Tube DACs

Personally I prefer a DAC's fixed output if it has any type of attenuators.   Even better is no variable output at all.   My DAC is the excellent sounding LAB 12 DAC 1 Reference.   Sure it has no features to speak of other than input selection and has a fixed analog output using a pair of 6922, but it sounds phenomenal .  

@macg19 I have a pair of Gold Lion and a pair of RCA Long Grey Plate aside from the stock ones that came with the DAC.  The Gold Lion weren't anything even remotely noticeable in difference.  The RCA I like the sound of, but there is a bit of break up and they are VERY microphonic so I can hear odd harmonics and noise level.  Nothing I have tried yet has 'warmed' things the way I'd like, without making things smooshy.  I have a pair of Legacy Studio HDs (recent version) and a Rega integrated amp, so there plenty of detail and accuracy, but things are a tad 'edgy' and can be fatiguing after a while of listening.

@amtprod I've tried the Gold Lion re-issue power tubes and pre-amp tubes and they don't do anything for me either. The RCA grey plates are not cheap, so perhaps there is an issue with the tubes. "Edgy" is exactly what I was trying to get rid of, and I have. 

Very happy with the Black Ice now...it is NOT the DAC (at least not in my system). 

It is not as simple as people think. Just because a dac outputs enough to drive an amp to full power or more we are forgetting that we almost NEVER listen at full output power. Instead we listen at levels close to 1w or so which in terms of DAC output signal is VERY low signal levels. Unfortunately most DAC’s and CD players place the volume pot after the gain blocks which drastically raises output impedance when used at volume settings less than 100% and gets to an insanely horrible situation at the 10 to 20% of full volume that listening levels demand.

Preamps are made specifically to give optimum performance at these greatly attenuated listening levels and do it with authority. This is the major problem with passive preamps and they lack dynamics and bass drive. Unless the DAC is designed a certain way to optimize very low signal output it will suffer.

Regarding a tube dac used with a tube preamp, it is wonderful IF you have a great tube preamp. Unfortunately there are a lot of cheaper tube components that use tubes in starvation of low plate current for a very "Tubey" sound. That is not my flavor and a proper tube design has transparency, purity and lack of grain that SS rarely achieves.

@dht4me 👍

I’m totally on board with the idea that a tube dac can work well with an excellent preamp. I’m currently using an Aqua La Scala with my ARC REF6 and have no issues.
As far as tubes go- I’ve had great luck following the advice given from Brent Jesse. I’m currently running NOS Telefunken red tips w/ wing shape plates- great tubes!