# "PPAS - SMD PPA that fits in a tin"



## ATAT

[size=x-large]*NOTE - This is the development thread, to just find out info about the PPAS, click*
*here
*
[/size]

 last night, got a bit bored, and combining my obsession with SMD components (so tiiiny!) with the PIMETA schematic, here's what I got..







 470uF x 4 rail caps, 
 No C1 Capacitors
 No class-A biasing
 Alps RK097
 OPA551 Buffers
 AD8620 for singal, 8610 for ground.
 All components (incl caps) are SMD, except the TLE. 
 Runs off 2x9v
 Size is 2.1x.98 inches. 

 If I take off the 2 rail caps, I think I can make this PINT size.. (with creative routing of course..) but not sure if thats a good enough tradeoff to make.

 I tried to minimize the number of vias, but minituarization was more of a concern to me..

 I'd really appreciate suggestions!

 Edit- Also, if anyone could tell me how to put SMD components on the bottom side of a PCB, I'd highly appreciate it..Change->Layer doesnt seem to affect component pads..

 Thanks!


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## guzzler

Quote:


  Originally Posted by *ATAT* 
_Edit- Also, if anyone could tell me how to put SMD components on the bottom side of a PCB, I'd highly appreciate it..Change->Layer doesnt seem to affect component pads.._

 

 Use the Mirror command


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## ATAT

So THATS how its done! 

 Thanks so much.. now time to make it a bit more compact... PINT size!


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## DaKi][er

Nice idea, I like where you're going with it but it looks like a real mess at the moment

 Post up some pictures without the silkscreen, have a go at placing components on the bottom as well, lots of room for cleaning up here

 Thought about who is going to manufacture one? batchpcb.com will do one real cheap (~$15-20 guessing) and they have a tolerance on traces that have to be 8mil spacing, so run a DRC on it and see what error you get with that


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## ATAT

Agreed, i couldn't for the life of me figgure out how to put components on the back.. so there's the mess. I think putting components in the back will decrease the space, but increase vias.. is that acceptable? IIRC, vias are to be minimized..

 i'll post pics of nonsilkscreen in a bit, what components should i put in the back? also, with going to the back, I think I can do a PPA-style power supply.. (ie smaller caps, and a buffer / nonbuffer psu divide). 

 As for fabbing, I'll probably use 4pcb's $33 order or use robotics' sponsor's fab.

 PS - what size pads should I use? the ones I'm using look too big..

 Now- No silkscreen





 Edit - Ugh, cant seem to make this any prettier without making it much larger. If anyone has any suggestions, I'd appreciate it, moving the whole ground channel to the back helped, but added a heapload of vias

 Edit2- Wow those pads are HUGE. fixing.


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## blueworm

Try and keep all trace angles to 45 degrees it makes layout a lot neater looking.
 Also if it is possibe try putting hook up wire holes and LED near the board edges, 
 this is not allways possible.

 What size SMD are you using, they look like 1206. 
 0805 are more fun 
	

	
	
		
		

		
		
	


	




 Using SMD caps does'nt really save much space, so IMHO why bother.

 Looking good so far.


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## Tenesu

Quote:


  Originally Posted by *blueworm* 
_Try and keep all trace angles to 45 degrees it makes layout a lot neater looking._

 

Also try to keep pad exits (where the trace intersects the pad) at 90 degrees. It can help avoid problems with manufacturing and looks nicer.
 An example:




 Whats the outline on the resistor footprints btw? It looks like its on the top copper layer which would be a bad thing.

  Quote:


  Originally Posted by *blueworm* 
_What size SMD are you using, they look like 1206. 
 0805 are more fun 
	

	
	
		
		

		
		
	


	


_

 

Or 06xx or 04xx 
	

	
	
		
		

		
		
	


	




 Those are lots of fun to solder. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *blueworm* 
_Using SMD caps does'nt really save much space, so IMHO why bother._

 

SMD caps can be hard to solder manually as well. I had some SM caps for a project and couldnt solder them manually since their pins were so short. I'd purchase a couple before making the board so you can see if they're solderable with your equipment.

 To make the board shorter I'd try putting some of the SMD resistors on the opposite sides of the board as the IC's and connecting them with vias.


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## ATAT

blue - most are 45 deg now, 2nd revision time.
 packages are most 0805 cept the 1M resistors which are 1206. I was thinking of putting SM caps on the other side (pads in same location, opposite layers) and saving some more space.

 Outline was auto-added by EAGLE


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## rsabo

Maybe consider different buffers, in my experience the OPA551 and the AD8610 don't play well together in the PIMETA. BUF634's would work without modification, though, since pin 2 isn't connected to anything.


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## NeilR

Now that the Pint is no longer available, you might get some customers


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## Jam_Master_J

Quote:


  Originally Posted by *NeilR* 
_Now that the Pint is no longer available, you might get some customers 
	

	
	
		
		

		
		
	


	


_

 

Pint is no longer available?


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## NeilR

Quote:


  Originally Posted by *Jam_Master_J* 
_Pint is no longer available?_

 

Apparently not. He discussed this yesterday on his Mint V2 thread on that other forum.


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## MASantos

Quote:


  Originally Posted by *ATAT* 
_last night, got a bit bored, and combining my obsession with SMD components (so tiiiny!) with the PIMETA schematic, here's what I got..


 470uF x 4 rail caps, 
 No C1 Capacitors
 No class-A biasing
 Alps RK097
 OPA551 Buffers
 AD8620 for singal, 8610 for ground.
 All components (incl caps) are SMD, except the TLE. 
 Runs off 2x9v
 Size is 2.1x.98 inches. 
_

 


 I would change the caps to through hole because it is easier to soder and the space is the same. 
 Class A could be done using SMD CRD. it only adds a bit of space and would be a great thing.
 You could try to make the buffer pads compatible with buf634 and opa551. 

 Also as other said, if you put some components in the bottom side you'll save space and improve layout. Ex: put the coupling caps directly on the bottom of the opamp power pins, etc

 The traces should also be reworked using 45º angles and 90º exits of the pads. 

 I would buy some boards if you ever order them!


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## blueworm

Quote:


  Originally Posted by *Tenesu* 
_Or 06xx or 04xx Those are lots of fun to solder._

 

Lets not get carried away 
	

	
	
		
		

		
		
	


	




 I would like to reach old age and conserve my eye sight. 
	

	
	
		
		

		
		
	


	




 &ATAT Are you aiming for any particular sized case?


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## ATAT

Rsabo- substantiate what you mean.. OPA551/AD8620 is fine in MINT config, what would make it different on a pimeta topology..?

 NeilR- Not really that much about the PINT, except the size, I don't trust the non-buffered design that is PINT and I thought I could shrink a PIMETA to that size, and PINT is still available, but tangent's just going to stop selling boards right?

 MASantos- Looking at revision 2, you'll see that the SMD caps are saving alot of space.. (back to back) If I used through-hole for the same capacitance I'd lose alot of board space.. So the question is , higher capacitance and SMD caps? or lower capacitance and through-hole. I personally never saw much advantage in botique caps, but perhaps there's a good reason to use lower capacitance, better cap. 
 Class-A -> So basically just a CRD connecting AD8620 output to -9V? 
 Yes, things are now really double-sided =p

 Blueworm -> PINT size is a real good size for me.. fitting in the MINT case is, in my opinion, the mark of a portable amp.
 And, 0805 / 1206 for resistors, readily available 

 Now- revision 2, still no CRD, but nearly PINT size +3/100 in and traces are now done well 45 deg, good entry and exit, only a few vias.. took ground to the bottom side too.





 No silkscreen






 Edit- Just realized, using the extra space I could use a PPAv1-like power supply, making it more of a PPA than Pimeta


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## FallenAngel

Buddy, this thing looks sick! I want one already, finalize the design and get the PCBs made, I'll be in line right away for one!


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## mono

Consider solid chip caps. Easier to solder than 'lytics, longer life, shorter, narrower. More expensive though.

 Although it doesn't exactly go along with your goal to minimize the size as much as possible, something that some might like is a discrete buffer like PPL used on the Lisa2. It wouldn't necessarily be that much board real-estate, the TO126 package for BD139/140 would stick up but unless one didn't want the pot at all, the board will have a similar populated height either way.


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## tobias_svensk

Quote:


  Originally Posted by *MASantos* 
_Class A could be done using SMD CRD._

 

Hello MASantos

 What places do you know that sells SMD CRD? I want some for my Mint
http://www.ettnet.se/~tobias/diy/mint/mint1.jpg

 Cheers


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## tangent

Quote:


  Originally Posted by *ATAT* 
_OPA551/AD8620 is fine in MINT config, what would make it different on a pimeta topology..?_

 

If it works for you, it's only accidental. The 551 is only a 3 MHz chip, while the 8620 is a 25 MHz chip.

 Why is that a problem? Because if there are any fast signals -- injected RFI noise, for example -- going through the amp the 8620 will pass them but the 551 won't be able to cope with them. That means you have no feedback above 3 MHz, but you have amplification above that. That increases the chances of oscillation greatly.

 Obviously you are not guaranteed to have problems. People have successfully run the 145 MHz AD8066 in a PIMETA, and what with my recommendations for R11, I doubt those same people were running it flat out at 180 MHz.

 I'm not certain, but gain might have something to do with it. As gain goes up, the bandwidth of an op-amp circuit goes down, but I don't think the buffer stage of a Jung multiloop circuit is affected by this. In my PIMETA example, a gain of just 3 would cut the bandwidth of the AD8066 to less than 50 MHz, which is probably less than a BUF634 with the recommended 220 ohm bandwidth control resistor.

 But even if I'm right, you'd have to use a gain of 17 (!) to get the same effect with a 551 and 8620. Heaven help someone wants to use an even faster op-amp.

  Quote:


 tangent's just going to stop selling boards right? 
 

Certainly there will be no more PINT v1.3s. Someone may come up with a small modification that takes care of all of my concerns about the PINT and I'll re-release the PINT as v1.x, but I don't think that's very likely. I plan on working on something to replace it, using the same board size but a different topology. 

 It'll still be unbuffered, so don't let that derail your plan.


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## ATAT

mmm tangent, what about a stabilization cap / ferrite to remove HF noise? if cutoff is around 3mhz then effects should be inaudible?

 Worst case, BUF634s are a drop-in replacement to OPA551 with the two pins shorted right? 

 Thanks muchly Tangent!

 Mono- if you're talking about tantalum SMD caps, they're really expensive at 470uF. Show me a mouser / digikey link of what you're talking about please.

 Also, your talk of discrete buffers makes me think that it may be possible to turn the output stage discrete, make the power supply isolated via JFETS and go PPAv2 style. I think wit hthe space i have left, the power supply is perhaps possible.. I'll investigate.

 But discrete probably wont happen, I want to reach PINT-size and thats probalby not possible if I add 4 SOT-23 4 TO-92 and such.

 Thanks!


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## mono

Quote:


  Originally Posted by *ATAT* 
_ Mono- if you're talking about tantalum SMD caps, they're really expensive at 470uF. Show me a mouser / digikey link of what you're talking about please._

 


 They are expensive, but I had overlooked that minor detail of "Runs off 2x9v". That effectively kills the idea, way too cost prohibitive.


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## Polaris111688

I have an idea for the discrete stage. You could use parts like the ones used in the Headroom amp modules. Their amp modules use discrete surface mounted transistors.


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## ATAT

Not sure if discrete is possible at this size.. the more I read about discrete buffers, the more I doubt it.. glassman's buffers are 1x1.2 / channel, much too big. 

 perhaps I could do this glassman style and add a riser board that "solders on" to the SO-8 so the board gets "thicker" but not any larger? not sure.. 

 Each buffer needs to be something like the size of 3-4 0805 resistor, and I think thats not really practical.. we'rr see though. 

 the one mono gave seems possible given creative routing but i'm not sure if that buffer is better than BUF634..


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## ATAT

Ugh, forget discrete buffers, I may not even be able to pull of Class-A.

 My dilemma is that if I add class-A, I'll have to add a fair amount of vias.. there's no way to cleanly integrate it space-wise.. so will you be willing to stand multiple vias on the Class-A path for that option? of course it'll use SOT-23, not the standard DO-35.


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## dhp

dont consider class A, we're trying to make a portable amp here that will use as little battery life for the best possible sound. I think that if we can get most of it down on SMD onto a PINT sized board, then we're good to go.


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## dhp

dont consider class A, we're trying to make a portable amp here that will use as little battery life for the best possible sound. I think that if we can get most of it down on SMD onto a PINT sized board, then we're good to go.


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## mono

Quote:


  Originally Posted by *ATAT* 
_Not sure if discrete is possible at this size.. the more I read about discrete buffers, the more I doubt it.. glassman's buffers are 1x1.2 / channel, much too big. 

 perhaps I could do this glassman style and add a riser board that "solders on" to the SO-8 so the board gets "thicker" but not any larger? not sure.. 

 Each buffer needs to be something like the size of 3-4 0805 resistor, and I think thats not really practical.. we'rr see though. 

 the one mono gave seems possible given creative routing but i'm not sure if that buffer is better than BUF634.._

 

I can only speak for myself, in that I put a simplified discrete in my Pimeta and never looked back. Consider the PPL buffer, it doesn't have to be large with the 1N4148 (or surface mounted small signal diode) and a TO126 output pair. A ferrite bead might be stuck anywhere, if it's really necessary (I didn't use one). As for the CCS, this is a battery powered amp, maybe 2N5484 isn't as useful here, I'd wonder if just a resistor will do the trick, or the CRD if the cost doesn't put anyone off.

 It's not my design though, I think it will be nice either way and there is plenty of room for different variants of the Pimeta generalized topology. I just felt it worth mentioning since the next Pimeta-esque build I do will have discrete buffers for sure.


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## ATAT

Hell yes! Victory!

 So, you may be wondering why I'm up at 2 and posting victory? I just think I got a PPA style isolated power supply onto the left side, got enough space for class-A biasing, and only added one extra via compared to PINT (two compared to mint) AND also its now smaller than the PINT.

 W00t. Now its PPAv1 inna tin!

 And I managed to make the caps thorugh-hole, just decreased the capacitance by a bit though. Meh, cry me a river.

 Obligatory post





 oh as for the DRC error, fixed it, and its 1:40, dont complain that the layout is messy. I'll fix that tomorrow.

 So.. anyone want to help me get a few of these proto'd?


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## ATAT

Shoot double post


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## [AK]Zip

Quote:


  Originally Posted by *ATAT* 
_So.. anyone want to help me get a few of these proto'd?_

 

Once the design is completly done I am in on helping you test these out. 
	

	
	
		
		

		
		
	


	




 -Alex-


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## blueworm

Quote:


  Originally Posted by *ATAT* 
_So.. anyone want to help me get a few of these proto'd?_

 

I'll do 1 also.


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## Polaris111688

Wow... Nicely done, ATAT!


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## MASantos

http://www.mouser.com/index.cfm?hand..._pcodeid=78109

 found these CRD's at mouser. There are same values to choose from. maybe digkey has something similar or better. I'll check it later today!


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## cetoole

Quote:


  Originally Posted by *MASantos* 
_http://www.mouser.com/index.cfm?hand..._pcodeid=78109

 found these CRD's at mouser. There are same values to choose from. maybe digkey has something similar or better. I'll check it later today!_

 

Thanks MASantos, I knew I had seen SOT23 CRDs somewhere, couldnt remember where. And all the way up to 4.7mA, thats perfect.


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## tangent

Quote:


  Originally Posted by *ATAT* 
_mmm tangent, what about a stabilization cap / ferrite to remove HF noise? if cutoff is around 3mhz then effects should be inaudible?_

 

You throw that word "cutoff" around as though a filter is a brick wall. No such thing. In the circuit size you're looking at, you'll probably only be able to fit a single-pole filter. You'd probably have to start filtering right above the audio band to have a good shot at getting the filtration at 3 MHz to be high enough.

 Okay, so you accept that. Where do you put these filters? Answer: on every pin that connects to the outside world, including the output pins; these are the holes in your case's Faraday cage. (You _are_ going to limit yourself to metal enclosures, right? If not, your whole filtration plan goes out the window.)

 Bottom line: this is hackery you're talking about. Use an appropriate buffer for the chips you want to use.


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## ATAT

tangent - you're absolutely right... didn't even think about how far I could filter... 
 However, did make it pin compatible with BUF634s and LT1223 (I want to see how well this performs..) 

 Meh, Added capability for class-A, no vias added (woot). I think this is about the limit for the board space I have... Now time to clean up the mess.

 This seems kinda messy but..





 The 3 pads you see to the right of the PSU part and left of the ground channel are the negative pads for class-A CRDs. the right side and to the bottom of the ground channel is 3 pads for positive of CRD. basically, CRDs should be inserted such that they're above the opamps.. meh, unintuitive, but it allows me to not use any vias, and if you class-A a portable amp, you should know what you're doing.


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## jbloudg20

Looks interesting... count me in for a prototype


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## fierce_freak

I'd be willing to give it a go, too.


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## ATAT

I think this board is ready for beta.. I've cleaned up the traces, lessened via numbers and finally did what I wanted to do, ground plane and V+ plane. Meh, might as well give it a whirl and see if it compares with my PPA at home..

 obligatory pics.





 3d pix





 bottom


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## MASantos

ATAT, I can't see the class A pads with all the color in the board and small space. Could you highlight these? Also, (you're gonna kill me for asking this!) where's the charging circuit?


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## jbloudg20

Quote:


  Originally Posted by *MASantos* 
_ where's the charging circuit? 
	

	
	
		
		

		
		
	


	





_

 

HAHAHHA Good point!


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## ATAT

MASantos - Duly noted, highlighted






 The V- pads connect to the Opamp out pads... basically you simply put a CRD between pads, on top of the opamp. it looks ugly, but it should work.

 The charging circuit? you mean my Elpac and resistor? Grin.

 Actually, I'm ready to do the first prototype board.. I'm not sure if this will work (ie pre-beta) but meh, no better way but by trying.

 The ONLY concern I have is my schematic for the power section..
 I have 2 JFETs isolating the entirety of the Opamp power rails (ie all opamps are isolated via jfets) 
 there are 2 on each rail (+ and -) and I'm planning on using a high Idss SOT-23 JFet (see backside on the rendering..) SST310 With a minimum 24 mA Idss, so each rail should have 48mA Idss minimum, and since each opa draws about 6mA quiescent, that should be fine yes?
 please check, thats the one part I'm worried about.


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## MASantos

So there are no proper pads for the class A biasing, the CRD's are mounted directly to the pins of the opamps?


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## ATAT

There are "proper" thorugh hole wirepads. (ie, no hackjob solder to opamp leads)
 basically, the CRDs have to go on top of the opamps (the physical CRD) with the leads connected to the highlighted pads..
 So yes and no I guess.


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## ATAT

2 things

 first, the JFET was connected incorrectly (thanks Cetoole!), fixed. 

 Now ready for prototyping.. hopefully I'll have a board in a week or two. 

 Also, once this is confirmed working under BUF634, I intend to siwtch the circuit to use LMH6321, a ridiculous noncontinuous 700mA output sound enticing? it does to me. at 30Mhz there shouldnt be any matching issues either. 

 Lookin' good. This should even run off 8 AAA batteries 8*1.5 -> 12v -> +-6 which should run the LMH6321 fine.... and that'll give longer life.

 Estimated costs

 Resistors $2.3
 Caps $2.4
 JFets $2
 Buffers $20
 Already own 8620 / 10 and TLE so no costs there
 so project subtotal comes out to be around $25, probably something like $50 if you pay everything.


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## DaKi][er

http://www.national.com/search/searc...ywords=LMH6321

 this lm6321?
 110mhz, 300mA and a supply current of 10mA each which is getting a little on the high side


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## cetoole

Quote:


  Originally Posted by *DaKi][er* 
_http://www.national.com/search/searc...ywords=LMH6321

 this lm6321?
 110mhz, 300mA and a supply current of 10mA each which is getting a little on the high side_

 

May I quote your sig? 
	

	
	
		
		

		
			




  Quote:


  Originally Posted by *DaKi][er* 
_Audio electronics- Where we strive for inefficiency_


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## mono

Quote:


  Originally Posted by *ATAT* 
_ This should even run off 8 AAA batteries 8*1.5 -> 12v -> +-6 which should run the LMH6321 fine.... and that'll give longer life._

 

Alkaline, starts out at 1.5 but roughly linear drop, not 1.5 most of it's useful life. NiMH (what many will prefer) Starts at 1.45 or so but also (less linear but still a drop) down approaching 1.0 and lower at the bottom of the discharge curve.

 The spec for this is +-5 minimum? IMO you will want at least 9 cells if not 10. Maybe it'll stay stable under +-5V though, or maybe it won't be stable no matter the voltage. 

 Is there an exposed 'sink on the bottom tied to V-? It might not be good to have tracks running adjacent on top layer due to heat or capacitance issues.


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## ATAT

mono you're right, but the LMH6321 runs at alot less than +-5. spec sheet seems to indicate it'll go down to 3.

 And yeah, the sink will require rerouting to be done.

 Daki][er a little would be an understatement, but I'm thinking of the total power consumption of this..
 Opamps -> 3mA *3 -> 9mA
 Buffers -> 10mA *3 -> 30mA
 (i'm guessing ground buffer will be doing alot less work?)
 around 39mA. run off 8x sanyo 900mAh will last a while... if run off 2x9v at 18 volts, it'll still run long enough... If I add a fast-charger daughterboard, it'll be pretty nice..

 Or am I fudging with the calculations here?


 Anyone used http://www.ultralifebatteries.com/datasheet.php?ID=U9VL these before?
 1.2 Ah sounds REALLY tempting.

 The intention of the amp is to deliver on size and quality, at sometimes the cost of runtime.. but I'll come up with a nice charger circuit.. =p


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## ATAT

So, MA santos. here's the charging circuit.





 Total size? .780 x .8 .. yes its under 1 square inch. 

 and you must be wondering, whats all those SOIC doohickies on that board?
 Keeping with the general "overkill" philosophy of this amp, they're Li-Poly charger stuff. Basically this is a fast-charge Li-poly circuit, with a 3.3volt overdraw protection. This should basically be a hands-off Li-po implemenation. However, there's no thermistor to cut off charge. user MUST add thermal fuse to prevent li-po runaway. 

 Oh, for all you PINT owners, this circuit will allow you to use Li-Po. 

 This board should work beautifully, except for one thing, there will be no music playing while charging. Lithium batteries are picky, and if there is any draw to the cells while charging. Well, prepare to say goodbye to your worldly posessions.
 I'd like to have another p mode MOSFET and cleaner implementation, but there's really no point. I'll use a switched DC jack and disconnect the ground of the amp whenever charger wallwart is inserted.

 sorry about all the vias, but honestly, I dont care. this is a power-supply circuit; not audio circuit.

 Oh and i'll add proper Class-A. With 2Ah Li-Po batteries, there's no reason not to


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## mono

Hmm, it looks nice, but you are aware the battery you linked previously is not rechargeable? 

 So what's the BOM on charger plus special cells to go along? Is there a target case all this (plus the amp) is targeted to fit tightly into?


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## ATAT

Yes, I didn't link to the battery I intended to recharge did I?

http://www.hobby-lobby.com/thunderpower.htm

 TP20003 should just fit in the MINT tin with the amp and charger circuit.


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## mono

Not exactly inexpensive cells, what is the grand total for ALL of this amp+charger+cells going to cost? You made a passing comment about $25, did you mean $125?


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## dhp

Quote:


  Originally Posted by *mono* 
_Not exactly inexpensive cells, what is the grand total for ALL of this amp+charger+cells going to cost? You made a passing comment about $25, did you mean $125?_

 

I'm guessing 25 since smd is cheap, but the board will add to the costs


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## ATAT

$25 for passives and psu, 
 add cost of opamps and buffers

 can be run off 2x9v, that should be the normal config.

 but just for fun, I intend to run mine off li-poly, so that will, in fact raise the cost by a fair amount.

 of course for rechargables, and cheaper config, one could use 
http://www.thomas-distributing.com/i...le-battery.php

 and change the resistor config on the charger a tad. This would allow for 1Ah config at $25 extra.


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## Armitage

I hope this doesn't get me kicked off the board, but I cannot see paying $79.90 for a battery.

 I'm fine, however, with $14.97 for that 500mAh 9 volt.


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## ATAT

hahaha agreed. The large battery is for my entertainment, the other 2x9v should be the normal configuration.


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## dhp

Ok, me and ATAT have been working together, and the prototype board should be arriving shortly. I will contact jude about getting a GB together for these boards, so I just want to gauge the amount of interest involved while I get jude's response on it. Thanks


 Daniel


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## dhp

Quote:


  Originally Posted by *mono* 
_Not exactly inexpensive cells, what is the grand total for ALL of this amp+charger+cells going to cost? You made a passing comment about $25, did you mean $125?_

 

I'm guessing ALTOGETHER, with everything, including batteries, the cost will approach about 80 bucks?


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## fierce_freak

I'm still interested, DiaF. Thanks for the update.


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## cire

Quote:


  Originally Posted by *DieInAFire* 
_I'm guessing ALTOGETHER, with everything, including batteries, the cost will approach about 100 bucks?_

 

it shouldn't cost anywhere that much for a basic, non lithium-ion/polymer configuration. three BUF634Us would cost just under $20, depending what opamps you use in the gain stages, it would be anywhere from 10 bucks (using cheap opamps like 2132 and 132) to $50 (if you find a creative way to mount OPA627s). assuming the BoM ATAT sent me is right, the cost of passives costs about $15.


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## mono

Quote:


  Originally Posted by *DieInAFire* 
_I'm guessing ALTOGETHER, with everything, including batteries, the cost will approach about 100 bucks?_

 


 I was thinking the batteries, charger board (populated) and supply will be closer to $100 then add whatever the amp costs.


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## mono

Quote:


  Originally Posted by *cire* 
_it shouldn't cost anywhere that much for a basic, non lithium-ion/polymer configuration. three BUF634Us would cost just under $20, depending what opamps you use in the gain stages, it would be anywhere from 10 bucks (using cheap opamps like 2132 and 132) to $50 (if you find a creative way to mount OPA627s). assuming the BoM ATAT sent me is right, the cost of passives costs about $15._

 


 It seems you quickly discount things like shipping, and perhaps knobs, jacks, case, etc? By a similar logic a stock Pimeta would cost $30 to 50 but ask some what they ended up spending even without botique parts. I'm not suggesting it isn't a worthwhile amp, just that it would be better to put a median estimate on cost with stipulations of how to save a buck here or there in certain situations.


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## ATAT

mm. my BoM for cheap everything, (tin, jacks, buffers, opamps .etc) comes out to around $45 (incl shipping) then add the cost of the charger circuit. the board components themselves will probably cost around $20-30 and the lipo batteries will cost $28 (we will assume no crazy 2000mAh setup). 

 Chepest setup possible would cost somewhere 'round $50. (cheapest as in, get the cheapest of every part (esp opamps), dont get rechargables and get ultralifes instead).

 most expensive setup, I have no clue, you guys are pretty creative in making BoM's cost alot so I'll say upwards of $100?

 if its any telling, my prototype setup which isn't really skimping on anything, costs $66 (all included with shipping) and 42 without shipping.
 Mono, if you'd like, i'll glady send the BoM for you to check.


----------



## FallenAngel

Hey guys, I've seen you refer to "charger circuit" as if it's very expensive, why not just use this trickle charger, I put that in my Pimeta and it cost me barely a couple of bucks, works great too.


----------



## dhp

Quote:


  Originally Posted by *cire* 
_it shouldn't cost anywhere that much for a basic, non lithium-ion/polymer configuration. three BUF634Us would cost just under $20, depending what opamps you use in the gain stages, it would be anywhere from 10 bucks (using cheap opamps like 2132 and 132) to $50 (if you find a creative way to mount OPA627s). assuming the BoM ATAT sent me is right, the cost of passives costs about $15._

 

costs depend a lot on which batteries you get


----------



## dhp

ok, group buy thread should be on soon


----------



## ATAT

Fallen Angel - yes you could, and it would cost you a few bucks, the charger on the previous page is a pretty complex design used for lithium-polymer batteries, which you could use to get nearly 2x the battery life of NiMh batteries you normally see. 

 But yes, if you just wanted charging you could add it for a few bucks.


----------



## saab

Quote:


  Originally Posted by *DieInAFire* 
_ok, group buy thread should be on soon_

 

Is this a small group buy for error checking and debugging? Or is this a full fledged, balls out, buy it and build it group buy?

 I guess I am just checking if this group but is based on a theoretical design.


----------



## dhp

Quote:


  Originally Posted by *saab* 
_Is this a small group buy for error checking and debugging? Or is this a full fledged, balls out, buy it and build it group buy?

 I guess I am just checking if this group but is based on a theoretical design._

 

well, I'm going to first test the prototype, and then revise if needed, prototype, revise if needed, prototype, looks good, and then commence mass production

 I mean, the design is basically the PPAv1, so it's a proven design


----------



## ATAT

basically, the prototype board should arrive tomorrow, since the schematic is based on the PPA, I really can't see what will go wrong. when we confirm it to be working, and sounding good, we'll go ahead with the GB.

 All DieInAFire is doing is getting permission for one when it does work.

 Don't worry, I know the importance of a long dev cycle and prototyping.


----------



## saab

Sounds great. I would have been in either way. Looks awesome.


----------



## mono

Quote:


  Originally Posted by *ATAT* 
_mm. my BoM for cheap everything, (tin, jacks, buffers, opamps .etc) comes out to around $45 (incl shipping) then add the cost of the charger circuit. the board components themselves will probably cost around $20-30 and the lipo batteries will cost $28 (we will assume no crazy 2000mAh setup). 

 Chepest setup possible would cost somewhere 'round $50. (cheapest as in, get the cheapest of every part (esp opamps), dont get rechargables and get ultralifes instead).

 most expensive setup, I have no clue, you guys are pretty creative in making BoM's cost alot so I'll say upwards of $100?

 if its any telling, my prototype setup which isn't really skimping on anything, costs $66 (all included with shipping) and 42 without shipping.
 Mono, if you'd like, i'll glady send the BoM for you to check._

 

It's not that I think it impossible to do this low cost, but the final cost could vary widely. With a project such as this there is a real potential for others to (at least consider if not actually) build it, and towards that end it might be useful to have a BOM and sources available for everyone rather than PM'd, as hunting down parts and where-to-get-what towards end of ordering from fewest vendors is always nice to have. 

 I'm sure using a tin for a case helps to lower costs, but are you also counting the board costs?

 I don't know that "cheapest of everything" is the route some will want to take but since this is modularized to the extent of the battery, it's really two separate projects though the latter compliments the former.


----------



## ATAT

Mono, Agreed. I just dont have any web space to put the BoM up on. 

 I have a few ideas for what kind of components could be used, and the "best" I can think of would cost upwards of $120, given the highest tolerance resistors, good caps, LM6321s, and Lithium Polymer batteries... (not 2000mAh but 730 mAh, on second thought 2Ah is just ridiculous.. and expensive).

 my prototype setup will cost about $60 altogether, considering 1% resistors, nichicons, and AD8620/10 LM6321. I'd say thats pretty good.

 Board, in production quantities should be around $5 (dont quote me on this) and the tin should be around $3.

 The battery project is still in the works compared to the amp, the amp's been simulated part by part (since the whole circuit kept giving me singularity matrix erros) (SPICE ftw.) but the lithium polymer charger has not.. I'll do this later, but for now my focus is on the amp.


----------



## fierce_freak

I'm willing to contribute webspace if need be.


----------



## digitalmind

Great stuff! Will deffinitly be part of a group buy if it gets to it, my portable rig is dieing for an amp.


----------



## [AK]Zip

Here is the bom list.

http://apuresound.com/ATAT/boms.xls

 -Alex-


----------



## ATAT

AK, thanks for the webspace! you forgot a .com btw...

 Documentation and parts selection guide will be up later.

http://apuresound.com/ATAT/boms.xls


----------



## fierce_freak

Is there a bom for the charging circuit, as well?


----------



## ATAT

Not yet, I might decide to scrap lithium polymer entirely and go with the ever popular NiMh... really depends on the feedback I get. Currently I'm waiting to see how the amp (the important part) goes.


----------



## ATAT

The prototype parts and board have arrived! I'll build it and see if its any good... 
 =) Grin. I'll start with a BUF634 buffer config, then move to LM6321.


----------



## saab

You know we are going to demand some pics. I can't believe you posted this without that in mind. 
	

	
	
		
		

		
		
	


	




 I can't wait to see what you think.

 -John


----------



## dhp

heh, the board is at my house now, so can't start yet 
	

	
	
		
		

		
		
	


	




 on the other hand, I got the ok from jude for the GB thread last week, but it still hasn't appeared, how sad...


----------



## dhp

ok, awesome, ATAT has the board and will hopefully finish it tonight and post impressions by tomorrow evening, and the Group Buy thread is up, and is located here:

http://www6.head-fi.org/forums/showthread.php?t=181347


----------



## Tedro

Excellent, I am itching to order something. You think I should start ordering the passive componnents yet or should I wait till you finalize your build and OK the deployment? Sorry my eglish is good not so.

 that is all


----------



## dhp

Quote:


  Originally Posted by *Tedro* 
_Excellent, I am itching to order something. You think I should start ordering the passive componnents yet or should I wait till you finalize your build and OK the deployment? Sorry my eglish is good not so.

 that is all_

 

i would wait, after all, after you pay, it will take time for the boards to be fabricated and shipped, in which time you can purchase your passive components.


----------



## mono

Quote:


  Originally Posted by *Tedro* 
_Excellent, I am itching to order something. You think I should start ordering the passive componnents yet or should I wait till you finalize your build and OK the deployment? Sorry my eglish is good not so.

 that is all_

 

Well... keep in mind, this is a generalized, valid topology, and a nice small form-factor, but ultimately the parts you select are up to you! Ah, the beauty of DIY. 
	

	
	
		
		

		
		
	


	




 Just make sure the sizes match those alloted on the board IF this is indeed the finalized layout.


----------



## MASantos

I've read the BOM and you say there that the LM6371 must be sampled since there is it not sold. 

 The buf634 is also very difficult to find.
 This will probably be a problem for people who either don't like o order samples or don't have any stock of the said buffers. 
 s
 Shouldn't you use a chip that has regular availability?


----------



## ATAT

Hey, I've worked on the protoboard a bit last night.. here's results and such

 first, the power supply works very well.. the rail isolation JFETs are working as intended. that's good.. that was something I was worried of

 second, ground channel doesn't oscillate, another thing i was worried of since ppl warned me of this.

 now, there's one problem i've run into.. not sure how severe it is.. 
 L/R channels are throwing noise.. alot of it. since I suspected buffres, they're now unpopulated, and my signals are taken out of the opamp outputs..

 possible issues.
 1). Opamp is dead .. entirely possible, cant check until I have a few more opamps..

 2). my schematic is wrong... check this over please
http://apuresound.com/ATAT/schem.gif 
 the feedback loop should be identical to that of the PPA v1.

 3). R6 is too large.. MisterX suggested this, I'll fix this today..

 I'll scope the board and post whats going on.. it may just be a bad opamp. I hope


 Also - MASantos - the LM6321 should be available via normal suppliers soon.. its a very new IC so I cant find it anywhere but it should start appearing.. for now, there's only sampling available.. any BUF634-pin compatible buffers will work... If one was courageous enough, they could use the OPA2227 and OPA551.


----------



## digitalmind

I'd go with MisterX here, R6 gives the opamp a very high gain. That could be the problem.


----------



## MASantos

PICS PICS PICS PICS PICS PICS PICS PICS PICS PICS PICS PICS PICS PICS


----------



## ATAT

MA santos, forgive me since the board is really ugly right now.. I dead-bug soldered the AD8620 so I could easily swap opamps.. but I could post pics later on.. when I have this working.


----------



## MASantos

I went to national.com to check the specs of the LM3621 and it said that it was discontinued.

 Digikey.com also says that it is discontinued.


----------



## ATAT

That's the old LM6321.. the new one I think is so new it hasn't been updated on their site yet.
http://www.national.com/pf/LM/LMH6321.html#datasheet
 if that doenst work, go to national.com -> amplifiers -> buffers -> LM6321 

 the datasheet just came up on the 5th of april '06. so I suspect its not discontinued


----------



## ATAT

Update - Its not 1 or 3. Then it must be 2.

 Swapped opamps, OPA2134 was dropped in for AD8620, no dice, differnt problem though, AD8620 outputted constant, earsplitting volume of noise, OPA2134 is very very faint, and i think it responds to volue control.

 Put another 1M in paralell, that cut the bandwith in half, but problem wans't solved with the ADs.

 mm. maybe the OPA is getting insufficient current? 12mA *2 / 3 -> 8mA / channel, should be enough..


----------



## cetoole

It would be a good idea to have your virtual ground channel reference the vgnd created by the TLE. As it is, its just tied to the gin pad, which I dont see referencing ground anywhere.


----------



## ATAT

Update 2 - problem found

 "
 (10:57:02) cetoole: :O
 (10:57:04) cetoole: What?
 (10:57:12) cetoole: how the hell do you have the ground wired?
 (10:57:18) cetoole: it doesnt seem to be tied to the tle
 [..]
 (11:00:04) Tatsu: oh crap
 (11:00:06) Tatsu: how did i miss that
 (11:00:09) cetoole: 
	

	
	
		
		

		
		
	


	



 (11:00:12) Tatsu: oh ****
 (11:00:13) cetoole: that might be it?
 (11:00:13) Tatsu: im stupid
 "

 sighs.


----------



## MASantos

ROTFLMAU































  Quote:


  Originally Posted by *ATAT* 
_Update 2 - problem found

 "
 (10:57:02) cetoole: :O
 (10:57:04) cetoole: What?
 (10:57:12) cetoole: how the hell do you have the ground wired?
 (10:57:18) cetoole: it doesnt seem to be tied to the tle
 [..]
 (11:00:04) Tatsu: oh crap
 (11:00:06) Tatsu: how did i miss that
 (11:00:09) cetoole: 
	

	
	
		
		

		
		
	


	



 (11:00:12) Tatsu: oh ****
 (11:00:13) cetoole: that might be it?
 (11:00:13) Tatsu: im stupid
 "




 sighs._


----------



## NeilR

It never ceases to amaze me how a guy that is always sucking his thumb in public can find stuff like that so quickly....


----------



## cetoole

You seem to have the opamp inputs wired backwards, so you are inputting ths signal to the - input, and have the + input wired for the feedback loop, so its inverting on the left/right channels, but not on the ground. Didnt notice at first because the part is upside down from what I am used to on the schematic.


----------



## ATAT

cetoole - found that a while ago.. fixed it too.

 Also, it works! took out the resistors that form a low pass filter, and for now im using no jfets. I'll try with SST310s soon

 Anyway, it sounds great! I'll post impressions later


----------



## ATAT

Sorry for responding to my own thread, but here goes.

 Caveat - I have not listened to the newest and greatest of amps, such as mini^3, PINT or such, my impression is based off of my old MINT, PPAS, Vanilla Millet Hybrid, and PPA v2.

 Impressions - Running through 3 sources, M-robe, D-33 and T42's h'phone out. through PPAS (thats what daniel wants to call it i guess) into my RS-1s and KSC-75. This really does the RS-1 bass justice, and brings out the highs. This amp is really similar to the PPA v2, and seems to bring out the details... with the KSC-75s, this seemed to really slam on the bass, so I'll be using this from now on.. =). 
 I liked this alot more than the MINT, and probably more than the Basic millet hybrid.. and in some parts, it seems to match the PPA (detail.. just lacks that little bit of slam on the bass..) 

 Config is OPA2227 / BUF 634s / AD8610 (ground). Can't get amp to oscillate under any supply configuration.. Draw was measured at 10-20mA. 

 For anyone intending to use this amp, they MUST use the SST310, NOT SST309. The SST309 cannot provide enough current to drive ANYTHING.

 I'm satisfied enough with this amp to end dev, and get a proper (fixed) board for it.


----------



## Filburt

Hey, if you can, try an LM6172 on the L/R and LM6171 on the ground channel and see what happens. Also, looking at your latest board layout, are you sure you don't have BUFG and OPAG too close to eachother on the bottom there?


----------



## ATAT

Too close to cause electrical interference, or too close to put the chips on?

 if its the latter, there's enough space to put both on. that's not a problem, 

 as for electrical interference, its unlikely, since the traces i spaced fairly wide apart, and its running at a fairly low bandwith...


 I'll try various opamp / buffer combos such as LM6172/1 when I get to it.. I dont have that particular opamp..


----------



## Filburt

Quote:


  Originally Posted by *ATAT* 
_Too close to cause electrical interference, or too close to put the chips on?

 if its the latter, there's enough space to put both on. that's not a problem, 

 as for electrical interference, its unlikely, since the traces i spaced fairly wide apart, and its running at a fairly low bandwith...


 I'll try various opamp / buffer combos such as LM6172/1 when I get to it.. I dont have that particular opamp.._

 

Alright. I'd really like to make sure I can use that op-amp with this as I've found it to be both nice in terms of power efficiency as well as nice in terms of sound.

 As for closeless, I was referring to interference. It definitely isn't too close for me to be able to solder it. This project looks like a fairly simple/straightforward solder job overall. It isn't running at such low bandwidth that I think we don't need to be careful about it, especially with high speed parts like the 6171/72.


----------



## dhp

Quote:


  Originally Posted by *Filburt* 
_Alright. I'd really like to make sure I can use that op-amp with this as I've found it to be both nice in terms of power efficiency as well as nice in terms of sound.

 As for closeless, I was referring to interference. It definitely isn't too close for me to be able to solder it. This project looks like a fairly simple/straightforward solder job overall. It isn't running at such low bandwidth that I think we don't need to be careful about it, especially with high speed parts like the 6171/72._

 

the AD8620 has extremely low current draw and sounds extremely good, so I wouldn't feel the need to stray from the ad8620, although you could certainly opt for the LM6172 if you wish.


----------



## Filburt

Quote:


  Originally Posted by *DieInAFire* 
_the AD8620 has extremely low current draw and sounds extremely good, so I wouldn't feel the need to stray from the ad8620, although you could certainly opt for the LM6172 if you wish._

 

I'm not really thrilled by the AD8620 sound, to be honest. I've heard combinations with it recently, though, that sound better than earlier implementations of it that I'd heard, but it still doesn't really float my boat. At least, not so much that I'd care to make an amp of this sort with it. I have a pretty good idea of what it'll sound like in this amp, and I think I'd like the 6172's sound better.


----------



## ATAT

Hey filburt, i see you live in San Jose, could you by any chance ship me 1 LM6172 and 1 LM6171, I'll pay for all shipping.. National Semi .etc takes too long to ship to test out in any reasonable timeframe.

 I understand why you would want to do that, im pretty confident the 6172 will work without issues, but the 6171 may need coaxing..


----------



## Filburt

Quote:


  Originally Posted by *ATAT* 
_Hey filburt, i see you live in San Jose, could you by any chance ship me 1 LM6172 and 1 LM6171, I'll pay for all shipping.. National Semi .etc takes too long to ship to test out in any reasonable timeframe.

 I understand why you would want to do that, im pretty confident the 6172 will work without issues, but the 6171 may need coaxing.._

 

I actually don't have any on me, otherwise I'd do it. I think DigiKey or Mouser stocks these, though. Maybe there are others who do as well like Newark.

 Edit: Just checked - DigiKey has both, Mouser doesn't, Newark does.

 If you haven't tried this chip, I do recommend it soundwise. I can see (hear) why Jan Meier is such a fan of it.


----------



## n_maher

Quote:


  Originally Posted by *ATAT* 
_Config is OPA2227 / BUF 634s / AD8610 (ground). Can't get amp to oscillate under any supply configuration.. Draw was measured at 10-20mA. _

 

You must be running the 634s in limited bandwidth mode to get current draw that low. Open those suckers up and I bet the amp will sound really good. Actually, it'd be a neat trick if you could implement a bandwidth setting switch for long or short batter life.

 Nate


----------



## dhp

Quote:


  Originally Posted by *n_maher* 
_You must be running the 634s in limited bandwidth mode to get current draw that low. Open those suckers up and I bet the amp will sound really good. Actually, it'd be a neat trick if you could implement a bandwidth setting switch for long or short batter life.

 Nate_

 

that would be pretty sweet, especially for a home and portable rig together
 however, it would be a pretty tight fit


----------



## ATAT

Does it matter if the ground is in wide-band? my gut says no... it is after all just sinking and sourcing current..

 anyway, implemented. jumper switches between two modes.


----------



## Filburt

If this works, this is going to be a pretty cool project for people to do.


----------



## n_maher

Quote:


  Originally Posted by *ATAT* 
_Does it matter if the ground is in wide-band? my gut says no... it is after all just sinking and sourcing current.._

 

I lack the required technical knowledge to argue whether it does or not but Tangent certainly encourages using the same bandwidth setting for BUFG and BUFL/R in the PIMETA, at least that's the way I read the docs.


----------



## dhp

Ok, right now, my ears are hurting because I didn't know the gain was set at 11 when I plugged in GRADOS (impedance of 32 ohms), so my brain is a bit frazzled, because i couldn't immediately take of the headphones because I needed to gently set down the amp because otherwise it would fall apart. The build quality of the prototype leaves much to be desired. Now onto my impressions:

 The PPAS is certainly bright, just like its larger version, the PPAv1. In fact, RS-1s are bright, the PPAS is bright, and the Miles Davis album Blue Moods, or at least the second song, is also bright. So in essence, my ears are also hurting from that recording in addition to obscene volumes. It bordered on sibilant, so I suggest that you use less bright headphones. On the other hand, it could be the fault of the opamps, with OPA2132 on the L/R channel and AD8610 on ground. However, when I put my K501s on and swapped recordings to Chopin by JOn Nakamatsu, everything mellowed down, and suddenly, it was bliss. Certainly, running it out of the headphone jack of an IBM T41 leaves much to be desired, but needless to say, it's quite an impressive amplifier. It seems very very fast and detailed, and on other recordings, there was an impressive bass slam. I need to spend more time with this amplifier and the PINT to make adequate comparisons though.


----------



## Filburt

Good to see that it's performing impressively for both of you. I look forward to seeing how it performs with the LM6171/72.


----------



## Filburt

Hmm another chip we could try is the LM7372. It has better pulse response and much better phase margin than the 6171 or 72. No single amp equivalent to it, though, that I can see...which is unfortunate. The 7171 is some totally different op-amp that has much less stable performance.


----------



## ATAT

Hey all.

 Prototype board #2 was ordered today, this has provision for high-bandwith switch.. so this amp could possibly be used as a home-amp. (up to 20 volt supply). 

 I will leave this country in about 6 more days, so DieInAFire will take over all testing, board revisions (if any) and build help. 

 He's working on 

 -Various closed / open loop buffer compatibility and opmap compatibility tests..

 -adding a PINT-style trickle charger via point to point wireing...

 Since the group buy has a long lead time, this should all be done by that time.

 Also, DieInAFire and I agree that once we have a working prototype amp, we'll send it around to ask for criticisms and impressions. We want to figgure out what flaws this amp has, and fix that in component selection.

 PM me if you want to help out in the 'dev effort.


----------



## MASantos

C'mon! Show the pics!!


----------



## ATAT

Hey MASantos, I would post pics, but the thing is just too darn ugly right now. I had to make some real quick fixes on the board, and it looks real.. realllll bad. (i mean, worse than CMOY bad) 
 But I will take a pic when i clean it up..

 Also. If anyone has their "favorite opamp" / "favorite BUF634 replacement". We will test it out.. (or DiAF will)


----------



## MASantos

Quote:


  Originally Posted by *ATAT* 
_Also. If anyone has their "favorite opamp" / "favorite BUF634 replacement". We will test it out.. (or DiAF will)_

 


 2xOPA627 in a browndog soic adapter(2xsingle soic OPAMP to dual soic)


----------



## splaz

Cost much ? 

 Better make that quad stacked buffers too.


----------



## MASantos

Quote:


  Originally Posted by *splaz* 
_Cost much ? 

 Better make that quad stacked buffers too. 
	

	
	
		
		

		
		
	


	


_

 

WBT next gen RCA's, silver hookup wiring, custom build titanium enclosure,

 anything more?


----------



## rsabo

AD8397


----------



## cetoole

Quote:


  Originally Posted by *MASantos* 
_2xOPA627 in a browndog soic adapter(2xsingle soic OPAMP to dual soic)








_

 

Come on MASantos, be realistic.

 ATAT: What we all want to see is that amp mounted with class A discrete opamps, and jung discrete diamond buffers 
	

	
	
		
		

		
		
	


	




.


----------



## ATAT

I think rsabo wins the unrealistic request of the day award =p.

 Anyway, I hope you're not serious =p because I'll have to ask why... the buffers drive the current anyway.

 I think I can get the LMs to cooperate though.. they dont look that bad.. the key is the inner-band resistor R6.. by decreasing that, inner loop bandwith goes down, stability incresaess.

 Anyway, its likely not possible to use these high speed opamps in the ground channel for reasons of stability.

 We'll see tho.


----------



## ATAT

Cetoole - I think you CAN do a discrete diamond buffer.. 

 use one of http://www.logicalsys.com/painfo-vpa...-sof-d250-08/6

 and add a board on top.. I think you could do discrete opamps and buffers.

 probably because of the case size you woldn't be able to do that AND have 2x9v though.


----------



## Filburt

Quote:


  Originally Posted by *ATAT* 
_I think rsabo wins the unrealistic request of the day award =p.

 Anyway, I hope you're not serious =p because I'll have to ask why... the buffers drive the current anyway.

 I think I can get the LMs to cooperate though.. they dont look that bad.. the key is the inner-band resistor R6.. by decreasing that, inner loop bandwith goes down, stability incresaess.

 Anyway, its likely not possible to use these high speed opamps in the ground channel for reasons of stability.

 We'll see tho._

 

LM6172 is unity gain stable. LM7372 is even more stable at unity gain it appears.


----------



## ATAT

I've got it! I can put in glassman's buffers on this board.

 Here's how I intend to do it.. I'll buy ED83100-ND from digikey, dual-row headers for $14.20 (50 headers). Now, take 3 header / buffer, solder into pads, ignoring pad 1 and 8 (bandwith control and NC) (this should populate approximate 16 buffers, but whatever.)
 Then take something similar to glassman's buffers, and solder into the header.

 Should be no higher if I use a 2 layer topology.. 

 If anyone has a good discrete buffer schem, I'll appreciate it! 

 MOSFET? Glassman? Sijosae? I'm open to all suggestions.

 (also, how much current draw / money would you sacrifice for one of these? if no one else wants it, it becomes hard to pay the expensive proto fees for a tiny tiny buffer board).


----------



## MASantos

I would prefer to have a simple IC buffer. It's probably cheaper, easier to build(allowing more people to do it) and will not eat as much current as a discrete buffer allowing more battery life. 



  Quote:


  Originally Posted by *ATAT* 
_I've got it! I can put in glassman's buffers on this board.

 Here's how I intend to do it.. I'll buy ED83100-ND from digikey, dual-row headers for $14.20 (50 headers). Now, take 3 header / buffer, solder into pads, ignoring pad 1 and 8 (bandwith control and NC) (this should populate approximate 16 buffers, but whatever.)
 Then take something similar to glassman's buffers, and solder into the header.

 Should be no higher if I use a 2 layer topology.. 

 If anyone has a good discrete buffer schem, I'll appreciate it! 

 MOSFET? Glassman? Sijosae? I'm open to all suggestions.

 (also, how much current draw / money would you sacrifice for one of these? if no one else wants it, it becomes hard to pay the expensive proto fees for a tiny tiny buffer board)._


----------



## rsabo

why not just etch the buffer board yourself for prototyping? do it properly and it doesn't cost more than 10 dollars.

 mosfets? wouldn't that make it kind-of-sort-of a battery-powered portable M3?
  Quote:


  Originally Posted by *ATAT* 
_I've got it! I can put in glassman's buffers on this board.

 Here's how I intend to do it.. I'll buy ED83100-ND from digikey, dual-row headers for $14.20 (50 headers). Now, take 3 header / buffer, solder into pads, ignoring pad 1 and 8 (bandwith control and NC) (this should populate approximate 16 buffers, but whatever.)
 Then take something similar to glassman's buffers, and solder into the header.

 Should be no higher if I use a 2 layer topology.. 

 If anyone has a good discrete buffer schem, I'll appreciate it! 

 MOSFET? Glassman? Sijosae? I'm open to all suggestions.

 (also, how much current draw / money would you sacrifice for one of these? if no one else wants it, it becomes hard to pay the expensive proto fees for a tiny tiny buffer board)._


----------



## dhp

Quote:


  Originally Posted by *MASantos* 
_I would prefer to have a simple IC buffer. It's probably cheaper, easier to build(allowing more people to do it) and will not eat as much current as a discrete buffer allowing more battery life._

 

I dont get it, it would simply be an option


----------



## MASantos

Quote:


  Originally Posted by *DieInAFire* 
_I dont get it, it would simply be an option_

 

So it's a daugtherboard? I tought it would be the only option! If so then it is a good thing


----------



## cetoole

Quote:


  Originally Posted by *MASantos* 
_I would prefer to have a simple IC buffer. It's probably cheaper, easier to build(allowing more people to do it) and will not eat as much current as a discrete buffer allowing more battery life._

 

Great thing about discrete is, you choose the current draw. If its class B especially, they dont have to draw much at all, and are still efficient when just barely operating in class AB.

  Quote:


  Originally Posted by *rsabo* 
_mosfets? wouldn't that make it kind-of-sort-of a battery-powered portable M3?_

 

Yes, but only for a very short period of time. And to think, people complained about the battery life of the Pint, using only 2xAD8397. Class A mosfets will surely be much worse.


----------



## ATAT

Hey.. i'm up bright n early!

 The board is about 95% laye'd out (or so EAGLE tells me) there's one trace that's kinda tricky and i havent gotten right.

 As for now, I'm using Sijosae's buffer, modified. The schem was shamelessly ripped from Cetoole. It uses a Vishay Siliconix SST502 to bias the buffer and uses TO-92 output stages.

 The whole thing measures approx .4x.5 inches. It should fit perfectly with the headers i suggested


 and yes, this is more of an optional daughterboard project.. most people will probably choose to populate their ppas with normal buffers, but like the people hwo used glassman's discretes, PPAS will have a similar option.


----------



## mono

Quote:


  Originally Posted by *MASantos* 
_I would prefer to have a simple IC buffer. It's probably cheaper, easier to build(allowing more people to do it) and will not eat as much current as a discrete buffer allowing more battery life._

 

There is no reason a discrete would need use more current than BUF634 unless it's your choice to do it. It's even possible the discrete might continue working down to a lower voltage.

 Cost can be very similar if it's simple, but frankly I'd not want it on a riser-adapter onto surface mount pads, making it the fragile part of the amp.


----------



## rsabo

Quote:


  Originally Posted by *cetoole* 
_Yes, but only for a very short period of time. And to think, people complained about the battery life of the Pint, using only 2xAD8397. Class A mosfets will surely be much worse._

 

hmmm, but what about sticking a ppas (with, say, those mosfets) in with a DAC & wall power them? that has the potential to be a very small, very awesome sounding rig.


----------



## cetoole

Quote:


  Originally Posted by *rsabo* 
_hmmm, but what about sticking a ppas (with, say, those mosfets) in with a DAC & wall power them? that has the potential to be a very small, very awesome sounding rig._

 

It would be interesting, but remember, mosfets will need heatsinking, as they dissipate a fair amount of heat, and as this will most likely be mounted to so8 pads, which isnt very secure, I would feel pretty uncomfortable doing this, unless the mosfets were heatsinked to the case, or something else that supports its own weight.


----------



## dhp

Quote:


  Originally Posted by *cetoole* 
_It would be interesting, but remember, mosfets will need heatsinking, as they dissipate a fair amount of heat, and as this will most likely be mounted to so8 pads, which isnt very secure, I would feel pretty uncomfortable doing this, unless the mosfets were heatsinked to the case, or something else that supports its own weight._

 

maybe we could hook up a fan


----------



## ATAT

Thanks to Cetoole's godly layout powers, diamond buffers are done. 

 This is based off of cetoole's db schem that he used on his discrete buffer'd pocket amp. SST502s bias the buffer into class-A. TO92 output transistors nad the like.

 The DBs do not affect height at all (cap is the highest component, and hte other side has empty space) and fits snugly 

 Pics.

 First, the Buffer pic.






 measures .4 x .5

 Pics of buffer mounted in board










 Of course, this buffer can be used on any SO-8 pad (ie, on the mint).

 I'll order some on the $33 proto, but sadly, I wont be able to test it out in japan (i have no clue how to get parts there..) DieInAFire will have that fun =p


 Cetoole thinks MOSFET output stage is impossible. I dont. Time to prove him wrong =)


----------



## dhp

Quote:


  Originally Posted by *ATAT* 
_Thanks to Cetoole's godly layout powers, diamond buffers are done. 

 This is based off of cetoole's db schem that he used on his discrete buffer'd pocket amp. SST502s bias the buffer into class-A. TO92 output transistors nad the like.

 The DBs do not affect height at all (cap is the highest component, and hte other side has empty space) and fits snugly 
 Of course, this buffer can be used on any SO-8 pad (ie, on the mint).

 I'll order some on the $33 proto, but sadly, I wont be able to test it out in japan (i have no clue how to get parts there..) *DieInAFire will have that fun =p*

 Cetoole thinks MOSFET output stage is impossible. I dont. Time to prove him wrong =)_

 



 Hrm, I'm going to be away in Argentina during July, so I suppose during that time it'll be the lead time for the board production =]


----------



## NeilR

Quote:


  Originally Posted by *ATAT* 
_Cetoole thinks MOSFET output stage is impossible. I dont. Time to prove him wrong =)_

 

You're all mad


----------



## dhp

Quote:


  Originally Posted by *NeilR* 
_You're all mad 
	

	
	
		
		

		
		
	


	


_

 

hmm, perhaps we could use mosfet outputs for a home-based module? seeing as in a portable setup, you'd be mad to even want to use mosfet outputs... although I'm not sure where the heat would go


----------



## Filburt

I so have to build it with diamond buffers. This project is starting to just scream excess


----------



## cire

Quote:


  Originally Posted by *DieInAFire* 
_although I'm not sure where the heat would go_

 

hand warmer, anyone?


----------



## cetoole

Quote:


  Originally Posted by *ATAT* 
_Cetoole thinks MOSFET output stage is impossible. I dont. Time to prove him wrong =)_

 

I dont feel that it is impossible, just unfeasible. Issues like current draw and heatsinking make mosfet output stages unfriendly to portable use.


----------



## rsabo

Quote:


  Originally Posted by *cetoole* 
_I dont feel that it is impossible, just unfeasible. Issues like current draw and heatsinking make mosfet output stages unfriendly to portable use._

 

re the heatsink so8 pads:
 glancing at heatsinks, it looks like that a good number of them have more than one set of holes. would it be feasable to bolt something like a spacer, or a standoff, or something between the case and one of those extra holes? I would think that that would alleviate some of the weight issues, as well as provide some extra cooling.

 (this is insane for a portable amp, I know)


----------



## cetoole

Quote:


  Originally Posted by *rsabo* 
_re the heatsink so8 pads:
 glancing at heatsinks, it looks like that a good number of them have more than one set of holes. would it be feasable to bolt something like a spacer, or a standoff, or something between the case and one of those extra holes? I would think that that would alleviate some of the weight issues, as well as provide some extra cooling.

 (this is insane for a portable amp, I know)_

 

If you can drill the tolerances tight enough, I see no reason this wouldnt be fine, though I would prefer to have it attached to the pcb through hole, to aleviate the risk of the board moving with respect to the buffers. This is mainly a concert with cases like what the PPAS is targeted at, the mint tin, which is pretty weak, and, IMO, unsuitable for use as a portable amp case. Its one thing if the case gets damaged a bit, its another if it bends, and tears the buffers and pads off the amp pcb.


----------



## dhp

Quote:


  Originally Posted by *cetoole* 
_If you can drill the tolerances tight enough, I see no reason this wouldnt be fine, though I would prefer to have it attached to the pcb through hole, to aleviate the risk of the board moving with respect to the buffers. This is mainly a concert with cases like what the PPAS is targeted at, the mint tin, which is pretty weak, and, IMO, unsuitable for use as a portable amp case. Its one thing if the case gets damaged a bit, its another if it bends, and tears the buffers and pads off the amp pcb._

 

I don't think anyone would be crazy enough to use mosfet outputs in a fully portable setup.....


----------



## rsabo

Quote:


  Originally Posted by *DieInAFire* 
_I don't think anyone would be crazy enough to use mosfet outputs in a fully portable setup..... 
	

	
	
		
		

		
		
	


	


_

 

backpacks are portable, car batteries are portable.

 think about it: truly stellar portable sound and a workout all in one!


----------



## ATAT

Rsabo.. if you ever want to use a mosfet output stage.. here's what would be needed

 a). a large battery, Lipo would be required if you wanted to use it portably (not trans-portably, then just use SLAs).

 b). Heatsinks. I think you could.. basically the mosfets should be connected via wire to the buffer board, and the mosfets bolted to the case, which should have a heatsink attached to it ..

 so Buffer board pads -> wire -> MOSFET -> Case -> Heatsink.

 IMO, too much effort. But if you want, I'll lay out a mosfet push-pull output stage and fab you a set or two.. 


 Actually.. the more I think about it.. the more I want to do a mint-tin based home amp. Alright. make that 2 sets of mosfet boards =p


----------



## dhp

meh, 2 9 volt batteries won't fit with the DB boards, etc. so you may as well fab a nicer case than the mint tin, ATAT


----------



## ATAT

Oh sneaky.. trying to make me get up and work on a 3 axis CNC..

 But that wont quite work.. sadly for you, it'll still fit with 2x9v. I checked already =p


----------



## dhp

Quote:


  Originally Posted by *ATAT* 
_Oh sneaky.. trying to make me get up and work on a 3 axis CNC..

 But that wont quite work.. sadly for you, it'll still fit with 2x9v. I checked already =p_

 

with the MOSFET outputs?


----------



## ATAT

oh. 

 I thought you meant the other board.

 I guess yeah, for the M^3ified one, I'll have to get a nicer case =)


----------



## mono

The typical way to mount parts like the mosfets would be to allow a perimeter around the edge of the board, and a heatsink "fence" that bends at least around one 90' corner so it has 2 axis support when soldered into the board holes, those holes being at least at the ends if not the middle too. However, this doesn't resolve the issue of heat buildup in the small case, making any 'sink less effective and necessarily larger.


----------



## K2Grey

Ermm... what would be the battery life on this kind of thing? Forgive me if this has already been said, my search-fu is weak because this wireless connection is horrible and I can't go through the whole thread without taking a while


----------



## dhp

Quote:


  Originally Posted by *K2Grey* 
_Ermm... what would be the battery life on this kind of thing? Forgive me if this has already been said, my search-fu is weak because this wireless connection is horrible and I can't go through the whole thread without taking a while _

 

with BUF634u on low bandwidth mode, <20ma
 although we havent tested with buf634 on high bandwidth mode and haven't tested any other buffers yet


----------



## ATAT

Hey K2.. No problem.

 This was an early concern since the buffers I planned to use (LM6321) were put down for 10mA draw each.. 

 But my prototype is running a AD8620 / 10 setup, BUF634 and draws about 10-20mA Total. That translates into about 20 hours runtime. This is the most conservative setup.

 (FYI, my prototype has been running for 3 days, and its the only amp i've used during that time..)

 Add class-A biasing, add 3more mA. (~18mA total) still 'round 20 hours

 Open Bandmode (~40mA) round 10 hours

 LM6321 (~50mA) less than 10.

 Discrete buffers (~???) Assume something like 100mA, probably about 5 hours then.

 (NB.. last numbers are extrapolations.. the first one is measured)


----------



## dhp

Quote:


  Originally Posted by *ATAT* 
_Hey K2.. No problem.

 This was an early concern since the buffers I planned to use (LM6321) were put down for 10mA draw each.. 

 But my prototype is running a AD8620 / 10 setup, BUF634 and draws about 10-20mA Total. That translates into about 20 hours runtime. This is the most conservative setup.

 (FYI, my prototype has been running for 3 days, and its the only amp i've used during that time..)

 Add class-A biasing, add 3more mA. (~18mA total) still 'round 20 hours

 Open Bandmode (~40mA) round 10 hours

 LM6321 (~50mA) less than 10.

 Discrete buffers (~???) Assume something like 100mA, probably about 5 hours then.

 (NB.. last numbers are extrapolations.. the first one is measured)_

 

i think your run times are exaggerated


----------



## ATAT

Wow. within 20 seconds of posting, 2 people say the same thing.

 I assume a 500mAh Alkaline battery.

 A 250mAh NiMh will have half that time

 A ultralife 1.2Ah battery will double that time.



 Also- Swapped my opamps. I like this better.. OPA2132 -> AD8620. The 8620 is much much nicer.. not as shrilly, but has a bit more oomph on the low end =)


----------



## ATAT

Pictars posted.
















 Overall size pic.







 You can see all the fixes i made on there that you dont have to make..

 THe solder bridge at the bottom left was there to jumper 10 ohm resistor..
 The pseudo-deadbug soldering of AD8620 was to swap 2 pins (inverting and nonintering)
 The red wire jumpering vgnd to ground is to prevent floating ground channel.


----------



## digitalmind

Wow that's small! Great work, will deffinitly keep watching this one.


----------



## cire

i can tell you this, it definitely looked a lot better in person


----------



## rsabo

Very nice.


----------



## NeilR

I can't wait to see the build instructions for this, especially the air wired chip 
	

	
	
		
		

		
			





 Just kidding! Very cool work arounds for the board issues. 

 Regards,
 Neil


----------



## dhp

well, it's a good thing he posted those pics voluntarily, otherwise I woudl've taken pics and posted myself


----------



## ozshadow

Please tell me theres a Browndog adapator for that chip


----------



## ATAT

Heh. That's not necessary on the final board (thankfully =p) ive fixed all the issues so no air-wireing..

 Anyway. Which would yall prefer, a PPL / Mono style buffer or the one we have now? (Sijosae style Class-AB Emitter Follower buffer).


----------



## ozshadow

Whats the current parts list and if that buffer sounds good, use it


----------



## jl123

I see a new soldering technology on the rise.


----------



## DaKi][er

Quote:


  Originally Posted by *jl123* 
_I see a new soldering technology on the rise._

 

Yea, how to destroy the advantage of lower inductance in the leads and packages of SMD devices


----------



## kramer5150

ATAT.... YGPM


----------



## Filburt

Quote:


  Originally Posted by *ATAT* 
_Heh. That's not necessary on the final board (thankfully =p) ive fixed all the issues so no air-wireing..

 Anyway. Which would yall prefer, a PPL / Mono style buffer or the one we have now? (Sijosae style Class-AB Emitter Follower buffer)._

 

PPL Buffer! 
	

	
	
		
		

		
		
	


	




 Meh, the E-F buffer would probably work, too, but it's not as exciting...


----------



## dhp

proto is arriving tomorrow


----------



## Polaris111688

If you're doing a ppl/mono style buffer daughter board, might as well call it mini-PPAv2. I'm freaking impressed by this project!


----------



## dhp

Quote:


  Originally Posted by *Polaris111688* 
_If you're doing a ppl/mono style buffer daughter board, might as well call it mini-PPAv2. I'm freaking impressed by this project!_

 

well, the DB are an option, so you could call it PPAv1 with diamond buffers =]


----------



## 00940

Quote:


  Originally Posted by *ATAT* 
_Also- Swapped my opamps. I like this better.. OPA2132 -> AD8620. The 8620 is much much nicer.. not as shrilly, but has a bit more oomph on the low end =)_

 

The OPA2132 shrillly ???? I've the feeling your opamp was oscillating. Do you have decoupling caps near the opamps ?


----------



## ozshadow

I'm looking at these cases for this, unless someone can point me towards some styled like Ray Samuels sr-71 type case.

http://www.minute-man.com/acatalog/S...nclosures.html

 Then again, I may go with a wood case.


----------



## ATAT

0094. absolutely sure no oscillation. it doesnt show up on the 'scope and the draw is just about minimal expected.

 I think I just have tin ears.

 Oz - Get the Hammond 1455 Series.


----------



## ozshadow

hehe, just found that actually.

 1455J1201BK


----------



## ozshadow

Was looking at your BOM: Any reason not to change the 330uf caps to 470uf caps ? Nichicon offers many in 8mm diameter like the 330's you have listed. The 470's are 16v, but your 330's listed are 25v but the 100's are 10v.

 Was looking at 647-UPW1C471MPD6 but there are plenty of em in 8x12.5 or 8x15 in 470uf


----------



## dhp

Quote:


  Originally Posted by *ozshadow* 
_Was looking at your BOM: Any reason not to change the 330uf caps to 470uf caps ? Nichicon offers many in 8mm diameter like the 330's you have listed. The 470's are 16v, but your 330's listed are 25v but the 100's are 10v.

 Was looking at 647-UPW1C471MPD6 but there are plenty of em in 8x12.5 or 8x15 in 470uf_

 

470uF in 16V means you can't use 2x 9V batteries


----------



## cire

Quote:


  Originally Posted by *DieInAFire* 
_470uF in 16V means you can't use 2x 9V batteries_

 

well you can, you'll just be in for a nice fireworks show


----------



## ozshadow

Yup, you're fast. Didn't even have time to remove it. Was just looking at the schematic again and realized the voltage had not split yet.


----------



## cire

Quote:


  Originally Posted by *ozshadow* 
_Was just looking at the schematic again and realized the voltage had not split yet._

 

should've been obvious. there's a reason why there's only one power cap


----------



## ozshadow

*scratch head*

 I see two 330uf power caps.


----------



## NeilR

Looking at the BOM's... the 4.42K 805 part spec'd for the "no compromise" BOM, Mouser part# 71-TNPW0805-4K42-BETY is non-stocked and has a minimum order of 1000 pieces. Group buy in order here ? 






 Not that I would use such boutique parts, mind you 
	

	
	
		
		

		
		
	


	




 Regards,
 Neil


----------



## ozshadow

Excel BOM from website has it listed as 71-CRCW0805-4.32K


----------



## NeilR

Quote:


  Originally Posted by *ozshadow* 
_Excel BOM from website has it listed as 71-CRCW0805-4.32K_

 

You're looking at the Ghetto Version. Real men click the 3rd tab at the bottom of the sheet and build that one.


----------



## ozshadow

That one needs these jacks from Digikey: CP-43502PM-ND Which will finally be available again on the 12th.

 I click poor man's tab, and spurge on the middle class one. I ignore the third tab.


----------



## NeilR

Quote:


  Originally Posted by *ozshadow* 
_That one needs these jacks from Digikey: CP-43502PM-ND Which will finally be available again on the 12th.

 I click poor man's tab, and spurge on the middle class one. I ignore the third tab._

 

Actually those Real Man's CP-43502 jacks won't work too well in a metal case....

 I got interested in the 3rd tab because I was curious why I'd want to spend up to a buck each for resistors and checked out the specs. It's an interesting solution to the matching problem but I always order at least 2X what I need for SMD parts because I never want to have to be crawling around on the floor with a magnifying glass frantically looking for my last 805 part that just launched out of my tweezers: k1000:


----------



## mono

Quote:


  Originally Posted by *00940* 
_The OPA2132 shrillly ???? I've the feeling your opamp was oscillating. Do you have decoupling caps near the opamps ?_

 


 it seems like it would be quite a trick to have decoupling caps near the opamp when it's "spiderized" as in the picture.


----------



## threepointone

vishay alternatives, straight from catalog
 -------------------

 IRC thin film 0805, .1%, 4.42k 25ppm, seems high quality
 66-PFC08C-4.42k

 Xicon thin film 0805, .1%, 4.53k 10ppm, generic mouser passives mfr
 288-4.53k

 KOA Speer thin film 0805, .1%, 4.42k 25ppm, mil-spec
 660-RN732ALTD4421

 the KOA Speer thin-film seems like the best one, maybe even better than the vishay ones--according to the datasheets, the KOA Speer resistors have lower current noise than the vishays.

 The vishay thin-film is rated around -26dB for this particular resistance, while the KOA speer is around nearly -40dB (if you believe the spec sheets, of course--but then again, these are mil-spec) so, you might want to replace all the thin film resistors on the BOM to the KOA mil-spec ones; they're cheaper, too.


----------



## ATAT

Woah. I've missed quite a discussion.

 You can't use a lower voltage cap. that discussion's done

 But I think you Can use a high quality cap (like the Cerafine 470uF) and lay it down sideways on the board.. thus having one good cap, as opposed to two .. well. good caps =p

 Good call on the parts selection by the way. You're absolutely right. this is why I shouldnt make my BoM based on the Mouser catalog (paper version).

 ATAT.


----------



## ATAT

Also. List of opamps to test has been just about made.

 Thanks alot to filburt and his opamp suggestions. we'll try and test out all of them, and post a compatibiilty note on the website

 Cheers!

 ATAT


----------



## ozshadow

I am REALLY excited about this. I have several cmoys laying around in various formats and all have worked great, but none have a really nice enclosure or nice jacks - just the $3 RS ones.

 I intend to make this over the next few months with all nice components and that nice metal hammond case.


----------



## ATAT

The Finalized board has arrived at DieInAFire's, its assembled and working flawelessly.

 Victory!

 Also, ground is stable even with the ultrafast THS4631s /I/ think it improves soundstaging. DieInAFire thinks its overcompensating. Interpret as you wish.


----------



## ATAT

Doublepost


----------



## Filburt

THS4631 eh? Very cool. I wonder how that'll mate with some of the other op-amps I suggested.


----------



## ozshadow

What buffer formats have yall tried so far ?


----------



## Tedro

have you been able to use the original buffer from National that you had origianaly wanted to use? Now that I have some on hand, I would like to use them. Is that buffer stable and a drop in for the TI buffer?


----------



## ozshadow

Can you please give us the rough measurements of the actual finished board with components ? with maximum width being to the mounting surface of the pot ?


 I am case shopping !


----------



## Filburt

It's about the size of the PINT board except for a bit shorter in length and slightly taller in height, it seems.


----------



## ozshadow

Guess that means the 1455J1201 is about the smallest you can do and squeeze in two 9v batteries. 4.72x2.75x0.95 (120x70x24) internally.

 I am thinking it might be possible with the extra room to squeeze in some 10x12.5 25v 470uf Nichicon FW series caps. Any particular reason sound-wise for choosing the PW series ?


----------



## ATAT

2.166 x .777 
 Tolerance of 5 mils.

 10x12.5 wont fit in that size. If you wanted, you could bend the leads and fit it without a problem, but I'd only take the pain to do that for something like an ELNA.

 the footprint is 8x10 for each power cap. 



 Tedro - I haven't the chance. I had a bunch of problems with the board, and took off the buffer the first thing. I now have only 2 working buffers so I'm unable to test. That will be the first thing I'll try though.


----------



## ozshadow

I looked at the Elna Cerafine's and Nichicon Muse series caps - I am guessing they are a no go. Bent leads can be done, but at 20 mm tall minimum, it would probably not fit that case with bent lead spacing + board + underside comps + insulating material.


----------



## Tedro

Quote:


  Originally Posted by *ATAT* 
_2.166 x .777 
 Tolerance of 5 mils.

 10x12.5 wont fit in that size. If you wanted, you could bend the leads and fit it without a problem, but I'd only take the pain to do that for something like an ELNA.

 the footprint is 8x10 for each power cap. 



 Tedro - I haven't the chance. I had a bunch of problems with the board, and took off the buffer the first thing. I now have only 2 working buffers so I'm unable to test. That will be the first thing I'll try though._

 

I have most the parts and the buffers so I would be able to test this out, one of your beta testers. If you have something for me to test I would be able to do so, I am an experienced builder. Let me know


----------



## ozshadow

How does it sound ? I am probably going with the 8610/8620 combo and buf634's. The 2227 chips are just too light on bass for me, but I do have some 2107's on their way. No idea how they sound yet.


----------



## mono

Quote:


  Originally Posted by *ozshadow* 
_How does it sound ? I am probably going with the 8610/8620 combo and buf634's. The 2227 chips are just too light on bass for me, but I do have some 2107's on their way. No idea how they sound yet._

 

I see in your sig the CMOY with 2227, is that where you make generalization about lack of bass with 2227? If so, do not compare any opamp in an CMOY to one behind a buffer, a cmoy mostly tells us how the opamp drives a load, not it's ultimate performance in other topologies. Not to disagree entirely about 2227, but mostly I note less detail as I tend to with all the lower bandwidth opamps.


----------



## ATAT

The 2107 is the opamp of choice for filburt. he's been raving about it, and since the 2107 is a low output current, high precision, low noise, its basically nearly ideal for the PPAS-type topology (compared to high current, low precision stuff..). 

 Of course, this is all untested and therefore just speculation. but as soon as I get my boards over in japan, I'll test out the follow'in

 Opamps - 

 Signals -
 AD8620 
 OPA2107
 OPA2227
 OPA2134
 AD8066
 LM6171 (dual)

 Grounds - 
 THS4621 (or something.. forgot the exact #..)
 LM6171 (yes, its an "unstable" opamp..)
 AD8610
 LM7171

 Buffers - 
 BUF634
 OPA551
 LM6321

 Any other suggestions?


----------



## rsabo

Quote:


  Originally Posted by *ATAT* 
_The 2107 is the opamp of choice for filburt. he's been raving about it, and since the 2107 is a low output current, high precision, low noise, its basically nearly ideal for the PPAS-type topology (compared to high current, low precision stuff..). 

 Of course, this is all untested and therefore just speculation. but as soon as I get my boards over in japan, I'll test out the follow'in

 Opamps - 

 Signals -
 AD8620 
 OPA2107
 OPA2227
 OPA2134
 AD8066
 LM6171 (dual)

 Grounds - 
 THS4621 (or something.. forgot the exact #..)
 LM6171 (yes, its an "unstable" opamp..)
 AD8610
 LM7171

 Buffers - 
 BUF634
 OPA551
 LM6321

 Any other suggestions?_

 

Consider also that the header-to-smd thing you have set up for the diamond buffer boards most likely allows the use of buffers with totally different pinouts. The only experience I have with something like that is the HA-5002 (which sounds beautiful with the AD8610/20 family, by the way). I'll try to whip up something to that effect in eagle right now. You're using 0805 resistors, correct?

 Can anything else be done in this way (that would be worth it?)


----------



## ATAT

Hmm. Rsabo, not sure if you can use SMD ones with different pinouts.. (unless you flush-cut the headers) 

 basically the headers are in the center of the board, so if you have SMD chips, the headers will be in the way, unless you cut them flush to the board. I think you can easily use DIP buffers though. I think using the intersils would be a fun thing to do..I'll whip some board designs up and add them to the proto panel.


----------



## rsabo

think I beat you to it, found out that SMD wouldn't work w/ the headers when I did it this morning, so it uses a dip w/ smd resistor. I'll PM you the file so you can check it to see if it meets your expectations.


----------



## ozshadow

If all goes well, I plan to mount this board like this with these caps. All should be pretty much to scale.


----------



## ATAT

Hmm. Alright. Ozshadow - that looks pretty reasonable to me. Are you going to use battery holders? I would want to use them in that configuration, if the 9vs slam into the PCB, bad things could happen..

 Also, you might want to consider upping the capacitance on the opamp rails too (the smaller capacitors).. these will have a greater effect than the buffer caps since the opamp rails will be current limited by the TLE.


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## ozshadow

Yes, I plan to include some type of barrier between the batteries and the amp. The case I have in mind has a sliding floor. I am thinking a toolbox divider with the sticky tape on bottom will do well as it should not need much trimming.

 As for the 100uf caps, yes, I fully intend to match them using Cerafines as well in as big as I can squeeze in there. I am pretty sure I can get two 220's in there, but if at all possible, I'll get some 470's in there. Whatever I can possible get in that case with even wire configs, I will. I may go with 4 470's in a similar setup but with the top two shifted 1/2 a width.


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## ATAT

ozshadow - Be sure not to go overboard with the rail caps.. here's the tradeoff.

 1). too small -> not enough current output on large transients and the opamps clip

 2). too large -> it takes a while for the caps to charge on startup, because of the JFETs which limit current, this is even more so. This can lock up some cranky opamps and make them dump rail voltage. this WILL destroy your headphones.

 The only opamp ive been able to do #2 on is the AD843.. but others may be similar. proceed with caution. 

 Its unlikely that #1 or 2 will happen, but be safe and dont be riduclous (400 will probably be okay.. 2000uF on the opamp rails? noo...)


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## ozshadow

LOL, no space for that. By 4x 470, meant 2 470uf instead of two stock 330 uf, and 2 470 uf instead of two stock 100 uf. Not 2000 on the rails. 

 Actually, the most I can honestly see spacewise so far is 2 x 220's on the rails, and the 2 x 1000's right off the batteries. But I really want to use cerafines in this.


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## ATAT

I suggest you use 2x470 on the rails (a good 940 uF..) and 2x220s on the opamp.. why? because 2x470 on the opamp would give you something like .1 second rise time to 18 volts, this may or may not be bad for you, and I seriously doubt your opamp will need the 470uF (compared to 220) mainly because of the buffered design.


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## nysulli

haven't heard any news on the diamond buffers in a little while, just wondering whats going on in that front

 or, whats everyones thoughts on trying to use some of the millet hybrid diamond buffers, as i happen to have a few of those sitting around


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## NeilR

Quote:


  Originally Posted by *nysulli* 
_haven't heard any news on the diamond buffers in a little while, just wondering whats going on in that front

 or, whats everyones thoughts on trying to use some of the millet hybrid diamond buffers, as i happen to have a few of those sitting around_

 

I would also like to make use of my Millet diamond buffer boards. Those are nice buffers.


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## ATAT

NeilR- I agree, the board is one of the better done diamond buffers. there are two reasons I didnt / couldnt implement something like that. My board uses a more simple (but not too much worse..) CRD setup for biasing. and it also removes a few of the transistors.. IMHO, it shouldn't matter that much

 but if you want to use your boards, note well that you'll have to do some hackery to get it to work. 

 First, get a suitable buffer for ground. (the millet one is only 2 channel)

 Second, put the header onto the SOIC-8 pins, and then use wire-wrap tool / wire to connect the holes on the buffer board..

 This will of course require a bigger enclosure, as the diamond buffer board is pretty big.


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## NeilR

Quote:


  Originally Posted by *ATAT* 
_NeilR- I agree, the board is one of the better done diamond buffers. there are two reasons I didnt / couldnt implement something like that. My board uses a more simple (but not too much worse..) CRD setup for biasing. and it also removes a few of the transistors.. IMHO, it shouldn't matter that much

 but if you want to use your boards, note well that you'll have to do some hackery to get it to work. 

 First, get a suitable buffer for ground. (the millet one is only 2 channel)

 Second, put the header onto the SOIC-8 pins, and then use wire-wrap tool / wire to connect the holes on the buffer board..

 This will of course require a bigger enclosure, as the diamond buffer board is pretty big._

 

ATAT- I know that this is not the right board for the Millet buffers. There is a little conflict between building a circuit on a board the size of a stick of gum and all the embellishments we like to do 
	

	
	
		
		

		
		
	


	




 As far as the ground channel, I would assume that the Millet board would have to be cut in half, and 3 of the 4 halves of two boards would be required for a ground channel, amp.

 My comment was more of a general nature aimed at whoever is working on larger boards.

 I'm not familiar with this header thing... can you point me to a specific part? Are you thinking about a standard SIP header?

 Regards,
 Neil


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## Filburt

Quote:


  Originally Posted by *ozshadow* 
_LOL, no space for that. By 4x 470, meant 2 470uf instead of two stock 330 uf, and 2 470 uf instead of two stock 100 uf. Not 2000 on the rails. 

 Actually, the most I can honestly see spacewise so far is 2 x 220's on the rails, and the 2 x 1000's right off the batteries. But I really want to use cerafines in this._

 

Why do you want to use Cerafines? They aren't handling anything in the signal path. What is most optimal in terms of performance is using low ESR caps designed for rail supply etc. Try something like Matsu****a/Panasonic FC or FM or Nichicon UPW.


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## Filburt

Quote:


  Originally Posted by *ATAT* 
_The 2107 is the opamp of choice for filburt. he's been raving about it, and since the 2107 is a low output current, high precision, low noise, its basically nearly ideal for the PPAS-type topology (compared to high current, low precision stuff..). 

 Of course, this is all untested and therefore just speculation. but as soon as I get my boards over in japan, I'll test out the follow'in

 Opamps - 

 Signals -
 AD8620 
 OPA2107
 OPA2227
 OPA2134
 AD8066
 LM6171 (dual)

 Grounds - 
 THS4621 (or something.. forgot the exact #..)
 LM6171 (yes, its an "unstable" opamp..)
 AD8610
 LM7171

 Buffers - 
 BUF634
 OPA551
 LM6321

 Any other suggestions?_

 

The dual LM6171 is the 6172. I do not recommend the OPA551 unless you absolutely must use it as it's too slow for most of the op-amps we're looking to couple with it.

 Hopefully the LMH6321 will sound more like the LM6171/2 sonically than the BUF634 as, IMHO, the BUF634's colouration of the sound isn't particularly suited to some of these op-amps. I don't personally like the 634 on practically any amp I've ever heard with it, and the ones I didn't dislike it with I still felt were lacking in some manner, so I'm probably going to stick with the LMH6321 or something else if possible (and provided they sound better).

 Another op-amp you can try, if you can restrain yourself from using 2x9v (12v supply max) is the LMH6622.


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## ozshadow

When is Die returning home and any eta on when the boards will be finished up at the shop ?


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## ozshadow

Are teh Intersil HA3-5002 buffers used in the original PPA possible for this ? I will have to lean on your observations soundwise. I have yet to hear anything with a buf634 buffer, but comments about a veiled sound do not sound great - especially for $8 each.


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## ATAT

Oz - I dont find the BUFs particularly "veiled".. filburt hates the BUFs, I find em just fine.

 The intersils can be used via adaptor. rsabo made a pretty good intersil -> SOIC adaptor which I'll make a few of..

 ETA on boards is 8 days and counting + 3 days for shipping to Die's place.

 Filb - 

 The OPA551 is basically for compatibility testing, as the OPA seems more abundant and some may want to use it. 

 and if I was limited to 9v only, there'd be a BUNCH more opamps id like to test, but i just dont have the time / boards to do that.


 NeilR- 

 There is a specific set of DIP headers that are high-density and have the same spacing as the SOIC pads. You bend out the leads on the pads and you basically convert SOIC to DIP (not DIP spacing though..)


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## Filburt

Okay so I finally got time to actually troubleshoot daniel's PPAS that I received where the right channel wasn't working. Wow, I am lucky I didn't kill my super-secret Technics earbuds with this thing. Offset on the right was 5,8v (yes, that would be 5800mV). Left was 0,03mV. Although the BUF634 current limits, so that's probably why nothing bad happened to them...they still sound really sweet as far as earbuds go ^_^

 Anyhow, got them both down to 0,02ish mV, so I'm probably good to go there.

 The sound? Pretty impressive. Definitely has that BUF634 sound going on, but I guess I can tolerate it. Sounds worlds better to me than the MINT w/ OPA2132s and BUF634s. Has high levels of detail and stereo/instrument separation and imaging. It's quick as well, and has a lot of power on tap from what I can tell.

 Configured as follows (by Daniel): OPA2132 on L/R, BUF634s, THS4631 on ground. 2x9v. I'm definitely glad I ordered several boards. This thing will be a whole lot of fun. I'm starting to wish I'd ordered more.

 What I'm going to try eventually, probably:

 OPA2107 on the L/R on this amp, and then OPA2107 w/ LM6171 or THS4631 on ground and LMH6321 as buffer. Maybe try discrete after that.


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## ozshadow

I got several 2107's in the mail right this minute. Let me know how that works out - I have two boards coming to me. One will be 8620, the other, I dunno - whatever gets praised enough !


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## Filburt

Quote:


  Originally Posted by *ozshadow* 
_I got several 2107's in the mail right this minute. Let me know how that works out - I have two boards coming to me. One will be 8620, the other, I dunno - whatever gets praised enough !_

 

How many? Willing to share (sell)?


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## ozshadow

Well, by several, I meant 3. I want to play around with them first. If I do not like em, I'll pass them along.


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## Filburt

Quote:


  Originally Posted by *ozshadow* 
_Well, by several, I meant 3. I want to play around with them first. If I do not like em, I'll pass them along._

 

K. I just compared them to 627s...they sound fairly similar. The 627s are probably more neutral/accurate and a bit more detailed.


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## ozshadow

Who has the Buf634u's now ?

 Digikey lists them currently at 06/19/2006 Hope they get a lot !


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## ATAT

DieInAFire intends to buy a batch of em I think..

 I get my ICs from DiAF and Cire so I have no clue where .. you should PM them


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## ozshadow

Are there any jumpers in the path from the two R4's to the outputs ? If not, probably a little late now, but a jumper spot would have given the option of tieing in an optional bass boost circuit.

 Something like this ?

http://ozpk.ginnypotter.com/bassboost.jpg


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## ATAT

Nop. No tie outs there.. 

 Honestly, I'm not a big fan of bass-boosting circits (i think digital bass boost is better.. ) but if you really want, you could take the taps off of the SMD pads.. (i can make a writeup on how to do it.. but its really "no duh".. and its pretty easy with wire-wrap wire.


 by the way, if you just want bass boost on all the time, put a cap on top of the resistor and solder both on in parallel =p

 *edit* on second thought the ^ above wont work at all. NVM.


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## wowie11

Hey Dieinafire...how does the PPAS sound compared to your mini^3ified PINT?


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## ozshadow

Is this the week coming up that Die receives the boards back ?

 I gotta get to planning parts buys !


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## dhp

boards will be shipping out wednesday of this week if everything goes as planned. Then we play the waiting game


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## ATAT

great.. the one week waiting game for me..

 Either way, when the boards arrive, it'd be nice if one of you could take pictars at every step and send them to me (or upload em to photobucket) so that the first build goes painless for all of us.. 

 There's a few tricky parts of the build that you could inadvertently mess up.. the SOT-23 pads are so close together that they form a grid.. you can offset your transistors and have to end up desoldeirng the SST-310s (Pain in the ass) you could also flip the tantalum capaictors (oh what fun). 

 The silkscreen on the back is kinda scrweed up (ie no component mask.. sorry.. I have no idea how that happened.. it is on the gerber =/) and on the front, the + silk screen is covered by the pad for tantalum caps.. so I'll need someone who gets it early (ahem .. filburt? =p) to post some pictars. 

 Also, if you want to make sure your board works (ie troubleshooting ease rather than building ease) then build the power supply section first.. that way you can check the PSU and then check the audio section =)

 Good luck! I'll probably be one of the last to build the PPAS thanks to my overseas locale.


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## Filburt

Found a new chip to try - OPA2822. I found it while looking for a replacement for the I/V converter or line driver...not sure which...on my PCDP which currently has a JRC 2100A in it which is the same thing as the NJM2100.


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## ATAT

According to Daniel, Parts should ship tomorrow morning.. I'll start up a build thread when all boards are shipped... 

 Filburt - 2822 looks interesting, I'll build one with that if I can find that opamp at akihabara.


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## Teerawit

Hey guys I just got back from a long hiatus so I don't really want to read 13 pages, so I have this question.....is this project still "beta" or are the boards of a final layout? I'm not sure I understand ATAT's sig.


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## Filburt

Just make sure you don't try to run the 2822 on 2x9v as it's a low voltage part. I thought it might be something neat to try for those who want to run on 4 AAAs or 1x9v.


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## jl123

How bout the lm6171. What are some thoughts on it?


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## Filburt

Quote:


  Originally Posted by *jl123* 
_How bout the lm6171. What are some thoughts on it?_

 

As some at least know, I'm a fan of the 6171/6172. At least one of my PPASes will use these.


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## jl123

I'm glad you're a fan. What does that mean to me?


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## Filburt

Quote:


  Originally Posted by *jl123* 
_I'm glad you're a fan. What does that mean to me?_

 

Well, I haven't gotten a chance to test this thing with a bipolar input chip yet, let alone the LM6171/72, so I don't know how well it'll work in the PPAS. I'll try it out when I get a chance. I kind of wish this board had been developed with a buffer other than the BUF634 in mind, but oh well.


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## ATAT

Sorry about the confusing sig Teerawit - The boards is in the final production layout .. What I meant by beta was doing compatibility testing between opamps and buffers.

 JL123 - no one's yet tested the LM6171 but it *should* be unity gain stable and therefore have no problems with stability.. as for sound, I have no clue on this circuit..


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## JCD

Just got my PCB's.. I had dropped out for a while and hadn't realized the beta testing was done!

 Anyway, thought I'd short cut this and see if the BoM on ATAT's website is finalized. I remember there were a few opamps that were going to be tried, but since I dropped out, I didn't see how that experiment turned out.

 Thanks for the boards!

 JCD


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## ATAT

yeah Daniel's known for being fast 
	

	
	
		
		

		
		
	


	



 JCD - the build thread outlines all the configs currently tested... sorry about the lack of testing the LM6321 
	

	
	
		
		

		
		
	


	




 I had to go to japan and work and all that.


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## vixr

Got my boards today... thanks for all the effort to make this happen... PPA in my pocket? As a matter of fact, IT IS!!!!!!!!


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## wobberly1

What happened to the PPAS, its seemed to have fallen into a black hole.

 Has anyone built one yet? 

 Are there any problems with it?

 How good does it sound?

 curious 
 Martin


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## quicksilver96

There was a problem getting IC buffers, TI BUF634 SOIC, for this amp a time back. I still don't have the money to do up a little diamond buffer prototype for this rig yet (seeing as there is a Ducati in my budget...) and IMO the national semi buffers discussed in this thread use slightly more current than I desire in a portable amplifier. I prefer the sound of the National chips over the more mellow BB sound but I'd much like this amp to pull ~30 mA (less being better). However, I just got a notice from mouser on friday that the buffers (TI BUF634 SOIC) that I backordered in june had finally shipped. Oddly enough, I was just about to check this thread out one more time before I ordered the rest of the amp components from mouser today.

 I think you will be seeing more reports on this amp as the buf634 chip becomes more readily available.


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## kklee

Quote:


  Originally Posted by *wobberly1* 
_What happened to the PPAS, its seemed to have fallen into a black hole.

 Has anyone built one yet? 

 Are there any problems with it?

 How good does it sound?

 curious 
 Martin_

 

I built two. One paired with an Alien DAC for a friend and another as a straight amp for myself.

 The only issue was operator error installing one buffer upside down.

 Since I couldn't find any Buf634's at the time, I used LMH6321 instead and they bouth sound great.


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## wobberly1

Quote:


  Originally Posted by *quicksilver96* 
_I think you will be seeing more reports on this amp as the buf634 chip becomes more readily available._

 

Great, I'll look forward to hearing more about it.

 Martin


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