How do tubes alter sound in P12

[jimbones]

I own a pair of P12's (original not the C1 upgrade). I am using TungSol 6550's. If I were to use Kt120's how would I expect the sound to be altered? Thanks.

[AnotherJohnson]

RJ or Roberto can tell you if the power supply is up to KT120s.

There are no KT120s to be had right now. Supply has dried up. May change later this summer. Or not.

If you could find them, and if your amp can support them, they may give you cleaner tighter bass with no lessening of the other aspects. RJ will have a detailed description.

[Big Dog RJ]

This very topic of changing from 6550's to KT120's has been covered in several threads under the Amplifier tabs. Just go through any of those and there's a wealth of info.

I wouldn't say that the KT120's are better, although on specs they're superior tubes. The character of the KT120 is such that it sounds fuller, more extension on the full freq spectrum. However, there are many who prefer the original 6550's and specifically the 6550C. The winged-C comes from the SED factory (Svetlana electron devices), Russian origin but was made in one of the US factories. It is a fantastic tube and one of my favourite 6550's.

The other thing you have to consider before making the change is the type of speakers you're using and the overall preference of sound. The 6550's may seem to be the perfect choice to your existing speaker system. Adding KT120's may overdo things...

I'm afraid with this type of tube, only YOU can decide which one suits you.
Cheers, RJ

[jimbones]

Thanks guys. I currently have both TungSol and Winged C. I dont remember hearing much difference when I went from Wing C to TS.
I dont think its worth the change to the Kt120. (BTW I spoke with CJ and they said I could use them.) Previously they said no so that is a bit concerning that they would give mixed answers.
A buddy of mine swears by the Kt88 as his favorite.

[roberto]

Hola jimbones,

Well, certainly people is entitled to have its own preferences and liking. Me, I never will go back to the 6550s(C) having the KT-120. To my ears and liking, I have much better bass control, making it tight and very well reproduced. There are musical notes with a deepness when the musician uses this on his bass, that I never got this with the 6550s. Also, my power amp, (Classic 120SE) came from factory with them. Before I had an ARC VT200 MKIII mod. using the KT120s too. The stage is wide and presents a steady musicians. The image is great. The highs are the quality of Conrad Johnson pureness. Clear and crystal highs with a harmonic texture that I never had before. The definition of the musical instruments and voices are just right. I do believe too that all tubes are important, and I am using the signal tubes made by Genalex, Gold Lion, gold pins.

It is important to understand that what I like not necessary must be your liking. I use the analogy of food as an example:
Some people like garlic, others hate the garlic...but the plate is delicious. So, my recipe with tubes might not be for everyone, the important thing here is that I am in Heaven. I don't want to change nothing. I am very, but very pleased with my sound quality and what I am hearing now. I am rediscovering all my music. The harmonic texture is fantastic. You can understand while listening to a pianist, what the left hand is doing vs the right easily. Also, the voices are projected to the space with such realism that I get goosebumps very often. Easy to understand the fun that the musicians are having while playing together.

Happy listening!

[Wildcat]

My Premier 11 is nearly the same circuit as the P12 and P8, and I bought KT120s when I first purchased it. The GE 6550s and other tubes were tired, likely the factory originals (based on the history the second owner gave me, as the original owner was a family friend). I mainly read about the improved bass like @roberto mentions above, and I haven't felt as though anything is lacking after several years of listening. When I had the amp in for service, Bill had me send along the tubes I intended to use so that when he ran through adjustments, they would be based on those particular tubes.

I only wish that the power output of the amp could have been increased to use more of the KT120s capabilities, but that would have required modification from a stock P12 (which I don't want to do, as I feel it decreases the value), and likely would have shortened tube life. As these aren't driven hard, I used my first set for many years before I needed to send the amp in for service. So I am running my newer set, but the older set is a good backup.