Stripe/Serial # (Mark III question)/Preamp tubes

[Skyless7620]

I just bought another Mark III from a forum member. the serial is in the 15,9XX range yet from the pics it's a red stripe. Could it be that it was upgraded to a red stripe at Mesa? I have my doubts that red stripes were found in serial numbers this low. Regardless, the amp is super clean and I got a decent price on it. It would be a bonus if it were a red stripe so I'm curious.

 

[Boogiebabies]

Should be a purple unless it was upgraded.

 

[DaveP]

The description read as follows when I purchased it: "It has updated Reverb, Brand New Mesa 2 6L6/ 2 EL-34 Power Tubes (4) and all new Preamp groove tubes 12ax7 (5). Newly Recapped at Mesa, With A complete cleaning and full servicing. This amp is a Red Stripe / Black Dot Model"
Never heard of a red stripe black dot model. It could have been upgraded.
I did however speak with Mike B on another amp had asked that options/mods were available for the III and he indicated he would upgrade or downgrade to whichever stripe you wanted.

 

[Skyless7620]

Well, after some comparisons with my Green stripe I thought that while both are amazing they are different beasts while still retaining the Mark III lead sound.

The Red stripe I got fixed a lot of the issues I had with my green stripe (some harshness in the high end. The Red stripe has a slightly fuller, more present sound, and is also slightly more defined) but I lost a bit of that "metallic" attack to the notes. This was most apparent at lower volumes so I'm guessing it's a difference in the preamp. I've got groove tubes in this one and Mesa 12AX7s in the greenie.

Are groove tubes 12AX7s any good compared to Mesas?

EDIT: The tubes are GT-12AX7-R, I did some research and it turns out these are lower gain and not the best suit for V1. I'm going to swap it with a Mesa and report back the results

EDIT2: No Dice, the groove tubes actually sound a bit better than the Mesa overall, even if the mesa is a bit gainier... *sigh*

 

[Neptical]

Hey, Skyless..

My red stripe is a completely difference beast all together then my purple stripe. It's definitely alot more gainy then the purple by a long shot. Besides the stripe revision, I think the tubes may be playing a big part in that since the purple is running old Tesla 34s/Mesa 6L6 415s and the red is using the MB STR 440 EL34s & MB 420 6L6s. I've been thinking of purchasing some new SED =C= el34s and 6L6s with some Tung Sol/JJ combos for 12ax7s.

All the Best,
~Nep~

 

[Boogiebabies]

Well, after some comparisons with my Green stripe I thought that while both are amazing they are different beasts while still retaining the Mark III lead sound.

The Red stripe I got fixed a lot of the issues I had with my green stripe (some harshness in the high end. The Red stripe has a slightly fuller, more present sound, and is also slightly more defined) but I lost a bit of that "metallic" attack to the notes. This was most apparent at lower volumes so I'm guessing it's a difference in the preamp. I've got groove tubes in this one and Mesa 12AX7s in the greenie.

Are groove tubes 12AX7s any good compared to Mesas?

EDIT: The tubes are GT-12AX7-R, I did some research and it turns out these are lower gain and not the best suit for V1. I'm going to swap it with a Mesa and report back the results

EDIT2: No Dice, the groove tubes actually sound a bit better than the Mesa overall, even if the mesa is a bit gainier... *sigh*

The Green has the outer sockets wired in pentode. It's louder, less compressed and a bit more percussive. The red has the outer pair
wired in triode which is softer, more compressed and smoother. The red stripe also has a 1000pf/.001uf 1000V ceramic disk bypass cap in C30 which smoothes out
some high treble. The green does not and may seem a bit more brash like the C+. You can add the cap to C30 to smooth it out a bit if you want.
It also sends a little less fizz to the power amp and can help tame some of the pentode wired harshness or wider high frequency you may be hearing.
The bottom end is still going to feel a bit bigger on the green over the red after the mod.

 

[Skyless7620]

Hmm.. interesting, the bottom end actually feels a bit bigger/fuller on the red stripe despite having EL34's in the outer sockets compared to the 6L6's on my greenie. I'm starting to think that the "metallic" voicing of the upper midrange is just specific to the green stripe.

Could any other stripe be rewired in pentode on the outer sockets? From what I gather I like the overall sound and presence of my new red stripe better but wish to add some more "percussiveness", if you get what I mean?

 

[Boogiebabies]

I don't think it's upper midrange it just treble overload. These amps don't clip into distortion the way modern amps do. They use
as much treble as possible and filter a bit to ground to stop oscillation. Most newer amps use cathode clipping, cathode followers and
extra gain stages. On the MK IV when you switch from triode to pentode the bottom end gets faster and a bit more prominent but you lose
the effect of the triode wiring which treats the high end differently and may seem warmer and wider. The C30 mod helps the fizzies. If you look at your
red stripe C30 should be 1000pf and the second resistor (3.3M) below the relay should be bypassed. It may have a 10pf instead of a 20pf like the green.
They both effect the treble frequencies and shift them down a bit. Most of this is really still pretty useless at low volumes. They get smoother with the Master over 3.
Otherwise there will be some fizz in your tone, but a little less prominent with the true Simul wired Red stripe.

 

[Skyless7620]

Alright, understood! Thanks

I'm going to wait it out and keep playing them both before toying with either of their circuits. I could just blend them both with 2 identixcal 4x12's. Somebody say overkill?

 

[Boogiebabies]

I would not touch the red stripe. Adding the C30 is a small attempt at getting the green closer to the red.
When and if you are ready the cap is .15 cents and easy to add.