KT 120 valves

[Lee Henley]

I've been using Tungsol 6550's which replaced my GL KT 88's, I've been told I can roll in some 120's, is there much benefit from this, would I gain much?

Lee

[John]

Speak to either Marco or Anthony TD

[Marco]

Hi Lee,

Don't do anything until you find out if the mains transformer in your amp is up to the job of handling the higher current demands of the KT120s, or you could end up in a whole world of grief....

I would contact Anthony TD, via his website: http://www.tubedistinctions.co.uk/contact_info.htm where he will be able to advise you further :)

Marco.

[Rare Bird]

Hi Lee,

Don't do anything until you find out if the mains transformer in your amp is up to the job of handling the higher current demands of the KT120s, or you could end up in a whole world of grief....

I would contact Anthony TD, via his website: http://www.tubedistinctions.co.uk/contact_info.htm where he will be able to advise you further :)



http://www.tubedistinctions.co.uk/kt88.htm

[Lee Henley]

I have already checked with the manufacturer and he said it was fine to use KT 120 valves

[Marco]

In that case, Lee, then go right ahead. Much will depend, however, on how well the circuit in your amp will take advantage of the increased power available from KT120s.

For best results, I would send it to someone like Anthony, who will look at your amp and make any necessary small adjustments, to ensure that you get the most out of the KT120s you install.

If you haven't read this bit from his website, check it out:


The new KT120 is a very good replacement for a lot of power amps using either KT88 or 6550, however, I must stress that it is not identical in electrical parameters and therefore there are some important diffrences to consider i.e. they will take a little more current from conventional AC heater supplies [average is around 100ma once valve has settled] which for high quality well made equipment, is usually not a problem, yes, you may find that the mains transformer will run a little warmer etc.

Also, the bias supply usually will need careful adjustment to exactly match the same steady state current as a KT88, however, with the KT120 having a considerably higher anode/plate dissipation of 60 watts compared to even the highest available KT88 [Original Svetlana winged C of 42 watts] it can be clearly seen that the KT120 when run as a direct replacement for KT88 and 6550 will have seemingly a much easier life.

Bearing the potential higher power dissipation in mind, some amplifiers [mainly grid biased] can indeed be tweaked to produce even more power without getting anywhere near the maximum plate dissipation of the KT120.

If you have a [conventional] cathode biased amplifier, care must be taken to make sure that the bias resistor values and wattage fitted for KT88 do not allow the KT120's to draw excessive current which could indeed lead to premature failure of the valve and equipment. On a positive note then, excellent results can be achieved using the new KT120 valve, but certain tests and precautions should be adhered to before doing the swap over, if your not sure then either consult your equipments manufacturer or a qualified technician for advice.


For example, is your amplifier grid or cathode biased? That factor alone will significantly influence the results you obtain from fitting KT120s :)

Marco.

[Lee Henley]

Couldn't resist anymore ordered a set today, should be here in a few days time, if these do the trick then a quad set of 6550's will be up for sale soon 😊

[Lee Henley]

KT 120's now up and running, very nice, looks like my 6550's are going to be up for sale, defiantly an improvement in the width of the soundstage, bass is a lot more controlled which I think is probably contributing to clearer mids. Gonna need more listening, oh well it's a hard life 😊

[Marco]

Nice one, Lee. For me they are without doubt the best power valves available (for push-pull amps) - WAY better than KT88s (even the fabled GECs) and piss all over 6550s!

They don't cost the earth either. If you fancy a further upgrade, get them cryo-treated. Trust me, the sonic improvement is almost as big again as the one you obtained by going from 6550s to KT120s... ;)

Enjoy :)

Marco.

[worrasf]

If you fancy a further upgrade, get them cryo-treated. Trust me, the sonic improvement is almost as big again as the one you obtained by going from 6550s to KT120s... ;)

Enjoy :)

Marco.

Hi Marco
I seem to remember a post some time back where you recommended a firm to cryo valves but I may be mistaken. Like you I am very impressed with the KT120's that are now in my Croft S4s - it needed a bit of "Glenn tweaking" to get them running smoothly but they sound super. I was now thinking of giving them the cryo treatment (rather than buying a whole new quad of pre-treated valves) so would apreciate any recommendations where I could get them frozen.

Steve

[Jimbo]

Interestingly although not in the same league as your valve amps I did find even with my Croft 25R pre I tried a bit of tube rolling and found that the cryo valves were better even than NOS Mullards. I swapped them out and found that the cryo treated valve was indeed much better.

[TheMooN]

A-N other manufacturer enters the game ~ http://psvanetube.com/wordpress/store/products/kt-120-quad/