Does anyone have a rundown of the various mods?

ners

New member
Starting to get deeper into Plexi circuit mods, but there's slim chance I get my hands on a Cameron anytime soon (and YouTube just doesn't cut it); so just looking to learn more about his amps. Any specific threads worth reading? My search returned about 90% people bitching...

* CCV
* Aldrich
* Ocean
* High/Low Gain Jose

Not looking for an exact circuit, but would love to know the general differences (extra gain stage, diode clippers, etc) between all of his work.
 

panhead

Well-known member
Starting to get deeper into Plexi circuit mods, but there's slim chance I get my hands on a Cameron anytime soon (and YouTube just doesn't cut it); so just looking to learn more about his amps. Any specific threads worth reading? My search returned about 90% people bitching...

* CCV
* Aldrich
* Ocean
* High/Low Gain Jose

Not looking for an exact circuit, but would love to know the general differences (extra gain stage, diode clippers, etc) between all of his work.
Not enough to talk about
 

NewReligion

Active member
Starting to get deeper into Plexi circuit mods, but there's slim chance I get my hands on a Cameron anytime soon (and YouTube just doesn't cut it); so just looking to learn more about his amps. Any specific threads worth reading? My search returned about 90% people bitching...

* CCV
* Aldrich
* Ocean
* High/Low Gain Jose

Not looking for an exact circuit, but would love to know the general differences (extra gain stage, diode clippers, etc) between all of his work.
You spoke of the Aldrich but I wish to expand upon that modification.

1.) There a variants of his Aldrich mod. Some two channel, a single 3 channel I believe ended up in Hawaii the last I heard. Some with a gain trim pot & some with clippers on the master volume as well.

I owned three of Mark’s Aldrich’s. An additional variant had a 5 way rotary Switch set to parallel a coupling cap on V2. Honestly, I lifted the rotary & the amp came to life a bit more IMO. Have to look out at the swamp resistors as well. If replaced with any value higher than 5.6k the amp can take on the Mesa characteristics especially if he changed the TS Slope Resistor to a 47k & the Bias Voupling Caps to .1uf

I would not be surprised to find Mark elevated the heaters on some. This is a non cathode follower circuit which is where Mark picks up the 4th stage of gain. Unique in how he couples the first three gain stages with the inclusion of the gain pot. The “Old Bitch” should fall into the Aldrich catagory.

2.) I read that you pretty much covered the pre tone stack master volume clippers a.k.a. “Jose” mods. The core Jose mod Mark perfected had two gain knobs but I found if one of the gain pots were to be turned up to or beyond about 6 on a M1A Taper Potentiometer the preamp circuit will become undefined with low mid flub saturation. To this end we can add another clipper circuit variant named the “Atomica”.

The second gain is set just below what about 5 on a M1A pot would be with components internally. May be mounted in any number of ways.

3.) The Bogner style circuits Mark deployed. He took a couple years but finally got his room mates Bogner Modded Marshall operational. This amp had one of the Bogner blue PCB’s in it. The amp did not operate when his room mate purchased it from Bogner’s hometown in Germany.

Mark did a great job at finishing this amp out to be the “Snorkler” circuit. If you are unfamiliar, the Snorkler was owned by Ronnie Champagne & used extensively by Jerry Cantrell on Alice in Chain’s killer debut album “Facelift”. This too is a non cathode follower circuit picking up the 4th stage again where the cathode follower would be so in all of these cases I should point out the tone stacks are plate (Anode) fed. Mark may use a variation of different tone stacks in addition to a lot of .047uf coupling caps in place of .022uf.

For ideas on the circuit posted above you can reference the Hafler-Bogner Triple Giant schematic. Study the “Sharp” channel.

4.) The last non cathode follower circuit I can speak to is what Mark referred to as the Cantrell mod. I own the one off Cantrell though I suspect there are a few around which are similar in circuitry. I prefer this to the Snorkler by Mark as it cuts nicely.

Built my own version of it. Ronnie Champagne hit me up for a chat to say it sounded damn close to what the Snorkler sounded like in the room. Seemed like a very kind guy that enjoyed talking shop a bit. I have no idea who owns that particular amp at this time.

I can’t think of anything else at the moment as I should have been sleeping hours ago but I’m practicing my chops & typing this out for you at 6:22am lol

Best Regards, David Hopkins
 
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glpg80

Well-known member
I’ve recently heard that tone of the amp seemingly falling apart when the first gain pot is cranked and the second gain pot is set around 6-8. The amp gets dark and low mid focused. Usable but not Marshall. I always dimed the first gain pot and then dialed it back with my ears until the amp seemed to open back up again. I’m just going to hardwire the divider circuit at that point. There’s so much gain at 4 stages into a cathode follower that shielding practices have to be made and stages have to have shielded coax. Grounds have to be short. High gain as well as lots of features make it challenging.

I actually don’t like to bypass both gain pots. I like the stock gain bypassed for a mid boost, but I find the amp gets too shrill when bypassing both gain pots.
 
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