My 2204 need some mods for that 80's rock tone #Dokken#Ratt#TNT

[Kennetiversen]

Hi there!

I have a 2204 ptp that i would like to mod. Right now I feel the amp is a little to spongy and lacks some clarity. I need to tighten it up a bit.

I'm playing it thru a 2x12 marshall cab with g12h 75 creambacks.

Last night i listened to some Friedman BE-100 clips on YT and damn that thing sounds good.

Anybody got a BE-100 schematic or other mod tips they would like to share?

[mixn4him]

Easy, the tight punchy bass is the fixed resonance setup. 220k resistor in parallel with a .0047 cap, this is after the Feedback resistor and into the speaker impedance tap. Dave currently is doing a 47k FB resistor and on the 4ohm tap.

More gain is easy too, finally settled on this recipe on my 2204. V1 plate 330k, remove the 470k/470pf from low input jack to gain pot and replace with 68K resistor. Also add a .68cap across the 820 resistor of V2. Stop listen and decide..

If that's not enough gain lower the cold bias V1b 10k to 6.8k or 4.7k OR full on Dave 2.7k with a .68 bypass cap.

If you want a better tone a low volumes and a better taper on the MV replace wire from treble pot to MV with a 220K resistor and add a 1MEG resistor from the MV input to Gnd.

Those simple mods will make a ton of difference..and for not much $ IF you know what your doing inside a lethal death box !

[stevensamps]

Will those values also work on a 1959 ?

[Holgar]

You will not need any gain mods, if the amp is too spongy and lacks clarity. Have you taken away the bright cap? Maybe try more NFB and put the NFB wire from 8 to the 16 Ohm tap or use a smaller than 100K resistor.

[Holgar]

... and keep the bright cap on the gain pot. If you miss fullnes and mids, go to a higher value like 5000pf. I have a rotary switch with 0, 1000, 5000 and 5600pf in my 2204. After trying all the written mods from the internet, the stock amp sounded best in my ears and the bright switch is the only mod left.

[Alfi27]

Interesting to see a fellow Norwegian in here

I have been on a similar quest with my 1981 JCM800 2204, started out with a 0.68uf bypass cap on the 820R V2 cathode and that was a significant improvement! Still, I feel the low end is a bit... not sure if I would say flubby, 'vintage' is the most accurate word in my head, and a bit uncontrolled. Yesterday I bypassed the 10k V1 cathode with a 4.7k and 0.68uf (3.2k ish total resistance), and it turned the amp into a total gain monster... Although it was too much, I still don't think it sounded overly compressed for the amount of gain it was putting out, which some people who did that modification have stated. People who say anything lower than 4.7k is madness, are probably right. Putting a >10k resistor and possibly a cap on a push pull would be a great way to add a switchable gain boost though, might just do that!

Regarding the fixed resonance mod, I am very very eager to try that but there's a few things I'm uncertain of that could potentially make the modification easier. Is 47k on the 8 ohm tap, equal to 100k on the 4 ohm tap? Or is it the other way around? On second thought, just sticking with 4 ohm would probably be easier so I can just go with the 220k and 0.0047uf values.

Also, has anyone tried to change the presence cap to 0.68uf? Slash's modified amps usually sport this, apparently mainly to reduce squealing but it has to alter the tone somehow as well?

EDIT: didn't see the date of the OP... Oh well