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Tubed DAC problems,opinions please.

Hi to all.
Recently I purchased a used AUDIO RESEARCH DAC-3 Tubed DAC with four 6922's output stage. When I hooked it up to my system I heard pops coming from the speakers and first blamed my ARC line stage LS3B and thought that volume control was dusty or something. I actually started a thread on AMPS-PREAMPS about it.
I was about ready to take my line stage in for check-up but the last minute I decided to re-check my whole set-up one more time.
Today after carefull ispection I realised that the DAC-3 is creating the pops and very low volume level (I mean low,to the point that at 11:00 pm position of volume control on the LS3B LINE STAGE the sound is barely noticeable).
Note that the DAC-3 is feeding my LS3B LINE STAGE which is driving a CONRAD JOHNSON MV55.
There is no doubt that something is wrong with DAC-3 .
The previous owner claims that it left his house in good working condition,but the FEDEX must of dropped it.
Do you think the problem got to do with the 6922,s tubes or must be something more serious.
I mean could the tubes produce above problems and by replacing with new ones everything gets fixed, the previous owner was using telefunken NOS and just put the stock 6922's in prior to shipping. But he says he checked two times and everything worked ,before shipping it to me.
I am confused,and not an expert ,please let me know your thoughts
Best regards
George
yioryos

Showing 1 response by s23chang

s23chang
620 posts
 
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.
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