Success Rolling Opamps in EE Minimax DAC

i own the minimax dac. i have several nos tubes. i believe that if you use the tube gain stage, you bypass the opamp. is this correct ?

if this is correct, it may be more productive of your time to tunr the dac with a tube rather than try to find a suitable opamp.

also, if i am correct isn't the absence of an opamp preferable to the presence of an op amp ??

Mrtennis, to my ear the influence of the Opamps supercedes that of the tube rolling.

I'm checking on the SS/tube output question.

Doug, As you know there are two pairs of opamps in the EE DAC: Two NE5532 dual opamps for I/V (current to voltage) for tube and solid state; and two NE5534 single opamps for solid state output only.

Operating the EE DAC with the tube stage engaged bypasses the single opamps' circuit.

I generally prefer operating the DAC in solid state mode and found that rolling a variety of quality (read "expensive") tubes didn't have nearly the beneficial effect as did switching to your LME497X0 opamps.

Njs, you are right on the money with your answer. I received the reply from Alex Yeung, designer of the Minimax DAC, and you have it right.

One set of Opamps are always used regardless of output SS/tube. The other set of Opamps is only used with SS output. In my testing I heard what I felt were clear distinctions with different Opamps using the tube output but I did not want to comment definitively until the question was answered, providing verification.

Yes, it is certainly an acceptable choice to run the unit in SS output and with the upgraded Opamps it is quite refined.

Anyone care to comment on the influence of the power supply on performance. There are competing DAC designs claiming the importance of power supply chokes or elaborate regulation and transformers to serve as important elements.

I suppose this is the sum of all the parts concession I can make but wonder too why the smaller parts are not given more respect or attention.

Kudos to Doug for shifting the direction.