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When I connect a multiturn pot to ground (acting as I/V resistor) on output of TDA1545 pin I get 4.5V accross it only when I set pot to 17K - this represents about 0.26mA output. I have 11K & 11K resistors on Vref pin as per max dynamic swing in TDA1545 datasheet.
Is my TDA1545 chip busted or is ther another issue?
Another question - why is input resistor to Vref set to 33K on Thorsten's post on battery supply & I/V to TDA1545?
When I connect a multiturn pot to ground (acting as I/V resistor) on output of TDA1545 pin I get 4.5V accross it only when I set pot to 17K - this represents about 0.26mA output. I have 11K & 11K resistors on Vref pin as per max dynamic swing in TDA1545 datasheet.
Is my TDA1545 chip busted or is ther another issue?
Another question - why is input resistor to Vref set to 33K on Thorsten's post on battery supply & I/V to TDA1545?
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Re: OPA660 I/V for TDA1545
Konnichiwa,
Something is wrong. You need to check your wiring and the Chip. Even my understanding of how the Output current is build up is wrong, your results suggest a fundamental problem.
The resistors between +V and the Ref pin are 2 X 11k? Then the absolute minimum output current should be 1mA for digital silence. You have much less than that.
No.
Sayonara
Konnichiwa,
jkeny said:
Something is wrong. You need to check your wiring and the Chip. Even my understanding of how the Output current is build up is wrong, your results suggest a fundamental problem.
The resistors between +V and the Ref pin are 2 X 11k? Then the absolute minimum output current should be 1mA for digital silence. You have much less than that.
jkeny said:
No.
Sayonara
Kuei,
I'm setting up an upgrade for an Onkyo DX607 which is a nice built CD player that has a Sigma Delta DAC which will be replaced by a AD1865N-K DAC chip.
This AD chip has a +-1mA current output, reading the data sheet it appears that the signal from it is centered at 0 mA but I can't be sure.
My idea has been to make an outboard I/V using the OPA660 and would like to hear your suggestion on how to modify the values of the circuit to be compliant with the new operating conditions.
In the other hand, related to this same CDP and modification it has been suggested by Haly on the AD1865N-K Project thread that using D flipflops through the connections between DF and DAC would be a good idea to reduce jitter plus also the use of ISO150 isolators will reduce RF from the DF. What would be your opinion an suggestion on these?
I'm setting up an upgrade for an Onkyo DX607 which is a nice built CD player that has a Sigma Delta DAC which will be replaced by a AD1865N-K DAC chip.
This AD chip has a +-1mA current output, reading the data sheet it appears that the signal from it is centered at 0 mA but I can't be sure.
My idea has been to make an outboard I/V using the OPA660 and would like to hear your suggestion on how to modify the values of the circuit to be compliant with the new operating conditions.
In the other hand, related to this same CDP and modification it has been suggested by Haly on the AD1865N-K Project thread that using D flipflops through the connections between DF and DAC would be a good idea to reduce jitter plus also the use of ISO150 isolators will reduce RF from the DF. What would be your opinion an suggestion on these?
Konnichiwa,
Assuming that you are right, simply remove the "bias" circuit that removes the offset on the TDA1541 and double the I/V resistor in value. Done.
Good idea.
Potentially good. It is equally good, but without jitter penalty (if using opto couples re-clock AFTER the OC's) are fully galvanically separate supplies for the DAC and that using very low leakage transformers in both Digital and DAC section (meaning no noise on ground and current loops closed locally).
Sayonara
apassgear said:
Assuming that you are right, simply remove the "bias" circuit that removes the offset on the TDA1541 and double the I/V resistor in value. Done.
apassgear said:
Good idea.
apassgear said:
Potentially good. It is equally good, but without jitter penalty (if using opto couples re-clock AFTER the OC's) are fully galvanically separate supplies for the DAC and that using very low leakage transformers in both Digital and DAC section (meaning no noise on ground and current loops closed locally).
Sayonara
Coming back to the TDA1541 + OPA660.
After discussing the the drift of some other I/V on the AD1865N-K Project thread with Kello and P. Daniel I started monitoring these on the output of the OPA660 and found that with the lid on the CDP I had not more than 3 mv of variation so decided to get rid of the output caps.
The results were as expected, a great improvment of dynamics and resolution with improved bass openness and low level transients.
Now there is a more solid soundstage and details such as palpable tricks from lips and tongue done by singers...
I have a G. Tent clock that is waiting to be tested on this CDP and will report on the added benefits as soon as implemented.
I'm getting close to that objective of no cap on the signal path except for those of the PSU. The only remaining caps are on the output of the line amp, they will be replaced also with trafos in the near future.
After discussing the the drift of some other I/V on the AD1865N-K Project thread with Kello and P. Daniel I started monitoring these on the output of the OPA660 and found that with the lid on the CDP I had not more than 3 mv of variation so decided to get rid of the output caps.
The results were as expected, a great improvment of dynamics and resolution with improved bass openness and low level transients.
Now there is a more solid soundstage and details such as palpable tricks from lips and tongue done by singers...
I have a G. Tent clock that is waiting to be tested on this CDP and will report on the added benefits as soon as implemented.
I'm getting close to that objective of no cap on the signal path except for those of the PSU. The only remaining caps are on the output of the line amp, they will be replaced also with trafos in the near future.
AD844 or OPA660
Hello,.... I am totally new here......and wondering....
If I dont remember wrongly I have been warned (read) in the past about using BurrBrown OP-Amp's (i am aware this is not an ordinary OP-Amp...) as audio amplifiers, as they used to have good data, but not so good sound....but I dont remember where I read this....
Analog Devices on the other hand have an outstanding reputation making great sounding OP-Amps.....
Have anyone had the opportunity to listen to them both in the same environment ??
I am thinking about uppgrading my old DCD-2560 with new I/V stages (AD844 ?), and Elso Kwak's clock7.
This player have 4psc. of AD1862 DAC's (Balanced!?), and i was thinking about building 4 I/V stages trying to get a "perfect" balanced output from my CDP.
(the player have no balanced output today...)
Is this possible?
Have anyone of u tried this (on Denon (2560)) before??
P
Hello,.... I am totally new here......and wondering....
If I dont remember wrongly I have been warned (read) in the past about using BurrBrown OP-Amp's (i am aware this is not an ordinary OP-Amp...) as audio amplifiers, as they used to have good data, but not so good sound....but I dont remember where I read this....
Analog Devices on the other hand have an outstanding reputation making great sounding OP-Amps.....
Have anyone had the opportunity to listen to them both in the same environment ??
I am thinking about uppgrading my old DCD-2560 with new I/V stages (AD844 ?), and Elso Kwak's clock7.
This player have 4psc. of AD1862 DAC's (Balanced!?), and i was thinking about building 4 I/V stages trying to get a "perfect" balanced output from my CDP.
(the player have no balanced output today...)
Is this possible?
Have anyone of u tried this (on Denon (2560)) before??
P
Guido or anyone else: this link appears dead (after many years...).
Did anybody perchance download this file?
Thanks,
jd
Hello janneman
I've use wayback machine at the web.archive.org and I found the new link for the dc servo file ;
http://web.archive.org/web/20041027034615/home20.inet.tele.dk/kou/dcservo.html
You can directly download the file there;
http://web.archive.org/web/20041027034615/http://home20.inet.tele.dk/kou/files/servoamp.zip
Btw, would you know if I can use the OPA860 as a drop-in replacement to goes into the circuit in the post 46 ?
Bye
Gaetan
I've use wayback machine at the web.archive.org and I found the new link for the dc servo file ;
http://web.archive.org/web/20041027034615/home20.inet.tele.dk/kou/dcservo.html
You can directly download the file there;
http://web.archive.org/web/20041027034615/http://home20.inet.tele.dk/kou/files/servoamp.zip
Btw, would you know if I can use the OPA860 as a drop-in replacement to goes into the circuit in the post 46 ?
Bye
Gaetan
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