oh there could still be an issue with the 797, because I dont believe its a good match here, I just meant that the distortion cancellation pin is not the answer, perhaps compensation, but I recommend just sticking with what you have working, or perhaps try some other less tempermental chips that work comfortably at unity gain for the buffer section. OPA827, OPA1641, LME49990 (my current favorite), LT1028 (this ones a little tricky too)
Hi:
I check marchel attach schemeic,
If Yr circuit like his version pls check....
Output use AD797 Op to be a buffer but After check AD797spec. AD797-pin8 should be a CAP. connect to output.
This pin function should be connect output to feedback signal (do decompensatione. & distrotion ).
Maybe this is a reason cause some distortions at high frequences.
Btw AD797 spec. close LME49710 already.
ASter
Mr211's Blog - Yahoo!?????--
I don't know if it's just my luck, But I absolutely have no problems with 797 in my unit. There are no symptoms of trouble that I can detect, There is no distortion and no overheating IC.
There might be some differences in the parts used in my unit and yours or it could be that the preamp is distorting. You could try soldering some small value bypass caps under the opamp socket under the pcb, It might help, When you are using the AD797. BUt I didn't have any mods around the opamps on my unit, And There are no problems.
I also have the LME48710, Used it for a while , And then I returned to the ad797, For me the ad797 is more transparent sounding, I now paired the dac with a preamp that delivers full sounding bass, To compensate for the ad797 slightly dry sounding bass.
There might be some differences in the parts used in my unit and yours or it could be that the preamp is distorting. You could try soldering some small value bypass caps under the opamp socket under the pcb, It might help, When you are using the AD797. BUt I didn't have any mods around the opamps on my unit, And There are no problems.
I also have the LME48710, Used it for a while , And then I returned to the ad797, For me the ad797 is more transparent sounding, I now paired the dac with a preamp that delivers full sounding bass, To compensate for the ad797 slightly dry sounding bass.
Hi:
For me if just connect AD797 only I will feel signal too weak gain not string enough.
Yr still mount WM8740?
For more pretty sound response so I connect Tube buffer and Transformer output.
Could reference....
Toy1 My first time Audio DIY ... D/A.
Mr211's Blog
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Have you tried using ad797 on all six sockets, I'm using six ad797 on my unit, And I could say that this is the best sounding opamps I have ever heard, As transparent as a good transistorized opamps.
I haven't tried the opa627 though, The ones I tried were defective or fake and were returned to the seller.
Hi :
My D/A combination is WM8741+AD827AQ(dual OP)+AD797.
AD827AQ is a differential combiner.
Because WM8740~42 is a balance differential output (I-V about 2.2V).
ASter
http://tw.myblog.yahoo.com/jw!9frLFy6fAkV0gBy_oZT_geG5fC24WQ--
Hi:
Yes,I replace WM8740 with WM8741.
I had ever replace WM8741 and WM8742 but final I select WM8741.
AD827AQ is a differential combiner (have filter function same time) and connect WM8741 output.
AD797 is buffer stage.
ASter
Mr211's Blog - Yahoo!?????
Hi:
D/A is working under PWM feature.
So your D/A output should be a PWM carry frequency filter.
D/A working function block will like D/A+filter+buffer.
So yr Better connect OPT to OP buffer output.
Btw need take card Otp impedance must be matching.
Normal OP output close 600ohm so Your OTP first-pole must close 600ohm.
Pls take care what's stage your will connect to D/A output.
That's depend on OTP second pole impedence.
If connect to Tube Amplifier that's will be High impedence.
If connect to Transister Amplifier Impedence just 75ohm.
Aster
Mr211's Blog - Yahoo!?????
mm...so you are recomending to use what i have marked as point 3 in the schematic?.....i will try this weekend and report.
thank you.
Attachments
Hi:
Attach Modify circuit for your reference.
Connect U29-pin6 to OPT First pole.
Second pole Output tag OUT just connect output RCA connector.
OPT Two side Ground just connect D/A Ground together.
Aster
Mr211's Blog - Yahoo!?????
Hi:
No Better just your like or not.
This is DIY.
If yr direct connect to codec chip and yu better have a nice impendece matching.
your have to check DAC L+/L- output imp. value and close to your OPT Imp. .
If match not good your will loss signal too.
Btw after check wm8741 spec. diff.-out min load about 2K.
Aster
http://tw.myblog.yahoo.com/jw!9frLFy6fAkV0gBy_oZT_geG5fC24WQ--
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24/96-192 flac files
Have some people found that their WM8740 4.0 DACs will not play some 24/96-192 flac/wav files ?
I have also found that when plugging in my SPDIF into my DAC it plays even when the ground is not connected on the RCA plug this was repeated at friends house also but was worse as we could not get a signal lock , could this be why he has redesigned some of the digital input section of the board in his latest version of the WM8740 4.0 ?
Have some people found that their WM8740 4.0 DACs will not play some 24/96-192 flac/wav files ?
I have also found that when plugging in my SPDIF into my DAC it plays even when the ground is not connected on the RCA plug this was repeated at friends house also but was worse as we could not get a signal lock , could this be why he has redesigned some of the digital input section of the board in his latest version of the WM8740 4.0 ?
yes for direct connection you will need to load the primary with 2k+ it should reflect the same impedance as the next stage, so whatever the input impedance of your amp is, you should try and match this as loading on the primary of the tx. the onetics are 600:600 if its the same as mine, so load with same on both sides as the input impedance of your amp will be reflected to the primaries. its a funny old world in this area, so may be totally incorrect.
one thing i definitely agree on, what would be the point of using tx on the output after the opamp and buffer? the whole point of that mod is avoiding the output stage opamps, galvanic isolation is minimal, especially if you use balanced out; so you would just be adding another component for no reason and rolling off the top end for nothing
one thing i definitely agree on, what would be the point of using tx on the output after the opamp and buffer? the whole point of that mod is avoiding the output stage opamps, galvanic isolation is minimal, especially if you use balanced out; so you would just be adding another component for no reason and rolling off the top end for nothing
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Hi:
WM8740 only could receive PCM or I2S formate.
But your problem is SPDIF receiver problem.
That's different issue.
The working block will be RCA-> SPDIF receiver-> PCM formate-> WM8740-> Balance I/V out->PWM filter->Buffer.
WM870 no local clock and it working in PLL Mode( auto Phase lock loop).
Your got check SPDIF receiver circuit.
Br,
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