Plexi Power!

flemingmras · Post by **flemingmras** » Sat May 01, 2004 9:53 am

Hey Mke! I think you just helped me figure out why one of my ST Marshalls sounds more aggressive than the other!!!

Spinal Tap #1 sounds a lot smoother than Spinal Tap #2 I've noticed. However Spinal Tap #2 was built before Spinal Tap #1(it JUST became a Spinal Tap Marshall since I just switched the panels on it when I replaced the OT). I am thinking this is because Spinal Tap #1 has more soak time than #2. #1 has never been ran "gently" except for on 1 gig. So that head has about a good 8 hours of soak time as this head has been pretty much soaked since I built it. However I couldn't keep Spinal Tap #2 on a soak long enough to give it any soak time as it kept blowing on me everytime I did it! This is due to when that Jager Bomb got spilled in it two of the tubes(the ones closest to the preamp tubes) literally went into meltdown and the plates were glowing bright orange when the spill happened so this excessive current draw fried one side of the OT partially to the point where at low volumes it would work fine but as soon as you start soaking the amp and running it real hard it started blowing tubes and shit! Well, I replaced the OT and all the power tube sockets(basically overhauled the entire output section) and soaked it at a gig last night all night long and NOW it's running great on the soak.

So because of this lack of soak time compared to #1 I'm noticing that #2 sounds fizzier than #1 so since you mentioned your above post I have come to the conclusion that #1's Sozos are farther along in their break in process due to it's higher soak time. George did say that it does take about 100 hours of playing to fully form these caps so I'm anxious to hear them once they're all formed.

As far as him preforming the caps, that would mean that he'd have to take ALL his Sozos(and believe me he stocks A LOT of them) and run them on a signal generator for 100 hours. Unfortunately I don't think he has time to do this.

Jon

Flames1950 · Post by **Flames1950** » Sat May 01, 2004 4:20 pm

Bluefuzz--to my ears they've loosened up quite a bit, although I've ordered a pair of the GT KT66's from George to try and get even more "touch" out of my Marshalls. I think the current production EL34's I've tried are holding back my '78 head, they're too harsh in the upper mids and don't soften down enough when you back off. I'm hopeful that the KT66's will help with that, otherwise I'll put my GT E34Ls's back in it, which I do really like still.
I think it was Gnugear who said John(?) at SoZo told him to idle the amp with the tubes pulled out (standby on, just like if you were playing) and let it sit and break the caps in that way. I idled my amp a couple times with the tubes in, just turned it on while I was working on something else, and let the SoZo caps "cook" that way as well. Try it and see if it helps break them in quicker.

flemingmras · Post by **flemingmras** » Sat May 01, 2004 4:55 pm

Actually I think what would break them in quicker is letting it cook, but with a signal generator running through the amp with the volumes cranked. This way the caps now have a full high amplitude signal going through them which should help form the dielectric. Set it up for a 1kHz 100mV signal output, plug it in and crank it. Make sure the poewr tubes are out though. If you decide to leave the power tubes in make sure the amp is on a dummy load that can handle at least 200 Watts. Big ceramic dummy load resistors perform this job just fine and they're only like $10-$15.

Jon

bluefuzzguitar · Post by **bluefuzzguitar** » Sat May 01, 2004 5:30 pm

[quote="Flames1950"]I've ordered a pair of the GT KT66's from George to try and get even more "touch" out of my Marshalls. I think the current production EL34's I've tried are holding back my '78 head, they're too harsh in the upper mids and don't soften down enough when you back off. I'm hopeful that the KT66's will help with that, otherwise I'll put my GT E34Ls's back in it, which I do really like still.[/quote]

I'm partially responsible for this KT66 'movement'. It was for the very same reason. Current-production are in fact holding back the Marshall sound because they tend to emphasize the upper mids too much, you're absolutely right. I'm sure you'll like them! Let us know how you experience the GT KT66's. I'll be sure to report back about the SoZo's progress. Thanks, guys!

Mike

Flames1950 · Post by **Flames1950** » Sat May 01, 2004 9:35 pm

I'm partially responsible for this KT66 'movement'. It was for the very same reason. Current-production are in fact holding back the Marshall sound because they tend to emphasize the upper mids too much, you're absolutely right. I'm sure you'll like them! Let us know how you experience the GT KT66's. I'll be sure to report back about the SoZo's progress. Thanks, guys!

Yeah, you are sorta to blame for it, and frankly I never would have suspected current production KT66's to be that good. I hope they live up to you and George's hyping (I suspect I can trust you kids to know if they sound good!)
Then the question will become, "If they can make a decent KT66 why the hell can't they come up with a decent EL34?" So far the Winged "C" tubes are the best sounding current production EL34 I've got, despite the bad batches going around. OK, I really like my GT E34Ls tubes too, but that comment will bring Jon in screaming here any minute!!!

bluefuzzguitar · Post by **bluefuzzguitar** » Sun May 02, 2004 10:51 am

The KT66 experiment is one thing and it's definitely a success. In the future I also want to try and experiment with 7581a's, 6ca7's, or even KT88's, basically any big-bottle, military-style tube with a 6L6 flavor and lots of clean headroom (though not as much as a 6550). I'm currently stocking up on those tubes. Once the KT66's have had, which hopefully won't be for many months to come, I'll replace them with 7581a's first, I think. Anyway, I'll keep y'all posted when the time comes.

Mike

bluefuzzguitar · Post by **bluefuzzguitar** » Tue May 04, 2004 11:01 am

Going back to the SoZo's, I guess what I'm lacking most of all right now is top-end sparkle, something the Mallorys do provide. Can anyone shed some light on Mallory vs SoZo in this respect? Is this just down to the burn-in factor and should I just be patient or are the SoZo's just lain darker-sounding than the Mallorys?

Thanks,

Mike

Post by **VelvetGeorge** » Tue May 04, 2004 11:31 am

Mike, I've found the Sozo's to be every bit as warm as the Mallorys, but with better clarity. This was apparent for me as soon as I installed them.

As they broke in, they just got sweeter sounding. I can't imagine losing any sparkle with them. It might be worth checking them to see if one is leaky or out of spec. I haven't a single bad one in several hundred, myself.

George

Flames1950 · Post by **Flames1950** » Tue May 04, 2004 12:50 pm

I've not had a lack of sparkle either. The amp with SoZo's chimes really nicely.....
ESPECIALLY WITH THESE KT66 TUBES!!

Damn these tubes are cool, kind of like finding the perfect middle ground between a cranked Fender and late-seventies Marshall scream.
At long last I have a Marshall amp that CRIES.
Had to change the bias resistor though. Hit the standby and even with the bias voltage as negative as it would go, I couldn't get these things to draw less than 81mA. Subbed a 100K for the 47K and got the range in line, although I'm almost at the top end of that range.
But who cares about how I got it there, these pups are nice and glassy and more balanced out than the EL34's I'd tried, more high end sparkle than the GT E34Ls tubes. They're killer.

Post by **VelvetGeorge** » Tue May 04, 2004 1:34 pm

Glad you dig em Flames! I agree 100% on your findings.

These things can be sweet or nasty depending on how you slap them.

When I catch up (that will happen

) I want to build a JTM45/100 type amp with KT-66's.

George

bluefuzzguitar · Post by **bluefuzzguitar** » Tue May 04, 2004 5:37 pm

Join the KT66 club, Flames! Aren't these tubes waaaaaaaaaayyyyyyy cool?

George, I've read reports on Plexi Palace about the SoZo's being fuzzy in the highs at first. You didn't have that experience, I did. It still sounds like this is not an abnormality and to be honest I've only tried them for three gigs, the third being the one where the caps' top started to open up. I guess I'll just hang in there for a few more gigs before I'll have the SoZo's looked at or even replaced. I guess I'm just an impatient sumbitch! To be continued...

Mike

Flames1950 · Post by **Flames1950** » Wed May 05, 2004 12:48 am

Incidentally, the KT66 tubes have also turned that Marshall into a Texas blues MONSTER with a Strat. I can even still use the treble knob, and small animals aren't burrowing for safety.

flemingmras · Post by **flemingmras** » Wed May 05, 2004 12:55 am

Flames, did u just use Fender and Marshall in the same sentence? OUCH!!!...Oh wait a minute, Jimi Hendrix did that OOPS!!!

Why the hell am I even posting this? I just proved to the world I'm an idiot!!!

Country Boy Shane · Post by **Country Boy Shane** » Wed May 05, 2004 3:01 am

Yes that was a good one John... better watch yourself next time!

bluefuzzguitar · Post by **bluefuzzguitar** » Wed May 05, 2004 8:19 am

[quote="Flames1950"]Incidentally, the KT66 tubes have also turned that Marshall into a Texas blues [b]MONSTER[/b] with a Strat. I can even still use the treble knob, and small animals aren't burrowing for safety.

[/quote]

Yeah, 'Texas Blues' is how I would describe my Super Bass with KT66's as well. And since that's the style of music I'm coming from and my other influences include early Clapton, Paul Kossoff and Duane Allman I guess you can see why these tubes fit my style to a T.

I have found that basically any good-quality tube sounds fine in a Marshall, it's just a matter what sound suits your taste and style. For me it's a 6L6-type sound with increased headroom (though not as much as a 6550). KT66's certaintly fit the bill but I'm pretty sure I'll get equally good results (though slightly different in character, of course) with 7581a's or 6ca7's. These tubes are next on my list (I already scored a quad of 7581a's) but I won't replace the KT66's until they're worn to the last filament. I don't mind if my Marshall experiment takes me a few years. It'll be fun using up tubes and then swapping them out!

Mike