Giving up on my Mk III + recap on the mods

[okgb]

Tried most of the typical things but not all
[ as my resources allowed ]

no stripe , non 105 xfmr loaded combo simul

I know it's tough in words but i'll try to describe it
could be some of what it's good at I don't like
you may say it has a in your face upfront feel
but i'd describe it as a Dry midrange that's no fun
to play , sort of like having your ear close to the speaker
instead of 10 feet away in a nice room
what i would really like is a little more texture & complexity
kinda like you had reverb on with no reverb
[ if you know what i mean ] more depth , less bold

I only have a few different preamp tubes to try
either U.S. or british ones none of the " magic "
ones mentioned and mostly celestion type speakers
around the house . may still gain something there

Some of the mods helped but not in a dramatic way

Did the power supply caps even though there was no hum problems
If anything this made it a little more punchy where i'd rather have it
looser in feel . [ i hadn't been playing the amp much so not a direct
comparison , just assumed with it's age that it'd help ]
Mike B , said he doesn't usually change the 30 uf caps on the mainboard
otherwise there were 4 220uf caps by the psu , sounds like boogie will
sell these to you . [ i ordered them all before i talked to him ]
BTW Mike B did return my call but i'm sure he's busy and seems to want
a concise , obvious question , I guess he can't spend allot of time on the calls .

the presence cap mods seemed to shift it higher ? but does give a more usable range
now . i used a polystryne cap i had around .
the c27 mod [ man i wish there were part #'s on the schematic to relate where they
are in the circuit ] not sure about this one no harm , maybe not enough like able
difference , have to play it more [ it's in the tone stack part of circuit ? ]
c30 seemed to smooth it out , still experiencing the brighter distorted part of the
signal dying out sooner leaving a cleaner smoother note sustaining a little longer ,
this is better and longer with the mods & tube change than before but still there .

Mostly i use a luke with EMG's , using Duncan pearly gates is better by
15 -20 % ? need to play it more & try more speakers although i'm reluctant
spend a bunch more money [ gotta be finacially responsable ]

Mods were not hard to do at home as long as you know how to solder
and have a good iron

 

[DaveP]

What speaker are you using in the combo? I had a Mark III blue stripe and it sounded horrible with the EVM12L but sounded great with the Celestion C90.
I was experiencing the same thing you described and the C90 fixed it.

 

[okgb]

speaker in there now is a
made for mesa ? Black shadow
with a celestion international label on it
bought in the 80's
I have to make up a cable and try it on a vintage 30
that's in a DSL combo

 

[CoG]

What you are describing really sounds like a speaker thing. With the EVM or the C90 the default Mark setup is for a fairly "hi-fi" sound, and combined with the Mark III's naturally in-your-face middy tone this makes for a very non-nuanced kind of high-gain sound.

A V30 isn't gonna help, in fact in my experience it'll sound worse.

Suggestions--

1) volume, getting the EL34s into the drive equation really makes a big difference.

2) After a lot of fiddling I have come to the conclusion that the (well, at least my green stripe through a Recto cab) Mark III actually plays and sounds smoother and more responsive with a *very small* amount of attenuation (like -3db, which is not enough to keep from getting kicked out of your apartment or even take you out of the earplug zone :lol: ) but if you don't already have an attenuator they are expensive. It seems like most attenuators compress the high end just a little bit.

3) Volume and tone knobs that actually work. Remember that the Marks interpret treble as gain. Rolling back on your tone on the guitar, even just a teeny bit, can make a big difference. Of course, like I said, you need knobs that actually work. I was amazed when I got an '82 Yamaha SG1500-- it was like, whoa, so THAT's what those things are supposed to do!

4) Try recording actual tracks in a band mix. If you plop them down in front of an amp, 8 guitarists out of 10 and like 10 out of 10 Mesa players automatically try to find a lead tone that is too dark and fat to sit in a mix.

 

[kdorsey]

Those are very good suggestions, CoG. The only thing I'd add is that a single speaker is WAY too little load for a MkIII playing hard rock/metal. I don't play metal, but certainly consider my sound "hard" with definition, so I require pushing this amp. To keep the SPL into reasonable ranges, try a 2x12 or 4x12 cab. I use a pair of 2x12 Boogie cabs but only have my master at 2-3. If only driving the single EV, it would be brutally loud and shrill, making my drummer want to punch me! The added speakers distribute the air more evenly and prevent that brittle breakup.

I would highly recommend reconsidering your preamp tube selection and speaker/speaker cab options. Between those two, you can wrangle control over a Mark's brightness pretty well. Leverage that Simul-Class power stage and get some Boogie EL-34s in there. You'll notice a warm up instantly and the glass shattering brittleness will melt away.

CoG, what kind of attenuation are you referring to? Power attenuation or speaker output attenuation (Power Soak/Brake)? If the latter, I've used a Marshall Power Brake for 15 years and love it. But my recent changes eliminated the need for it. Otherwise, I used to drive my master at 7 and drop the Power Brake considerably for a really nice, driven sound.

 

[CoG]

I have tried a whole wack of attenuators and ended up with a Marshall Powerbrake too-- most people hate them, but they really are the best thing for a JCM800 (my other main amp) and with the Mark III I am applying so little attenuation that the heavy squashing effect the Powerbrake has isn't a problem. I just want a wee bit of squash

For okgb, far as the Mark III's brightness goes you have to remember that the high-gain channel on the amp was designed for 80s lead/shred playing. So tones that would be painfully bright on their own, cutting through a really busy mix, were the order of the day. If you dial in some of the suggested settings in the manual they're ear-bleedingly bright on their own. When you're trying to tame that too much you're kind of fighting the amp design itself, and you might be better off with something based on a JMP circuit.

One other thing-- pickups. Pickups now are sooooo much hotter than when the Mark III was originally playtested. The whole idea with a Mark IIC/III was that you didn't need a pedal or a hotrod job, the gain was all there at the start. EMG's ARE a boost pedal by 1987 standards I've played other people's EMGs through my greenie and it just sounds bad.
Cooler pickups will give you a much less "strident" sound out of your Mark III.

 

[Facelift]

The cure for mellowing out the brightness.

 

[kdorsey]

The cure for mellowing out the brightness.

Are you the guy in the Ukraine that sold me my RFT's? 8)