What Tubes Can I Use?

[Leo_Gnardo]

What's your plate voltage?

Post 58 says 450V. No worse than some Deluxe Reverbs I've run across. Try some tough JJ's, or old RCA or Sylvania as Jim Kelley suggested for his 500V B+ amps. Bias accordingly at, hmm 20 mA or so, who knows might be the bees knees. Worst that could happen is, nahh this isn't for me...

[gtrplayr1976]

What's your plate voltage?

450

[gtrplayr1976]

Post 58 says 450V. No worse than some Deluxe Reverbs I've run across. Try some tough JJ's, or old RCA or Sylvania as Jim Kelley suggested for his 500V B+ amps. Bias accordingly at, hmm 20 mA or so, who knows might be the bees knees. Worst that could happen is, nahh this isn't for me...

I have a set of new JJs ,and some vintage ,but don't remember what they are. I'll have to look. I'm game for trying anything to see how it sounds.

[Leo_Gnardo]

I have a set of new JJs ,and some vintage ,but don't remember what they are. I'll have to look. I'm game for trying anything to see how it sounds.

The ones I mentioned oughta work at 450V. I'd beware of some of the delicate 6V6 versions like Visseaux & Mazda, they don't like living much beyond 300V.

[Helmholtz]

I'm using JJ KT77s. Specs look the same as KT66 if I'm not mistaken?

No, specs are different. Unfortunately JJ never publishes comprehensive tube data and doesn't specify the rating system. But especially KT77s and EL34s have higher transconductance (gm) values than KT66s. In conjunction with the strong NFB of the JTM45 this may support oscillation issues.

To my knowledge Marshall choose the 8k impedance to suit KT66s. While it has been reported that JTM45 prototypes used 5881s and maybe 6L6s (with a different OT), I think that most production amps were equipped with KT66s. So these are part of the classic JTM45 sounds.
I like mine best with original GEC KT66s.

Rather than use unsuitable power tubes I would experiment with different feedback ratios and speakers.

[gtrplayr1976]

The ones I mentioned oughta work at 450V. I'd beware of some of the delicate 6V6 versions like Visseaux & Mazda, they don't like living much beyond 300V.

I think the vintage ones I have are Philco ,RCA ,or Sylvania. I really didn't think these would handle the plate voltage? I know the JJs should since they aren't really made like the old 6V6s.

[Leo_Gnardo]

I think the vintage ones I have are Philco ,RCA ,or Sylvania. I really didn't think these would handle the plate voltage? I know the JJs should since they aren't really made like the old 6V6s.

About 5 years ago, we had a go-round at The Amp Garage concerning Jim Kelley amps. Darn good amps! They were all the rage in the late 70's for a while. Bonnie Raitt & Jackson Brown snapped up theirs, seen playing them onstage. Jump ahead to 2014, I've worked on a couple, but their bugaboo was they ran a quad of 6V6 with a B+ of 500V. This matter came up on TAG and who popped up but Jim Kelley himself. With the recommendation that those who want their tubes to not turn into fireworks displays had better score NOS RCA or Sylvania 6V6. I'd trust the word of the man who made the amps. Seems JJ can keep up with the high voltage spec too. With that in mind I made my recommendation. Should be OK in your 450V amp. Don't be surprised if that B+ rises a bit, as you'll need only 20 mA or so to run your V's.

Philco... I dunno if they made their own tubes and how much guff they'll put up with. Chances are good Philco are re branded tubes made by another manufacturer, with Philco logos painted on so owners of Philco radios & TV's could feel safe using the "proper" brand in their sets.

[gtrplayr1976]

About 5 years ago, we had a go-round at The Amp Garage concerning Jim Kelley amps. Darn good amps! They were all the rage in the late 70's for a while. Bonnie Raitt & Jackson Brown snapped up theirs, seen playing them onstage. Jump ahead to 2014, I've worked on a couple, but their bugaboo was they ran a quad of 6V6 with a B+ of 500V. This matter came up on TAG and who popped up but Jim Kelley himself. With the recommendation that those who want their tubes to not turn into fireworks displays had better score NOS RCA or Sylvania 6V6. I'd trust the word of the man who made the amps. Seems JJ can keep up with the high voltage spec too. With that in mind I made my recommendation. Should be OK in your 450V amp. Don't be surprised if that B+ rises a bit, as you'll need only 20 mA or so to run your V's.

Philco... I dunno if they made their own tubes and how much guff they'll put up with. Chances are good Philco are re branded tubes made by another manufacturer, with Philco logos painted on so owners of Philco radios & TV's could feel safe using the "proper" brand in their sets.

There should be a code on the tube that might tell me who exactly made them. If I'm not sure ,I'll just go with the JJs to be on the safe side.

[gtrplayr1976]

According to this 312 code they are Sylvania (Hygrade Sylvania Corp)

[Leo_Gnardo]

According to this 312 code they are Sylvania (Hygrade Sylvania Corp)

There you go, good research! Now to try out some V's - I expect you'll get 15-20 watts power. But will the tone be to your liking? Only one way to find out...

[gtrplayr1976]

There you go, good research! Now to try out some V's - I expect you'll get 15-20 watts power. But will the tone be to your liking? Only one way to find out...

We will see. It sounds better to my ears just since removing the MV ,changed the screens to 470R instead of 1k I had in there. Have a slight 60hz hum that I heard before I even did this. I will find that after I get the tubes I want.

[gtrplayr1976]

There you go, good research! Now to try out some V's - I expect you'll get 15-20 watts power. But will the tone be to your liking? Only one way to find out...

Hey, Not bad! I have options.