Go Back   Home > Forums > Source & Line > Digital Line Level

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 21st January 2012, 05:26 AM   #231
diyAudio Member
 
Join Date: Jan 2008
Location: Virginia
Dude, TDA1541 is boring. I have a TDA1541 and I know it sounds (OS or NOS), compared with PCM61+Alpha DF (delivers 20 bit) or PCM1791 (with or without Alpha 24 Processing Plus).
Adding an "A" in the tail does not make it a different device, even if some people think is somehow "magic". It just lifts it a little bit (don't want to go into details). Two of them has it contending probably for the 17 bit realm. But not with the NE5532 as I/V that it has now.
Discrete stages where tried by many companies and didn't deliver the nirvana. If you manufactured something better than 5532 - good job. Allow me
to be skeptic that is better than a modern OpAmp.

Because that is the discution about (not the comparations with others)- is a modern OpAmp capable of delivering as I/V for TDA1541?

PS: Yes DCM-360 it's a carusel player with a very interesing DF and DAC stage. But that is another story.

Last edited by SoNic_real_one; 21st January 2012 at 05:42 AM.
  Reply With Quote
Old 21st January 2012, 08:42 AM   #232
diyAudio Member
 
Join Date: Mar 2011
The best i/v for TDA1541 is a common base input with input impedance less than 15 ohms.
And no feedback.
To achiev this, use enough current and fold the current back with a current mirror or a folded cascode. There you go, with an 2k resistor to ground, which converts the 2mA into 2Volts. A cap in parallel will give you a 1. Order low pas. Put a buffer after this, eg. this Pass diy buffer. Its even cheaper than those fancy AD797 or OPA637.

Last edited by sottomano; 21st January 2012 at 08:45 AM.
  Reply With Quote
Old 21st January 2012, 08:47 AM   #233
diyAudio Member
 
Join Date: Apr 2008
Quote:
Originally Posted by SoNic_real_one View Post
Dude, TDA1541 is boring. I have a TDA1541 and I know it sounds (OS or NOS), compared with PCM61+Alpha DF (delivers 20 bit) or PCM1791 (with or without Alpha 24 Processing Plus).
Adding an "A" in the tail does not make it a different device, even if some people think is somehow "magic". It just lifts it a little bit (don't want to go into details). Two of them has it contending probably for the 17 bit realm. But not with the NE5532 as I/V that it has now.
Discrete stages where tried by many companies and didn't deliver the nirvana. If you manufactured something better than 5532 - good job. Allow me
to be skeptic that is better than a modern OpAmp.

Because that is the discution about (not the comparations with others)- is a modern OpAmp capable of delivering as I/V for TDA1541?

PS: Yes DCM-360 it's a carusel player with a very interesing DF and DAC stage. But that is another story.
"Then what are you doing on this thread" go heckle (also known as an agitant) some other people that like cheapy boring carousel players .

Comparing a cheapy boring carousel player with a cheapy budget TDA1541A about sums up your experience again just let people be if you do not like something then go start a thread about it but do not heckle people that legitimately want to be informed by what Thorsten and others have to say .

P.S. Perhaps you can start a thread about "any good boring cheapy consumer carousel players" so we can all critique it as you have done so kindly here .
  Reply With Quote
Old 21st January 2012, 08:51 AM   #234
diyAudio Member
 
Join Date: Mar 2011
Thank you Paul. I felt the same.
  Reply With Quote
Old 21st January 2012, 09:01 AM   #235
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
The TDA1541 is such a beast it can be downright frustrating researching for a build with it. Ever heard of the Killer DAC? Has a cult-like following with the Aussies, but looking at the price and what it contains But hey at least it isn't an ESS switcher.

Anyway, We know that the TDA1541 needs 0.00V to a max 25mV between its output and its ground pin, per the datasheet (max voltage compliance). That means a low input impedance into the mhz is required to meet spec. This is the only significant detail we have from the primordial soup of DAC's on how to build an analog stage, it is the fundamental constraint. Yes I believe this compliance spec was taken out of subsequent i-out DAC's publications because their own datasheet's opamp I/V's didn't meet the spec, so it was discarded for marketing reasons (sell a few opamps with each dac chip.) Big companies suck like that, just like they do today with the fudged up datasheets for the S-D switchers being adored by those who have never heard anything else.

Now if an opamp I/V has an input impedance that rises with frequency (I am afraid they all do), and that impedance is over 12.5 ohms at the fast frequency of the LSB steps that make up our "0-20khz" output (note the quotation marks.) we we have the TDA1541A running out of spec with regard to voltage compliance. That coupled with higher order distortion present with opamps has always had me looking for something drastically different than a opa275 or 627 I/V.

Current output DAC's can get nasty sounding the further out-off spec we run with regard to voltage compliance, I think worse when this impedance is constantly changing with each bit shift out as happens with opamps. It is very telling that rf design doesn't use opamps, yet any dac step is obviously rf?

Many of us have gotten by with passive I/V + tube gain, and Ove's website has good info on this, personally I found it to be one of the better options for the PCM63K. But I do think the tube "dither" helps hide some of the voltage compliance nasties. A pcm1704 with a passive I/V and a high quality jfet phono type gain stage can give one some good insite into the voltage compliance induced distortion issue, it is not pleasant and I consider it one of the worst forms of IMD that subtely attacks the micro details in music. Original thought was outof spec voltage compliance just led to protection diodes clipping with only 2H and this has been shown to be drastically off-base with most i-out dac's (the AD1865 and TDA1543 seem to be the only two that exhibit this behavior and they are much easier to work with.) With DAC's, true distortion (not just snr) gets worse with smaller signals, its the opposite of analog, and the signal at-60db level behavior is important to SQ and intuitively closely tied to the voltage compliance fundamental design constraint. Interstingly the TDA1543 and the AD1865 both don't look too good -60dB down.


I think as far as SS for the TDA1541, it would be tough to do better than a mofset Pass D1 I/V somehow incorporating Thorsten's filter? Maybe Thorsten can answer if a mofset d1 stage could be made a match for NOS ?

Some like the Jocko/Rorehberg stage. They keep the voltage compliance in spec by working like a transformer (reflecting a lower impedance to their inputs) , but I haven't had much luck with the Jocko style BJT I/V. They tend to have way too much IMD/THD. The only luck I've had with a BJT I/V is by cheating with 30dB local NFB preceded with filtering the current out, then following the I/V followed with a diamond buffer, can't explain why but it sounds good and measures very good. And is my goto for oversampling i-out r2r. But it won't work with NOS.

I want to try NOS TDA1541A, Lazlo has a TDA1541 into transformer + tube push-pull I/V with ~1ohm input impedance posted on this forum that is probably the most innovative tube analog stage for an i-out dac I have ever seen, yet unfortunatley it requires two TDA1541's in differential mode which obviously has a host of problems in setting up on the digital front end. And I think it would be difficult to implement a proper nos filter, so really a good digital oversampler filter with an inv data output would be ideal for this.

I have a TDA1541 tucked away and do plan on building it up with Thorsten's veroboard idea. Right now I am leaning toward Ove's passive I/V (with a current source cancelling out the DC offset) but using a D3A triode (high gain low noise, low distortion.) If you look at Oleg's published 1khz FFT's on his website they are better than any other analog stage for the TDA1541 made public. For my time that says a lot.

But I want to incorporate Thorsten's NOS compensation filter, never liked NOS probably because I never set up his filter to keep the treble from rolling off! (somehow I missed this innovation.) Probably will use Jocko/Rankin's asynch usb SPDIF (3ps rms jitter)->wm8804 (50ps min up to not specified jitter), no masterclock in the DAC, despite what many claim the technology just isn't available publicly to effectively slave a computer to a TDA1541 and Brown (ECDesigns) will be the first one to tell you this.

A lot of folks follow Thorsten and ECDesigns ideas/philosophies, and they are very good. One thing that bothers me is ECDesigns doesn't use the compensation filter, that a huge difference in design philosphy?

But a reality check I think for practical home builder (who isn't selected for Thorstens project) probably Ove has a lot to offer the hobbiest looking to have a good sounding TDA1541A. I do recommend anyone coming to this thread with interest in the 1541A to check out Ove's website. He has well documented measurements which show low IMD (abrax email the man for the %'s if you don't believe me


Most of all I am glad to see some enthusiasm in this chip as opposed to yet another S-D, hope the constructive arguments/disagreements fuel the innovation and keep things going.

peace
  Reply With Quote
Old 21st January 2012, 10:35 AM   #236
diyAudio Member
 
Join Date: Jun 2007
If by filter are referring to sinc correction it can simply be accomplished by a 8.2mh inductor in series with the 1k5 iv resistor (assuming 4ma pp) and a 3.3nf capacitor across them. However in case of an iv such as the d1 where you have a bias current running through the iv resistor you need an inductor that is rated for that and there are some debate about the long term affects on sound quality from running dc biased ferrite indicators like that
  Reply With Quote
Old 21st January 2012, 11:11 AM   #237
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Quote:
Originally Posted by Tazzz View Post
If by filter are referring to sinc correction it can simply be accomplished by a 8.2mh inductor in series with the 1k5 iv resistor (assuming 4ma pp) and a 3.3nf capacitor across them. However in case of an iv such as the d1 where you have a bias current running through the iv resistor you need an inductor that is rated for that and there are some debate about the long term affects on sound quality from running dc biased ferrite indicators like that
yes sinc correction. I have had bad luck in general with inductors in DAC filters, air core inductors sound best yet they pick up hum. Always tried to avoid them.

I completely missed the original sinc correction discussions as I was turned off to NOS due to all the poor designed TDA1543 based NOS DAC's and I was a PM/SM oversampling only person at the time. Guess I have a lot of homework to do.

thanks
  Reply With Quote
Old 21st January 2012, 11:21 AM   #238
diyAudio Member
 
Join Date: Dec 2003
Location: Sydney
Quote:
Originally Posted by regal View Post
The TDA1541 is such a beast it can be downright frustrating researching for a build with it. Ever heard of the Killer DAC? Has a cult-like following with the Aussies, but looking at the price and what it contains But hey at least it isn't an ESS switcher.

Anyway, We know that the TDA1541 needs 0.00V to a max 25mV between its output and its ground pin, per the datasheet (max voltage compliance). That means a low input impedance into the mhz is required to meet spec. This is the only significant detail we have from the primordial soup of DAC's on how to build an analog stage, it is the fundamental constraint. Yes I believe this compliance spec was taken out of subsequent i-out DAC's publications because their own datasheet's opamp I/V's didn't meet the spec, so it was discarded for marketing reasons (sell a few opamps with each dac chip.) Big companies suck like that, just like they do today with the fudged up datasheets for the S-D switchers being adored by those who have never heard anything else.

Now if an opamp I/V has an input impedance that rises with frequency (I am afraid they all do), and that impedance is over 12.5 ohms at the fast frequency of the LSB steps that make up our "0-20khz" output (note the quotation marks.) we we have the TDA1541A running out of spec with regard to voltage compliance. That coupled with higher order distortion present with opamps has always had me looking for something drastically different than a opa275 or 627 I/V.

Current output DAC's can get nasty sounding the further out-off spec we run with regard to voltage compliance, I think worse when this impedance is constantly changing with each bit shift out as happens with opamps. It is very telling that rf design doesn't use opamps, yet any dac step is obviously rf?

Many of us have gotten by with passive I/V + tube gain, and Ove's website has good info on this, personally I found it to be one of the better options for the PCM63K. But I do think the tube "dither" helps hide some of the voltage compliance nasties. A pcm1704 with a passive I/V and a high quality jfet phono type gain stage can give one some good insite into the voltage compliance induced distortion issue, it is not pleasant and I consider it one of the worst forms of IMD that subtely attacks the micro details in music. Original thought was outof spec voltage compliance just led to protection diodes clipping with only 2H and this has been shown to be drastically off-base with most i-out dac's (the AD1865 and TDA1543 seem to be the only two that exhibit this behavior and they are much easier to work with.) With DAC's, true distortion (not just snr) gets worse with smaller signals, its the opposite of analog, and the signal at-60db level behavior is important to SQ and intuitively closely tied to the voltage compliance fundamental design constraint. Interstingly the TDA1543 and the AD1865 both don't look too good -60dB down.


I think as far as SS for the TDA1541, it would be tough to do better than a mofset Pass D1 I/V somehow incorporating Thorsten's filter? Maybe Thorsten can answer if a mofset d1 stage could be made a match for NOS ?

Some like the Jocko/Rorehberg stage. They keep the voltage compliance in spec by working like a transformer (reflecting a lower impedance to their inputs) , but I haven't had much luck with the Jocko style BJT I/V. They tend to have way too much IMD/THD. The only luck I've had with a BJT I/V is by cheating with 30dB local NFB preceded with filtering the current out, then following the I/V followed with a diamond buffer, can't explain why but it sounds good and measures very good. And is my goto for oversampling i-out r2r. But it won't work with NOS.

I want to try NOS TDA1541A, Lazlo has a TDA1541 into transformer + tube push-pull I/V with ~1ohm input impedance posted on this forum that is probably the most innovative tube analog stage for an i-out dac I have ever seen, yet unfortunatley it requires two TDA1541's in differential mode which obviously has a host of problems in setting up on the digital front end. And I think it would be difficult to implement a proper nos filter, so really a good digital oversampler filter with an inv data output would be ideal for this.

I have a TDA1541 tucked away and do plan on building it up with Thorsten's veroboard idea. Right now I am leaning toward Ove's passive I/V (with a current source cancelling out the DC offset) but using a D3A triode (high gain low noise, low distortion.) If you look at Oleg's published 1khz FFT's on his website they are better than any other analog stage for the TDA1541 made public. For my time that says a lot.

But I want to incorporate Thorsten's NOS compensation filter, never liked NOS probably because I never set up his filter to keep the treble from rolling off! (somehow I missed this innovation.) Probably will use Jocko/Rankin's asynch usb SPDIF (3ps rms jitter)->wm8804 (50ps min up to not specified jitter), no masterclock in the DAC, despite what many claim the technology just isn't available publicly to effectively slave a computer to a TDA1541 and Brown (ECDesigns) will be the first one to tell you this.

A lot of folks follow Thorsten and ECDesigns ideas/philosophies, and they are very good. One thing that bothers me is ECDesigns doesn't use the compensation filter, that a huge difference in design philosphy?

But a reality check I think for practical home builder (who isn't selected for Thorstens project) probably Ove has a lot to offer the hobbiest looking to have a good sounding TDA1541A. I do recommend anyone coming to this thread with interest in the 1541A to check out Ove's website. He has well documented measurements which show low IMD (abrax email the man for the %'s if you don't believe me


Most of all I am glad to see some enthusiasm in this chip as opposed to yet another S-D, hope the constructive arguments/disagreements fuel the innovation and keep things going.

peace
Completely agree about fundamental constraint remark!

Not long ago I started the thread asking for 1704 compliance voltage specifications.....from your statements above, it seems you may know the answer?

Boky
  Reply With Quote
Old 21st January 2012, 11:59 AM   #239
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Quote:
Originally Posted by Extreme_Boky View Post
Completely agree about fundamental constraint remark!

Not long ago I started the thread asking for 1704 compliance voltage specifications.....from your statements above, it seems you may know the answer?

Boky
I tried to send you a PM , couldn't get it to work. Try to send me one.
  Reply With Quote
Old 21st January 2012, 12:35 PM   #240
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by SoNic_real_one View Post
So... YOUR measurement tool/method was flawed. That does not mean that ALL the tools/methods are flawed. Or that the measurements are useless.
I am not sure what argument you are attempting to made.

I answered a post in which you had stated:

Quote:
Originally Posted by SoNic_real_one View Post
And, even if I still hear distortions well, I trust measurements more.
I was merely giving you an example where trusting measurements that proclaimed an absence of distortion was the unwise choice and trusting ones senses that told one that there was distortion was the wise choice.

I would also add something that was an adage of our professor in "Messtechnik" - a module in my EE course that thought the 4-T's (Tips, Tricks, Traps and Techniques) of measurements and testing, not audio, but in general.

Whenever one of us was too convinced that what we measured was real, he used intone in a thunderous voice "Wer misst misst mist.", which is only really cute in german but translates to "Who measures measures manure".

He instilled in me a robust and healthy scepticism regarding whatever measurements I make and an equally robust and healthy tendency to take others measurements "cum grano salis". And don't get me started on circuit simulators, who's output is nowadays so frequently substituted for real evaluations of real circuits on the clear and dramatic misunderstanding that real circuits behave in reality the way they simulate...

Quote:
Originally Posted by SoNic_real_one View Post
However, in the subject at hand, you are basically trading SNR (using a compliant resistor for I/V you have a low signal) to avoid an eventual slew-rate induced distortion.
In the subject on hand I suggested using Op-Amp's with sufficient slew rate. I also pointed out that using resistor I/V conversion may be used. For the TDA1541 combined with a tube giving around 30dB Amplification we need around 47...51 Ohm I/V Resistance.

Such a resistor has a Johnson noise of around -138dBV over a 20KHz bandwidth, the signal developed would be -24dBV.

So the available SNR after the I/V resistor is around 114dB (unweighted), which is lower than noise of the DAC (and indeed of many other DAC's with a greater claimed number of Bits)...

BTB, for the Shanling Players I used to modify I had parallel PCM1704 with resistor I/V had a theoretical noise limit of -118dB for the passive I/V and still exceeded the SNR (unweighted) of two of this "24-Bit" DAC paralleled.

So, for now I do not see any trading of SNR at all.

Quote:
Originally Posted by SoNic_real_one View Post
Small capacitors on inputs of fast OpApms (and on feedback) limit that slew-distortion well and they are not so much of a load to induce distortions.
Do you have proof your claim?

Ciao T
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Raindrop Hui TDA1541A DAC Kit wushuliu Swap Meet 25 21st November 2013 10:07 AM
which clock for analogmetric tda1541A dac kit Chilli6565 Digital Source 4 6th May 2010 12:41 PM
FS: AYA DAC Rev 2.0b TDA1541A Non-Oversampling DAC kit or complete krishu Swap Meet 0 17th December 2009 09:33 AM
Recommend a DIY tda1541a dac kit? boidos Digital Line Level 2 6th August 2009 01:43 PM
TDA1541A Chineese DAC KIT UV101 Digital Source 8 10th February 2009 10:46 AM


New To Site? Need Help?

All times are GMT. The time now is 02:31 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2