Can you really tell a difference...

[streakin406]

In the simul/non-simul amps by sound only? What are the characteristics of each?

 

[MrMarkIII]

The Simul amps add another, parallel, power section that runs in Class A (wink, wink) and only puts out 15 watts before clip (25 watts in the green stripe).
Generally, the Simul amps get power tube distortion at lower sound pressure levels that non-Simuls.
Non-Simul amps are "glassier" (all 6L6s), and according to the Mesa catalogs of the time, more "clinically accurate sounding". Simul amps are more forgiving and "spongier".
YMMV.

 

[>Photi G<]

Yes, that is the textbook answer, but the OP was asking someone who has extensive experience with both to provide a comparison, if any.

 

[screamingdaisy]

The problem I have is that I've never had the chance to directly A/B two same model Marks... one with and one without Simul-Class. It doesn't help that Simul-Class has evolved over the years, including a change from Triode to Pentode and an increase in power from around 60w to 75w to 90w. It also doesn't help that there's a difference between a Simul-Class amp that can only run one tube type vs a Simul-Class amp that can run a 6L6 pair mixed with an EL34 pair.

The textbook answer is that a non-Simul, 100w Mark has more headroom and can push out more bottom end.

The Simul-Class amp has less headroom, more compression, more midrange and a bit more sponge on the bottom end (due to the Class A pair). It's a bit like you're running 25w and 50w amplifier side by side, then summing the total signal and feeding it into the same speakers.

 

[dodger916]

Per Mike B, non-Simuls are the classic "Fender-on-steroids", whereas Simuls blurr the articulation a bit, lending touch sensitivity and harmonics to the sound.

 

[MrMarkIII]

Yes, that is the textbook answer, but the OP was asking someone who has extensive experience with both to provide a comparison, if any.

Oh, excuse me. Should have been clearer.
Yes, the above post is my personal, direct experience.
I own and have played for over twenty years, blue and green stripe Simuls, and a 60/100 (non-Simul, of course).
Screamingdaisy and dodger916 are also correct.
Thank you.

 

[tony777]

In the simul/non-simul amps by sound only? What are the characteristics of each?

The difference of my non simul (60W) c+ and my simul (75W) c+ is very noticable, most at the rhythm channel, but absolutely present in lead as well. The simul has delicious highs, where the non simul has agressive highs. Slightly tighter bottom at the simul as well. The 60W is leaning into raw sounding, when the simul is smoother.
Both sound fantastic though, but just different.

I use the STR 415 in both amps. and STR 447 at class A at the simul, with mesa russian 2 12ax7.
Tubes make a difference, so I am A/B'ing with similiar tubes.

I have not played a 100W mark amp, so I can't comment on that one.

 

[>Photi G<]

If you take a look at the schematics, Simul Class isn't really Simul Class at all. It's a 60W pair of 6L6's running cold at full tilt, with a 15W pair of EL34's running very warm, creating a smooth effect. The only way to have a true Simul Class system was if the EL34's were Cathode Biased, and had a lower plate voltage, but that is impossible without adding a second Output Transformer to the mix.

The new 90W simul class amps, like the Mark V and the Electra Dyne, do some even crazier stuff-the Class A pair has been set up to put out 30 watts now, and when switched down, the 60 watt pair stays on, while the Class A pair turns off, and the output is lowered to 45 watts, somehow. But, The Mark V is able to run two TRUE class A tubes in a Single Ended setup at it's lowest 10W setting, which hasn't been done before.

 

[streakin406]

On an early mark III with out a sticker anymore, what would the code on the output transformer to distinguish a simul amp?? I have tried searching but cannot come up with what I am looking for. Thanks guys, best forum on the web

 

[CoG]

I've played a 100/60 Mark III blue and owned a green and a purple simul. The 100 has a bigger sound with more space in it and more "going on" in the highs and lows while the simuls are a tiny bit more punchy and smooth. The simuls have super-tight lows but the 100 has kind of a "whomp" to it that the simul doesn't.

The cleans on the 100 were definitely a bit fuller and nicer. Simul cleans, if you want *clean*, are a little on the plinky side and it's hard to play totally clean at any real volume. The simul has a really nice bit-o-dirt sound though.

All of these differences are only noticeable at volume, though, and I don't think I could pick out a 100W versus a simul in a mix unless the sound was totally clean.