The Canadian Guitar Forum banner

1 - 10 of 10 Posts

·
Banned
Joined
·
153 Posts
Discussion Starter #1
DO the new JCM 800 reissues sound as good as the Older 70's JCM 800 Master MKII's. If the difference is minimal, thats ok too. Man, guoitar center had these babys cleranced out for like 1200.00 the other day. They wrere gone inn a flash, and I missed it. Poor me.
 

·
Registered
Joined
·
1,909 Posts
I would think that if you watch around, you could find an original in that price range, either a (70s) JMP or a (80s) JCM800.

I missed a 50 watt JMP the other day at $950, in the bargain finder.

I think the originals would be better investments over the long term too.
 

·
Registered
Joined
·
1,909 Posts
awesome, did it fit your budget?
 

·
Banned
Joined
·
153 Posts
Discussion Starter #7 (Edited)
Its the 100 watt model.Its in excellent condition , but its been recapped.I see black JJ [email protected] +10 +30. Are these good caps?Also,It is all original,except I just noticed, I think the original 6550's have been changed to EL34's. I think this is true because the tube reatiners are for 6550's and they are too big for the EL34's.The amp seems to run hot, and I dont know whats going on.I dont know if thats normal or not. Probably time to have a tech make certain its biased correctly.Is there something involved to change tubes from the 6550's to the EL34's and back? thanks P.S. I paid 700.00 U.S. I wouldve been a lot happier to pay 650.00 but was afraid to lose it. I dont know now though about those tubes. Now Im broke for a few months.
 

·
Registered
Joined
·
1,909 Posts
I'd think you'd want to leave the 34s in there. That's where you're going to find the British Marshall sound.
If you think it's running too hot, yes, have a tech check the bias on it. On a used head, it's good insurance to have your tech give it a good once over anyway.
I'm pretty sure I've read the JJ caps are good.

I think you stole it for that price.
 

·
Registered
Joined
·
52 Posts
gerald guerrero said:
Its the 100 watt model.Its in excellent condition , but its been recapped.I see black JJ [email protected] +10 +30. Are these good caps?Also,It is all original,except I just noticed, I think the original 6550's have been changed to EL34's. I think this is true because the tube reatiners are for 6550's and they are too big for the EL34's.The amp seems to run hot, and I dont know whats going on.I dont know if thats normal or not. Probably time to have a tech make certain its biased correctly.Is there something involved to change tubes from the 6550's to the EL34's and back? thanks P.S. I paid 700.00 U.S. I wouldve been a lot happier to pay 650.00 but was afraid to lose it. I dont know now though about those tubes. Now Im broke for a few months.

The only thing about 6550 and el34 is you have to re-adjust your bias line voltage (on the board) and sometimes you don't even have too as long the bias voltage is within range of the tube. El34 are rated at 25w and a good rule of thumb is to use 60%-70% of it's "plate dissipation power", so around 16-17w from the tubes would be the target with el34s.

Ex.

EL34 plate dissipation = 25 watts
25 watts divided by plate voltage = plate current
plate current x 70% = desired mA

so if:

25 divided by 390 (plate voltage) = .064 [64mA is your plate current]
64 x .70 = 44.8mA

You can also go by taste, use your ears......
 
1 - 10 of 10 Posts
Top