The Amp Garage

Just wanted to update this thread. I ended up doing the Bainzy mod on this amp (adding 3rd preamp) and I absolutely love what it did, plus the bonus is that I can switch it off and have a stock plexi as well. Actually 2 bonuses. I had a cap on the bright volume push/pull and I never cared for how it...

I suppose you could do it. It would work as it does in the Chupa if you set your "Normal" gain to minimum . The "Pussy Trim" in the Chupacabra is a 1M pot to ground in place of the 470k Mixing resistor. What about those 68k resistors in the Plexi? Also connect to pin 7? 68k resistors are on the inp...

Roe wrote: ↑Tue Oct 27, 2020 9:44 am not a great idea. just adjust the unused volume of the jmp50 instead, since it affects the voltage divider used on both channels

I'm sorry, but could you provide a little more detail. I don't understand what you mean but I'm curious.

bmx wrote: ↑Mon Oct 26, 2020 11:37 pm I suppose you could do it. It would work as it does in the Chupa if you set your "Normal" gain to minimum . The "Pussy Trim" in the Chupacabra is a 1M pot to ground in place of the 470k Mixing resistor.

What about those 68k resistors in the Plexi? Also connect to pin 7?

This looks interesting. Supposedly fine tunes the gain and saturation, but I'm not sure if this would work on a stock 50W plexi build. In looking at these 2 layouts the only part I'm questioning is V1 pin 7. On the plexi it goes to the 68K resistors to the inputs, but on the Chupacrabra this goes to...

Ok, so far I changed the V1b bypass cap back to .022 from .0022 and the phase inverter coupling caps to .022 from .1 Too late to crank it up but this is what I noticed so far. Before I wouldn't have called the amp congested by all means, but these changes have made the amp sound more airy and almost...

Here are some photos of the board. I don't quite remember what the value of the smaller (in size) split cathode cap was. All I remember is that I used the similar values that Frank Levi used on one of his amp mods. I also forgot the value of the cap in parallel to the NFB resistor. I tried a bunch u...

Consider what this looks like. And I assure you that I am not intending to be mean spirited. This is just, in my view, the cold truth. Given the volunteer nature of the group, your response that you've already posted information isn't adequate. Do you expect these generous volunteers to print a sch...

Detail matters, especially so with such a nebulous query. It’s hardly that big of an ask for you to sketch out the schematic, note the values, and take / upload a photo of it, surely? A Marshall 50 is not a specific thing, there are variants. What you’ve got in front of you may be obvious to you, b...

What current drawvdo you have your outout tubes idling at? You want the tubes idling at 60% and I assume your running 425 to 450 volts on the plates? If so here's the millamps they should idle at to attain that 60%. 425V = .035 435V = .034 450V = .033 You can go as high as 70% if your running the J...

Well if that's the case then I would replace your 50 watt OT with like a Hammond 30 watt OT which when driven hard in itself will roll off low end , add some crunch and make you open up that bass pot more and drive either a PI, the outout tubes or both harder and give you more of what your missing....

Without a current schematic, it seems kinda pointless responding? Need to know where you are, and what you've already tried and rejected. Also, are you sure the issue isn’t the speaker cab, have you tried the amp with any others at all, preferably a variety? It's not an issue. I'm trying to voice t...

I don't follow you either, as what discribe is the opposite of what should take place and what does take place during the 50 years I have seen in playing and working on amps! That being said the first thing I would do is to increase the resistance of the feedback resistor to lower the global feedba...

First, I would try reducing the two 0.1uF coupling caps in the output of the phase inverter to something smaller like .022uF if they aren't already The difference is a reduction in frequencies below 10hz which are entirely unneeded in a guitar amp as far as I am concerned. If you like the bass comp...

I'm not following you. I'm not looking to increase the bass. I'm looking for the bass to response to be more in line with the higher frequencies in regards to compression and gain when I turn it up. My amp is already on the verge of having too much bass and if anything I'd like to reduce it, but tha...