******'s Mod

[chrisom]

I bought one of those load resistors from the link Blix posted (haven't used it yet). It probably doesn't make any difference, but it was an 8-ohm resistor (300 watt), not a 16-ohm. It's also listed as 8-ohm in part of the link he gave. Just an FYI ...

Total load and line out amplified, this is the resistor I bought:http://www.ebay.com/itm/8-OHM-300W-Non- ... 1e6e215af6
And yes, this made me question those expensive attenuators indeed, when a simple resistive load does such a fine job!

And the link still works, after all this time- I just tested it:
http://www.ebay.com/itm/8-OHM-300W-Non- ... 1e6e215af6
I did an eBay search, changing the title to 16-ohm. They do offer those as well, but they are only rated at 100 watts. Still, 4 of them in series-parallel like a 4x12 could be cool, or 2 of the 8-ohm ones in series...

[dirtycooter]

Both of these resistors look awesomely tempting. I am just leary of buying from china overseas.
Those guys may not ship right ohmage or something. I was lookin at the duty cycle of the silver aluminum one-1 min on then 30off?? Scary if thats what I read right.
"Ahhh good choice cowboy, last you loooong time"
Maybe I will snag a hotplate if I fnd a deal cheap. Hunting right now

[dirtycooter]

Ha!
I just snaggatized me 4 100watt 16ohm resistors for a grand total of $20.40 w/free shipping Should be safe enough you think?? 400watt total?? Beats the dogshit outta spending $200-300 on a hotplate for a test run.
Now I need to turn on the plexi in the morning and see if it still fires up after sitting for two years now. Should be gone through as its about 10-11 years old.

[chrisom]

"Ahhh good choice cowboy, last you loooong time"

[dirtycooter]

Ah HA! So re-readin the article sounds like the load used was indeed a "reactive burried speaker type load" during bradshaw days. The reisistors while working for me and intended purposes sounds pretty cool. But something is askew though to my ears and not quite regular amp response.

Hmmm..... time to put some high powered speakers in a sound proof coffin I think, tap the line out signal and re-examine my slave amp used. It should be the best possible way to maintain naturalness here. Far surpassing any attentuator.

[plexified]

Hey Gang ,
Kinda back after being hit by a car on my mountainbike , no fun . But to chime in , ****** had some pretty great ideas and on not often looked at was the use of the variac in a very unique way . I first must say I have an original 12 series and surp Hrisingly it usually sounds the same with mods , without mods , including this one ... Chirs suggested to use the variac form the speaker output > into the varic set at 90 and then sent to the speakers . Yes you read it correct . Here you have to fabricate the speaker output jack into the two prongs and not the ground . And out to your speakers . I have done it and Chris said it halves the output and impedence matches . I actually tried it and guess what ? It sounded exactly like that harmonic rich sound on Push Comes Shove ! Shimmering and harmonic laden nirvana ! I was crazy enough to try it and full volume and all into the period correct cab it absolutely slays ! Just food for thought . I think the stock head variaced to 110 to correct the line voltage is the ticket . I variac to 90 and honestly its really indiscernable on the stock head . WHY ? Because all the sag we seek is actually in the power transformer being asked to provide more instant peak power and THAT is what gives the spongy sag and quality that never goes away , mods , a lot of them tried , and really never escape that inherent engineering signature . Happy New Year ALL . Shannon , I did not forget you that pickup is coming . I was in the hospital for a while with a dislocated shoulder broken ribs , collar bone and clavical . No fun , but I am a tough SOB . Stronger soon even ! Ha HA , David

[jnew]

DAMN! Sorry to hear that and I hope recover quickly bro. I hope the driver was cool about it and didn't pull the cowardly Hit and Run routine. Missed ya.

So the variac is still powered up at 90VAC? And you're tapping off the speaker cable into the AC outlet of the variac with it turned on?

Also, when you say halves the output and impedance matches, is this the same as the head on 8 ohms into a 16 ohm cab, for example?

As always, great insight brutha.

[plexified]

J Thanks for the kind words , the guy never knew he hit me , I will be better . So to the nuts and bolts ...... The Wiring is just a plus and minus using the two blades on the variac . Have to make a connection to do it . In and out . The 90 rating on the variac is perfect to mend the minds of the units . Pretty ironic for sure . BUT Chris is so much of a professional and a great engineer that if its good enough for NASA its good enough for me . And the impedence is exactly the same . You like 16 with one cab like me , then that's OK . Its equivalent . I had found so much shimmer and harmonic it was enlightneng exactly like Push Comes Shove . Chris pointed to mods that identify with periods of EVH . I used his mod BTW on my bone stock Plexi 12 series and period correct cab and it was nailed VHI or VHII. All there . The other mod that Twisty did is also a shocker and spot on . Man Chris was just spewing the truth and we all just turned our heads BUT , I can say this , my 12 series is bone stock and has been modded and tweaked by me to no end and the end result is that it still sounds the same wide open ..WHy ? Because the power trans drops like 60 volts on a power chord . In other words its like a sag monster . Like a tube almost . So any mod means shit . The ****** mod like I spoke of shimmers and sings with harmonics , yet the same sag is there . That's the butter in the ED vibe . No variac at 90 is gonnna get it no mod . etc etc . I just gave up the goods . The roadmap that Cerrum gave is spot on . I modded his specs and BOOM . I modded his Variac mod and BOOM (VHIV) and the stock specks killed . The Twisty Mod with the resisitors too . BOOM . The guy makes transformers and that too , BOOM . Get it ? Good enough for NASA good enough for me man . Chris is an engineer . A freakin NASA engineer . He builds shit that makes the space shuttle work . Its gonna be enough for my amp . Get it ? Plus he is a total vintage amp / guitar guy + 40 years get it ? He is THE MAN . NO SHIT . I am a friend of Ken Fischer (R.I.P) and those guys were buddies . I have schematics for transformers from long lost times from Ken and Chris . Most from Chris were from Ken . And they shagged the details of a lot of the transformers Chris winds today . Done . No bullshit , just the shit man . J the reason why my stock plexi sounds the way it does is , oh man this is secret shit . Its because of the power trans . It drops voltage when a big demand on it presents itsef . So it cannot hide , even when modded . The ****** variac mod is just a texture added to a killer amp . You cannot buy a power x transformer that performs like this . Get a Bedrock and experience an amp where the thing is so over engineered that it sounds like solid state , Get it ? I know you do . Love you man , get those kids painting some more guitars for you , now that's talent ! David , I gave up the goods after ten years you all better get it, dumb fuckers , I made it so plain in the light to see . Even then then there are so many more secrets you soooo missed . Search my posts and learn ...!

[plexified]

I should have mentioned that a 68 period plexi is designed for a 110v wall voltage . Usually a variac is used to dial in the wall voltage here . I find 126+ all the time. The power company force feeding you voltage for $$ . Give your vintage amp a 110 or 100 to be safe before you do anything . So you probably need two variacs to do this stuff . Not a bad idea since you can get them for 100 bucks . The best thing you can do for a vintage amp . Wll voltage can be as high as 130 or more as the elec co is a scam to force feed you for $$ and destroy your stuff plugged in all the time . Next , I cannot advocate the results from the previous described experience . You are on your own . Realise bias in tubes also changes with voltage too and changes tone a lot in a sensitive amp and can hurt tubes . Variac to 90 like the EVH rumor and you have to re bias . Its a huge tone change when you change bias to tubes . You can tune it to tast for sure , but know what your doing . Some tube sets are hundreds of dollars and a toasted experiment is hundreds more and down time . Dial your amp in with proper voltages first . This is where a variac is used best . Dial down the wall current from usually 125+ to 118 if modern and proceed . The variac is best used to regulate wall current in your favor , not to find tone . The 90 volt myth is just that , a myth . Not much to be found there . Just saying . Lower your pickup before the voltage . Dave knows tone , trust me .

[plexified]

FWIW, You guys are chasing a bunch of stuff , here it goes . ... Ken Fischer modded a bunch of plexis in several ways and Ken was THE GURU . He took a plexi to tame by using 6v6 tubes . H e also used slaving ala EVH by using a 50 watt loaded with a resistor into a 100 watter . Eventually he took a bassman platform to tweak and it was a 50 watter and tweaked the front end and back end for the VHI tone . So the level of VH one sound is very vast . He also loved a pedal called a hotcake which is a fuzzface variant . So the secret pedal theory and the slaving is very valid , as well as the 6v6 tube option . It was about lowering the volume or control to aide Daves vocal weakness live . And don't forget t he pics from VHI on the album cover shoots with Zloz that had ED holding a Les Paul Junior . Fully loaded P-90 axe . Same clothes and smear . I have the pics . Do not forget it .That axe screams VHI all day long . I have the amp , the guitar , the pics . the tone . For days ..Just Sayin. We all get too far off sometimes thinking what was.... and do not forget vinyl trumps digital all day long .....David

[JimiJames]

Good stuph here man, and based on that, I most definitely damaged my trannies. Ever since we moved to the new (factory) building my amp & tone has suffered and has never sounded the same. Not realizing until it was too late, checked, and voltages near 135.Opportunities for tweaks were all there and many were done. It has gone from a near stock '69 SLP to a 12 series and all for naught. I haven't played this particular amp for nearly a year because the tone just sucked no matter what (tweak) I did to it...

[jnew]

HOLY SHIT! OK, I'm gonna have to have some Armenian coffee and go back and read all that.

Starting with Chris. That dude is "THE MAN"! No doubt about it. I've had many conversations with him at this point and many of our chats are about shit outside of amps and tone. About 3 years ago, I was at work offshore and we had a 35KV transformer blow up. I was about 15 feet from it when it did. It was so loud, the shock wave about blew my hard hat off my head. I though my life was over, it scared me that much. He designs and builds shit like this, and even bigger. He talks about all the tension and stress he feels in the same way, when he does startups with some of his big ass projects. Stuff that will make you real dead, real quick. There should be no questioning or dismissal of his information in any way. "HE KNOWS HIS FUCKING BUISINESS". And he's far too engaged to be toying around with any bullshit rumors, mod theories or the like. He is not one to perpetuate shit that isn't either fact or personal experience, PERIOD. In fact, recently, he's the only guy who has been able to clearly explain the polarity/death cap concept on the Marshall's made for the U.S.from back in the day and I researched the shit out of that subject for almost a month. One e-mail from Chris and "BOOM" as you put it. Anyway, more to come on that issue later.

I used his transformers in my new build and his PT has 100V, 120V, 220V, 230V and 240V primary options. Unlike the originals which were designed for 105V-110V's (U.S. option), I think using his PT with the 120V tap would be the equivalent of an original (like yours) with the variac at 110V's because Chris knows this and designs his stuff with this sort of knowledge. But I use a variac anyway so that I can ensure a true # regardless of where my power source is. It's a small one too, 5 amp. I'm going to buy another one and try the little stunt you talked about (Only calling it a stunt for humor. You know I love ya bro, no disrespect here). But I'm still not clear on the wire mapping. Seems like two ways this can be done.

1) The speaker out's tip and sleeve wire nutted to an AC plug that plugs into the blades of the variac and within the wire nuts are the tip and sleeve from the cab.

Or:

2) The tip wired in to one blade of the variac as sort of an "IN" while the other blade acts as an out for the tip to continue to the cab, while the sleeve leg runs straight from the amp to the cab.

Either way seems friggen nuts but if Chris signs of on it, I trust it's good info.

[Strat78]

It's always good to hear from you David, glad your OK!
Yep, David got us all going on this a couple years ago. Here is a good thread on using the variac between the head and the cab. I think I might go back to this as well, still have all my extra variacs and converted cables etc...
http://forum.metroamp.com/viewtopic.php ... 5&p=335284

[jnew]

I'm still confused. Do you run it like this?

(deleted diagram so that it wouldn't be used)

[mightymike]

.