Quote from: rnolan on November 08, 2024, 03:30:35 PMHey Dante, why do you want them together? Looks?

Yes, purely for looks. I don't want the orange thingy between the other two. Honestly, it's in a basement now, so it's never going to overheat. That rig is in retirement, I'm using my H&K and my MP-1 Classic

Hey Dante, why do you want them together? Looks?

But with Boss Fx on the bottom?, well MP2 on top is the main thing so it get more air on top of it, but Boss Fx in the middle is best for heat dissipation.  Also B200s on the bottom is better for weight distribution.

But hey it obviously will work fine how you have it now.

All good advice

Harley: I'll get in there with a chopstick,  and look for any discoloration on the resistors 

Richard: but I want the ADA gear together....maybe I'll put the Boss FX on bottom

According to the simulation, it's as flat as a pancake, assuming the digital potentiometer has even resistances at dead centre. That might not be the case but I don't care about that.

I have a hunch that the EQ is not quite zero balanced in the MP-1. The circuit looks suspicious and my ears seem to be telling me something. Like when I tweaked the filter in the Treble circuit, I would swear the sound changed even though it was programmed to 0, as if there were a slight boost at zero.

The two op-amp circuits used for mixing don't have the same gain.

I'm going to build a simulation of the cut/boost mixer to check this hypothesis.

Oh man; I was looking at some Marshall tone stack frequency responses on a website. And I noticed that a bunch of the mid scoop profiles are exactly like what I dialed in for the Mid control: -3dB half-power points at about 320 Hz and 1.6 kHz.

I have Marshall-conditioned ears!

It had to be that way. Too far below 1.6, and the tone is too nasaly/telephoney. Too far above, the tone just disappears. Same with the opposite end: cut too far below 300 and you lose body. Cut too far above, and it's too tubby.

I played with it this way and that, and in the end, what sounds  good, like what I want to hear when I'm changing the FM dial in the car around rock stations, turns out to be the Marshall scoop.

It's kind a sad in a way. 

Hey Dante, ( BTW: That amp gets LOUD ) . Nothing quite like 124w p/c into 4 ohms, probably 100 (ish) into  8 ohms, so 200w .

One suggestion though, I'd move the MP2 to the top of the rack, mostly because of heat.  MP2s get really hot on top, B200s also get hot on top (that's where the output transistors are mounted), so the B200s heat will go straight into the MP2.  I suspect the boss thingy isn't as deep ??, so putting it in between will let the heat circulate better and the extra space in the top of the rack will let the MP2 breathe.

Leon Todd gives the 3TM a good trial and also compares it to the MP-1 which he also uses.  Really suits some music, styles etc.  Personally I always found the MP-1 had plenty of gain (for me), now I use the MP-2 which has heaps more (if I wanted it).  These day's I'm dialling the gain down compared to my old levels.

Hey Kaz, it's been an interesting journey .

( I just have to document all this stuff. Sound clips would be nice. ) +1 good idea

So I think I'm done with the EQ tweaks. For the past bunch of days I had just been playing, and made one more change.

It became obvious I had made the Treble control way too narrow: Q factor of around 3.45! Cut offs at around 2.7 and 3.6 kHz, centered on 3.1.

And at the same time, too wide ranging; big change from 0 to +2 and to +4.

I fixed both issues with a resistor change which knocked down the narrow peak. The peak being a bunch of dB's down makes the EQ steps finer, and the Q dropped to 2.0, widening the bandwidth a bit wider than 2.5 - 4.0 kHz.

You might not think it's a big change, but the ear is very sensitive. It feels dialed in just right to me.

You can see the experimental process in the image. I made five copies of that circuit alone with different part values.

I implemented three or four of these. The cyan curve is the second-to-last which I tweaked to the red curve.

I experimented multiple times like this with the Mid control and Presence as well. Only the Bass took just two tries.

Kind of time consuming! Plus with multiple trips to the resistor and capacitor grocery halfway across town.

The search for tone takes you to strange places you'd never think you'd go ...

I just have to document all this stuff. Sound clips would be nice.