Amplifier Power tubes - important to sound?

@darkblacksmoke 

I agree, the prices are ludicrous, but that is just what the market is.  For example, looking for true NOS Genalex / GEC tubes, I could only find one dealer that appeared to have multiple legitimately "NOS" quads (Gold Monarch) in stock - not the "tests new"  stuff you typically see on Ebay.  And they wanted $4500 a quad.  (Although I do note there is one guy on EBay right now selling what looks to be one legit NOS quad for $2k). 

Its a simple issue of supply and demand - there just is no supply.  If you can find these tubes in quantity for half that price I'd be forking over the cash pretty quickly.

I agree with you on Tube Depot - they sold me a Mullard EZ81 that wasn't (no date codes, looked to be a Brimar).

I also completely agree with you that anyone says that the KR KT88 sound like the GEC KT88 clearly hasn't listened to them both.

"Curious, I read herein that the feedback level related to the amplifier is important to consider for purposes of evaluating whether it really makes much of a difference to tube roll power tubes. Anyone know why that would be?"

I've seen quite a few people say that tube swapping shouldn't make a difference in a high-feedback amplifier.  The theory is that high levels of feedback will pretty much swamp any small sonic differences between tube brands.  All I can tell you is that my Williamsons use the standard 20dB of feedback, which is about as much feedback as most vintage push-pull amplifiers employ, but the differences in output tubes are clearly audible to me.  Moreover, feedback cannot compensate for poorly-made tubes that produce below-rated wattage, higher distortion, microphonics and other undesirable artifacts.

I use a Denis Had Firebottle SEP "HO" (high output...heh heh) or a Pass XA-25 with very efficient speakers. Swapping between these amps and noting their differences (subtle, and both sound amazingly good) is fun. Also, the Had amp can be used with many different tubes and those differences are also interesting, leading to my drawer full of tubes. All manner of GLs...88s, 77s, 66s...all sounding a bit different...currently KT120s. 2 power tubes in that amp...that's right...2...ha. All my small tubes are NOS GEs because I like 'em...4 in my Freya preamp, 1 in the Had amp, and none in the XA-25 (I suppose I could put a tube in it but it would just rattle around) although when in use it I can look at the tubes in the Had. Another ha...

@rel LMFAO...

Curious, I read herein that the feedback level related to the amplifier is important to consider for purposes of evaluating whether it really makes much of a difference to tube roll power tubes. Anyone know why that would be?

Further, I am biamping with mc 901 monos and since the solid state part of it handles the bass drivers maybe power tubes are not that important since it appears it impacts the bass area more so.

But since I love spending so much money on everything audio even the slightest change might be worth considering. Maybe power tubes would impact the mid driver.

@emergingsoul 

Agree with @dogearedaudio - feedback does not free us from the impact of tube rolling on sound. Lessens it some - but never completely gone, in tube land!

Even if those MC 901 push bass frequencies with the SS section (really nice looking amps, btw) - most of the "music" lives in the midrange, and the sonic fingerprints of your components and tube choices will sum up and reveal themselves here. It's not just a matter of raw power; amps each have their own "sound" even when loafing  - but they'll certainly strain and sound more colored when pushed hard, so having more headroom is an asset. 

@immatthewj 

It's not just about producing max power IMO. The parallelization smooths out imperfections in each PP pair, and more importantly gives headroom at lower levels. There is an effortless sense of power, finesse and grip with my larger Master / Statement level VAC amps compared to the Signature 200iQ (to be fair there are other improvements too, besides more PP pairs & power). On a good day, the 200iQ sounded wonderful. On other days, the treble seemed a little aggressive. On others, the bass sounded either a bit lean or too loose / bloated. Even on a "bad" day, the Master and Statement amps will outperform the 200iQ's best days.