2204 el34 recomendations?

[Tone Slinger]

Funny, but I've had WAY different results with tubes than what has been stated above. Right around '02-'06 I went through SEVERAL different 2204 and 2205 JCM 800's.

Here is what I found,


The Svetlana was very 'soft' sounding, with undefined bottom end. Great warmth and tone, but sorta 'mushy'.

I had a pair of old chinese el-34's, labeled 'HARD ROCK'. These were slightly bigger el-34's, like the JJ E34L's. They were labeled as El-34/6CA7, because of this heftier construction, though true 6CA7's they were not.

These were tighter, but had a fairly 'flat' response, not as warm as the Svet's.


I put a new pair of the JJ E34L in. These seemed a little better than the Chinese, with a bolder bottom end, very tight and sort of lower mid emphasis. Still, sort of 'flat' in tone compared to the Svet's. But not bad.


I threw a pair of 6CA7 EH in there (true 6CA7 design) and the sound was very full, tight, with great articulation. Not as warm as the Svet's though.


My FAVORITE tube in this amp overall, was the EH EL-34 ! This tube made the amp perform like how I remembered them sounding in the late '80's, fresh off the line (was Marshall using the Sovtek/EH tubes then ?) They werent quite as 'open' sounding as the Svets, but they had, bar far, the BROWNEST tone of them all. Palm mutes had sizzle, and muted low E pedal tones held togather. They had the best 'voice' with this amp.

Some think that the reissue 'MULLARD' is the same tube as the EH because they are made in the same factory, but they are not. The regular EH is better (and cheaper).

[Roe]

Cs, RFTs or real xf2s

[jtunes]

Got some RFT's Ill let you know how things go....

[erikdegroot]

I modded my 4104 JCM800 2x12# as follows:

C7: 22n -> 2n2 reduce low end distortion when preamp volume is 3/4 and more
R11 470K -> 1M more gain
R15: 33K -> 39K slope resistor for more oomph
R22*: 100K -> 47K feedback resistor for more negative feedback = less poweramp distortion; EL34 sound harsh
Change negative feedback wire from 4 ohm to 8 ohm tab for more negative feedback (see above)
Add 100nF cap between 8 ohm feedback tab and R22* to control low-end rumble
R18: 82K -> add 120pF cap in parallel to reduce harsh high end
R21: 100K -> 91K + 120pF in parallel to reduce harsh high end
C18: 47pF -> 75pF (2x150pF in series) to reduce harsh high end

I replaced all of the 470pF ceramic caps with 2x1nF Mallory150's in series (to reduce harsh high end of the ceramic caps)

(If more of a lead sound is preferred than add a 2.2uF cap in parallel with R9 820R).

This gives the amp a wonderfull controlable EL34 rock-tone without the harshness.