50w Plexi mods

Swapping out speakers in cab -OR- putting a hammer though your Line6 Spider? Tell us about it.
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Bubba
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Re: 50w Plexi mods

Post by Bubba »

Greg_L wrote: Thu May 04, 2017 9:18 pm Ok so I found a version of the cascade gain mod using a push/pull pot for the normal channel volume pot. It makes the amp work as stock and as a hairy shred monster. But I don't think I'm gonna mess with it anymore.
Hmm. The result of that mod doesn't sound like anything I would like to achieve, in any case. I think you're doing the right thing. :coolstorybro:
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rayc
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Re: 50w Plexi mods

Post by rayc »

That is wild n haory. Bummer about the downside.
Oh well, you'll find the answer somewhere.
Superb work on the MV & maintaining the front panel's integrity.
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Greg_L
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Re: 50w Plexi mods

Post by Greg_L »

Bubba wrote: Fri May 05, 2017 6:34 am Hmm. The result of that mod doesn't sound like anything I would like to achieve, in any case. I think you're doing the right thing. :coolstorybro:
It's not a sound I'd use. I just wanted to see if I could make that type of Marshall sound and how it would work, if it would work, and if I could do it and still have the amp function as stock. I won't sacrifice the amp for some dated hair metal tone. :facepalm2:
rayc wrote: Fri May 05, 2017 6:52 am That is wild n haory. Bummer about the downside.
Oh well, you'll find the answer somewhere.
Superb work on the MV & maintaining the front panel's integrity.
Thanks Ray. :like:
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Bubba
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Re: 50w Plexi mods

Post by Bubba »

Greg_L wrote: Fri May 05, 2017 8:53 am It's not a sound I'd use. I just wanted to see if I could make that type of Marshall sound and how it would work, if it would work, and if I could do it and still have the amp function as stock. I won't sacrifice the amp for some dated hair metal tone. :facepalm2:
Yes, you have to try stuff. You never know, you might have really dug it. :smiles:
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Lt. Bob
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Re: 50w Plexi mods

Post by Lt. Bob »

awesome pics man ...... now you're almost ready to open "Gregs Mods' .... "we fix your amp like WE want it"
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Greg_L
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Re: 50w Plexi mods

Post by Greg_L »

Bubba wrote: Fri May 05, 2017 9:48 am Yes, you have to try stuff. You never know, you might have really dug it. :smiles:
If I can figure out how to have the amp remain as stock, and also do the cascade gain mod on a switch, then I will do that. I wouldn't mind the hair metal tone, but not at the expense of the rest of the amp. The problem is every single layout or method I can find is for turret board amps. Everything is so simple on those things. I know my PCB version is the same circuit, but you can't just swap things around easily on a PCB amp.
Lt. Bob wrote: Fri May 05, 2017 10:19 am awesome pics man ...... now you're almost ready to open "Gregs Mods' .... "we fix your amp like WE want it"
Lol. If I knew anything at all about modding amps, maybe I would. But I know nothing. I'm just following directions and copy-catting what others have already done.
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Greg_L
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Re: 50w Plexi mods

Post by Greg_L »

Here's one I found yesterday. This seems like it would be ideal. But I'd need to sit and trace out how this diagram translates to what I have on my PCB..
1959RR1wireswitch.jpg
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ido1957
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Re: 50w Plexi mods

Post by ido1957 »

Listened to the MP3 - it has that distinct hair band sound. Usable if that is the goal but a switchable pot would be a good overall solution to retain that stock sound as you say. Interesting mod. You just cloned a JVM. :)
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Greg_L
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Re: 50w Plexi mods

Post by Greg_L »

ido1957 wrote: Fri May 05, 2017 11:28 am Listened to the MP3 - it has that distinct hair band sound. Usable if that is the goal but a switchable pot would be a good overall solution to retain that stock sound as you say. Interesting mod. You just cloned a JVM. :)
Haha yeah, sort of. The OD/Orange mode of the JVM is very much a very similar hair metal type sound. :metal:

There is something better about it through a Plexi circuit though. It's more open, not as compressed as the JVM.
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Farview
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Re: 50w Plexi mods

Post by Farview »

I had a cascading mod done on an old jmp, but mine allowed you to play with both channel volumes. If you turned the 1st down and the 2nd up, you would essentially get the stock sound.

You could also get tone variations by using more or less of one preamp or another, since one of the preamps was brighter than the other. Mine wasn't switchable.
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Greg_L
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Re: 50w Plexi mods

Post by Greg_L »

Farview wrote: Fri May 05, 2017 12:23 pm I had a cascading mod done on an old jmp, but mine allowed you to play with both channel volumes. If you turned the 1st down and the 2nd up, you would essentially get the stock sound.

You could also get tone variations by using more or less of one preamp or another, since one of the preamps was brighter than the other. Mine wasn't switchable.
Was it a turret-board amp? I'm seeing all kinds of cool shit done to those type amps. Apparently no one does anything to the PCB amps that I can find so far. If I knew how to read a schematic I'm sure I could figure something out. But I don't know how a bunch of squiggly lines on paper correlates to what I see on a circuit board. I know what to do to make it cascade only, and it worked. But I don't know to make it stock and cascaded.
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einstein magoo
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Re: 50w Plexi mods

Post by einstein magoo »

Congrats on the success! You gots some balls to fiddle around inside an already awesome amp.
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Greg_L
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Re: 50w Plexi mods

Post by Greg_L »

einstein magoo wrote: Fri May 05, 2017 1:48 pm Congrats on the success! You gots some balls to fiddle around inside an already awesome amp.
Thanks man. I have two important things going for me....
1) It's not my only amp.
2) I'm a fearless moron.
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einstein magoo
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Re: 50w Plexi mods

Post by einstein magoo »

Neat! Didn't realuize you were fearless.
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Greg_L
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Re: 50w Plexi mods

Post by Greg_L »

Okay, minor breakthrough...

I'd been one-wiring the wrong side of the input resistors! :lollers2: :facepalm:

So I ran a jumper to the other side and voila, that sounds like it should sound. :coolstorybro:

And as a confusing bit of good fortune, the bright channel still works as it should.

Now, it's not switchable. I have to physically unplug from channel one and go into channel two to get the monster gain, but it does work. :coolstorybro:

Also, a 1 meg resistor on the second volume (now gain) pot going to those input resistors seems to tame the fizz pretty damn well. Sounds massive and meaty without any harsh fizz or buzz. It's surprisingly quiet too. Go figure. :happytrees:

I'm gonna remove my jumper wires and hardwire this bitch for keeps now.
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Farview
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Re: 50w Plexi mods

Post by Farview »

Greg_L wrote: Fri May 05, 2017 1:41 pm
Was it a turret-board amp? I'm seeing all kinds of cool shit done to those type amps. Apparently no one does anything to the PCB amps that I can find so far. If I knew how to read a schematic I'm sure I could figure something out. But I don't know how a bunch of squiggly lines on paper correlates to what I see on a circuit board. I know what to do to make it cascade only, and it worked. But I don't know to make it stock and cascaded.
I wish I could remember. I sold the amp in the late 80's (like an idiot) when I got the Laney endorsement.
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liv_rong
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Re: 50w Plexi mods

Post by liv_rong »

Fuck, impressive dude, Nice looking work too!
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Greg_L
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Re: 50w Plexi mods

Post by Greg_L »

Thanks liv.

Ok, I think this might be it.

Hardwired my one-wire mod with some shielded wire to minimize noise. Grounded one shield end on the pot ground, the other end goes to the input resistors. As you can see, it is literally one wire. I kind of cheated on the board end. I tinned the ends and tucked them under the resistor legs, then soldered. This way it's unobtrusive and easily reversible with no damage anywhere. The pot end is as basic and simple as soldering wire to a pot.
Image

And that's it. It works! Massive gain, unnervingly noise-free, and it can be wound back down to stock typical Plexi cleanish crunch sounds on the bright channel. All inputs work as they should...although I did not try jumping the channels yet. As far as I can tell, it's stock bright channel, and the second channel is mega gain. Cool. I'll try it tonight at practice and see if it blows up.

All buttoned up. Chicken head master volume knob out back...
Image

This 50w is on top. Totally stock looking front, with face melting gain hiding behind the top right input.
Image

:minernuggs: :coolstorybro:
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ido1957
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Re: 50w Plexi mods

Post by ido1957 »

Excellent !
People want something for nothing, they want it right now. Either they can't tell quality or don't care but feel it is important that everyone agrees with them.
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Re: 50w Plexi mods

Post by Farview »

What happens if you turn the bright channel all the way off? Do you still get sound?

On my mod, one channel would actually feed the other. If you turned either one down all the way, you would get nothing. You could vary the amount and color of the gain by adjusting the two channels against each other.
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