I'm using an Audio Logic with 6922's and have never had that problem.
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It is not the cable ,or transport,or pre-amp,or anything else. It is beyond any doubt the ARC DAC-3 (FOUR 6922 OUTPUT STAGE) .Reason I know is because I eliminated every component in the system by ex-changing with another one .
I mean I used a second spare dac (stax talent) and another cd transport (musical fidelity A3 used as transport via digital output and as a stand alone cd player)and a different power-amp (mark levinson 27.5) and another line stage(used the HARMAN KARDON home theater receiver).
I mean I turned my system heads down till I was sure.
Every time that DAC-3 was feeding the signal upstream in the system the problem was there,and every time it was out ,the problem was gone.
Another words the signal coming from the DAC-3 is week and lifeless and lucking punch and dynamics,it's like listening to your alarm clock to wake up in the morning.
It is of that reason that I am wondering whether the tubes need to be replaced because they reached their usefull life.
If you take a look of the tubes they show a dark ,black dicoloration crown on their tops.
This is my opinion though and I would like to hear from somebody who knows better than me.
My knowledge is minimal in these matters.I am new into tubes too.
thanks in advance
First of all, the stock 6922 tubes are not even close to most of NOS tubes. That's why the seller didn't include those with the DAC.
As I replied you in your LS3B preamp question, I didn't think there was anything wrong with your preamp's volume control.
How was the tubes packed? if they were shipped inside of the DAC then it is possible that they could damaged from shipping. The damaged tubes would give you pop and hiss sound. "Lifeless and weak" has more to do with tube character itself. Get yourself Some NOS Amperex or Siemens 6DJ8s. If you want a lower noise type ( I would usually prefer lower noise for DAC but they're less liquid sounding) then get yourself some NOS Amperex/Siemens 7308 tubes.
I recently had the same problem with my Kora Hermes II dac. At first I thought it was a problem with my integrated amp, so I swapped in another amp and it was still there.
In discussing the problem with my local tech, he suggested the dac's output voltage may be overdriving the integrated's preamp section. He mentioned that a lot of tube dacs dump a high (7+) voltage unfiltered signal to the pre that (typically) is expecting only the industry standard 2 volts.
I don't know what the DAC-3's output voltage is but I'd ask the ARC tech support if this might be an issue.
My DAC-3 is still bad as ever,the output voltage is 1.5Vrms
and note that I am using a same brand linestage as my DAC.
That's Audio Research.I would think that both units coming from the same manufacturer are compatible. At this moment I am waiting (previous owner offering)for a set of different tubes so I can swap and see what happens.I am almost conviced that I experience a case of one or more bad tubes.
I'd call ARC as well, their customer service is excellent. It sounds like it could be tubes, but if it's in both channels it would be unusual for all the tubes to go bad at once. I have had 6DJ8/6922s (Sovteks) go bad in my Audio Logic, and they can make some nasty pops, which get louder over time, so I'd get it fixed sooner rather than later.