I have reviewed the schematic, and it seems to me that the first line of attack should not be the opamps, but the power supply. Eg. rectifier diodes are as nasty as they come, and there should be great improvement to switch to soft recovery or schottky diodes (according to taste).
Next of course will be the power supply caps, and my current preference is Panasonic FM for analog sections, and Oscon for digital. The size of ps caps is interesting too. I'd generally have more generous sizes near the opamps.
Next of course will be the power supply caps, and my current preference is Panasonic FM for analog sections, and Oscon for digital. The size of ps caps is interesting too. I'd generally have more generous sizes near the opamps.
just ordered one!!...i plan on using onectic transfos for the output, but i would also like to keep the opamp out..so my question is, can i conect the transformers to the dac chip and also keep the opamp stage?...or should i lift the output to go only to the transfos?
i really like the idea of having a pair of outputs and compare...
i really like the idea of having a pair of outputs and compare...
Hi mekanoplastik,
Before you buy the trafo, I would like to suggest that you listen to the ad797 on all 6 IC sockets, You might like the sound.
I would imagine that , If you tap connect a trafo from the dac chips output so that you have 2 different rca outputs, The sound quality would suffer, As the trafo will become a parasitic sound quality sucker or downer ( for lack of a better word) to the ICs, And vice versa. Better it one or the other , And not both.
Before you buy the trafo, I would like to suggest that you listen to the ad797 on all 6 IC sockets, You might like the sound.
I would imagine that , If you tap connect a trafo from the dac chips output so that you have 2 different rca outputs, The sound quality would suffer, As the trafo will become a parasitic sound quality sucker or downer ( for lack of a better word) to the ICs, And vice versa. Better it one or the other , And not both.
I'm picking up the AD797BRZ for the I/V and LT1028ACN8 for the output within the next 2-3 weeks. I will report back vs the AD797ANZ and OPA604 I have in there right now. 🙂
yes erin, it was quite clearly directed at you
what?? its really pretty straight forward, I just said that although the bursons have quite low distortion, they are not lower than the opamps that you replaced with them, as even fairly generic type opamps like OPA134 have distortion orders of magnitude lower, as you seemed to be suggesting with the lower level detail retrieval.
I also went on to concede that i feel they can sound good in the right position, but that I did not believe they could replace quality instrumentation opamps in areas where offset drift are important and went on to explain that I did in fact have many of them and had tried them instead of the suggestion that because I made mention of the evil numbers and chose to use something else that I must not have done so.
I started by saying they can sound quite good, but that if numbers meant anything to you, then perhaps they arent the right part for the job and in that case...they arent....if it doesnt mean anything to you..then why does it matter?
I fail to see where the ego lies just because I said that if I felt like going with a discrete circuit, I would build a discrete circuit that was able to be tuned to my taste. I said nothing about designing my own circuits, in fact I clearly mentioned and named OTHER PEOPLES designs in the same sentence
I maintain that they are still a good drop in replacement for those who are either not willing, or unable to do such a thing and want some flavor, but that they cannot just replace any opamp and do a better job. they do a better job of 2nd order distortion and harmonics, which can be quite pleasing to the ear and yes even my ears, audio performance is quite good
I got frustrated with being argued with when I was making efforts to present a rounded opinion, when someone just picks a negative out of such a post for the sake of argument it bugs the hell out of me
and in fact you said
erin said:
and Paul, i'm sorry but it seems you are the one being personal here, erin is a big boy and even if I was picking a fight and believe me you would know if I was, rather than just being frustrated, then i'm sure he can look after himself, instead of needing some 'me too' type back up from you, then going on to make up your own version of what I said.
i'm happy to just drop it, i've said what I needed to say and hopefully people will read it in its entirety, instead of picking bits to argue with.
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just for example as well and this is an honest to god recommendation for those who are willing to give it a try, this dac has 4 voltage out dacs in parallel, you do not need any gain here, a simple jfet follower would suffice and sound great. parts count and cost would be very low and effort to find a circuit low also
/rant, back to your scheduled program
/rant, back to your scheduled program
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i already have the transfos, i had used them with a single wm8740 dac from the same seller and it was nice, so i really want to try with 4 chips.
maybe i can use jumpers, or a switch......once i have the dac on hand i will figure out how to have both outputs available, i hope traces are fat and easy to "highjack"
Thanks to all have replied to this thread. I will be using 797, hexfreds, Nichicon OSCONS, Panasonic Electrolytics, surplus Russian Polystyrenes and Visahy naked resistors in the signal path. I suspect I may also replace the Digital isolation transformer. We shall see how it stacks up to my Muse Model 2, still my reference after all these years. Thanks again for all the help and the testing.
DAC received
Just received DAC today. Very quick service. I am impressed! Stock it sounds very very good. I am using it in a desktop system with a Rotel amp and Orb speakers. Just a hint of digititus, but massed choruses now sound like choruses not grundge. I was blaming my four year old Dell cheapie for my problems, but I now think the DACs I was using are to blame for much of the problem. I am waiting on parts to begin modification. I think with some superior parts this can be a real winner. It already is in so many ways, but I agree with John Curl, you can never use less than the best parts and expect the best results. We are lucky to have a man of such talent and discernment as a member of the forum. I had one of his Vendetta crossovers and now wish I had never sold it. He is a genuis and a font of informed wisdom. We should all listen to him more closely. Thanks for all the the advice on improving this device. I have taken them all to heart. I would like Mr. Curl to take a look at the circuit and make any suggestions he might have. Thanks again to all who have contributed.
Just received DAC today. Very quick service. I am impressed! Stock it sounds very very good. I am using it in a desktop system with a Rotel amp and Orb speakers. Just a hint of digititus, but massed choruses now sound like choruses not grundge. I was blaming my four year old Dell cheapie for my problems, but I now think the DACs I was using are to blame for much of the problem. I am waiting on parts to begin modification. I think with some superior parts this can be a real winner. It already is in so many ways, but I agree with John Curl, you can never use less than the best parts and expect the best results. We are lucky to have a man of such talent and discernment as a member of the forum. I had one of his Vendetta crossovers and now wish I had never sold it. He is a genuis and a font of informed wisdom. We should all listen to him more closely. Thanks for all the the advice on improving this device. I have taken them all to heart. I would like Mr. Curl to take a look at the circuit and make any suggestions he might have. Thanks again to all who have contributed.
AD797AN
I've been following this tread with great interest and finally decided to purchase this DAC a few weeks ago. I also ordered four AD797AN opamps for the filter stage--I am planning to use balanced outputs thus leaving the output stage BBs in place. What happened is really surprising: after I placed ADs in IC sockets, there was no sound at first, and than smoke came out of an AD797. I placed the BBs OPA134 back and the sound came back. I then tried to replace two left channel opamps with the ADs and consequently lost the sound in the left channel; the right channel was playing fine. Does anyone know what happened here, and why there is no sound when AD797s replaced OPA134s. And, the AD797 that had smoke came out of it has a crack right in middle of the top face. It didn't smell good! The DAC is now playing fine with its four OPA134s back in place. Thanks in advance for any advice you can share.
I've been following this tread with great interest and finally decided to purchase this DAC a few weeks ago. I also ordered four AD797AN opamps for the filter stage--I am planning to use balanced outputs thus leaving the output stage BBs in place. What happened is really surprising: after I placed ADs in IC sockets, there was no sound at first, and than smoke came out of an AD797. I placed the BBs OPA134 back and the sound came back. I then tried to replace two left channel opamps with the ADs and consequently lost the sound in the left channel; the right channel was playing fine. Does anyone know what happened here, and why there is no sound when AD797s replaced OPA134s. And, the AD797 that had smoke came out of it has a crack right in middle of the top face. It didn't smell good! The DAC is now playing fine with its four OPA134s back in place. Thanks in advance for any advice you can share.
Replacing bypass caps on W8740s
I would like to replace the electrolytics with oscons. Has anyone done this? How difficult was it? Was there any improvement in SQ? thanks for the help.
I would like to replace the electrolytics with oscons. Has anyone done this? How difficult was it? Was there any improvement in SQ? thanks for the help.
i received mine, testing with 4 x ad8610 + 2 x opa627..... i will roll more opamps in the following weeks as i want to get used to this "reference" sound first.... but i like it so far.
Grand opening
I have now opened the DAC. No problems. Diodes and electrolytics are marked for polarity on the circuit board. I see no problems in replacing any of the above components. Solder wick and a controlled heat station should do it. I will also add some flux to the board to keep things cool. I will let you know how things progress.
I have now opened the DAC. No problems. Diodes and electrolytics are marked for polarity on the circuit board. I see no problems in replacing any of the above components. Solder wick and a controlled heat station should do it. I will also add some flux to the board to keep things cool. I will let you know how things progress.
The are Oscons and there are oscons 😀. If you look up older posts, Oscons would be referring to Sanyo Oscons, and the general opinion was that they helped in digital sections, but avoid them in analog sections. Back then Panasonic FCs were well regarded in terms of price/performance for power supply caps for the op-amps.
Moving on, Pana FMs have mostly got a good reception, but there is not much about the newer solid aluminum polymer (oscon) from United Chemi Con, Nippon Chemi Con and others. Spec-wise they are similar to Sanyo Oscons. The package is cool, like the smt caps on computer cards - silver + black or other dark band on negative side.
I still avoid Sanyo Oscons in analog sections.
Taking your advice
I Will be using 47uf25v Panasonic FMs in the analogue section and Nishicon 47uf 63v Oscons in the digital. I am replacing 47uf in all locations so that should not be a problem. I am concerned about the post dealing with AD797d burning up in this circuit while Marcel reported no problems.I may go with OPA627s just to be safe. Any advice?
I Will be using 47uf25v Panasonic FMs in the analogue section and Nishicon 47uf 63v Oscons in the digital. I am replacing 47uf in all locations so that should not be a problem. I am concerned about the post dealing with AD797d burning up in this circuit while Marcel reported no problems.I may go with OPA627s just to be safe. Any advice?
From what I remember, Marchel's OPA627 didn't work for him either. So either way, there is a risk...The AD797 are still going strong for me though.
You might want to wait till I roll the AD797BRZ to see if they are worth the added cost/trouble over the ANZ in this DAC. I am just waiting for the adapters to arrive.
I have just tried LT1028 ACN8 at the outputs. It's definitely a big improvement over the stock OPA604. I don't have an extra pair of AD797 to compare at the moment though, but I am so not going back to the 604 😛
the opa627 was fine for me, much better than the stock opamps
however, I have moved on from this DAC (that is another story)....
however, I have moved on from this DAC (that is another story)....
to mb3brooklyn
I can think of several reasons for your problem. !. The 797s were inserted backwards. 2. The 797s become unstable when driving the 134s. 3. They are "fake" 797s. 4. The circuit has been changed, I noticed that in my recent DAC, the 10uf decoupling caps have been replaced with 47uf. I do not know if this is a problem, but it is not what the schematic specifies. Other changes maye also have been made. Hope this helps. Kindest regards John Dozier
I can think of several reasons for your problem. !. The 797s were inserted backwards. 2. The 797s become unstable when driving the 134s. 3. They are "fake" 797s. 4. The circuit has been changed, I noticed that in my recent DAC, the 10uf decoupling caps have been replaced with 47uf. I do not know if this is a problem, but it is not what the schematic specifies. Other changes maye also have been made. Hope this helps. Kindest regards John Dozier
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