[dsavitsk]

Quote:

Originally Posted by individual6891 That sounds a bit strange, are you sure the pins under the PCM chip haven't come loose and shorted pins?

I'm sure of nothing

Quote:

Originally Posted by individual6891 Have you checked the regulated outputs to be +5V and +3.3V?

I've got 5.01V at one point and about 8.1V at the other. Straight across the batt tabs (from the USB) is 4.83V. I actually think that there is a short in the USB jack, as I have to jam the cable in pretty hard to get it to connect. Of course, since I epoxy'd the jack to the board, I may never know for sure.

My other rev-a board and my beta board work fine.

-d

 

[dsavitsk]

USB DAC built to match Grado RA-1

-d

 

[iampivot]

I am trying to source the exact black gate caps and sanyo caps. The hificollective website doesn't have the Nx type, only the N type, and I've been unsuccessfull sourcing the sanyo OS-CON caps. Any links to sites in the UK that has them?

Second, the website http://www.mellowparenting.demon.co....er/usbdac.html doesn't load pictures properly in other browsers than IE, because the img url's use \ instead of / for path separators.

I tried mailing Guzzler about it, but got no reply. I also think I remember seeing a different version of this website some time ago, with more information about each particular revision. Does anyone know any other website with more details on this DAC?

 

[shiggins]

iampivot,

You can get the oscons from rapid electronics, 11-2522. 75p each. They're also doing free delivery this weekend and no minimum order. Nice. I didn't use black gates, instead got Nitais, also from rapid electronics. No idea on their relative quality, but dirt cheap and will get you going until you find black gates.

BTW, Guzzlers pics load fine for me using Opera.

 

[guzzler]

iampivot, I thought I sent a reply to you?

It should work fine in Internet Explorer if you have such a thing. Sorry about that

Anyways, I'm in the middle of two things at the moment

1) Exams

2) I'm almost completely out of DACs, so I'm going to be working on a new board over the next couple of months.

Scheduled changes are:

a) including low voltage opamps and space for a 3.5mm jack for use as a proper portable source for travellers, and for people who want some more filtering for line stages. Current capabilities will, of course, be retained

b) getting rid of the MAX1722 for something more easily available, or looking into buying small quantities

c) Making the board a different shape (ie, square) with holes in each corner for easier mounting (possibly make it fit the Hammond 1455, maybe, they're a bit common!)

d) making the socket stick out for easier panel mounting

I'm not going to say much more about it at the minute, as I've really not got a bean of time just now, but I'll start on it the start of July and post some updates

g

 

[bg4533]

Guzzler,
The pics work in Internet Explorer. They do not work in other browsers (Firefox for me).

 

[jerb]

I dont suppose there are any unused kits still floating around?

 

[awagner]

Just thought I'd chime in and express my interest in this project. If there are any of the previous versions of the kit available, I'd like to purchase one or two, and I'd also like to be a tester for the new version.

Since you seem to be reconsidering the form factor for the next revision, I think it might be cool to consider making the design expandable with daughter-cards for power supplies, headphone amplification and crossfeed, etc.

So for non-portable use one could take something like per-anders' QRV07 design...

http://home.swipnet.se/~w-50719/hifi/qrv07/index.html

chop it in half, flip the power supply half upside down and mount it under the amp portion, put the USB dac on top of these (3 cards total)

For portable use, a NiMH battery board and maybe a board with a MINT amp with (jumpered, optional) crossfeed, and the USB DAC on top (again, 3 cards total)

I'm not suggesting you should necessarily design all of these boards, but it might not be hard to make provisions for others to do so by choice of connector placement and jumpers for things like internal vs. external power, internal vs. external volume pot, availability of cases of varying heights for the width you choose, etc.

Thanks!
Drew

 

[Dr_Skoobie]

Hello all,

I recently got my kit constructed, but am encountering problems. I'm using the dac in conjunction with tangent's "tread" power supply.

As I can get a nice clean 5vdc from the tread, I have power running into the +5v (formerly +alt) pad, bypassing IC2.

Like another poster, however, I'm getting closer to 1.5v from IC3, not the desired 3.3v.

Guzzler's site still refers to grounding a bypass PS with Vs = 5v to the right pad of R1-- which I did initially. I discovered after examining the layout that ground connects to the left pad (verified by testing continuity with the USB connector and DAC chip grounds), duh. Could I have damaged the regulators by having ground attached to the right hand pad of R1 when I powered up the first several times?

I am also complicating my troubleshooting somewhat by having IC2 connected, as I soldered the SMDs before knowing what PS approach I would take. I did omit the LCR and C1-4 as suggested, but figured that having IC2 installed would be harmless as the +5v pad bypasses it-- am I mistaken?

Any help in troubleshooting and determining next steps is welcome.

thanks!

dr_s

 

[guzzler]

Which version of the board are you using? If it's a Revision A board, there won't be a pad to the right of R1, except one marked >5V, so I'm not entirely sure where you've put the ground. Is there any chance of a picture (or even annotate the layout from the webpage) of where you put things? IC2 shouldn't have any impact on it as the input trace for it doesn't go anywhere if you've left out the switching supply parts. Really, I'm a little confused as to where you've put the ground, but after that we'll take a look

g

PS; regards website, I know what's happened there... I updated it over the easter holidays using the old version from home, and the changes were on the copy I've got here at uni so that's why thats changed. It'll be a couple of weeks until I can change that back

 

[Dr_Skoobie]

Hi Guzzler,

It is the revision A board. There is no through hole, I was using the actual right hand solder pad for R1 (which is omitted in this case) for my ground connection.

When I moved it to the left hand side, I chose the negative/ground through hole for C17 (which connects to the left hand solder pad of R1). As I don't need the L-C-R filter, this seemed convenient.

I assume this is correct... kind of disappointed to hear that removing IC2 won't fix my problem, no silver bullet!

With regard to the tread, I verified that the PS is putting out 5vdc relative to its own ground. Measuring from the +5v pad to the revA board ground, however, I get only 1.6vdc. I don't know if this is a symptom of a problem with my construction of the DAC, or a sign that I simply need to increase the voltage output from the tread, considering the load presented by the DAC circuit. I thought I would seek counsel here first so as to avoid damaging anything by guessing.

thanks!

-dr_s

 

[guzzler]

You could try removing IC2, but it shouldn't do anything. You connected it backwards when you had ground to >5V, but now that you've disconnected that, that trace doesn't go anywhere so it's not like the IC is shorting to ground or anything. The TREAD is more than enough to supply the DAC. First of all, check you're soldering around the main chip with a magnifying glass. It does sound like a short to ground somewhere. Also, it might be a good idea to measure your current draw as this would confirm the problem. Let us know how you get on

g

 

[danko]

Hello guys!


Have anyone tried this PCM2702 DAC to work under linux?
If it works good, then I think, it's time for upgrade my soundcard

)

guzzler, can you send me the EAGLE file-s of the board?

thanks in advance: Danko

 

[dsavitsk]

Quote:

Originally Posted by danko Have anyone tried this PCM2702 DAC to work under linux?

It should work fine.

 

[danko]

thanks! I have found on www.linux-usb.org, that this chip works perfectly under linux. So, it's time to upgrade my soundcard