Mk III ??low volume, or am I being unfair..

[McBarry]

Results.. finally..
signal input identical to both amps, all dials 5 except m/vol, clean channel only tested.
IIB m/vol: 1
III m/vol: 2(to achieve same vol judged by ear)
same input, signal from "send" jacks to separate mixer (so not affected by m/vol), IIB mixer slider: 6
III slider: 10 to achieve same level
Signal input into return jack, IIB: 1.2
III: 2 to achieve same volume
Changed power tubes Mesa 6L6 str 420 coke bottles (with sticker, I didn't look hard enough before) to Mesa 6L6 str 440 straigh bottle = no change
Changed V2, JJ ecc83 to vintage Mesa 7025 white inked/paint label: no change.

So nothing is really conclusive or proven. I'm still wondering if it's linear vs log pots, but really need signal tracing in each amp to get more data.
One thing I DID notice was the pots in mkIII have a lot of "slack" ie: lots of play on the shaft before the wiper actually turns.
Stay tuned, Dave

 

[SonicProvocateur]

Here are some of my thoughts, just qualitative based on what I will now call "The McBarry Test" 8)

1) The Mark I's were known to be loud. Hella loud, so loud in fact they browned out the sound on the reissue with a switch. If the IIB's were in suit, the massive transformers, and less circuitry in the way of the output signal could play into effect of the reason for less input control required for more signal for the Mark III's master to be run higher, even with R2 defeated and your power tubes qualitatively shown to be good. This only applies to when hooked to a speaker. The Mark III line was known to be tailored to what customers wanted, which may have been a bit lower volumes.

2) I'm not sure about the EQ slider scenario from the send. With the signals levels, i'd assume they perform at the same boost/cut functions, only that the Mark III has the R2 circuitry in its signal path where the IIB does not. I don't know why the Mark III had to be boosted higher.

3) On a side note, to me, the Mark V has suffered the same "wimpiness" if I can say from the EQ that lets it not perform at low to medium volumes without being cranked. Your test may be the very same thing I hear when I have tested various Mark V's. I'm certainly not badmouthing the Mark V, it's awesome, but every time I play one, I have to crank the hell out of it to get it to sound right. Far beyond where I play my Mark III.

These are just my thoughts, again.

 

[McBarry]

Ha,, McBarry Test.. love it...!!
The sliders were the MIXER sliders. I was meaning that on the mixer I had to run the channel sliders for each amp pretty much similar to the m/vol of each amp. I was hoping the signals would have been roughly equal, which would then have eliminated all the circuit up to that point, but alas no.
It's got me interested now and I'm on a mission,so I'm gonna chase a signal through each and see what shows.
SP, did U mean for the MkV U have to run it louder for a good sound, or just run the dials at higher numbers..

On a positive note, while the amps were both in theatre on the operating table, I ran the operation a little longer and transplanted some preamp tubes.
The mkIII now runs: V1 Tungsram,V2 Valvo, V3-5 Tungsram. V5,V8: Mesa 6L6 STR 430 straight bottle, V6,V7: Mesa 6L6 STR 420 coke bottle.
Both patients made a full recovery and MkIII sound quite different, in a VERY positive way.
All those hours of reading U guys posts and results/reviews really paid dividends. Kudos all...
Next is the C30/other minor cap mods to excise some lead channel fizz. While in surgery I might do a PSU/bias capectomy - haven't made my mind up.
Dave

 

[CoG]

Another observation... I have been playing my III's as my main amps for several years now (both of them have been tuned-up at MB) and there is sort of a volume ceiling that you could conceivably hit. With my usual settings on my green (Vol around 7 and Lead Master around 7) with the Master at 4.25, into an 8ohn Recto 4x12, that is as loud as the amp's getting. It's LOUD, you would not want to be within 15' in front of it, but it's not "oh sweet jesus loud" like, say, my Ampeg V4 was, or a 100W JCM800. (I cannot imagine, in 2011, ever needing to turn an Ampeg V4 up to what it's capable of doing lol.) My volume "sweet spot" is also definitely lower than this-- the amp sounds best, with these settings, just shy of 3 on the MV.

The loudest (verified by recording) I have gotten the amp to go is on R2 with the volume around 4.5, R2 volume pretty high, and the master around 7. It was Marshall-y, lol. Turning either volume, R2 volume, or master up past that point obviously just resulted in rapid, fairly unpleasant compression and power tube fuzz.

I think this is where the Mark III might be running up against the "fixed bias" thing. It's designed to run the 6L6s clean, even if under simul-class the El34s are running pretty hot.

 

[kdorsey]

Another observation... I have been playing my III's as my main amps for several years now (both of them have been tuned-up at MB) and there is sort of a volume ceiling that you could conceivably hit. With my usual settings on my green (Vol around 7 and Lead Master around 7) with the Master at 4.25, into an 8ohn Recto 4x12, that is as loud as the amp's getting. It's LOUD, you would not want to be within 15' in front of it, but it's not "oh sweet jesus loud" like, say, my Ampeg V4 was, or a 100W JCM800. (I cannot imagine, in 2011, ever needing to turn an Ampeg V4 up to what it's capable of doing lol.) My volume "sweet spot" is also definitely lower than this-- the amp sounds best, with these settings, just shy of 3 on the MV.

The loudest (verified by recording) I have gotten the amp to go is on R2 with the volume around 4.5, R2 volume pretty high, and the master around 7. It was Marshall-y, lol. Turning either volume, R2 volume, or master up past that point obviously just resulted in rapid, fairly unpleasant compression and power tube fuzz.

I think this is where the Mark III might be running up against the "fixed bias" thing. It's designed to run the 6L6s clean, even if under simul-class the El34s are running pretty hot.

I concur with the volume ceiling comment. During one outdoor gig where I was self amplifying (not mic'ed thru PA), exceeding master volume 4 resulted in excessive power stage distortion. That was with two 2x12 cabs and I was LOUD. It mixed perfectly at 50' from the stage, but I was at the output limit of the amp for the volume settings. As a note, that was running in Simul-Class w/ EL-34s, too.

And yes, I agree with the "Marshall-y" tone. I think my R2 (without the R2 mod) sounds very Plexi-ish right now.