I have a DAC7 (V1.0) ( SDAC 100 v1.0) with a white board.
I lost the opamps that came with it ( 2 years ago !). What are the opamps that one can use. I was told the two presets on the board should be set to give +/- 15 V at the opamp supply pins. Apparently all three opamps are dual opamps.
I don't have the USB adapter board.
Same board as seen here: http://gd4.alicdn.com/imgextra/i4/88221699/T2xPd4XjxcXXXXXXXX_!!88221699.jpg
Thanks.
I lost the opamps that came with it ( 2 years ago !). What are the opamps that one can use. I was told the two presets on the board should be set to give +/- 15 V at the opamp supply pins. Apparently all three opamps are dual opamps.
I don't have the USB adapter board.
Same board as seen here: http://gd4.alicdn.com/imgextra/i4/88221699/T2xPd4XjxcXXXXXXXX_!!88221699.jpg
Thanks.
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The "usual" upgrade for the tl072 when a jfet input is needed is the opa2134. It looks like the output stage is a classical balanced to unbalanced converter and jfet inputs aren't required. If the dac output stage uses lowish values resistors (as often seen in datasheet to keep noise low), opamps made to drive 600R, such as the lm4562, should be better than the tl072; those are really awful driving low impedance loads.
Slow is better, I've had that fast moving electricity get the best of me on several occasions.
The circuit is based on an Arcam design, and those came with AD797, and OP2134 FWIW.
I have a similar one and it came with NE5532, and TL072 as delivered from Weiliang.
And I believe the supplies are closer to 12V also.
The circuit is based on an Arcam design, and those came with AD797, and OP2134 FWIW.
I have a similar one and it came with NE5532, and TL072 as delivered from Weiliang.
And I believe the supplies are closer to 12V also.
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I bumped my voltage up to 14v for my op amps, by the way...
Had some opa627 biased a bit along with lme49720 on the servo, and worked great, then I found some discrete op amps.
It may also help to run a jumper from the power pins of the op amps to the 47uf capacitor that feeds it, made a big difference with the discrete modules anyways.
Had some opa627 biased a bit along with lme49720 on the servo, and worked great, then I found some discrete op amps.
It may also help to run a jumper from the power pins of the op amps to the 47uf capacitor that feeds it, made a big difference with the discrete modules anyways.
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Well, the DAC7 received the TL072's and NE5534.
I must say I never expected it to sound the way it did. It IS good even with the TL072's ! But on complex sounds it's a bit noisy to my ears. So after an hour or two I searched for the OPA2134 and found them. Put that in. It became much smoother. Bass is well defined and deep and HF is very good. On very good recordings the HF sounds great. So far I didn't hear any vocals that didn't sound nice. Very nice.
BUT there is a spanner in the works ! If you stop and start a cd or pause and start a song or skip songs you get a sharp hiss/crackle from the speakers.Sometimes short but sometimes a bit long. Destroys the start of a song ! What is it due to ? Junk going to the DAC during those periods?
Is mute an effective solution ? A relay is slower. But will that do without truncating the start of a track ? By the way if I play the disc continuously there is no noise when tracks change.
It's terrible if you need to stop and start or pause or skip tracks.
But otherwise I like the sound. Some aspects are nicer than my OPPO93 !
Now I need to see how I can fix the noise problem. After that more opamps to compare !
However I'm happy I bought it ! I trust the new versions must have fixed the noise problem ? Like the V1.2 or higher ( mine being V1.0).
The heat sinks run quite hot ! Wonder how hot that would get in a closed box ! Will check it out in Jan !
I will record the section where I get noise like skipping tracks etc. Then will look at it on an editor and see if the noise actually stops before playback starts or if it merges even a little bit bit as the track starts. If it does, that would be a disaster ! I hope it doesn't. I like the DAC !
I must say I never expected it to sound the way it did. It IS good even with the TL072's ! But on complex sounds it's a bit noisy to my ears. So after an hour or two I searched for the OPA2134 and found them. Put that in. It became much smoother. Bass is well defined and deep and HF is very good. On very good recordings the HF sounds great. So far I didn't hear any vocals that didn't sound nice. Very nice.
BUT there is a spanner in the works ! If you stop and start a cd or pause and start a song or skip songs you get a sharp hiss/crackle from the speakers.Sometimes short but sometimes a bit long. Destroys the start of a song ! What is it due to ? Junk going to the DAC during those periods?
Is mute an effective solution ? A relay is slower. But will that do without truncating the start of a track ? By the way if I play the disc continuously there is no noise when tracks change.
It's terrible if you need to stop and start or pause or skip tracks.
But otherwise I like the sound. Some aspects are nicer than my OPPO93 !
Now I need to see how I can fix the noise problem. After that more opamps to compare !
However I'm happy I bought it ! I trust the new versions must have fixed the noise problem ? Like the V1.2 or higher ( mine being V1.0).
The heat sinks run quite hot ! Wonder how hot that would get in a closed box ! Will check it out in Jan !
I will record the section where I get noise like skipping tracks etc. Then will look at it on an editor and see if the noise actually stops before playback starts or if it merges even a little bit bit as the track starts. If it does, that would be a disaster ! I hope it doesn't. I like the DAC !
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Not sure what a solution would be for the noise problem. Your correct as to the causes though. Normally a CD player has all the logic integrated into the system control to take care of this. I suspect the DAC "firmware" doesn't do the necessary when it detects a pause or break in the data stream.
If I use my Sony MiniDisc recorder as a DAC there is no problem when this kind of thing happens or the signal disappears... it just silently mutes.
I've no answer I'm afraid.
If I use my Sony MiniDisc recorder as a DAC there is no problem when this kind of thing happens or the signal disappears... it just silently mutes.
I've no answer I'm afraid.
The Wolfsen WM8741 DAC chip has a pin for mute. Pin 25 which according to the circuit diagram that I got, is unconnected.
I looked carefully at the LED on the board which I think shows the presence of a digital signal. It flickers very briefly when the noise comes. It is normally on when connected to the player.
Sometimes I wonder if something in the player is aggravating this issue. I'll change the player and try it. However I may not be able to do it as I am leaving in 24 hours for my holiday. Note that it doesn't happen 'always' when you switch a track or stop/start a track.
I put back my DAC9 ( AK4399) to compare the sound. Hard to make a comparison right now. Both are good. Surprisingly the DAC9 also has the same noise problem though it occurs much less often than the DAC7. That's why I want to change the disc player. However the eBay sellers page does mention that DAC7 can have switching noise when changing tracks ! The DAC9 sellers page doesn't mention it.
My current player is an OPPO93. I will use a Marantz CD67-II or a Marantz-CD-17 to confirm that the player does not aggravate the problem. All that after 5th Jan.
Happy New Year to all !
I looked carefully at the LED on the board which I think shows the presence of a digital signal. It flickers very briefly when the noise comes. It is normally on when connected to the player.
Sometimes I wonder if something in the player is aggravating this issue. I'll change the player and try it. However I may not be able to do it as I am leaving in 24 hours for my holiday. Note that it doesn't happen 'always' when you switch a track or stop/start a track.
I put back my DAC9 ( AK4399) to compare the sound. Hard to make a comparison right now. Both are good. Surprisingly the DAC9 also has the same noise problem though it occurs much less often than the DAC7. That's why I want to change the disc player. However the eBay sellers page does mention that DAC7 can have switching noise when changing tracks ! The DAC9 sellers page doesn't mention it.
My current player is an OPPO93. I will use a Marantz CD67-II or a Marantz-CD-17 to confirm that the player does not aggravate the problem. All that after 5th Jan.
Happy New Year to all !
The question is , is it just because they have not implemented any muting at all. They haven't, you can easily see it from the board. The mute pin is also unused. So if I implement a mute will it work well ? Use transistors ( like most CD players) or a miniature relay ? Most guys remove the transistors used for muting claiming they degrade the sound. That way the player does have switching noise but I don't know if they are similar to what I hear now.
Needs 'time' to find out and I don't have that now.
Needs 'time' to find out and I don't have that now.
Hmmm... I wouldn't like to say. Perhaps try transistors first and see if it works... in fact just use an LED and see if the mute line would be active when needed before rigging anything up.
Transistors if used correctly (and the correct devices) are fine. If the switching levels permit then use FET's.
Transistors if used correctly (and the correct devices) are fine. If the switching levels permit then use FET's.
You are right. I must test the mute pin to see if it works at all ! Then I could scope it while playing music and see if it does work during the period that's required. I have a digital scope that can store the trace.
Pity I have no time now. I will get back on this when I return.
DAC 9 has been playing in the background and it is really nice. But I want to make a level calibrated comparison with the OPPO93.
Pity I have no time now. I will get back on this when I return.
DAC 9 has been playing in the background and it is really nice. But I want to make a level calibrated comparison with the OPPO93.
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