I can't help with the opamp problems, I never used the circuit. Could there be an oscillation problem in using some of these opamps in a low gain configuration? I've seen that in the past.
An Idea - perhaps!
This thread does seem to be a great success. It has only one problem that I can see - one which is common to many other threads.
As time progresses more and more of these DACs are sold and a lot of new posters looking for advice on how best to use their new DAC post questions - which have often been answered many times in earlier threads. To expect anyone to read through almost 2,000 posts is not reasonable. There are eight or ten members who have the patience of Saints by repeatedly answering what is effectively the same question.
The point of this post is to see if anyone believes that a sticky or a Wiki giving the basics for the following - or similar - headings:
a) transformer output conversions
b) power supply basics
c) opamp options
d) onboard modifications
e) computer outboard use
would this be be a good idea?
I had a simple need which was to add a pair of UCT- 20 transformers. I got excellent advice and have a result which answers all of my needs for CD replay. Thank you all - and especially those who are the stalwart advice givers such as Bill Fuss - for making life so easy on this front.🙂
This thread does seem to be a great success. It has only one problem that I can see - one which is common to many other threads.
As time progresses more and more of these DACs are sold and a lot of new posters looking for advice on how best to use their new DAC post questions - which have often been answered many times in earlier threads. To expect anyone to read through almost 2,000 posts is not reasonable. There are eight or ten members who have the patience of Saints by repeatedly answering what is effectively the same question.
The point of this post is to see if anyone believes that a sticky or a Wiki giving the basics for the following - or similar - headings:
a) transformer output conversions
b) power supply basics
c) opamp options
d) onboard modifications
e) computer outboard use
would this be be a good idea?
I had a simple need which was to add a pair of UCT- 20 transformers. I got excellent advice and have a result which answers all of my needs for CD replay. Thank you all - and especially those who are the stalwart advice givers such as Bill Fuss - for making life so easy on this front.🙂
hi brianco,
this is a very good idea. maybe its time to make something like a small tutorial about this dac and the improvements that can be made. i build my dac some days ago and when i was planing it i had to ask a lot of questions, from which maybe 50-60% havalready been answered before.
but this is a basic problem of threads that are as big as this one. i think the most simple way would be to edit the first post and to link the most important posts.
greetings,
chris
this is a very good idea. maybe its time to make something like a small tutorial about this dac and the improvements that can be made. i build my dac some days ago and when i was planing it i had to ask a lot of questions, from which maybe 50-60% havalready been answered before.
but this is a basic problem of threads that are as big as this one. i think the most simple way would be to edit the first post and to link the most important posts.
greetings,
chris
I support this. I recently re-read the thread to pick up any earlier mods I might have overlooked/forgotten. It was quite a slog. I was yearning for an index!
To build on brianco's initial suggestion, I suggest a re-order of headings based on following the signal path. This could help keep the guide structured as it grows and might help newbie's understanding;
1 - power supply basics
2 - computer outboard use
3 - digital input stage
4 - onboard modifications
5 - analogue output stage
5.1 - transformer output conversions
5.2 - opamp options
To build on brianco's initial suggestion, I suggest a re-order of headings based on following the signal path. This could help keep the guide structured as it grows and might help newbie's understanding;
1 - power supply basics
2 - computer outboard use
3 - digital input stage
4 - onboard modifications
5 - analogue output stage
5.1 - transformer output conversions
5.2 - opamp options
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pcm1798: follow-up
I emailed the seller on eBay and a pcm1798 module is available for 25 $ (shipping included). I think I'm going to try it. Obviously my A-20s with 1:1 ratio will not work for that. Maybe a pair of Lundahl LL1674? I will check for other transformers...
I emailed the seller on eBay and a pcm1798 module is available for 25 $ (shipping included). I think I'm going to try it. Obviously my A-20s with 1:1 ratio will not work for that. Maybe a pair of Lundahl LL1674? I will check for other transformers...
That's right. The newer board has some VDC on this pin instead of being to the ground.
This mod was recommended only for the CS4398 dac.
Are the cs4398 and pcm1798 pincompatible?
Why wouldn´t the A-20 work with the pcm1798?
Don't forget apart from transformer output 5.3 should be tube output conversions...
The CS4398 and the PCM1798 don't have the same pinout, that's why there is an adaptor with additional parts to fit into the DA converter board. In that case I think you can use the UTCs A-20. But the idea is to steal the PCM1798 outputs directly. Since it's a current DAC, transformers with higher gain are necessary, like the Sowters McGyver has.
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Has anybody done this yet? It would be nice to have a step by step with pics for this. One more item to add to the wiki.
Trafos for current out chips are around 18-20/1 ratio, like MC phono trafos. I haven't tried it yet but many have. It's quite a different procedure from what we have been doing with the voltage out chips. They also are generally pretty expensive but what the hell.
The WIKI sounds like a great idea.
Another option not listed for output is active discrete buffering for the CS4398 types.
The WIKI sounds like a great idea.
Another option not listed for output is active discrete buffering for the CS4398 types.
Wiki
I have been playing with a more complete framework for a wiki. This is attached as text file (as I did not want to hog the thread pages for those who ain't interested).
I have no idea how or where to set this kind of thing up, but am keen to help and to contribute content as I have had so much help from some of you lot.
I have been playing with a more complete framework for a wiki. This is attached as text file (as I did not want to hog the thread pages for those who ain't interested).
I have no idea how or where to set this kind of thing up, but am keen to help and to contribute content as I have had so much help from some of you lot.
Hoverdonkey- you can get a free wiki site from here:
PBworks: PBworks Online Collaboration
Will need some setting up. I havn't done this myself but will help if required.
Rich
PBworks: PBworks Online Collaboration
Will need some setting up. I havn't done this myself but will help if required.
Rich
pcm1798
I just ordered a pcm1798 module. Kevin from KKaudio suggested a LL1674 like they use in their RAKK dac : Passive output
However Per Lundahl is more evasive:
Almost any of our mu metal or amorphous metal transformers can be used forDAC output. Yes, LL1674 will do the job. It is however unhappy with any DCsignal unbalance.
Sowter get a range of transformers for DAC (like the 9545 of McGyver):SOWTER DAC I/V TRANSFORMERS
Still waiting for Jensen's answer. In the meantime, I will check if there is anything on eBay.
I just ordered a pcm1798 module. Kevin from KKaudio suggested a LL1674 like they use in their RAKK dac : Passive output
However Per Lundahl is more evasive:
Almost any of our mu metal or amorphous metal transformers can be used forDAC output. Yes, LL1674 will do the job. It is however unhappy with any DCsignal unbalance.
Sowter get a range of transformers for DAC (like the 9545 of McGyver):SOWTER DAC I/V TRANSFORMERS
Still waiting for Jensen's answer. In the meantime, I will check if there is anything on eBay.
An update to my crackling, scratchy-sounding right channel. I just received my LME49860 opamps from Digikey. Plugged them into the dac, and now no more crackling. I guess on my board the issue was bad opamps...
Got my DAC
Hi,
This thread inspired me to purchase one of these little DACs. It arrived a few days ago and I had time to hook it up tonight and do some quick measurements. I used ARTA combined with an M-Audio 2496 card, frequency response was measured using a 16bit 44.1kHz SPDIF output.
I see about -3dB dip at 10kHz which I seem to remember reading some earlier posts about this. I look forward to modding this!
Cheers
Chas
Hi,
This thread inspired me to purchase one of these little DACs. It arrived a few days ago and I had time to hook it up tonight and do some quick measurements. I used ARTA combined with an M-Audio 2496 card, frequency response was measured using a 16bit 44.1kHz SPDIF output.
I see about -3dB dip at 10kHz which I seem to remember reading some earlier posts about this. I look forward to modding this!
Cheers
Chas
Attachments
I wish you luck as I am all but totally illiterate regarding any form of setting up of computer stuff!! If you can get this to work it would be a valuable reference facility.🙂