Debate on Eddie's Plexi

[Ralle]

I would love to hear the differences between a 1.7k 2" Drake and a 2.2 or 2.5k 2" Drake... Anybody knows?
I have Cris's 1202-132 1.7k OT... and it rocks... How would it sound if it was 2.2k?

[rgorke]

you're all about to have your minds changed....you're going to be assimilated and resistance is futile!
That 2.2k 2" Drake is THE OT...soon my pretties...soon.

Do you mean the Classic Tone one?

[StuntDouble]

No, that OT is completely wrong for this sound; that's a hi-def OT.

[somethin'else]

Are you having a custom 2.2k 2" OT made? Am I reading that right?

[StuntDouble]

I had Merc build one and it weren't cheap.

[vanhalen5150]

Just finishing up a board on a 12000. Did anyone ever fiqure out what brand the little blue V1B plate bypass cap was?

[StuntDouble]

Dave Freidman said it was a Xicon. I'm not 100% certain, but I believe it was metalized polypropylene. It's hard to say what sounds best there, because it really seems to varry from amp to amp, but polypropylene film/foil sounds pretty good. According to everyone who saw Ed's amp back in the day; the Xicon at V1b and Arco/El Menco paper mylar caps were added by Van Wheelden, when he re-wired the amp in the mid/late 90s. Either way, I do like the paper/mylar at the P.I. input as well as the polypro at V1b.

I got some Mojo Dijons to try at V1b, but haven't had the chance to try tthem...or anything else in a long time. My Peacemaker came with very similar caps, that are also polypropylene film/foil, and the .0022uf Mojave cap I thought sounded really good there.

The little red polypro caps I found are slightly harsher on the top-end. IMO, the polypro film and foils have the openess with out the harsh highs; I think Strat78 is rocking one at V1b, wheras Ralle is using a .0022uf mustard there. I think it's just one of those little tweaks that will vary depending on how the amp is setup and parts choices elsewhere. It's not a traditional "Plexi" sound, but I tried a WIMA MKP10 there, and it imparts some real teeth to the sound. It's like having some of the vibe from the MXR 6 band when going straight in; very aggressive sounding. They also have an FKP...at least I think that's what it is...series that is Polypro film/foil.

EDIT: I may have been wrong about that Classic tone OT too; the O100JM-VZ isn't hi-fi, but it's more open that a C1998. I think it's worth re-visiting at some point.

[vanhalen5150]

I have a Sozo I'll stick in there first. Got Mustards as well but I'll wait for the smoke to clear on power ups first.

Have some JJ kt77's I want to try with this.

[rgorke]

Dave Freidman said it was a Xicon. I'm not 100% certain, but I believe it was metalized polypropylene. It's hard to say what sounds best there, because it really seems to varry from amp to amp, but polypropylene film/foil sounds pretty good. According to everyone who saw Ed's amp back in the day; the Xicon at V1b and Arco/El Menco paper mylar caps were added by Van Wheelden, when he re-wired the amp in the mid/late 90s. Either way, I do like the paper/mylar at the P.I. input as well as the polypro at V1b.

I got some Mojo Dijons to try at V1b, but haven't had the chance to try tthem...or anything else in a long time. My Peacemaker came with very similar caps, that are also polypropylene film/foil, and the .0022uf Mojave cap I thought sounded really good there.

The little red polypro caps I found are slightly harsher on the top-end. IMO, the polypro film and foils have the openess with out the harsh highs; I think Strat78 is rocking one at V1b, wheras Ralle is using a .0022uf mustard there. I think it's just one of those little tweaks that will vary depending on how the amp is setup and parts choices elsewhere. It's not a traditional "Plexi" sound, but I tried a WIMA MKP10 there, and it imparts some real teeth to the sound. It's like having some of the vibe from the MXR 6 band when going straight in; very aggressive sounding. They also have an FKP...at least I think that's what it is...series that is Polypro film/foil.

EDIT: I may have been wrong about that Classic tone OT too; the O100JM-VZ isn't hi-fi, but it's more open that a C1998. I think it's worth re-visiting at some point.

My chicklets are finally on their way. Tell me more about the WIMA MXP10. Are you using a .0022 or .022?

[StuntDouble]

.0022uf WIMA MKP10's...not for the vintage purists; toothy, sizzly, gritty and mean!
JJ KT77=

EDIT: I think TedB just hit the nail on the head; this is why 100k on the 4 ohm tap sounds like poo with a C1998 or a Drake 1202-132.
http://forum.metroamp.com/viewtopic.php?f=22&t=36908" onclick="window.open(this.href);return false;

...i also think this is why a fat cap doesn't sound right with most OT's.

[plexified]

Still stroking the upgrade you wankers! Cool stuff though. Heh...

[rgorke]

Look unless all you guys are trying this on a 12 series amp you have no idea what it sounds like. Also none of you have a power transformer that is doing exactly what his does either. It sags about 70+ volts with normal wall voltage dimmed and 50 some volts with a variac on it. Also unless you are listening with original 6ca7s everything gets thrown out the window. The real key to get the right sound also is the treble cap. His amp has been restored with all mustards and a 560pf lemco treble cap and a 500pf little red cap out of a 69 era amp for the mixer bypass cap. Also the amp has been rewired with all original period correct wire out of another plexi. Now I have said this before the amp is biased to like 85ma with normal wall voltage and then dropped with a variac to 90 volts. This will bring the bias down to around 50ma. Now the way the feedback is set up and filtering works well with this setup. I was told the amp now sounds like it use to back in the day.

Split cathode V1a 250uF/820,V1b .68/820
All coupling caps are 0.022uF,Bright channel coupling cap is 0.0022uF

470k mixer resistors
500pf [red out of 69 amp] mixer bypass cap
Bypass cap on V2a is .68uF and a 220uf to 470uf
33k/560pF lemco tone stack combo
100k NFB resistor at 4 ohm tap
220k bias splitter resistors
0.1 uF cap on presence control
.022uf output couplers

filtering is
2] 100uf's f&t in series mains
2] 32uf's f&t in series screens
1]100uf lcr phase inverter
1] dual 33 x 33 f&t preamp

I went back to almost this exact spec (my mixer is a 560pf and no "extra" cap on V2a) with the bias all the way up with real 6CA7s and a variac bringing the plate voltage down to 330-340. I kept the PPIMV at 8.5 or so and the Weber attenuator at 9 or so to protect my speakers.

I am not sure how many people actually do clips with the amp wide open but this was a completely different tone than when the attenuator and/or MV is brining down the volume. There was easily enough gain for ALL the early albums with me just going straight in.

I guess I bring this up because of some posts I read on another forum from a certain former member here still talking about some magic distortion pedal. For obvious reasons, we don't run our amps full bore with no attenuation but the plexi is a completely different animal at that level. We, collectively, are getting fantastic tones at many different volume levels but I wanted to give another nod to this spec. It sounds good at low volume but in a different world with nothing holding it back.

[Ted B]

For obvious reasons, we don't run our amps full bore with no attenuation but the plexi is a completely different animal at that level.

What obvious reasons?

I don't even own an attenuator.

[rgorke]

For obvious reasons, we don't run our amps full bore with no attenuation but the plexi is a completely different animal at that level.

What obvious reasons?

I don't even own an attenuator.

Well, because I don't gig at places where you can run a 100 watt plexi unattenuated or w/o a master volume.

[Strat78]

There were two very important events this month here at metro:
1)The "Debate" thread is now a sticky,
2) http://forum.metroamp.com/viewtopic.php?f=42&t=37944" onclick="window.open(this.href);return false;
Life is short and beautiful, fire up those irons and lets build!