Greetings! This is my first post here, and I have a lot of questions about the possibility of modding my Marshall Mosfet 100 Reverb 5215. I tried searching for threads that touch on the relevant topics, but I didn't see much that answered my questions. I apologize if these topics have been discussed and I missed the info.
Basically, I'm thinking of modding my 5215 to add current feedback, in the hope that it will add some depth and presence to the tone. In its stock form, it sounds a bit dry, and dull on top. Here is the schematic of the power amp. I have experience with vacuum tube electronics, but less with solid state, outside of preamps and pedals.
Going into this, my main concern is that replacing some of the voltage feedback with current feedback will give the amp more gain at the extremes of the speaker's impedance curve, and that this might cause clipping with higher signals. I don't have enough experience with SS power amps to know if clipping is safe within the safe operating area of the MOSFETs. Is this a valid concern?
While researching that, I did some math on the stock power amp. It appears that it only takes 591mV peak signal to drive the power amp to full 100WRMS output into a 4 ohm load. The preamp should be able to put out almost 3x as much peak signal. Is this common? On top of that, it appears the current protection doesn't start to work until the amp is putting out 7.6A of current, which is way past the rated power of the amp into a 4 ohm load. Is this normal? Is the protection only for shorts?
It looks to me, in my limited knowledge, like the amp is already built to melt itself down if the user is just a bit too exuberant. Would using current feedback only make it more likely to be pushed beyond its limits? Can I beef up the protection circuitry to make it safer?
Thanks for reading, and thanks ahead of time for any insights.
Basically, I'm thinking of modding my 5215 to add current feedback, in the hope that it will add some depth and presence to the tone. In its stock form, it sounds a bit dry, and dull on top. Here is the schematic of the power amp. I have experience with vacuum tube electronics, but less with solid state, outside of preamps and pedals.
Going into this, my main concern is that replacing some of the voltage feedback with current feedback will give the amp more gain at the extremes of the speaker's impedance curve, and that this might cause clipping with higher signals. I don't have enough experience with SS power amps to know if clipping is safe within the safe operating area of the MOSFETs. Is this a valid concern?
While researching that, I did some math on the stock power amp. It appears that it only takes 591mV peak signal to drive the power amp to full 100WRMS output into a 4 ohm load. The preamp should be able to put out almost 3x as much peak signal. Is this common? On top of that, it appears the current protection doesn't start to work until the amp is putting out 7.6A of current, which is way past the rated power of the amp into a 4 ohm load. Is this normal? Is the protection only for shorts?
It looks to me, in my limited knowledge, like the amp is already built to melt itself down if the user is just a bit too exuberant. Would using current feedback only make it more likely to be pushed beyond its limits? Can I beef up the protection circuitry to make it safer?
Thanks for reading, and thanks ahead of time for any insights.