Tube question JMP1 head for SteveD

[pleximaster]

Hi SteveD!
You know I love your amp! I just picked up my second JMP1. I bought it to have two with different mix tubes to get variations of the sound I love in these babies. I haven't change tubes in any of them yet (in fact I haven't bought the tubes yet!) when I compared the two there is a considderable difference in brightness of the two. They are from the same batch and one of them I had for about two and a half weeks. The new one is very much brighter and I have to roll of the treble quite a bit. The "old" one is much darker and not as clear as the new one. When I play these I play them hard. The change in sound is quite different much more dramatic then breakin in a 50 or a 100 watter after tube change. Will this change continue and what is the expected lifespan of tubes in these amps? What tubes are stock in these amps?

Best plexi

[surfnorthwest]

Steve addressed this in a earlier post. I know he is on his way to the MusikMesse show in Frankfurt this next week for the JMP1 launch so he will probably be absent from here for a bit.

Parallel single ended (Class A)

The amp will actually function with the following output configurations albeit with varying degrees of distortion and tonal character; -

A pair of ECC81s (12AT7) - stock production format
A single ECC81
A pair of ECC82s (12AU7)
A single ECC82

All of these amps sound great IMHO and would make a killer 'sonic tool kit' for any player!

[pleximaster]

Thanks Surf!
Sorry I wasn't clear about which tubes were stock, I meant which brand of tubes.

Best regards plexi

[Doc Holliday]

Are they jjs and shuang? I had a jj in the first position in my jtm1 . Can I change the ecc82 tube in that amp without a rebias?

[surfnorthwest]

I think they are a Shuguang, no way does a JJ sound that good.

[SteveD]

Steve addressed this in a earlier post. I know he is on his way to the MusikMesse show in Frankfurt this next week for the JMP1 launch so he will probably be absent from here for a bit.

Parallel single ended (Class A)

The amp will actually function with the following output configurations albeit with varying degrees of distortion and tonal character; -

A pair of ECC81s (12AT7) - stock production format
A single ECC81
A pair of ECC82s (12AU7)
A single ECC82

All of these amps sound great IMHO and would make a killer 'sonic tool kit' for any player!

See my new post for an expansion on the above info; -

http://marshallvintagemodern.com/viewto ... 374#p83374

[SteveD]

Hi SteveD!
You know I love your amp! I just picked up my second JMP1. I bought it to have two with different mix tubes to get variations of the sound I love in these babies. I haven't change tubes in any of them yet (in fact I haven't bought the tubes yet!) when I compared the two there is a considderable difference in brightness of the two. They are from the same batch and one of them I had for about two and a half weeks. The new one is very much brighter and I have to roll of the treble quite a bit. The "old" one is much darker and not as clear as the new one. When I play these I play them hard. The change in sound is quite different much more dramatic then breakin in a 50 or a 100 watter after tube change. Will this change continue and what is the expected lifespan of tubes in these amps? What tubes are stock in these amps?

Best plexi

The speaker alone can account for sonic differences in sound especially during break in periods as can valves. It's also a fact that any position on a pot except maximum or minimum cannot be compared like for like as the tolerance of these components is not good enough. Rarely do two valve amps even from the same range and model type sound the same but please allow some settling in.

The valves should last quite a while if they are decent brands. Shuaguangs are in the output positions on the JMP. As always it's difficult to predict with valves and you may get weeks, months or even years depending on how robust the ones in your amps are as well as how you use those amps.

[pleximaster]

Thanks a lot Steve!

Can I just pop the tubes in or do I have to rebias?

I played them more today and I must say they are such great tonemasines, just Ilike my old 50 watters. But at reasonable volume. . All my old amps sound of cause a bit different even though same year. I thought newer amps were more similar. I kind of dig that they sound a tad different, both sound really sweet. But this means I might have to find yet another JMP1 cause it might be even sweeter... :)

I bought the YJM for the reason I needed plexi tone at low volumes, but I fiend it to be best used live with controllable levels. The 1 watter series really is what I have been waiting for.

Best plexi

[surfnorthwest]

Rarely do two valve amps even from the same range and model type sound the same but please allow some settling in.

This is very important for all of us to always keep in mind, I agree with this. It is why I will never sell my VM or TSL 100. I got good ones.

Crap, it may be another month before I see my JMP1.

[SteveD]

Can I just pop the tubes in or do I have to rebias?

Just replace the valves in the configurations I have suggested. No need to rebias as the JMP-1watt is cathode biased.

[Doc Holliday]

I'm thinking of popping in some mullard ecc81's in the power section
On the jmp when I receive it. Will I see a drop in gain in comparison to the stock power valves?

[surfnorthwest]

I'm thinking of popping in some mullard ecc81's in the power section
On the jmp when I receive it. Will I see a drop in gain in comparison to the stock power valves?

Perhaps a touch but doubt it will be very noticable. I have a rather large box of all sorts of tubes from the years of trying this tube and that tube. Many I over bought just to have spares so experimenting will be easy.

For me when my JMP1 comes in I will see how it sounds stcok and if it hits the mark I will leave it alone. I would like to retube the JTM1 to give it less gain and more clean power. Also I want to retube my Class 5 head to give me less gain and more clean power. Both amps have more gain on tap then I use.