugged). Or, you could just wire everything together and plug/unplug everything manually.

  Quote:


 Same question with inputs, can you run multiple inputs in parallel or should they be switched? 
 

No, you can't connect multiple inputs together. You need a selector switch for that.


----------



## Jaypetermen

Quote:


  Originally Posted by *amb* 
_You need a selector switch for that._

 

My Par-Metals M³ Group Buy Option A enclosure is already at max capacity.

 Darn, I should have ordered an Option B instead to fit the R/L speaker binder posts and an input selector switch. LOL


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_My Par-Metals M³ Group Buy Option A enclosure is already at max capacity.

 Darn, it should have ordered an Option B instead to fit the R/L speaker binder posts and an input selector switch. LOL_

 

You should be able to fit two sets of RCA inputs, a DPDT toggle switch for input selector, and two pairs of speaker binding posts on the rear panel.


----------



## skyskraper

dammit, now i have to try this. off to buy some binding posts....


----------



## amb

Quote:


  Originally Posted by *skyskraper* 
_dammit, now i have to try this. off to buy some binding posts.... 
	

	
	
		
		

		
		
	


	


_

 

If you will be driving speakers with the M³, replace D1 with a 1N5401 (rated 3A) diode. The default 1N4001 is rated at 1A. The 1N5401 is physically larger than the 1N4001, so it should either be mounted vertically (tombstone style) on the board, or you could form the leads inward.


----------



## skyskraper

no problems! i have one around i think or similar one hehe.

 did most of my case work and got the tread boards yesterday, picked up the transformer, tread parts, and associated case hardware today. should have a completed amp this afternoon


----------



## amb

For those who want to drive speakers with the M³, here are some additional considerations (aside from D1 already described above).

 The TREAD is a more flexible PSU board to use than the STEPS for the following reasons:
The TREAD's power transformer is off-board, so you aren't restricted to the Amveco 15VA or 25VA sizes that the STEPS board could accommodate. You could use a 50VA or larger transformer.
You could use a LT1083 3A regulator (instead of the LM317 1.5A).
You could put a large sized heat sink on the regulator and orient the heat sink fins outward, thus avoiding interfering with other parts on the board.

 The bridge rectifier specified for the TREAD is a 1.5A unit, but you could fit a BR31 100V 3A unit (Mouser #583-BR31) with a little lead bending.

 With the beefed up power supply, the M³ board's C7 rail capacitance may be increased to about 6000uF.

 Allow good ventilation for both the MOSFETs and the voltage regulator. For the MOSFETs, the minimum size heat sink for speaker loads should be the 1.5" tall version.

 Together, these would make a really nice 6Wrms per channel (into 8 ohms) speaker power amp if you set the TREAD up for 36V DC and use an opamp that could handle the voltage. At 24V DC, the power output is about 2.5Wrms. The actual output power varies with the opamp choice because some opamps could swing more voltage than others at a given PSU voltage.


----------



## skyskraper

*sniff* hrmm smell another project for amb and morsel, maybe a M³ inspired speakers amp? 
	

	
	
		
		

		
		
	


	




 on the tread board, the holes are pretty small, so some parts may or may not fit in. for example the 0.1" headers i have don't fit. the holes are just the tiniest bit too small. and a lot of the small holes are quite close together, so take a tiny bit more thought when assembling. would be nice to see a slightly larger version spaced out a bit more with bigger holes/pads


----------



## Syzygies

Quote:


  Originally Posted by *skyskraper* 
_*sniff* hrmm smell another project for amb and morsel, maybe a M³ inspired speakers amp? 
	

	
	
		
		

		
		
	


	


_

 

I'd rather see them redefine the shirt-pocket category!


----------



## pabbi1

... or, mayhaps, a tube implementation?

 The old term 'duck & cover' comes quickly to mind...


----------



## MisterX

That would be an interesting combo............ M3 tube variant


----------



## ub312g0d

I just finished up my build of my mmm and it mostly works. dc offset's are: left 1mV, ground=0.1mV and right is 200mV 
	

	
	
		
		

		
		
	


	




 The last one of course being FAR too high. The right channel is also making a constant buzing so I took a video with the scope to see if anybody can figure out what it is. VIDEO its only like a 300k file btw. The scope is at .1V/division vertical and at 5mSEC/division horizontal. Another odd thing is that while R9L and R9G go down to ~85mV, R9R stays at around 97mV Would be able to take any other measurements if I know where to take them if that would help at all.


----------



## wistily

Due to my newbeeness, i have destroyed my C1s (or at least two of them).
 These are Golden max one.
 Now, since i would avoid to make an order with 21$ shipping fee just for that, could i buy some replacement caps at a local store ?
 These are 10 pF npo 100V 10%, with no brand.
 Will there be a decrease in quality compared to the golden max ?


----------



## MisterX

Quote:


 Will there be a decrease in quality compared to the golden max ? 
 

Were the "golden max" caps npo as well? 
	

	
	
		
		

		
		
	


	



 Even if you put the cheapest garbage you could find in there I don't think you would notice much of a difference


----------



## amb

Quote:


  Originally Posted by *ub312g0d* 
_right is 200mV 
	

	
	
		
		

		
		
	


	




 The last one of course being FAR too high. The right channel is also making a constant buzing so I took a video with the scope to see if anybody can figure out what it is. VIDEO its only like a 300k file btw. The scope is at .1V/division vertical and at 5mSEC/division horizontal._

 

Something is definitely not right with your right channel, but I am not sure what to make of the scope video... it's too jumpy. Check all your solder connections to make sure there are no bridges or cold joints. Verify them with multimeter measurements. Check the orientation/polarity of all parts.

 Try swapping the opamp between the left and right sides. Does the problem remain on the same side? Also, what is the voltage drop across R5 on the problematic channel? Were you able to adjust the BIASOP trimpot on that channel successfully? Lastly, check the voltages (relative to IG) at each side of C2 on that channel too. Let me know what you get.

 What opamps are you using and what's your voltage gain setting and value of C1? Other descriptions of the parts you used would also be helpful.


----------



## amb

Quote:


  Originally Posted by *wistily* 
_Due to my newbeeness, i have destroyed my C1s (or at least two of them).
 These are Golden max one.
 Now, since i would avoid to make an order with 21$ shipping fee just for that, could i buy some replacement caps at a local store ?
 These are 10 pF npo 100V 10%, with no brand.
 Will there be a decrease in quality compared to the golden max ?_

 

Any NP0 (C0G) multilayer ceramic or silver mica capacitor of the appropriate value should work. There isn't really a sonic issue here, because this is a compensation cap that acts only in the ultrasonics (megahertz range), well out of the audio band.


----------



## rjkdivin

I have three M3 boards working beatifully, and one already cased up....pics soon. My problem is with my STEPS PS(s). I have had the same problem with two of them......Upon initial set-up everthing is fine and I adjust VSET to a perfect 24v.....where it stays perfectly until I try to use it.

 When I hook it to my separately cased M3, it is apparently destroying some part of the regulator circuit because the voltage then goes up to 48v and stays there from then on. My readings after the failure are TP 1-2 37.07vac from the transformer; TP 3-5 49.17vdc unregulated (and 19.9mvac): TP 4-5 47.85vd....supposed to be regulated, but obviously not!!!! 

 I'm using R3 at 120ohm, R4 at 2.2kOhm, and Vset at 500ohm. The transformer is the Amveco 70063K 15v + 15v at 12.5VA + 12.5 VA.

 The same M3 I am attempting to power works perfectly with a 1 amp wall wart....and sounds magnificent!

 Any suggestions as to what component I am killing and why?


----------



## rjkdivin

I finally got the time to get these finished. Now if I can just find out what I am doing wrong with the STEPS.


----------



## MisterX

rjkdivin: Very Very nice!
 Is the regulator and or heat sink shorting to the case? 
 How tall are the standoffs in the amp?


----------



## primer

Looks good, what sort of casing is it?


----------



## wistily

I'm curently mounting the heatsinks on the board, but i think i do it wrong:
http://jjlapin.free.fr/photos/m3/
 Should i better cut the keratherm (insulating sheet) so that the "hole" under the heatsink can be free ?


----------



## bg4533

rjkdivin,
 How much rail capacitance do you have for the M3? I remember a few people using the PPA with 6000uF+ on the rails and blowing up regulators.


----------



## rjkdivin

Quote:


  Originally Posted by *MisterX* 
_rjkdivin: Very Very nice!
 Is the regulator and or heat sink shorting to the case? 
 How tall are the standoffs in the amp?_

 

No....the PS regulator and heatsink are not shorting to the case....about 8mm standoffs below the pcb and about 5mm clear above the heatsink. The standoffs for the M3 board are 5mm with a similar clearance above the tops of the heatsinks. I am using AMBs Method 1 wiring....everything isolated except the M3 input ground and pot housings. 

 The cases are all anodized alum except the back plates that I had to make....they are painted alum. I haven't yet connected the IG to the Vol and Bass pot housings...but the measured resistance there is only about 7ohms and I'm not getting any hum at all. In fact it is amazing how quiete the M3 is.


----------



## rjkdivin

Quote:


  Originally Posted by *bg4533* 
_rjkdivin,
 How much rail capacitance do you have for the M3? I remember a few people using the PPA with 6000uF+ on the rails and blowing up regulators._

 


 No I'm just using the 3 - 330uf caps on each channel. But it seems something is blowing the regulator?????


----------



## rjkdivin

Quote:


  Originally Posted by *primer* 
_Looks good, what sort of casing is it?_

 


 The cases are Silverstone LaScala Nano ATX cases. They were expensive, but I was also able to salvage the power supplies from them that I hope to utilize for an M3/Transport/DAC project.

 I had to build new back plates because the stock ones had cut-outs for USB ports and the like. The nice thing is I could use the built in front panel leds for the power indicator leds. I had to do a little work to fit in the rocker switches in place of the momentary contact switches that came with the cases.

 Both side pieces are slotted for ventilation, but I added the round holes above the heatsinks.


----------



## skyskraper

what a great idea!

 home theatre cases are so varied these days and look so pretty


----------



## amb

rjkdivin, great looking cases!

 For your PSU problems, I wonder if the STEPS' regulator IC itself is being blown, or if the problem is with D2. Try removing D2 and measure it using the diode test function on your DMM. Also, the regulator's body is internally connected to the Vout pin, if it is not mounted to the heat sink with insulators, make sure the heat sink doesn't touch anything else. How is the ground wired up in the STEPS case? Are the V+ and V- outputs totally floating (they should be)?


----------



## amb

Quote:


  Originally Posted by *wistily* 
_I'm curently mounting the heatsinks on the board, but i think i do it wrong:
http://jjlapin.free.fr/photos/m3/
 Should i better cut the keratherm (insulating sheet) so that the "hole" under the heatsink can be free ?_

 

There is no need to cut the insulating sheet. Your photos look fine. Measure the resistance between the metal tab of the MOSFETs and the heat sink and you should read "infinity".


----------



## rjkdivin

Quote:


  Originally Posted by *amb* 
_rjkdivin, great looking cases!

 For your PSU problems, I wonder if the STEPS' regulator IC itself is being blown, or if the problem is with D2. Try removing D2 and measure it using the diode test function on your DMM. Also, the regulator's body is internally connected to the Vout pin, if it is not mounted to the heat sink with insulators, make sure the heat sink doesn't touch anything else. How is the ground wired up in the STEPS case? Are the V+ and V- outputs totally floating (they should be)?_

 

Hi AMB,

 I replaced the regulator (again). It is holding this time, but running very warm when hooked to any of my M3s....about 145 to 150 deg F. The 24v output is stable.

 The The IC is not insulated, but the STEPS board isolates the heat sink and it is not touching anything. The V+ and V- outs are completely isolated. The mains ground is also isolated from the case. I was wondering if I am just dropping too much voltage......the transformer is 15v. + 15v. ? (the 12 + 12 is on back order)

 I don't think D2 is failed....do you think I should check it anyway?


----------



## rjkdivin

To AMB and Morsel,

 To second some other comments regarding the performance of the M3.....it is quite amazing. The sound is awsome, and it is absolutely noiseless. Thanks again for the unbelievable effort.....and for the continuing help!!!!


----------



## n_maher

Quote:


  Originally Posted by *rjkdivin* 
_The 24v output is stable._

 

My steps also ran quite hot at 24V, however you should be able to safely crank the output voltage up to 27V and reduce the regulator temp some. Even if you're using the AD8610's this will still produce a safe working voltage for the opamps. This is assuming that you've got a stock M3 setup that drops a couple of volts before the opamps.

 See this thread for a bit more information. And nice work on those enclosures!

 HTH,

 Nate


----------



## amb

Quote:


  Originally Posted by *rjkdivin* 
_I replaced the regulator (again). It is holding this time, but running very warm when hooked to any of my M3s....about 145 to 150 deg F. The 24v output is stable._

 

OK, maybe the heat is cooking your regulator. While you're waiting for your 12V+12V transformer, adjust the output voltage of your STEPS up to 27V if you are using AD8610 opamps, and run with the top cover of the PSU top cover open. This will help reduce the dissipation a bit. If the regulator is mounted directly to the heat sink then make sure it has heat sink compound on the mating surfaces for maximum heat transfer.

  Quote:


 (D2) do you think I should check it anyway? 
 

If replacing the regulator fixes the problem (even for a just a while) then D2 should be fine.


----------



## wistily

I'm doing initial setup.
 I'm at test 7, measuring the voltage between pins 4 and 7 of the G opamp. I got only 15V here (with a PSU@ 25V).

 Anyone has an idea ?


----------



## amb

Quote:


  Originally Posted by *wistily* 
_I'm doing initial setup.
 I'm at test 7, measuring the voltage between pins 4 and 7 of the G opamp. I got only 15V here (with a PSU@ 25V).

 Anyone has an idea ?_

 

What opamp are you using? With only one opamp in, and if the opamp is a type that has low quiescent current draw, then it's possible that Q5+ and Q5- is dropping more voltage than with all three opamps installed.

 Next to the C8 capacitor closest to the back edge of the board, you will see two "unused" pads that are actually vias. These are connected to the collector pins of Q5+ and Q5- respectively. Measure the voltage drop across the Q5+ transistors by touching the red meter probe on the outer via and the black probe on pin 7 of your opamp. Then measure the voltage drop of across Q5- between the inner via and pin 4 of the opamp. The two readings should not be too different (within a volt or so).

 Then measure the voltage from the opamp's pin 7 to IG, as well as the opamp's pin 4 to IG. These should be just about exactly half of what you get between pins 7 and 4.

 If your measurements all pass these guidelines, then it's should be fine. As you install and set up the other channels the drop across the Q5s should decrease, and you'll read more voltage across pins 7 and 4 of your opamp.

 I think I'll relax the voltages listed on my site a bit for this step.

 EDIT: Also, make sure you're counting the opamp pins correctly. See the opamp datasheet for the pin numbers (you go in a counter-clockwise fashion starting from pin 1). I think someone else made a mistake with this and was actually measuring at pin 6 rather than pin 7.


----------



## wistily

*Sorry, i'm really messing with the pins number, i will do the checkings again.*


----------



## wistily

LOL, that was that, i was messing with pins numbers.

 Sorry to have make you loose your time.


----------



## wistily

And now, an other working M3 
	

	
	
		
		

		
			




 I can't really comment on the sound since my 880 has been at beyer for a checkup for 6 weeks (grrrrr) and i'm trying it on a old sony crap, but the numbers are good:
 -IG/OL offset 0.7mV
 -IG/OR offset 0.4mV
 -IG/OG offset 0mV 
	

	
	
		
		

		
		
	


	




 (i hope i'm just lucky and nothing's wrong).

 Thank you all for your help, and especially team M3 for your hard work 
	

	
	
		
		

		
		
	


	




 Now will come the harder part: finding a case or building one.


----------



## ub312g0d

ok, heres the measurements that you wanted me to take amb..
 Vc2-Ig=fluctuates between 3.3-3.6V(right channel)
 Vc2-Ig=3.59V(left channel)
 Vr5=500mv for all three channels.

 My parts are from the bom list supplied on your site except for C1r+C1L=24.1pf silver mica. C7 is 3x1000uf nichon electrolytics. gain is set at ~7(r3=2k,r3=12.1k). Opamps are opa627's on all channels right now. Same thing happening with opa 637's as well. Swapping opamps has no effect on the problem.

 Rechecked solder points numerous times and all look good. Bad thing I noticed those is that there is 2 black marks beside Q4R and Q3R so it is possible that unnoticed stray wire/clippings could have shorted them out or the like? how could I test them to see if they are still functioning properly?


----------



## amb

ub312g0d, if you're getting a stable voltage across R5R, then Q3R and Q4R are most likely working fine. Since you're getting a fluctuating bias at C2R, I suspect that maybe the problem is with Q2R. It's not totally dead, but seems to be misbehaving. Try replacing it and see if it makes a difference.


----------



## rjkdivin

Hey folks,

 I have posted a review of the M3 on the Amplification Forum under a new thread:

http://www6.head-fi.org/forums/showt...76#post1364976

 Please feel free to have a look and add comment as you feel appropriate. A few of you have already posted reviews on this forum, but I thought it would be good to share our enthusiasm as the M3s are coming on line in greater numbers now.

 Thanks again AMB and Morsel!!!


----------



## amb

Thanks rjkdivin for the excellent review! I hope the journey of building the amps is as much fun as it is to listen to the final results. We're all hooked...


----------



## bg4533

Quote:


  Originally Posted by *amb* 
_Yes, except that I am powering it with a 3A bench supply adjusted to 36V. The speakers are around 88dB SPL/W/m. It plays quite nicely at levels that won't disturb my neighbors 
	

	
	
		
		

		
		
	


	




 . 


 Yes. I made a 1/4" phone plug to four female banana jack adapter for this, although in my next M³ build I'll probably just mount binding posts on the rear panel of the case._

 

I have been considering an M3. The ability to power speakers makes it even more interesting.

 What sort of PSU will be necessary to power speakers? I am guessing a Steps with 25va transformer won't be enough.


----------



## wistily

Look here:
http://www.amb.org/audio/mmm/


----------



## amb

Quote:


  Originally Posted by *bg4533* 
_I have been considering an M3. The ability to power speakers makes it even more interesting.
 What sort of PSU will be necessary to power speakers? I am guessing a Steps with 25va transformer won't be enough._

 

I make some recommendations for driving speakers on my M³ site, under the "Power supply" as well as the "Options" sections. However, that recommendation (3A) is somewhat conservative. You could use a STEPS and it would still work reasonably well. A 25VA transformer won't deliver its full rated voltage when you exceed its current rating, but it won't catastrophically fail if the overcurrent condition is transient (as it would be during music peaks when driving speakers), plus the power rail reservoir caps help to supply the peak demand as well. You could also use a larger, leaded transformer (like a Avel-Lindberg or Plitron toroid) and either mount it on the STEPS board or separately in the case. I also recommend using a LT1085 or LM1085 3A regulator, along with TO-220 style Schottky rectifier diodes, and good case ventilation for the regulator and the MOSFET heat sinks. If your speakers are efficient and your room not too large, you'd be surprised by how "studly" this little headphone amp is, thanks to those MOSFETs.


----------



## amb

For those who are using the group buy Par Metal cases, here are a few hints and thoughts.

The anodizing makes the surface of all the case panels electrically insulated. This means that even when you assemble all the pieces together, the panels are most likely not making electrical contact with each other. For proper shielding (to avoid hum/noise), you should grind off just a little bit of the anodizing at the inside of the screw holes. Use your multimeter in ohms mode to verify that all panels are making good electrical contact after you fit everything together.
In these 2.5" cases, if you use 1/2" standoffs to elevate the M³ board, it would place the shaft of the onboard Alps blue velvet volume and bass boost controls very close to the centerline of the front panel.
Note that if you want the front side of the pcb to be flush with the inner front panel, the two front standoffs will be over two layers of aluminum, one is the case bottom, and the other is the bottom lip of the inner front panel. You should drill large enough holes on the inner front panel lip to allow the standoff to go through to the bottom plate so that the board will sit level. Or else, you would have to shorten the front standoffs a bit, but that could be a pain to do.
An alternative is to set the board back a bit, so that all four standoffs will be directly on the bottom plate. Depending on how far back you go, there may still be enough pot shaft through the front panel for some knobs; or you could move the board even farther back and use couplers/panel bearings. These solutions means that you won't be securing the pot to the front panel with the pot's nuts. So you'll have to add the extra wire to ground the volume pot body (see my site).
One further alternative, and this maybe the easiest one, is to use standoffs only at the rear of the board, and rely on the pot's nuts to secure the front of the board.

 Just thought I'd throw some ideas out there. Have fun with your casework.


----------



## Akku

I have completed my M3 board and now I am testing it but something strange is happening. First, I hear a steady noise even with 300ohm cans, only with 600 ohm k240 is not clearly audible. RMAA tells me is a huge 50hz hum. I know that this sort of problems usually disappear with casing and proper grounding but is really huge.
 Second, today I measured DC offset and I got 4-5 mv in the L and R channels. Nothing really bad but I swear I mesured it yesterday and the results were less than 1mv in all three channels!
 PS voltage is OK, 26,3 volts from STEPS become 24 volts (railtorail) at op-amp's (AD8610) pins.
 Third, with not attenuation (pot completely open) the amp seems to clip badly even if the level from the source is low.
 Fourth, the current bias for Mosfets is a bit instable. Slowly decrease after powering on the amp, is it normal?
 Fifth, I got the impression the amp has less gain than expected but it could be just a fake impression
 Standard parts except the pot that is a 10k step. att.

 Edit:n.2 solved, I am stupid, this time I mesured offset with bass boost on. Without the offset is in the 0,5-1 mv range.


----------



## individual6891

Is it ok to use something higher for C4 (eg 220-330uF?)


----------



## morsel

Akku: Your hum may be due to improper grounding as you suggest, or improper RMAA testing, or both. A CRT monitor will radiate all sorts of noise, for example, and must not be anywhere near the circuit. Everything must be shielded, including the cables, and proper grounding is essential.

 MOSFET bias current will slowly decrease as the MOSFETs warm up.

 If you are clipping at low volume and are not sure what gain your amp is operating at, it sounds like you need to take some measurements and check out your amp more thoroughly. Did you follow amb's detailed construction instructions?

 individual6891: It should be OK to use somewhat higher values for C4. C4 and C5 were intentionally specified to use the same component to simplify parts stocking. If you go too high with these caps, the opamp rail may ramp up to full voltage too slowly. If you are having trouble finding 100µF caps of the right size, use the 50WV flavor, they should fit perfectly.


----------



## Akku

Thank you Morsel for your suggestions.
 RMAA could fail but I hope my ears don't 
	

	
	
		
		

		
			




 Building the PPA I had the same experience, casing the PCB the noise disappeared. This time is really huge.
 No wonder there is somenthig wrong in the grounding with all those clip wires I am using hanging everywhere. Connecting cans to the jack socket the DC offset in ground channel raise to 30mV (something is collapsing virtual ground?).
 I guess it is useless to test the AC behaviour of the amp until I fix this problem casing and wiring properly everything.


----------



## DigiPete

I noticed after I assembled the board that C1G should only use the 33pf cap. I put in 15pf caps for all three channels. I am using the 827bp op amps for all three channels. The amp sounds great!

 Is this of concern? Should I unsolder the C1G and put the 33pf in?

 Thanks
 Pete


----------



## amb

Quote:


  Originally Posted by *DigiPete* 
_I noticed after I assembled the board that C1G should only use the 33pf cap. I put in 15pf caps for all three channels. I am using the 827bp op amps for all three channels. The amp sounds great!
 Is this of concern? Should I unsolder the C1G and put the 33pf in?_

 

I recommend 33pF for the ground channel. You might not hear any anomaly with a smaller value cap, but the 33pF value was chosen with extensive testing and is optimized for best stability and bandwidth.


----------



## DigiPete

Quote:


  Originally Posted by *amb* 
_I recommend 33pF for the ground channel. You might not hear any anomaly with a smaller value cap, but the 33pF value was chosen with extensive testing and is optimized for best stability and bandwidth._

 

AMB thanks for the info.

 I'll swap it out.

 DigiPete


----------



## Akku

Quote:


  Originally Posted by *amb* 
_I recommend 33pF for the ground channel. You might not hear any anomaly with a smaller value cap, but the 33pF value was chosen with extensive testing and is optimized for best stability and bandwidth._

 

Ops 
	

	
	
		
		

		
		
	


	




 Now I realize i made the same mistake


----------



## andante

Quote:


  Originally Posted by *amb* 
_For primarily speaker use, I recommend using a 36V power supply rated at 3A, and opamps that could handle the voltage ... You should also increase the total C7 rail capacitance to 6000uF and upgrade D1 to a 1N5401. With this configuration you should have a very healthy 6W per channel (into 8 ohms) power amplifier._

 

Also from amb's website, about C7 capacitors:

  Quote:


 If you install too much capacitance for C7, the turn-on inrush current will be large and may cause damage to your power supply. It may also degrade the power connectors' contacts over time. Too much capacitance will also cause the amplifier DC rail voltage to discharge slowly after the amplifier is turned off, and this may cause undesirable noise at the output. 
 

I am considering using M3 amp to, in addition to headphones, drive a set of bookshelf speakers, to replace computer speakers on my desk. I would build it with above mentioned mods to make it speaker-ready, although for the time being, I would just use it with headphones and a 1A 24V THREAD power supply.

 How serious are the drawbacks of increasing C7 capacitance to 6000uF? Should I just simply get a Sonic T-amp for the speakers instead?

 Thanks.


----------



## andante

Using M3 with TREAD power supply, outboard wallwart, TREAD PCB housed with M3...

 Where do I put power switch? Between DC in and TREAD or between TREAD and M3? Do I need to switch both DC lines or just one, and which one if it matters?

 Thanks.

 (edited for correct spelling of TREAD)


----------



## amb

Quote:


  Originally Posted by *andante* 
_How serious are the drawbacks of increasing C7 capacitance to 6000uF?_

 

Don't increase to 6000uF unless your PSU is running with at least 3A regulators and other beefed-up mods as I previously outlined.

  Quote:


 Should I just simply get a Sonic T-amp for the speakers instead? 
 

Only you could make this decision. The T-amp is much cheaper than an M³, but I believe the M³ to be far superior (although it may not matter for driving computer speakers).

  Quote:


 Where do I put power switch? Between DC in and THREAD or between THREAD and M3? Do I need to switch both DC lines or just one, and which one if it matters? 
 

Put the switch inline with the power input jack in the amp. This way, when the switch is off, everything really is off. By the way, it's "TREAD". And typically you want an AC wallwart (containing nothing but a transformer), so it's an AC voltage going into the TREAD, not DC.


----------



## skyskraper

well depending on what AC powerpacks you have available to you, dc ones may be cheap (ie surplus stock or sitting around thehouse) 

 if you use dc you could save a few cents on the bridge and c1-4, then simply connect the input of the DC jack to the + and - pads on the bridge (ignoring the ac ~ pads) and use it like that. thats how id go about doing things if i had a DC powerpack


----------



## andante

Quote:


  Originally Posted by *amb* 
_Don't increase to 6000uF unless your PSU is running with at least 3A regulators and other beefed-up mods as I previously outlined._

 

Thanks, I was considering using 24V temporarily with 6000uF since I already have that. I guess that's out.
  Quote:


  Originally Posted by *amb* 
_Only you could make this decision. The T-amp is much cheaper than an M³, but I believe the M³ to be far superior (although it may not matter for driving computer speakers)._

 

I am definitely building an M3. I am mainly concerned about compromising M3's headphone driving suitability by trying to shoehorn it into both roles. That's why I'd consider separately using a T-amp or a gainclone or whatever for speaker duty. The draw of using M3 is that it would cost even less then a T-amp to get M3 from default configuration to the recommended "speaker configuration". In addition to caps/diode/voltage, I would also need a switch on output, and possibly an adjustable gain switch as well. I also want to have crossfeed. It would have to be completely bypassed when using speakers to recover a few dB. I'd try to accomplish all 3 tasks with one switch. Is all this extra wiring/switches likely to have a noticable or measurable difference on SQ?
  Quote:


  Originally Posted by *amb* 
_Put the switch inline with the power input jack in the amp. This way, when the switch is off, everything really is off._

 

Thank you. In my layman's view of electricity, I was wondering if having a pre-charged capacitor on TREAD would help when amp turns on.
  Quote:


  Originally Posted by *amb* 
_By the way, it's "TREAD"._

 

Funny how one's mind works... I've read Tangent's site a few times over, bought the kit, built the regulator, and for some reason "THREAD" is what stuck in my mind.
  Quote:


  Originally Posted by *amb* 
_And typically you want an AC wallwart (containing nothing but a transformer), so it's an AC voltage going into the TREAD, not DC._

 

That's what I would have thought, because redundant diode bridge, etc, didn't feel right intuitively, but it seems from Tangent's website and some posts here that he likes DC wallwart just fine, even with diode bridge on the TREAD. Other then the needless voltage drop, should this be a problem, and can I still use DC wallwart for now? BTW, what would be the benefit of using AC over DC wallwart (and skipping the bridge and C1-C5 on the TREAD)? Superior, or at least known, components/design?


----------



## amb

Quote:


  Originally Posted by *andante* 
_...
 Is all this extra wiring/switches likely to have a noticable or measurable difference on SQ?_

 

Ideally, the less switches and contacts you have, the better. But, whether such switching would actually affect SQ depends on the quality of the switch and the wiring work.

  Quote:


 Thank you. In my layman's view of electricity, I was wondering if having a pre-charged capacitor on TREAD would help when amp turns on. 
 

Funny you should ask this. In fact, I've received problem reports from another M³ user with exactly that configuration (actually, he has two power switches, one on the AC mains in the PSU, and another between the PSU DC output and the M³ board. Basically, if the PSU is already powered up, and then the M³ amp is then switched on, it would blow up the LM317 regulator. No such problem occurs if the M³ power switch is left on and the whole thing is powered on and off via the PSU power switch.

 The reason for this, IME, is because in the latter case, the LM317 is powered up at the same time as the amp, and there is a somewhat "soft" start-up due to the charging of the capacitor at the ADJ pin of the LM317. The soft start characteristic avoids any damage to the regulator even though there is significant amount of rail capacitance in the M³. When the PSU is already on and then you switch on the M³, we don't get that soft-start characteristic. Suddenly the LM317 is called upon to charge up 3000uF of capacitors plus whatever start-up operating current the amp itself requires. The result is a big current surge and would damage the regulator. He tried changing to a LM1085 3A regulator, and even though this regulator will not blow out in this circumstance, the surge is still big enough to cause it to go into current-limit shutdown, and the only way to reset it is to cycle the power.

 So, the moral of this story is, don't use too much C7 rail capacitance unless your PSU is up-to-snuff. And, if you have a power switch between the PSU and the amp, turn that on *before* turning on or plugging in the PSU.

  Quote:


 (AC wallwart vs DC wallwart for TREAD)
 That's what I would have thought, because redundant diode bridge, etc, didn't feel right intuitively, but it seems from Tangent's website and some posts here that he likes DC wallwart just fine, even with diode bridge on the TREAD. Other then the needless voltage drop, should this be a problem, and can I still use DC wallwart for now? BTW, what would be the benefit of using AC over DC wallwart (and skipping the bridge and C1-C5 on the TREAD)? Superior, or at least known, components/design? 
 

You _could_ use a DC wallwart with a TREAD if you like, and it's your choice whether you should leave-in the bridge rectifier and associated capacitors. They are not necessary with a DC wallwart, and introduces additional voltage losses, but they do provide a neat "benefit" -- you could connect the DC wallwart in either polarity and it would work. This is because the bridge rectifier becomes a polarity convertor in this setup.


----------



## andante

Quote:


  Originally Posted by *amb* 
_You could use a DC wallwart with a TREAD if you like, and it's your choice whether you should leave-in the bridge rectifier and associated capacitors. They are not necessary with a DC wallwart, and introduces additional voltage losses, but they do provide a neat "benefit" -- you could connect the DC wallwart in either polarity and it would work. This is because the bridge rectifier becomes a polarity convertor in this setup._

 

I can probably return the 24V AC/DC wallwart since I bought it locally and get an AC/AC one instead. They only have a 500mA AC/AC wallwart. Would you prefer this to 1.2A AC/DC supply for headphone-only use with TREAD?


----------



## amb

Quote:


  Originally Posted by *andante* 
_I can probably return the 24V AC/DC wallwart since I bought it locally and get an AC/AC one instead. They only have a 500mA AC/AC wallwart. Would you prefer this to 1.2A AC/DC supply for headphone-only use with TREAD?_

 

500mA is adequate for headphones, and probably cheaper than the 1.2A DC wallwart. My preference would be different than yours because I tend to use my amps in various ways (like driving speakers, or testing under severe loads, etc). This is why I have not built a STEPS, TREAD or other dedicated PSU for my own M³. I've been using an adjustable bench supply.


----------



## Akku

I retested the board and now the amp is working. No more problems with the ground channel (don't ask me why). I still have a little buzz, volume dependent, that magically disapper at full volume (no attenuation) but I guess casing and grounding the pot case will fix it. Just few minutes of listening but a great sound yet. Thanks M3 team!


----------



## primer

Which of amb method of securing the M3 board to the small ParsMetal case do you guys find most appropriate?


----------



## thrice

Well, one way is to drill holes in the bottom of the case and stick screws up through them and then use spacers to raise the board off the bottom of the case.

 You can get plastic or aluminum spacers from Mouser.


----------



## skyskraper

primer, depending on how tall a spacer you need, i find self adhesive ones from jaycar and altronics to be the most convenient, no hole measuring and cutting, and its easy to reposition the board. 

 aside from self adhesive spacers, i tend to use whatever size fits and is handy in my parts bin. nylon or metal doesnt matter hugely, i use the tapped ones. again jaycar and altronics have heaps and heaps and heaps to choose from 
	

	
	
		
		

		
		
	


	




 oh and if u cant find the exact size you need, u can always chop up an unthreaded nylon spacer (always handy to have) to the right size to piggyback on to another spacer.


----------



## primer

Quote:


  Originally Posted by *amb* 
_
In these 2.5" cases, if you use 1/2" standoffs to elevate the M³ board, it would place the shaft of the onboard Alps blue velvet volume and bass boost controls very close to the centerline of the front panel.
Note that if you want the front side of the pcb to be flush with the inner front panel, the two front standoffs will be over two layers of aluminum, one is the case bottom, and the other is the bottom lip of the inner front panel. You should drill large enough holes on the inner front panel lip to allow the standoff to go through to the bottom plate so that the board will sit level. Or else, you would have to shorten the front standoffs a bit, but that could be a pain to do.
An alternative is to set the board back a bit, so that all four standoffs will be directly on the bottom plate. Depending on how far back you go, there may still be enough pot shaft through the front panel for some knobs; or you could move the board even farther back and use couplers/panel bearings. These solutions means that you won't be securing the pot to the front panel with the pot's nuts. So you'll have to add the extra wire to ground the volume pot body (see my site).
One further alternative, and this maybe the easiest one, is to use standoffs only at the rear of the board, and rely on the pot's nuts to secure the front of the board.

 Just thought I'd throw some ideas out there. Have fun with your casework._

 

Thanks guys but I should reword my question and sorry for the misunderstanding. From the method described by amb, which will be the most appropriate method to use. The last option seems to be the easiest but the pot's thread only reaches the plate.


----------



## amb

Quote:


  Originally Posted by *primer* 
_... The last option seems to be the easiest but the pot's thread only reaches the plate._

 

By "plate" I assume you mean the outer front panel? Due to the thick front panel, indeed there is not enough thread length for the pot nut to be mounted on the outside of the front panel. What you could do is to fabricate a piece of L-shaped sheet aluminum bracket, bolt that to the bottom of the case and and mount the pot(s) to it:


----------



## DigiPete

Quote:


  Originally Posted by *primer* 
_Thanks guys but I should reword my question and sorry for the misunderstanding. From the method described by amb, which will be the most appropriate method to use. The last option seems to be the easiest but the pot's thread only reaches the plate._

 

Hi Primer,

 What I did was use 3/8" standoffs (this puts the pot shafts slightly below centerline, but that did not bother me since I am going to put labels above each knob). I positioned the PCB flush with the front panel. I marked up all the hole locations, with the bottom panel and front panel mounting bracket bolted together (I drilled through both from the bottom). Installed the pcb with standoffs, and I used a few spacers on the back pcb bolts and standoffs to raise the back of the pcb to level with the front. Pretty easy, and the pot shafts can be secured to the front panel with the existing nuts. 

 The hardest part is measuring, marking up, and drilling the holes precisely so it all lines up correctly (gulp!) Measure 10 times, cut once 
	

	
	
		
		

		
		
	


	




 PS. After mounting and tightening down the pcb, then make your final measurements for where to drill the front panel holes. I used the panel mounting bolts as my reference point.


----------



## primer

amb, not a bad idea. I will look around for a L-shape plate. This plate will secure the pot through to the front plate.

 DigiPete, thanks. I'm trying to minimise any more drilling than necessary because I've made a couple of mistakes to other cases before, so my confidence is a bit down.


----------



## DigiPete

Hi Folks,

 Here are some pics of my almost completed M³ in the Par-Metals Case 
	

	
	
		
		

		
		
	


	




 DigiPete


----------



## amb

Quote:


  Originally Posted by *DigiPete* 
_Here are some pics of my almost completed M³ in the Par-Metals Case 
	

	
	
		
		

		
		
	


	


_

 

Very neat! You gotta get some nicer knobs though


----------



## thrice

Nice job DigiPete...I would second amb's comment about the knobs


----------



## DigiPete

Quote:


  Originally Posted by *thrice* 
_Nice job DigiPete...I would second amb's comment about the knobs 
	

	
	
		
		

		
		
	


	


_

 

Thanks guys!

 I am open to getting better knobs, just don't know where?

 Any pics and links would be highly appreciated.

 DigiPete


----------



## thrice

Quote:


  Originally Posted by *DigiPete* 
_Thanks guys!

 I am open to getting better knobs, just don't know where?

 Any pics and links would be highly appreciated.

 DigiPete_

 

THL Audio has some nice knobs www.thlaudio.com

 Ordering from them is a bit of a pain since you have to fax it in.


----------



## MisterX

Quote:


 Ordering from them is a bit of a pain since you have to fax it in. 
 

They also accept email orders


----------



## bbm3

Very Nice work DigiPete.
 I have been on the fence about building an M3.
 Your pics just pushed me over the edge.
 Too bad I can't have it ready for Mothers Day.


----------



## DigiPete

Quote:


  Originally Posted by *bbm3* 
_Very Nice work DigiPete.
 I have been on the fence about building an M3.
 Your pics just pushed me over the edge.
 Too bad I can't have it ready for Mothers Day._

 

Great! Just do it. It was my first amp, and a great learning experience building it


----------



## DigiPete

Quote:


  Originally Posted by *thrice* 
_THL Audio has some nice knobs www.thlaudio.com

 Ordering from them is a bit of a pain since you have to fax it in._

 

Wow! Now those are some cool knobs...

 Thanks Thrice and Mr.X


----------



## rjkdivin

Some of you may recall that I had a problem with blown regulator ICs in my STEPS when I turned on my M3 (mounted in separate cases): 
	

	
	
		
		

		
		
	


	




). Originally I thought it might be the high operating temperature of the regulator, but through a process of elimination (many wasted regulators), and a lot of help from AMB, I finally figured out the actual failure sequence, cause and a solution.

 The regulators would blow if I turned on the power supply first, and then the M3 afterward. If I turned on the M3 switch before the PS, they worked fine. I tried switching from the LM317 (1amp) to the LM1085 (3amp) and they stopped blowing, but they would still trip out, and required powering down before they would operate again. I also tried some low resistance, high wattage resistors in series between the STEPS and M3, but it did not help.

 The cause of the problem was a current spike to charge the rail capacitors when the M3 was turned on. If the M3 and STEPS power up simultaneously, there is not a huge spike. But I wanted the separate switch on the M3 case so I could operate it with a wall wart if I wanted to. In a single case build with a single switch, this would not be a problem.

 Thankfully, AMB found a 5amp current limiting regulator with the T0-220 architecture that just drops into the pcb and heat sink. It now works flawlessly regardless of which component is turned on first.

 The regulator is available at Digi-Key and the Manufacturer No. is LM338T-ND.


----------



## skyskraper

cool 
	

	
	
		
		

		
		
	


	




 out of interest whats your power rail capacitance on your m3?


----------



## amb

To chime-in on rjkdivin's post above, the following paragraph from the LM138/338's datasheet is the characteristic that makes the crucial difference:

  Quote:


 "A unique feature of the LM138 family is time-dependent current limiting. The current limit circuitry allows peak currents of up to 12A to be drawn from the regulator for short periods of time. This allows the LM138 to be used with heavy transient loads and speeds start-up under full-load conditions. Under sustained loading conditions, the current limit decreases to a safe value protecting the regulator. Also included on the chip are thermal overload protection and safe area protection for the power transistor. Overload protection remains functional even if the adjustment pin is accidentally disconnected." 
 

For this reason, those of you who are using a LM317T-based PSU for this (and other amps), and want to have a power switch between the PSU and the amp, I recommend using the LM338T instead. The LM338T is pin-compatible with the LM317T, and is inexpensive at $1.98 from Digikey.


----------



## rjkdivin

Quote:


  Originally Posted by *skyskraper* 
_cool 
	

	
	
		
		

		
		
	


	




 out of interest whats your power rail capacitance on your m3?_

 

My total capacitance is 2970uf.


----------



## rjkdivin

Nice job DigiPete!

 I suppose we will all have similar looking M3s resulting from the Par Metals group buy, but there are still variations possible. I still like to put a switch on the front. I am currently listening to Enigma from my Nakamichi Dragon to this M3 thru some Sennheiser Hd-600s....awsome!!!


----------



## wistily

Newb question: how do you do the holes in the thick aluminium ? I have tried with a dremel with no success. What's the magic trick, especially for big things like the iec inlet, or the neutrik ?


----------



## skyskraper

a proper drill is your best friend. there was a thread a couple of weeks ago on cutting iec inlet's and a few techniques on how to do them.

 proper drill either held in your hand or a press, and a decent set of drill bits, possibly a stepped bit, will work wonders for your casework. 

 larger stuff like iec inlets and 20mm+ holes you can also get punche's that will do the trick 
	

	
	
		
		

		
		
	


	




 i just got a 25mm punch for my neutrik combo jacks, it wasnt too pricey at all, a lot cheaper then the equivalent drill bit. have yet to run it though so i can't tell you what the results are like yet.


----------



## rjkdivin

Quote:


  Originally Posted by *wistily* 
_Newb question: how do you do the holes in the thick aluminium ? I have tried with a dremel with no success. What's the magic trick, especially for big things like the iec inlet, or the neutrik ?_

 

I use stepped drill bits for the larger holes....I have 3 different ones for different hole diameters up to 1 1/4". For rectangular holes, I use files to remove the corners after drilling the center as large as possible. The stepped drill bits are available at most hardware stores, but you can save some money on Ebay where you will find a large variety for sale.


----------



## DigiPete

Quote:


  Originally Posted by *Magsy* 
_I've been spending most of my time finalising the panel, I thought I'd come back to finding a jack later (which is going to be a mistake!)

 I couldn't find anything off hand, I already have those neutrik jacks though. The nut is way to big for the look I want, the thread is big and plastic too, I'm not sure a 4mm panel will hold it nicely without the front nut?

 I'll have a look when I get home...

PDF 90kb

 My panel is looking like this at the moment, almost done. Had to move the pot holes inward which I didn't like but they won't fit the case other wise. I know the 'h' in headphone should be uppercase, its on my list.. 

 Sorry its a PDF but it looks terrible as a raster (jpg etc)_

 


 Hi Magsy,

 Nice design for your panels! Could you share what font you used for your lettering? Is it one of the standard Windows fonts?

 Thanks
 DigiPete


----------



## Magsy

ygpm


----------



## Akku

I cased the amp. No more buzz or hum. It's so silent I though it was broken 
	

	
	
		
		

		
		
	


	




 I'd like to post pictures but I have no digital camera. It is a standard M3 anyway. The minor differences are the fixed BB, crossfed (Tangent board) with rotary switch in the back along with stepped att. and shaft extensions to the knob on the panel.
 Maybe I must ask a friend to lend me a camera, I am so proud


----------



## skyskraper

stingray


----------



## amb

Quote:


  Originally Posted by *Akku* 
_I cased the amp. No more buzz or hum. It's so silent I though it was broken 
	

	
	
		
		

		
			



_

 

Great!


----------



## Akku

Yes, even with low impedence cans (MDR-V6) at full volume I can barely hear just a distant "somenthing" (thermal noise?). I though about lowering R1 (the att. is 10k) but with the actual performance I guess it is useless 'cause source noise is predominant anyway.


----------



## Jaypetermen

Quote:


  Originally Posted by *amb* 
_The TREAD's power transformer is off-board, so you aren't restricted to the Amveco 15VA or 25VA sizes that the STEPS board could accommodate. You could use a 50VA or larger transformer._

 

If I opted to go with the STEPS with a Amveco 25VA instead of the TREAD's, would the Digi-key P/N TE70063-ND be the correct transformer?

  Quote:


  Originally Posted by *amb* 
_With the beefed up power supply, the M³ board's C7 rail capacitance may be increased to about 6000uF._

 

I was planning on using six of the ELNA Cerafine 470uf/35V caps for C7. To increase C7 rail capacitance to 6000uF, would I just use six of the ELNA Cerafine 1000uf/35V caps?

 Will the larger caps or any of the other speaker driving options decrease the amp's headphone mode performance?

  Quote:


  Originally Posted by *amb* 
_ I also recommend using a LT1085 or LM1085 3A regulator, along with TO-220 style Schottky rectifier diodes,…_

 

I will replace the STEP’s LM317TNS with a LT1085CT-ND.

 On the Tangentsoft web site it states that “The downside of these LDO regulators is that they are sensitive to the impedance on their output." Do I need to be concerned with this if I increase C7 rail capacitance to 6000uF?

 TO-220 style Schottky rectifier diodes. Does anyone have a Mouser or Digi-Key P/N for this part? 
	

	
	
		
		

		
		
	


	




 I realize that these questions maybe fundamental, I just want to confirm before proceeding.

 Let’s see what else, replace the M³’s D1 with a 1N5401 and add speaker binding posts.


----------



## steinchen

an LDO regulator isn't a good idea when you're going to push the rail capacitance that high

 suitable 15VA transformers for steps are:
 +/-15V 15VA digikey # 70053
 +/-12V 15VA digikey # 70052

 TO-220 style Schottky rectifier diodes:
 MUR 820 digikey # MUR820IR, mouser # 625-FES8DT
 up to ... MUR 860
 10TQ035 digikey # 10TQ035
 HFA 08TB60 digikey # HFA08TB60-ND


----------



## Jaypetermen

Quote:


  Originally Posted by *steinchen* 
_an LDO regulator isn't a good idea when you're going to push the rail capacitance that high_

 

If a LDO is out. What regulator will work?
  Quote:


 suitable 15VA transformers for steps are:
 +/-15V 15VA digikey # 70053
 +/-12V 15VA digikey # 70052 
 

Does the STEPS board support a Amveco 25VA transformer?


----------



## steinchen

Quote:


  Originally Posted by *Jaypetermen* 
_If a LDO is out. What regulator will work?_

 

if you don't want to stick with a LM317T or LM317A you may pick the LM338

  Quote:


  Originally Posted by *Jaypetermen* 
_Does the STEPS board support a Amveco 25VA transformer?_

 

the STEPS PCBs work with either 15VA and 25VA transformers (5 through 25VA to be exactly)

 I recommend to take a look at tangent's part selection guide


----------



## amb

Quote:


  Originally Posted by *Jaypeterman* 
_Will the larger caps or any of the other speaker driving options decrease the amp's headphone mode performance?_

 

No, but if you have low impedance headphones then you may have a gain conflict. For speaker use, the gain should be on the high side (the default of 11x is good), but that might be a bit much for some low-Z headphones. Your usable volume control knob range will be small with such phones.

 For speaker use, go with as large a power transformer as you could fit. The higher VA ratings will provide the current and voltage demands. Also, I now recommend the LM338T for the regulator if you use the amp with speakers.


----------



## Jaypetermen

Quote:


  Originally Posted by *steinchen* 
_the STEPS PCBs work with either 15VA and 25VA transformers (5 through 25VA to be exactly)

 I recommend to take a look at tangent's part selection guide_

 

Digi-key offers no less then six Amveco 25VA transformers in this series. They have different values for the following: Sec-Full Load V, Current mA, No Load Voltage. I do not know which one of the six transformers to use.


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_Digi-key offers no less then six Amveco 25VA transformers in this series. They have different values for the following: Sec-Full Load V, Current mA, No Load Voltage. I do not know which one of the six transformers to use._

 

What is your target PSU output voltage? It can't be more than about 26V if you use AD8610 or AD8065, but could be up to 36V or higher depending on which other opamps you choose (see my M³ site, under "power supply"). Your capacitors' voltage rating has to be high enough (plus some headroom) for your choice of voltage. So 35V cerafines won't do for 36V+.


----------



## Jaypetermen

Quote:


  Originally Posted by *amb* 
_So 35V cerafines won't do for 36V+._

 

Would six of the Nichicon Ultra-Low Impedance Electrolytic Capacitor, 1000uf/63V, 18mm x 31mm be a good choice?


----------



## BrokenEnglish

Quote:


  Originally Posted by *Jaypetermen* 
_Would six of the Nichicon Ultra-Low Impedance Electrolytic Capacitor, 1000uf/63V, 18mm x 31mm be a good choice?_

 

yeah... they'd do the job. but be aware, that you'd have to solder some of them off-board with the STEPS (place for 4 caps) or the TREAD (place for 1 cap). also... 4000µf would be a sufficient solution.


----------



## Jaypetermen

Quote:


  Originally Posted by *BrokenEnglish* 
_yeah... they'd do the job. but be aware, that you'd have to solder some of them off-board with the STEPS (place for 4 caps) ...._

 

Okay, I thought I was putting the six 1000uf/63V Nichicon Ultra-Low Impedance Electrolytic Capacitor in the M³, to increase the C7 rail capacitance to 6000uF?
  Quote:


  Originally Posted by *amb* 
_What is your target PSU output voltage?_

 

36V+ with OPA637AP & OPA627AP configuration. Just need to find some already soldered on Browndog boards.
  Quote:


  Originally Posted by *amb* 
_…if you have low impedance headphones then you may have a gain conflict._

 

I currently only have a pair of Sennheiser HD650s and PX-100s. I am interested in a pair of Beyerdynamic DT 880s in the future.

 One more try and I am going back to building the stock M³.

 STEPS upgrades:
 -Transformer to a Amveco 25VA to product 36V+ (need P/N)
 -IC1 regulator to a LM338T, Digi-key P/N: LM338T-ND

 M³ upgrades:
 -D1 to a DO-41 5A Rectifier, Mouser P/N: 512-1N5401
 -TO-220 style Schottky rectifier diodes, Mouser P/N: 625-FES8DT
 -OPA637AP & OPA627AP configuration on Browndog boards
 -C7 to six 1000uf/63V Nichicon Ultra-Low Impedance Electrolytic Capacitor, Welborne Labs, P/N: NICH21
 -Speaker binding posts (need P/N)


----------



## skyskraper

with the m3 power rail caps, u might find a larger range of different values if you look to the panasonic fc and fm range seeing as it looks like you're ordering from mouser. 

 not sure what the lm338t max output voltage is (looks like 32v) but iirc the 317 max's out at 35v so you probably wont hit 36+v using the steps using the lm338t. im getting about 32v from my lm317 based tread, i have a 12 0 0 12 30va transformer. i would say that a 12 0 0 12, 25va amveco (check the catalog for a part number) would be about right to give you say up to 32v.

 also why do you want to use smd opa627's? why not simply get the dip package and not have to worry about adaptors and the like.


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_STEPS upgrades:
 -Transformer to a Amveco 25VA to product 36V+ (need P/N)
 -IC1 regulator to a LM338T, Digi-key P/N: LM338T-ND_

 

I suggest the Amveco TE70063. Adjust your STEPS to output 36V DC.

  Quote:


 M³ upgrades:
 -D1 to a DO-41 5A Rectifier, Mouser P/N: 512-1N5401
 -TO-220 style Schottky rectifier diodes, Mouser P/N: 625-FES8DT
 -OPA637AP & OPA627AP configuration on Browndog boards
 -C7 to six 1000uf/63V Nichicon Ultra-Low Impedance Electrolytic Capacitor, Welborne Labs, P/N: NICH21
 -Speaker binding posts (need P/N) 
 

OPA637AP and OPA627AP are already in DIP8 packages, no need for browndog adapters.

 C7, use six Nichicon HE series low ESR 1000uF 50V (Mouser 647-UHE1H102MHD) to get 6000uF.

 Binding posts, use Pomona 3750 (Mouser 565-3750-0 black, 565-3750-2 red)

  Quote:


  Originally Posted by *skyskraper* 
_not sure what the lm338t max output voltage is (looks like 32v) but iirc the 317 max's out at 35v so you probably wont hit 36+v using the steps using the lm338t. im getting about 32v from my lm317 based tread, i have a 12 0 0 12 30va transformer. i would say that a 12 0 0 12, 25va amveco (check the catalog for a part number) would be about right to give you say up to 32v._

 

The LM338 will happily output 36V if the input voltage is a few volts higher, and the voltage adjustment resistor values are chosen approproately. See tangent's STEPS site for details.

 The 12V dual secondary transformer is too low for 36V output. Use the dual 15V one as I specified above. The dual 18V transformer would probably make the LM338 run too hot.


----------



## skyskraper

cool, i just got a bit confused reading the datasheet of it 
	

	
	
		
		

		
		
	


	




 agreed with the transformer choice for 36v too. so prease ignore what i said about transformer for the regulator


----------



## Jaypetermen

How will this headphone/speaker based amp pair with the Sennheiser HD 650 and the Beyerdynamic DT 880?

  Quote:


  Originally Posted by *amb* 
_C7, use six Nichicon HE series low ESR 1000uF 50V (Mouser 647-UHE1H102MHD) to get 6000uF._

 

Will the 647-UHE1H102MHD3 (18mm x 20mm) fit in the larger C7 footprint?


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_How will this headphone/speaker based amp pair with the Sennheiser HD 650 and the Beyerdynamic DT 880?_

 

Should be just fine.

  Quote:


 Will the 647-UHE1H102MHD3 (18mm x 20mm) fit in the larger C7 footprint? 
 

Yes, it will fit, but the *MHD has slightly better ESR and ripple specs than the *MHD3. They are the same price at Mouser.


----------



## CPL593H

I'm waiting for the M3 board and the STEPS PS board to arrive and putting together the parts order. Has anyone used the Nichicon KZ caps for C7 or C5 on the M3? Any recomendations? 
 I've never used "audiophile grade" electrolytic caps in any of my tube amps because at high voltages they are always way too expensive. At 50 volts the boutique caps are more interesting.

 HD600's and NAD 502 CD.

 Dave


----------



## MisterX

Quote:


 Has anyone used the Nichicon KZ caps for C7 or C5 on the M3? 
 

Can't use them for for C4/C5 cause they won't fit. 
 (the leads are to big for the holes)


----------



## rjkdivin

I just completed another M3 build using the Par Metals group buy Option A cases. For the PS in this one I used the Welborne Labs PS-1 instead of the STEPS. It is just slightly larger than the STEPS with an off pcb transformer, but fits very nicely, and runs considerably cooler than the STEPS. The PS-1 is a dual rail PS with separate regulators and heat sinks for + and - rails, and can be set up for different output voltages. I set mine at +12v plus -12v, and do not use the ground at all. Again, the M3 is awsome!!


----------



## rjkdivin

By the way, the PS-1 does not come with provision for a power LED, so I a added an LED and resistor in series across the + and - rails to get matching LEDs on the M3 and PS-1 cases.


----------



## Jaypetermen

rjkdivin, nice work.


 Are my two best options for the M³'s D1 the DO-41 5A Rectifier, Mouser P/N: 512-1N5401 or the TO-220 style Schottky rectifier diode, Mouser P/N: 625-FES8DT?

 If so, which one would be the easiest to incorporate?


----------



## DigiPete

Quote:


  Originally Posted by *CPL593H* 
_I'm waiting for the M3 board and the STEPS PS board to arrive and putting together the parts order. Has anyone used the Nichicon KZ caps for C7 or C5 on the M3? Any recomendations? 
 I've never used "audiophile grade" electrolytic caps in any of my tube amps because at high voltages they are always way too expensive. At 50 volts the boutique caps are more interesting.

 HD600's and NAD 502 CD.

 Dave_

 

I used the KZs for C7 on my M³.

 DigiPete


----------



## CPL593H

Quote:


  Originally Posted by *MisterX* 
_Can't use them for for C4/C5 cause they won't fit. 
 (the leads are to big for the holes)_

 

 I appreciate your answer. I bought a set of wire size drill bits when I built my power amps because some of the leads didn't fit the holes. Is is a really huge difference or just a tweek on the hole size as I have the tiny drills to open the holes up a litte.

 Dave


----------



## MisterX

Looks like I was wrong.... cause once you cut the very ends of the leads off they will fit through the holes.

 (I tried it with 100uF/25vdc and 200uF/25vdc KZ series)


----------



## amb

Quote:


  Originally Posted by *CPL593H* 
_I appreciate your answer. I bought a set of wire size drill bits when I built my power amps because some of the leads didn't fit the holes. Is is a really huge difference or just a tweek on the hole size as I have the tiny drills to open the holes up a litte._

 

Don't drill the pcb holes, because they are plated-through and in some cases are the connection between the top and bottom layers. If you drill them will you break that connection.


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_Are my two best options for the M³'s D1 the DO-41 5A Rectifier, Mouser P/N: 512-1N5401 or the TO-220 style Schottky rectifier diode, Mouser P/N: 625-FES8DT?
 If so, which one would be the easiest to incorporate?_

 

They both require a little lead-bending to fit the holes, nothing major. The FES8DT is rated considerably higher at 8A than the 1N5401 (3A), but both will work fine.


----------



## rjkdivin

Quote:


  Originally Posted by *amb* 
_Don't drill the pcb holes, because they are plated-through and in some cases are the connection between the top and bottom layers. If you drill them will you break that connection._

 

To elaborate on AMBs answer a bit, drilling out the through hole plating will also weaken the mechanical connection to the pcb because it removes the 'anchor' for the solder pad.....this could be a real concern with large caps.


----------



## CPL593H

Thanks for the no-drill warning. I've never worked with a double-sided plated through board and could have made a big mistake. I went back and read a lot of historical posts on capacitors and think that I should just buy the recomended Panasonic or Nichicon's from Mouser or Digikey.

 dk


----------



## funch

I'm considering building an M3, but would like to integrate a Hagerman Bugle phono pre into the same case (w/input switching), and run both off of the same P/S to save space/$. Is this possible, or am I nutz to even consider it? Since Welborne Labs is having a 20%-off sale on their PS-1, I was thinking of using it at +/- 12v. I would be using the AD8065/66 for both amps. I would have to use just the +/- leads for the M3, and all 3 leads (w/ground) for the Bugle. Or I could use a 24v P/S, and add a TLE rail splitter to the Bugle (it needs a +/- P/S). Also, the Bugle draws about 100 mA.

 Any thoughts would be appreciated.


----------



## skyskraper

what i would want to do integrating the bugle like that is to install the tle on the m3 but dont cut the lead's off the bottom, then simply tap the tle so the rails of the m3 and the bugle are at the same place and you wouldnt need to worry about modifying the hagtech pcb.


----------



## amb

funch, skyskraper's suggestion is good. You can use the V+ and V- leads from your PSU, and take the virtual ground (IG on the M³ board) to power your Hagerman Bugle phono board. Leave the Welborne PS1's ground unconnected.

 Looking at the Bugle schematic, it does not source or sink significant current from the virtual ground so the TLE2426 on the M³ board will have no problem with the additional "load". Moreover, the Bugle consists of three OPA2130 dual opamps. These opamps are very low current devices (~530uA per amplifier), so in total it adds only about 3.5mA to the total current draw on the PSU, which is essentially nothing. Even if you change to use AD8066s on the Bugle, the additional current draw is only ~6.6mA * 6 = 40mA. The Welborne PS1 should have no trouble powering both the M³ and the Bugle.


----------



## skyskraper

let us know how it goes if u decide to do it. ive been meaning to try out a bugle for a while but have just never gotten round to it, but there's plenty of space in my mmm case


----------



## en480c4

I know there have been lots of questions of which to build... the M^3 or PPAv2. I just thought I'd let you guys know Nate (n_maher) and his M^3 sat down w/ me and my PPAv2... 

 Here is the summary of my thoughts.... Nate's will follow later this week.
http://www6.head-fi.org/forums/showthread.php?p=1393626


----------



## funch

Thanks amb and skyskraper for the idea. That sounds like a winner, and would simplifiy things a bunch.


----------



## funch

Oops! I just thought of another potential problem with my M3/Bugle idea. My tonearm is a Rega with the Incognito rewire kit. It has a separate ground wire. Don't I need a true ground off of the Bugle board to connect that ground wire to? The virtual ground won't work as a ground connection for the tonearm, right? Or am I off base (not completely out of the realm of possibility 
	

	
	
		
		

		
		
	


	




 ). Or can I use chassis (input) ground?


----------



## amb

funch, the virtual ground is as "real" as anything as far as your tone arm ground is concerned. There should be no problem connecting it that way. Also, the virtual ground _is_ input/chassis ground in two of my recommended internal wiring schemes (see the wiring & ground section of my M³ site).


----------



## funch

amb, Ok, thanks.


----------



## amb

Hi all, if you have completed your M³ amp, and it is not yet featured in the gallery section of the M³ site, what are you waiting for? 
	

	
	
		
		

		
		
	


	




 PM me and I'll provide details on how to upload your pics.


----------



## Jaypetermen

Quote:


  Originally Posted by *amb* 
_They both require a little lead-bending to fit the holes, nothing major. The FES8DT is rated considerably higher at 8A than the 1N5401 (3A), but both will work fine._

 

I already purchased the AD8610AR Op-amps.

 Will the STEPS PS run at 24VDC okay with the Amveco TE70063 Transformer and LM338T IC1 regulator?

 and will the M3 run okay with TO-220 style Schottky rectifier diodes, AD8610AR op-amps and six Nichicon HE series low ESR 1000uF 50V for C7 only receiving 24DVC?


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_Will the STEPS PS run at 24VDC okay with the Amveco TE70063 Transformer and LM338T IC1 regulator?_

 

The regulator will get too hot. Best to use the TE70062 transformer for 24V - 27VDC output. You can safely run the AD8610ARs at 27V because the M³'s D1 and capacitance multiplier will drop that voltage down a bit.

  Quote:


 and will the M3 run okay with TO-220 style Schottky rectifier diodes, AD8610AR op-amps and six Nichicon HE series low ESR 1000uF 50V for C7 only receiving 24DVC? 
 

Yes.


----------



## wistily

Newb question: in some M3, i see two headphone out. Does it mean than it order to have the same on my model, i just need to solder two headphones out in parallel ? Will it draw more current ? Will there be a limitation of some type ?

 ps: don't worry amb, when my M3 will be cased up, i will give you details and pictures for your site


----------



## skyskraper

there are dual output pads for this exact reason


----------



## amb

Quote:


  Originally Posted by *wistily* 
_Newb question: in some M3, i see two headphone out. Does it mean than it order to have the same on my model, i just need to solder two headphones out in parallel ? Will it draw more current ? Will there be a limitation of some type ?_

 

You can use the dual output pads and wire each jack separately as skyskraper says, or you could daisy chain from one jack to another. Either way is fine. There is no problem driving multiple headphones in parallel, the MOSFET output stage of the M³ will deliver all the current required.


----------



## CPL593H

What should I set the gain at on the M3 I'm building. I'll be using a home system CD source like my NAD502 or a Sony SACD player. The phones will be Sennheiser HD600s. Should I use the default gain of 11 or back off some? thanks


----------



## skyskraper

i found a gain of 7.5 to be just short of what i need. a gain of 11 should be fine


----------



## DigiPete

Quote:


  Originally Posted by *CPL593H* 
_What should I set the gain at on the M3 I'm building. I'll be using a home system CD source like my NAD502 or a Sony SACD player. The phones will be Sennheiser HD600s. Should I use the default gain of 11 or back off some? thanks_

 

I found that the gain of 11 works well, because some SACDs are recorded at low levels, and I had to crank the volume pot up to about 70% (with my DT880s).


----------



## Jaypetermen

Quote:


  Originally Posted by *CPL593H* 
_What should I set the gain at on the M3 I'm building._

 

How do you adjust or set the gain to 11 on this amp?


----------



## DigiPete

Quote:


  Originally Posted by *Jaypetermen* 
_How do you adjust or set the gain to 11 on this amp?_

 

from Amb's website on the M³:

 Notes about R3 and R4 

 The voltage gain of the amplifier is determined by the ratio of R4L and R3L (as well as R4R and R3R). The default values of these are 10KΩ and 1KΩ, respectively, for a gain of 11. This is usable with most headphones, although it might be a little high for the most sensitive low-impedance types. 

 The gain may be reduced to suit such headphones. Further, the gain may also need changing depending on whether the amplifier is to be used with computer/portable devices or home stereo. The latter typically have a higher "line out", requiring less gain in the headphone amplifier. 

 The gain is computed by the formula: 
 G = (R4 / R3) + 1


----------



## Jaypetermen

Quote:


  Originally Posted by *DigiPete* 
_from Amb's website on the M³:_

 

Thank you, found it on Amb's website under 'Parts List', 'Resistors', 'Notes about R3 and R4.'


----------



## DigiPete

Question:

 I have been reading about the praises of the AD797ANZ and the Supermacro V3. Also been reading good things about the OPA604.

 Will these op amps roll into the M³, at least from a functional standpoint, to allow comparisons?

 Any arguments pro or against?

 Thanks
 DigiPete


----------



## amb

See my M³ site (under Parts list) for a list of tested opamps. The OPA604 is among them. I do not recommend using the AD797 here because it is not FET-input and has high input bias current. In the M³ there are no coupling capacitors, so the output DC offset voltage will be high, and will vary with the volume control setting.


----------



## DigiPete

Quote:


  Originally Posted by *amb* 
_See my M³ site (under Parts list) for a list of tested opamps. The OPA604 is among them. I do not recommend using the AD797 here because it is not FET-input and has high input bias current. In the M³ there are no coupling capacitors, so the output DC offset voltage will be high, and will vary with the volume control setting._

 

Amb,

 Got it thanks. Not being an E.E. (only an M.E.) it helps to have opinions from people who actually understand the circuits.

 Thanks much!
 DigiPete


----------



## steinchen

opa604 ... hm ... power supply voltage up to +-25V 
	

	
	
		
		

		
		
	


	




 how does this opamp sound ? Can anybody give a short discription of its sonical character ?

 where is the voltage limit of the M³ ? Caps 63V (electrolytic), tle2426 40V, opa604 50V, 2n3904 40V -> with a little safety margin of 2 or 3 Volts -> 38V max ?


----------



## CPL593H

Any suggestions for cutting the IEC AC power entry module holes in an aluminum box? I've got a drill press and roto zip. Both seem like crude tools for the task. 

 Has anyone used the Par Metal box and had Par machine the chassis holes? Was it affordable in the context of a $300 project?


----------



## skyskraper

draw outline of iec with pencil, drill inside the outline, then use something like a dremel to cut it to a proper square/rectangle. takes some time but the results are good, and its not too difficult.


----------



## amb

Quote:


  Originally Posted by *steinchen* 
_opa604 ... hm ... power supply voltage up to +-25V 
	

	
	
		
		

		
		
	


	


_

 

Yup! If you want a lot of voltage swing this is the opamp to use in M³.

  Quote:


 how does this opamp sound ? Can anybody give a short discription of its sonical character ? 
 

I'll let others do that, but during my short listen there wasn't anything glaringly bad about it. In fact it was quite good. This opamp is interesting in that all active amplification transistors inside are JFETs, and is the opamp used in most good NAD CD players.

  Quote:


 where is the voltage limit of the M³ ? Caps 63V (electrolytic), tle2426 40V, opa604 50V, 2n3904 40V -> with a little safety margin of 2 or 3 Volts -> 38V max ? 
 

The 2N3904 bias transistor will never see the full rail, so that's of no concern. The MOSFETs are rated at 55V so it's ok, if you use 50V electrolytic caps then that's fine too. The TLE2426 is the "bottleneck" at 40V. Since the capacitance multiplier transistors and D1 cause a drop of another 2.5V or so, there is already a built-in safety margin and thus 40V is a good max PSU voltage. If you use a real split PSU and omit the TLE2426, then you could go further up to 48V if you have 50V rail capacitors.


----------



## Ob3ron

Hey i've got a few newbie questions regarding the wiring/grounding...

 a) I'm going with AMB's wiring scheme 1 and am wondering how I might go about connecting the pot to my parmetals chassis if i've placed the board too far back to actually screw the pot shaft's nut onto the front panel. Would connecting the pot's ground screw to the input ground suffice since input ground will be connected to the case via the input jacks?

 b) For a power switch, I've got an SPDT that says its rated for 6A 125V (I'm running a headphone MMM so that should be fine). Can I just put it inline with the AC live wire (one side going to the middle prong, the other going to the top or bottom)? 

 c) I'm making a dual input MMM and I've got a DPDT switch for input selection. I read in some thread (can't seem to find it now), that in theory it's not the best idea to have my two sources' grounds connected as are by using a DPDT, but practically, I shouldn't have any problems. Is this correct?

 Thanks


----------



## amb

Quote:


  Originally Posted by *Ob3ron* 
_Would connecting the pot's ground screw to the input ground suffice since input ground will be connected to the case via the input jacks?_

 

Yes. That's fine.

  Quote:


 Can I just put it inline with the AC live wire (one side going to the middle prong, the other going to the top or bottom)? 
 

If by "prong" you mean the solder tabs of the switch, then yes. Use heat-shrink to insulate the wires afterwards so that no high voltage is exposed.

  Quote:


 c) I'm making a dual input MMM and I've got a DPDT switch for input selection. I read in some thread (can't seem to find it now), that in theory it's not the best idea to have my two sources' grounds connected as are by using a DPDT, but practically, I shouldn't have any problems. Is this correct? 
 

There is no problem connecting the grounds of the two sources together and only switch the signals. That's how most preamps do it.


----------



## Jaypetermen

I am about to start building a M3 & STEPs. I currently have the AD8610AR op-amps (which are rated up to 27VDC) and I am also thinking about building a Millit-Hybrid, since I could not resist the group buy.

 I would like to configure the STEPs to be able to power both amps (one at a time of course) without changing the voltage. Would 27VDC be a good setpoint for both of the stock amps?


----------



## n_maher

Yes, your STEPS set up to output 27V will work just fine for the Millett and the M³. I've run the exact setup (well 26.5V) on both and neither has suffered one bit. Somewhere in this thread AMB describes the voltage drops that you get during the circuit of the M3 so that 27V is actually safe for the 8610s since they see at least 1V less at the chip.

 HTH,

 Nate


----------



## rjkdivin

Quote:


  Originally Posted by *Jaypetermen* 
_I would like to configure the STEPs to be able to power both amps (one at a time of course) without changing the voltage. Would 27VDC be a good setpoint for both of the stock amps?_

 

I'm not recommending anyone actually do this on purpose, but I can say from experience that the AD8610 can handle some excess voltage. When I was having a problem blowing the regulators on my STEPS due to current spikes, the voltage to the M3 would jump up to about 30v after the regulator blew (using a 15v + 15v transformer). I didn't attempt to run it that way, but the AD8610s did survive until I powered off. On the other hand, when I did the same thing with a 24v + 24v transformer, the voltage would climb to about 48v after the PS regulator blew, and the AD8610s did not survive. One of them actually blew its top off.


----------



## amb

Q5+, Q5- and D1 will each drop some voltage (totalling about 2.5V), so if you use a 27V PSU, the actual voltage "seen" by the opamp will be about 24.5V so all will be well with the AD8610.


----------



## Ob3ron

I'm trying to figure out the best way to mount the neutrik locking jack to the front of the Parmetals group buy case... I realize i could buy a 22mm (0.945") drill bit but that's probably gonna set me back 15-20 bucks. I bought a dremel with 70+ accessories last weekend so I'm wondering if theres any way I can use that to make the hole.

 EDIT: Okay, nevermind. 

  Quote:


 larger stuff like iec inlets and 20mm+ holes you can also get punche's that will do the trick i just got a 25mm punch for my neutrik combo jacks, it wasnt too pricey at all, a lot cheaper then the equivalent drill bit. have yet to run it though so i can't tell you what the results are like yet. 
 

-skyscraper

  Quote:


 I use stepped drill bits for the larger holes....I have 3 different ones for different hole diameters up to 1 1/4". For rectangular holes, I use files to remove the corners after drilling the center as large as possible. The stepped drill bits are available at most hardware stores, but you can save some money on Ebay where you will find a large variety for sale. 
 

-rjkdivin

 I'll look into these.


----------



## skyskraper

go the punch 
	

	
	
		
		

		
		
	


	




 cutting big holes with slow high torque (ie: twisting a pair of wrenches on a punch) is a lot more controlled then high speed drill bits that are temperamental at the best of times. havent installed my combo's on my m3 yet, but played round with cutting AL and the punch works nicely. i found the cost of my 25mm hand punch was significantly less then a decent quality 25mm drill bit/hole saw.


----------



## CPL593H

Where's a good place to buy punches online? 
 thanks

 ___________________

 Don't get your hair on fire.


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## skyskraper

i believe in the USA digikey or mouse carry them. past that there's ebay. i got mine from RS components in oz when i was picking up some other parts, but id reccomend calling b2b tool suppliers in your area. heaps in perth, west aust, had them in stock for around the same price as i paid at RS.


----------



## CPL593H

I'm pretty excited to see a service like Front Panel Express. This could make the M3 project a lot easier and the final product look a lot better. Are there any M3 photos that use a panel from this service on the site?


----------



## n_maher

Check the M3 gallery at amb's site here and look at steinchen's beautiful M3 w/ a panel by FPE. Be warned though, they are not cheap.

 HTH,

 Nate


----------



## thrice

I've got an M cubed hooked up with Solen fast caps in the C6 position (tombstoned to make room) and the results are quite nice...smoother sound overall from the wimas (it's a subtle difference though)

 Just thought I'd throw that out there.
 thrice


----------



## SDA

My M³ is all set up, but not working properly... for some reason, with a WM080 plugged in (all I have until I finish my STEPS, unfortunately), voltage between pins 4 and 7 of each opamp socket is .5V, and it shows (the LED's emitter barely glows). Resistance between pins 4 and 7 is four point something mega-ohms. What could be causing this?


----------



## skyskraper

what voltage do you get across the -+ voltage input pins? what about between the in and out and the out and common pins of the TLE?


----------



## SDA

+- pins: 2.2xV.

 in and com: about .5V, same as between pins 4 and 7 of opamps.

 com and out: about .25V.

 It seems like the amp is just working as it would if it were fed 2.2xV or so, but I know this WM080 puts out a little over 24V with an open circuit. Could the M³ be stressing the thing THAT much?


----------



## n_maher

Have you double checked the elpac to see if it is, in fact, putting out 24V? If it is start working your way down the power supply section of the amp checking voltages as you go, you might find the fault there. If your LED is barely lighting something is definitely not right.

 You also might start a new thread and post some pictures of the amp to see if someone can find something you've overlooked.

 Nate


----------



## wistily

Do you use an external power supply with a power jack ? I had similars problems with my m3, and i found out, that i had soldered the female jack incorrectly: there were three pins on it, and i soldered the minus on the wrong "ground" (i still don't undestand why there are three pins on these connectors and what does the third pin).


----------



## skyskraper

can you measure across the +- points of your dc input jack. and also maybe try a continuity check to make sure your dc jack is isolated from the case (blind leading the blind with the second point 
	

	
	
		
		

		
			





 )


----------



## n_maher

Quote:


  Originally Posted by *wistily* 
_i still don't undestand why there are three pins on these connectors and what does the third pin._

 

Most likely what you have is a switched jack, it's designed to allow the use of 2 power supplies, like internal batteries and an external wall-wart. The jack "switches" between the two when you plug the wall-wart in. If it didn't disconnect the other power source you'd have big issues unless you opened your amp and disco'd the batteries each time you plugged in the wall-wart. For your case one of the ground terminals will just be left empty since you have a single power supply.

 HTH,

 Nate


----------



## SDA

Quote:


 Have you double checked the elpac to see if it is, in fact, putting out 24V? If it is start working your way down the power supply section of the amp checking voltages as you go, you might find the fault there. If your LED is barely lighting something is definitely not right.

 You also might start a new thread and post some pictures of the amp to see if someone can find something you've overlooked. 
 

Thing is, the only voltages that I know would be V+ to V- and either of those to ground, and measuring those anywhere just tells me that the voltage is really low and that the TLE is splitting the tiny voltage it gets pretty well. Where should I start measuring (all I've confirmed so far is the Elpac with an open circuit and D1, which has a ~0.7V drop), and what values should I look for?

 I can try to borrow my friend's camera again later today. Should I take pictures of the top or the bottom, or both?


  Quote:


 Do you use an external power supply with a power jack ? I had similars problems with my m3, and i found out, that i had soldered the female jack incorrectly: there were three pins on it, and i soldered the minus on the wrong "ground" (i still don't undestand why there are three pins on these connectors and what does the third pin). 
 

I thought that might have been it, but when I disconnected the molex connector I found that the voltage between where I had connected V+ and V- was what it was supposed to be.


  Quote:


  Originally Posted by *skyskraper* 
_can you measure across the +- points of your dc input jack. and also maybe try a continuity check to make sure your dc jack is isolated from the case (blind leading the blind with the second point 
	

	
	
		
		

		
		
	


	




 )_

 

24 volts and change until I connect it to the board. Then it drops to the voltages measured earlier. Also, there, uh, is no case right now.. I decided to test it in the open first to see if it worked.


----------



## skyskraper

do you have a spare d1 that you could possibly swap in ?


----------



## SDA

No, but I could take one from a simply CMoy-type amp I've made. It doesn't seem like D1 is defective, though.. if it were, how would it cause this?


----------



## skyskraper

i make the suggestion sheerly because at the input from the power pack the voltage seems fine then the next component in the chain is the diode. its the only component before the led, makes sense to be a possible culprit.


----------



## SDA

Damn, new known-good (worked in the CMoy) D1 makes no difference.

 Looking at the schematic, the problem seems like it would most likely be in that section of the power supply with Q5+/- and Q6+/-, just because there's more to be screwed up there. How do I test the individual diodes there?


----------



## skyskraper

ooh is it possible that c7 is dead and the power is just flowing between its former position?

 q5 you should be able to test with the info here, i have yet to need to test a FET for functionality though so q6 i couldnt give you a definite direction on sorry.


----------



## rjkdivin

Quote:


  Originally Posted by *SDA* 
_Damn, new known-good (worked in the CMoy) D1 makes no difference.

 Looking at the schematic, the problem seems like it would most likely be in that section of the power supply with Q5+/- and Q6+/-, just because there's more to be screwed up there. How do I test the individual diodes there?_

 

A couple more suggestions:
 Make sure you are plugging the power supply into the M3 before you plug the PS into the mains. The M3 draws a very large current to charge the rail capacitors when it starts up. If the PS is fully powered before the M3 it is subjected to a substantial current spike and you could be tripping any protective circuitry it has.

 Also, double check the orientation of D1, although it sounds like you have done that if you have pulled it a couple of times.

 Finally, double check the identification of your Q1+ and Q1- mosfets to be sure you have not reversed theme with each other. I did this with one pair on one of my M3s and ended up frying an R9 resistor.


----------



## amb

Quote:


  Originally Posted by *rjkdivin* 
_Finally, double check the identification of your Q1+ and Q1- mosfets to be sure you have not reversed theme with each other. I did this with one pair on one of my M3s and ended up frying an R9 resistor._

 

Yes, the N-channel and P-channel MOSFETs have internal reverse diodes (see datasheet) from the source pin to the drain pin. If you had installed one or more pairs of these MOSFETs wrongly, then the diodes will basically present theselves as a crowbar short circuit to the PSU through the R9 resistors. Read the face of the MOSFETs carefully to make sure you installed IRFZ24N in the Q1+ positions and IRF9Z34N in the Q1- positions.


----------



## Jaypetermen

I have the 100uF 50V Aluminum Cap Nichicon UPW caps for C4 & C5. 

 However I would like to use a bouquet cap in these positions. I originally was planning on using the 100uf/35V ELNA Cerafine but the supplier is currently out of stock.

 Currently, I have found the following potential alternatives:

 -100uF/25vdc, Nichicon Muse KZ, 10.0 x 16.0
 -100uF/25vdc, RFS Silmic II Series, 10.0 x 18.0
 -330uF/50vdc, Nichicon Muse KZ, 16.0 x 31.5

 At these prices I want to insure they will work for my configuration. I am planning on running a STEPs at 27VDC. AMB noted that;

  Quote:


  Originally Posted by *amb* 
_Q5+, Q5- and D1 will each drop some voltage (totalling about 2.5V), so if you use a 27V PSU, the actual voltage "seen" by the opamp will be about 24.5V so all will be well with the AD8610._

 

Will the 100uF/25vdc Nichicon Muse KZ and 100uF/25vdc RFS Silmic II Series run at there limits at 24V?

 Will the 330uF/50vdc, Nichicon Muse KZ, 16.0 x 31.5 fit and is the capacitance to high?

 Any other capacitor options or known supplier for the ELNA Cerafine?


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_Will the 100uF/25vdc Nichicon Muse KZ and 100uF/25vdc RFS Silmic II Series run at there limits at 24V?_

 

Yes, for C4 you would be running at its full rated voltage with almost no room to spare. I wouldn't feel comfortable with this, especially considering that electrolytic caps tend to fail by exploding 
	

	
	
		
		

		
		
	


	




 . For C5 they normally see half of that voltage, but if the TLE2426 should ever fail then it may also cause C5 to see the full voltage too.

  Quote:


 Will the 330uF/50vdc, Nichicon Muse KZ, 16.0 x 31.5 fit and is the capacitance to high? 
 

16mm is physically too large, and the increased capacitance is overkill. The circuit in effect multiplies the capacitance of C4 by the Hfe of the Q5 transistors, which results in a "virtual capacitance" of ~10000uF (assuming 100uF and Hfe of 100).


----------



## SDA

Quote:


 Finally, double check the identification of your Q1+ and Q1- mosfets to be sure you have not reversed theme with each other. I did this with one pair on one of my M3s and ended up frying an R9 resistor. 
 

 Quote:


 Yes, the N-channel and P-channel MOSFETs have internal reverse diodes (see datasheet) from the source pin to the drain pin. If you had installed one or more pairs of these MOSFETs wrongly, then the diodes will basically present theselves as a crowbar short circuit to the PSU through the R9 resistors. Read the face of the MOSFETs carefully to make sure you installed IRFZ24N in the Q1+ positions and IRF9Z34N in the Q1- positions. 
 

At first I thought I had them all installed correctly, then I realized I had 9Z34 and Z24 reversed for ALL channels 
	

	
	
		
		

		
		
	


	




 Thanks for your help, all of you... I probably shouldn't be allowed near a soldering iron 
	

	
	
		
		

		
		
	


	




 Err, unfortunately, there's one more thing. Setup of G and R channels seems to have gone well enough, but the voltage across R5L stays around 17mV no matter how I adjust BIASOPL. I'm guessing I have a short or something, where should I start looking?


----------



## amb

Quote:


  Originally Posted by *SDA* 
_Err, unfortunately, there's one more thing. Setup of G and R channels seems to have gone well enough, but the voltage across R5L stays around 17mV no matter how I adjust BIASOPL. I'm guessing I have a short or something, where should I start looking?_

 

Check your soldering for all parts near Q2L, Q3L and Q4L (verify connectivity with your DMM in ohms scale while the amp is powered off), and make sure all these are mounted in the correct orientation. If these all check out fine, then power up and measure the DC voltage at pin 6 of OPAMPL relative to IG. Also, measure the voltage between the collector and emitter pins of Q2L. What do you get for these?


----------



## SDA

Checked soldering work in that area, found some mess that might cause problems, cleaned it up and redid it, now everything is working fine. Thanks!

 Initial setup is almost complete now, just have to wait that half hour and then adjust the bias pots. Of course, I am unable to wait, so I'm listening to it now. It sounds great, of course. 
	

	
	
		
		

		
		
	


	




 Quick question, are there many headphones that sound better out of a 75-ohm adapter? I'm considering giving this amplifier a separate 75-ohm output just for the sake of variety.


----------



## amb

Quote:


  Originally Posted by *SDA* 
_Quick question, are there many headphones that sound better out of a 75-ohm adapter? I'm considering giving this amplifier a separate 75-ohm output just for the sake of variety._

 

I am of the opinion that inserting resistance inline with the headphones is detrimental to the performance, but apparently some phones out there are designed to work best with some resistance in series (this is why the Meier Corda amps have two outputs, one direct and one via 120 ohm resistors). 120 ohms is also a "standard" that few companies seem to adhere to. At any rate, I won't advocate it, and it's up to you to experiment.


----------



## rjkdivin

Quote:


  Originally Posted by *SDA* 
_Err, unfortunately, there's one more thing. Setup of G and R channels seems to have gone well enough, but the voltage across R5L stays around 17mV no matter how I adjust BIASOPL. I'm guessing I have a short or something, where should I start looking?_

 

So, you are able to adjust G and R to exactly 0.5v across R5? But when you adjust BIASOPL the voltage across R5L does not vary from 17mv at all....no movement?

 Oh...I see you solved the problem....enjoy!


----------



## wistily

My modest build:














 M3 with AD8610AR, a gain of 11, and a 24V Steps.
 Since it's my first diy build (not only electronic), i'm pretty proud of it. I havn't still got my DT880 back (2 month 1/2 at Beyer grrr), so i won't comment on sound, but i'm already happy with it.
 The electronic part was very easy to build but so wasn't the enclosure.
 Thank you amb and morsel for you nice amp, i hope there will be other top quality, easy to build projects available from you in the future (who said a nice dac? I know, i'm dreaming).


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## DigiPete

Nice job wistily! congrats!

 I am using DT880s with my M³ and love it! I think you will be pleased. I am using the OPA627s with my amp.

 Cheers
 DigiPete


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## xAPaperBoy

I agree, the DT-880 and the M³ sound awesome together.

 Now if I could just choose which op-amp I like best with this combination. Let's see, I have:
 AD825's
 AD8610's
 AD843's
 AD845's
 OPA627's
 OPA637's

 AMB and Morsel recommend the AD8610's. Some have commented that they like the OPA637 (L&R) and OPA627 (G) best -- much better than the OPA627 (L,R,&G).

 Honestly, I don't know what I prefer!? They all sound good.


----------



## Finch&Music

I am planning the building of an M3 and am in the process of choosing and gathering components. In the Netherlands that is not so easy, I have to make several stops to get a complete inventory for the M3. Some things comes from USA, others from Germany, others from local shops. But that is part of the fun. 

 I have some practical questions about yes or no using the possibilities of the 'bassboost-section'. Not using saves money also, but I want to go for a quality choice within the context of my reproduction chain.

 My M3 (with premium components) will be used with a Sennheiser 650 or a AKG K1000. May be in the future there will be an additional headphone, but that will be a quite neutral balanced one. As a source I will be using a Njoe Tjoep 4000 (a heavily modded Marantz 4000 with severe upsampling and a tube outputstage) or an older Philips transport with several modded external dac's. The first source has a output gain control of itself, the others presents a fixed outputsignal to the M3. The reproduction chain is primarily used for classical and jazz music (and some 'classical' rock) extracted from mostly good to outstanding recordings.

 Is there in such a chain in the practice of listening to music a usefull benefit to have a bassboost available for a little compensating for some not so good balanced recordings? 

 Or is it much more convenient to have a variable gaincontrol on board of the M3, so you can seek your most usable gainrange for the usable settings of the volumepot? 

 Or is it in practice only exceptional that you use the extra possibilities? I have already seen that there are some builders of the M3 that have not been using the bassboostsection at all. I am interested in the arguments for omitting the possibility. Do they miss something in reality or do they already feel the temptation to modify their configuration afterwards?

 When I choose for the possibility of a continuous variable gaincontrol (that is f.e. with an alps in combination with a dact attenuator): can I expect that with the alps in such a function I can compensate for the often heard complaint with a stepped attenuator that the steps are too coarse in practice? Or should I choose another way to overcome that?

 Greetings,

 Pieter.


----------



## morsel

Bass boost is a matter of personal preference. I like bass boost for enhancing bass weak recordings, of which there are many. Some people don't want to spend the extra money, or don't want to be tempted to tonally alter the original recording in any way for any reason. With the bass boost pot all the way down it does not affect the sound at all, so it will not hurt to include it. The K1000 is bass-shy, all the more reason to include bass boost.

 A variable gain control should not be necessary. A switch to choose between low and high gain should be sufficient in the case of using both efficient and inefficient headphones. Note that changing the gain control resistors affects bass boost response. It is better to increase R3 (to 2 or 3k) than reduce R4. Since the K1000 and HD650 are both inefficient you will probably not need any gain control.

 I believe complaints about stepped attenuators having steps that are too coarse are due to gain set too high for use with efficient low impedance headphones.

 Good luck with your M³.


----------



## meat01

Just got my amp back in its new enclosure. I had someone build me a nice wood enclosure and I am happy how it looks. I used a tread as the power supply. Here are some pictures.


----------



## SiuGuyGuy

I had built a M3 a running with good result 
	

	
	
		
		

		
		
	


	




 Now i want to try make it to push speakers, as recommended config from amb's web site. I had made a power supply with a Nuvotem Talema 0050P1-2-030K(50VA, 2nd 15-0-15VDC). I would like to ask is this transformer ok to run with speaker? 

 I just want to have a try first, and will source a bigger VA transformer if get good result. So just want to know if my 50VA is able to run it.

 My power supply config is LM317 + LM337, outputing 26V (+13V & -13V). and speaker is jmlab706s(8ohm, 90db)

 Thanks for reply first!


----------



## SiuGuyGuy

btw, meat01's amp is very impressive


----------



## amb

SiuGuyGuy, 50VA is big enough for speaker use. However you should upgrade the voltage regulators in your PSU. The problem is, there aren't many high-current negative regulators to choose from. Is there a reason why you're using dual regulators? I would suggest using a single LM338 regulator, adequately heat-sinked and adjusted to the voltage you want.

 The PSU's bridge rectifier may also need to be upgraded, depending on what you have.

 Note that a PSU voltage of 26V is going to restrict output voltage swing and the amp will clip at around 2W into 8 ohms.

 Search this thread for keyword "speakers" to see previous discussions on this topic.


----------



## steel

Hi AMB

 I just start build M3.
 some part are Difficult to find.
 can i use VISHAY CPF2 on R9?
http://www.vishay.com/docs/31021/cpf.pdf 

 thanks


----------



## morsel

You can use any 2W metal film resistors that will fit. The CPF2 is fine.


----------



## Jaypetermen

Does anyone know of additional suppliers for the 100uf/35V ELNA Cerafines or of an alternative bouquet cap for C4 and C5?


----------



## steel

Quote:


  Originally Posted by *morsel* 
_You can use any 2W metal film resistors that will fit. The CPF2 is fine._

 

Thanks...

 Is this a good idea for R9?
 to solder as a frame.
 i guess it will be hot


----------



## n_maher

Jay,

 The Cerafine line has been discontinued as far as I know. Try searching for Elna Silmic II's or Nichicon Muse Caps. I know that Handmade Audio carries some of each line, perhaps not exactly what you're looking for but close.

 Also, I posted a thread about this a while ago (which you can search for) and the general opinion from amb was that I was worrying about things which had little effect on the overall sound of the amp.

 HTH,

 Nate


----------



## amb

JayPeterman, check out Michael Percy Audio or Handmade for boutiquey-stuff. I don't believe that such caps would make a difference in C4 and C5, but if you insist... 
	

	
	
		
		

		
			





 steel, the R9 resistors normally do not get hot. The 2W rating is chosen because the output stage is _capable_ of very high current output (such as when driving speakers or very low-Z headphones) and we don't want the resistors to fail even under extreme conditions. While there is no harm in mounting the resistors the manner that you did, it is not necessary.


----------



## Syzygies

I've gotten the impression from various tech notes that it's a good idea to solder resistors flush with the PCB, to minimize signal path and stray inductances and so forth. On the other hand, we see 'dead bug' construction all the time for CMOY and similar amps, and the limitations of those circuits swamp whatever's wrong with the wiring of the jumble of parts.

 Amb has weighed in (for example) that the increased signal path can work against any benefits to switched attenuators, so for the M³ how one solders resistors may matter.

 So I don't know if R9 is a "good idea" as pictured, but this is the question the picture raises in my mind.


----------



## amb

Syzygies, it's true that additional lead length increases inductance but that only matters in high impedance areas of the circuit. At the output of the amp where R9 is, this is not the case.


----------



## Syzygies

Quote:


  Originally Posted by *amb* 
_...only matters in high impedance areas of the circuit. At the output of the amp where R9 is, this is not the case._

 

Hard to tell with the depth of field blur in the photo, but it looks like all the resistors are mounted in the same style?

 As a beginner myself, I know the temptation to emulate the style in the most beautiful photos, and that's one beautiful photo, which is why I raised the question.


----------



## stadams

Quote:


  Originally Posted by *Jaypetermen* 
_Does anyone know of additional suppliers for the 100uf/35V ELNA Cerafines or of an alternative bouquet cap for C4 and C5?_

 

Thrice has a few leftover SILMIC II's from the group buy a couple of months ago. Give him a buzz.

 Later,


----------



## Jazper

Heya all, just planning an M3 build and organising parts from various suppliers (well planning orders) and have a few questions.

 First of all, is there any downside to running the amp at 25-26v (for headphone use only)? 

 Second, I plan to use ELNA silmic II 100uF(c4, c5) and 330uF(c7) caps, however I'm looking at the 35v versions to keep costs under control, am I safe using these if I'm going to be running said 25-26v? 

 Thirdly, is there any benefit here using vishay dale low tolerance resistors here or will any generic low tolerance brand be fine?

 Forthly, (only if you can tell me) what's the peak current draw when the caps are charging at startup when c7 are 330uF caps?

 and finally, is there any downside to using an ad8610 for the ground channel while I use opa 637s for the left and right (as this is what I have handy at the moment)?


 Anyhow, great amp, appreciate the work you all put into it 
	

	
	
		
		

		
		
	


	




 Now to see if I can build it


----------



## amb

Quote:


  Originally Posted by *Jazper* 
_First of all, is there any downside to running the amp at 25-26v (for headphone use only)?_

 

No, the only exception is if the headphones you are planning to use are _extremely_ inefficient and require a huge amount of output voltage swing to get loud, and you like your music at earsplitting levels. Since it's been reported that even the (in)famous AKG K1000 worked well with a stock M³, I think this won't be an issue for other headphones.

  Quote:


 Second, I plan to use ELNA silmic II 100uF(c4, c5) and 330uF(c7) caps, however I'm looking at the 35v versions to keep costs under control, am I safe using these if I'm going to be running said 25-26v? 
 

Yeah, that is ok.

  Quote:


 Thirdly, is there any benefit here using vishay dale low tolerance resistors here or will any generic low tolerance brand be fine? 
 

Any good quality metal film 1/8W or 1/4W resistors are fine, except for R9 which should be 2W. Vishay-Dale RN55 series are very good and not too expensive, but cheaper generic resistors will be fine too.

  Quote:


 Forthly, (only if you can tell me) what's the peak current draw when the caps are charging at startup when c7 are 330uF caps? 
 

The actual peak current draw is difficult to estimate because it is limited by the ESR of the capacitors, as well as the impedances of the pcb traces to the capacitors, D1, wiring and connectors, and the PSU internal current limiting.

  Quote:


 and finally, is there any downside to using an ad8610 for the ground channel while I use opa 637s for the left and right (as this is what I have handy at the moment)? 
 

The transfer curves of the two types of opamps are different and you lose a bit of the "symmetry" (as seen from the headphone transducers) thus affecting linearity.


----------



## DigiPete

I was wondering is it is possible to implement a treble cut circuit in the M³ to help with some of those really harsh 80s CD (which I love so much).

 DigiPete


----------



## skyskraper

it would probably be better to get a proper eq unit like a parametric eq


----------



## DigiPete

Quote:


  Originally Posted by *skyskraper* 
_it would probably be better to get a proper eq unit like a parametric eq_

 


 That is one serious piece of hardware, with a serious price 
	

	
	
		
		

		
		
	


	




 I guess I could continue to listen to those CDs through speakers and use my receiver's treble control.


----------



## skyskraper

haahaha yeah i love avalon stuff, only used it once in a studio before.

 there are other parametrics in the sub 500 range that will do a really good job too. 

 hell you don't even need a parametric, a graphic eq would do the trick and theyre plentifully cheap these days


----------



## Jaypetermen

Is "-dB" a suitable substitute for "Volume" for labeling the volume knob on the front panel of the M3?


----------



## skyskraper

you can label it whatever you want, you still know the function of the knob. the common use of the word decibel is for a relative measure of sound pressure level

 label it whatever you want 
	

	
	
		
		

		
		
	


	




 on the front panel you have more freedom then most other parts of the amp


----------



## Ob3ron

Quote:


 s "-dB" a suitable substitute for "Volume" for labeling the volume knob on the front panel of the M3? 
 

 As was said above, call it whatever you like! And I do happen to like it!


----------



## funch

I thought this forum would be the best place to post this.
 I'm looking for an Option B case from the Par-metal group buy, 12x8x2.5. If anyone has an extra you would be willing to part with, please PM me. Thanks.


----------



## MisterX

Pick up your phone and dial 201-955-0800. 
 Then slowly tell the nice lady on the other end of the line that you would like to order one part # 20-12082M.


----------



## funch

OK, great! Thanks. 
	

	
	
		
		

		
		
	


	




 So, how slowly, exactly? Like, speak in all capitals letters, or what?


----------



## n_maher

I don't think MisterX was trying to be a wise guy, I think he was referring to the fact that ParMetals isn't exactly known for a. getting right the first time or b. anything resembling customer service.

 Good luck,

 Nate


----------



## MisterX

No I was referring to the fact that the nice lady at Par metals always needs me to repeat everything I say to her.


----------



## funch

Oh, yeah, I understood exactly what Mr. X meant. I've read thru the group buy thread and knew where he was coming from. Sorry if I came across a little 'wise' myself. When I used to teach 7th graders, if they weren't doing real well at listening to directions, I would ..speak..real..slow. It would drive them nuts, so the next time it happened, and I said "Do I have to speak in all capital letters", they knew what was coming and perked right up. Sometimes yah' gotta fight fire with fire!!


----------



## MisterX

lol
 I have not checked in a while but John from Par metals does occasionally sell surplus cases on Ebay. 
 It might be worth a shot. 
	

	
	
		
		

		
		
	


	




 Link----> http://stores.ebay.com/id=55712608


----------



## steel

M³ finished ... 
	

	
	
		
		

		
		
	


	




http://myweb.hinet.net/home9/st3388/M3/mmm.htm


----------



## MisterX

[size=small]Nice work![/size]


----------



## thrice

Cool, I like the illuminated IEC. Good job!


----------



## amb

steel, very nice casework!


----------



## steel

How hot is your MOSFET's heat sink?

 Mine is very HOT!


----------



## amb

Quote:


  Originally Posted by *steel* 
_How hot is your MOSFET's heat sink?
 Mine is very HOT!_

 

They can get quite hot depending on how high you set the bias and how well the case is ventilated. If you can put your finger on the top of the heat sink for more than a few seconds then chances are it's ok.


----------



## Jaypetermen

Quote:


  Originally Posted by *MisterX* 
_Pick up your phone and dial 201-955-0800. 
 Then slowly tell the nice lady on the other end of the line that you would like to order one part # 20-12082M. 
	

	
	
		
		

		
		
	


	


_

 

I called today and the 20-06082M is $75.00 each (without the front panel). I sure like those Group Buys!


----------



## gregmorris

I've been considering a one box amplification solution using the M3 as both a headphone amp and as a pre-amp to a gainclone. I was also thinking about building as the higher voltage design to get 6 hi-quality class-A watts. So in one box I would be able to switch between dedicated headphone amp/6-watt class A and a gainclone with signal fed through M3 first. 
 Are there any downsides or other considerations I should be thinking about? Should I just build in separate boxes with separate power supplies and connect externally? 
 Thanks for any input.

 Greg


----------



## amb

gregmorris, there is no real downside if you plan your gain appropriately between the two. One thing to note, though. The M³ is class A only when driving headphones. When serving as a speaker amp, it becomes class AB. It all has to do with the amount of bias. In order to stay in true class A in a push-pull amplifier, the quiescent current must be at least one half the peak output current. For 6Wrms output into 8 ohms, that means about 0.6A of constant quiescent current through each MOSFET (for a power dissipation of 11W each). Clearly, the little heat sinks are not adequate. However, when biased to 80mA quiescent (and working as a class AB 6W amp), it's still high quality 
	

	
	
		
		

		
			





.


----------



## gregmorris

Thanks for the information, Amb...and for making the design possible for me to build.

 I think I'll probably just use the M3 for headphone/pre-amp duties and not worry about the 6W for now.... 

 I've noticed that most SS pre-amps have an output impedence up to 100ohm. Would the M3's low output impedence, desirable for driving headphones, be ideally suited for the much higher input impedence of a gainclone?


----------



## amb

Quote:


  Originally Posted by *gregmorris* 
_I've noticed that most SS pre-amps have an output impedence up to 100ohm. Would the M3's low output impedence, desirable for driving headphones, be ideally suited for the much higher input impedence of a gainclone?_

 

There is no issue here. The reason many preamps have an output impedance in the hundreds of ohms range is that they have a series resistor at the output to prevent the (relatively weak) output stage from being damaged in a short circuit.

 In fact, the lower the preamp's output impedance, the better. It makes the setup less sensitive to interconnect cable capacitance, which contributes to stereo crosstalk and high frequency rolloff. The low output impedance also makes it more impervious to external noise interference.


----------



## gregmorris

amb, 

 On your parts list/explanation page you mention that the bass-boost pot. can be used to adjust gain for various impedence headphones if the bass-boost is not desired. If I went this route, could I just jumper the volume pot. and use the gain pot exclusively? Or would this negatively affect signal-to-noise ratio?


----------



## amb

Quote:


  Originally Posted by *gregmorris* 
_On your parts list/explanation page you mention that the bass-boost pot. can be used to adjust gain for various impedence headphones if the bass-boost is not desired. If I went this route, could I just jumper the volume pot. and use the gain pot exclusively? Or would this negatively affect signal-to-noise ratio?_

 

The gain adjustment range is limited (it cannot go below a gain of 1), so you'll still need a proper volume control.


----------



## sean-xenos

Hello,

 I'm new to the M³ project and would like to know more about gain and opamps.

 What gain is recommended for Grado RS-1 headphones (32 Ohms, 98dB SPL 1mV)?

 Which of the listed opamps would be a good match for the Grados, the default AD8610, the AD8065, AD843 or the OPA627/637?

 How do you like your M³ with Grados?

 Thanks a lot,
 Holger


----------



## amb

Quote:


  Originally Posted by *sean-xenos* 
_What gain is recommended for Grado RS-1 headphones (32 Ohms, 98dB SPL 1mV)?_

 

A gain of around 5 should be good, but this also depends on the output level of your source.

  Quote:


 Which of the listed opamps would be a good match for the Grados, the default AD8610, the AD8065, AD843 or the OPA627/637? 
 

This is more a personal preference sort of thing. Different people will recommend different opamps.

  Quote:


 How do you like your M³ with Grados? 
 

It works great! 
	

	
	
		
		

		
		
	


	




 The stout MOSFET output stage provides more than enough current to make the low impedance headphones sing.


----------



## sean-xenos

Quote:


  Originally Posted by *amb* 
_It works great! 
	

	
	
		
		

		
		
	


	




 The stout MOSFET output stage provides more than enough current to make the low impedance headphones sing._

 






 Thanks amb,

 good news: my M³ board has arrived today.
 Shipping took just 5 days from Sunnyvale to Berlin 
	

	
	
		
		

		
		
	


	




 Though opamps are a matter of personal tastes,
 I'd love to know more about the experiences of my fellow builders.
 Hey, there are at least a dozen of M³ owners here on this forum who own Grados!

 As far as I understood the instructions the OPA627/637 combo needs at least a gain of 8 to work properly in the M³, will this be ok with Grados?


----------



## amb

Quote:


  Originally Posted by *sean-xenos* 
_As far as I understood the instructions the OPA627/637 combo needs at least a gain of 8 to work properly in the M³, will this be ok with Grados?_

 

Yes, I recommend gain of 8 or greater if you're going to use the OPA637 in the L & R channels (it actually tested stable on my bench at a gain of 6, but I'd feel more comfortable recommending a minimum gain of 8). The difference between a gain of 5 and 8 is only a touch over 4dB, so it just means your volume control knob will be set a little lower to get the same perceived loudness.


----------



## gregmorris

I read that the PPA needed the input ground attached to the output ground on the preamp-out (if used as a preamp). Would this also be necessary for the M3 if it is driving an "active" load?


----------



## amb

Quote:


  Originally Posted by *gregmorris* 
_I read that the PPA needed the input ground attached to the output ground on the preamp-out (if used as a preamp). Would this also be necessary for the M3 if it is driving an "active" load?_

 

Yes, the pre-out jacks' ground should be wired to the IG points on the pcb (signal ground, not output ground).


----------



## CPL593H

Well it looks like the 25va +/-12v 7006 transformer is backordered at Digikey till July 22. Would another transformer work for a 26v supply?

 Would a +/-15v supply run the regulator too hot?
 Would a 15VA +/- 12V transformer have enough current capability (for headphones)?

 Thanks


----------



## rjkdivin

Quote:


  Originally Posted by *CPL593H* 
_Well it looks like the 25va +/-12v 7006 transformer is backordered at Digikey till July 22. Would another transformer work for a 26v supply?
 Would a +/-15v supply run the regulator too hot?
 Would a 15VA +/- 12V transformer have enough current capability (for headphones)?
 Thanks_

 

I have three STEPS running at 24v for use with M3s. Initially I used an 18+18 transformer.....it was too hot in my opinion, at about 142-146 deg. F on the regulator IC. As you stated, the 12+12 models have been slow to come by, so I switched to 15+15 while I waited for a back order. That dropped the temp by about 3-5 deg. When I finally got some 12+12s, it dropped the regulator temp by about another 3-5 deg., and they are now quite comfortable to touch.

 You can also adjust the output voltage up a few volts to decrease the voltage drop, and lower the temp a few degrees I believe AMB has stated that up to about 27v. input on the M3 is acceptable with the default opamps. You could also substitute in a taller heatsink if height was not a concern.

 I think the 15+15 or 12+12 are both fine with the standard heatsink. Im using the 25va models.


----------



## Jazper

when running bass boost, is there ainy benefit to having a switch across SbbL and SbbR (single position dual throw) so that it's switchable? or is there absolutely no boost when the pot is set to its maximum resistance setting?


----------



## amb

Quote:


  Originally Posted by *Jazper* 
_when running bass boost, is there ainy benefit to having a switch across SbbL and SbbR (single position dual throw) so that it's switchable? or is there absolutely no boost when the pot is set to its maximum resistance setting?_

 

There is no boost when the bass boost pot is set to its _minimum_ (fully-counterclockwize) position. The only "benefit" of an additional bass boost switch wired to the Sbb* positions is you can defeat the boost with just a flick of the switch, and restore to the same boost level again without turning the pot. Otherwise, the switch is redundant.


----------



## Jaypetermen

I am performing the initial setup on my M3 and have a couple of questions before I want to continue.

 With my DMM set to 200mVDC, I am reading 0.8 measuring DC voltage across the R9G+ resistor. AMB’s Initial Setup section states that I should “adjust the BIASG trimpot clockwise until you read 80mV.” I have turned BIASG up all the way and the largest value I can achieve is 2.0 on the three channels?

 With my DMM set to 200mVDC, I also checked the DC offset voltage between IG and OL, IG and OR, IG and OG respectively. I am reading the following so it appears that the DMM is working properly.

 0.0mV on IG and OG
 0.6mV on IG and OR
 0.7mV on IG and OL

 To measuring DC voltage across the R9G+ resistor I am probing the two leads of the R9G+ resistor. Is this the proper way to take this measurement?

 Also, how do I measure the source to make sure it has no DC offset at its output?


----------



## rjkdivin

Quote:


  Originally Posted by *Jaypetermen* 
_I am performing the initial setup on my M3 and have a couple of questions before I want to continue.
 With my DMM set to 200mVDC, I am reading 0.8 measuring DC voltage across the R9G+ resistor. AMB’s Initial Setup section states that I should “adjust the BIASG trimpot clockwise until you read 80mV.” I have turned BIASG up all the way and the largest value I can achieve is 2.0 on the three channels?
 With my DMM set to 200mVDC, I also checked the DC offset voltage between IG and OL, IG and OR, IG and OG respectively. I am reading the following so it appears that the DMM is working properly.
 0.0mV on IG and OG
 0.6mV on IG and OR
 0.7mV on IG and OL
 To measuring DC voltage across the R9G+ resistor I am probing the two leads of the R9G+ resistor. Is this the proper way to take this measurement?
 Also, how do I measure the source to make sure it has no DC offset at its output?_

 

I'm sure AMB can point you in the right direction if he is on today, but here are a few things you can check:
 1. Check the output voltage of your power supply.
 2. Check the DC voltage across the + and - rails by touching your DMM leads to the mounting tabs at Q1G+ and Q1G-. It should be about the same as the PS output. Also, does your LED light up?
 3. Have you measured the voltage across R5G? Can you achieve 0.5vdc there?
 Now basic component checks:
 4. Make sure you have D1 installed with the correct polarity.
 5. Check your Q1 ICs to be sure you have all the Z24Ns in the Q1+ positions and the 9Z34Ns in the Q1- possitions.
 6. Make sure you have not reversed the positions of the BIAS (5kohm) and BIASOP (1kohm) trimpots.
 7. Check to be sure you have oriented the opamps with pin 1 in the correct position.
 8. Last, check all your electrolytics to be sure you oriented with the correct polarity.

 Yes, you measure the mvdc across the R9s by touching one probe of your DMM to each lead of the resistor with the resistor in place.


----------



## CPL593H

I think the 15+15 or 12+12 are both fine with the standard heatsink. Im using the 25va models.[/QUOTE]


 thanks, I'll try a 15+15 and up the voltage as much as possible.


----------



## Jaypetermen

Quote:


  Originally Posted by *rjkdivin* 
_I'm sure AMB can point you in the right direction if he is on today, but here are a few things you can check:
 1. Check the output voltage of your power supply.
 2. Check the DC voltage across the + and - rails by touching your DMM leads to the mounting tabs at Q1G+ and Q1G-. It should be about the same as the PS output. Also, does your LED light up?
 3. Have you measured the voltage across R5G? Can you achieve 0.5vdc there?
 Now basic component checks:
 4. Make sure you have D1 installed with the correct polarity.
 5. Check your Q1 ICs to be sure you have all the Z24Ns in the Q1+ positions and the 9Z34Ns in the Q1- possitions.
 6. Make sure you have not reversed the positions of the BIAS (5kohm) and BIASOP (1kohm) trimpots.
 7. Check to be sure you have oriented the opamps with pin 1 in the correct position.
 8. Last, check all your electrolytics to be sure you oriented with the correct polarity._

 

1.27.5VDC and is correct
 2.Did not do this, a little unclear where to probe?
 3.Adjust the BIASOPG trimpots until you got 0.5VDC
 Now basic component checks:
 4.D1 polarity installed correctly.
 5.Q1 ICs installed correctly.
 6.Oops, BIAS (5kohm) and BIASOP (1kohm) trimpots reversed.
 7.Opamps installed correctly.
 8.Electrolytics installed correctly.

 Thank you rjkdivin. I will swap the trimpots and see if this brings the R9s to 80mv.

 Is there a way to breed the LED voltage after the units have been shut off or will they bleed when I turn up the volume pot and provide a load?


----------



## rjkdivin

Quote:


  Originally Posted by *Jaypetermen* 
_1.27.5VDC and is correct
 2.Did not do this, a little unclear where to probe?
 5.Q1 ICs installed correctly.
 6.Oops, BIAS (5kohm) and BIASOP (1kohm) trimpots reversed.
 Is there a way to breed the LED voltage after the units have been shut off or will they bleed when I turn up the volume pot and provide a load?_

 


 I suspect that correcting the BIOS and BIOSOP pots will do the trick.

 To measure the voltage on the rails, you actually touch your DMM leads to the metal mounting tabs of the Q1G+ and Q1G- ICs (this works with the right and left IC pairs as well)....these are the tabs that you attached to the heat sinks. They are actually electrified.

 The LED will dim down as the rail capacitors discharge. The LED and RLED will accomplish this slowly even without a load.....no real need to speed it up.


----------



## amb

Jaypeterman, rjkdivin gave some great pointers. Hope that was enough to get you going.


----------



## Jaypetermen

Quote:


  Originally Posted by *rjkdivin* 
_I suspect that correcting the BIOS and BIOSOP pots will do the trick._

 

I swapped the ground channels trim pots and now I have 80vm. All values are within range per "Initial Setup" for the ground channel. 
	

	
	
		
		

		
			





 I am about ready to try the M3 with headphones. How do I measure the source to make sure it has no DC offset at its output?


----------



## Jaypetermen

AMB’s “Wiring & ground” for external power supply states; “To allow the M³ amplifier chassis to act as a shield, the RCA input jacks' ground connections should be electrically connected to the chassis, which should also be mechanically and electrically tied to the housings of the volume and bass boost potentiometers.” 

 Does this mean that the RCA input jacks' ground connections should be electrically connected to the chassis and which would connect them to the signal ground IG pads?


----------



## skyskraper

yup, check the diagram above the text.


----------



## Jaypetermen

Quote:


  Originally Posted by *skyskraper* 
_yup, check the diagram above the text._

 

I was unsure from the diagram of which component, of the RCA jack, is required to be electrically connected to the chassis. The RCA body or signal ground pin!


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_I was unsure from the diagram of which component, of the RCA jack, is required to be electrically connected to the chassis. The RCA body or signal ground pin!_

 

The RCA jack (and plug)'s outer shell _is_ the signal ground. The center pin is the signal (non-ground). The signal ground is the one that should be connected to the case.


----------



## Jaypetermen

[ Quote:


  Originally Posted by *amb* 
_The RCA jack (and plug)'s outer shell is the signal ground. The center pin is the signal (non-ground). The signal ground is the one that should be connected to the case._

 

So the RCA jack's outer shell should be electrically tied to the chassis. _Not_ the center pin. 

 Also, how do I measure the source to make sure it has no DC offset at its output?


----------



## MisterX

Quote:


 So the RCA jack's outer shell should be electrically tied to the chassis. Not the center pin. 
 

Correct. 
	

	
	
		
		

		
		
	


	




  Quote:


 Also, how do I measure the source to make sure it has no DC offset at its output? 
 

Your + probe goes to right/left output and the - probe on your dmm connects to the ground.


----------



## Jazper

Alrighty, I'm struggling, the amp is put together, I'm using my first powersupply design (which is essentially a snubberised steps (can easily provide the voltage) 

 I dropped a LM741 in the ground channel (because that's all I have on hand that's dip) and started testing

 ... 

 Voltage is fine across the opamp..(27.2v/13.62v) 

 0.5v on R5G

 0.1->0.9mv on R9+?!? (depending on where the pot is set) 

 voltage going to the board is 29v +-05v. 

 checked components, checked soldering job .. all ok.. 
	

	
	
		
		

		
		
	


	




 I doubt my multimeter is faulty..


 help please? (better chips are coming... just wanted to see if I could set it up beforehand)


----------



## amb

Quote:


  Originally Posted by *Jazper* 
_I dropped a LM741 in the ground channel (because that's all I have on hand that's dip) and started testing_

 

OK if you're just playing with the circuit, but I would expect that the 741 opamp to cause high DC offset problems at the amp output due to its high input bias current (and the DC offset would vary as you turn the volume pot). Don't connect headphones!

  Quote:


 0.1->0.9mv on R9+?!? (depending on where the pot is set) 
 

Measure the voltage across C2, as you turn the BIAS trimpot from minimum and up. Do not turn past about 8V (if you could go that high) to prevent too much quiescent current. Can you achieve 8V or so? If not, what's the highest you could get? At that point, what are the voltages at both leads of C2 relative to IG?

 Double check the values of your BIAS trimpot, as well as R6 and R7 to make sure they are correct. What do the markings say?

 Also, with a 29V supply you've exceeded the max voltage rating of the AD8610 or AD8065 opamps. I hope you're not planning to use these.


----------



## Jazper

Quote:


  Originally Posted by *amb* 
_OK if you're just playing with the circuit, but I would expect that the 741 opamp to cause high DC offset problems at the amp output due to its high input bias current (and the DC offset would vary as you turn the volume pot). Don't connect headphones!


 Measure the voltage across C2, as you turn the BIAS trimpot from minimum and up. Do not turn past about 8V (if you could go that high) to prevent too much quiescent current. Can you achieve 8V or so? If not, what's the highest you could get? At that point, what are the voltages at both leads of C2 relative to IG?

 Double check the values of your BIAS trimpot, as well as R6 and R7 to make sure they are correct. What do the markings say?

 Also, with a 29V supply you've exceeded the max voltage rating of the AD8610 or AD8065 opamps. I hope you're not planning to use these._

 


 max of the voltage across c2 is .489v 
 the leads are approx .457 and .019 to IG respectively at max. 

 I'll lower the voltage for ad8610 use. 

 about to doublecheck the values of the Bias and r6/r7, but I did use the excel file on your site


----------



## Jazper

Trimpot for bias is 1k according to the markings on it. just tested R7 (7.5k), R6 is 1.001k according to my multimeter
 appears that I made a mistake with the bias trimpots.. changing them out now..


----------



## Jazper

well this isn't going well

 I slipped with the soldering iron and shorted something while it was off, obviously the caps didn't discharge.. voltages over the board are :S 

 only <1v around the opamps.. I'm guessing (and hoping) I just killed the railsplitter :S


----------



## amb

Quote:


  Originally Posted by *Jazper* 
_only <1v around the opamps.. I'm guessing I just killed the railsplitter :S_

 

Check the voltage across the collector and emitter pins of Q5+ and Q5-. It's more likely that one or both of these are blown rather than the TLE based on your description.


----------



## Jazper

Quote:


  Originally Posted by *amb* 
_Check the voltage across the collector and emitter pins of Q5+ and Q5-. It's more likely that one or both of these are blown rather than the TLE based on your description._

 

will do as soon as I remove/ change the trimpots


----------



## Jazper

Q5- has about 1.3v going through it

 q5+ has about 3.5v going through it

 the spark was amber, if that helps at all


----------



## Jazper

it should be noted that the reason the pots were mixed up is that I followed the excel file on your site amb - the 5k and 1k pots are flipped (parts number wise) and on my mouser order I transferred the parts name (Mbias etc) to the order. Might be wise to correct that, and while that's being done it should be noted that C2 is only available in lots of 5000 or so from mouser so an alternate part might be worth looking into.. (this is why I was a few caps short when the order arrived)


----------



## amb

Quote:


  Originally Posted by *Jazper* 
_Q5- has about 1.3v going through it
 q5+ has about 3.5v going through it_

 

The numbers don't add up. If you are only measuring 1.3 + 3.5V drop across these transistors, then where are all the rest of the volts going (assuming you still only have <1V at the opamps)? Measure the voltage at pins 7 relative to IG of the opamp, and then do the same at pin 4 relative to IG. Lastly, measure across pins 7 and 4 of the opamp. What do you read?

  Quote:


 it should be noted that the reason the pots were mixed up is that I followed the excel file on your site amb - the 5k and 1k pots are flipped (parts number wise) and on my mouser order I transferred the parts name (Mbias etc) to the order. 
 

Yup, the part numbers are swapped but the descriptions aren't. The excel file is from n_maher and hosted on Nisbeth's site. I'll ask them to fix this. At any rate, you should use the schematic diagram to assemble the amp, not the BOM (the BOM is only a guide for you to buy the parts). You'll get a better feel of what you're actually doing by looking at the schematic.


----------



## n_maher

Spreadsheet fixed and revised version emailed to Nisbeth, sorry for the confusion. 

 Nate


----------



## Jazper

rechecking to make sure I'm reading right - just woke up

 4 to IG is .103

 7 to IG is .103 

 4 to 7 is 0


----------



## amb

Quote:


  Originally Posted by *Jazper* 
_rechecking to make sure I'm reading right - just woke up

 4 to IG is .103
 7 to IG is 0 
 4 to 7 is 0_

 

Looks like your Q5+ and Q5- need to be replaced. Fortunately these are 2N3904/2N3906 and are easy to get and cheap.


----------



## Jazper

will the NE5534 work with the m3 as a temporary measure(can pick them up when I go get the 2n3904)? or do I have to worry about offset again?

 btw thanks for your help amb


----------



## amb

Quote:


  Originally Posted by *Jazper* 
_will the NE5534 work with the m3 as a temporary measure? or do I have to worry about offset again?_

 

The 5534 is also a bipolar input opamp, and has the same high input bias current issue as the 741. If you have some TL081, TL071, LF351 or LF356 JFET opamps around, these would be ok for temporary purposes. They won't sound as good as the recommended higher-performance opamps, but at least the circuit would work ok.


----------



## Jazper

ok, I've been unable to get the opamps I need, however, a tip for builders, make sure the LED is connected, it'll drain the caps if nothing else does.

 AMB: after replacing Q5+ and Q5- voltages are back to normal on the opamp pins


----------



## amb

Quote:


  Originally Posted by *Jazper* 
_ok, I've been unable to get the opamps I need, however, a tip for builders, make sure the LED is connected, it'll drain the caps if nothing else does._

 

Yeah. Although in normal situations (when the MOSFETs are biased properly), the quiescent flow through the MOSFETs will drain the rail caps fairly quickly.

  Quote:


 AMB: after replacing Q5+ and Q5- voltages are back to normal on the opamp pins 
 

Cool. I hope you're able to dial in the proper opamp and MOSFET bias currents now.


----------



## Jaypetermen

Quote:


  Originally Posted by *jaypetermen* 
_Also, how do I measure the source to make sure it has no DC offset at its output?_

 

 Quote:


  Originally Posted by *MisterX* 
_Correct. 
	

	
	
		
		

		
			





 Your + probe goes to right/left output and the - probe on your dmm connects to the ground._

 

I placed the + probe on the right/left output of the interconnects ¼ plug, the – probe on the ground section (closest to the plugs housing) and read 25mvdc out of my Zen Touch DAP.

 I then connected the Zen Touch up to the M3 with a ¼ plug -> RCA interconnect cable, turn up the volume all the way and read 30mvdc. Then I turned up the bass all the way, in conjunction with the volume being maxed, and read 150mvdc.

 Are these values excessive for the dc offset? Just want to make sure everything is okay before plugging in my HD 650s.


----------



## MisterX

Quote:


 RCA interconnect cable, turn up the volume all the way and read 30mvdc. 
 

Is the Zen idle or is playing something? 
 If it was playing something then you need to retest because most DMM's have a hard time measuring DC when there is a AC signal present and it will give you a bogus reading. 
 Nothing is ever that easy is it?


----------



## amb

If the 25mV offset from your Zen Touch is at idle, then it's too high. That offset is then amplified by the gain of your amp before it reaches your headphones. You might even hear scratchy noises while turning the volume pot when there is high enough DC offset present. I don't recommend using a source like that with a direct-coupled amp (e.g., M³) without adding a coupling capacitor. 

 While high impedance phones like the HD650 can handle higher DC offsets than a low impedance phone, I'd feel better if the actual offset "seen" by the headphone is less than 10mV. Turning up the bass boost will increase the offset if there is some, because the gain at low frequencies, all the way down to DC, is increased.


----------



## Jazper

Quote:


  Originally Posted by *amb* 
_Yeah. Although in normal situations (when the MOSFETs are biased properly), the quiescent flow through the MOSFETs will drain the rail caps fairly quickly.


 Cool. I hope you're able to dial in the proper opamp and MOSFET bias currents now._

 


 urm.. I'll find out when I get opamps in there


----------



## Jaypetermen

The Zen Touch was in play mode with it's volume turned up 75% when I took the DC offset reading. The reading was actually all over the place, out of the Zen, but settled down to 25vdc.

 Re-measured with the Touch in idle mode and initial reading was around 30mvdc but quickly decreased to 12mvdc.

 Measured 33vdc, which also decrease to 11mvdc (left) and 13mvdc (right) with the Touch in idle mode and M3's volume at max. This appears to be within limit?

 I do not know why the dc offset decreases. Maybe it decreases when the units warm. It performed these measurements directly after turning the units on.

 With the thought that the DC offset is in check, I plugged my PX-100s into the M3 for the first listen. Dead silence all the way up to full volume with the Zen in play mode 
	

	
	
		
		

		
		
	


	




 The following are reading taken with DMM:

 - 24.7v from pin 4 to 7 on three op-amps. Running STEPS at 27.5v.
 - 0.5v across R5 on all three channels.
 - 89.mvdc across R9+ and within 5% on R9-. Planning to increase 10 to 15mv prior to putting in case.
 - Tested DYI interconnect cable between Zen Touch and receiver. It works in with these components 

 Any ideas on why there wouldn't be a audio output?


----------



## n_maher

This is a somewhat M³ related question, but has more global implications. My amp will have an internal STEPS and so I was originally thinking that I would have a tiered power switch setup where there was a "MAIN" switch that controlled the flow of AC to the STEPS and a "SECONDARY" switch that controlled the flow of DC to the amp. I seem to remember having read that having only a switch on the STEPS could be bad for the regulator and I know how hot the STEPS can get if you leave it constant plugged in so here's my question(s). Is just switching the AC a bad idea? Will this in fact be hard on the power supply? Any suggestions on how things could be done differently and use just a single switch?

 As always help is greatly appreciated.

 Nate


----------



## steinchen

One builder recorded probs with a switch between psu and M³, frying his regulator when connecting his M³ to the already powered up psu. Conclusion was that the high inrush current into the empty caps killed the regulator. When powering up the psu with connected amp the regulator switches into current limiting mode and survives.

 There was only a single user having this prob and I guess there was someting else "different" in his build. I think he solved his prob by substituting LM317 with LM338.

 Unless you don't put more than the recommended 2.000 to 3.000uF rail capacitance into your amp either of the assembling plans you mentioned should work. There are many builders out there with full 9.000uF (not recommended !) in their PPA or M³ without having probs.

 The temperature of the heatsink depends on the voltage drop across the regulator and the current you draw from the psu. With a voltage drop of 4V and current draw of 300mA you'll get 4 * 0.3 = 1.2 Watts of heat dissipation. The big heat sink of the steps should be about 10°C above ambient temperature. Picking an approbiate transformer for your application is the most important step to keep the heatsink cool / warm (and not hot).


----------



## n_maher

Quote:


  Originally Posted by *steinchen* 
_One builder recorded probs with a switch between psu and M³, frying his regulator when connecting his M³ to the already powered up psu. Conclusion was that the high inrush current into the empty caps killed the regulator. When powering up the psu with connected amp the regulator switches into current limiting mode and survives._

 

Thanks, that'll make things much easier for at least one setup I want to run.
  Quote:


  Originally Posted by *steinchen* 
_There was only a single user having this prob and I guess there was someting else "different" in his build. I think he solved his prob by susbtituting LM317 with LM338._

 

Good to know my memory isn't totally shot 
	

	
	
		
		

		
		
	


	




.
  Quote:


  Originally Posted by *steinchen* 
_The temperature of the heatsink depends on the voltage drop across the regulator and the current you draw from the psu. With a voltage drop of 4V and current draw of 300mA you'll get 4 * 0.3 = 1.2 Watts of heat dissipation. The big heat sink of the steps should be about 10°C above ambient temperature. Picking a approbiate transformer for your application is the most important step to keep the heatsink cool / warm (and not hot)._

 

You're exactly right. Too much voltage drop = too hot a STEPS. But either way I still don't want the STEPS powered up all the time as I'll be using it's LED pads for interior illumination (bling) so having it switched is key. I also purchased a large heatsink for the steps so that I can be doubly sure that it won't get too hot regardless of setup. 

 Anyway, thanks for your help!

 Nate


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_Any ideas on why there wouldn't be a audio output?_

 

Post links to hi-res photos of your board and wiring, including the jacks/connectors. Maybe something is wrong?
 Also, check your headphones to make sure it's still working on something else.


----------



## Jaypetermen

Confirmed that the headphones are still working properly. In fact I listened to them on the M3.

 While taking pictures I realized what was wrong. See if you can figure it out from these pictures. The picture does not exactly show the mistake, you may have to guess:
















 Thanks for all your help on this amp. All that left is to decide on a front panel scheme for the M3 and STEPS.


----------



## n_maher

Quote:


  Originally Posted by *Jaypetermen* 
_Confirmed that the headphones are still working properly. In fact I listened to them on the M3.

 While taking pictures I realized what was wrong. See if you can figure it out from these pictures. The picture does not exactly show the mistake, you may have to guess:_

 

Did you have the switched headphone jack wired wrong? Wouldn't be the first person to do that, trust me 
	

	
	
		
		

		
		
	


	




.

 Regardless, glad to hear that you got it working.

 Nate


----------



## Jaypetermen

Quote:


  Originally Posted by *n_maher* 
_Did you have the switched headphone jack wired wrong? 
 Nate_

 

Yes, that’s it. 

 Anyway, I have the M3 all setup and it sounds very good. 
	

	
	
		
		

		
		
	


	




 I may make some adjustments to achieve more gain for the 650s.






 Now to work on the front panels for the M3 , Steps, and Millet-Hydrid. I am tiring to decide on one of the following. I think that there are pros and cons to each version. Opinions are welcome.


----------



## funch

I just thought I'd shout out a big thank you to Mister X for the info and link to Par Metal's eBay store, antek inc. on page 28 of this thread. I kept checking it, and my patience was rewarded. John listed the perfect case: vented, all aluminum, in black, 16x8x3. Perfect for my M3 with a Hagerman Bugle phono pre and STEPS. To my door for 69 bucks. Now I've got all the boards and the perfect case to boot. What else do I need? Oh yeah; the stuff to put in the boards! And decide on knob color. That could be a challenge!! Thanks again!!


----------



## amb

Jaypetermen, I am glad your amp is working fine now. As for the three front panels, they are all nice. I prefer the first two a bit more, especially the second one, but I'd reduce the M³ logo a bit. It's a bit BIG. 
	

	
	
		
		

		
		
	


	




 Btw those are nice looking knobs. Where did you get them?


----------



## Jazper

Amb: the amp appears to be working, just finalising the power supply, the psu that was supplying 29v sagged to 28.25 when I pumped up the quiescent current so I think AD8610s should be safe in it - thanks for all the help (I'd never have worked out that T5+ amd - were dead without you) Will post more info as it unfolds in my thread.


----------



## Jaypetermen

Quote:


  Originally Posted by *amb* 
_ As for the three front panels, they are all nice. I prefer the first two a bit more, especially the second one…_

 

I personally like the second version the best also. The potentials cons with this FP is its most distinctive feature, the milled out center section. This section would be milled down .010” to .020”. The remaining edge may be sharp, the anodize may chip at the edge during or after machining, machine tooling marks may be left in the recessed section and it would not be protected with anodize. FP #3 resolves these problems, but I do not think that it looks as good. 

 Your input is welcome if you have machining knowledge/experience to confirm or discard these potential machining issues.

 Here’s a combination of #2 & #3 and would have the same potential cons as #2.







  Quote:


  Originally Posted by *amb* 
_Btw those are nice looking knobs. Where did you get them?_

 

The knobs are from Audio Electronic Supply (Cary Audio). The larger knob is the 1 1/2" beveled face and the small is the ¾” beveled face. They do not list the Aluminum knobs on there web site. I called in the order on these. They are around $25 each, not cheap.

http://www.audioelectronicsupply.com...4&aisle_id=242


----------



## MisterX

Quote:


 Here’s a combination of #2 & #3 and would have the same potential cons as #2. 
 


 Where is the isolation washer? 

 Without the isolation washer you end shorting out the ground channel on the amp.


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_Your input is welcome if you have machining knowledge/experience to confirm or discard these potential machining issues._

 

Sorry, I am not experienced with that. Others might be able to help though.

  Quote:


 The knobs ... They are around $25 each, not cheap. 
 

Gulp. 
	

	
	
		
		

		
		
	


	



 Definitely boutique!


----------



## Jaypetermen

Quote:


  Originally Posted by *MisterX* 
_Where is the isolation washer? 

 Without the isolation washer you end shorting out the ground channel on the amp._

 

Yes correct. Sorry, just did not put it in the picture. The isolation washer will be between the chrome cap and the front panel.

 I am still looking to find a isolated jack, which will thread into the front panel. Something like this:


----------



## MisterX

Mouser #502-N112B = isolated 1/4" switchcraft jack that will screw into the case
 It ain't pretty though.


----------



## Jaypetermen

I would like to increase the gain of the M3 for HD-650s. 

 My STEPS is outputting 27.5VDC and the DC voltage across the R9G+ resistor is currently 80mV. AMB’s “Maximum recommended quiescent current” table shows that at 26V the Maximum recommended quiescent current is 140mA. 

 I could increase the BIASG trimpot until I read 140 + 15 = 155mV across the R9G+? (15mV to account for enclosing) 

 ”If you are using an unventilated case, you should restrict the quiescent current to no more than 50mA per channel.” –AMB’s Initial Setup. 

 My case is not vented on the top, just the sides. So this statement doesn't apply. Right?


----------



## MisterX

Non ventilated = no vents at all. 
 Yup, that statement does not apply to your case.


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_I am still looking to find a isolated jack, which will thread into the front panel._

 

There are versions of the jack that you currently use, that has an insulated (plastic) thread bushing: Rean NYS212
Neutrik NMJ6HF-S


----------



## Jaypetermen

Neutrik/RE-AN 1/4' Phone Jack, NMJ6HCD2. Mouser P/N: 550-22302

http://www.neutrik.com/images/ock/pr...210_217181.pdf


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_Neutrik/RE-AN 1/4' Phone Jack, NMJ6HCD2. Mouser P/N: 550-22302_

 

The mounting collar isn't insulated on this one, though. If it's chrome/metal, then the 1/4" plug "ground" will touch it and short to the chassis unless you use insulating washers.


----------



## Jaypetermen

Quote:


  Originally Posted by *amb* 
_The mounting collar isn't insulated on this one, though. If it's chrome/metal, then the 1/4" plug "ground" will touch it and short to the chassis unless you use insulating washers._

 

The collar is chrome/metal and threaded. It appears to screw into 100% into the plastic jack housing. The part comes with spacers to make up any slop/clearance.






 I have not used this jack, since I do not have a front panel yet. 

 I soldered on another jack, temporarily, to test the M3. I am not 100% sure that the metal collar will not contact the enclosure but it looks like it should be okay.


----------



## rreynol

I have used the jack with chrome nose on a pimeta in one of the aluminum hammonds. I used the washers and they do isolate it from the chassis. It is the jack I like to use on metal cases.


----------



## rjkdivin

Quote:


  Originally Posted by *steinchen* 
_One builder recorded probs with a switch between psu and M³, frying his regulator when connecting his M³ to the already powered up psu. Conclusion was that the high inrush current into the empty caps killed the regulator. When powering up the psu with connected amp the regulator switches into current limiting mode and survives.

 There was only a single user having this prob and I guess there was someting else "different" in his build. I think he solved his prob by substituting LM317 with LM338.

 The temperature of the heatsink depends on the voltage drop across the regulator and the current you draw from the psu. With a voltage drop of 4V and current draw of 300mA you'll get 4 * 0.3 = 1.2 Watts of heat dissipation. The big heat sink of the steps should be about 10°C above ambient temperature. Picking an approbiate transformer for your application is the most important step to keep the heatsink cool / warm (and not hot)._

 

Yes....I was the builder with the regulator problem. In one of my M3 builds I placed the M3 and Steps in separate cases. I switched the AC input to the Steps, AND I switched the DC input to the M3. If I turned on the M3 after I turned on the Steps, it would blow the LM318 regulator. If I swithched on the M3 before I switched on the Steps, it worked fine. As stated, the problem was solved by going to the LM338T regulator which has a higher current rating, and current limiting circuitry.

 Regarding the temperature of the regulator on the Steps, I recommend using the 12v + 12v 25VA model...Amveco 70062K, but the 15v + 15v model also maintains acceptable temperatures. The 18v+18v model was too hot in my Steps.


----------



## sean-xenos

Quote:


  Originally Posted by *rjkdivin* 
_....Regarding the temperature of the regulator on the Steps, I recommend using the 12v + 12v 25VA model...Amveco 70062K, but the 15v + 15v model also maintains acceptable temperatures. The 18v+18v model was too hot in my Steps._

 

Would the 12V + 12V 15VA model (Amveco 70052) be sufficient for the M³ 
 if I use it as a headphone amp for 32 Ohms phones?


----------



## n_maher

You could probably expect to get 30 or so useable volts out of that transformer. I tend to use the larger, 15V transformer for anything higher than 28V but there's no magic to that, just my random nature.


----------



## sean-xenos

Quote:


  Originally Posted by *n_maher* 
_You could probably expect to get 30 or so useable volts out of that transformer. I tend to use the larger, 15V transformer for anything higher than 28V but there's no magic to that, just my random nature._

 

Well I will either use OPA627s or AD8610s as opamps,
 so I guess 28 Volts will be enough.

 I was just wondering why (almost?) everybody was recommending 25VA transformers and if 15VA models are enough for headphone use. I don't plan to use the M³ as a pre-amp or to power loudspeakers.


----------



## skyskraper

12 + 12 v ac = ~17 + 17 v DC

 more then enough to get even 30v out of a teps.


----------



## rjkdivin

Quote:


  Originally Posted by *sean-xenos* 
_Would the 12V + 12V 15VA model (Amveco 70052) be sufficient for the M³ 
 if I use it as a headphone amp for 32 Ohms phones?_

 

32ohms is a fairly low impedance for headphones, and so they can potentially draw more power than a more typical headphone with 80 to 300ohms. AMB could give you a more definitive and more reliable answer, but I would be concerned about the potential for clipping with the 15VA transformer instead of the 25VA. At 15VA and 24vdc output from your STEPS, that is considerably less than 1 amp which is AMB's recommended input for the M3. The 25VA model gives you slightly over 1 amp.


----------



## amb

A 25VA transformer is more than what's needed for "normal" headphone loads, but a bit of conservative over-engineering never hurts anyone (especially since it is only $2 more expensive than the 15VA model from Digikey). It also gives you some useful headroom in case you want to connect even lower impedance (or very inefficient) headphones, or use speakers.

 All that said, there is nothing wrong with using the 15VA model. It is perfectly fine in most cases. There are people using the Elpac WM080 24V 330mA wallwart with the M³, and it works ok (but with no headroom).


----------



## Jaypetermen

Quote:


  Originally Posted by *Jaypetermen* 
_I would like to increase the gain of the M3 for HD-650s. 

 My STEPS is outputting 27.5VDC and the DC voltage across the R9G+ resistor is currently 80mV. AMB’s “Maximum recommended quiescent current” table shows that at 26V the Maximum recommended quiescent current is 140mA. 

 I could increase the BIASG trimpot until I read 140 + 15 = 155mV across the R9G+? (15mV to account for enclosing) _

 

I adjusted the BIAS(all) trimpot until I read 155mV across the R9(all)+ and the amp did not appear to provide more output. The sound did seem to become bright/fatiguing. I adjusted back to 100mV, figuring that it will drop back to around 80mV cased, and the amp sounded good.

 Has anyone experienced this bright/fatiguing sound when turning up BIAS(all)?


----------



## amb

Quote:


  Originally Posted by *Jaypetermen* 
_I adjusted the BIAS(all) trimpot until I read 155mV across the R9(all)+ and the amp did not appear to provide more output. The sound did seem to become bright/fatiguing. I adjusted back to 100mV, figuring that it will drop back to around 80mV cased, and the amp sounded good.

 Has anyone experienced this bright/fatiguing sound when turning up BIAS(all)?_

 

Turning up the bias simply increases the quiescent current (and make the amp operate deeper into class A). It does not increase apparent output. The only "advantage" for doing so is to prevent the amp from dropping out of class A (and operate in class AB mode) when delivering large output power.

 As for sounding worse when the bias increased beyond a certain point, I don't know why. I've done RMAA measurements on my prototype and it showed no significant difference between 80mA and 160mA, but RMAA doesn't make the amp swing large voltages. Listening tests reveal no differences either (with my HD600s).

 The range of quiescent currents allowed, as listed on my site is based on the assumption that the PSU can deliver the needed current, and it's possible that your increased currents are stressing the PSU (you're pulling about 0.5A at this point), but the STEPS should be able to handle that. Make sure the regulator's temperature is ok and not going into thermal shutdown.

 It seems you have HD650s, which are high impedance. There is really no point in running such large quiescent currents for these headphones. 80mA is far more than enough to keep the amp in class A all the way up to clipping.


----------



## rjkdivin

Does anyone have a clever way to slightly extend the length of the potentiometer shafts to accept knobs with the set screws too far out to engage the shaft fully.


----------



## MisterX

You mean something like a shaft extender?


----------



## amb

rjkdivin, check out these:
http://www.oselectronics.com/ose_p100.htm


----------



## rjkdivin

Quote:


  Originally Posted by *MisterX* 
_You mean something like a shaft extender? 
	

	
	
		
		

		
		
	


	


_

 

Yes...but a very short shaft extender....perhaps 1/4" or so, and without an increase in diameter at the coupling.


----------



## MisterX

Drill and tap the shaft.... and then screw a piece 1/4" aluminum or other stock into it? 

  Quote:


 rjkdivin, check out these:
http://www.oselectronics.com/ose_p100.htm 
 

Nice link AMB.


----------



## rjkdivin

I finally got back to my second M3 housed in the large group buy case to add the Crossfeed from Tangentsoft. It fit in easily and works very well. I used Tangent's rotary switch (4pole/3pos) with silent wiring option so I could line up the rotary with the M3 pots. The listening effects are pleasing with most sources I have tried. It is a fairly subtle amount of crossfeed when you listen to a full stereo signal. To see how much crossfeed you are getting (and to test your assembly), try unplugging one channel input at a time....it is surprising.

 This M3 also uses Tangent's STEPS set to 24.9vdc, using the Amveco 70062 transformer and substituting in the LM338T regulator.

 I thought of drilling and tapping the switch shafts to extend them as you suggested MisterX, but opted for triming the knobs instead.


----------



## Jazper

I should mention I am running high quiecent current settings for the mosfets (140mA/26.5v) and it was clipping a little(a TINY bit) till I changed d1 to a mur820 and added a 1000uF cap in the power supply (bypassed by a 1uf polyester) on the output. Seems to have fixed the problem and added a bit more bass slam. 

 Thinking about raising the voltage (and dropping the current) a little. But it works so I'm not complaining.


----------



## ylshieh

My M3 had finished.
 It works very well with My HD600 now. 
	

	
	
		
		

		
		
	


	



http://www.wretch.cc/album/album.php?id=ned0815&book=1


----------



## amb

ylshieh, very nice work. What power supply are you using?


----------



## ylshieh

Quote:


  Originally Posted by *amb* 
_ylshieh, very nice work. What power supply are you using?_

 

Custom epoxy case Transformer and Ultimate Mini Regulator that I set the voltage at +-13.8V.

 for Ultimate Mini Regulator info:
http://home.kimo.com.tw/ucccap/howtodoUMR.html


----------



## stinn

Here's a pic of my build, it's done just waiting for a case to be built for it. You can see a modified TREAD being used for the power in the background.


----------



## halman

Here is a picture of my semi complete build Im still missing the 100uF Silmic II caps

 The PSU box is ment to stand on edge


----------



## Jazper

Quote:


  Originally Posted by *halman* 
_Here is a picture of my semi complete build Im still missing the 100uF Silmic II caps
_

 


 Have to say, the hammonds look nice 
	

	
	
		
		

		
		
	


	




 - what power supply is that?


----------



## halman

I decided to go with a PSU of my own. It uses a mainsfilter, CLC on the secondary side and a discrete regulator with a stack of LM329 diodes feed by a currentsource. 

 This is how they are ment to stand when finished.


----------



## pabbi1

Finally got around to my 2nd m³ (for AD8610 to contrast to the OPA637 at the Ft Worth meet), and have run into this curiosity:

 PS = 28.0v

 Pins 4->7 = ~25.7v (all channels)

 5R = .500v (all channels)
 9R = 80mv (all channels)

 IG -> OL = .2mv
 IG -> OR = 1.4mv
 IG -> OG = 6.58V YIKES!! (This is with OPA627; it's around 10v with AD8610)

 The attenuator outer case has a wire soldered to IG.

 Thoughts about what this is most likely?


----------



## amb

pabbi1, double check that R2G and R4G are the correct value (1K) and they are properly soldered (with the amp powered off, use a multimeter in ohms mode to verify). Also check R8G+, R8G- and all pins of the OPAMPG socket. From the description your TLE2426 should be ok, but it won't hurt to also verify that the voltage from IG to pin 7 and 4 to each opamp are the same (except reversed in polarity).


----------



## sean-xenos

Hello,

 I have some questions on MOSFET selection for Q1+ and Q1- : 

 Can I use the output voltage of my STEPS PSU (+/- 12V Amveco transformer)
 to test the gate-to-source voltage of the MOSFETs? 

 Are the 100 Ohms 5W resistors mentioned on amb's website correct for this or should it be 200 Ohms?

 Do I have to mount the MOSFETs on heat sinks for testing?

 Thanks for your help


----------



## amb

Quote:


  Originally Posted by *sean-xenos* 
_Can I use the output voltage of my STEPS PSU (+/- 12V Amveco transformer)
 to test the gate-to-source voltage of the MOSFETs?_

 

Yes.

  Quote:


 Are the 100 Ohms 5W resistors mentioned on amb's website correct for this or should it be 200 Ohms? 
 

The 100 ohm resistor value mentioned pertain to a 12V DC supply. Since you will be testing with double (or more) the voltage, you should also increase the resistance to keep the drain current about the same. I suggest using a 270 ohm resistor. Assuming 24V, and Vgs of approximately 4V, that means there will be about 20V across resistor. With a 270 ohm resistor there will be ~74mA of current flowing through the MOSFET. This is close to the target quiescent current of 80mA in the amp, and will cause about 1.5W of power disspation on the resistor.

  Quote:


 Do I have to mount the MOSFETs on heat sinks for testing? 
 

The MOSFET will warm up slightly (about 0.3W dissipation) so you won't need a heat sink. In fact the Vgs will begin to drop as the device heats up (a characteristic of the MOSFET), so you should be consistent in your measurement technique. Either take quick measurements, or allow the same amount of time for each device after power up before measuring.

 My experience with the IRFZ24N/IRF9Z34N is that you will tend to get lower Vgs values in the N-channel devices than the P-channel, but ~0.3V difference is close enough.

 Edit - A tip: even though the Nelson Pass article describes a different way to hook up P-channel devices than the N-channel for measuring Vgs, you can use the N-channel scheme for the P-channel, just reverse the polarity of the power supply leads. This makes the job easier. If you keep the meter connected as-is, the Vgs will read negative, or you could reverse the meter leads too.


----------



## pabbi1

DOH!! I missed 2 pins on the ground socket... and, the AD8610 does indeed sound, well, awesome with the HD600. Another addition to the FT Worth meet.

 Specs:

 No bass boost
 Stepped attenuator
 Sun Sparc 911 case
 Silver wire
 All Mouser parts (save board and transistors - AMBs part shop)


 For those keeping score at home, that's TWO m³ amps (OPA637 & AD8610), with jewelry, for less than $500.


----------



## Jazper

what say we start compiling a list of what opamps sound better with what headphones, in the m3? 

 for instance: 

 The 637/627s sound great with bright headphones like the MS-1s


----------



## MisterX

Quote:


 what say we start compiling a list of what opamps sound better with what headphones, in the m3? 
 

Ummmmmmmmmmmm.......maybe becuse it's all a matter of taste? 
	

	
	
		
		

		
		
	


	



 That and you seem to be forgetting about the role the source plays in all of this.


----------



## Jazper

Quote:


  Originally Posted by *MisterX* 
_Ummmmmmmmmmmm.......maybe becuse it's all a matter of taste? 
	

	
	
		
		

		
		
	


	



 That and you seem to be forgetting about the role the source plays in all of this. 
	

	
	
		
		

		
		
	


	


_

 

you're right... I haven't really woken up yet - cheers for the wakeup call


----------



## stinn

The (near)finished product. My M3 in a custom oak case. I still haven't found the right knob for it but maybe soon.
 Sorry for the quality, the camera I used sucks.


----------



## Jazper

Quote:


  Originally Posted by *stinn* 
_The (near)finished product. My M3 in a custom oak case. I still haven't found the right knob for it but maybe soon.
 Sorry for the quality, the camera I used sucks._

 


 more pics please ! 
	

	
	
		
		

		
		
	


	




 looks good


----------



## bhjazz

Quote:


  Originally Posted by *stinn* 
_My M3 in a custom oak case. I still haven't found the right knob for it but maybe soon._

 

Nice work. To me, that oak in that design is calling for a real retro looking knob. 






 I like the one second row up from the bottom, three in from the left. This is from 
http://www.oldradioparts.com/

 Select Radio Parts, then Knobs.


----------



## stinn

Quote:


  Originally Posted by *bhjazz* 
_Nice work. To me, that oak in that design is calling for a real retro looking knob. 
 [/IMG]http://www.oldradioparts.com/2a18p.jpg[/IMG]

 I like the one second row up from the bottom, three in from the left. This is from 
http://www.oldradioparts.com/

 Select Radio Parts, then Knobs._

 

Interesting, I'll definately keep that in mind. I was thinking retro too, but more 70's/80's retro 
	

	
	
		
		

		
		
	


	




 Everything is done with a silver accent so I was thinking of a 2-2.5" stainless steel or brushed aluminum. 
 I'll try to get some more pictures later, the damn thing takes a while to open, plus I'm enjoying music too much right now to turn it off


----------



## Jazper

Quote:


  Originally Posted by *stinn* 
_I'll try to get some more pictures later, the damn thing takes a while to open, plus I'm enjoying music too much right now to turn it off 
	

	
	
		
		

		
		
	


	


_

 

Enjoy!


----------



## bhjazz

Quote:


  Originally Posted by *stinn* 
_Interesting, I'll definately keep that in mind. I was thinking retro too, but more 70's/80's retro 
	

	
	
		
		

		
		
	


	


_

 

Ah! More Marantz-styled, then! Well, I'll keep my eyes peeled for ya. Have fun!


----------



## stinn

Here's some more pictures, sorry for the, still, ****** camera.

















 The dual rca inputs are actually an input and output. I put in a switchable pass through to allow me to easily output the sound(from my computer) to my home theater. 
 I also must give credit where it is due. My friend did all the PCB soldering and designed and built the power regulator. Another friend built the box(i stained it). All I really did was put it in the box and wire all the switches and it was my first time doing any soldering/electronic wiring.


----------



## Covenant

A random question for all ye m3 builders:

 I'm looking for an opamp with the same (or similar) sound characteristics to the opa637bp, and at least the same amount of bandwidth, but that remains stable at gain level below 5. Does anyone know of one?

 Thanks all.


----------



## silvalis

OPA627? 
	

	
	
		
		

		
		
	


	



 it's the compensated version of the 637.

 oops. lower bandwidth.


----------



## Covenant

Quote:


  Originally Posted by *silvalis* 
_OPA627? 
	

	
	
		
		

		
		
	


	



 it's the compensated version of the 637.

 oops. lower bandwidth._

 

Yup, the bandwidth constriction of opa627 makes it appear sluggish when used with the likes of SA5K. I'm thinking i may need to head into discrete opamp territory


----------



## MisterX

Quote:


 I'm looking for an opamp with the same (or similar) sound characteristics to the opa637bp, and at least the same amount of bandwidth, but that remains stable at gain level below 5. Does anyone know of one? 
 

AD8065
 If you like the OPA637 you are gonna love the 8065.


----------



## amb

Quote:


  Originally Posted by *Covenant* 
_Yup, the bandwidth constriction of opa627 makes it appear sluggish when used with the likes of SA5K. I'm thinking i may need to head into discrete opamp territory 
	

	
	
		
		

		
		
	


	


_

 

I doubt it. The OPA627 has a GBP of 16MHz at unity gain, and at a gain of 20dB still has useful bandwidth over 1MHz. There is no musical content that would approach those frequencies. There are opamps with wider bandwidths out there (e.g., AD8065 with 145MHz GBP, THS4631 with 210MHz GBP) but the difference is sound between these chips are probably not due to the bandwidth.


----------



## Jazper

Quote:


  Originally Posted by *amb* 
_I doubt it. The OPA627 has a GBP of 16MHz at unity gain, and at a gain of 20dB still has useful bandwidth over 1MHz. There is no musical content that would approach those frequencies. There are opamps with wider bandwidths out there (e.g., AD8065 with 145MHz GBP, THS4631 with 210MHz GBP) but the difference is sound between these chips are probably not due to the bandwidth._

 


 how does the ths4631 sound to you amb? in comparison to the 637


----------



## amb

Quote:


  Originally Posted by *Jazper* 
_how does the ths4631 sound to you amb? in comparison to the 637_

 

See my impressions post on this opamp:
http://www6.head-fi.org/forums/showp...8&postcount=23

 The main concern I had was that they run very hot, and the specific units I had was that the DC offset was a bit too high for comfort.

 Your mileage may vary, of course.


----------



## Covenant

Quote:


  Originally Posted by *amb* 
_I doubt it. The OPA627 has a GBP of 16MHz at unity gain, and at a gain of 20dB still has useful bandwidth over 1MHz. There is no musical content that would approach those frequencies. There are opamps with wider bandwidths out there (e.g., AD8065 with 145MHz GBP, THS4631 with 210MHz GBP) but the difference is sound between these chips are probably not due to the bandwidth._

 

If not a bandwidth issue, then it must be some other aspect of the chip. I'm going by what i read here, as spike33 tested opa627 with SA5K and noted the sluggishness. 8065 he notes is much faster, which i concluded had to be a bandwidth issue (considering that seems the most prominent difference between these two chips).

 Tangent had a slightly less positive report of the 8065 though, stating this in his opamp roundup: 

 "This chip kind of splits the difference between the AD8610 sound and the Burr-Brown sound: not aggressive, but not laid-back, either. It's a bit veiled, which is expected given the chip's price."

 Which doesn't make it sound too fantastic. I want something as no-holds-barred as possible, that compromises in nothing and is overkill in every respect - probably impossible i know, but i won't settle for anything less than the best


----------



## skyskraper

unless you have the same ears and equipment as that guy, then your experience is likely to differ markedly.


----------



## amb

Covenant, the only advice I could give you is to do a comparison yourself if possible. Throw out any preceived notions about the sonic characteristics that you might have read from others, and let your own ears be the judge. There is no consensus on what is "no holds barred, compromises in nothing". Many people here are just rehashing what they read from others anyway. Given a proper blind A/B comparison, much of the difference vanishes anyway (Don't believe it? Try it out sometime).

 If you hear something you like better, then you found the right opamp for you. If you can't hear a difference, then pick the cheaper one.


----------



## Jazper

Quote:


  Originally Posted by *amb* 
_ Many people here are just rehashing what they read from others anyway. Given a proper blind A/B comparison, much of the difference vanishes anyway (Don't believe it? Try it out sometime).

 If you hear something you like better, then you found the right opamp for you. If you can't hear a difference, then pick the cheaper one. 
	

	
	
		
		

		
			



_

 


 Agreed, however, there are two differences that had me choose the 637 over the 8610. The 8610's bass seemed recessed, and the highs were piercing. This was with my ms-1s and av710.. so ymmv. I also find the 637 sounds much better after it's warmed up whereas there isn't much difference between the 8610 before and after it warms up in the m3.


----------



## rjkdivin

I just got around to casing up my fourth M3. It's in a Lansing B2H08-V02B case that I was planning to use for just an M3 without a power supply. However, due to its height of 3 1/2", I found it would fit the Welborne PS-1 if I angled the transformer on a custom bracket and mounted the two PCBs at different heights so they could lap over a little. I was a bit concerned about EMI due to the cramped quarters, but it is as clean sounding as my other three, two of which have the PS in a separate case.

 Now, since there is room, I'm considering larger heatsinks for the PS-1 since it is running a little hot with a 15v + 15v toroid.


----------



## amb

rjkdivin, nice case. I am a little concerned about the proximity of the transformer to the input traces too. I know you have the ability to run RMAA tests, so you should do a test of this amp and check the noise spectrum. If there is any interference, you'll see spikes at the AC fundamental (60Hz) and its harmonics. If you don't see any spikes, then all is well. Just fyi.


----------



## rjkdivin

I went back to my first M3 in the Silverstone separate cases to run the RMAA tests, and ran into a problem. In adjusting the signal levels, with volume at full on both the M3 and the M-Audio, and with 330 Ohms on the dummy load box, it only comes up to about -12db....not enough to run a meaningfull test. I re-checked the STEPS output voltage....24.5v, and re-checked all of the initial set-up items...rail voltage, pin 4/7 voltage, IG/OG, R5, R9 +/- from your instructions, and all are perfect. I even swapped in a different set of opamps with no change. The amp plays beautifully. Any ideas why this could be?


----------



## amb

rjkdivin, does this M³ have the default gain of 11 (i.e., R3 and R4 are 1K and 10K ohms)? If the gain is too low then you won't be able to achieve enough output for an RMAA test. That said, I have run RMAA successfully on the M-Audio Firewire Audiophile with amps with gain as low as 4 and it's still sufficient. Check the value of your R4 and R4 resistors just to be sure. Does this amp play equally loud compared to your other M³ builds when connected to the same source and headphones and the volume control set to the same position?

 If that is fine, then something is attenuating the levels in your RMAA testing chain. Are the two channels equally low in level? Try swapping different interconnect cables just in case.

 Edit: actually, even a gain of 1 should be enough because that's what loopback does.


----------



## rjkdivin

AMB,

 Yes, I used default values for everything. I checked the values of R3 (1k). R4 (10K) and R4G (1K) in place. I even pulled out R4G to double check, and they all measured fine.

 I visually verified all other resistors and all capacitors also. I have always been suspicious of C3 at the Mosfets and C1 at the Opamps because the markings didn't match my order with Mouser precisely. So I pulled them all out and they measured as follows:
 C3 - .317nf or 317pf....sounds somewhat close to 220pf? They were labled 221.

 C1 - .123nf or 123pf....about 4 times your design value of 33pf. They were labled 330. Could this be a problem?

 As far as my test set-up, I haven't changed it from one test to the next, and it worked fine on my Par Mtls Separates M3. But just for fun, I switched interconnects, and it made no difference.

 Now I need new capacitors anyway because I ruined one getting it out....terribly small little buggers!

 This guy won't be ready for the HeadFi meet! Maybe just to look at....those Silverstone cases are nice!


----------



## amb

Quote:


  Originally Posted by *rjkdivin* 
_Yes, I used default values for everything. I checked the values of R3 (1k). R4 (10K) and R4G (1K) in place. I even pulled out R4G to double check, and they all measured fine._

 

OK.

  Quote:


 I have always been suspicious of C3 at the Mosfets and C1 at the Opamps because the markings didn't match my order with Mouser precisely. So I pulled them all out and they measured as follows:
 C3 - .317nf or 317pf....sounds somewhat close to 220pf? They were labled 221. 
 

The 3rd digit on these caps is a multiplier. The label "221" means 22pF times 10^1 = 220pF. So it is correct. These are supposed to be 10% tolerance parts, so your measured result is out of whack. I would be suspicious of the measurement rather than the part itself.

  Quote:


 C1 - .123nf or 123pf....about 4 times your design value of 33pf. They were labled 330. Could this be a problem? 
 

Same here: 33pF times 10^0 = 33pF, so it's correct too.

  Quote:


 As far as my test set-up, I haven't changed it from one test to the next, and it worked fine on my Par Mtls Separates M3. But just for fun, I switched interconnects, and it made no difference. 
 

Well I don't know what to tell ya...

  Quote:


 Now I need new capacitors anyway because I ruined one getting it out....terribly small little buggers!
 This guy won't be ready for the HeadFi meet! Maybe just to look at....those Silverstone cases are nice! 
 

Send me email and let me know which caps you need, I could bring a few to the meet where you could do an on-site repair. Just bring a soldering iron, solder and some needed tools along. It would be nice to have all your gear in working condition. 
	

	
	
		
		

		
		
	


	




 Once fixed, we could try doing RMAA testing there. I will be bringing my laptop, M-Audio Firewire Audiophile and other test stuff.


----------



## rjkdivin

Quote:


  Originally Posted by *amb* 
_OK.
 The 3rd digit on these caps is a multiplier. The label "221" means 22pF times 10^1 = 220pF. So it is correct. These are supposed to be 10% tolerance parts, so your measured result is out of whack. I would be suspicious of the measurement rather than the part itself.
 Same here: 33pF times 10^0 = 33pF, so it's correct too.
 Well I don't know what to tell ya...
 Send me email and let me know which caps you need, I could bring a few to the meet where you could do an on-site repair. Just bring a soldering iron, solder and some needed tools along. It would be nice to have all your gear in working condition. 
	

	
	
		
		

		
		
	


	



 Once fixed, we could try doing RMAA testing there. I will be bringing my laptop, M-Audio Firewire Audiophile and other test stuff._

 

Well I rechecked 5 of the 6 capacitors....off the pcb....using a Fluke 187 autoranging. All close to the same: C1 - .123 to .129 nf C3 - .317 to .329 nf.


----------



## amb

Quote:


  Originally Posted by *rjkdivin* 
_Well I rechecked 5 of the 6 capacitors....off the pcb....using a Fluke 187 autoranging. All close to the same: C1 - .123 to .129 nf C3 - .317 to .329 nf._

 

I really think that your meter is not reading correctly. It may not be the meter itself, but perhaps the test leads have some "built-in" capacitance. This makes sense because in both cases it read about 90pF too high.


----------



## tangent

In my experience, my Fluke 189 doesn't do so well measuring below 100pF. I switch over to an AADE LC Meter II for that. But don't feel bad about the Fluke -- it'll go up into the microfarads, where the AADE unit will poop out.


----------



## rjkdivin

Quote:


  Originally Posted by *tangent* 
_In my experience, my Fluke 189 doesn't do so well measuring below 100pF. I switch over to an AADE LC Meter II for that. But don't feel bad about the Fluke -- it'll go up into the microfarads, where the AADE unit will poop out._

 

You and AMB are correct I think. My Fluke 187 with standard leads reads around .095nf, and without any leads its around .078nf......both in the neighborhood of my 90pf error in measuring the caps.

 I have a 199 scope meter, but I haven't tried that yet to see if it makes a difference.


----------



## SiuGuyGuy

Today my m3 suddenly gone no sound. I had check thought it and found that seems the power supply of opamps gone wrong. First i check voltage bewteen pin4 and pin 7 of opamp socket, it got 2.7V. Then I check voltage of pin 7 vs power supply's V- is +23.4V, and Pin 4 vs pwr supply V- is +20.7V. My power supply is 24.5V.

 Is that my TLE2426CLP fired? Or some other possible reason?

 Thanks for help!


----------



## amb

SiuGuyGuy, sounds like your Q5+ and Q5- died. Be sure to use proper "name brand" transistors for these, because I found some "no name" 2N3904/3906 not to meet the specifications. If you use opamps that draw a lot of current (e.g., THS4631D, or even in some cases OPA627/637) these transistors would burn up.


----------



## GregVDS

Hello, I begun now some months ago the DIY headphone amp quest. I made two Cmoys, different (buffered at output, then at input), implementing some Crossfeed filters in. I mainly listen with a Grado SR325i, and nothing else, since all my other headphones are crappy in comparison.

 Now I want to take the big step and build an entire M³, with Linkwitz modified Crossfeed and Tangent Step PSU. I studied a lot the websites of Tangent and AMB, even asked some people on internet, but I still have some questions about details, or maybe more important things, Here I go:

 -First, I want Crossfeed, so, I just put the crossfeed (linkwitz, tangent pcb implementation) in front of the M³ circuit, between RCA and M³ pcb input, right? How will interact the volume pot with the crossfeed? should I buffer the crossfeed between two OpAmp unity gain stages?

 -AMB specific, what is the meaning of "Boutique grade", for Cerafine, very good, or barely ok? (I show my french-speaking-guy limits here, sorry)

 -Consequently, are there big differences between Nichicon UHE serie and Elna Cerafine, for the last ones are difficult to find?

 -Can I use Orange Drop polypropylene rated 200~400v for CBB? Is it worth it?

 -My main music source will be the line out (not headphone jack, the one intended for hifi amp line in) of my 3rd generation iPod. I measure dc offset between right and ground, left and ground, in mV, correct? What amount is tolerable, only nothing, some thenth of mv, some mv?

 -I the same context, How could I tackle down this DC offset if there is one?

 -Can it be possible to lower the 1.5'' heatsink a little bit by sanding out some millimeters of material? which extremity, from the base or the top?

 -I want to use a par-metal case (Thrice could answer me on these ones maybe?) and have a custom one (10'' x 8'' x 2'', hence the heatsink question) what screws are used, and would it be possible to replace front, top and back by top panel express ones? I would like to have them attached from inside, with no screws on the outside. Is it possible to fix the pcb in the box If I want the shafts of volume pot and bass boost pot useful for knob attachement, for the internal aluminium foil chassis is quite large (I need in fact the width and height of the hole in the internal front plate)? Is there some holes in the back plate or not? See the front.jpg here for my layout, any comments welcome

 -Someone heard something about a 'Mark Burson Super OpAmp', with figures at least ten times better than the OPA627, look into ebay, australian product, is this for real?

 -Volt gain is computed from R3 and R4, but for volume pot turned to max, or do I miss something?

 -Why 4 C8, and not 3?

 -Why no R1G?

 -PSU 24V ok?

 -Useful to have an internal metal divider between step and M³ pcb's? Par-metal 20-series has this option.

 -I want to use a 4 pole 3 position rotary switch for Linkwitz; is it possible to position it just above the big M³ inscription on the pcb, or the heatsink is too close to the front panel (having in mind my wish to use the shafts of pots through the front panel)

 -What shielded wire to use, or how to shield a wire?

 for C7, what's better: 9 x 330µF, 6 x 470µF, 3 x 1000µF?

 Ok, that's all I should know for now, many thanks if you're still there.

 I hope to have at least some answers to progress in this.

 Many thanks to all

 GregVDS


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_-First, I want Crossfeed, so, I just put the crossfeed (linkwitz, tangent pcb implementation) in front of the M³ circuit, between RCA and M³ pcb input, right? How will interact the volume pot with the crossfeed? should I buffer the crossfeed between two OpAmp unity gain stages?_

 

If you use the "high-Z" version of the crossfeed circuit then yes, it goes between the RCA input and the M³ pcb input. The volume pot should have little interaction with the crossfeed. Note that the crossfeed circuit will introduce a 6-10dB loss, so depending on your source and headphones you may need to increase the gain of the amplifier to make up for it.

  Quote:


 -AMB specific, what is the meaning of "Boutique grade", for Cerafine, very good, or barely ok? (I show my french-speaking-guy limits here, sorry) 
 

Cerafine is considered boutique-grade. Generally, anything that are labeled specifically "for audio" and then priced significantly above standard stuff are "boutique".

  Quote:


 -Consequently, are there big differences between Nichicon UHE serie and Elna Cerafine, for the last ones are difficult to find? 
 

In the M³, electrolytic capacitors are only used in the power supply rails, not in the signal path. In my opinion there is no advantage of using Elna Cerafine over Nichicon UHE in this application, but don't let me stop you from using the boutique stuff.

  Quote:


 -Can I use Orange Drop polypropylene rated 200~400v for CBB? Is it worth it? 
 

You can use the Orange Drop if you like, as long as it physically fit the board and the leads not too thick to go through the holes. The high voltage rating is total overkill and not needed in this circuit.

  Quote:


 -My main music source will be the line out (not headphone jack, the one intended for hifi amp line in) of my 3rd generation iPod. I measure dc offset between right and ground, left and ground, in mV, correct? 
 

Yes.

  Quote:


 What amount is tolerable, only nothing, some thenth of mv, some mv? 
 

Any DC offset at the input to the amp will be amplified by the gain of the amp (at max volume). The amount of DC offset that is tolerable depends on the type of headphones you have. Lo-Z phones are more likely to be damaged by offset, and I would suggest no more than a few mV maximum at the input of the amp.

  Quote:


 -I the same context, How could I tackle down this DC offset if there is one? 
 

Insert a coupling capacitor, either at the output of the offending source, or at the input of the M³ amp to block the DC.

  Quote:


 -Can it be possible to lower the 1.5'' heatsink a little bit by sanding out some millimeters of material? which extremity, from the base or the top? 
 

If you must grind down the height, do so at the top of the heat sink.

  Quote:


 -I want to use a par-metal case (Thrice could answer me on these ones maybe?) and have a custom one (10'' x 8'' x 2'', hence the heatsink question) what screws are used, and would it be possible to replace front, top and back by top panel express ones? 
 

If you use short standoffs (like 1/8") and apply an insulating plastic sheet below the board to keep anything from touching the case, then the board with 1.5" heat sinks will fit in the 2" tall Par Metal case. However this arrangement will cause your volume/bass boost knobs to be a bit below the center line of the front panel.

 All screws in the Par Metal 20 series are 6-32 thread machine screws. You can replace the front with a custom panel from Front Panel Express but all the other pieces have bends in them. I am not sure Front Panel Express will make such pieces.

  Quote:


 -Someone heard something about a 'Mark Burson Super OpAmp', with figures at least ten times better than the OPA627, look into ebay, australian product, is this for real? 
 

Don't waste your money. It's a scam.

  Quote:


 -Volt gain is computed from R3 and R4, but for volume pot turned to max, or do I miss something? 
 

Yes. When we speak of amplifier gain we imply the volume at max position. The volume control then introduces a loss (from none at maximum to 100% at minimum).

  Quote:


 -Why 4 C8, and not 3? 
 

Its for power rail decoupling. There can be any number of them, and since there is room for 4, we put 4 in there.

  Quote:


 -Why no R1G? 
 

Because R2G already serves that purpose.

  Quote:


 -PSU 24V ok? 
 

Yes.

  Quote:


 -Useful to have an internal metal divider between step and M³ pcb's? Par-metal 20-series has this option. 
 

Yes.

  Quote:


 -I want to use a 4 pole 3 position rotary switch for Linkwitz; is it possible to position it just above the big M³ inscription on the pcb, or the heatsink is too close to the front panel (having in mind my wish to use the shafts of pots through the front panel) 
 

You will have to determine this yourself, based on the dimensions of your switch and how you would mount the board and switch.

  Quote:


 -What shielded wire to use, or how to shield a wire? 
 

If your input wiring is not longer than a few inches then there is no need to use shielded wires. Just twist the ground and signal wires together. If you have longer runs, then use coaxial shielded wires, like a microphone cable.

  Quote:


 for C7, what's better: 9 x 330µF, 6 x 470µF, 3 x 1000µF? 
 

All else being equal, 9x330 would provide the lowest ESR, but all else is not equal even between selections of the same line of capacitors. In reality it is not going to make much difference. We provide holes on the board for those who obsess about these things so they could do what they like.


----------



## White Mike

Wow. Thats getting pretty close to a complete summary of the entire thread so far!


----------



## GregVDS

Ok,

 many thanks AMB for this so complete answer. I will use that, for sure.

 For the input DC offset, I measured my iPod, the headphone output is somewhere around 0.1mV, and the line output is around 0.3mV. These do not move when on internal battery, and fluctuate from 0.2 to 0.4 for the line output when on wall charger. If this is passed through a voltage gain of 5, to a Grado, the headphone will have 1 to max 2 mV through 32ohms, meaning 0.03125 to max 0.0625 mA. Is this a real threat, for the headphone is expensive enough at least to burn them!

 Ok, now if this is too much, I should put a cap inline with the input, now, before or after the Linkwitz pcb? And what kind, and what value? will it interact with the crossfeed or not (surely, but how to minimize this effect)?

 One of my Cmoy (front buffered) have a Linkwitz high-Z implementation, and a gain of 4 to 5, I'm satified with the volume level, can I just assume I will have the same volume level if I stick to a gain of 5 in the M³?

 How can I further fin-tune the M³ for Grado / OPA627, Gain 5, besides 27pF in place of 33pF, are there specific bias settings?

 I want to achieve gain 5 without touching to the R4 (10kOhms), so I need r3 = 2500 Ohms, right? Is it the optimum, regarding current and noise, for 4kOhms and 1kohms work also, and a lot more combinations.

 Many many thanks again, I want to study it and be sure I understand everything and be convinced I can cope with all the aspects before beginning this.

 All the best,

 Greg


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_For the input DC offset, I measured my iPod, the headphone output is somewhere around 0.1mV, and the line output is around 0.3mV._

 

This is low enough not to be a concern.

  Quote:


 One of my Cmoy (front buffered) have a Linkwitz high-Z implementation, and a gain of 4 to 5, I'm satified with the volume level, can I just assume I will have the same volume level if I stick to a gain of 5 in the M³? 
 

Yes. Or, you could keep it at the standard gain of 11, which is only about 6 or 7dB more at max volume.

  Quote:


 How can I further fin-tune the M³ for Grado / OPA627, Gain 5, besides 27pF in place of 33pF, are there specific bias settings? 
 

There are no other opamp-specific settings except power supply voltage. 24V is safe for any of the recommended opamps.

 If you plan to try different opamps in the future then you should keep C1 at 33pF. The difference is small anyway, we're talking about frequency response up to 1.2MHz instead of 1.5MHz, which in either case is rather academic.

  Quote:


 I want to achieve gain 5 without touching to the R4 (10kOhms), so I need r3 = 2500 Ohms, right? Is it the optimum, regarding current and noise, for 4kOhms and 1kohms work also, and a lot more combinations. 
 

10K/2.5K is fine, 4.02K/1K works too. The difference in noise is negligible. However the two require different value of Cbb to achieve similar bass boost control range (assuming 50K pot). Use the bass boost calculator on my site to figure this out.


----------



## GregVDS

Ok,

 I come back to my question about orange drop capacitors. The overrated voltage is all what I found on Mouser. Could someone point me where to find 50V ones as seen on Tangentsoft's website? Are these ones the best, or Solen is better? I try to find very good ones for CBB and crossfeed (0.1 and 0.022µF) as these are in the signal path.

 And also, if someone could point me also to small spacers, screws and stuff like that, I'm interested, is there a special section in Mouser for this?

 I just ordered my M³ pcb, STEP and crossfeed PCB; as soon as I begin to build and solder things, I will post pictures of it.

 Many thanks again for the advices and help.

 All the best,

 GregVDS


----------



## funch

I just got my orders in for my M3. I'm also using 200v Orange Drops in the Cbb position, as well as on Tangent's crossfeed board, and the fit is fine. Hope this helps.


----------



## GregVDS

Ok, thanks, I will so stick to these.

 Logically, a too high voltage is just useless, but it should not be harmful for the sound, right?

 I hope my pcbs will arrive quickly 

 I still don't have any answer from par-metal, are they closed at the moment, or they don't do business with european guys?

 I want a custom 7.5'' depth x 9'' width x 2'' height aluminium 20-series case. I will in the future replace the front panel by front panel express one.

 And by the way, what difference between Anodized and alodined aluminium?

 Many thanks!

 All the best,

 GregVDS


----------



## skyskraper

the best bet with parmetals is to call them or email their ebay store linky another option for you may be one of the cases from thl, they at least reply to their emails quickly


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_Logically, a too high voltage is just useless, but it should not be harmful for the sound, right?_

 

It should have no adverse effect on the sound.

  Quote:


 I still don't have any answer from par-metal, are they closed at the moment, or they don't do business with european guys? 
 

They don't seem to answer emails. You should contact them by telephone (keeping in mind the timezone differences). The telephone number is listed on their web site. I don't know whether they will ship outside of the US, so be sure to ask.

 Update: skyskraper's link to Par-Metal's ebay store "Antek" is the Australian version. Here is the general one. They items offered through the ebay store can be shipped to Europe.


----------



## tess

if its any use to *GregVDS* I've just phoned Par-Metal after many unanswered emails and they don't deliver to the UK.

 Have a look at these cases, http://www.hifi2000.it/default.asp?id=16&mnu=16

 they are available from http://www.audiokit.it/ but are on Italian Hol's until the end of the month.


----------



## amb

Quote:


  Originally Posted by *tess* 
_Have a look at these cases, http://www.hifi2000.it/default.asp?id=16&mnu=16_

 

These look nice, but have an internal height of only 40mm, which is a bit too short for the board with 1.5" heat sinks and standoffs. They offer taller versions but the next step up is 80mm, making it less sleek-looking.


----------



## GregVDS

Thank you for all these answers.

 These boxes from Italy look beautiful and very well finished, better than Par Metal in my opinion, and cost less! But you're right AMB, those 4 cm are very small, but they could go out of the box like lamps. It's just an idea, maybe mad. Surely not the safest way to go. if that darn box could be 5 to 6 cm height and not 4... Sigh

 I still don't find the right enclosure, this is difficult and frustrating, for I cannot build one by myself, lacking the tools.

 Ok, C4, C5, C8 for the M³ and D1 for the STEP seem to be out of stock. How long can it takes?

 I ordered also Ag solder from WBT, I know this is a little bit too much, but I want to do this the best I can. Input will go through WBT-0201 RCA sockets.

 All the best to all of you

 GregVDS

 ps: so there are very few chances Par-Metal will ship to Belgium, I guess...


----------



## Jazper

Quote:


  Originally Posted by *GregVDS* 
_Ok, C4, C5, C8 for the M³ and D1 for the STEP seem to be out of stock. How long can it takes?_

 


 for C8 you could use mouser part no: 505-MKP20.1/100/5 

 As for C4 and C5 you could use mouser part no: 647-UHE1H101MPD 

 and for the steps D1 you can use mouser part number: 512-RHRP860 

 These shouldn't change the sonic characteristics much from the stock parts

 all are currently in stock at mouser


----------



## GregVDS

Ok,

 Many thanks all!

 Tess, these are the most neat and clean box I've seen yet on internet. For sure, as AMB pointed out, the 4cm height is not enough, and the 8cm is too much.

 But I have this idea:

 the galaxy boxes are simply extruded profiles of 4cm height, on wich the front and back panels are attached (4 hex recessed screws each), and on which also the top and bottom plates are attached (4 hex recessed screws each). I think it is quite simple to have whatever width and depth. For height, could it be possible to cut one of the profiles along its longest axis, in order to achieve let's say a height of 5.5cm (enough clearance for the 1.5'' heatsink and under the pcb, still achieving the centering of the knobs vertically on the front face).

 I asked www.hifi2000.it for this, and still don't have an answer. I'm afraid all the site being written in italian, maybe the guys are not familiar with english?

 I plan to replace all the top, bottom, back and front by front panel express ones.

 I need, to plan this, to know the exact dimensions of the STEP v1.2 and the crossfeed pcbs and holes in them. The info is not complete regarding this on Tangentsoft's site. If someone can just measure it and write me down the quotes, I would be very pleased. I presume the quotes given by AMB for the M³ are exact, right?

 Anybody use the www.diycable.com aluminium knobs and remote control volume pcb?


 Ok, hope parts will begin to arrive soon 

 All the best,

 Greg


----------



## Nisbeth

Quote:


  Originally Posted by *GregVDS* 
_Ok,
 the galaxy boxes are simply extruded profiles of 4cm height, on wich the front and back panels are attached (4 hex recessed screws each), and on which also the top and bottom plates are attached (4 hex recessed screws each). I think it is quite simple to have whatever width and depth. For height, could it be possible to cut one of the profiles along its longest axis, in order to achieve let's say a height of 5.5cm (enough clearance for the 1.5'' heatsink and under the pcb, still achieving the centering of the knobs vertically on the front face)._

 

Cutting the profile isn't going to work, as you can't get the case back together again. I can send you some pics to show you what you're up against 
	

	
	
		
		

		
		
	


	




 Replacing the top/bottom (which is steel) and/or the front/rear (which is aluminium) is easy though.

  Quote:


  Originally Posted by *GregVDS* 
_I asked www.hifi2000.it for this, and still don't have an answer. I'm afraid all the site being written in italian, maybe the guys are not familiar with english?_

 

The will reply in english, but they can be a little slow to respond and beside most of southern europe is closed for holidays in august. Be patient 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *GregVDS* 
_Anybody use the www.diycable.com aluminium knobs and remote control volume pcb?_

 

While you're at audiokit.it, check out their selection of knobs as well 
	

	
	
		
		

		
		
	


	



 You can order the volume control PCB that diycable.com sells directly from the designer at electronics.dantimax.dk 
	

	
	
		
		

		
		
	


	





 /U.


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_I plan to replace all the top, bottom, back and front by front panel express ones._

 

If you're going to be doing that, then you might as well make your own custom enclosure.

  Quote:


 I presume the quotes given by AMB for the M³ are exact, right? 
 

The measuerments stated on the M³ pcb dimensional drawing (found in the "Circuit board" section of my M³ site) are exact. You should also be able to get an actual-size printout of the PDF version of the silkscreen layer picture, also on that same webpage.


----------



## GregVDS

Quote:


  Originally Posted by *Nisbeth* 
_Cutting the profile isn't going to work, as you can't get the case back together again. I can send you some pics to show you what you're up against 
	

	
	
		
		

		
			





 Replacing the top/bottom (which is steel) and/or the front/rear (which is aluminium) is easy though.
 /U._

 

Yes, please, I want to see these. How can you know where to send the pics?

 Many thanks for the knobs and remote volume hints also

 All the best

 Greg


----------



## GregVDS

Quote:


  Originally Posted by *amb* 
_If you're going to be doing that, then you might as well make your own custom enclosure._

 

Ok, but how? Assuming I order the six faces, with holes for screw attachment. On which base? I don't have a chassis. Is there a custom chassis society with aluminium plying and hole punching facility outhere where one can ask for one piece?

 Any comment welcome on how to build its own custom enclosure... 

 Many thanks

 Greg


----------



## skyskraper

the place to go to get single custom panels is a local machining shop. yellow pages is your friend. in my experience the guys at my locals have been really cool and helpful. pretty cheap too.


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_Ok, but how? Assuming I order the six faces, with holes for screw attachment. On which base? I don't have a chassis. Is there a custom chassis society with aluminium plying and hole punching facility outhere where one can ask for one piece?_

 

For the top/bottom/side panels you don't really need Front Panel Express, since (I assume) you won't have any markings. Just get a local metal fabricator or machine shop to cut and form sheets of aluminum to size and then you could either prep and paint them, or have them treated in some way (anodize, etc). Then, just join all the pieces together with angle brackets and screws. For the small screw holes you could just drill them yourself.

 You really don't need anything fancy to make an attractive case. My own M³ prototype lives in a home-made case. The base is formed from a piece of sheet aluminum, bent into a U-shape (see this picture, and then I added acrylic side walls, mounted to the aluminum base with aluminum angle brackets and screws. The front and rear panels, also acrylic, are then attached to the side walls with more bracketry. Finally, the top cover is a clear acrylic piece, which screws into the sidewalls. See this picture to see the finished product. More pics from various angles can be found in the gallery section of my M³ site. Instead of acrylic you could do something very similar with aluminum.


----------



## GregVDS

ok,

 Thanks AMB and Skyskraper.

 I will try this way.

 AMB, What shipping method does Elvencraft use to send orders through the website? When will I receive all the stuff?

 I can't stand waiting to begin this 

 All the best

 GregVDS

 ps, where can I find reviews of the M³?


----------



## morsel

Elvencraft ships nothing, as it is my domain name. Send amb private email to discuss shipping issues. Use the search function to find reviews on the M³ in these forums.


----------



## GregVDS

Quote:


  Originally Posted by *morsel* 
_Elvencraft ships nothing, as it is my domain name. Send amb private email to discuss shipping issues. Use the search function to find reviews on the M³ in these forums._

 

Ok, Do apologize me for the confusion, Morsel, I was thinking this was in my order reply email, hence this was shipped so.

 Greg


----------



## Nisbeth

Quote:


  Originally Posted by *GregVDS* 
_Yes, please, I want to see these._

 

See here: 
	

	
	
		
		

		
		
	


	



 You can see how the front (3mm aluminium - rear panel is identical except black anodized) is fixed using countersunk M4-screws. You can replace the front and rear panels easily enough and/or use other screws if you like. You can also see the small countersunk M3-screw that holds the top (1.2 mm steel) in place (bottom is identical). You can replace these panels as well if you like and/or use different screws.





 Now see how the assembly works. The top and bottom is attached to the M3-nut you can see (there's normally two nuts but this is a very small enclosure). This is a standard M3-nut which simply slides into a groove in the side profile. If you cut some of the profile away, you will not be able to fix the top and bottom anymore. The front and rear screws go into tapped holes in the end of the side panels. You could change the length of the sides if you wanted to, as that would only require you to shorten the profiles and then re-tap the holes in one end of the profile.

 Hope this makes sense!


 /U.


----------



## GregVDS

Thanks Nisbeth for your explanations, I let down my idea on the galaxy, though I still think it is possible. I was planning in fact to lower down the height of a 8cm height galaxy box. If you look at it, I think the side panel (extruded ones) are made with two normal extruded piece, each 4cm height. If one cuts each to 3cm height, conserving the parts with the tapped holes for front and rear, I think it is still possible to reassemble the box.

 But as AMB suggested me, it is maybe more meaningfull to build the enclosure from scratch, so, I choose this way: 6 panels from front panel express (too much money at the moment for me, but in a near future), assembled together by aluminium corner profiles. You just have to carefully plan wher to put holes and stuff like that. As soon as it is possible to show this, I will!

 Roughly, I plan to build the M³ with internal psu, in a box 238mm width, 19mcm depth and 63mm height. I cannot go lower than this to and still conserving symetry in the front panel (neutrik, multiswitch for crossfeed, logo, bass boost and volume, each at 1,5 inch of distance to each other), and positioned also in the center vertically (need some clearance on the top of the 1.5 inch heatsinks). I could maybe diminish a little bit the depth, but I need to look if ther is still enough room for mains connector depth, STEP pcb, Linkwitz pcb, and neutrik and multiswitch in front.

 I will post my design, to have comments about it.

 Many thanks for the pictures and explanations again

 All the best

 Greg


----------



## silvervarg

Great reading about the case. Please keep us posted on the development. I will soon have to figure out how to case my M³. Hopefully I can do the setup of the amp in a day or two, except for the bass boast that has to wait since I lack the appropriate capacitors. So, chances are I will be screaming for help soon if I don't get things working at first try...

 The PSU is ready and tested, and all parts on the M³ board except the bass boast and MOSFETS are in place so far. Actually I still have to put on the connectors and possibly the power LED.
 Perhaps I wait with the power LED until I have decided on what case to use.


----------



## funch

Just finished my M3 with a Hagerman Bugle phono board and STEPS incorporated together in the same case. Sort of an M3 integrated amp. All went very well during testing until I measured the DC offset. That's where things are really screwed up! Here's what I got: Left ch. = -1.4 mV: Right ch. = .6 mV: Ground ch. = 0.0 mV. If I flip the leads of my meter on the left channel, then it reads +1.4 mV. What gives? I assembled it very carefully, double checking everything, and followed AMB's setup exactly!!!!


----------



## robzy

funch.... go get a AA battery and measure the voltage. Then swap the meter leads around and measure the battery again.

 Rob.


----------



## skyskraper

its well within the "OK" range for dc offset. you're good to go


----------



## MisterX

Switch the opamps around (left goes in right, right goes in left) and see if the DC-offset stays the same on the left channel. 

  Quote:


 Here's what I got: Left ch. = -1.4 mV: Right ch. = .6 mV: Ground ch. = 0.0 mV. If I flip the leads of my meter on the left channel, then it reads +1.4 mV. What gives? 
 

Nothing wrong with that behavior. 
 The + and - voltages should switch when you reverse the polarity of the meter.


----------



## Dougigs

With regard to ordering silver solder (mentioned by GregVDS): This isn't a big deal one way or another, but silver solder is actually slightly less conductive than good old 60/40. In order to get the 1 per cent silver (which really doesn't melt that easily), they need to drop the tin content and increase the lead content to lower the melting point. And lead is not as good a conductor as tin... So in order to get a tiny amount of silver, you're diminishing the electrical quality of the solder in general.

 The only place where you actually need silver solder is where you're soldering components (i.e. connectors) that have silver-plated contacts. Regular solder has a tendency to wick the silver plating off the contacts, and silver solder preserves it.

 Aside from that application, "regular" solder is actually slightly better electrically, and is easier to work with, and a lot cheaper (though as I said the differences aren't huge).


----------



## Jazper

Quote:


  Originally Posted by *Dougigs* 
_With regard to ordering silver solder (mentioned by GregVDS): This isn't a big deal one way or another, but silver solder is actually slightly less conductive than good old 60/40. In order to get the 1 per cent silver (which really doesn't melt that easily), they need to drop the tin content and increase the lead content to lower the melting point. And lead is not as good a conductor as tin... So in order to get a tiny amount of silver, you're diminishing the electrical quality of the solder in general.

 The only place where you actually need silver solder is where you're soldering components (i.e. connectors) that have silver-plated contacts. Regular solder has a tendency to wick the silver plating off the contacts, and silver solder preserves it.

 Aside from that application, "regular" solder is actually slightly better electrically, and is easier to work with, and a lot cheaper (though as I said the differences aren't huge)._

 


 I've found that silver solder is slightly stronger than normal solder, but both work equally well in my experience.


----------



## Dougigs

Let me follow the above know-it-all answer with a question that betrays my larger ignorance....

 I'm interested in building an M3 -- I have a Sheldon Stokes amp that I built years ago, and it's been the only line-powered headphone amp I've needed... But I'm excited by your design and especially by the great discussions on this thread.

 But here's my question: Why wouldn't it be better to leave out the rail-splitter chip and use a real bipolar supply? I have one that I built for the SDS amp that uses Jung + and - regulators, and to my old-school mind this would be a more solid supply. It would have a genuine ground without a chip in the way... Now, I realize that your rail-splitter chip has a vanishingly low impedance (according to its datasheet), and while it can only handle 20ma, you're not using a ground for the power output (since it's buffered), so that probably isn't a problem. But still, I can see the benefits of rail-splitters for battery powered circuits but it isn't exactly clear to me why they'd be better in a line-powered amp than a conventional centre-tapped, dual-regulated supply.

 But this is probably because my knowledge of such things is woefully out-of-date. The M3 appears to have been designed by some of Silicon Valley's best analog minds, using the latest power-supply design practices. So could one of you just spend a moment laying out the thinking behind the rail splitter?

 Thanks.


----------



## skyskraper

im guessing that when designing it they would have looked to the builders who would be building it. familiarity with building single voltage supplies, plenty of commercially and diy ones available easily. its cheaper to use a single $2 part then to double the number of parts needed for the psu 
	

	
	
		
		

		
			






 oh and most wouldnt be using a jung supply so the tle keeps the ground tracked perfectly halfway between the two rails.

 just my guesses, im sure amb will be along in moments.........


----------



## Dougigs

"will be along in moments..." -- easy for an Aussie to say. It's currently 3AM in northern California, home of the M3. And 11AM here in Blighty, and dinnertime in your neck of the woods. But there's no hurry.

 And you've captured the crux of the question: Is the rail splitter being used to make it easier for builders (in which case I'll leave it out and go bipolar), or is it being used because it actually makes a better tracking regulator than a conventional +/- supply? (especially since this circuit doesn't actually *use* its ground much). I'm willing to entertain arguments either way.


----------



## Jazper

Quote:


  Originally Posted by *Dougigs* 


 

Doug, my M3 is positive jung driven (using P-A's JSR03 design) http://home.swipnet.se/~w-50719/hifi/jsr03/index.html

 Works fine. (pic)
http://photobucket.com/albums/y219/K...t=IMG_0591.jpg

 to quote amb's page:

  Quote:


 Precision virtual ground reference
 Rather than using a conventional split power supply with positive, ground and negative outputs, the M³ amplifier uses a single supply and internally synthesizes a virtual signal ground by using the TLE2426 precision rail splitter chip. This simplifies the power supply requirement, yet provides the advantage of a dual-tracking split supply without associated complexity. The result is improved common-mode rejection ratio (CMRR).


----------



## skyskraper

hah, he's been caught posting later then now 
	

	
	
		
		

		
		
	


	






  Quote:


 Only a single supply is needed. It is not necessary to use a dual (or "split") power supply with positive and negative rails. The single supply is internally split on the M³ circuit board into separate rails, providing a virtual ground centered at one-half of the supply voltage. This simplifies the power supply requirement, provides better common-mode rejection ratio (CMRR), and gives the benefits of a dual-tracking power supply without the complexity. 
 

seems to make brief points for both. 

 i guess most simple/cheaper dual supplies are simply 78XX and 79XX working together, but wouldn't track nicely like a tracking jung would. 

 im a fan of the simplicity of single voltage supplies with a rail splitter myself. 

 for you though, assuming your jung tracks tightly (im sure it would 
	

	
	
		
		

		
		
	


	




 ) i could see why just using that would be the go.


----------



## Jazper

I don't see why you couldn't use a dual power supply.. pull the TLE and have the input ground in the centre pin hole, where the + and - inputs are put the +- power inputs from the supply. 

 I just don't see the point in going to the extent of having a crazy dual power supply when you can half of one and run a TLE chip in this instance and it'd potentially be better.


----------



## Dougigs

Wow, thanks for the pointer to that Swedish web site -- he's got a lot of nifty stuff. If I can just get my head around the kroner-euro-pound conversion rates, I'll order one of those tiny SMD Jung regulator PCBs -- They'd be an easy fit into a small enclosure. His inrush protector is nice, too (not for this -- for my voltage-isolator box, which uses a 1500VA toroid that currently is protected with a big ugly thermistor).

 I'm assuming that the output topology of the M3 does not have a terribly spectacular PSRR, so it's worth our effort to be talking about fancy regulators for it... Again, I'm happy to be proven wrong.


----------



## Jazper

Quote:


  Originally Posted by *Dougigs* 
_Wow, thanks for the pointer to that Swedish web site -- he's got a lot of nifty stuff. If I can just get my head around the kroner-euro-pound conversion rates, I'll order one of those tiny SMD Jung regulator PCBs -- They'd be an easy fit into a small enclosure. His inrush protector is nice, too (not for this -- for my voltage-isolator box, which uses a 1500VA toroid that currently is protected with a big ugly thermistor).

 I'm assuming that the output topology of the M3 does not have a terribly spectacular PSRR, so it's worth our effort to be talking about fancy regulators for it... Again, I'm happy to be proven wrong._

 


 Off topic though, P-A (peranders in this forum - the owner of the website) is really helpful, just read his instructions carefully. 

 ww.xe.com is an easy converter which you can use

 The only main consideration with the regulator is the amount of current the M3 needs, which is about 300mA or so (more if you increase the FET bias, obviously). That being the case, be careful about the heatsinks you use on P-A's regulators, I'm running relatively small ones and they are VERY toasty..

 Should also mention that increasing the capacitance on the output of the regulator, before the M3 has markedly improved response (to my ears), which I find a bit odd.


----------



## Dougigs

Ah yes, good point -- I'd be biasing it very heavily into class A since I'm using 32 ohm Grados, so I think an SMD regulator is out... better to get some big fins up. After all, portability is not the point with this unit.

 I would like to see PSRR figures on the M3, since they could render this whole discussion somewhat moot.


----------



## Jazper

Quote:


  Originally Posted by *Dougigs* 
_Ah yes, good point -- I'd be biasing it very heavily into class A since I'm using 32 ohm Grados, so I think an SMD regulator is out... better to get some big fins up. After all, portability is not the point with this unit.

 I would like to see PSRR figures on the M3, since they could render this whole discussion somewhat moot._

 


 I'm running 120mA bias and it's plenty for anything I've thrown at it. 

 (that makes it about 400mA overall draw) 

 read my thread about my M3 adventures here: 
http://www6.head-fi.org/forums/showthread.php?t=123686


----------



## amb

Although I've never measured the PSRR of the entire amp, I believe it should be very good. Typically the PSRR of the amp is most adversely impacted at the input side, and here we use opamps with already high PSRR, and then added the capacitance multiplier to further isolate the opamp supply rails.

 At the output side, the MOSFETs are biased by sourcing constant current out of the opamp with a pair of cascoded JFETs. Not only does this make the opamp operate in class A, it vastly improves the PSRR of the output stage over the original SDS Labs amp where the bias current flows from the positive supply rail to the negative supply rail through resistors.

 Using the Tangent STEPS PSU (and locating the PSU power transformer far away from the amp board so there is no magnetic hum induction), the noise floor of the M³is very low and free of any spurious power-supply related noise. Thus, I see no advantage of swapping out the TLE2426 and going with a more complex dual power supply.


----------



## GregVDS

Ok, I read all the AMB website, and have quite right in mind the different ways to hook up grounds from input, output, Mains and so on.

 My question is more related to cable shielding.

 Is a simple twisted pair coming from RCA connectors on the backside to the front switch - crossfeed is sufficient (+- 1 foot, 30cm), or should I better opt for the shield-braided cable (like a microphone cable). Is here silver wire interesting, or normal copper is ok?

 Again, form the output R, L and G, should I use two wires from ground to output R and L in order to have twisted pairs from pcb to neutrik jack?

 And also, the output ground is ok for shielding? the input ground is ok for shielding too (since they are not the same)?

 And last, Is there a minimal thickness for internal separation between M³ and PSU pcbs, in terms of aluminium foil I mean. I plan to build a very tight enclosure, to be able to have it with me at work, and come back home with. Hence, the psu and M³ will be very close. I was planning to separate them by an aluminium plyed foil (0.8mm thick), shielding the psu. The outer box will be in aluminium Alodined internally.

 Looking at the dielectric constant of material, I saw Cotton is even better than teflon. Someone use cotton braid as isolant on copper or silver? Is it manageable? I read oxydized copper was rather poor conductor, but silver remains very good, even oxydized. Any comments?

 All the best.

 GregVDS


----------



## Dougigs

That's pretty persuasive. In fact, it seems tempting to try a completely unregulated (but filtered) supply, since between the capacitance multipliers, the rail splitter, the various current sources and the intrinsically low PSRR of the op amp front end, we've got vast amounts of regulation already... An unregulated supply (with, say, a good-sized transformer with 4% regulation, followed by a rectifier and a string of 1000 uf low-esr caps) would have a much lower impedance and maybe give the output stage more bang.

 Has anyone tried this?


----------



## GregVDS

I should check if the one I bought is so, I was thinking it was lead-free.

 WBT silver solder contains 4% of AG. Ag-solder is sonically useless?

 All the best

 Greg


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_Is a simple twisted pair coming from RCA connectors on the backside to the front switch - crossfeed is sufficient (+- 1 foot, 30cm), or should I better opt for the shield-braided cable (like a microphone cable). Is here silver wire interesting, or normal copper is ok?_

 

Simple twisted pairs are good for less than just a few inches. If you go longer than that (such as with crossfeed), then I suggest using shielded cables. I don't really believe in fancy silver wiring inside the case, especially when the distances are so short. Copper is fine.

  Quote:


 Again, form the output R, L and G, should I use two wires from ground to output R and L in order to have twisted pairs from pcb to neutrik jack? 
 

It is not necessary to twist the output wires, but if you want to, you can just twist the three together.

  Quote:


 And also, the output ground is ok for shielding? the input ground is ok for shielding too (since they are not the same)? 
 

You don't need to shield any of the output wiring. For the inputs, if you shield it, just use two shielded cables, one for each channel, and connect the shields together for the signal ground.

  Quote:


 And last, Is there a minimal thickness for internal separation between M³ and PSU pcbs, in terms of aluminium foil I mean. I plan to build a very tight enclosure, to be able to have it with me at work, and come back home with. Hence, the psu and M³ will be very close. I was planning to separate them by an aluminium plyed foil (0.8mm thick), shielding the psu. The outer box will be in aluminium Alodined internally. 
 

Aluminum does not shield against magnetic interference from the power transformer. A ferrous metal may work better, but only if you completely enclose the PSU in a box. There is really no substitute for sheer distance. Assuming you use a low-leakage toroidal transformer, you should still allow at least 4 inches of space between the transformer and the amp board if you want a quiet noise floor. I can't emphasize this enough: It doesn't make sense to build a "maxxed" amp with fancy boutique parts, only to spoil it with hum and noise induced from the transformer. The best solution is to put the PSU in a separate case than the amp and use an umbilical DC power cord, or put it in the same case with a lot of space between the two.


----------



## amb

Quote:


  Originally Posted by *Dougigs* 
_That's pretty persuasive. In fact, it seems tempting to try a completely unregulated (but filtered) supply, since between the capacitance multipliers, the rail splitter, the various current sources and the intrinsically low PSRR of the op amp front end, we've got vast amounts of regulation already... An unregulated supply (with, say, a good-sized transformer with 4% regulation, followed by a rectifier and a string of 1000 uf low-esr caps) would have a much lower impedance and maybe give the output stage more bang._

 

While the PSRR of the amp might be good, I do not recommend an unregulated supply. If you look at the output of such a supply on the scope you'll see sawtooth-shaped ripples that even very large filter capacitances won't cure effectively. Perhaps more important, an unregulated supply will be at the mercy of your AC line's voltage stability. The resultant DC voltage could vary significantly.


----------



## morsel

Quote:


 Is a simple twisted pair coming from RCA connectors on the backside to the front switch - crossfeed is sufficient (+- 1 foot, 30cm), or should I better opt for the shield-braided cable (like a microphone cable). 
 

You should definitely use coaxial cable for the input leads. 1 foot is way too long to go with twisted pair with the added hum and noise source of the power supply inside the amp case. Be sure to position the power supply on the output side of the amp, not the input side, and either space it several inches away, or use a ferromagnetic shield.

  Quote:


 And also, the output ground is ok for shielding? 
 

If you meant, "can I use output ground to shield other signals?", the answer is no, output ground is only for the headphone jack and nothing else.

  Quote:


 Looking at the dielectric constant of material, I saw Cotton is even better than teflon. 
 

Cotton is a poor choice for insulation because it degrades over time. Stick with teflon or PVC.


----------



## GregVDS

Ok,

 So I should let down my one box design and begin to plan a two boxes one. I already made so much different kind of boxes, but only on plan. Ok, let's go again. But you surely are right.

 Thanks again.

 GregVDS


----------



## GregVDS

Thanks Morsel for these, but as AMB and you and all in fact want me to position the psu so remotely from the M³ pcb, this would need a really too big enclosure (4 inches minimum?! sure but the box is nearly 40 cm wide then), so I will now try to plan and build a two boxes enclosure. That's the best way to go it seems.

 Ok, coaxial so, does the kind of mono jack to jack electric guitar cable does the trick, usually, this is a central conductor, in teflon, in ground braid around and pvc out. I was wondering if multi-wires was not as good as mono-wire, regarding skin effect and things like that? does a 22 to 24 gauge mono wire shielded cable exist, apart from stock TV coax antenna cable?

 Thanks for any suggestion,

 All the best

 GregVDS


----------



## morsel

Either a mono coax cable or a stereo coax cable will work. Some people find it easier to use stereo coax cables as wires are easier to attach to the pcb and/or panel jacks than the shield, which can be tied to the ground wire independently. 

 As for positioning the psu, if it is on the output side of the pcb rather than the input side, that is 3 inches from the sensitive inputs already. You can try it out that way before committing to a specific casing choice. There is no way we can tell you in advance how many inches of distance will be required.


----------



## GregVDS

I'm so sorry to ask this, for this is barely acceptable not to know this, but I'm uncertain, and don't want to make any mistakes, so laugh at me, banish me, I really deserve it!

 First (so ashamed):

 I usually use the plastic sheet markings on capacitors to know which leg is the + one, but I know also that one leg is longer than the other. The longer is the + one, right? (recorded laughters here, tomato shots allowed, no: required!)

 Second (idem but a little bit more, if possible):

 After putting a component through the pcb, should I cut the legs before or after soldering them to the pcb? In both case, what lenght is useful, 1mm, 2mm, far less, even longer? (Ok, I'm leaving now, I'm sorry 

 Do accept my apologies for these, ok?

 GregVDS


----------



## GregVDS

Ok, AMB,

 another one then:

 what about the noise collected by this umbilical cable between the psu box and the amp box, this cable should be shielded too, no? The shield should be connected to V-, or ground of the psu box, right?

 And inside the amp box, the signal shielded cable could be stereo one with shield, using the stereo pair for signal + and signal ground, the shield being connected to the ground at the input connector? Is this ok?

 Is a shielding braid which is not connected to ground still shield something, or nothing?


----------



## evo_lution

Quote:


  Originally Posted by *GregVDS* 
_I usually use the plastic sheet markings on capacitors to know which leg is the + one, but I know also that one leg is longer than the other. The longer is the + one, right? (recorded laughters here, tomato shots allowed, no: required!)_

 

Correct on the caps i've looked at- but always double-check the caps markings


  Quote:


  Originally Posted by *GregVDS* 
_After putting a component through the pcb, should I cut the legs before or after soldering them to the pcb? In both case, what lenght is useful, 1mm, 2mm, far less, even longer? (Ok, I'm leaving now, I'm sorry _

 

I always trim them flush after soldering- but hey thats just me 
	

	
	
		
		

		
			





 No apologies needed- we're all new once (i still am 
	

	
	
		
		

		
		
	


	




 )


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_I usually use the plastic sheet markings on capacitors to know which leg is the + one, but I know also that one leg is longer than the other. The longer is the + one, right?_

 

Right.

  Quote:


 After putting a component through the pcb, should I cut the legs before or after soldering them to the pcb? In both case, what lenght is useful, 1mm, 2mm, far less, even longer? 
 

First solder, then cut off the leads flush at the solder joint, no need to leave any excess length of the lead.

 The fact that you are asking this worries me. It's apparent you have not done any PCB work before. I did say on the M³ site that this project is not recommended for the first time DIY'er.

 Before you start building this amp maybe you should practice working on something a little simpler?

  Quote:


 what about the noise collected by this umbilical cable between the psu box and the amp box, this cable should be shielded too, no? 
 

No, there is no need to shield this. I just use a pair of 18-gauge stranded wires, tightly twisted together, and then wrap them in a techflex sleeve, and terminate both ends with barrel-type 2.5mm DC power plugs.

  Quote:


 And inside the amp box, the signal shielded cable could be stereo one with shield, using the stereo pair for signal + and signal ground, the shield being connected to the ground at the input connector? Is this ok? 
 

If you have a wire with two conductors (plus the shield), you could do it one of two ways:
 1. Use one wire to carry everything: the two inner conductors for a L and R signals, respectively, and the shield for the ground connection from the input jacks to the board.
 2. Use two separate wires, one per channel: use one inner conductor for the signal and the other as ground, and connect the shield to the ground wire on one end only.

 The first option has the benefit of less wiring, the second has the advantage of less stereo crosstalk. But since you are going to be artificially adding crosstalk with crossfeed, the "less crosstalk" argument is moot.

  Quote:


 Is a shielding braid which is not connected to ground still shield something, or nothing? 
 

An unconnected shield does not shield against anything.


----------



## GregVDS

Quote:


  Originally Posted by *amb* 
_The fact that you are asking this worries me. It's apparent you have not done any PCB work before. I did say on the M³ site that this project is not recommended for the first time DIY'er.

 Before you start building this amp maybe you should practice working on something a little simpler?_

 

Thank you to be worried, but I already soldered some stuffs: two modified cmoys with crossfeed (meier, ohman and Linkwitz), on protoboard, doing all traces work with legs, everything works perfectly. No, I know how to solder, don't need to be worried by my capabilities here, but I never soldered on a real pcb like the M³ one, so I just wanted to know precisely the way to do it. That was actually how I made for my former amps, put components, bend legs for trace, solder (the less the better) and then cut the legs just near the solder joints.

 For the caps, I just wanted to be sure. Please, be confident, all will be fine!

 Just another question, but on an entire different domain:

 If this is not confidential, how many M³ pcbs did you already sent, just to know if I will have a very common unit or a more rare one. Could it be possible to know our "serial number", just for the fun. I would be pleased to know I have the 23rd, or the 458rd, or the 1.005.587rd, you see? (Mad guy, I know!)

 And how do you all manage to post big pictures here, I tried, but mines are all the time too big or too heavy, and I only manage to attach images through a link, not directly in the message. Explanations welcome (and no, I don't have any html skills, but I can understand it quite easily I think)

 All the best,

 GregVDS


----------



## morsel

Greg, consider studying some electronics basics before plunging ahead with your build. Trial and error on protoboard does not teach good soldering practices or electronics theory. Using Google thusly:

search Google for soldering tutorial
great pdf on soldering
soldering stations
basic soldering guide

 Searching Head-Fi, this site was recommended:

Lessons In Electric Circuits

 Some of the more popular books on electronics include:

*The Art of Electronics* by Paul Horowitz and Winfield Hill
*Troubleshooting Analog Circuits* by Robert Pease
*Practical Electronics for Inventors* by Paul Scherz
*Forrest Mims Engineer's Notebook* by Forrest Mims

 There are no M³ serial numbers. Last I asked, about 150 boards had been shipped. The exact count is not tracked regularly. M³ board distribution is a community service, not a business.

 There is a 25K limit on attachments here. You have to host your own large images and link to them.


----------



## guzzler

Sorry to be contrary here, but I prefer to cut *before* soldering, as 

 a) you get a much neater finish on the board 
 b) you don't need to heat the component as long (as you have a smaller mass to heat) 
 c) and the solder doesn't wick up the leg. (basically why "a" is the case)

 You need to apply a little pressure from the other side to hold it flush, but by no means hard. Most components will actually stay in by themselves, as the leads go into the sockets quite tightly


----------



## sean-xenos

Quote:


  Originally Posted by *guzzler* 
_Sorry to be contrary here, but I prefer to cut *before* soldering, as 

 a) you get a much neater finish on the board 
 b) you don't need to heat the component as long (as you have a smaller mass to heat) 
 c) and the solder doesn't wick up the leg. (basically why "a" is the case)

 You need to apply a little pressure from the other side to hold it flush, but by no means hard. Most components will actually stay in by themselves, as the leads go into the sockets quite tightly_

 






 I second what guzzler wrote.
 Especially with smaller, temperature sensitive components, it doesn't make sense to cut after soldering.


----------



## GregVDS

Ok, thanks for the contradictory advices, it means everybody has its own technique (no offense here to nobody, ok? I'm just more relax! .

 Regarding the temperature sensitive components, I read somewhere over the Headwize project pages that these particularly need theirs legs as some small heatsink while being soldered. But I understand also the need to heat correctly the legs, and this will be achieved quicker if one cuts the leg before soldering. I think it depends of the point of view.

 Really thanks for the comments, I will try my best, both techniques seem to have advantages, and I don't fix my mind at the moment, but, as Mouser takes a long time to come here, I have the time to think about it.

 Morsel, thanks for the very useful links, I read some , specially the first pdf, and though I knew a lot, everything is useful to be known.

 The head of my last solder iron has been disolved it seems, due to poor cleaning, but I have now the correct equipment, and a new solder iron, with fresh pin, that I will take care of 

 All the best,

 GregVDS


----------



## poolorpond12

I thought that I read a post where someone asked about an input buffer. Has anyone done this? My thought is that an opamp before the volume pot would provide a stable input impedance. It would be easy to correct for offset bias too, without altering the amp.

 The only question that I have is if there is enough power in the on board supply for an extra opamp. I was thinking of tapping off the on board supply with a couple jumpers.


----------



## amb

Quote:


  Originally Posted by *poolorpond12* 
_I thought that I read a post where someone asked about an input buffer. Has anyone done this? My thought is that an opamp before the volume pot would provide a stable input impedance. It would be easy to correct for offset bias too, without altering the amp.

 The only question that I have is if there is enough power in the on board supply for an extra opamp. I was thinking of tapping off the on board supply with a couple jumpers._

 

There is enough power onboard for an extra opamp but I am unsure just what "problem" are you trying to solve by doing this? Can you elaborate on what you mean by "provide stable input impedance" (with respect to what?) and "correct for offset bias"?


----------



## PinkFloyd

Quote:


  Originally Posted by *guzzler* 
_Sorry to be contrary here, but I prefer to cut *before* soldering, as 

 a) you get a much neater finish on the board 
 b) you don't need to heat the component as long (as you have a smaller mass to heat) 
 c) and the solder doesn't wick up the leg. (basically why "a" is the case)

 You need to apply a little pressure from the other side to hold it flush, but by no means hard. Most components will actually stay in by themselves, as the leads go into the sockets quite tightly_

 

I second that also. I tend to bend the legs of the component so they make a good "mechanical" connection with the pads _first_ and then I snip the legs flush with the edges of the pad. "Then" I solder which leaves a lovely neat finish, this method of soldering is great if you're going to leave the component in situ and provides a very reliable joint. If you're going to be experimenting with lots of different components (say capacitors) then you may want to adopt the pin witness method amb suggests as it's a lot easier to desolder a component that has been soldered "pin witness" standards.

 BTW, reading this thread (whoah It's long!) and want to build a M3 as it looks like a super amp where can I get a board?


----------



## MisterX

M3 boards are available from AMB's site:
http://www.amb.org/shop/


----------



## GregVDS

I would like to know if someone incorporated VU meters in an M³ build.

 How to do that? take L and R signal, and then after? Assuming the VU meter sensitivity is 0-200µA (130µA = 0VU) and resistance is 250 ohms, what should I do (348-8425 part number RS-components)?

 Thanks,

 GREGVDS


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_(VU meters)
 How to do that? take L and R signal, and then after? Assuming the VU meter sensitivity is 0-200µA (130µA = 0VU) and resistance is 250 ohms, what should I do (348-8425 part number RS-components)?_

 

I guess this depends on what you're trying to accomplish with the VU meters (actually measure something or just for visual amusement).

 If you want to be pedantic, the IEC and ANSI standard for VU meters is to display 0VU at +4dBu (which corresponds to a bit over 1.5Vrms into a 600Ω load). If such a meter is to be connected to the output of a headphone amp, you'd probably find that most of the time it shows little motion at all because the output voltage while driving headphones at average listening levels is far lower than that (see below).

 Therefore, you might say that you really aren't trying to conform to any standard. Then the question is, what should the "0VU" reading mean? Maximum output of the amp? Some arbitrary level where you get the most meter activity?

 Headphone amps can output a very wide range of voltages depending on the situation. The amp is capable of delivering many volts of output prior to clipping, yet depending on the type of headphones you use the "typical" level could be as little as millivolts (for example, the Grado RS-1, a low impedance headphone, is rated to output 98dB SPL with just 1mV, and that's quite loud). Higher impedance headphones tend to require higher voltage to reach the same loudness. Headphone sensitivities also vary from model to model, so at the very least we're talking 2 to 3 orders of magnitude difference in voltage levels between those extremes. That's over 60dB of dynamic range.

 The meter you specified has only a usable display range of just a bit over 20dB. If you set the meter up to get a useful range of motion (for whatever it's worth) with a Grado, it might be quite a useless range for a Sennheiser.

 As such, I think it should be clear that VU meters on a headphone amp are of dubious value.

 As for the particular VU meter you linked to, it doesn't look like a proper VU meter (good VU meters are a lot more expensive than that). I defer you to the following site for more info (courtesy of Elliott Sound Products) about VU meters and their drive circuitry:
http://sound.westhost.com/project55.htm


----------



## GregVDS

Ok,

 So no interest in a headphone amp because of the very different output levels!

 I was sudden nostalgic of these moving needles, I was fascinated by them when I was kid.

 If I follow correctly, one should callibrate the circuit powering the VU for a given headphone, based on its sensitivity and impedance? and if we want to display Volt, the needles will practically never move.

 It was just a bad idea 

 GregVDS


----------



## skyskraper

i would have thought with a vu meter that running it before the headphone amp would be the go. there are a few circuits out there for driving meters.


----------



## GregVDS

This would be nice, but the VU meter would only reflect the dynamic of the signal, not the dB.

 This is nevertheless a great idea, I will continue to think about it.

 thanks for the suggestion!

 GregVDS

 ps: I received the Mouser pack today, and have practically everything. I only miss the L1 for the STEPS PSU, and forgot the crimp terminals for the molex connectors, I was thinking the connector was already equiped with. I will begin the solder as soon as possible but I'm stuck at a conference all the end of this week, and the WE seems already full, so, nothing before next monday I fear


----------



## skyskraper

ok it was late and id had a long day. run it before the amp section but run it from the output of the pot. iirc the few vu meter circuits i looked at when i was considering doing this had the ability to calibrate via a trimpot the gain/response/whatever of the meter. again it wouldnt be accurate. i gave up when i realised that accurate meters would cost nearly as much as the rest of the amp


----------



## MisterX

Quote:


 i gave up when i realised that accurate meters would cost nearly as much as the rest of the amp 
	

	
	
		
		

		
		
	


	



 

Unless you go for one of the annoying flashy led level meter things..... those are pretty accurate and very easy to implement.


----------



## skyskraper

even they wouldnt be as accurate as a proper BBC specced peak program meter.... thats what i want


----------



## MisterX

Quote:


  Originally Posted by *skyskraper* 
_even they wouldnt be as accurate as a proper BBC specced peak program meter.... thats what i want 
	

	
	
		
		

		
		
	


	





_

 


 It's all for visual entertainment anyhow.....


----------



## skyskraper

thats why i ended up putting one of those nightrider dancing led kits on there with pink blue and purple led's. so pwettty 
	

	
	
		
		

		
		
	


	




 /sarcasm


----------



## Dougigs

One thing that would be worth your time, and might provide useful information, is a clipping indicator:

http://sound.westhost.com/project23.htm


----------



## amb

Quote:


  Originally Posted by *skyskraper* 
_ok it was late and id had a long day. run it before the amp section but run it from the output of the pot._

 

The input impedance of the VU meter should be very high or you'd be introducing an undesirable load at that point in the circuit. If the meter is passive (i.e., containing nothing more than rectifier diodes and the meter coil itself) then it would definitely not be suitable. A separately amp'ed meter drive circuit would be ok, but be aware that the node just after the volume pot in is the most sensitive point in the amp (to noise interference and stereo crosstalk), so be very carefully about adding extra wiring or components there.


----------



## Jazper

I couldn't help but tinker.. it's in my nature..

 Today I pulled the C2 caps from my M3 (which were 1uF wima MKS)

 A few things to report: 

 1. the offset has dropped (from 10mV on both channels to about 7.3mV) on the otherwise high offset ths4631D chips, which still run hot
 2. the noise floor has dropped (the hiss as heard from the headphones) -there is more "blackground"
 3. The soundstage has greatly opened up and the imaging is better
 4. The amp sounds more neutral, and has more bass impact. 
 5. The amp seems faster than it was. 
 6. The amp sounds clearer, as if it had a cold before and doesn't have it anymore.

 Now before everyone goes and pulls their C2 caps, the main reason I thought to do so is because Morsel did say a while ago that she couldn't hear the difference, and I've heard lots of "bad things" about having caps in the signal path.

 I don't think I'm in the "golden ears" club, but I know what sounds good, and this sounds good.

 So I pulled them, and I'm happy with the result.

 Setup in my sig.


----------



## morsel

Wima MKS caps are polyester film. If you are going to populate C2, try using MKP polypropylene film. .1µF should be adequate, so you can use the same caps as for C6. While you are at it, you can use them for C8, if you use C8 at all.

 amb, any reason why polyprolylenes are not listed for C2 and C8 on the parts list page? It seems worthy of a note. Also, C6 can be polyester instead of polypropylene.


----------



## Jazper

Quote:


  Originally Posted by *morsel* 
_Wima MKS caps are polyester film. If you are going to populate C2, try using MKP polypropylene film. .1µF should be adequate, so you can use the same caps as for C6. While you are at it, you can use them for C8, if you use C8 at all.

 amb, any reason why polyprolylenes are not listed for C2 and C8 on the parts list page? It seems worthy of a note. Also, C6 can be polyester instead of polyprolylene._

 

Well on the original parts list by nate, and on the page, polyester film were recommended. In my amp I just dropped in 1uF MKS wimas for C8 and C2. I don't think there'd be THAT much difference with C8 being polyprop over polyester, however after what I'm seeing here now if you're going to populate C2, then I'd say you should use something high quality(polyprop or better). Right now I don't see the point in putting a cap there..

 Isn't general theory that caps in the signal path = bad?


----------



## morsel

C2 spans the Vbe multiplier, theoretically assisting it in maintaining a constant voltage between the MOSFET gates. To the extent that the Vbe multiplier is doing the job, C2 is superfluous, since they are in parallel. Is C2 in the signal path? Sort of, but not in the same way that an input coupling cap would be in the signal path. C2 has a very minor influence on the amp, since the Vbe multiplier does a pretty good job.


----------



## amb

Quote:


  Originally Posted by *morsel* 
_amb, any reason why polyprolylenes are not listed for C2 and C8 on the parts list page? It seems worthy of a note. Also, C6 can be polyester instead of polypropylene._

 

C2 and C8 are specified to be MKT or MKS2 because the Wima MKP2 series metallized polypropylene box caps only go up to 0.33µF. For these purposes a metallized polyester is just fine.

 Jazper, if there was a DC offset and noise floor change by pulling C2, then something is not right with your amp. That cap should have absolutely no influence on DC offset or noise. While RMAA test shows no difference with or without it, and I did not observe a discernable difference in square wave response at the output, nevertheless my tests are limited and are not likely to show all the intricacies. It is common practice to bridge the bias network with a capacitor to improve its performance at high frequencies, and I do not recommend removing C2.


----------



## morsel

amb, .1µF should be fine for C2 and C8. I think it's worth mentioning the polypropylene option on your web site.


----------



## Jazper

well all the voltages, resistances and capacitances measure out ok, don't know what could be wrong here...


----------



## silvervarg

Quote:


 Jazper: well all the voltages, resistances and capacitances measure out ok, don't know what could be wrong here...

 ...ths4631D chips, which still run hot... 
 

This sound like the OP-amps are oscillating to me, but its just a guess.
 I would turn bass boast to zero or bridge Sbb and then check C1 and R4.
 What type of cap did you use for C1 and what value?
 Have you tried with other OP-amp brands? Do they also get hot?


----------



## Jazper

Quote:


  Originally Posted by *silvervarg* 
_This sound like the OP-amps are oscillating to me, but its just a guess.
 I would turn bass boast to zero or bridge Sbb and then check C1 and R4.
 What type of cap did you use for C1 and what value?
 Have you tried with other OP-amp brands? Do they also get hot?_

 

urm, even amb noticed that when he tried the ths4631Ds that they run hot, they draw about 11.5mA quiescent - there is also a reason that there is a version with a "powerpad" - heat seems likely.

 I don't think they're oscillating


----------



## fyleow

This might seem like a trivial question but what kind of standoffs are suitable for the board? I checked AMB's site for parts list but it doesn't list any specific item numbers.

 If someone could list some item numbers that would work I'd really appreciate it. Thanks


----------



## amb

Quote:


  Originally Posted by *fyleow* 
_This might seem like a trivial question but what kind of standoffs are suitable for the board? I checked AMB's site for parts list but it doesn't list any specific item numbers.

 If someone could list some item numbers that would work I'd really appreciate it. Thanks 
	

	
	
		
		

		
		
	


	


_

 

A lot of different standoffs are appropriate, it depends on what kind of enclosure you're going to mount the board in and how high you want to elevate the board off the bottom. I see that you're in Cupertino, the best place for something like this is HSC Electronics (aka Halted) in Sunnyvale. They have a large selection of these and various associated hardware at cheap prices. Just go there and get what you need.


----------



## fyleow

Quote:


  Originally Posted by *amb* 
_A lot of different standoffs are appropriate, it depends on what kind of enclosure you're going to mount the board in and how high you want to elevate the board off the bottom. I see that you're in Cupertino, the best place for something like this is HSC Electronics (aka Halted) in Sunnyvale. They have a large selection of these and various associated hardware at cheap prices. Just go there and get what you need._

 

I've actually moved north to Hayward now unfortunately 
	

	
	
		
		

		
		
	


	




 I miss the central location of Cupertino (3 Fry's within ~15 minutes) but housing here is cheaper.

 I have a bunch of standoffs used for motherboards so that might work, but it's good to know I can get them locally too. Thanks for the info.


----------



## GregVDS

Hi,

 I had the (practically) last pack from Mouser, and began to build.

 Just to be sure I can do it, I began the STEPS first rather than the M³. I cut legs before solder. The components fit thightly enough for this, and this permit to heat very rapidly the component lug and the pcb hole. Very nice finish.

 For the ones that have built it, in the STEPS, the Tantalum C7 is polarized, right? Ther is a + hole on the pcb, but no longer leg on C7. On the yellow drop, there is a kind of upside down L sign. This one points down to the + leg?

 How much of silicone grease should I put, practically nothing, the less the best, or there is need for at least a drop of it?

 The wire I usually use tend to brake just after the solder joint after some movement. Why is that so? Is this all the time the case, or my wire is a bad quality one? I read it depends also how you remove the pvc sheet (I pay attention, but I touch the copper with my cutter, is it enough to damage the wire?).

 Thanks,

 All the best,

 GregVDS


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_(STEPS) the Tantalum C7 is polarized, right? Ther is a + hole on the pcb, but no longer leg on C7. On the yellow drop, there is a kind of upside down L sign. This one points down to the + leg?_

 

Yes tantalum caps are polarized. Usually there should be a '+' mark next to the positive lead, but depending on the brand of the capacitor the actual marking might vary (e.g., possibly the negative lead is marked instead with a '-').

  Quote:


 How much of silicone grease should I put, practically nothing, the less the best, or there is need for at least a drop of it? 
 

Just a little is enough. Too much and you will have it oozing out the sides when you screw the part on the heatsink and it's messy.

  Quote:


 The wire I usually use tend to brake just after the solder joint after some movement. Why is that so? Is this all the time the case, or my wire is a bad quality one? I read it depends also how you remove the pvc sheet (I pay attention, but I touch the copper with my cutter, is it enough to damage the wire?). 
 

If you are not using a proper wire stripper tool and you cut too hard, the copper conductor of the wire becomes nicked and becomes easy to break. Also, solid core wires become stressed when you bend them around and will eventually break, so avoid doing that.


----------



## GregVDS

Thanks AMB,

 I checked the spec sheet, I used a kemet tantalum T35 serie, and yes the upside down L is completed by a tiny + near one of the leg. Everything is ok at the moment 

 Tonight, I finish the PSU I think (heatsink, big caps and toroidal transfo, and cabling). I will maybe go slow, to avoid any stupid errors, as desoldering something gives me nightmares.

 I realized I ordered 9 x 330µF nichicon UHE for M³ C7, hence I can have as much as 2970 µF (I know, +- 10%). Is this not too much? Should I put only 6 (1980 µF)?

 I followed the C2 C8 discussion, I stick to the plan so, yep? There is no need to avoid or change these, maybe polypropylene 0.1µF in place of C2?

 what's the name of the tiny bits that are pushed in the heatsink taping holes of the STEPS, that are used to be soldered on the pcb to fix the heatsink, and can I find these alone?

 I read again the initial setup, is it not dangerous to lead-test R9 being so close to the heatsinks (V+ right?) What if a short between V+ and R9 either before or after?

 Should I use multistranded wires for voltage and mains?

 And how do you heatshrink the heatshrink? I always end burning it.

 AMB, Close to the C8 close to the D1, there are two holes not used, one could take V+ and ground from there?

 What is the best way to clean the solder iron tip, the humid foam - sponge, to sand it a little bit before heating it, a kind of white stone similar to Alun or something like that?

 Thanks for all,

 GregVDS


----------



## Jazper

Quote:


  Originally Posted by *GregVDS* 
_I followed the C2 C8 discussion, I stick to the plan so, yep? There is no need to avoid or change these, maybe polypropylene 0.1µF in place of C2?


_

 

if you followed my tip earlier, the capacitors you ordered for c8 and c2 will be 0.1uF polypropylene so you have nothing to worry about there


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_I realized I ordered 9 x 330µF nichicon UHE for M³ C7, hence I can have as much as 2970 µF (I know, +- 10%). Is this not too much? Should I put only 6 (1980 µF)?_

 

9 x 330µF is fine.

  Quote:


 I followed the C2 C8 discussion, I stick to the plan so, yep? There is no need to avoid or change these, maybe polypropylene 0.1µF in place of C2? 
 

1µF MKT or MKS will work fine, so will 0.1µF MKP.

  Quote:


 what's the name of the tiny bits that are pushed in the heatsink taping holes of the STEPS, that are used to be soldered on the pcb to fix the heatsink, and can I find these alone? 
 

Those are pins. The heatsink that tangent specifies for the STEPS come with them pressed in, and you solder the heatsink to the board. For the M³, I supply heatsinks without pins. I suggest using M3 screws (either self-tapping or machine screws. If you use machine screws then you need to tap the heatsinks). Screws rather than solder makes the heatsinks easier to remove if you ever need to do so.

  Quote:


 I read again the initial setup, is it not dangerous to lead-test R9 being so close to the heatsinks (V+ right?) What if a short between V+ and R9 either before or after? 
 

Just be very careful with your test probes when you do this.

  Quote:


 Should I use multistranded wires for voltage and mains? 
 

I do, but it's up to you what you want to do. Just make sure to insulate all connections, leave no exposed high voltage AC mains anywhere. Use plastic-shrouded push-on lugs for the IEC AC module and power switch wiring (and/or heat-shrink tubing). Make sure everything is physically secure.

  Quote:


 And how do you heatshrink the heatshrink? I always end burning it. 
 

There are special heat guns for this purpose. They look like hair dryers but produce a more focused flow of hot air. Some have a temperature adjustment switch.

  Quote:


 AMB, Close to the C8 close to the D1, there are two holes not used, one could take V+ and ground from there? 
 

Those are large vias to connect traces between the top and bottom pcb layers. They are actually the V+ and V- lines, not ground.

  Quote:


 What is the best way to clean the solder iron tip, the humid foam - sponge, to sand it a little bit before heating it, a kind of white stone similar to Alun or something like that? 
 

Don't sand your soldering iron tip if it's good quality. You'll ruin it. Just clean by wiping on a damp sponge when it's hot.


----------



## GregVDS

Thanks,

 I finished the STEPS yestereve. All is working fine. I hope to begin the M³ this evening. The most annoying part was the soldering of the heatsink 'legs'. Heatsink actually sinks you guess what? Heat, so it's almost all the time not hot enough for correct soldering. I had also a hard time putting the common choke filter. I went for the big one (in tangentsoft website list), and with the Mouser C1/C3 just close, legs where not perfectly aligned, but pushing a little bit did it, though the choke is not perfectly levelled to pcb.

 Is there an order to assemble the pcb? I mean, more detailed than from low profile to high profiles? I think mainly of access problem to holes while soldering. Some components are to be placed first to avoid their legs be behind other already soldered very close? I don't know if I'm very clear here, sorry for that.

 I already tap the 6 heatsinks with a self-tapping screw 4-94 or something like that. I think this is safer to do that before assembly, in order to avoid ruining the almost finished M³ with a very long and hard screwdriver slip, SKKRATCH, oups .

 I promise you I will try to post pictures, but I still don't understand how people here put in their message directly seeable pictures wider than 1000 pixels.

 All the best,

 GregVDS

 ps Jazper: don't be angry for I stick to AMB specs, I think the best way to begin is to do the normal layout, listen to it long enough to know its characteristics, then go for modding, and compare and evaluate changes. If I straight go for 0.1µF, How can I say if it's better, or even worth it? Anyway thanks for advices and comments!


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_The most annoying part was the soldering of the heatsink 'legs'. Heatsink actually sinks you guess what? Heat, so it's almost all the time not hot enough for correct soldering._

 

I don't know what kind of soldering iron you have, but this is a good reason why a adjustable-temperature soldering station is a good idea. For fine PCB work you could use just enough heat to do the job without damaging the part of the board, while soldering big items like that you could crank up the heat.

  Quote:


 Is there an order to assemble the pcb? I mean, more detailed than from low profile to high profiles? I think mainly of access problem to holes while soldering. Some components are to be placed first to avoid their legs be behind other already soldered very close? I don't know if I'm very clear here, sorry for that. 
 

Basically, the lowest profile parts go on first, then work your way up. Sometimes it helps to have a piece of foam or something that you could put over the part to keep it fully seated while you solder the part in with the board upside-down. If the part has more than two pins, you could lightly tack-solder just two opposing pins to "seat" the part all the way in, and then do the formal soldering of all the pins.

  Quote:


 I still don't understand how people here put in their message directly seeable pictures wider than 1000 pixels. 
 

Don't post any images that wide, because it won't fit in the window completely on many people's computer screens. Shrink it down to 800 pixels or smaller.


----------



## GregVDS

Ok,

 just to let you know, I nearly finished the amp. The STEPS is finished and works fine. I just have C4 and C5 to solder (and the crossfeed, but this can be done after initial setup). 

 I nearly died yesterday evening. I just had finished to solder the C7 and assembled and soldered the 6 mosfet. I smoke a pipe in the garden, simply happy (poor unknowing guy), when I suddenly remember the mosfets are not identical!! I had 3 time half the chance the 34N and the 24N being in the right places: Ground channel, ok, left channel, ok, could it be I have chance, right? Wrong!! I had to desolder (silver solder) the two right mosfet to exchange them. Now I will never let you see the bottom of the pcb! I was sad about that, for I knew it, I should have taken all the papers and reread them again, even to solder C7, or mosfet pairs. I only hope now I made it right, and everything is just fine. I hope tonight to put C4 and C5 in place, and make the initial setup.

 AMB, if I burned a mosfet, how will the amp react, or how can I check they are ok now?

 Many thanks, apart from this, everything just went fine.

 All the best,

 GregVDS


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_I smoke a pipe in the garden, simply happy (poor unknowing guy), when I suddenly remember the mosfets are not identical!!_

 

You aren't the first to make this mistake. 
	

	
	
		
		

		
			




 At least you remembered and understood that there was the problem before you applied power... (or so your description seems to indicate)

  Quote:


 AMB, if I burned a mosfet, how will the amp react, or how can I check they are ok now? 
 

If you never powered the amp on and fixed the mistake, then it's probably fine. Actually, the MOSFETs have internal reverse diodes between the drain and source pins, so if you had the wrong devices installed it will appear shorted across the power rails and cause your power supply to shut down. If any MOSFET is damaged then you won't be able to get a good DC offset measurement during initial setup.


----------



## GregVDS

No power applied, since C4 and C5 are still absent. And even at that point, now I know I will double-check everything, after having removed the rosin with isopropanol and teethbrush!

 Can I majke the initial setup without the output jack soldered, nor the rca connectors, nor the crossfeed at the input? I mean, Can I make the setup with just the led and voltage supply evidently)?

 I had also a question about the setup. Steps have to be done repeatedly for ground, left and right. For left, can I let the ground opamp in place, or should I remove it, and again, for the right, can I let ground and left in place, or should I again remove the others?

 Thanks again.

 GregVDS


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_Can I majke the initial setup without the output jack soldered, nor the rca connectors, nor the crossfeed at the input? I mean, Can I make the setup with just the led and voltage supply evidently)?_

 

Yes.

  Quote:


 I had also a question about the setup. Steps have to be done repeatedly for ground, left and right. For left, can I let the ground opamp in place, or should I remove it, and again, for the right, can I let ground and left in place, or should I again remove the others? 
 

Once you've completed setup of a channel, you don't need to remove the opamp for that channel.


----------



## rreynol

Just about done with my M3 amp. 











 All thats left to do is trim the pot shafts. I would have liked more lighting of the interior but I didnt feel like adding a 3rd or 4th LED. The two that are in there are 8000 mCD 3.5V 5mm's running with aboutr 13mA through each (they are rated up to 30mA). Its enough to let me know that the amp is powered on so they serve their purpose. I'll be putting together a matching STEPS in a 1455N16 but I think I'm gonna take a break from DIY-ing for a while.

 P.S. pic quality isnt the best. My digital camera is old.


----------



## Jazper

Quote:


  Originally Posted by *rreynol* 
_Just about done with my M3 amp. 


 All thats left to do is trim the pot shafts. I would have liked more lighting of the interior but I didnt feel like adding a 3rd or 4th LED. The two that are in there are 8000 mCD 3.5V 5mm's running with aboutr 13mA through each (they are rated up to 30mA). Its enough to let me know that the amp is powered on so they serve their purpose. I'll be putting together a matching STEPS in a 1455N16 but I think I'm gonna take a break from DIY-ing for a while.

 P.S. pic quality isnt the best. My digital camera is old._

 

Looks good, what do you think of how it sounds?


----------



## Vladco

Rreynol which case you are using? Is it standard hammond case?
 Vlad


----------



## amb

Quote:


  Originally Posted by *Vladco* 
_Rreynol which case you are using? Is it standard hammond case?
 Vlad_

 

Looks like a Hammond 1455T2202. The 1455T2201 will also work.


----------



## rreynol

Quote:


  Originally Posted by *Jazper* 
_Looks good, what do you think of how it sounds?_

 

My good cans (DT770) are at work. Won't get to try those out til tomorrow. I'm sure my portapros don't do the m3 justice but it sounds excellent.



 Amb is correct. Its the Hammond 1455T2202 (Mouser now stocks the larger sizes of Hammond cases)


----------



## phobus

I was re-wiring my M3, and put everything back together, but now...

 With the Ground opamp out, the voltages measure fine. Once I put the opamp in, the voltage between pins 4 and 7 read 6.5 volts, and the power supply gets REALLY hot (its not the opamp, I tried other ones).... This doesn't happen with the L/R opamps so I'm guessing I blew something out in the ground channel. Is there anything to check for, or should I start replacing components?

 Thanks


----------



## amb

Quote:


  Originally Posted by *phobus* 
_I was re-wiring my M3, and put everything back together, but now...

 With the Ground opamp out, the voltages measure fine. Once I put the opamp in, the voltage between pins 4 and 7 read 6.5 volts, and the power supply gets REALLY hot (its not the opamp, I tried other ones).... This doesn't happen with the L/R opamps so I'm guessing I blew something out in the ground channel. Is there anything to check for, or should I start replacing components?

 Thanks_

 

Don't start replacing anything just yet. The symptom sounds like some MOSFETs are simply over-biased and passing too much current.

 With the power off, first try turning the BIAS trimpots of all channels to the fully-counterclockwise position and the BIASOP trimpots to the middle of their travel, remove the L/R channel opamps, then re-do the initial setup procedure found on the M³ website. See if that is successful.


----------



## adhoc

Quote:


  Originally Posted by *sean-xenos* 
_






 I second what guzzler wrote.
 Especially with smaller, temperature sensitive components, it doesn't make sense to cut after soldering._

 

imo most importantly, cutting *before* soldering reduces the chance of a _fractured_ solder joint. ime the _mechanical shock _ (think 'snip!') of cutting a long lead off a completed joint is sometimes too much. ymmv.


----------



## Voodoochile

Nice looking work, rreynol.


----------



## Teerawit

nevermind


----------



## phobus

Quote:


  Originally Posted by *amb* 
_Don't start replacing anything just yet. The symptom sounds like some MOSFETs are simply over-biased and passing too much current.

 With the power off, first try turning the BIAS trimpots of all channels to the fully-counterclockwise position and the BIASOP trimpots to the middle of their travel, remove the L/R channel opamps, then re-do the initial setup procedure found on the M³ website. See if that is successful._

 

Unfortunately its still showing those symptoms... Any ideas?


----------



## amb

Quote:


  Originally Posted by *phobus* 
_Unfortunately its still showing those symptoms... Any ideas?_

 

Well then it's time to test the board for problems. Since you say that the L/R channels are ok, and only the ground channel is exhibiting a problem, then it should be easy to use the L/R side as reference. With the power off (and all rail caps completely discharged), check each MOSFET in your DMM's ohms mode between the drain and source pins to see if there are any shorts. Check the Q2G transistor between the B-E junction, B-C junction and the C-E junctions and compare against Q2L and Q2R. Check the Q3G and Q4G JFETs similarly. Basically, see if you could find any obvious difference between the ground channel and the other channels (except where they are supposed to be different, see the schematic).

 Also, it would be a good idea to examine the board very carefully to see if there are any bad solder joints, solder bridges, shorts, charred parts, etc.


----------



## poolorpond12

I have started trouble shooting my amp and get +25v and +12v at the rail splitter. This corresponds to the same voltages on pins 4 and 7 at the opamp. The steps power supplies about 36v unloaded. I have been sneaking away from the new baby to build this and have not had much time to spend with this. Any thoughts?


----------



## n_maher

Quote:


  Originally Posted by *poolorpond12* 
_I have started trouble shooting my amp and get +25v and +12v at the rail splitter. This corresponds to the same voltages on pins 4 and 7 at the opamp. The steps power supplies about 36v unloaded. I have been sneaking away from the new baby to build this and have not had much time to spend with this. Any thoughts?_

 

First, turn the STEPS down, a lot! As I learned (the hard way) there is absolutely no need to run with that much voltage. It serves virtually no purpose and can only complicate things. 

 Second, where exactly are you taking the measurements from? You say at the rail splitter but do you really have the board flipped upside down and you're measuring the TLE pins? If so, BE CAREFUL. That's an easy place to short something. Also, measure the resitance from pin to pin on the TLE and report back, it could be that you already fried it and it's internally shorted. 

 Finally, from the sound of it you've got a short somewhere on your board. The only way that I can see to get positive volts into the negative rail is to have a short. After spending as much time pouring over my PPA that's really all I can come up with (I experienced similar issues as you with that amp). If you've got a flatbed scanner scan the bottom side of the board and look at it very closely, or post the image and let us look at it.

 HTH,

 Nate


----------



## amb

Quote:


  Originally Posted by *poolorpond12* 
_I have started trouble shooting my amp and get +25v and +12v at the rail splitter. This corresponds to the same voltages on pins 4 and 7 at the opamp. The steps power supplies about 36v unloaded. I have been sneaking away from the new baby to build this and have not had much time to spend with this. Any thoughts?_

 

I think you're probably just testing with the probes at the wrong points for one of your readings. 12V is about half of 25V, so it seems to be splitting correctly.

 To verify this, keep your meter's black probe on IG, then touch the red probe on pin 7 of the opamp. You should get +12V. If you have a digital meter, then keep the black probe at IG, and touch the red probe on pin 4 of the opamp, you should get about -12V. If you have a meter with "needle pointer", then put the red probe on IG and the black probe on pin 4, and you should get +12V. By the way, I don't really recommend using a needle-type meter for measuring these circuits, because they tend to have much lower input impedance and would load the circuit you're trying to measure. Use a digital multimeter instead.


----------



## poolorpond12

Sorry guys. I was being hasty and should not have even wasted your time. I kept measuring from pins 4 and 7 to the common lead on the rail splitter, not the IG. Everything checks out.

 The power supply is only putting out 26v, not 36v.


----------



## silvervarg

My M³ build has been delayed by tons of things, but I finally got to the point where I want to ask for troubleshooting help.

 With no OP-amps in I measure:
 rails 22.6V, sockets (pin 7-4) 21.4V and pins 7/4 to IG about half that.
 Everything seems fine so far.

 Once I put in an OP at the ground channel (using NE5534 during tests) the voltages drops dramatically.
 Rails 11.5V, sockets (pin 7-4) 10.1V and pin 7/4 to IG about half that.

 So, any idea what is happening?
 It seems my rails are dropping to close to half the voltage with an op-amp in place.


----------



## Jazper

Quote:


  Originally Posted by *silvervarg* 
_My M³ build has been delayed by tons of things, but I finally got to the point where I want to ask for troubleshooting help.

 With no OP-amps in I measure:
 rails 22.6V, sockets (pin 7-4) 21.4V and pins 7/4 to IG about half that.
 Everything seems fine so far.

 Once I put in an OP at the ground channel (using NE5534 during tests) the voltages drops dramatically.
 Rails 11.5V, sockets (pin 7-4) 10.1V and pin 7/4 to IG about half that.

 So, any idea what is happening?
 It seems my rails are dropping to close to half the voltage with an op-amp in place._

 


 What amount of current is your power supply capable of? I'd guess you're overloading it.

 do you realise that the NE5534 is a bipolar opamp and will not work in the m3? Try a TL071 if you want a test chip that's cheap.


----------



## GregVDS

Hi,

 Long time I did not ask something. Too busy at work, but I now I just finished the initial setup. I still have to receive the boxes for STEPS and M³ and mount everything in them. I so don't have heard the amp in itself, for the crossfeed filter, switch and rca are still to be connected.

 I hope to have the boxes soon, so I can take precise quotes and modify lastly if required the front panel express fronts and backs. I think I will not be able to make a rectangular 34 x 72 mm hole, nor round holes of 24mm of diameter, required for headphone jack and speakon connectors I will use for power between PSU and AMP.

 I have some questions:

 I made the setup, following scrupulousely all the steps described. First I noticed the power voltage drop somewhat each time another opamp was introduced (not that much, don't remember the figures but I wrote them down for record). Is it normal? As I understand, the STEPS give a somewhat higher voltage without load, and less and less the load increasing, right?

 Through R5X (X = G, L, R) I first put 0.5V adjusting BIASOPX, then adjusted BIASX for 80mV through R9X. Coming back to chaeck to R5, I read a lower value, around 0.491V, depending on the channel (G being hoter, and working for longer than R, and this last one longer than L). I thought this is ok, but re-adjusted BIASOPX for 0.497V through R5X. What do you think of this.

 After the half-hour warm up, I pushed the quiescent current through R9X to 100mV PSU giving 24.77V, for the amp will drive a Grado RS-325i (32 ohms, sensitivity not that high, so volume put higher, having in mind also an Audio-Technica ATH-EW9, rated 28ohms). I had to readjust some time, the temperature counter-effect droping somewhat the quiescent current. Should I play reading-adjusting a long time or there is no point to be maniac here?

 What differences between R5's and R9's of reading is allowed (I mean to what point I should refine and quest for the same values for G, L and R)?

 I achieve almost nothing mV between IG and OG, maybe 0.1mV, 1.5~1.6mV for L and 2.3mV for R. Is it ok, keeping in mind my source will be an iPod giving around 3mV of DC offset, passing through a Modified Linkwitz filter (dropping of DC offset here or not?)?

 Many thanks again for any advice.

 All the best,

 GregVDS

 ps, I promise, when everything will be finished I will manage to post some pics, but I still to manage to reduce them enough for posting.


----------



## amb

Quote:


  Originally Posted by *silvervarg* 
_Once I put in an OP at the ground channel (using NE5534 during tests) the voltages drops dramatically.
 Rails 11.5V, sockets (pin 7-4) 10.1V and pin 7/4 to IG about half that._

 

The NE5534 is not unity-gain stable without a special compensation cap between pins 8 and 5, and the ground channel runs at unity gain. It is probably oscillating like mad, increasing the current draw dramatically. When opamps oscillate on the M³ it has the potential of damaging Q5+ and Q5-.

 Try using one of the recommended opamps, and if the problem persists, replace Q5+/Q5-.


----------



## amb

Quote:


  Originally Posted by *GregVDS* 
_I made the setup, following scrupulousely all the steps described. First I noticed the power voltage drop somewhat each time another opamp was introduced (not that much, don't remember the figures but I wrote them down for record). Is it normal? As I understand, the STEPS give a somewhat higher voltage without load, and less and less the load increasing, right?_

 

Yes, a small amount of drop (fraction of a volt) with each additional opamp is ok.

  Quote:


 Through R5X (X = G, L, R) I first put 0.5V adjusting BIASOPX, then adjusted BIASX for 80mV through R9X. Coming back to chaeck to R5, I read a lower value, around 0.491V, depending on the channel (G being hoter, and working for longer than R, and this last one longer than L). I thought this is ok, but re-adjusted BIASOPX for 0.497V through R5X. What do you think of this. 
 

That's fine. A variation in the third decimal place is too small to matter.

  Quote:


 After the half-hour warm up, I pushed the quiescent current through R9X to 100mV PSU giving 24.77V, for the amp will drive a Grado RS-325i (32 ohms, sensitivity not that high, so volume put higher, having in mind also an Audio-Technica ATH-EW9, rated 28ohms). I had to readjust some time, the temperature counter-effect droping somewhat the quiescent current. Should I play reading-adjusting a long time or there is no point to be maniac here? 
 

Just get somewhere close to what you want is fine. It's more important to make it consistent between channels than to hit a specific target precisely. When you put everything into a case, the thermal rise on the MOSFETs will increase somewhat and the quiescent currents will settle at a different point again.

  Quote:


 What differences between R5's and R9's of reading is allowed (I mean to what point I should refine and quest for the same values for G, L and R)? 
 

See above. It also depends on how picky you are.

  Quote:


 I achieve almost nothing mV between IG and OG, maybe 0.1mV, 1.5~1.6mV for L and 2.3mV for R. Is it ok, keeping in mind my source will be an iPod giving around 3mV of DC offset, passing through a Modified Linkwitz filter (dropping of DC offset here or not?)? 
 

As far as the amp itself is concerned, your offset readings are fine. The crossfeed circuit will reduce the effect of the source-induced offset somewhat (because it is lossy), but the overall offset will be whatever the amp "sees" at its input, multiplied by the gain of the amp.


----------



## SiuGuyGuy

Recently I had added and additional rca output for pushing my newly-build 3886 gainclone (certainly, I do remember to use signal in ground as rca output ground). The result is great and make my Jmlab 706 resurrect 
	

	
	
		
		

		
			





 While here comes some problems: I found that M3's DC offset is keep on swinging between 0-80mV when playing music. At first I am not even aware of this during building of kit, but when I checking voltage before input cap of gainclone, I suddenly discover that there's such DC keep on happening on the M3. 

 I had followed the initial setup procedure, and get 0.1mV(OG), 1.0mV(OL) and -1.5mV(OR) vs IG when no signal input, and checked my CDP's DC level is 0.1-0.2mV during playing music. The measurement is get from using 627AP x3, @30VDC. If changed to AD8610 x3 @26VDC, it even swing between 0-160mV. I asking this because when i measure gainclone's output dc level, I got no such condition(it only stay at 0.1mV even shouting loud) And, this only happen on OL/OR vs IG, OG vs IG do not have such change, keeped on 0.1mV.

 Is that normal, or something wrong with my M3? 

 Again trobuling question here, thanks fo advise!


----------



## amb

SiuGuyGuy, many multimeters can't reliably measure DC voltage while there is a lot of AC voltage riding on top of that (such as when you're playing music). If your DC offset looks reasonable when the volume is turned completely off, then everything is fine.


----------



## silvervarg

Quote:


 What amount of current is your power supply capable of? I'd guess you're overloading it. 
 

Well, first time I tried the PSU the regulator blew due to the high inrush current. With only ~3000-3500uF low ESR I though it would hold, but I was wrong.
 I connected a soft start in between and got it starting ok, perhaps I got the softstart wrong so it limits when I start to pull more current.
 The PSU should be able to give 1.5A, but it seems it doesn't with the softstart.

 Anyway, I tried with a bench supply that can supply 2A, and put in 3*AD8610 and all voltages seems fine. Finetunes all bias settings and then measuring 0.0mV, 0.0mV, 0.5mV offsets on outputs.
 All looks fine, so it tried it with music as well, and first impression is that it sounds perfect. 
	

	
	
		
		

		
		
	


	




 Real listening impressions will have to wait.

 Thanks for the help.
 Next step will be to check up on that PSU. Not very practical or nice to use the bench supply forever.


----------



## ottopig

Spent some quality time weekend trying to finish and case up my second MMM, but ran into a snag. So then I spent some quality time with my DMM and searching this thread for info. My first MMM went perfectly and sounds _great_, so I really don't understand this:

 Setup steps 1-3, looked good. Voltages from each DIP pin 4 and 7 to IG and across DIP 4 and 7 were good on all sockets. No shorts anywhere. Installed OPA627 in OPAMPG. BIASG set to 0.500V across R5G, BIASOPG set to 80mV across R9G+. No problem. Heat sinks warmed up nicely. 
	

	
	
		
		

		
		
	


	




 Installed OPA637 in OPAMPR. Could NOT raise BIASR higher than about 0.1V. 
 Installed OPA637 in OPAMPL. Exact same thing. BIASL wouldn't go higher than 0.1V. Both maxed at 0.1V and both were steady.

 Removed OPA637 and OPA627. Repeated everything with OPA604. Exact same thing: G channel working, R and L BIAS wouldn't go above about 0.1V. 

 I've compared the boards of both MMM and cannot see any differences. I checked the value of each R and each BIAS pot with the DMM and they are all correct (match their printed values, nothing is fried). 

 Am I just blowing some easy detail? 
	

	
	
		
		

		
		
	


	




 Thanks to all.

 ottopig


----------



## GregVDS

did you tried to put the OPA627 into the Left and Right channel, to see?

 It seems also the OPA637 is less tolerant regarding low gain. Your gain is ok for OPA637?

 For the rest I let specialists answer, that's my two cents ideas.

 All the best

 GregVDS


----------



## amb

ottopig, check the voltage across opamps' pins 4 and 7 with the OPA637 installed. Is it still what you expect?

 Check that the correct MOSFETs are installed in each position. 

 Also, is the BIAS pot turned all the way to their counterclockwise position when you are doing this step? If so, check the voltage across the C2 capacitor and tell me what it is.


----------



## ottopig

Amb and GregDVS,

 Thanks. I'm going to chalk this up to "don't do this stuff at 4 in the morning". 

 In preparing to take your advice and make new measurements, all I did was pull all the buffers, recheck the voltages without them, and then sequentially installed OPA in G, R and L and everything was perfectly normal. Easy to set BIASOP for 500mV and BIAS to 100mV, nothing fried.

 ???!

 ottopig


----------



## morsel

Moderators, please close this thread.
 M³ build discussion has been moved here:

New Headwize M³ Build Discussion


----------



## Finch&Music

Quote:


  Originally Posted by *morsel* 
_Moderators, please close this thread.
 M³ build discussion has been moved here:

New Headwize M³ Build Discussion_

 

What is the reason for this move?


----------



## diablo9

Quote:


  Originally Posted by *morsel* 
_Moderators, please close this thread.
 M³ build discussion has been moved here:

New Headwize M³ Build Discussion_

 

that's their Headwize discussion, why we have to close this thread and move our discussion to headwize?


----------



## grawk

Why would it make sense to move to a thread with no history?


----------



## Vladco

check http://www6.head-fi.org/forums/showthread.php?t=140490


----------



## diablo9

Quote:


  Originally Posted by *Vladco* 
_check http://www6.head-fi.org/forums/showthread.php?t=140490_

 

what the heck? that's GB policy thread, has nothing to do with M3 discussion.


----------



## Dougigs

If I glean correctly, it seems that the M3 designers as well as the MINT and PIMETA deisngers -- i.e. some of the best open-source headphone amp designers around -- seem to have been driven away from this site by its overly authoritarian new group-buy rules. 

 If I'm misreading, please correct me, and I will edit.

 If not, probably best to take your show over to Headwize.


----------



## diablo9

Quote:


  Originally Posted by *Dougigs* 
_If I glean correctly, it seems that the M3 designers as well as the MINT and PIMETA deisngers -- i.e. some of the best open-source headphone amp designers around -- seem to have been driven away from this site by its overly authoritarian new group-buy rules. 

 If I'm misreading, please correct me, and I will edit.

 If not, probably best to take your show over to Headwize._

 

I see your point, but I am still waiting for Jude's final decision. PMed him but no response. Depending on the policy, I might shift to Headwize, too, since I am mainly concentrating on DIY, now.


----------



## morsel

Quote:


 What is the reason for this move? 
 

...the reasons are a subject for private email.

 Team M³ will no longer provide technical support for M³ here at Head-Fi DIY. If the moderators choose not to close our thread and other members choose to continue discussing M³ here, so be it.


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## adhoc

in other words, _to protect those who pay_, discussions like this have to be moved to other forums.


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## Voodoochile

Quote:


  Originally Posted by *adhoc* 
_in other words, to protect those who pay, discussions like this have to be moved to other forums._

 

You are free to discuss M3 or any other headphone-related DIY projects here, or elsewhere. There are no qualms about that.

 There has been concern that some business ventures have been allowed to essentially promote themselves for free***, while other business ventures have paid for a mall-fi ad. No one is forced to buy any mall-fi ad, but it is not fair to someone who chooses to help support the site by purchasing a mall-fi ad when others running similar business ventures are not. In either situation, the general membership is of course free to discuss these or any other projects.

 That is as simple and brief an explanation as I am going to offer, and I don't want this thread to turn into a discussion of this situation, so it will be closed.

 YES, you may discuss this situation further, but in another thread if you like- this thread is _not _ being closed so that I could have the final word.

 YES, of course you may still discuss the M3 build process if you wish, post questions if you wish, just start a new thread for it at this point.

 Morsel has simply stated that "Team M³ will no longer provide technical support for M³ here at Head-Fi DIY." That is perfectly fine, and is their choice. This thread will not be deleted from the site, and may still be referenced at any time.

***_This thread did not represent those concerns at all, either. It was simply requested that it be closed. Again, you are free to open another one for the same purpose if you wish._


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