KT120 Tryout as SE

[Cressy Snr]

I may have at least one TT21 we could plug it into one channel of your amp one day just for the heck of it. Just have to clip leed from the transformer to the top cap. I'll live with the consequences. I am not sure if I have more than one TT21 I have at least one TT22 also. If I could make a pair of 21's we could really find out how they measure up at that rating to your KT120's

If I could make a base changer to the GU50 with it's off board 12v heater supply, we could even try that? Up for it?

Sounds like a good idea to me.

[steve s]

I have a box of 354v valves , there are many different variations of these things, the early ones have large box type anodes and sound really good, the box type give way to valves with a much smaller round anode. These do not sound anything like as good as the early cossor or mullard valves.
later still came valves based on mov mh4's which sound ok, but no better than the round anode versions
Paul, those shortpath ac/hl sound very nice too, better in my veiw than the later mullards.
In my view a valves a valve.. There to be used

[Paul Barker]

Paul, those shortpath ac/hl sound very nice too, better in my veiw than the later mullards.
In my view a valves a valve.. There to be used

Oo you are a tease!

[Zekk]

First and foremost, you guys are extraordinary helpful! Thanks!

My EL802 driven TT22 operates at 550v @ 80mA using James OPT.

Dissipation is 39 watts where max is 45 watts.

This valve is tough and lasting. I've six pcs but only two pairs among the lot.
A great relic from the glorious days of the British Empire.

I'm excited about it all, and am like a kid waiting for the candy store to open for business.

Cheers!
Zekk

[Paul Barker]

First and foremost, you guys are extraordinary helpful! Thanks!

My EL802 driven TT22 operates at 550v @ 80mA using James OPT.

Dissipation is 39 watts where max is 45 watts.

This valve is tough and lasting. I've six pcs but only two pairs among the lot.
A great relic from the glorious days of the British Empire.

I'm excited about it all, and am like a kid waiting for the candy store to open for business.

Cheers!
Zekk

You are probably correct about the strength of this venerable valve.

We now live in an age where peoples exp[ectations of valve life have met with the Chionese production quality in the middle and on the whole the consumer is convinced this is how it always was.

I'll get my coat!

[Cressy Snr]

Damn, blast and buggery!

Started up the amp tonight and one of my precious Cossor 41MTL meshies has picked up an ominous, hummy, buzzy noise. Isolated it by the "noise follows valve" method and yep the valve has certainly gone noisy, no getting away from it.

Going to have to put in my Osram MH4s.

In the meantime, whilst I investigate the problem, the EL84 balanced push-pull is doing sterling service. Good job I have two amps.

[Paul Barker]

Damn, blast and buggery!

Started up the amp tonight and one of my precious Cossor 41MTL meshies has picked up an ominous, hummy, buzzy noise. Isolated it by the "noise follows valve" method and yep the valve has certainly gone noisy, no getting away from it.

In my view a valves a valve.. There to be used

[Cressy Snr]

41MTLs are not expensive, just a bit hard to find.

It's just a bit sad that one could go just like that. That however is just the nature of valves. Some last forever, others go quickly.

[pre65]

That however is just the nature of valves. Some last forever, others go quickly.

Unfortunately it also applies to people.

[Cressy Snr]

That however is just the nature of valves. Some last forever, others go quickly.

Unfortunately it also applies to people.

Yep too right Phil.

Anyway, I have replaced both the meshies with my used pair of Osram MH4 and whaddya know, the amp sounds even better....bloody fantastic to be honest. Those meshies might have been a bit weak from the get go, but that's the chance you have to take with valves as old as these.

It beats the sound I had at Owston.
This for me is more evidence that the KT120 is a remarkably neutral valve, that allows your driver valves to really show what they can do, without fuss or favour. These big, new production beam pentodes, have proved their worth, for me at least.

Now where to find some more MH4, that's going to be the problem.
AC/HLs? as an alternative you're 'avin a larf aint ya.

An old British 7 pin pentode driver would be interesting. That's probably going to be the only way of getting the required gain for a 2 stager, without spending lots of dosh, once the MH4s start losing emission.

I'm thinking long term with this amplifier, it is that good.

I've left it very late in the day (possibly too late now) though to become truly hooked on classic English small signal triodes. Oh well

[Cressy Snr]

Did a bit of investigating the innards of the amp today and found that the two parallel, 100K 0.6W anode resistors to each of the input valves were badly discoloured.
They were inadequately rated for the power being dissipated.
A bit of an oversight on my part and I can't work out how it happened
Anyway... four parallel 200K 0.6W metal films per valve later and we are now well within the power rating for the anode resistors.

It hasn't made that rogue 41MTL any less noisy, but it was worth trying them back in the amp, if only to eliminate overheated resistors as a cause of the noise.

Ah well, never mind. The MH4s are just as nice sounding, not quite as delicate at the very top but much more full bodied tone everywhere else, so the trade off is not a problem.

[Cressy Snr]

Dang it....one of my MH4s has gone noisy now.
I'm now down to my AC/P globes, which don't really have the gain but they'll have to do

My old Brit stock is looking a bit flaky.

[steve s]

Dang it....one of my MH4s has gone noisy now.
I'm now down to my AC/P globes, which don't really have the gain but they'll have to do

My old Brit stock is looking a bit flaky.

I will have some later MH4's spare Steve..you're not driving them too hard ?
Seems strange for 2 valves to go the same way...

[Cressy Snr]

Dang it....one of my MH4s has gone noisy now...

Hi Steve
Half of this deleted by mistake makes Paul's comment below make no sense Sorry I was trying to post below Pauls post and ended up editing this one.

But yes Steve It would be nice to visit your place this summer. Would be good to see the new listening room and maybe you could invite Paul to bring his uTracer.

[Paul Barker]

It would be nice to pay a visit to your place sometime this summer, maybe invite Paul round with his uTracer

Sure.