Lyle Caldwell
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- Joined
- Dec 31, 2010
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A client brought me his new Class 5.
In stock form I found the amp almost unusable. Weird mids and lows for Strats, sounded pretty good at higher gain with humbuckers, but splatty with single coils, and the low gain sounds were pretty bad. No real treble, just mids and boomy lows - the Bass knob was useless with such a narrow range.
But I tweaked it all out and I think the result is a damn good sounding amp with about $5-10 worth of different parts.
Here's what I changed - feel free to try this if you like.
Input - change the input impedance to 1M. This helped the Strat single coils out immensely.
I put in a switch to go from full lows to tight "Plexi lead" lows. You can play around with the cathode caps if you don't want a switch. The 1uf is the "Plexi" value for tighter lows.
I put a very subtle bright cap across the volume and removed the voltage divider after the volume control.
Changed the slope resistor to get a more balanced sound (not as trebly/middy) and changed the bass cap to a 22n to get a more usable range out of the Bass knob.
Changed the cap coming off the plate of V2 pin 1 to have more lows so the earlier switch would be apparent.
Put in the "Marshall emphasis cap" across R12 (this is to taste).
Bumped up the values of the voltage divider after the cap on the plate of V2 pin 6, again to make the earlier bass switch apparent.
Put in a "fizz cap" here (68pf to ground) and made the grid to the EL84 a 220K - slightly warmer.
Put a wire in the speaker jack section to make the "headphone switch" become an output attenuator for both speaker jacks - allows late night practice.
We're going to be putting a Mercury Magnetics choke in, but the amp sounds really good as it is now.
Maybe some of you will dig these simple mods.
http://psionicaudio.net/images/Marshall-Class-5-Mods.jpg
In stock form I found the amp almost unusable. Weird mids and lows for Strats, sounded pretty good at higher gain with humbuckers, but splatty with single coils, and the low gain sounds were pretty bad. No real treble, just mids and boomy lows - the Bass knob was useless with such a narrow range.
But I tweaked it all out and I think the result is a damn good sounding amp with about $5-10 worth of different parts.
Here's what I changed - feel free to try this if you like.
Input - change the input impedance to 1M. This helped the Strat single coils out immensely.
I put in a switch to go from full lows to tight "Plexi lead" lows. You can play around with the cathode caps if you don't want a switch. The 1uf is the "Plexi" value for tighter lows.
I put a very subtle bright cap across the volume and removed the voltage divider after the volume control.
Changed the slope resistor to get a more balanced sound (not as trebly/middy) and changed the bass cap to a 22n to get a more usable range out of the Bass knob.
Changed the cap coming off the plate of V2 pin 1 to have more lows so the earlier switch would be apparent.
Put in the "Marshall emphasis cap" across R12 (this is to taste).
Bumped up the values of the voltage divider after the cap on the plate of V2 pin 6, again to make the earlier bass switch apparent.
Put in a "fizz cap" here (68pf to ground) and made the grid to the EL84 a 220K - slightly warmer.
Put a wire in the speaker jack section to make the "headphone switch" become an output attenuator for both speaker jacks - allows late night practice.
We're going to be putting a Mercury Magnetics choke in, but the amp sounds really good as it is now.
Maybe some of you will dig these simple mods.
http://psionicaudio.net/images/Marshall-Class-5-Mods.jpg