Line Amp - Power Tubes?

Mojo

Mojo

Member
I’ve been scared about using other than JJ 6V6S or JAN Philips 6V6GT in my Line amp, which runs 460PV. I’ve been holding off trying some RCA black plate VT-107A’s (which I’d love hear) out of fear that I’ll damage the amp. What might I do expect to be the outcome? Tube damage? Amp damage?
 
In general rca tubes aren’t as durable as Philips Sylvania. Hence the JANMIL spec.
Which came later in the late 60s if I recall
For clarification. JAN MIL stands for Joint Army Navy Military. Many people know it’s a “mil” spec tube however, not everyone actually knows the acronym. Jim has been through a lot of these tubes over the decades. His preference is the sylvanias and or JJs. Philips works to as long as Jan Spec. Sylvanias typically don’t even need to be Jan is they are early to mid 70s green label. If I recall there may have even been a period of time where he used GE. I may even have some labeled Jim Kelley. But again, his preference is Sylvania/Philips and JJs.
 
Voodoosound said:
In general rca tubes aren’t as durable as Philips Sylvania. Hence the JANMIL spec.
Which came later in the late 60s if I recall
For clarification. JAN MIL stands for Joint Army Navy Military. Many people know it’s a “mil” spec tube however, not everyone actually knows the acronym. Jim has been through a lot of these tubes over the decades. His preference is the sylvanias and or JJs. Philips works to as long as Jan Spec. Sylvanias typically don’t even need to be Jan is they are early to mid 70s green label. If I recall there may have even been a period of time where he used GE. I may even have some labeled Jim Kelley. But again, his preference is Sylvania/Philips and JJs.
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I think they all sound great (the JANMIL, Sylvania, and JJs), but it's a testament (to me) of what a genius Jim is at circuit design that I really can't tell a ton of difference in the Line circuit with those tubes. Not that my ears are the greatest in the world, but i think they all just sound wonderful.
 
beckstriad said:
I think they all sound great (the JANMIL, Sylvania, and JJs), but it's a testament (to me) of what a genius Jim is at circuit design that I really can't tell a ton of difference in the Line circuit with those tubes. Not that my ears are the greatest in the world, but i think they all just sound wonderful.
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It’s worth stating that Jim chooses tubes for their power handling capabilities. Some tubes just simply don’t make the cut. At some point I’m hoping he comes here to clarify. I’m not trying to speak for him just offering info based on conversations I think I am remembering correctly :)
 
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Thanks for your comments. The RCA’s I have are U.S. Army Signal Corps VT-107A’s from Jan 1958. I have read mixed interweb comments about them versus other 6V6GT’s, so I thought I’d inquire here to see if there was any experience among this group. I don’t want to harm the amp by doing something foolish as you might imagine, so I’ll hold for now.

It would be great if Jim were to drop in here!
 
I have a bunch of quads for the line amp. I have 3 quads of the Sylvania. They are all low current draw. I also have a quad of Bendix, a quad of JAN Phillips that I got from Jim, and the quad of new production tung sols that came in my amp at the time. They all sound good. Some sound great. I think the Sylvanias are the most scooped and I might like them the best. Maybe I will do a comparison video one weekend.

I think the key here is that the amp has pretty high plate voltage - 477 as per Jim. Higher current draw tubes wont last as long in the amp. When I bias in the Sylvanias I can get them to 18mA maximum and run them around 15.3 or so. The JAN could go to 33mA at the maximum setting and I am running them under 20 if I remember correctly.

I would be interested to see what those RCA's run at when you put them in. They could be fine.

I generally keep the Sylvanias in for gigs because all the quads are about the same and if anything goes wrong I can just throw in another 6V6 and it will match.
 
Thanks for that. I hope Jim will chime in as well.

I have to say that I love Sylvania preamp tubes. I haven’t tried many different power tubes in the Line (or other Kelley amps), but have been really pleasantly surprised how great everything sounds.
 
smazz said:
I have a bunch of quads for the line amp. I have 3 quads of the Sylvania. They are all low current draw. I also have a quad of Bendix, a quad of JAN Phillips that I got from Jim, and the quad of new production tung sols that came in my amp at the time. They all sound good. Some sound great. I think the Sylvanias are the most scooped and I might like them the best. Maybe I will do a comparison video one weekend.

I think the key here is that the amp has pretty high plate voltage - 477 as per Jim. Higher current draw tubes wont last as long in the amp. When I bias in the Sylvanias I can get them to 18mA maximum and run them around 15.3 or so. The JAN could go to 33mA at the maximum setting and I am running them under 20 if I remember correctly.

I would be interested to see what those RCA's run at when you put them in. They could be fine.

I generally keep the Sylvanias in for gigs because all the quads are about the same and if anything goes wrong I can just throw in another 6V6 and it will match.
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Thanks for sharing! I’ll report back when I get a chance to check them out..
 
Update: won’t be proceeding with trying the RCA’s in-circuit as i don’t have enough good tubes to populate the amp. I tested tubes on my tester had tubes that were positive for shorts.. Glad I at least checked before trying and likely frying components!
 
Mojo said:
Update: won’t be proceeding with trying the RCA’s in-circuit as i don’t have enough good tubes to populate the amp. I tested tubes on my tester had tubes that were positive for shorts.. Glad I at least checked before trying and likely frying components!
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Yes, that is one amp you definitely don’t want to release the magic smoke.
 
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