# The Holy Grail



## dsavitsk

The problem, for me, with the available portable amps is that they aren't really that portable. They all need batteries, and, even worse, they all need sources which also need batteries as well as cables to connect them. I wanted something that I could take to a coffee shop, connect to my computer, and listen without a pile of crap on the table.

 That is, I wanted a usb dac with a built in headphone amp that was all powered via USB, and I wanted it to sound good. Now, Hagtech does make such a thing, but quite frankly it lacks the power to actually drive headphones, it uses a TI dac chip that does not sound that good, and it costs a fortune, all things considered.

 So, this being DIY, I made my own (and of course spent way more than I would have on a hagtech one, but oh well.) It is a NOS USB DAC using the TDA1543 as a dac and a passive I/V. The amp stage is more or less ripped off from the Pint/Mini3. However, the really clever bit is the power supply. It uses a DC-DC converter to get a higher voltage out of the USB which is then regulated to what it needs to be for the amp and the DAC. I configured mine for 9V, but the chip can supply something like 24V if need be.

 For the first experimental build I used the NJR4556 opamps, but the ad8397 is on deck for the next one. (Schematics and layout details will be on my site soon -- a couple of days probably.)


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## MASantos

I want one, I want one!!! 
	

	
	
		
		

		
		
	


	




 This is what I have spoken about some time ago, in the PCM2702 revision B DAC thread!

 It looks really nice!!!!


 it looks like it was build with the hammond 1455C801 enclosure in mind. can you confirm this? 


 THat's really nice!


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## dsavitsk

Quote:


  Originally Posted by *MASantos* 
_it looks like it was build with the hammond 1455C801 enclosure in mind. can you confirm this?_

 

Indeed. However, I went a little closer to the edges that I should have and some of the parts (C11 and C12) touch the case. So, I may need to do another revision to pull the layout in a little tighter.


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## joostoo

It may not fit in that case. It was talked about in another thread about how the EVJ pot could be too tall to fit in it.


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## MASantos

This is funny! I was driving home today and was thinking about startting a new thread to convince someone to design exactly this! A usb dac with an amp powered form the usb. Strange coincidence. I'm in for a group buy if you decide to do one. 

 What's the estimate parts cost? Around 100$ including case and shipping costs?


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## dsavitsk

Quote:


  Originally Posted by *joostoo* 
_It may not fit in that case. It was talked about in another thread about how the EVJ pot could be too tall to fit in it._

 

I think that was my thread. It will fit, but you have to apply a little force. Also, the smoothing cap I used is a little tall, so I need to hunt around for a shortr one.


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## Predator88

Hmm, this could be extremely useful once I get a laptop. How much did this cost to build? Outstanding work. Another version of this that would be really sweet would be one that could bypass the amp so it could double as a regular desktop amp to be paired with something more powerful. Yet still be abel to use the built in when portability is a must.


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## K2Grey

nevermind.


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## hanon

Super conception and execution. I've been looking around for a long time for such a project for use with a notebook. My current proxy solution is rather primitive - use tbaam or esi u24 with an attenuator. Neither is very elegant nor very satisfying, so consider great interest expressed should a pcb or kit fs emerge.


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## mrarroyo

I want one too. Can you keep me in mind if there is a group buy? Hopefully I can buy one put together.


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## ATAT

a). what passive I/V network are you using?

 b). what dc-dc converter are you running? and whats your current draw? 
 Im just shooting from the hip right now, but the usb runs at 0->5v, you have to up that to at least 9 volts for a useable pint config right? so you have some serious current draw if I'm not mistaken...

 Looks like a great project =). good luck on that


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## dsavitsk

Quote:


  Originally Posted by *ATAT* 
_a). what passive I/V network are you using?_

 

I used 1K for both I/V and for Vref. It is not necessarilly the optimum setup, but it actually does pretty well. It also keeps the output impedence of the DAC stage low enough that it works well into the 10K pot -- used because of the opamps used.

  Quote:


  Originally Posted by *ATAT* 
_b). what dc-dc converter are you running? and whats your current draw? 
 Im just shooting from the hip right now, but the usb runs at 0->5v, you have to up that to at least 9 volts for a useable pint config right? so you have some serious current draw if I'm not mistaken..._

 

For the DC-DC converter I used a TPS61040. It is pretty efficient and current draw is not that bad. I converted the power to 9V which is reregulated to 8V by a LDO vreg for the amp and 5V for the DAC. The pcm2707 runs at 3.3V and for that there is a reg101 connected right to the usb supply.

 I ran it off my laptop today which was on battery power and it ran comfprtably for about 5 hours that way. However, you are correct that this is the limiting factor. Oh well, it is almost the holy grail. Maybe it needs some solar power chips


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## Fiola

Im in for a group buy if anyone decides to do one! 
	

	
	
		
		

		
		
	


	



 looks awsome btw, great work!


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## MASantos

What would be the maximum voltage that could easily be pulled? WOuld there be any benefit it extracting something like 13v to have 12v after the reg? That could help the amp section a bit. The pint doesn't pull that much current anyway. 

 I am actually listening to a PINT 9volts only and it sound amazing liekt this!

  Quote:


  Originally Posted by *dsavitsk* 
_I used 1K for both I/V and for Vref. It is not necessarilly the optimum setup, but it actually does pretty well. It also keeps the output impedence of the DAC stage low enough that it works well into the 10K pot -- used because of the opamps used.



 For the DC-DC converter I used a TPS61040. It is pretty efficient and current draw is not that bad. I converted the power to 9V which is reregulated to 8V by a LDO vreg for the amp and 5V for the DAC. The pcm2707 runs at 3.3V and for that there is a reg101 connected right to the usb supply.

 I ran it off my laptop today which was on battery power and it ran comfprtably for about 5 hours that way. However, you are correct that this is the limiting factor. Oh well, it is almost the holy grail. Maybe it needs some solar power chips 
	

	
	
		
		

		
		
	


	


_


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## ATAT

dsavidsk very nice..

 why not use a opamp i/v stage? it would be alot better (imho) and you could just waste one SOIC space.. 

 by the way, any reason why you use the switcher for your 5v supply? you could just filter / tap that off straight USB and not strain your dc-dc converter..

 My laptop doesnt run 5 hours stock 
	

	
	
		
		

		
		
	


	




 so that's that. 

 also.. one sided?


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## dsavitsk

Quote:


  Originally Posted by *ATAT* 
_why not use a opamp i/v stage?_

 

Cause I don't like them, and as the designer that's my prerogative. 
	

	
	
		
		

		
			





 Plus it would require getting more power over to that side of the board, but really the first reason is the real one.

  Quote:


  Originally Posted by *ATAT* 
_by the way, any reason why you use the switcher for your 5v supply? you could just filter / tap that off straight USB and not strain your dc-dc converter.._

 

The tda1543 sounds better -- or at least different -- with 8V. I was just running it conservatively at 5, but by giving the option of the higher voltage it gives the end user more choice.


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## joostoo

Humm....i should consider a usb DAC for my next project maybe...

 Just a few questions though about any DAC:

 1)suppose i had an ipod shuffle, could i theoretically plug it into the usb port?

 2)does the computer need any special drivers for it to work with the DAC?


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## dhp

why not the RK097? It's shorter than the EVJ I believe


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## Clutz

I won't be able to build my copy of the PCB until I get back from New York - but I'm planning on building the first one with either a pair of OPA227s or OPA2132/4s, and the second with a pair of AD8397s. I'm really looking forward to it.


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## Clutz

Quote:


  Originally Posted by *joostoo* 
_1)suppose i had an ipod shuffle, could i theoretically plug it into the usb port?_

 

No. First of all, when you are playing music over an iPod, to the best of my knowledge, it is not outputting the digital signal to the D+ and D- of the USB interface, which you would need. Second, and more importantly - it would draw *way* too much current to use with an iPod shuffle. 

  Quote:


 2)does the computer need any special drivers for it to work with the DAC? 
 

The short answer is, no. The longer answer is: As long as you're using any operating system that supports Streaming USB Audio, then no. Windows 98, 2000, ME, XP, Mac OS X, various Linux variants.


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## ATAT

dsavidsk any reason you dont like opamp i/vs? they seem like a simple and elegant solution to me.. (PM me if you dont want to talk about this in the thread)

 heh Clutz, you *could* if you cracked open the ipod and took the inputs to the dac and ran them to the input of the TDA


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## DaKi][er

Quote:


  Originally Posted by *ATAT* 
_heh Clutz, you *could* if you cracked open the ipod and took the inputs to the dac and ran them to the input of the TDA 
	

	
	
		
		

		
		
	


	


_

 

No you couldn't 
	

	
	
		
		

		
		
	


	




 have a look up of the datasheets of the dacs used in the ipods to see why


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## ATAT

I was kidding Daki][er .. nevertheless, pin 6 and 7? data and clock is right there for anyone to take and send to the dac chip.


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## .: ZMN :.

Great Idea!

 Just out of curiosity. Is there a good reason against sharing the PS of your Notebook with an AMP/DAC (besides possible source of noise)?

 Without any EE background I would think that a couple of diodes would be enough to get this DUAL PS option working, right?. 
	

	
	
		
		

		
		
	


	




 Ans yes, I would love to see a good small amp/dac combi that can run with a USB-powered sollution AND can go 'overdrive' with the Noteook PS in case the coffee place has an available powerconnection


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## Clutz

Quote:


  Originally Posted by *ATAT* 
_dsavidsk any reason you dont like opamp i/vs? they seem like a simple and elegant solution to me.. (PM me if you dont want to talk about this in the thread)_

 

You can't get much simpler than using a set of resistors.

  Quote:


 heh Clutz, you *could* if you cracked open the ipod and took the inputs to the dac and ran them to the input of the TDA 
 

You'd still have the problem of draining the battery of the iPod really quickly.


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## motherone

Quote:


  Originally Posted by *.: ZMN :.* 
_Great Idea!

 Just out of curiosity. Is there a good reason against sharing the PS of your Notebook with an AMP/DAC (besides possible source of noise)?

 Without any EE background I would think that a couple of diodes would be enough to get this DUAL PS option working, right?. 
	

	
	
		
		

		
		
	


	




 Ans yes, I would love to see a good small amp/dac combi that can run with a USB-powered sollution AND can go 'overdrive' with the Noteook PS in case the coffee place has an available powerconnection 
	

	
	
		
		

		
		
	


	


_

 

I would say the primary reasons to avoid sharing the supply of your PC/Laptop are the fact that you only get 5V @ 250-500ma out of the USB Port, and that power is sourced from a noisy switching power supply. 

 To get a dual supply, you would need another DC-to-DC converter to generate it.

 This isn't anything against SMPS, as I know they can sound very good when properly implemented. However, PC Power Supplies are all about getting the maximum amount of power as cheaply as possible. They generally rely on local regulators to filter out the remaining crud from the PSU.


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## dsavitsk

Quote:


  Originally Posted by *motherone* 
_I would say the primary reasons to avoid sharing the supply of your PC/Laptop are the fact that you only get 5V @ 250-500ma out of the USB Port, and that power is sourced from a noisy switching power supply. 

 To get a dual supply, you would need another DC-to-DC converter to generate it.

 This isn't anything against SMPS, as I know they can sound very good when properly implemented. However, PC Power Supplies are all about getting the maximum amount of power as cheaply as possible. They generally rely on local regulators to filter out the remaining crud from the PSU._

 

My laptop, an IBM/Lenovo T60, uses a linear power supply. I chatted with a guy at IBM who said he believed there were some EU regulations that were pushing laptop makers to use linear PS's. Whether that part is true or not I do not know.

 At any rate, I am using the computer's batteries, so the PS is not a big issue (though I suppose there are dc-dc converters in the laptop itself.) Also, the dac/amp has ferrites and such all over to clean up hf noise.


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## Dave_M

Quote:


  Originally Posted by *joostoo* 
_suppose i had an ipod shuffle, could i theoretically plug it into the usb port?_

 

On top of what Clutz said, there is another reason. USB is flawed in that it is a master / slave relationship. The ipod will be a slave, the DAC would also be a slave. Slaves cannot talk to each other. You need a master device like a computer. Firewire doesn't have this problem - AFAIK.


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## Calroth

Quote:


  Originally Posted by *joostoo* 
_1)suppose i had an ipod shuffle, could i theoretically plug it into the usb port?_

 

The iPod shuffle is unique in that as well as the standard 4 pins on its USB port, it has an additional 5 pins. These carry line-level signals, I believe.

 So, the answer is yes, on the following conditions: a) it's an iPod shuffle, not anything else; b) you modify the USB port and/or cable on your side to handle the additional 5 pins; c) you understand that the signal out is analogue, so you don't actually need that DAC...


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## Clutz

Quote:


  Originally Posted by *Calroth* 
_The iPod shuffle is unique in that as well as the standard 4 pins on its USB port, it has an additional 5 pins. These carry line-level signals, I believe.

 So, the answer is yes, on the following conditions: a) it's an iPod shuffle, not anything else; b) you modify the USB port and/or cable on your side to handle the additional 5 pins; c) you understand that the signal out is analogue, so you don't actually need that DAC... 
	

	
	
		
		

		
		
	


	


_

 

Well, seeing as the point of this is to be a USB DAC + AMP, then no you can't because it was designed to take a digital audio signal in from a USB port, convert it using a DAC and then amplify the signal - not just amplify a line level signal.


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## Calroth

Quote:


  Originally Posted by *Clutz* 
_Well, seeing as the point of this is to be a USB DAC + AMP, then no you can't because it was designed to take a digital audio signal in from a USB port, convert it using a DAC and then amplify the signal - not just amplify a line level signal._

 

See point c) where I say that you can get rid of the DAC part. It was supposed to be a joke, since the whole point was to develop a DAC. But what the hell, I'll kill my own joke.


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## .: ZMN :.

So if I understand your (more expert) positions correctly and hopefully staying on topic:

 1. The USB-port provides enough current to meet demands, therefor other power supply options are not necessary at all. 
 (simple example: USB 5v DC-DC boosted to 16v, with ~80% efficiency, leaves MAX ~60-120mA to use for AMP and that is enough?)

 2.
  Quote:


 They generally rely on local regulators to filter out the remaining crud from the PSU. 
 

 Quote:


 Also, the dac/amp has ferrites and such all over to clean up hf noise. 
 

It would be possible to effectively filter a (laptop) PSU separately without large sacrifices in board space, but the laptop (battery) does this allready for you. So why bother, take the USB supply. Correct?

 3.
  Quote:


 To get a dual supply, you would need another DC-to-DC converter to generate it. 
 

Why? My IBM PSU provides 16V DC and the Toshiba/Asus/Dell/Acer/IBM laptop PSUs I have seen all have 16-19V DC. I would say this is pretty comfortable if you would like to boost performance a bit. Let's say, when you move from noisy cafe to quiet hotel lounge and your best headphones happen to have travelled along with you 
	

	
	
		
		

		
			





.


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## mono

Quote:


  Originally Posted by *dsavitsk* 
_My laptop, an IBM/Lenovo T60, uses a linear power supply. I chatted with a guy at IBM who said he believed there were some EU regulations that were pushing laptop makers to use linear PS's. Whether that part is true or not I do not know.

 At any rate, I am using the computer's batteries, so the PS is not a big issue (though I suppose there are dc-dc converters in the laptop itself.) Also, the dac/amp has ferrites and such all over to clean up hf noise._

 


 I doubt this, it is not at all likely that it uses a linear supply for anything, anywhere, except maybe for the mainboard audio. Perhaps he didn't know the difference between linear and "regulated"?

 The laptop AC-DC brick is 1/2 of the supply. The second half is a power board (or mainboard integrated) switcher that produces that 5V for USB. It's likely there isn't much power noise difference on the USB port whether running from battery or the AC brick- that they're both relatively noisey and will need those ferrites if not more elaborate LC filter. Also keep in mind the limitations of capacitance on a USB port- there isn't supposed to be over roughly 100uF in a USB device unless behind a current limiter. I don't recall the max allowed inrush current, it might be in the USB specification.


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## Clutz

Quote:


  Originally Posted by *Calroth* 
_See point c) where I say that you can get rid of the DAC part. It was supposed to be a joke, since the whole point was to develop a DAC. But what the hell, I'll kill my own joke._

 

Oops -Sorry.


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## dsavitsk

Quote:


  Originally Posted by *mono* 
_The laptop AC-DC brick is 1/2 of the supply._

 

Your point is well taken. I was just referring to the power brick which is linear.

  Quote:


 Also keep in mind the limitations of capacitance on a USB port- there isn't supposed to be over roughly 100uF in a USB device unless behind a current limiter. I don't recall the max allowed inrush current, it might be in the USB specification. 
 

That is interesting and you appear to be correct. The upside is that the majority of the capacitance is behind the voltage regulators which are all current limiting. I don't know if this is enough to meet USB specs, though. Also, one of the regs that I used will allow 500mA, so I may want to choose a different regulator for that spot that has a stricter limit.

 Oh, also, the DC-DC converter is current limited to 400mA and has a soft start feature, so I think everything is okay.


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## dsavitsk

A couple of things: If anyone is interested I have a small number (4) of extra prototypes that you can have for cheap. I am curious to get some feedback on what people think, how difficult they are to build (the answer to that is very, by the way), etc. before I implement a few changes.

 I am particularly interested in someone with a scope that can take some readings, etc. So, let's say $12 for a board and a tda1543 (and I'll cover paypal and shipping). The first 2 people get some Nichicon Muse ES coupling caps too -- I only have 6 left and you need 3. Also, you have to promise to build it sooner than later as otherwise it does me no good. Oh, total cost for the whole thing can range, but probably $60 on the low end and $100 on the high (with BG caps and expensive opamps.) Send me a PM -- but don't post to the thread that you did so.

 Also, do note the concern mono has raised above re: excess capacitance and in rush current. It has not been a problem for me, (and see my note in the post above) but I can't be responsible for you.

 Last, the management has asked that comments and requests regarding a "Group Buy" be curtailed from this thread.

 Thanks.

 -d


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## Thaddy

**subscribed**

 I'm keeping my eye on this thread, excellent work so far
	

	
	
		
		

		
		
	


	




 This is the perfect amp for use at the office IMO.


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## TheRobbStory

I'd definitely like to get in on this.


 I emailed you earlier today about one of your other DAC designs. This is essentially what I was looking to do with it. Perfect solution for school and office!


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## dsavitsk

One more board if anyone wants it.

 -d


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## Samgotit

Edit.


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## MASantos

Could you post a schematic and if possibly a parts list? I went to your website but I couldn't anything about this project.


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## dsavitsk

Quote:


  Originally Posted by *MASantos* 
_Could you post a schematic and if possibly a parts list? I went to your website but I couldn't anything about this project._

 

Next board revision is about done. Info should be up in a week or two ...


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## Samgotit

Quote:


  Originally Posted by *dsavitsk* 
_Next board revision is about done. Info should be up in a week or two ..._

 

The first revision was a huge surprise considering its size and power supply. I found Bass and "Weight" I have never heard before out of the K701. This includes through all of the non-portable gear I own! There were moments when the bass was... "concentric rings in the water cup"... spectacular. Understand, I'm not a huge bass head, but the new sound was very addictive.

 TDA1543 + Pint amplification + NJR4556 = 
	

	
	
		
		

		
		
	


	




 Looking forward to the second revision.

 Sam


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## dsavitsk




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## ozshadow

Purdy !


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## Samgotit

Quote:


  Originally Posted by *ozshadow* 
_Purdy !_

 

and available!

 Looks like Dsavitsk is finished with Rev0.1b:
http://www.ecp.cc/HPDAC.html


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## abcheng

nvm


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## dsavitsk

There was some concern at some point (though I can't find the post for the life of me) that too much capacitance on the usb supply was trouble as the in rush current would be too high. Well, in the course of some experiments I had the opportunity to learn a little more about this. I accidentally shorted the usb supply to ground. Windows (XP in this case on T60 Thinkpad) threw an error, internally disconnected the supply, and suggested I remove the device. No harm came to the computer. So, at least in some cases, there is a safety mechanism built in.


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## MASantos

I was measuring the voltage output of my laptop some time ago. I accidentaly shorted the output and that error also appeared on the screen. It said that the output capability of the USB port had been reached and it would be shut down. I then had to go the USB controller menu and turn the port on. I then tested this in my father's laptop and home computers and the same happened. It is probably a standard feature of the USB connections.

 Where could we read more about this?


  Quote:


  Originally Posted by *dsavitsk* 
_There was some concern at some point (though I can't find the post for the life of me) that too much capacitance on the usb supply was trouble as the in rush current would be too high. Well, in the course of some experiments I had the opportunity to learn a little more about this. I accidentally shorted the usb supply to ground. Windows (XP in this case on T60 Thinkpad) threw an error, internally disconnected the supply, and suggested I remove the device. No harm came to the computer. So, at least in some cases, there is a safety mechanism built in._


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## Clutz

Do an online search for the IEEE white paper on the USB protocol/standard is my guess. That said, here are some words of caution. 

 Manufacturers, particularly the cheaper manufacturers, do not always follow hardware standards to the letter of the law. I think it would be unwise to make the assumption that all USB ports have this shutdown properly implemented. It could cost the individual making the assumption the cost of a new motherboard, DAC, or both. If it's there and it works - great; but when you have a design, design it to be a safe-fail, rather than assuming that the failsafes will work.


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## dsavitsk

Quote:


  Originally Posted by *Clutz* 
_Do an online search for the IEEE white paper on the USB protocol/standard is my guess. That said, here are some words of caution. 

 Manufacturers, particularly the cheaper manufacturers, do not always follow hardware standards to the letter of the law. I think it would be unwise to make the assumption that all USB ports have this shutdown properly implemented. It could cost the individual making the assumption the cost of a new motherboard, DAC, or both. If it's there and it works - great; but when you have a design, design it to be a safe-fail, rather than assuming that the failsafes will work._

 

The thing to take from my post was several fold, to wit, 1. in a worst case scenario, you *may* have some protection and 2. more importantly, it took a dead short to see this message. It has not been seen with the normal design which has worked fine and, as noted in the project page, there is considerable attention paid to limiting inrush current.

 That said, it is a good idea to read the USB specs, to do initial tests on an old computer that you don't care about, etc.


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## NeilR

When I plug in my Alien Dac, I get a balloon message off of the system tray complaining about a power surge on the USB port. This message appears for maybe a second or two and disappears. I don't lose power or functionality on the port as reported above.

 I'm using a Dell I8500 laptop running Windows XP 2002 SP2, fully up to date with automatic updates. I've been trying to decide if I need to deal with this and cut my cap values down.


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## Scimmia

I got that message on my laptop when I screwed up a project I was doing. I though maybe the laptop just couldn't supply the power I needed (should have known better, but the USB ports on my laptop are screwed up anyway). So of course, I plug it into my desktop, and all of my wires start to burn!

 Lesson: not all USB ports have protection, or have enough protection to protect small wires.


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## mono

Quote:


  Originally Posted by *dsavitsk* 
_The thing to take from my post was several fold, to wit, 1. in a worst case scenario, you *may* have some protection and 2. more importantly, it took a dead short to see this message. It has not been seen with the normal design which has worked fine and, as noted in the project page, there is considerable attention paid to limiting inrush current.

 That said, it is a good idea to read the USB specs, to do initial tests on an old computer that you don't care about, etc._

 

While you might have protection in worst case, it would be better to assume you don't, as some boards may have a zero ohm resistor or jumper instead of a polyfuse and some Intel mainboards were even blowing out southbridge silicon from overcurrent. 

 Actually your situation is a bit odd as a short _should've_ triggered overcurrent protection from the PSU, requiring disconnect (from upstream power, AC or in case of notebook, DC) to reset the PSU. Then there's the issue that one fault may be survivable but perpetual high current surges could take their toll eventually. While it's hopefully safe to assume there won't be perpetual shorting of power & ground, it may not be as safe to assume all host devices are as robust as the next. 

 The USB 2.0 Spec reads as follows;
  Quote:


 7.2.4.1 Inrush Current Limiting

 When a function or hub is plugged into the network, it has a certain amount of on-board capacitance between
 VBUS and ground. In addition, the regulator on the device may supply current to its output bypass capacitance
 and to the function as soon as power is applied. Consequently, if no measures are taken to prevent it, there could
 be a surge of current into the device which might pull the VBUS on the hub below its minimum operating level.
 Inrush currents can also occur when a high-power function is switched into its high-power mode. This problem
 must be solved by limiting the inrush current and by providing sufficient capacitance in each hub to prevent the
 power supplied to the other ports from going out of tolerance. An additional motivation for limiting inrush
 current is to minimize contact arcing, thereby prolonging connector contact life.

 The maximum droop in the hub VBUS is 330 mV, or about 10% of the nominal signal swing from the function.
 In order to meet this requirement, the following conditions must be met:


> • The maximum load (CRPB) that can be placed at the downstream end of a cable is 10 µF in parallel with
> 44 Ω. The 10 µF capacitance represents any bypass capacitor directly connected across the VBUS lines in
> the function plus any capacitive effects visible through the regulator in the device. The 44 Ω resistance
> represents one unit load of current drawn by the device during connect.
> ...


The upstream facing port of a hub is also required to meet the above requirements. Furthermore, a bus-powered
 hub must provide additional surge limiting in the form of a soft-start circuit when it enables power to its
 downstream facing ports.

 A high-power bus-powered device that is switching from a lower power configuration to a higher power
 configuration must not cause droop > 330 mV on the VBUS at its upstream hub. The device can meet this by
 ensuring that changes in the capacitive load it presents do not exceed 10 µF.

 Signal pins are protected from excessive currents during dynamic attach by being recessed in the connector such
 that the power pins make contact first. This guarantees that the power rails to the downstream device are
 referenced before the signal pins make contact. In addition, the signal lines are in a high-impedance state during connect, so that no current flows for standard signal levels.


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## mikemacwillie

Got my partial kit today.. I'm very excited to start building! The quality of the PCB is ecelent, and the parts where well packed. Just waiting on my digikey order!


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## mikemacwillie

I've got mine built.. However it doesn't seem to be working properly yet.. I get sound, but it's very distorted. Troubleshooting time for me!


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## mikemacwillie

Got it working.. A mistake on my part was the problem.


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## MisterX

Initial listening test suggest this is a very good performer for such a small package. 
	

	
	
		
		

		
		
	


	




 Edit: pics removed.


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## Voodoochile

Nice, as always, Marshall! Do you have a back panel pic available?

 I'm curious- did you drill a hole, then file out the corners, or just cut a rectangle outright? (for the USB-B connector)


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## tomb

Yes, very nice work, MisterX! (I don't see anything crooked. 
	

	
	
		
		

		
		
	


	




 )

 Would you give us some listening comments? Dsavitsk loves bass and Samgotit likes it with his K701's, but how does it sound compared to some of the other DIY amps and/or the Alien DAC?


----------



## MisterX

Quote:


  Originally Posted by *Voodoochile* 
_Nice, as always, Marshall! Do you have a back panel pic available?_

 

Here ya go: 



 I am once again guilty of not cleaning something before taking pictures. 
	

	
	
		
		

		
			






 As you can tell the USB receptacle that is included with the boards rocks!


  Quote:


  Originally Posted by *Voodoochile* 
_I'm curious- did you drill a hole, then file out the corners, or just cut a rectangle outright? (for the USB-B connector)_

 

I did this one a little different. 
 I started by drilling 4 1/8" holes in the corners then drilled 4 more holes between them, cut the metal between the holes with my nippy cutters, used a rotary file on the dremel to get the shape close and then finished it with a file. 
 Needless to say that process takes a wile. 
	

	
	
		
		

		
		
	


	



 One of these days I am gonna stop at the local tool shop and have them make me a knockout punch. 


  Quote:


 how does it sound compared to some of the other DIY amps and/or the Alien DAC? 
 

I havent had a chance to do any side by side comparisons yet but I would say it sounds better then the Alien DAC + Pint combo with the same op-amps (LM6172s).


----------



## Voodoochile

There is no acceptable substitute for old-fashioned patience. Looks great!


----------



## MisterX

I have been eye-balling a solution for those days when I am not so patient. 
 Have a look: 

http://www.deepgroove1.com/cnc%20mill.htm


----------



## MisterX

I finally had a chance to do some side by side comparisons between the HPDAC and a few PINT + Alien DAC combos. 
 The PINTs had slightly better bass so a quick change was in order:


----------



## tomb




----------



## humanflyz

Pardon my ignorance, since I'm not a DIY type of guy, but what would a maxed-out HPDAC look like configuration-wise?


----------



## MASantos

Quote:


  Originally Posted by *MisterX* 
_I finally had a chance to do some side by side comparisons between the HPDAC and a few PINT + Alien DAC combos. 
 The PINTs had slightly better bass so a quick change was in order: 




_

 


 MisterX, you're the greatest!!!!!!


----------



## civilmonkey

I'm just about to place an order to build my HPDAC, but Digikey is out of PCM2707's. I compared the datasheets between PCM2707 PCM2706 and couldn't find many differences. Has anyone successfully used a PCM2706?


----------



## dsavitsk

I don't see any reason it should be a problem, but I have not tested it yet. I am waiting for a few parts and I will test it in a few days.


----------



## Clutz

Quote:


  Originally Posted by *civilmonkey* 
_I'm just about to place an order to build my HPDAC, but Digikey is out of PCM2707's. I compared the datasheets between PCM2707 PCM2706 and couldn't find many differences. Has anyone successfully used a PCM2706?_

 

I haven't used it in this application, but I have used the 2706 instead of a 2707 in another situation and it worked just fine.


----------



## FallenAngel

Quote:


  Originally Posted by *MisterX* 
_I finally had a chance to do some side by side comparisons between the HPDAC and a few PINT + Alien DAC combos. 
 The PINTs had slightly better bass so a quick change was in order: 




_

 

I must ask, what is the little cap in C2 beside the big Black Gate?


----------



## MisterX

.1uF N series


----------



## FallenAngel

Well, I've decided to build a couple of these, then noticed there's no real BOM so it's on to finding and choosing parts. Anybody want to help out with a BOM?


----------



## FallenAngel

Well, I created a BOM for this HPDAC completly from DigiKey.

 Could someone please verify that I'm using the correct parts as I'm a little clueless whether the caps I chose will work or if there are better choices for them. Please note the "Notes" section for things I'm not clear on. BOM is zipped in Message #77 below.

 Thanks!


----------



## dsavitsk

Quote:


  Originally Posted by *FallenAngel* 
_Well, I created a BOM for this HPDAC completly from DigiKey.

 Could someone please verify that I'm using the correct parts as I'm a little clueless whether the caps I chose will work or if there are better choices for them. The BOM can be found here in Excel format. Please note the "Notes" section for things I'm not clear on.

 Thanks!_

 

If you put a text file up I'll look at it, but I'm allergic to Excel 
	

	
	
		
		

		
		
	


	




 Note, though, that there is no BOM because there is no set way to build this. There is a lot of room for experimentation and tinkering.


----------



## MisterX

Quote:


 Sorry about the free file sharing server, don't have a web host handy. You gotta click on "Download for free with FileFactory Basic" mid page, then on "Click here to begin your download". 
 

Screw all of that... just zip the file and attach it to a messge. 

 Like this:


----------



## FallenAngel

Updated 
	

	
	
		
		

		
			




 Still gotta choose parts for the main C2 caps. I like MisterX's idea, might just go with that, but DigiKey doesn't carry BG's. Any ideas on what I can get from DigiKey that suits that position well?

 Oh man, thanks MisterX, didn't even see that, I must be blind.


----------



## dsavitsk

Quote:


  Originally Posted by *FallenAngel* 
_Updated 
	

	
	
		
		

		
		
	


	



 Still gotta choose parts for the main C2 caps. I like MisterX's idea, might just go with that, but DigiKey doesn't carry BG's._

 

I would say that 4x 47uF/25V Silmic II (604-1054-ND) is a good choice. Also, there are a bunch of Panasonic FMs that will fit the 8mm spot if you want a bit more capacitance (though I would consider 470uF to be the limit here) -- check the datasheet for sizes. You could also use FC's, but I don't like them as much as FMs.


----------



## FallenAngel

The 4 x 47uF Elna only add up to 188uF total capacitance, I think I would want to try for a bit more capacitance. I'm thinking of a single 470uF cap in the same Elna line and maybe another small 4.7uF one after it, any ideas?

 Or what about using 4 x 100uF Elna, same line, they're 10mm instead of 8mm but it really shouldn't be too hard to bend one lead on each cap by 2mm and still have them stand straight and with a height of 16mm, it should still fit inside the 1455C802.


----------



## dsavitsk

Quote:


  Originally Posted by *dsavitsk* 
_I don't see any reason it should be a problem, but I have not tested it yet. I am waiting for a few parts and I will test it in a few days._

 

For those who are worried, the 2706 seems to work just fine.


----------



## daveDerek

Quote:


  Originally Posted by *dsavitsk* 
_The problem, for me, with the available portable amps is that they aren't really that portable. They all need batteries, and, even worse, they all need sources which also need batteries as well as cables to connect them. I wanted something that I could take to a coffee shop, connect to my computer, and listen without a pile of crap on the table.

 That is, I wanted a usb dac with a built in headphone amp that was all powered via USB, and I wanted it to sound good._

 

not meant as a thread crap, but i think the headroom total bithead would meet the stated requirements. of course if building stuff is how you get your jollies, then that would be worthless....


----------



## MASantos

Quote:


  Originally Posted by *daveDerek* 
_not meant as a thread crap, but i think the headroom total bithead would meet the stated requirements. of course if building stuff is how you get your jollies, then that would be worthless...._

 

You point is correct, but this one can be made cheaper, you build it to your likings and specifications, smaller, no batteries to charge, so it is very different from the bithead. Sound should be on the same level if not better.


----------



## dsavitsk

Quote:


  Originally Posted by *daveDerek* 
_not meant as a thread crap, but i think the headroom total bithead would meet the stated requirements._

 

I thought it needed batteries, but I guess not, so, I'll add the requirements that it needs to have a metal case and a decent volume pot.


----------



## MisterX

I dunno if I would ever call a EVJ a decent pot.


----------



## mrarroyo

Is there anyone making this for those of us not diyer's? Thanks.


----------



## MASantos

Quote:


  Originally Posted by *mrarroyo* 
_Is there anyone making this for those of us not diyer's? Thanks._

 

I believe that dsavitsk offers these fully assembled. Check his homepage for details.


----------



## tomb

Quote:


  Originally Posted by *MisterX* 
_I dunno if I would ever call a EVJ a decent pot. 
	

	
	
		
		

		
		
	


	


_

 

Aw, come on:
 1. include the pins in the PCB
 2. include holes in the PCB for soldering the tabs
 3. make sure it's bolted directly to a metal endplate
 4. don't let any flux drip inside
 5. don't screw down too tightly with a knob's set screw on the plastic shaft
 6. pay no attention if it leaks volume at the lowest settings

 With all those things, it can be semi-decent.


----------



## Samgotit

Quote:


  Originally Posted by *daveDerek* 
_not meant as a thread crap, but i think the headroom total bithead would meet the stated requirements..._

 

I'm an idiot. Ignore me reguarding my first post. I was under the impression it was full time battery powered.

 Do note the Bithead is a totally different animal - No TDA1543 (among many other things). The Bithead implements the PCM2902 for input and output IRC.
 Comparing the two would be very very interesting. Anyone want to loan me their Bithead?


----------



## FallenAngel

Quote:


  Originally Posted by *tomb* 
_3. make sure it's bolted directly to a metal endplate_

 

Uhm... does it really NEED to be connected to a metal endplate?


----------



## dsavitsk

Quote:


  Originally Posted by *FallenAngel* 
_Uhm... does it really NEED to be connected to a metal endplate?_

 

I've not had any noise from it not being connected.

 The EVJ pots are not the best in mechanical terms, but compared to other pots in the price range they sound pretty good (and they are easy to get) which seems more important to me.


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* 
_I've not had any noise from it not being connected.

 The EVJ pots are not the best in mechanical terms, but compared to other pots in the price range they sound pretty good (and they are easy to get) which seems more important to me._

 

OK, if you guys are going to take that list so seriously, I'll bite:

 No, it doesn't have to be metal. Plastic is fine as long as it's thick enough. The Pana EVJ needs all these three - 1) leads in the PCB, 2) solder positions for the wing tabs, and 3) locked completely in place with a _solid_ endplate.

 Seriously, I agree with dsavitsk in his essential thought: under the right conditions, they perform well, are cheap and _easy to get_. I wish more board designers would at least make the option for them. If the PCB doesn't have all that mentioned above, the EVJ has some serious issues.

 P.S. It's a very nice project, dsavitsk.


----------



## MisterX

Quote:


 It's a very nice project, dsavitsk. 
 

You will get no argument from me there.


----------



## motherone

Weird.. I've never had any issues with my EVJ's.. I've used them in at least 20 projects with no issues whatsoever.


----------



## mrarroyo

Quote:


  Originally Posted by *MASantos* 
_I believe that dsavitsk offers these fully assembled. Check his homepage for details._

 

Thanks.


----------



## joostoo

Quote:


  Originally Posted by *dsavitsk* 
_I've not had any noise from it not being connected.

 The EVJ pots are not the best in mechanical terms, but compared to other pots in the price range they sound pretty good (and they are easy to get) which seems more important to me._

 

Agreed, thats the only reason ive continued to use them. They are probably the only good audio pots i can find in digikeys online catalogue. You cant beat having 10 EVJ's coming to your door the VERY NEXT DAY, for just under 25 bux. Once digikey brings in a different audio pot (hopefully in the alps fashion, 2 rows of 3 pins each), ill be dropping the EVJ's faster than a hot potato.


----------



## FallenAngel

Well, I just got my parts in last night (came home at midnight).

 To cut a long story short, 6am and half a bottle of my favourite wine later (Domaine Gigondan 2000 Cuvee), I have 2 built HPDACs. One is getting serious distortion (actually worse at lower volumes) and the other isn't even recognized as a USB device. I'll investigate the non-detected one later as it seems I probably just missed something, but first I'm just curious, what could be causing the distortion in the one that "works". Any ideas?

 Thanks


----------



## MisterX

Did you check the voltages yet?


----------



## dsavitsk

Quote:


  Originally Posted by *FallenAngel* 
_what could be causing the distortion in the one that "works". Any ideas?_

 

Nope, but post pics and it might be possible to figure it out.


----------



## Clutz

Also, in case it isn't obvious from the picture - what opamps are you using, and what gain in the amp portion are you using? Can you connect the output of the DAC's I/V stage, but before the amp stage to another amp that you know works, using aligator clips - possibly allowing you to isolate where the problem exists (e.g. digital or analog). 

 Also post pics of the device that isn't recognized as a USB device. I've had that happen a few times and in all cases it was from a really tiny solder bridge.

 Cheers,
 Cltuz


----------



## FallenAngel

Sorry, couldn't find my camera, should turn up tomorrow so pics will be uploaded then.

 MisterX: What voltages am I checking?

 DC offset on the amp is reasonable, but a little high at times while playing music. 60Ohm load, no music, < 10mA, with music playing, it jumps around 10mA to 20mA, sometimes spiking as high as 35mA, which is a little higher than I wanted.

 I didn't know exactly what voltages to check, so I just checked around VR1 and VR3 
	

	
	
		
		

		
		
	


	




 :

 VR1 IN and OUT to middle pin (Ground): 4.51V and 4.48V (Kinda weird, thought it should be closer to 8V as per schematic)

 VR3 all pins to middle (Ground): All around 3.3V

 Clutz: I'm using stock resistor values, so I think gain should be around 6. The opamps are a pair of LM6172's.

 As for connecting output of the DAC's I/V stage to another amp, I'm totally lost. I'm a systems analyst and keep this as a hobby and seriously lack the EE knowledge to know how to do that (read: Can't tell where schematic and PCB for DAC ends and AMP begins 
	

	
	
		
		

		
		
	


	




 ). But if you tell me where to connect and to what, that I can definitly do.


----------



## dsavitsk

Quote:


  Originally Posted by *FallenAngel* 
_VR1 IN and OUT to middle pin (Ground): 4.51V and 4.48V (Kinda weird, thought it should be closer to 8V as per schematic)_

 

If you are using the default resistors for R5 and R6, you should be getting about 9.5V on the input of VR1. It sounds like something is wrong with the switching PS, either a wrong resistor somewhere, or a solder bridge, or something like that.

  Quote:


 VR3 all pins to middle (Ground): All around 3.3V 
 

This is right for the output of VR3. If you are getting 3.3V on the input too, you have a computer issue. Note, though, that if your USB supply is too low (which would be odd and would probably cause other usb devices to not work) that the dc-dc converter should still work as it only needs about 2V on the input.


  Quote:


 As for connecting output of the DAC's I/V stage to another amp, I'm totally lost. ... But if you tell me where to connect and to what, that I can definitly do. 
	

	
	
		
		

		
		
	


	



 

For reference, you would take the output from CR and CL -- from the side of each closer to the volume pot. You could take ground from either side of CG. However, don't do that until we get the voltage issue resolved.


----------



## MisterX

Do you have C23 & C24 in the right way around? 
 If C23 is the right way around but C24 is backwards that would give you the symptoms you described.


----------



## Clutz

Hey MisterX: How would that cause the weird voltage problems?


----------



## FallenAngel

MisterX: I think I have C23 and C24 on right. Perhaps C24 may be bridged under the cap because it's so small, but I don't think so.

 Took pics of the distorted HPDAC, hope this helps the pros here.


----------



## dsavitsk

Any luck yet? Nothing is jumping out at me, though the tops of the chips are not readable in all cases. At this point I'd start cleaning up extra solder, looking for bridges/cold joints, etc. Maybe start thinking about whether the dc-dc converter is inop?


----------



## FallenAngel

No luck last night, still same thing. I'll go over and check all the solder joints today. Can somebody please post high quality pics of a working HPDAC just so I can compare side by side.

 Thanks.


----------



## FallenAngel

YEEAAAHH!!!! The first HPDAC works great. MisterX, you were right! I took off and resoldered C24 (tiny little thing) and the voltage on VR1 jumped to what around 9.6V. There was still some weird noice, but after going over all the solder joints that looked a little funky (big blobs of solder on the resistors and caps), everything sounds great! Thanks for the helpful info.

 I'll be casing this tonight and getting a fresh start on the second (and in much worse shape) HPDAC tomorrow.

 I also learned here that USB2.0 is basically a MUST for this DAC. I have an old laptop with a USB 1.1 port and the thing hums when I do anything on the computer. On my good desktop though, there's no problem.


----------



## dsavitsk

Quote:


  Originally Posted by *FallenAngel* 
_YEEAAAHH!!!! The first HPDAC works great._

 

Good to hear.


----------



## Samgotit

For board #2 if you want to check on the PCM270x, after you check voltages, if your meter can measure frequency check this out: http://diyparadise.com/dackit/dackit2.html
 Scroll down to "Problem: No sound...". Dsavitsk pointed this out and it seems to be a nice way to verify that your 270x is functioning and correctly soldered.

 Nice job with the first one.

 Edit: I noticed you're not having #2 recognized by windows, so the above method really isn't much good. I think you want to start by looking at power to the 270x and its solder joints (sorry if this is stating the obvious 
	

	
	
		
		

		
		
	


	




).


----------



## MASantos

I got two boards from Dsatvisk. I will only be starting this project in November/December. Could someone tell me how much should total parts cost for this be ordering stuff from digikey? 

 It should be about 100-150$ in parts right?

 Manuel


----------



## FallenAngel

My order was $180 Canadian with parts for 3 boards (plus extras for some parts) plus cases and knobs for 2 - I like to be on the safe side and have extras in case I lose those little SMC things. I'm guess it'll be around there for 2 since most parts come in standard packages of 10.

 That's not including the BlackGates I used for C2 and CL/CR/CG.


----------



## dsavitsk

Quote:


  Originally Posted by *MASantos* 
_Could someone tell me how much should total parts cost for this be ordering stuff from digikey? l_

 

I would think lower than that. The case is about $10, the pcm is $7, and the assorted caps, resistors, opamp, etc are probably not more than $30. Overall it is a pretty cheap build.


----------



## MASantos

Quote:


  Originally Posted by *dsavitsk* 
_I would think lower than that. The case is about $10, the pcm is $7, and the assorted caps, resistors, opamp, etc are probably not more than $30. Overall it is a pretty cheap build._

 

Great, it's cheapper than I tought.

 ps: YGPM!


----------



## FallenAngel

HPDAC #2 done 
	

	
	
		
		

		
		
	


	




 If somebody wants parts for their HPDAC, I ordered enough extras to populate a another full HPDAC, except the opamps, C2 (big caps), case and PSU, for those, you're on your own. - Sold to civilmonkey.

 Just found out I don't have these, but they're cheap:
 Place: C7-C19, C26
 Part: Kemet X7R 0.1uF 50V 5% Ceramic Chip Capacitor (1206 Package)
 DigiKey: 399-1250-1-ND

 PM if interested.


----------



## MisterX

Quote:


  Originally Posted by *FallenAngel* 
_HPDAC #2 done 
	

	
	
		
		

		
		
	


	


_

 

Glad to hear that you got both of them working. 
 Any thoughts on how they sound yet? 
	

	
	
		
		

		
		
	


	




 BTW, I got a nice little box in the mail today. 
 Thanks for ordering those caps for me.


----------



## FallenAngel

It sounds great! Definitly sounds similar to a PINT with my IPod. Still doesn't match the clarity of my Home Pimeta, but it's definitly a great toy. I've moved one to the office, it's very convenient to have such a small case on the desk that does EVERYTHING! No extra power supply, no seperate DAC + AMP + power to both, it's just standalone and sounds great. I would barely even mention it sounds tons better than the onboard AC97 soundcard + Sijosae Class-AB I had before. Not saying that Class-AB is a bad amp, but this HPDAC is just the most convenient thing in the world.

 Edit: WOW, thing thing does need a little burn-in time, I was listening to it all day at work, and now, maybe 6 hours later, the sound quality just BROKE OUT! Thing thing sounds much better than the first time I tried it, must be the BG caps requiring a little time. Everything is so smooth, notes just flowing from one to the next, it's incredible. Makes me want to ditch the Audigy2ZS (ASIO) and build a DAC for home.


----------



## blargman

is it possible to make one of these with a XLR connection? :\


----------



## FallenAngel

It's not balanced, but as long as the jack fits, I don't see why not.


----------



## blargman

sry, ya i assumed it wasn't balanced. making it so would require a major redesign?


----------



## dsavitsk

Quote:


  Originally Posted by *blargman* 
_sry, ya i assumed it wasn't balanced. making it so would require a major redesign?_

 

Major enough, at least for a designer without balanced headphones. 
	

	
	
		
		

		
		
	


	




 By the way, a head's up for anyone following this thread: quantities are getting very low on these kits -- single digits. When they are gone, I am undecided whether there will be another run or not. Also, supposedly Digikey is no longer stocking the PCM2706 and PCM2707 (the kit now comes with one.) 

 -d


----------



## FallenAngel

dsavitsk: Definitly do another run, this HPDAC is a definite must for anybody that wants to take the "one component does everything" approach to the entire headphone music idea. I totally love this thing as my office DAC + Amp, definitly the ONE MUST HAVE thing if you listen to music in the office and want an easy way to do so. Like most people, I'm sure, I can't install a soundcard into my office PC and don't really want to bring in another Source + AMP + Power for everything, so for me this HPDAC is PERFECT!


----------



## dhp

finally, my order has been placed and I"ll get that stinking diode!!!


----------



## blargman

I'm surprised there's even an question of another run, even if someone has you make one for them dsavitsk, its still nearly half the price of a corda aria. I have no reference to compare, but probably just as good.


----------



## K2Grey

Yes, do another run


----------



## Rayman2k2

Yes! Please do another run! This is precisely what I was looking for!


 However, would there be someone who could build it for me?


----------



## dsavitsk

Quote:


  Originally Posted by *Rayman2k2* 
_Yes! Please do another run! This is precisely what I was looking for!_

 

You are a little premature. I still have a few left.

  Quote:


 However, would there be someone who could build it for me? 
 

For builders, you can look through the thread for people who have built them and ask them ... or maybe someone will speak up ... 

 I appreciate the encouragement. The biggest factor (though not the only one) for whether another run of boards happens is availability of the pcm2707. Digikey is out (the kits come with one) and is listing it as non-stock. If this is true for the future, it means that there will be a minimum order quantity. If this quantity is 25 , that may be okay, but if it is 250 or 1000 then it is too many chips for me to keep on hand. Other factors include finding builders and a few other things.

 -d


----------



## FallenAngel

According to Texas Instruments, their lead time for the PCM2707 is one week, hope that means that in a week or so, they'll ship out inventory to the distributers and digikey will have stock again.


----------



## sjlee001

I know this is a dump question since there could be a million different things wrong, but I just build my HPDAC last night and when I plugged it in, all I got was a little buzzing when I turned the volume all the way up. I'm hoping this is a typical problem and there's an easy solution.

 On another note, I went to the TI website and you can get free samples of the PCM2707....

 Thanks,

 Stephen


----------



## ezkcdude

Quote:


  Originally Posted by *sjlee001* 
_I know this is a dump question since there could be a million different things wrong, but I just build my HPDAC last night and when I plugged it in, all I got was a little buzzing when I turned the volume all the way up. I'm hoping this is a typical problem and there's an easy solution.

 On another note, I went to the TI website and you can get free samples of the PCM2707....

 Thanks,

 Stephen_

 

As said before, check for shorts...and then check again and again.


----------



## sjlee001

ezkcdude:

 Thanks for your suggestion! Actually, I forgot to clean off the flux last night, it was 1 AM.... I cleaned it off this morning and it works! Sounds great out of the box, I'll let it run for a bit and see how it goes. 

 Thanks Doug!!


----------



## blargman

sweet got this baby today from Fallenangel. my headphone outs were waayy to underpowered. I can fully blow out my ear drums now!

 only got cheap k81djs hooked up to it now, but its definitely doing its job of amping. sounds good. doesn't sound bad. i don't know any audiophile mumbo jumbo. so i'll just leave it at that


----------



## labmat

I recieved two HPDAC kits today and would like to know if anyone here has put together a digikey or mouser bom for the remaining components.

 Thanks,


----------



## FallenAngel

Read Page 3 of this post.


----------



## labmat

Thanks FallenAngel.

 Can anyone tell me where I can purchase that large Black Gate Capacitor, I'm not terribly familiar with vendors outside Digi and Mouser.

 Later,


----------



## dhp

Quote:


  Originally Posted by *labmat* 
_Thanks FallenAngel.

 Can anyone tell me where I can purchase that large Black Gate Capacitor, I'm terribly familiar with vendors outside Digi and Mouser.

 Later,_

 

maybe partsconnexion, although not sure if it's necessary at all


----------



## labmat

I'm going to build one with the black gate and one with different caps to see how the two sound.

  Quote:


  Originally Posted by *DieInAFire* 
_maybe partsconnexion, although not sure if it's necessary at all_


----------



## dsavitsk

Quote:


  Originally Posted by *labmat* 
_I'm going to build one with the black gate and one with different caps to see how the two sound._

 

Digikey part P12408-ND is a 150uF panasonic FM that will fit the spots on the board. Use a pair of those + some high quality 47uF caps (silmics, cerafines, etc.), or use 3 of the panasonics. In this context I think this should be almost as good as the BG.


----------



## Samgotit

Ok... so... since all of you pillaging DIYers have sacked Digikey of both the PCM2706/7 and the Panasonic pot, anyone want to sell me 2 pieces of each. 
	

	
	
		
		

		
			





 The usual suspects (Mouser, Newark, Futurlec) don't stock either.


----------



## psilosome

I ordered parts last night and saw that Digikey doesn't expect the 10k pot in stock until December (my kit came with the PCM chip). I'm going to try a 50k pot from my parts bin, increasing R2L and R2R to 499k. Has anyone tried this pot and seen instability? I also ordered some bandwidth-limiting caps just in case (C27, C28, Digikey no. 338-1347-ND).


----------



## dsavitsk

Quote:


  Originally Posted by *psilosome* 
_I ordered parts last night and saw that Digikey doesn't expect the 10k pot in stock until December (my kit came with the PCM chip). I'm going to try a 50k pot from my parts bin, increasing R2L and R2R to 499k. Has anyone tried this pot and seen instability? I also ordered some bandwidth-limiting caps just in case (C27, C28, Digikey no. 338-1347-ND)._

 

Edit: The only other 10K pot that seems okay is also out of stock. So, use a 20K and increase R2L ad R2R to 200K, or do as psilosome suggests and use 50K/500K. Should be fine.


----------



## blargman

ermm, anyone know what could my HPDAC to all of a sudden start sounding like an AM radio? :\ 

 been working fine but now it has all kinds of strange interference sounds and such. and i can hear noise from moving my mouse and things where i couldn't before. :\


----------



## MisterX

Did you try unpluging and repluging it into the computer?


----------



## blargman

yeah, i'm letting it sit now for a bit, to see if its a heat issue. i just read some of the earlier posts. erm, it appears i got FA's one that was having distortion issues b4 perhaps 
	

	
	
		
		

		
		
	


	




 doh!

 *edit* hrm, didn't appear to change anything. argh


----------



## FallenAngel

You're using USB2.0 right? HPDAC needs quite a bit of current that I think only USB2.0 can provide. I was having trouble with using this thing on a really old laptop with USB 1.1 and got the same issue, just not enough current which resulted in not enough voltage past the regulator, plugged it into a normal computer with USB 2.0 (so far works great on my new desktop and work computer).

 Edit: After some more reading on the USB standard, 500mA is the amount of current USB should provide. Most PCMCIA laptop USB cards do not provide that, nor do USB Hubs. And from experience, old laptops don't provide that either.


----------



## dsavitsk

Quote:


  Originally Posted by *FallenAngel* 
_Edit: After some more reading on the USB standard, 500mA is the amount of current USB should provide. Most PCMCIA laptop USB cards do not provide that, nor do USB Hubs. And from experience, old laptops don't provide that either._

 

No, they probably don't. I would not use this dac on a hub or an extension card or with other usb deviced plugged in. It is a little bit of a pig as far as usb current is concerned.


----------



## FallenAngel

Definintly not a good idea to use this with a hub (especially people who have one in their LCD monitor or keyboard, these are low-powered), maybe with a powered usb hub, but that's still a maybe.

 Best case scenario would be to use this on it's own USB HOST, most computers come with at least 2 now, usually 3 or 4. Just plug it into one "bunch" (best way to explain it) of USB ports without any others connected to the same one. Usually you'll have 1 or 2 4-Port hubs on the back of the computer and another 1 2 or 4-port in the front. Use either one, but try to make sure nothing else is using the same one. If you go to Control Panel->System->Hardware->Device Manager, under Universal Serial Bus Controllers, take a look at how many "USB Root Hub"s you have, it'll tell you how much stuff you can plug into, but remember, that's just how many you have in your computer, not necessarily how many are connected from the motherboard to an actual port. This means you might have 4 USB Root Hubs on your motherboard, but only have 1 or 2 hubs at the back of the case.


----------



## blargman

thanks guys, i really don't think its a power issue as it was working fine for a few days, but i did just try it plugged into its own usb host, still giving the same problem. its a desktop i've got it plugged into, and i tried both the ports on the front and the back.

 the biggest thing i've noticed that its doing, is i can hear mouse movements, disk access and the the like, when i couldn't before. perhaps its some sort of power conditioner or noise remover part you have in the design thats loose/shorted? ya sry its a dumb statement but its the only thing i can think of. 

 :\

 *edit* sry didn't answer before, ya its usb2


----------



## dsavitsk

Quote:


  Originally Posted by *blargman* 
_thanks guys, i really don't think its a power issue as it was working fine for a few days, but i did just try it plugged into its own usb host, still giving the same problem. its a desktop i've got it plugged into, and i tried both the ports on the front and the back._

 

Can you try it on another computer? 

 Does it still play music, and if you are not doing any mouse movements, etc. does it still sound clear, or is the music garbled?

  Quote:


 the biggest thing i've noticed that its doing, is i can hear mouse movements, disk access and the the like, when i couldn't before. perhaps its some sort of power conditioner or noise remover part you have in the design thats loose/shorted? 
 

The things in the design that remove noise are things that if they came off would, in many cases anyway, cause it to not work at all. However, cold solder joints might be something to look for. Can you post closeup pics of the top and bottom of the board?


----------



## blargman

i'll see what i can do about the pics. probably won't be able to get it til tomorrow. im' at work atm with no camera. or screwdriver 
	

	
	
		
		

		
		
	


	




 tried on another pc. as far as when music plays, it sounds pretty bad. like a badly blown out speaker on an am radio, to put it another way, ya it sounds real garbled.

 thanks for trying to help tho guys, i'll get pics up asap.


----------



## labmat

Hey guys,

 I completely assembled one of my HPDAC kits today (I'm waiting for the blackgates for the other DAC) and the DAC seems to work except the sound coming out of the amp portion is really lopsided to the right channel. I need to turn the pot 1/2 way to get the left side to the same level the right is at 1/8 of a turn.

 What could possibly cause this? I had to leave work in a rush and didn't get a chance to measure any voltages; where should I start looking tomorow?

 Thanks,


----------



## Heady

Quote:


  Originally Posted by *labmat* 
_Hey guys,

 I completely assembled one of my HPDAC kits today (I'm waiting for the blackgates for the other DAC) and the DAC seems to work except the sound coming out of the amp portion is really lopsided to the right channel. I need to turn the pot 1/2 way to get the left side to the same level the right is at 1/8 of a turn.

 What could possibly cause this? I had to leave work in a rush and didn't get a chance to measure any voltages; where should I start looking tomorow?

 Thanks,_

 

Sounds like you could have wired up the vol pot as a balance control.


----------



## dhp

Is the middle pin the input pin on the vreg?


----------



## labmat

I used a different 10k pot (EVJ-CC1F02651) than was specified since digi is out of the (EVJ-C20F02D14) it was recomended here as a potential replacement. Is this the root cause of my issue? After listening some more it is clear that there is no real volume on the left channel; sound is just kind of there but barely.

  Quote:


  Originally Posted by *Heady* 
_Sounds like you could have wired up the vol pot as a balance control._


----------



## dsavitsk

I think that's your problem. I'd remove it and go with a 20K or 50K pot -- just remember to increase R2L and R2R accordingly.


----------



## labmat

I just ordered a 20k and 50k pot and some 200k and 500k resistors. I should get them monday; I'll let you know how it goes.

 Thanks,

  Quote:


  Originally Posted by *dsavitsk* 
_I think that's your problem. I'd remove it and go with a 20K or 50K pot -- just remember to increase R2L and R2R accordingly._


----------



## ngrady

Hi Everyone,

 I recently finished building my HPDAC, but I’m having a few issues with it:
 (1) There is a significant amount of hiss. How much should I expect? It varies with the volume control setting. It is enough to be noticeable during quite parts of music at modest volume levels. I haven’t cleaned the flux yet, but I don’t know if that would make a difference – planning to do that tonight. 
 (2) The DC offset at the headphone jack is quite high when I turn the volume up. At the output side of CR, CL, and CG the DC voltage ranges from 0.2 mV on all three with the volume control turned all the way down, to 12.9, 13.0, and 0.2 mV, respectively with the volume control all the way up. Between the headphone jack shield and either left or right I have about 80 mV DC without any sound playing. 
 (3) The DAC chip gets fairly warm – not “ouch” warm, but definitely significant. How hot should it be getting?
 (4) I only measure 7.82 V across the C2 capacitor bank and at the output of VR1. At the VR1 input, I see 9.21V between ground (middle pin) and input. The output seems quite a bit off from 8 V. Alas, I only bought one VR1, so I can’t just swap it. Do you think the problem is VR1 itself, or is this indicative of another problem. 

 I did make a few mistakes assembling the board, which perhaps have lead to some of these problems. The first was accidentally installing C1 backwards (I guess after finally wrapping my head around SMT caps having + marked with a line, I slapped that one in backwards). I wasn’t sure if the cerafine would still be ok, so I put a spare 47 uF Nichicon UPW (the caps are actually labeled PW(M), but the Mouser catalog says UPW) in its place. 

 The other was the infamous “USB device not recognized” issue. It of course turned out to be the PCM2706 soldering job (it’s my first time soldering a QFP), but I replaced it and VR3 in the process of figuring this out. If you’re having this problem, really really really carefully check that the PCM is soldered well – I think one of the pins was floating above the pad a bit with solder on it, so it looked like it was connected, but really wasn’t. I removed it by removing as much solder as I could with solder wick, then heating and lifting each pin with a tweezers. The pads without any connections didn’t fair too well, but all of the pads with a trace running from them did just fine. In retrospect, I think the original chip was just fine. 

 Few Misc. Details: I used 2x47 uF and 2x100 uF Nichicon UPWs (couldn’t tell any difference between 4x47 and this combo, so I didn’t bother replacing the other two 47s with 100s). The volume control is an ALPS RK12L1210C0H from Mouser (which I think is basically the same as the Panasonic part). Op-amps are LM61721Ms.

 Anyway, sorry this post got a little excessively long.

 Thanks!


----------



## zip22

what is an approximate build cost? i was thinking of bulding an alien and then a pimeta, but this is really exactly what i have been looking for.


----------



## dsavitsk

Quote:


  Originally Posted by *ngrady* 
_(1) There is a significant amount of hiss. How much should I expect? It varies with the volume control setting. It is enough to be noticeable during quite parts of music at modest volume levels._

 

Some hiss is normal, but you should only ear it at high volumes (though my high may be your moderate). If you are hearing it at low volumes it sounds like something is amiss.


  Quote:


 (2) The DC offset at the headphone jack is quite high when I turn the volume up. At the output side of CR, CL, and CG the DC voltage ranges from 0.2 mV on all three with the volume control turned all the way down, to 12.9, 13.0, and 0.2 mV, respectively with the volume control all the way up. Between the headphone jack shield and either left or right I have about 80 mV DC without any sound playing. 
 

Some offset is normal. It shouldn't change with music playing, but it will increase when the volume is turned up. 80mV does seem pretty high. I'd check that R1* through R4* are correct.

  Quote:


 (3) The DAC chip gets fairly warm – not “ouch” warm, but definitely significant. How hot should it be getting? 
 

This seems a little odd. Mine don't really get warm at all, but this could also be a different definition of warm. Certainly not hot, though. These chips are not made to a tight tolerance, so I can send you another one if you'd like to try it. Send me a PM if you want to try that. It would not account for the high offset, though.

  Quote:


 (4) I only measure 7.82 V across the C2 capacitor bank and at the output of VR1. At the VR1 input, I see 9.21V between ground (middle pin) and input. The output seems quite a bit off from 8 V. Alas, I only bought one VR1, so I can’t just swap it. Do you think the problem is VR1 itself, or is this indicative of another problem. 
 

7.82 is well within the tolerance of the chip (http://focus.ti.com/lit/ds/symlink/tl750l05.pdf), so I would not worry about that.


----------



## dsavitsk

Quote:


  Originally Posted by *zip22* 
_what is an approximate build cost? i was thinking of bulding an alien and then a pimeta, but this is really exactly what i have been looking for._

 

I think it is in the $70 to $80 range depending on the options you choose.


----------



## ngrady

Quote:


  Originally Posted by *dsavitsk* 
_ Some hiss is normal, but you should only ear it at high volumes (though my high may be your moderate). If you are hearing it at low volumes it sounds like something is amiss.

 Some offset is normal. It shouldn't change with music playing, but it will increase when the volume is turned up. 80mV does seem pretty high. I'd check that R1* through R4* are correct._

 

Ok - I'm probably being too picky about the hiss then. I’ll double-check R1* through R4* when I get home to make sure I didn’t goof somewhere. At normal volume levels I only have about 20 mV DC offset (~ ¼ of the way up on the volume pot), and barely noticeable hiss. Overall the sound is excellent; definitely a massive improvement over dreadful sound my computer generated before, and slightly better than the headphone jack on my stereo. 
  Quote:


  Originally Posted by *dsavitsk* 
_ 7.82 is well within the tolerance of the chip (http://focus.ti.com/lit/ds/symlink/tl750l05.pdf), so I would not worry about that._

 

D'oh - should have read the data sheet before posting!


----------



## he46570

Now that Doug has a new stock of boards, I'm jumping on the bandwagon too! 

 So if anyone would like to sell me parts for one HPDAC, that would be most appreciated. I'm especially interested in the pot, surface mount components and others which need to be purchased in lots of 10 or so. I'll be willing to pay purchase price plus 50% plus shipping. Please let me know.

 Thanks!


----------



## civilmonkey

Hey all,

 I finished my HPDAC using Fallenangels parts he sold me. It works perfect. 

 I used 2 x 33 uF and 2 x 150 uF (digikey P12408-ND), panasonic FM series. It sounds great to my ears. The bass seems as punchy as my pimeta with 4 x 470 uF cerafines. I don't seem to hear the hum you hear in a stadium (e.g. live recording) as much though.

 Anyways, works for me great, thanks Dsavitsk!


----------



## dakotart1984

Just got my pcb's today, thanks dsavitsk. Seems all you diy'ers have put digikey back on a lot of these parts though. I cant find nearly half of the parts I need and Fallenangel didnt have a part listed for the usb since it was to be included with his pcb's. If anyone out there has any leftovers please let me know.. I can at least use 2 EVJ 10k's for the moment and a PN on that usb jack would be aprreciated.


----------



## Polaris111688

This thing is serious stuff. I got my fully-assembled HPDAC from dsavitsk today and gave it a test run. Even on a pair of crappy Sony MDR-V150s, it sounds pretty darn good. I'll give it another impression once I get my Grado SR-225s here.


----------



## dsavitsk

Quote:


  Originally Posted by *dakotart1984* 
_Just got my pcb's today, thanks dsavitsk. Seems all you diy'ers have put digikey back on a lot of these parts though. I cant find nearly half of the parts I need and Fallenangel didnt have a part listed for the usb since it was to be included with his pcb's. If anyone out there has any leftovers please let me know.. I can at least use 2 EVJ 10k's for the moment and a PN on that usb jack would be aprreciated._

 

The usb jack that I use is from Mouser, part #571-7877801. There is one at digikey that will work, but I'll need to look it up -- or someone else can. Digikey is out of the cases too, so you'll need to get the case at Mouser anyway. Oh, and the part number for C3 and C4 is 505-MKP20.1/100/5.

 For the pot, use a 20K (EVJ-C20F02D24) and increase R2L and R2R to 200K.


----------



## MisterX

For the USB receptacle try Digikey #AE9925-ND


----------



## dsavitsk

Quote:


  Originally Posted by *MisterX* 
_For the USB receptacle try Digikey #AE9925-ND_

 

or WM17113-ND or WM17131-ND or 151-1081-ND I think.


----------



## MisterX

Quote:


 or WM17113-ND or WM17131-ND or 151-1081-ND I think. 
 

Yup, all look like they will work. 
	

	
	
		
		

		
			






 A31725-ND looks very similar to the one you suggested from Mouser. 

 609-1039-ND also looks promising.


----------



## error401

Quote:


  Originally Posted by *MisterX* 
_Yup, all look like they will work. 
	

	
	
		
		

		
		
	


	





 A31725-ND looks very similar to the one you suggested from Mouser. 

 609-1039-ND also looks promising. 
	

	
	
		
		

		
		
	


	


_

 

Got my parts today - but still waiting on the board (dsavitsk, I hope you don't send an e-mail when you ship these or I've got a while to wait yet!). Anxiety!!

 I ordered 609-1039-ND and it looks to be pretty much identical to the recommended Mouser one. The AMP is probably higher quality though, I missed that one when I was building my BOM. Guess I got lucky with one of the last Hammond cases.

 I did make one stupid mistake though. Ordered 1.2R resistors instead of 1.2K for R3L and R3R. I plan to sub either 1.5K or 1.0K. If I understand the circuit correctly, this could potentially make the amp unstable or cause other issues. Is it safe to use 1.0K here instead, or should I try and jerry-rig a standard 1/4W here (or go spend >$25 more at digi to get the right part - not that I don't want to build those AlienDAC board I just bought, but I'd rather not spend the cash right now...). Also, why are these values two full orders of magnitude smaller than Tangent's in the PINT?


----------



## dsavitsk

Quote:


  Originally Posted by *error401* 
_dsavitsk, I hope you don't send an e-mail when you ship these or I've got a while to wait yet!_

 

Not always. I think your board went out Monday.

 For the resistors, I'd try the 1K or 1.5K and measure the offset, the LM6172 isn't that unstable -- but note that offset will increase as the volume increases, so measure at various ranges.


----------



## dakotart1984

Would anyone suggest the ALPS version of the EVJ.. Mouser# 688-RK12L1210C0H ??


----------



## dsavitsk

Quote:


  Originally Posted by *dakotart1984* 
_Would anyone suggest the ALPS version of the EVJ.. Mouser# 688-RK12L1210C0H ??_

 

The word on the street is that the alps pot is of lower quality than the evj, but I have no personal experience to verify this. My guess is that it won't make much difference one way or the other.


----------



## Magsy

C20 and C24

 Can I use ceramic here as mentioned in MisterX's parts list or tant only as on ecp.cc ?

 The tants don't seem to be listed in 'case size' a,b,c and not as 0805/1206


----------



## psilosome

Quote:


  Originally Posted by *Magsy* 
_C20 and C24

 Can I use ceramic here as mentioned in MisterX's parts list or tant only as on ecp.cc ?

 The tants don't seem to be listed in 'case size' a,b,c and not as 0805/1206_

 

I did order tants in this size from Digikey:
 511-1474-1-ND CAP TANT 1.0UF 20V 20% SMD C23
 511-1461-1-ND CAP TANT 4.7UF 10V 20% SMD C24 *[EDIT -- THIS IS THE WRONG SIZE! Should be 0805]
*
 These are both manufactured by Rohm, "Package / Case 1206 (3216)"

 I'm in the middle of moving house and all of my electronics are packed away, so it will be some time before I can try these.


----------



## Magsy

Well I've figured out that 'Case Size A' is the same as 1206, but that still leaves it hard to find the single 4.7uf tant needed in 0805.

 I am in the UK and D-K wants a nearly $40 in shipping - it is too much for a small order


----------



## psilosome

Magsy, I've sent you a PM


----------



## Magsy

Ah god bless Headfi, thank you psilosome


----------



## error401

I ordered DigiKey 511-1461-1-ND, 4.7uF Tantalum in 0805.


----------



## Magsy

Are these suitable ferrites? 
	

	
	
		
		

		
		
	


	




http://uk.farnell.com/jsp/endecaSear...sp?sku=3056582


----------



## dsavitsk

Quote:


  Originally Posted by *Magsy* 
_Are these suitable ferrites? 
	

	
	
		
		

		
		
	


	




http://uk.farnell.com/jsp/endecaSear...sp?sku=3056582_

 

Should be fine.


----------



## altape

Well, I finally got the last of the parts I needed today. Plugged it into a usb hub just in case there were some electrical issues, and the usb hub is dead now. :/ Oh well, I need a new one anyways.

 However, the board works fine now plugged directly into my laptop.







 And sounds great!

 I missed the part about needing some 1.5kOhm smd resistors, so I improvised with some radioshack 1k and 470k resistors. You can see them sticking out from under the board.

 I used some tantalum resistors for RIVR and RIVL, blackgates for CR/CL/CG/C1. Gonna have some panasonic FM caps for C2, though I don't expect them to help too much. Right now there's just some generic nichicon caps from Mouser in there right now.


----------



## dsavitsk

Quote:


  Originally Posted by *altape* 
_I used some tantalum resistors for RIVR and RIVL, blackgates for CR/CL/CG/C1._

 

This is the same setup I use which I like very much.

  Quote:


  Originally Posted by *altape* 
_Gonna have some panasonic FM caps for C2, though I don't expect them to help too much._

 

You might be surprised at the difference changes here make. I have settled on 2x47uF BG Std and 2x 150uF FM. 400-470uF seems to be a good amount, and high quality tightens up the bass a lot. The BGs are better than Cerafines which are a bit better than Silmcs to my ear. Silmics seems to have more bass than the cerafines, but the cerafines are a little tighter perhaps. MisterX uses a single 470uF BG on its side, but I have not heard it to know how it compares.

 -d


----------



## FallenAngel

Quote:


  Originally Posted by *altape* 
_Well, I finally got the last of the parts I needed today. Plugged it into a usb hub just in case there were some electrical issues, and the usb hub is dead now. :/ Oh well, I need a new one anyways.

 However, the board works fine now plugged directly into my laptop._

 

Buddy, you gotta clean up the solder on that PCM2706 and as for the usb hub, just a few pages back, we established that unpowered USB hubs will not work with this. Unless you've got extra power going to that hub, it will not work, same with usb on keyboard or usb on monitor.


----------



## altape

Quote:


  Originally Posted by *FallenAngel* 
_Buddy, you gotta clean up the solder on that PCM2706 and as for the usb hub, just a few pages back, we established that unpowered USB hubs will not work with this. Unless you've got extra power going to that hub, it will not work, same with usb on keyboard or usb on monitor._

 

And in fact, I did have a huge wallwart attached to the hub, with the bus/self power switch on the hub set to self power. I've used it to power external hard drives before.

 The solder and flux on the pcm2706 can't be too bad, though I'm gonna clean up the gunk after fedex drops off my flux remover (among other items). It's doubtful the gunk there is a serious problem since it does seem to work well. The flash is making the flux look nastier than it actually is. If the soldering job on the pcm2706 were a problem, I'd expect no audio or very very badly butchered audio since it's all digital stuff there.


----------



## dsavitsk

Quote:


  Originally Posted by *altape* 
_The solder and flux on the pcm2706 can't be too bad, though I'm gonna clean up the gunk after fedex drops off my flux remover (among other items). It's doubtful the gunk there is a serious problem since it does seem to work well._

 

The problem with flux is that current leakage can develop over time. It typically won't manifest itself in the short term, but can cause something to stop working later on.


----------



## altape

I was looking at the EVJ pots that digikey has in stock today, and I was wondering if using a 5k pot would work fine (with R2L + R2R lowered to 50k ohms, of course), and if it might reduce the hiss since I'm using a 20k ohm pot. Any reason using a lower ohm pot might be bad?


----------



## FallenAngel

I always thought the only real reason to use a high resistance pot was because some sources don't like low output resistance, but if the "source" is the dac chip, I don't know if it would matter much.


----------



## dsavitsk

Quote:


  Originally Posted by *altape* 
_I was looking at the EVJ pots that digikey has in stock today, and I was wondering if using a 5k pot would work fine (with R2L + R2R lowered to 50k ohms, of course), and if it might reduce the hiss since I'm using a 20k ohm pot. Any reason using a lower ohm pot might be bad?_

 

You generally want the input impedance of a stage to be at least 10x the output impedance of the previous stage, else you will get some high frequency rolloff. The output impedance of the DAC stage is about 1K, so 10K is really the minimum you would want. 20K or 50K is also fine, but 5K is probably too low.


----------



## Pappucho

Quote:


  Originally Posted by *altape* 
_I missed the part about needing some 1.5kOhm smd resistors, so I improvised with some radioshack 1k and 470k resistors. You can see them sticking out from under the board._

 

Hey, wouldn't that give you 471K? 
	

	
	
		
		

		
		
	


	




 Judging from your pic, looks like you've got it right..... 1K and a 470.


----------



## MisterX

Image removed

  Quote:


 MisterX uses a single 470uF BG on its side, but I have not heard it to know how it compares. 
 

560uF Panasonic FC this time.
 I originally had a 680uF cap in there but windows didn't seem to like that one very much.


----------



## dsavitsk

There appears to be a small bug in the schematic and hence in the board. To date, there have been no reports of problems being caused by it, but if you are concerned, it is an easy fix. 

 Pin 11 (SSPND) on the PCM2707/PCM2706 is powered while it should not be (it actually provides voltage to turn on some DAC chips.) To disable this, you can either cut the small trace that connects pin 10 to pin 11 (it is right between the two pads -- this is most easily done before the board is built) or, once assembled, use an X-acto knife to cut pin 11 off of the chip.

 A third possibility is that you might be able to use the SSPND pin to power the Test (10) pin which must be set high. To do this, you would simply not populate L8. I have not had the chance to test this yet to know if it will actually work but it is a simply enough experiment to try.

 -d


----------



## error401

Well, aside from the PCM2706/7 I didn't think this'd be very difficult, and I'm still not totally sure what I screwed up - but apparently I pooched my attempt pretty well. It's been a while since I've done SMD (or electronics in general, really) and I'm making noob mistakes. Hopefully someone has some advice for me. I'll list my (discovered so far) errors below in the order I caught them.

Ordered 634R and 100R resistors for R5/R6 due to sleep deprivation. Caught this before I even received my order. In my initial attempt at firing up the HPDAC I jerry-rigged what I had on hand after consulting the datasheet to end up with a 1.5M R6 (1M 1206 in series with 499K 1/4W) and a 200K R5 (200K 1/4W), this should've got me a reasonable output.
Installed both TO92 regs backwards. Apparently not everyone bends the leads in the same direction I consider 'normal'...fried 'em both and replaced them both with fresh ones.
Did a piss-poor job of soldering the PCM2706 (I really should've built the power supplies first, and wanted to, but I followed the 'solder this first' instruction on the page for some reason instead of building in a modular, testable way...). Pins 9 and 10 were shorted, resulting in basically no voltage on any of the rails (0.8V) due to USB current limiting, I assume.

 So where I'm at now is pretty dismal. I don't think there are any atrocious shorts anymore as I've got reasonable voltage on the power supply rails. I also measured every pin on the PCM2707 with its neighbour and found no shorts there either. The rest of my soldering is pretty clean and I doubt there's anywhere else that could be shorted. I think the switch in the DC-DC might've failed open (~5V would pass, AFAICT), or is in some sort of protection mode due to something I'm missing. This seems to correspond with what I'm measuring too since when I'm metering the voltage it sticks to ~5V but seems to jump to 9V occasionally, then quickly drops back down to 5V again, though I'm not positive it isn't just my cheap meter acting up since it's *very* brief. I'm not measuring a short directly on the high rails, but that obviously doesn't mean there isn't one. 3.3V reg outputs a clean 3.3V now. If I crank the pot I can hear a very small amount of noise, so I think the amp section is doing _something_, even on 5V rails. The device is not detected by the OS when plugged in, and I'm scared to leave it in for too long.

 Long story short - does this sort of failure correspond to a simple failure of the DC-DC or do I have bigger issues? Anyone spot anything wrong with the board (yes, the soldering on the TQFP is atrocious, but I'm reasonably confident it's workable). And finally, would any kind head-fier be willing to let me piggyback an order (or if you've got some spares left over) for a couple of the TPS61040; I'll obviously pay shipping + cost + tip.

 Board (no alcohol on hand to clean the flux - project for tomorrow - but shouldn't prevent it working):


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## dsavitsk

A couple of things to be concerned with. First, I would remove the flux as this can cause problems. Second, the pins of the USB jack do not look well soldered. Third, pins 9-16 on the PCM look off a bit. Make sure that there are no shorts there, and that each pin is actually on the pad it should be. 

 If you are not getting recognition from the computer, then there is a PCM issue. Whether it is the chip, or the usb jack, is hard to know. These are fairly fragile chips, so a misapplied voltage, or just mishandling the chip can cause problems. But, first make sure all the connections (including the usb jack) and voltages are as they should be.

 Also, if the DC-DC converter is giving weird results, it might be oscillating. Cleaning the flux may help here too.

 For general advice, I find very thin solder and a very small iron to be the key here. The less solder you can use the better.


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## cantskienuf

It was snowy and cold in Denver today - perfect reason to finish the HPDAC. This was my first attempt at surface mounted devices. Yes, I did get to where I could do it pretty well, but it is still a pain in the eyes. DAC worked first try and I'm listening to a little Boney James through it right now. Sounds really nice. Quiet background, really good detail. Went with three Panasonic FM 150uF caps in C2 positions, a Blackgate 47uF in the C1 position, Blackgate 4.7uF in the CR, CL & CG spots, tantalum resistors in RIVL and RIVR, Vishay Dales in the R1R, R1L, R2R (200K), R2L (200K) and REF positions and the 20K Panasonic pot. Guess I'll let those Blackgates burn in while I do a little casework - but its gonna be hard to take the headphones off and go into the garage to drill on the Hammond. Thanks D! Great design.


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## cantskienuf

I've been running the DAC at the office this week trying to get some time on those Blackgates. While I had absolutely no problems on the home computer (where there are wood floors) I've found that in the office (with carpeted floors) when I return to my desk and touch the HPDAC, my computer monitor goes black and the computer is locked up. Although I haven't noticed any sparks, could static be traveling up the USB and confusing the computer enough to cause a shutdown? I didn't address grounding in the HPDAC case at all, is there something I need to do in that arena? I used the small Hammond case and the only contact point is the board edge and the body of the Panasonic potentiometer. Of course there is a simple solution, I'll take a patch cord in tomorrow, attach it to the chassis ground on the rear of the computer and make sure I touch it before touching the DAC. That should tell me if it is indeed a static problem.


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## dsavitsk

Short answer is, I am not sure. The slightly longer answer is that the HPDAC has 3 grounds. The real ground, which is your computer's ground, acts as the ground for the DAC portion and the negative rail for the amp section. Ground #2 is the amp section's virtual ground. Ground #3 is the output ground.

 The metal on the EVJ is isolated as is the USB jack. The only part that might not be is the metal ring on the recommended output jack. Since most people are using the case with the plastic end panels, this is not an issue at all. If you are using the case with the metal end panel, it should still not be an issue unless something else is touching the case. So, basically, the case is probably isolated, but at worst could be connected to the buffered ground.

 As for the computer issue, it is possible for a shock to cause a problem, but this would likely be an issue with the computer itself and how it is grounded. But, the computer's ground is connected directly to the hpdac, so it is worth investigating.


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## Magsy

I've had the reboot thing too with Guzzler's USB Dac, infact by shorting USB power you can reboot at will 
	

	
	
		
		

		
			





 I have had the machine reboot once when I touched the DAC and a metal radiator, so that sounds similar to yours...

 I didn't actually do anything to fix it other than case it properly - it does not come into contact with the chassis at all and all connectors are isolated.


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## civilmonkey

Quote:


  Originally Posted by *dsavitsk* 
_The metal on the EVJ is isolated as is the USB jack. The only part that might not be is the metal ring on the recommended output jack. Since most people are using the case with the plastic end panels, this is not an issue at all. If you are using the case with the metal end panel, it should still not be an issue unless something else is touching the case. So, basically, the case is probably isolated, but at worst could be connected to the buffered ground._

 

I used metal case / ends. Two things. I found that I hadn't trimed excess leads from the underside of the board enough and they were contacting the case causing problems. I also ended up isolating the USB jack and POT, but not the output jack. Although I just read the jack and pot are already isolated... I could have sworn my multimeter told me different.


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## dsavitsk

Quote:


  Originally Posted by *civilmonkey* /img/forum/go_quote.gif 
_Although I just read the jack and pot are already isolated... I could have sworn my multimeter told me different._

 

You might trust your multimeter over me. Mine just got through telling me that a 160V supply was 450V. Mine did seem to be isolated, but it is probably better to be safe and consider them grounded.


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## jdimitri

Sorry to go OT, but is the hpdac asio compatible?
 Mine should be here soon, i'm just wondering what i should do to get asio etc working in foobar
 Thanks!


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## MisterX

ASIO4all is all it takes.


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## nleahcim

I'm a little late here - but are there still PCBs available?


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## psilosome

Quote:


  Originally Posted by *nleahcim* /img/forum/go_quote.gif 
_I'm a little late here - but are there still PCBs available?_

 

It looks that way


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## nichone

Hi

 I put together a HPDAC with standard parts and it worked for two
 songs. I got up and swapped headphones and got no sound. 
 After much examination, resoldering, replacing the USB socket, DMM testing,
 and retesting, I can get it to work - or not. Sometimes still I get nothing;
 LED lights but no hiss or sound. More commonly now I get an tincan sound
 where the lows and highs are missing. But if I flex the PCB in the correct corner I get full sound. I have to put my right hand thumb below the end
 of the board and my fingers presssing down on the USB socket housing and
 cable connector. 
 I initailly thought the USB to PCB ground connection was bad or 
 shorted. I had found the "fix" by bending down the USB connection.
 A resistance check showed a poor connection ( end of USB cable to PCB 
 bottom ). Changing cables and computers did nothing. I played with the 
 socket until I just replaced it. Initially I also had low output voltage at the 
 5 volt regulator which was affected by the bending PCB. Now fixed, 
 The voltages are good at the outputs now - whether the sound is tincan or normal. 
 I have to be closing a gap or breaking a short, but where ? Any ideas ?

 Thanks in advance. John.


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## Clutz

I would go back and try re-flowing each of the solder joints - possibly with some liquid fluid, and then clean the board up really well using denatured alcohol. It sounds to me like you have a cold solder joint somewhere.


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## nichone

Thanks. You were right. I was worried about component failure. 
 After posting I again retested every connection - device lead to distal 
 device - all checked out OK. Then while rechecking the voltage outputs
 I flexed the headphone jack end ever so slightly and got the good sound.
 I redid every connection on that end of the board (again) and now it works.
 So I had the wrong side and some invisible poor joint - probably at the 
 opamp(s). I hope this helps someone else.


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## Magsy

4 o'clock in the morning but I am done, couple of issues, mainly offset from the AD 8058 I've fitted, fine until high volume then 50mv+ upto nearly 300mv at full. 
 Also it only seems to work in my apple usb keyboard (Intel PC), not direct in my usb ports - probably machine issue, I had similar thing with Guzzler usb dac.

 But....It sounds totally amazing. I was ready to be disappointed compared to either my standalone DAC or the 0404 but it really holds its own in a quick test. It has loads of volume with my HD580, which is something I was worried about because I like it loud 
	

	
	
		
		

		
		
	


	




 No noise, even on my main rig which has every pci slot filled.

 Good job, I'm very happy


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## Polaris111688

Congrats, dude. Got pics?


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## Magsy

Needs to be cleaned up, the leads are temp just to check it works!

 All out boutique parts assault, BG N's all round and Riken resistors, AN8005/8 reg's (when they arrive)
 Forgot the Rikens for R1/R2, to be replaced next time I order!

 Not worried about the cost, I did it because I could!


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## Magsy

Seem to have a little problem with my REG101. I checked the output and it was the same as the input, 4.75v. I replaced it with a fresh one and it is the same.

 What could be causing the regulator to seemingly not regulate? I've reflowed all the joints but they look ok, all of the 3.3v pins on the pcm2707 read 4.75v 
	

	
	
		
		

		
		
	


	




 When using the REG101 I was supposed to populate everything right? Not leave anything out?

 Even with no Reg101, I read 4.75v across C9 and C11. I have checked and checked for shorts at the 2707 but I am almost positive there are none.

 Edit: I even read 4.75v across C8 with no Reg101 in place, the DAC also works without Reg101 installed!?! :|


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## Clutz

What is coming out of your DC/Dc converter?


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## Magsy

8.4v across C23, I have 620k instead of 634k in R6 because it was all I could get.


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## dsavitsk

Quote:


  Originally Posted by *Magsy* /img/forum/go_quote.gif 
_Seem to have a little problem with my REG101. I checked the output and it was the same as the input, 4.75v. I replaced it with a fresh one and it is the same.

 What could be causing the regulator to seemingly not regulate? I've reflowed all the joints but they look ok, all of the 3.3v pins on the pcm2707 read 4.75v_

 

I think there must be a bridge somewhere. Between C7 and C8 is the obvious spot, but it could be elsewhere too. Can you post high res pics of the top and bottom of the board

  Quote:


 Edit: I even read 4.75v across C8 with no Reg101 in place, the DAC also works without Reg101 installed!?! :| 
 

Not surprising, but also not ideal. You can run this on a higher voltage, but if you do this and leave in L6 and L10 you may be in danger of damaging the 2706. 4.75 is right on the edge of where it will work -- any higher and it will probably stop, and long term stability is unknown.


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## Magsy

Thanks, appreciate the help.

 This is the best I can do with the cameras I have here. I agree it seems very much like it's bridged somewhere, I'll check it out again. The PCm does get warm quite quickly and there is distortion if I turn up the volume in windows, if I turn it down it sounds fine..

http://magsy.net/headfi/hpdac/topdown.jpg
http://magsy.net/headfi/hpdac/angle.jpg
http://magsy.net/headfi/hpdac/back.jpg
http://magsy.net/headfi/hpdac/pcmcloseup.jpg


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## dsavitsk

Do you measure continuity between C7 and C8?


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## dsavitsk

Also, look at the ground pin of VR3. It looks like there might be a small bridge there.


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## Magsy

Yes, the inner of C7+8 have continuity, no resistance.


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## dsavitsk

Quote:


  Originally Posted by *Magsy* /img/forum/go_quote.gif 
_Yes, the inner of C7+8 have continuity, no resistance._

 

So there is definitly a short somewhere ... now you just have to find it. Fortunately, the amount of copper that should be continuous with C7 is small, so looking along it should yield an answer. The parts that are conneted directly to this buss are C7, L7, VR3, DC1, C24, L2, the USB Jack, and RLED.

 Around L7 and L8 might be a good place to check, too.


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## Magsy

Stupid question, C7+8, I have to remove the caps to test continuity ? Ive tested with them in but they are both connected to ground..


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## dsavitsk

Quote:


  Originally Posted by *Magsy* /img/forum/go_quote.gif 
_Stupid question, C7+8, I have to remove the caps to test continuity ? Ive tested with them in but they are both connected to ground.._

 

No. The caps block DC which defines continuity. You may get a short burst of continuity while the caps charge, but then they will block it. If you have an extra cap laying around, try measuring continuity across the leads to see this happen.


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## Magsy

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_No. The caps block DC which defines continuity. You may get a short burst of continuity while the caps charge, but then they will block it. If you have an extra cap laying around, try measuring continuity across the leads to see this happen._

 

Argh, http://magsy.net/headfi/hpdac/back.jpg

 I had the two ferrites mounted wrong, I blame the lack of silkscreen 
	

	
	
		
		

		
			





 Sorry! I feel like an arse, I've spent hours fiddling with this and made some things a little messy by resoldering, removing and replacing so much. I've been through 2 Reg101's, 2 DC-DC convertors, a few ferrites and caps. Kinda angry but happy also 
	

	
	
		
		

		
		
	


	




 It works fine now, although now that reg works I get the 'too much power' message off my Apple keyboard but it works direct.

 One problems still persists though and that is distortion unless the volume in windows is -10db (foobar) With volume lowered it works fine right up to ear bleeding levels via the pot. Anyone else had this? I have had this problem with my Guzzler DAC for a very long time, I assumed something had gone wrong but I couldn't be arsed to open the case up. (The Emu 0404 in the same PC is fine.)


----------



## dsavitsk

Quote:


  Originally Posted by *Magsy* /img/forum/go_quote.gif 
_One problems still persists though and that is distortion unless the volume in windows is -10db (foobar) With volume lowered it works fine right up to ear bleeding levels via the pot. Anyone else had this? I have had this problem with my Guzzler DAC for a very long time, I assumed something had gone wrong but I couldn't be arsed to open the case up. (The Emu 0404 in the same PC is fine.)_

 

What resistor do you have for vref and the i/v? I'm no good at reading the stripes, but vref is different which could account for something?


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## Magsy

I have resistors for 8v and I'm running 5v atm, so it could be that?

 I have 2 x 2k7 and 1 x 1k5 in there.


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## Magsy

For some reason I decided to swap out the 2707 instead of playing with i/v resistors first....big mistake. I stuck the replacement 2707 on the wrong way around and then lost my temper removing it, taking all the dummy pads with it. 

 In short, 3x1k in I/V work fine, with no distortion.


----------



## Magsy

I bumped up the TDA up to 8v and it sounds quite good there, I also increase the stepup to 10v to allow for my less than 'low' dropout regulator.

 Is there an easy place to tap in and provide external power? I think if I could cut +ve after RLED (on schematic) so usb powers HOST and the rest is supplied by external, it would work. I want it to be switchable though...like the Guzzler DAC.

 Easiest is just to pull +ve from the usb cable, but I'm not sure the device will work if I leave that float and provide +5v there?


----------



## dsavitsk

Quote:


  Originally Posted by *Magsy* /img/forum/go_quote.gif 
_Is there an easy place to tap in and provide external power?_

 

You are entering into uncharted water here. If you look at the botom of the board (http://www.ecp.cc/images/HPDAC_0.1b_bot.GIF) the power pin from the usb connector has 3 spokes. One goes to the reg101 regulator, one goes to the host pin, and the third goes to the dc-dc converter and the led. Presumably, it is this third one that you would want to cut and replace.

 As for places to apply power, one option is that there is a via right before the dc-dc converter, but this would not bypass the converter, which I think is a source of more noise than the usb supply itself. 

 Another option might be to not populate the dc-dc converter section (and not cut any traces) and apply external power to the output pins of VR1 and VR2. This would keep the LED powered by the usb supply. If you only wanted to apply power to one spot only, it could be to the via next to the "2" in "L2". So long as you jumpered D1 this would power both the amp and DAC chip.

 All of this stil leaves the PCM powered via USB, but I don't see an easy way around that.

 -d


----------



## Skubasteve

I'm using a PCM2706 in internally-regulated mode. I did not populate C7, C8, C21, L6, and L10. Based on a review of the PCM datasheet, it looks like the PSEL pin should be LOW to trigger the internally-regulated mode. Is this correct? Should I remove L9 (or jumper it) to set the pin low?

 Also, I'm wondering why the SSPND pin receives voltage; since it's an output, shouldn't it be left to float?


----------



## dsavitsk

Quote:


  Originally Posted by *Skubasteve* /img/forum/go_quote.gif 
_I'm using a PCM2706 in internally-regulated mode. I did not populate C7, C8, C21, L6, and L10. Based on a review of the PCM datasheet, it looks like the PSEL pin should be LOW to trigger the internally-regulated mode. Is this correct? Should I remove L9 (or jumper it) to set the pin low?_

 

Jumpering it is the same is populating it. L9 presents a high impedance to high frequency noise, but a low resistance to DC.

 Anyhow, you need PSEL high to tell it to be in buss powered operation.

  Quote:


  Originally Posted by *Skubasteve* /img/forum/go_quote.gif 
_Also, I'm wondering why the SSPND pin receives voltage; since it's an output, shouldn't it be left to float?_

 

It is a (inconsequential it seems) bug. There is a note about it on the website which says:
  Quote:


 There appears to be a small bug in the schematic and hence in the board. To date, there have been no reports of problems being caused by it, but if you are concerned, it is an easy fix. Pin 11 (SSPND) on the PCM2707 is powered while it should not be (it actually provides voltage to turn on some DAC chips.) To disable this, you can either cut the small trace that connects pin 10 to pin 11 (it is right between the two pads -- this is most easily done before the board is built) or, once assembled, use an X-acto knife to cut pin 11 off of the chip.


----------



## Skubasteve

Thanks dsavitsk!

 Another noob question: I plan on adding VR3 at some point; would I then want to ground PSEL to get the chip to run in self-powered mode? Or does the voltage at VBUS take care of this?


----------



## dsavitsk

Quote:


  Originally Posted by *Skubasteve* /img/forum/go_quote.gif 
_Thanks dsavitsk!

 Another noob question: I plan on adding VR3 at some point; would I then want to ground PSEL to get the chip to run in self-powered mode? Or does the voltage at VBUS take care of this?_

 

TI's terminology here is a little confusing. Self powered is as opposed to bus powered. The hpdac is always bus powered, meaning powered off of the USB supply. Self powered would mean that you built a stand alone power supply (batteries or AC.) So, psel should always be high.


----------



## Skubasteve

dup


----------



## Skubasteve

dup


----------

