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Marshall needs more bottom

6/18/1997 2:36 PM
anonymous Marshall needs more bottom
I have a Marshall Master Volume (2203 I think) and the tone is not as deep as I would like. All caps and tubes have been replaced. Is this in the design, something out of spec, or what? The bass control doesn't seem as noticable as the mid and treble. Any suggestions?
6/18/1997 3:18 PM
Dan Lang

The JCM800's are usually bright amps by design.  
I sell a plug-in mod (no soldering or drilling needed) that warms all Marshall tube amps up.  
They also give you alot more sustain.  
If you want more info either email me at or  
Visit my web page at
6/18/1997 3:21 PM
Try add, in parallel, a 0.68uF/400v capacitor on the 820 ohm cathode resistor of the third stage (it's the second ECC83/12AX7).  
I did it on my Marshall JTM 45 "Bluesbreaker" combo and really it's makes it move some serius air.  
It's a five minute work and according to me it's worth.  
Good luck.  
6/18/1997 4:42 PM
Jim Salman

Although that mod is really cool on non-master volume Marshalls (the plexi models have the 0.68u bypass cap on the gain stage feeding the cathode follower/tone driver), it doesn't work very well on master volume models. Believe me, I've tried it, and it made the tone worse. Also, that cap used in that location boosts upper-midrange and treble frequencies, not bass frequencies.  
I think part of the problem of not having enough bottom end is that there is too much high end; the frequency spectrum is out of balance in those amps, in my opinion. I would try two things to fix this: 1) Remove the 470p cap that is soldered across the 470K resistor that goes between stages 1 and 2; and 2) Replace the 0.001u bypass cap on the gain pot with a lower value, maybe 100p or 250p (although this will make no difference at all if the amp is always played with the gain control on 10).  
You might also try thickening things up by changin the cathode circuit on the first gain stage. Try replacing the 2.7K, 0.68u combination with something like 1.5K, 2.2u (i.e., use a lower-value resistor bypassed by a higher-value cap). The trick is to not add too much bass response here or else the distortion character will get muddy.
6/19/1997 8:34 PM
Mark Cameron
I have a good trick for this. Unsolder the feedback wire (should be purple) from the 4-ohm tap(may be on the 8-ohm)and put a .0047 cap where the wire was and solder the purple wire to the other end of cap.  
This is what the deaph control on a V.H.T is, Peavey 5150 resonence control is also a version of this trick  
I think if you try to ad more bass or lesen the treble in the pre amp will make it muddy and lose the Marshall tone  
This works like the presence but this in the bass
6/20/1997 8:43 AM
You are the MAN! Tried your mod and it worked beautifully. Is there a way I could hook this up to a pot and make the mod more flexible?
6/20/1997 7:38 PM
Mark Cameron
Use a 1-MEG pot, looking from the back of the pot left to right conect tab 2&3 together then put your cap to tab 1 and the other end to 2&3 then put the purple wire to 2&3, connect a wire to tab 1 the other end of the wire should go to the 8 ohm tap that should do it.I wish I could draw it for you its easier then it sounds. Hope this helps.
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