JVM 410 mild tubes?

[avspecialist]

Todays experiment. I ended up with:

V1: JJECC 83s
V2: TAD 5751
V3: JJECC 83s
V4: Tung sol 12AX7
V5: TAD E83CC

The gain is lower with good crisp on the high end. I can acctually bring upgain to 5 on OD1 and orange mode without sounding mushed. So much better than stock tubes.

I hope your tune roll gives you what you were hoping for. Over the last 9/10 years, I went through a lot of preamp tube rolls based on the findings of some really smart members of the JVM forum. For me trying a wide variety of tubes from my stock of RCA’s, Telefunkins, GE, Sylvania and CP tubes like Tungsol, Millard EH to name a few, I was able to alter things, but not in the way I was looking for. I’m somewhat handy and not used to working on PC boards, but I did 3 simple mods, variable negative feed back mod, R97 mod, R128 mod, these loosened up the amp quite a bit and made the red and yellow gain much more manageable. The biggest change to my surprise was taking out the 4 JJ EL 34 and installing 4 of the Preferred Series EL 34’s. I believe with a plate voltage of 457 and a bias on on set at 81Mv and 79/80 my on the other set the amp really came to life. Basically a slight imbalance in the output tubes add more 2nd harmonic distortion. It’s really that good. I will have to say the speaker choice is another contributing factor. I recently compared my 1960A with 4 Creamback 65 to my 1960B cabinet that has 4 Celestion G1275T in it. With the Creambacks being used the amp is exactly what I was looking for. The amp is quiet and very balanced in all modes. When I switch to the G1275T, the amp is very noisy, feedback prone and just harsh and bright, really terrible. I goes to show that trial and error can go a long way.

 

[Raimo]

I hope your tune roll gives you what you were hoping for. Over the last 9/10 years, I went through a lot of preamp tube rolls based on the findings of some really smart members of the JVM forum. For me trying a wide variety of tubes from my stock of RCA’s, Telefunkins, GE, Sylvania and CP tubes like Tungsol, Millard EH to name a few, I was able to alter things, but not in the way I was looking for. I’m somewhat handy and not used to working on PC boards, but I did 3 simple mods, variable negative feed back mod, R97 mod, R128 mod, these loosened up the amp quite a bit and made the red and yellow gain much more manageable. The biggest change to my surprise was taking out the 4 JJ EL 34 and installing 4 of the Preferred Series EL 34’s. I believe with a plate voltage of 457 and a bias on on set at 81Mv and 79/80 my on the other set the amp really came to life. Basically a slight imbalance in the output tubes add more 2nd harmonic distortion. It’s really that good. I will have to say the speaker choice is another contributing factor. I recently compared my 1960A with 4 Creamback 65 to my 1960B cabinet that has 4 Celestion G1275T in it. With the Creambacks being used the amp is exactly what I was looking for. The amp is quiet and very balanced in all modes. When I switch to the G1275T, the amp is very noisy, feedback prone and just harsh and bright, really terrible. I goes to show that trial and error can go a long way.

Yes I beging to think the cab with G1275 is not the best cab for this amp.

 

[avspecialist]

Ramiro: I truly believe the G12T75’s really do not go with the JVM, and possibly a lot of other Marshall’s. So far the only amp that seemed decent with the G12T75 i’d my 94 Twin Amp. It’s basically a very dry amp without a lot of upper mids. It does bring out the noise in that amp also, but to a lesser degree. To me the Celestion Creamback 65’s, are an excellent match if you are using all of the preamp channels. My music is from Beatles to Black Sabbath and I can really get those sounds dialed in.

 

[MatFnEhUK]

I'm finding my new JVM205H a little fizzy on the OD orange and red modes. I don't think it's my speakers (4x12 with v30's and g12 heritage), because they sound great and non-fizzy with my other amps. And I've tried multiple suggestions for dialing in the amp but the fizz is still there, at least at lower volumes. I recently tried a Tungsol 5751 in v1 and it definitely helped with the fizz, but maybe not quite enough. Before I do anything else I will take the amp to a tech to get the bias checked because it may have come from the factory too cold, but if that doesn't work is it worth trying a second 5751 for the v2 position to smooth out both gain stages? Has anyone tried that yet?

EDIT: got the bias checked and the tech said it was fine, no adjustment needed. What I ended up with was Tungsol 12ax7s in all positions except v3 (Chinese 12ax7), Tungsol 5751 in v1. Fizziness is no longer a problem on the OD orange/red modes and I’ll probably be sticking to this config. Loving how it sounds now.

 

[Raimo]

Yes, tried it in the V2 and the gain lowered a bit, that was my goal. For me a TAD E83CC calms it down in the first position.

 

[MatFnEhUK]

Yes, tried it in the V2 and the gain lowered a bit, that was my goal. For me a TAD E83CC calms it down in the first position.

Cool, I like the e83cc in gainier amps, but what I meant to ask was, has anyone tried 5751s in both v1 & v2 simultaneously?