Can you try:
* Disconnect the coax input to the DAC and see if the thumps remain.
* Take the earth from the preamp (or at least from the powerboard the preamp is plugged into) and connect that to the outer ring of the RCA output(s) in the DAC? See if that introduces a constant hum or kills your thumps.
I understand you don't have a ground connected to the DAC and this may well be a wild goose chase but it's the only idea I have to run with...
giga works
Hi all, I'm going to have a go at this.. just ordered it.
Looking at the Tx coupling option and it looks like Sowter's transformers for DAC (esp. 9762) appears to be just the ticket for this one.
SOWTER DAC I/V TRANSFORMERS
But it's not cheap...
cheers
wjam
Hi all, I'm going to have a go at this.. just ordered it.
Looking at the Tx coupling option and it looks like Sowter's transformers for DAC (esp. 9762) appears to be just the ticket for this one.
SOWTER DAC I/V TRANSFORMERS
But it's not cheap...
cheers
wjam
Sowter Tx test
Interesting. Like previous poster on page 5 or 6 I have less output but enough to get decent levels for normal listening.
However, my bass is shot to hell... What's there is poorly defined, with no extension.
Mid and top end is nice, but i can't live with the bass.
I think it is a mismatch to my TVC... sp perhaps I might need to use the TX as feed to a tube grid. Maybe ECC99 balanced some day in the future, but for now I'm going back to the AD op-amps, for which I need to cure the thumping! Anyone cured that?
The Tx had no thumps. I suspect a ground issue
cheers
Interesting. Like previous poster on page 5 or 6 I have less output but enough to get decent levels for normal listening.
However, my bass is shot to hell... What's there is poorly defined, with no extension.
Mid and top end is nice, but i can't live with the bass.
I think it is a mismatch to my TVC... sp perhaps I might need to use the TX as feed to a tube grid. Maybe ECC99 balanced some day in the future, but for now I'm going back to the AD op-amps, for which I need to cure the thumping! Anyone cured that?
The Tx had no thumps. I suspect a ground issue
cheers
Hi.
I've just pulled out this dac again to do some measurements, and with a 1khz 0db sinus test tone, it gives about 3,14vpp on the U12 pin 1.
But when the resistors are replaced with 540ohm (2x240ohm in series) it gives a nice 2,10vpp on the pin1.
This also lower the output to about 2vrms which equals the output from an old Denon cdp.
I think it would be better to use 500ohm instead of your suggested 300ohm, to keep the output the same as on standard cdp's.
I cannot do any distortion measurements, but from the data sheet curves it stays well within acceptable levels.
Regards
Kim
Would be put a 1K or 1K2 resistor in parallel with 820 Oh. (aprox. 500 Oh.)
Sounds like a good idea. I do not know if it will be better or worse than a 470 Oh. parallel but better than the only 820 Ohm. , I think.
Rather than measuring, we should compare which sounds better.
Probably the best sound is your proposal.
Ok, I am a complete newb, I'm ok with a soldering iron, have built some stuff (hagtech bugle, bottlehead Eros, etc)
I'm making nothing but mistakes when it comes to this lampization stuff..
I have a SB3 and I just got a gigawork 'new' DAC, and I have salvaged the tube output stage from my Modwright plat. truth 999es, along with the PS9.0 power supply.
What I'd love to do is: find out where to 'tap' the dac outputs before the opamps, and:
make any mods necessary to use the MW tubestage for the gigawork's output.
I tried to do this with the SB3, and long story short.. it didn't work..
the tubes got hot, the 'music' sounded like hammered dogcrap... thin, static-ridden, but the 60hz buzz was clear, dynamic, and well defined!
any help would be greatly appreciated!
chers
I'm making nothing but mistakes when it comes to this lampization stuff..
I have a SB3 and I just got a gigawork 'new' DAC, and I have salvaged the tube output stage from my Modwright plat. truth 999es, along with the PS9.0 power supply.
What I'd love to do is: find out where to 'tap' the dac outputs before the opamps, and:
make any mods necessary to use the MW tubestage for the gigawork's output.
I tried to do this with the SB3, and long story short.. it didn't work..
the tubes got hot, the 'music' sounded like hammered dogcrap... thin, static-ridden, but the 60hz buzz was clear, dynamic, and well defined!
any help would be greatly appreciated!
chers
Ok, on my own here, I suppose.
I've gone ahead and pulled the opamps, there are pins on the underside labeled left -, left +
Right -, right +.
I'm guessing that's where I can tap the output from the chip itself,
To the tubestage, steal the 12.6vdc from the modwright tube rectified PS for the gigawork, and since Dan's tube stage is made to work with a V out dac, I think(?) a couple of resistors inline should make workie.
Driving blind.
I'll post pics or a eulogy.
I've gone ahead and pulled the opamps, there are pins on the underside labeled left -, left +
Right -, right +.
I'm guessing that's where I can tap the output from the chip itself,
To the tubestage, steal the 12.6vdc from the modwright tube rectified PS for the gigawork, and since Dan's tube stage is made to work with a V out dac, I think(?) a couple of resistors inline should make workie.
Driving blind.
I'll post pics or a eulogy.
And:
My cat Sofija
Regards zeoN_Rider
My cat Sofija
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An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Regards zeoN_Rider
Dobro veče!
My cat is from Belgrade too
Two switches, hmm one for power off/on and sec. for coax/opt.
Regards zeoN_Rider
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