Amplifier Power tubes - important to sound?

I have quite a collection of KT88s. For my system the KR KT88 sounds best. Mainly the tone and balance top to bottom being accurate. 

roxy54

7,903 posts

08-13-2024 at 12:17am 

@emergingsoul

It’s so strange. I want to believe that your just putting us on

”your”?  “your”??

OMG @roxy54: are you OK?

Do we need a new grammar nazi???

@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...