What am I doing wrong with my 2203?

[dirtyfunkg]

I've got a 1977 JMP 2203. For the most part, I love it, but here are the issues I have:

1. It just doesn't seem to be very tight on the low end. When I crank the gain (and adjust volume, which can get deafening!), I can't get to a very tight metal sound. The bottom sort of flubs out and the it still doesn't feel gainy enough.

I've tried the following cabs:
Genz Benz G-Flex with G12-K85's
VHT Fatbottom 4x12 with x pattern G12-K100's and P50E's.
Marshall JCM-800 1960A with, I believe, G12-M70's.

It seems to sound the best through the Genz Benz cab, but it still just has a little flubby bass. BTW the flub does not seem to be speaker related. It's more in the gain structure.

2. When I do try to run the amp cranked as above, rolling back the volume does not produce the clean sound I was hoping for. My base of reference for what I was expecting is somewhat influenced by my recently sold 1987X, as well as my experience with the VHT Deliverance amps.


My guess is that the amp may need a cap job and I may want to choose some different preamp tubes. The power amp tubes are NOS Tesla EL34's that I believe are originally from the 1970's. I don't think they need replacing but would be curious to see what you guys thing.

What I have been doing in the meantime which I'm pretty happy with (and would probably do for live and rehearsals) is running into the Low input on the 2203 and dialing in a really nice clean sound, then using my Joyo Ultimate Drive as my distortion box. That gets me a pretty chunky rhythm sound that certainly cuts through the mix.

Running this rig, split from my Hardwire SP-7 into either my Sig X or D-Moll (either, again, set to a nice clean and going through the FB412) and the 2203 like this sounds HUGE but so impractical .

 

[LP Freak]

It's pretty much nature of the beast. A cap job might help but a lot of guys run a Tube Screamer out front to tighten things up.

 

[dirtyfunkg]

It's pretty much nature of the beast. A cap job might help but a lot of guys run a Tube Screamer out front to tighten things up.

That's what I've been doing though (using a Tube Screamer up front). That's why I'm confused. The other Marshalls and similar style amps I've had in the past (Peavey VTM, JCM 2204, 1987XL) tightened up just fine with a boost, albeit an SD-1. My SD-1 switch needs repairs right now so is not on my board.

 

[Racerxrated]

It's pretty much nature of the beast. A cap job might help but a lot of guys run a Tube Screamer out front to tighten things up.

This. Any mid flavored boost(SD1, OD1, TS, Maxon, EQ pedal with mids bumped, tons more....) will tighten things up well. I used to use a Joyo Ultimate Drive(OCD clone) in conjunction with a Danelectro EQ pedal with mids bumped, low end up to tighten things up and add some low end to any 2203/4 that I had. Now I use an OD1X that adds tight low end and a nice 3D mid boost. Very quiet also.

 

[K-Roll]

I'm not a pro at this but most folks run the 2203 with a drive up front. Like an SD-1.
The other thing is the cab, i hated a JCM800 through a recto cab, but loved it through a marshall (either with T75s or V30s)

However, if you're aiming for a tight chugging tone, this amp may not be the right to do the job. it's somewhat open sounding rather than tight. The boost helps, but people whose right hand isn't tracking spot on feel as if the amp was not responsive and too difficult to play or get a good sound from.

good luck sir.

 

[mrhiwatt]

Back in the day a ADA mp-1 into the front of a jmp was common. Think of extreme skidrow I believe producer Michael Wagner did this a lot. JMP is looser and not true hi gain on its own.

Mwal

 

[Racerxrated]

Try some Chinese (8th or 9th gen, with chrome square getter)pre tubes if you can find them, or Amperex. I think your power tubes are a good combination with that amp. I use Siemens or Winged Cs that I've had for years.

 

[sg guy]

-besides opening up the amp and replacing caps and value's, here's some old school 2203 trick's-(what are your settings?)-

-EQ-
-clean boost with a good EQ section-
-V-30's
-KT77's or better yet KT88's-
-(this forum is full of old school 2203 user's & modder's,.. maybe they will post some solutions)-

 

[dirtyfunkg]

-besides opening up the amp and replacing caps and value's, here's some old school 2203 trick's-(what are your settings?)-

-EQ-
-clean boost with a good EQ section-
-V-30's
-KT77's or better yet KT88's-
-(this forum is full of old school 2203 user's & modder's,.. maybe they will post some solutions)-

Gain has been anywhere from 6 to 10 as I've tried. MV has been up around 4-5, occasionally beyond for short intervals just to test it out.

I've tried various different EQ settings on the amp trying to tweak it.

Interesting on the speakers. Right now I've only really got more flat or scooped type speakers in the G12-K85/100's and the VHT P50E's. The K85's are great for modern high gain amps like the Diezel and Fryettes but maybe not as good on the more vintage voiced like this Marshall.

I would be worried about the V30 being too harsh with a bright amp like this. What do you guys think? I've been considering adding a 2x12 with maybe a V30/CL80 combo.

As far as caps are concerned, I recently just bought this amp, and it's almost 40 years old. I have no idea when the caps were last replaced. I figure that's just something I need to do anyway.

 

[dirtyfunkg]

Try some Chinese (8th or 9th gen, with chrome square getter)pre tubes if you can find them, or Amperex. I think your power tubes are a good combination with that amp. I use Siemens or Winged Cs that I've had for years.

I'll check these out also. Thanks!

 

[itsme]

I know what you mean. I have an '82 2204. I struggled a bit with it when I first got it. Thought I had to max the gain, bass, and master volume. It flubbed out big time like that. What I found is that on mine, I can't run the gain higher than 6, and the bass no higher than 7. Also the master volume is best at 3 or lower. This gives a great crunchy rythm which can be rolled clean with guitar volume. For leads or higher gain I use a stock SD1. Volume maxed, tone 11:00, and gain at 10-11:00.

Amp is set:

Pres - 4
Bass - 7
Mid. - 6
Treb. - 2
Vol. - 3
Gain - 6

Using Creamback 65's. I couldn't be happier. Gigged it sat night.

*also highly recommend a Badcat Unleash. Best Attenuator I've used. Allows me to run delay without modifying the amp for effects loop. Also LOVE having the two foot-switchable volumes for lead boost

 

[mchn13]

Definitely could be something wrong with the amp. My jmp I had with a ts boost was never close to flubby on the low end, and usually could've used a hair more. Same with the 2204 I have now.
As far as cleaning up with the knob it's hard to beat the deliverance for that. One of the best heads I've ever had for cleaning up, and the ability to get modern.

 

[sg guy]

-almost forgot-(since it is just something I do automatically, especially with MARSHALL's or any MARSHALL platform)-lower your bridge pick up...

 

[Nilo]

If you are handy with a soldering iron here are some tweaks to get you some extra push and tightness without loosing to much of the character.

The first treble peaker is usually replaced with a 68k resistor. Fuck this! Replace it with a 4.7nF cap. In series with the 22nF cap on board this will give you a total of about 3.9nF for the first coupling cap and get rid of any series resistance before the gain knob. This giving you more gain and tighter bass . Add another 10k in parallell with v1Bs 10k cathode resistor or replace with 4.7k. Gives a bit more gain and also Gives the gain structure a bit less asymmetry resulting in a bit smoother feel.
Add a gridstopper on 34k-68k on v1Bs grid (output of gain knob). Prevents blocking distortion.
Add a 470k resistor front the pots wiper to the pots ground lug. This acta as a loudness control, giving you tightar bass when you increase gain.
Change the bright cap to 100pF. Makes the gain knob more useable.

These tweaks are generally the best ones in a 2203/2204 to retain character and just improve on it. Of cou se, make sure your amp is healthy before you attempt this.

Good luck.

 

[blackie13]

try high output pickups...
you will be surprised...

 

[Kapo_Polenton]

The problem with the circuit is that you can't crank the preamp gain past 7-8.. it gets flubby and fills out the sound. The higher you drive the volume, pull that preamp back. The presence has noticeably less effect so you can turn that up as well for extra grit. Besides that, TS will tighten things up and as many have suggested, this is the nature of the beast. Lower gain pickups will help the flubb if you are dead set on going to "10" but you don't need to at all. Hot pup, preamp on 7, tiny boost from TS, watch out!

Aside from that, take it out of the chassis and see if anyone has done any simple mods like snip the bright cap. (maybe someone changed the NFR value?) People do this a lot but they are useful at higher volumes! Filter caps could use a swap 40 years is old.... besides that, a diff transformer can make a diff too but I wouldn't get into that.

 

[dirtyfunkg]

FWIW my two main guitars have a Duncan JB in the bridge. That's relatively high output and has a track record with this amp circuit.

Yeah, I'm curious if anyone has done anything inside this amp as well. I'll be taking it to my tech this weekend to get a once over to check on capacitor health and see if any circuit changes have been made.

Thanks all.

 

[Chester Nimitz]

Thermionic valve amplifiers need maintenance especially old ones.

What you do is up to you but my recommendation is relace all 6 filter cans & the 2 bias filters and retube the power section and go from there.

And have a tech replace the crappy ohms plug with rotary style.

Im speaking from experience, should cost you about $300 bucks.

 

[gbsmusic]

Back in the day a ADA mp-1 into the front of a jmp was common. Think of extreme skidrow I believe producer Michael Wagner did this a lot. JMP is looser and not true hi gain on its own.

Mwal

This!! I ran mine back in the day and it was insane!!! You can pick them up pretty cheap now.

 

[cardinal]

I'm not sure any of those cabs is well suited to the amp. Before you start trying to perform surgery, try to find a Marshall-style rear loaded cab with G12Ms, G12-65s, or V30s.