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Speaker simulator

7/15/2000 10:54 AM
Speaker simulator
Does anyone know what op amps should be used in the Marshall speaker simulator ?  
I think that any common op amp like the TL72 (or 74) should work fine...  
What about other ones, like Mesa ?
7/15/2000 4:24 PM
Ed Rembold

Any fet-input opamp works fine.  
many builders have encountered distortion,  
because of too much gain. I recommend a 50K  
pot in place of the 47k resistor in the feedback loop of the first IC. (or a 25k resistor + a 25K pot).  
Ed R.
7/16/2000 10:23 AM

Thanx Ed.  
I've also seen the JMP1 amp simulator, which looks very similar to yours.  
What do you think about it ?  
Which should be the most suitable to use with a real amp to simulate the speaker (not the whole amp) ?
7/16/2000 7:45 PM
Ed Rembold

I own a JMP1, and in its time, the speaker sim.  
was tops in my book.  
However, Marshall radically simplfied its speaker  
sim. circut, and all Marshall amps with an XLR  
output, use the "simplfied" circut. it's a little  
bit less bright, than the JMP1 circut. a lot of bang  
for your buck.  
Ed R.
7/17/2000 9:32 AM

Thanx Ed,  
I think I'll build the simplified one, because I'll use it with heavy distortion sounds (metal), I prefer a "darker" or "brown" tone, without too much harsh trebles.  
I also think that maybe it will be the best, because I actually want to use it with my AX84 "November" homebrew amp, that is a sort of mini-plexi with about 15w.
7/17/2000 1:44 PM

How does that amp sound? Is it good for blues stuff?  
7/17/2000 6:39 PM
November Amp
I think it sounds awesome.  
The preamp is the same of the 1959SLP and 1987X (plexi), I also added another switchable gain stage to make it work like a JCM800.  
The output stage is a push-pull with 2 EL84.  
The circuit design is the same of the old (and new) marshalls, but uses the low power EL84 (Vox AC30, early gibson amps, 20-40w marshalls).  
It sounds very similar to an old marshall,great for rock, but you can get also great blues tone by overdriving only the output stage (or even not).  
The sounds is very touch sensitive, and ranges from a crystal clean (if you turn the vol down) to a light overdrive, and can be turned to mid-gain overdrive.  
You can get much more infos on other great homebrews project on the AX84 site:
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