Unless the stage after the DAC has very high input impedance (100k or more) you would need to use large coupling caps. With V-Caps, it will cost you a small fortune ($300 or so).
One solution is to use high impedance buffer and 0.1uF caps. A Borberly simple buffer (5 components or so) would be suggested here as it can be build with high impedance input.
As to V-Caps and the overall improvement, it is rather subtle. The V-Caps don't work well with Rikens, you need to switch to Caddocks TF020 ($6 ea). Even then, the improvement is some 10% or so: sound is a bit more transparent and detailed, but you loose some musicality as well.
One solution is to use high impedance buffer and 0.1uF caps. A Borberly simple buffer (5 components or so) would be suggested here as it can be build with high impedance input.
As to V-Caps and the overall improvement, it is rather subtle. The V-Caps don't work well with Rikens, you need to switch to Caddocks TF020 ($6 ea). Even then, the improvement is some 10% or so: sound is a bit more transparent and detailed, but you loose some musicality as well.
Hi,
I'd like to put together a 3875 kit, but will need to add a pot for volume control. Searching seemed to indicate a 10k lin is a good value.
I can get a basic Vishay for about £5 /$10, an Alps Blue for about £10 / $20, I also read on an old post that you have some Noble pots.
Are these still available, and will it give much improvement over the Alps?
thanks
Mark
I'd like to put together a 3875 kit, but will need to add a pot for volume control. Searching seemed to indicate a 10k lin is a good value.
I can get a basic Vishay for about £5 /$10, an Alps Blue for about £10 / $20, I also read on an old post that you have some Noble pots.
Are these still available, and will it give much improvement over the Alps?
thanks
Mark
Thanks for the reply Peter, how much are the 50k's. I don't know if Nobles are still made but I saw one over here for about £40 /$80.
It seems odd to spend as much on the pot as the kit.
Do you have any advice on hook up cable, solid cores seem very poular, even network cables. Is there much that can go wrong sonically with stranded, or is it more a case of finding a flavour you like.
Markus
It seems odd to spend as much on the pot as the kit.
Do you have any advice on hook up cable, solid cores seem very poular, even network cables. Is there much that can go wrong sonically with stranded, or is it more a case of finding a flavour you like.
Markus
USB DAC
Hi Peter,
I'm just getting around to building my USB DACs, and hit a small problem. When I powered up the first one, C3 heated up to the point that it started swelling, and of course the DAC was not working.
I've checked all the component values, polarities (especially C1 and C3) , and pin orientations, and cannot find anything wrong.
I've removed C3, and in addition to being visibly swollen, it does not measure consistently in value.
I have 10Vac out from both legs of the transformer, and the following voltages at the input to the DAC:
R1-R2: 12.5Vdc in, 10.2Vdc out.
R3-R4: 9.2Vdc in, 6.2Vdc out (with C3 removed).
I doubt that C3 was defective before....any suggestions of where to look further before replacing C3?
Thanks,
Robert
Hi Peter,
I'm just getting around to building my USB DACs, and hit a small problem. When I powered up the first one, C3 heated up to the point that it started swelling, and of course the DAC was not working.
I've checked all the component values, polarities (especially C1 and C3) , and pin orientations, and cannot find anything wrong.
I've removed C3, and in addition to being visibly swollen, it does not measure consistently in value.
I have 10Vac out from both legs of the transformer, and the following voltages at the input to the DAC:
R1-R2: 12.5Vdc in, 10.2Vdc out.
R3-R4: 9.2Vdc in, 6.2Vdc out (with C3 removed).
I doubt that C3 was defective before....any suggestions of where to look further before replacing C3?
Thanks,
Robert
Banned
Joined 2002
But C3 definitely heated up!
Re: USB DAC
Here a couple of photos just in case anyone can spot anything out of place:rjkdivin said:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
All Good
Okay....I re-installed the diodes in the correct orientation, and pirated another C3 from my next kit.....listening to Pink Floyd right now from the DAC to a Mini3 to some Sennheisers.....sounds awsome! Very good response at both ends. I did use Caddock TF020s and 2.2uf film capacitors at the outputs because I had tried that on the NOS DAC, and found I liked the high end better.
There doesn't seem to be any permanent damage to anything except C3, but is there anything else I should check?
Peter, I could use another C3....just tell me how much to PayPal you if you have any extras.
Thanks
Robert
Okay....I re-installed the diodes in the correct orientation, and pirated another C3 from my next kit.....listening to Pink Floyd right now from the DAC to a Mini3 to some Sennheisers.....sounds awsome! Very good response at both ends. I did use Caddock TF020s and 2.2uf film capacitors at the outputs because I had tried that on the NOS DAC, and found I liked the high end better.
There doesn't seem to be any permanent damage to anything except C3, but is there anything else I should check?
Peter, I could use another C3....just tell me how much to PayPal you if you have any extras.
Thanks
Robert
2nd One
I just finished up my second USB DAC PCB, and it works perfectly. I also realized I had replaced R8 & R9 Rikens with Caddock TF020s instead of R7 and R9. So I got those three resistors all sorted out on both boards....they sound even better now....a little smoother. To fit the Caddock at R7 without having it protrude on the bottom of the board, I swapped board sides with R8 and R7.
R7 and R9 are the correct ones to replace....correct Peter? I noticed you added the Caddock-spaced thru hole pads at R8 and R9, but not R7, and it threw me off a little.
I'm planning to build two more boards without the PSU section, or at least without the inlet and transformer, and put them into the cases I built for my two NOS DACs, sharing one PSU switched between the two DACs in each case.
It looks like the PCB cut could be made to feed the second board from the first transformer secondary (so the PSU diodes, caps and inductors would be duplicated); or you could cut it right behind the inductors and make the connection at R1,2,3,4 (so none of the PSU would be duplicated). To switch the PSU between the two boards would require a 4PDT switch? Any suggestions?
Peter I've also emailed you directly regarding buying another C3 to replace the one I toasted when my rectifiers were reversed.
I just finished up my second USB DAC PCB, and it works perfectly. I also realized I had replaced R8 & R9 Rikens with Caddock TF020s instead of R7 and R9. So I got those three resistors all sorted out on both boards....they sound even better now....a little smoother. To fit the Caddock at R7 without having it protrude on the bottom of the board, I swapped board sides with R8 and R7.
R7 and R9 are the correct ones to replace....correct Peter? I noticed you added the Caddock-spaced thru hole pads at R8 and R9, but not R7, and it threw me off a little.
I'm planning to build two more boards without the PSU section, or at least without the inlet and transformer, and put them into the cases I built for my two NOS DACs, sharing one PSU switched between the two DACs in each case.
It looks like the PCB cut could be made to feed the second board from the first transformer secondary (so the PSU diodes, caps and inductors would be duplicated); or you could cut it right behind the inductors and make the connection at R1,2,3,4 (so none of the PSU would be duplicated). To switch the PSU between the two boards would require a 4PDT switch? Any suggestions?
Peter I've also emailed you directly regarding buying another C3 to replace the one I toasted when my rectifiers were reversed.
Re: All Good
Sorry for late reply, but I was away. No problem with another C3, however, you might consider that such "cooked" capacitors may actually sound better
http://www.goodsoundclub.com/GetPost.aspx?PostID=5032&Phrase=cooked
rjkdivin said:
Sorry for late reply, but I was away. No problem with another C3, however, you might consider that such "cooked" capacitors may actually sound better
http://www.goodsoundclub.com/GetPost.aspx?PostID=5032&Phrase=cooked
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