Marshall Class 5 Mods

wagdog

Ack
A little behind in posting this.

I've got a Marshall Class 5 I picked up on craigslist a while ago. It was OK sounding, not great. I modded it, it got better, a lot better. This past week, I went a little crazy with it. It's not done yet, but here's where it's at:

I reconfigured the cathode follower to be another gain stage prior to the tone stack.

I added a volume control after the tone stack.

I made the cathode bypass on the new gain stage configurable with a 3-way switch - it has a .47uf, 2.2uf and 4.7uf switchable cap - this is pretty cool 'cause you can tone down the bass response for humbucker guitars.

The first gain stage has a switchable cathode bypass as well, but only two settings: .47uf and 4.7uf + the .47uf.

The second gain stage cathode also has a switch to lower the cathode resistor value and get more gain. MOAR GAIN IS GOOD, <evil laugh>.

I liked the sound of it through my MESA 1x12 cab with a black shadow, so I ordered a back shadow and sliced and diced up the cab. I'm going to need to front mount the speaker so it will fit. It *should* fit... I hope. If it doesn't, I'll have to cut a spacer ring to move out more in front.

I'm still waiting for the new speaker, should be here Wednesday. The speaker in the pics is an old, tired, fender speaker - doesn't sound good in this amp. The mods sound great. It's LOUD.

Pre-slice and dice:
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Extra vol control installed after tone stack.

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12" speaker is going to be a tight fit. The tubes are very close to the speaker.

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Old nasty grill.
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I used the old baffle to make a frame for the new grill cloth.

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New baffle cut from plywood. The new grill frame is below it.
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Speaker fits. (that's an old cruddy fender speaker)
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Cathode bypass cap switch(es) and gain switch.
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New switches on the front.
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New grill cloth mounted on frame. I used the old piping. I ordered new piping, but didn't need it... maybe I'll build a matching external 1x12 cab?
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Waiting on the speaker to finish it off.
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Speaker arrived. It was in perfect condition. It looked like the previous owner had a cat though.

Things happened fast...

The speaker almost hitting the chassis and the magnet is pulling it in. I stuck a pack of post-it notes there temporarily. I ended using a wood shim with some double side tape to make sure it wasn't contacting the chassis.
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I taped the emblem in place to get it centered, then used fishing line to hold it in place. I didn't want to mess up the new grill cloth by making holes and putting on a backing plate.
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Everything was good right up until the piping was installed. It pushed the sides of the grill cloth frame in a hair and the grill cloth is not as tight as it was before. It's OK, but I noticed it.
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I opened the back of the cab up a bit.
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It looks great and sounds killer. The circuit mods I put in really opened the amp up. I'll try to make some clips in the next few days.
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Couldn't leave well enough alone.

A number of Marshalls have a 4 diode "fuzz circuit" permanently wired in the gain channel. Some folks don't like them as they are "solid state". They can sound fizzy. I had a JCM 800 combo years ago that had them and I liked it. Tube screamers have they exact same circuitry. Anyway, I have about 400 of these diodes so I temporarily spliced 'em to see if it was useful. It was. So, I added one more switch on top of the amp to use this circuit, or not.

I'm feeling like @Elias Graves only with solder instead of sandpaper.
 
Class 5 was a tonally rich 5 Watt all-valve amp that featured true class A circuitry. The C5-01 combo produced pure Marshall tone with great feel and response. Conceived in the wake of numerous requests from both professional stadium fillers and bedroom widdlers alike, this compact combo was the answer to many low wattage, big tone prayers.

Created in the legendary Bluesbreaker style, the C5-01 took things back to basics with a top-loaded, Plexi-esque control panel comprising of volume, bass, middle and treble. Responding naturally to playing dynamics, and producing rich, second order harmonic distortion. This purist pleasing combo went from brilliant clean to full-bodied crunch and on to glorious lead tones.

All this great tone was delivered through a specially designed Celestion G10F-15 speaker
This doesn't seem spammy at all, does it, @Mark Wein?
 
who cares? They are commenting in a thread started about the amp. They aren't rude and didn't start a thread to push their wares. And they gave us "bedroom widdler."
 
who cares? They are commenting in a thread started about the amp. They aren't rude and didn't start a thread to push their wares. And they gave us "bedroom widdler."

Today it's on topic gibberish. Tomorrow it's boner pills gibberish. Can't let it get comfortable.
 
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