tried one, several error inside:
1)ground in and ground out on the output spdif transformer shorted, so you loose the benefit of using a transformer: galvanic isolation
2)wrong output level, near 4Vpp (open) vs 1Vpp of the standard
3)wrong output impedance (i don't remember but different from 75ohm)
i modded it to solve this errors, now is better but the result do not justify the time i spent on it
Ciao
Andrea
problem!!!
the OPTICAL input doesn't work.
i have improved the basic DAC(seller snow_48)with the transformer DV-709 on Input.
i have removed the little jump where is the place of the transformer.
from the OPTICAL input no music but only noise increasing.
someone know if the little jump must stay in place or must be removed.
thanks a lot for help.
rob
the OPTICAL input doesn't work.
i have improved the basic DAC(seller snow_48)with the transformer DV-709 on Input.
i have removed the little jump where is the place of the transformer.
from the OPTICAL input no music but only noise increasing.
someone know if the little jump must stay in place or must be removed.
thanks a lot for help.
rob
output voltage too high now on my Gigawork?
Using the Burson dual on the third op-amp socket and 2 x TLE2062 on the I/Vs.
Some CDs are overdriving the input on my amp now, even tried my old MF X10-D tube buffer between DAC and amp to try impedance matching the output, but continuing to hear distortion on hotter tracks. Toslink-in via PC is fine, but my CD's S/PDIF > Gigawork -> amp is distorting on louder passages. Have not measured, as i only have a DMM.
Any ideas on how i might attenuate the RCA out without compromising the signal would be most appreciated.
Could this be due to a non-75ohm S/PDIF cable (using homebrew RCA coax of unknown impedance)?
Using the Burson dual on the third op-amp socket and 2 x TLE2062 on the I/Vs.
Some CDs are overdriving the input on my amp now, even tried my old MF X10-D tube buffer between DAC and amp to try impedance matching the output, but continuing to hear distortion on hotter tracks. Toslink-in via PC is fine, but my CD's S/PDIF > Gigawork -> amp is distorting on louder passages. Have not measured, as i only have a DMM.
Any ideas on how i might attenuate the RCA out without compromising the signal would be most appreciated.
Could this be due to a non-75ohm S/PDIF cable (using homebrew RCA coax of unknown impedance)?
Swap the Burson for an OPA2134 or OPA1642!
If that doesn't help swap TLE2062 for LME49720! NO JFET OPAMPS FOR I/V CONVERSION!
A little "howto" for the guy who asked, and for any curious people around here.
So!
I got 2 Landahl transformers LL1636, wired as 1+1:10 with center tap
See the wiring of "C center tap" here :
http://www.lundahl.se/pdfs/datash/1636.pdf
Then 2 very high quality resistors, naked Z foils from vishay ("naked" z201, or VAR, or TX2575)
http://www.mimasa.co.jp/order/vishayCatalogue/VAR.pdf
I took some 15 kOhm resistors, but depending on your amplifier, you may have to get higher values.
My amp input impedance is 47 kOhm, if yours is the same or higher, you'll be fine with 15 kOhm.
If it's less than that, 22 kOhm resistor may be a better idea. (or even higher if your amp has very low impedance)
Remove the 3 opamps from the dac board, then see the interconnections on the following schematic (wiring.jpg)
I soldered the wires from the transformers primary directly on the empty sockets.
At the other side, I soldered the "ground" wire of the transformer's secondary to the "ground" of the RCA connector to cancel static noise and hums.
If everything is working fine (and it should!), you can then remove a few capacitors and resistors from the board, and disconnect half the power plug (alimentation for analogue parts, which is now fully deactivated)
Just look at the second attachment (DACremove.jpg).
I hope everything is clear, feel free to ask if you need more explainations.
So!
I got 2 Landahl transformers LL1636, wired as 1+1:10 with center tap
See the wiring of "C center tap" here :
http://www.lundahl.se/pdfs/datash/1636.pdf
Then 2 very high quality resistors, naked Z foils from vishay ("naked" z201, or VAR, or TX2575)
http://www.mimasa.co.jp/order/vishayCatalogue/VAR.pdf
I took some 15 kOhm resistors, but depending on your amplifier, you may have to get higher values.
My amp input impedance is 47 kOhm, if yours is the same or higher, you'll be fine with 15 kOhm.
If it's less than that, 22 kOhm resistor may be a better idea. (or even higher if your amp has very low impedance)
Remove the 3 opamps from the dac board, then see the interconnections on the following schematic (wiring.jpg)
I soldered the wires from the transformers primary directly on the empty sockets.
At the other side, I soldered the "ground" wire of the transformer's secondary to the "ground" of the RCA connector to cancel static noise and hums.
If everything is working fine (and it should!), you can then remove a few capacitors and resistors from the board, and disconnect half the power plug (alimentation for analogue parts, which is now fully deactivated)
Just look at the second attachment (DACremove.jpg).
I hope everything is clear, feel free to ask if you need more explainations.
Attachments
Last edited:
Finaly, I got my transformers output working!
Volume is a bit less stronger than with opamps but the sound is so gooooooood!
Lundahl ll1636 + 15kOhm vishay z201s resistors for i/v conversion
If anyone is interested, I can explain the whole schematic.
Just ask.
I go back listening now...
This is very interesting... and thank you SO VERY much for the how-to explanation (in the second post).
Can you describe the improvements in a few words? Anything lost or is everything better? Overall impressions vs. other DACs? Why did you choose that particular transformer?
Thanks in advance.
Hey! Thanks for your interest!
In a few words (you could have guessed) :
everything sounds better
Smoother, clean, free of any kind of distortions, wider scene, better instruments separation...
And what's more important, more enjoyable, not tiring at all.
Sounds more organic, more "analogical"...
At first, I though it was bass shy, but no, bass are here and strong, but so clean!
The only relative drawback is the small loss of output power level.
But I just turn my amp a fraction higher, and everything is fine!
I can only compare to a CD player : Micromega Minium Cd3 (350 to 500 euros) which sounds good enough to get a few awards (ok, french awards for a french company, they were a bit biased, but it's anyway a musical performer)
Micromega CD Lecteurs CD sur Son-Video.com
Well, everything above is based on direct comparaison between this cd player and the gigawork with transformers.
To conclude, a firm and enjoyable step up!
I chose LL1636 based on the choices made by the Rakk Dac designer for his Passive Output Stage Kit.
He uses LL1674 (1:4 step up) for a PCM1794 dac chip.
Gigawork uses PCM1798 dac chip which outputs half smaller current.
I could have used the same transformer with bigger I/V resistor but...
As I wanted to present a very small "equivalent" resistor to the dac chip (to avoid possible distortion and clipping), I chose the LL1636 for its 1:10 step up and amorphous core like the LL1674, even if they are smaller in size...
And a "center tap" was needed too.
(and they are cheaper!)
I'd like to compare the Rakk Dac with my modified Gigawork, to see if I miss something...
I don't know if I can recommend this mod to anybody, but I personnaly love the result on my system.
Cheers!
In a few words (you could have guessed) :
everything sounds better
Smoother, clean, free of any kind of distortions, wider scene, better instruments separation...
And what's more important, more enjoyable, not tiring at all.
Sounds more organic, more "analogical"...
At first, I though it was bass shy, but no, bass are here and strong, but so clean!
The only relative drawback is the small loss of output power level.
But I just turn my amp a fraction higher, and everything is fine!
I can only compare to a CD player : Micromega Minium Cd3 (350 to 500 euros) which sounds good enough to get a few awards (ok, french awards for a french company, they were a bit biased, but it's anyway a musical performer)
Micromega CD Lecteurs CD sur Son-Video.com
Well, everything above is based on direct comparaison between this cd player and the gigawork with transformers.
To conclude, a firm and enjoyable step up!
I chose LL1636 based on the choices made by the Rakk Dac designer for his Passive Output Stage Kit.
He uses LL1674 (1:4 step up) for a PCM1794 dac chip.
Gigawork uses PCM1798 dac chip which outputs half smaller current.
I could have used the same transformer with bigger I/V resistor but...
As I wanted to present a very small "equivalent" resistor to the dac chip (to avoid possible distortion and clipping), I chose the LL1636 for its 1:10 step up and amorphous core like the LL1674, even if they are smaller in size...
And a "center tap" was needed too.
(and they are cheaper!)
I'd like to compare the Rakk Dac with my modified Gigawork, to see if I miss something...
I don't know if I can recommend this mod to anybody, but I personnaly love the result on my system.
Cheers!
Hey! Thanks for your interest!
In a few words (you could have guessed) :
everything sounds better
Smoother, clean, free of any kind of distortions, wider scene, better instruments separation...
And what's more important, more enjoyable, not tiring at all.
Sounds more organic, more "analogical"...
At first, I though it was bass shy, but no, bass are here and strong, but so clean!
The only relative drawback is the small loss of output power level.
But I just turn my amp a fraction higher, and everything is fine!
I don't know if I can recommend this mod to anybody, but I personnaly love the result on my system.
Cheers!
Sounds like i'm going Lundahl shopping... thank you for your report!
Promised, I've no interest in Lundahl business
Cool, I'm looking forward to your impressions!
You know which resistors you will use?
Just a small precision, as I shortcut all the former output circuitry, there was a muting chip (powered with 6v) which is not in use anymore (the small chip under the dac board).
As a result, when there is no input signal (blue led off), the DAC outputs some "pink" noise.
This noise is gone as soon as the blue led shines.
I don't think it's a big problem, but I just wanted to mention it.
Grael,
I'm thinking I might try your transformer mod using these less expensive transformers:
EDCOR - MXL10cs
Do you see any reason why they would not work?
You mentioned a reduction in output when going to the transformers. Have you measured the Vout? I'm afraid of it being too low to drive my amplifier.
Thanks,
Jared
I'm thinking I might try your transformer mod using these less expensive transformers:
EDCOR - MXL10cs
Do you see any reason why they would not work?
You mentioned a reduction in output when going to the transformers. Have you measured the Vout? I'm afraid of it being too low to drive my amplifier.
Thanks,
Jared
Those elcor's should work, they have the mandatory "Center Tap" on the input.
Don't know about the sound quality.
I didn't measure my V out, but with formulas, with my 47kOhm amplifier, it's theoretically around 1.7/1.8 Vrms.
What is your amplifier input impedance?
(by the way, on the spec sheets, this elcor 's transformer may be a bit short in the high frequencies... but I don't know if it's wrong or not)
Don't know about the sound quality.
I didn't measure my V out, but with formulas, with my 47kOhm amplifier, it's theoretically around 1.7/1.8 Vrms.
What is your amplifier input impedance?
(by the way, on the spec sheets, this elcor 's transformer may be a bit short in the high frequencies... but I don't know if it's wrong or not)
but that transformer is a 1:10 ratio, thats some pretty serious gain. they are designed for low level microphone signals, not line level signals. you would have to at the minimum load the primary, but I really dont think its that suitable TBH. also has a 150R primary winding, far from the normal 600R of line trannies. they may well work, but certainly not ideal IMO
Ok, with a 100 KOhm input impedance ampli, you should get 2 Vrms with the 15 KOhm I/V resistors, you're good to go.
I really can't compare to "normal" line level transformer, I don't know anything about that, sorry...
I just know what used the guy from the Rakk dac and tried to build upon that. And I found it sounds good to me!
@qusc
I can just link to his explanation here :
Passive output
He says we can't compare typical transformer's use for line output with this particular i/v use. You think it's not an optimal use? Or was ok for a 1:4 step up, but not anymore for a 1:10?
Any comment would be appreciate, I need to learn!
I really can't compare to "normal" line level transformer, I don't know anything about that, sorry...
I just know what used the guy from the Rakk dac and tried to build upon that. And I found it sounds good to me!
@qusc
I can just link to his explanation here :
Passive output
He says we can't compare typical transformer's use for line output with this particular i/v use. You think it's not an optimal use? Or was ok for a 1:4 step up, but not anymore for a 1:10?
Any comment would be appreciate, I need to learn!
Learning about DAC's
Which Dac is the best?
Is up sampling better than NOS?
High Grade 24bit/192khz DAC with fully assembled kits - eBay (item 120551270004 end time Jun-30-10 02:48:28 PDT) $69.99
Hi End 24/192 DAC DA CONVERTER CS8416+CS8421+CS4398 USB - eBay (item 160446826476 end time Jun-21-10 22:37:28 PDT) $199.99
2010 UP-SAMPLING 24bit/192Hz DAC DA CONVERTER W/USB KIT - eBay (item 140411813616 end time Jun-27-10 20:14:24 PDT)
$74.99 3. DAC CS4398 -A stereo DAC for flagship audio products,
Advanced 24-bit resolution and sample rate up to 192kHz
120db dynamic range, -107db THD+N
(cs4398 can be updated to PCM1793,pay more 10dollars.can be updated to CS43122,pay more 15dollars)
Which Dac is the best?
Is up sampling better than NOS?
High Grade 24bit/192khz DAC with fully assembled kits - eBay (item 120551270004 end time Jun-30-10 02:48:28 PDT) $69.99
Hi End 24/192 DAC DA CONVERTER CS8416+CS8421+CS4398 USB - eBay (item 160446826476 end time Jun-21-10 22:37:28 PDT) $199.99
2010 UP-SAMPLING 24bit/192Hz DAC DA CONVERTER W/USB KIT - eBay (item 140411813616 end time Jun-27-10 20:14:24 PDT)
$74.99 3. DAC CS4398 -A stereo DAC for flagship audio products,
Advanced 24-bit resolution and sample rate up to 192kHz
120db dynamic range, -107db THD+N
(cs4398 can be updated to PCM1793,pay more 10dollars.can be updated to CS43122,pay more 15dollars)
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