More lows from Marshall JMP 2204?

Searay

Member
I have a '78 Marshall JMP 2204 that was my first Marshall. I have thinned down to just one 2204 and one 1959 Super Lead as keepers. This 2204 has the chicklet caps in it and is totally stock including the bright cap. I'm pleased with the tone but wish I had more low end. I'm sure this info exists, but what component, location and value should I be looking at to increase the low end to get a better balance out of the Marshall. My '81 2204's had better low end.
 

Speeddemon

Well-known member
No need to get too technical. Get an EQ pedal.
Pretty sure a '78 doesn't feature an FX-Loop.
If you add an EQ pedal with boosted lows before the preamp, you may end up with a bloated, muddy signal, depending on how much you boost the lows.

If you do have an fx-loop, then yes, go for it, as you can sculpt the overall tone quite well.
 

glpg80

Well-known member
Depth mod

1M // 0.0068uF with a 0.1uF dc blocker. I’d keep the stock NFB resistor and put it on either the 4 ohm or 8 ohm tap. I prefer the 4 ohm as it isn’t as choking, but for more punch you can try the 8 ohm. Just know you’ll trade high end detail.
 

BSRIAudio

Active member
How are you setting the tone stack? Marshall tone stacks are kinda weird but you should be able to get like a 5db boost in the 80-100Hz region with everything else basically flat if you run the bass and mids on 10 and treble on 0. Think in terms of subtracting things that make the amp not bassy rather than adding more bass.
 

glpg80

Well-known member
How are you setting the tone stack? Marshall tone stacks are kinda weird but you should be able to get like a 5db boost in the 80-100Hz region with everything else basically flat if you run the bass and mids on 10 and treble on 0. Think in terms of subtracting things that make the amp not bassy rather than adding more bass.
I find the bass knob to be more of a 4x12 tightness knob, the mid knob to add low mids/bass, and the treble knob acts more like a second gain knob (as well as highs, of course)

Marshall tonestacks are funky.
 

Racerxrated

Well-known member
I would still consider an eq in front and just a slight nudge up in the low frequencies; going extreme can mud things up as mentioned. I wouldn’t put a tone sucking loop on any vintage Marshall. They all suck some tone; I’ve tried them all.
Another pedal option is the OD1X as it keeps your lows intact and can add some in if dialed sparingly. Great boost pedal; very transparent and quiet.
I seem to never want for more lows in any vintage Marshall…as stated the eq can factor in how much low end you get even with it dimed…max your presence, bass, mids 2-5 and then slowly raise the treble.

A depth mod would work wonders too, as stated.
 

ZEN Amps

Well-known member
Maybe I'm in a minority but depth mods to old Marshall just don't do it for me. What cab you running?

Or better yet, blend it with a Diezel - problem solved.
 

Searay

Member
The cab is a 1976 checkerboard 1960B with original blackbacks. I thought perhaps I could do something with a component value, but would appreciate guidance for ref/des and value, nothing more radical. thanks!
 

Fusionbear

Active member
Three Suggestions that can be done individually or together depending on your taste:

1. Swap out the blackbacks for standard small dustcap Scumback J75's. These speakers will add low thump without becoming too bright. If you are concerned about brightness, the J75LD is the large dust cap version that will tame the highs and add a bit of low mids.
2. Swap out the bass cap in the tonestack from .022 to .22. This is what Splawn does. I prefer adding the bass here, because it doesn't mess with the feedback circuit like a depth mod does.
3. Add a fat cap to the cathode of V2a across the 820 resistor. I have a 22uf on a switch in my personal build at this location.

Thanks!
 

Steve Rebel Son

New member
My Marshall Vintage Modern has plenty of low end with vintage tonality on the "Blue" low setting button. I swapped out the KT-66 power tubes with 7581A power tubes for greater head room (and smoother tone) because I run pedals through the front end. I never use rear effect loops in my Marshalls because the tone is too squelched. Instead, I plug straight into the front amp input and back way off on my pedal settings to match more natural tones instead of oversaturated tones.
 

Searay

Member
2. Swap out the bass cap in the tonestack from .022 to .22. This is what Splawn does. I prefer adding the bass here, because it doesn't mess with the feedback circuit like a depth mod does.
Thanks Fusionbear. This is what I was looking for. I'll give this a shot.
 

RedPlated

Well-known member
Depth mod is a good choice. There are multiple values that can be used to keep it more “Marshall.” The typical 220k/.0047 doesn’t give the correct mid structure for that. Try a .0022 or even .0033 uF cap instead.

22-25uF cap on V2a cathode is also also an easy way to make the amp more full sounding.
 

harddriver

Well-known member
I agree with the other suggestions that the addition of the a depth mod would be the easiest and gives you an adjustable control of how much low end you want depending on the situation. When playing live at higher volumes you would need or want less low end and you dial it out. Playing at home at lower volumes most people want more low end present to make up for that fact they aren't moving as much AIR.

Most Depth mods are a 1 MEG audio taper pots with a bypass cap of you choice of the frequencies you want to enhance.
.0047uf gives the most low frequency bass
.0033uf less heavy low frequency bass
.0022uf even less heavy low frequency bass

You could put all three on a three way switch to give you some variety depending on your taste at that time.
 

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fek

Well-known member
Another option is to use a Power Station. Has depth control options already on it or use the loop in the PS to add an EQ pedal. No amp mods that way.
 

BesaMoogie

Active member
My best bet would be either on tubes or a different cab, no fan of modding vintage amps.
With tubes you can go with JJ in the preamp and either E34L or 6ca7 in the poweramp. All of them will give you more bass.
If you want a cab with a lot of bass, try the Mesa 4x12 OS.
 

psychodave

Well-known member
We need more information.

What power tubes are you running? 6550’s will bring in some nice bottom end. For my ears, quite a bit more bottom end. It’s a Marshall, so you’ll still have tons of “Marshall mids”.

Also, are you boosting it? If so, the boost might be stealing low end.

You say your cabinet has “Blackbacks”. Are they 25 or 30 watt speakers?
 

stephen sawall

Well-known member
One of the guitarist I worked with for many years immediately put 6550 in all his Marshall amps for this reason.

Power Station is a nice option and gives a lot of control.

I understand these like all the recommendations might alter what you do like about the sound too much. I mean Marshall voiced these amp and could have made them more bass heavy. It is the nature of them.
 
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