valve question - 6CA7 varieties

[Uk Ant]

I'm thinking about trying some 6CA7's in my little JCM900, just for a change really.
Now Electro harmix do them and they come in Cool (early distortion), medium (normal distortion) and Hot (late distortion).
Anyone with experience of these who could tell me how these different types actually sound?

[TwilightOdyssey]

Are you pushing your amp into power valve distortion? If not, then they will not matter ...

[gibson175]

i had some 6ca7s....eh ones too....but i dont know about the early/late stuff. I just biased them up and they sounded way better than the 30 year old phillips ones that were in the amp.
I like em. I reckon if i was using el34 based amps again, id prolly use 6ca7s when it was time for a retube. I reckon they give a little more headroom (read:bass) than el 34s.

[Soulcrusher_X]

JJ also makes 6CA7s. Ive never heard them, but I do like a lot of the JJ power tubes. A lot of guys and gals like 6L6s in their 900s also.

From what I know of JJ power tubes at least that you could easily bias up in your 900, the range of tubes from least to most headroom and full low end go from EL34 - E34L - KT77 - 6CA7 - 6L6

[Lake Placid Blues]

Are you pushing your amp into power valve distortion? If not, then they will not matter ...

But the cleans of different tubes can sound different too. I can hear it in the same amp.

[Lake Placid Blues]

I'm thinking about trying some 6CA7's in my little JCM900, just for a change really.
Now Electro harmix do them and they come in Cool (early distortion), medium (normal distortion) and Hot (late distortion).
Anyone with experience of these who could tell me how these different types actually sound?

You may not be able to bias 6CA7s in a 900 though. I tried 6CA7's in place of EL34s in one amp (not a 900) to get a deeper clean but I would of had to mod the bias ciruit to get them into a safer zone. They sounded good but I was afraid they wouldn't last very long run that hot. They went right into another amp. They sound like EL34s, but with more bottom.

[Uk Ant]

You may not be able to bias 6CA7s in a 900 though. I tried 6CA7's in place of EL34s in one amp (not a 900) to get a deeper clean but I would of had to mod the bias ciruit to get them into a safer zone. They sounded good but I was afraid they wouldn't last very long run that hot. They went right into another amp. They sound like EL34s, but with more bottom.

Yeh, there's a long thread on the marshall forum about these valves (most of which is a bit over my head) and there seemed to be many people who found they just didn't last very long in JCM2000's. I suspect the 900 and 2000 power sections are pretty similar so the longevity of the valves is a concern.
I do like the sound of more bottom so I may give a try.

[TwilightOdyssey]

But the cleans of different tubes can sound different too. I can hear it in the same amp.

Oh, I agree. But the difference is not so great as to influence a purchase decision. If you are pushing the amp to power valve distortion then the breakup point becomes a much more important criteria.

[Lake Placid Blues]

Oh, I agree. But the difference is not so great as to influence a purchase decision. If you are pushing the amp to power valve distortion then the breakup point becomes a much more important criteria.

Agreed.

[Lake Placid Blues]

Yeh, there's a long thread on the marshall forum about these valves (most of which is a bit over my head) and there seemed to be many people who found they just didn't last very long in JCM2000's. I suspect the 900 and 2000 power sections are pretty similar so the longevity of the valves is a concern.
I do like the sound of more bottom so I may give a try.

The main issue is the range of bias voltage on some amps. If you can get the range of the bias so that tube isn't running too hot and sounds how you want it to, then its a good swap.