EVH Chassis Layout

For all things to build the brown sound

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Ralle
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Re: EVH Chassis Layout

Post by Ralle » Thu Aug 16, 2012 6:27 pm

Hrrmm... would just like to say a few words on the matter...
As you may know, I have been leaning towoards the Plaap/ C***** speqs regarding the early sounds... basing that on the info and what I could hear from the amp... the info would be that there were a few oddball values for Marshall ( they didn't allways follow the schematics )... well, that fitted just fine for the Plaap/C speqs...

Here are the different out of the box infos on the amp:
1. One small tone/gain change
2. One added part for more bass in the treble channel
3. Oddball values for Marshall

Nr 3 goes for the Plaap/C amp... 1 and 2 is the amp that Dave F and John Suhr is takling about...

My two cents are these:
There are two things done to the amp... one (a) that makes it possible to dime ALL controlls... eaven the bass controll ( not Vol II )... and one (b) that makes the lead channel a bit bassier...

The (a) mod is something he might have done to all of his amps... and the (b) mod is something he might have done to the amps with a split cathod arrangement...

Again, this is my thoughts ( theories and guesses )... and I'm only aming towoards the early sound... before and during the first album... NOT after the first album... Im saying this because all the info on the NFB ( 100k/4 ohm in the Dave F speqs )... wich I belive was different from the beginning... And wich, btw, is one of the two things that has been discussed regarding any speq changes: the preamp, screen filterings and the NFB curcut...

Seams we have two amps to choose from: the Plaap/C amp or the Dave F/J Suhr amp...
Hmm... was it J Suhr that said the 12301 amp went to Plaap... cause that's not the amp that he ( Plaap ) or C**** describes...

Strange...

Anyways, I'm back on the Dave F track... the Plaap speqs sounded great, but with these two things done to amp, it sounds better with the Dave speqs... :wink:

CircuitBurner64
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Re: EVH Chassis Layout

Post by CircuitBurner64 » Tue Sep 10, 2013 12:21 am

Hello all,
I know this is an aging thread but I'm finely in a place in life where I can get back into playing guitar and chasing the legionary EVH sound.
I'll be up front and say I am from another planet as far as all the back and forth change this and change that and who did what mod when and where. And the upper echelon of amp builders seem to mainly deal with the HO amps.

I'm not going to be gigging anything. My problem seems to be the same as EVH. I need something I can get a good sound from at lower levels and still stay married :wink:
I want to build a good tube amp that can get me in the ballpark of the early EVH sound with out having to double up on credit card payments to pay off.

I have heard so many different amp kit samples that they all seem to sound the same now.

Nothing is ever right as soon as it is put together. SO I know I'll have to do some tweaking. But what is the best starting point? Who puts out no BS kits that will be a good jumping off point? Can someone point me in the right direction?

Aside from that. I have to say the reading was exciting and cemented the fact that I need to go with a tubed amp to get some feeling in my playing.

Thx,
Kev

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Tone Slinger
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Re: EVH Chassis Layout

Post by Tone Slinger » Fri Sep 13, 2013 6:35 pm

If you follow some of the build threads you will be on the right track. I'd suggest maybe a 50 watt build (or even an 18 watter). You could suss out everything with Valvestorm as far as what you need.He has most of it. You could buy a Plexi clone here in the classifieds, some show up from time to time. Obviously if you combine a 2203 front end along with a PPIMV using a super lead foundation, then you can get at low volume Brown sound galore.

Honestly though, if you want immediate gratificationin terms of 'low volume' Brown Sound, I'd suggest maybe a 'newer' Marshall. The JCM900 series, like the dual reverb models, get a real good brown sound at super low volumes imo, and can be had for around $700 to $800. The 'vintage/Modern' as well as the JCM 2000 models are also real good and can be fetched for a similar amount.
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NY Chief
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Re: EVH Chassis Layout

Post by NY Chief » Tue Oct 01, 2013 11:26 am

or build a brown sound in a box! :o

Actually it's a fun pedal.

http://www.generalguitargadgets.com/pro ... 05-bsiab-2" onclick="window.open(this.href);return false;
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Tone Slinger
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Re: EVH Chassis Layout

Post by Tone Slinger » Tue Oct 01, 2013 1:01 pm

Sweet, thanks for the link :thumbsup: . I've been interested in a dirt box that is capable of turning most any amp into a useable distorted tone. Obviously certain pedals I already own/built work good,but they are dependant on what amp is being used,like for ex. my tubescreamers,D+'s and 250 style boxes need help from the amp. This one you posted sounds very interesting.
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Re: EVH Chassis Layout

Post by Jeremy1283 » Fri Aug 22, 2014 2:38 pm

mightymike wrote:Here's 3 eyewitness accounts:

(1) By Mark Cameron by pictures taken in the early 80'S.
There ARE small tone altering and/or gain altering mods.
I do have pic's so I CAN physically see that the amp has a split cathode arrangement.
...the cap on v2(330uf) cathode.
...its a 2.7k/.68 and the resistor looks like the stock part(but I don't think it is)but the cap is one of those yellow square type from the 70' Marshall's. From the circuit card It looks like it came stock with this arrangement. The post that is pressed in looks stock too witch tells me more than anyone could.In the pics the serial # is 12301.


(2) By C errem. 1980.
To try to wrap up is ED thing...
His head was a 67/68 and he had the first stage valve with BOTH cathodes tied together sharing the same 820 ohm resistor that was bypassed with a 330uF blue cap...

His treble cap was a round shaped ceramic that was a 250pF that said MURATA ... With 56K on the tone circuit feed..

One of the 470K mixer resistors was bypassed with a round hollow tubular MURATA cap 500pF... If memory serves me right on the value, or it was a 330pF..I will check my notes....

The real kicker, his phase-inverter "get-rid-of-the-FIZZIES" cap was a 100pF instead of the normal 47pF ....and this my friends is how the "brown sound" with that added compression happens..

Oh, BTW those 820 ohm resistors were carbon-comp and drifted in value up about 1.1K and make the amp much more gainy and warmer, since these re-bias the 12AX7 valves in a bit more non-linear region..

I am pretty sure the feedback resistor was a 47K ...I will have to check my notes...

The filter cap in the center of the board was a dual 16uF gray RS cap...

The screen filtering was 2 DALY 32uF light-blue caps in series... The voltage doubler were 2 100uF DALY royal-blue caps...

Rear cap on top of chassis was a royal-blue HUNTS 32uF or 16uF...need to check notes..

The value of the coupling cap between V1 and V2a....022uF.

At least that was what it was in 1980...


(3) Plaap (a friend of Peter Van Wheelden who restored Eddie's amp.)
Edwards amp's internal measurements were as follows:

1.The first 820 ohm resistor (carbon type) measured a little over 1K. It was bypassed with a blue 330uF resistor. can

2.His treble cap was a 250pF Murata flat ceramic one. The cap across his 470K was a Murata hollow round 330pF. cap

3.His second stage 820 ohm (which also measured a little over 1K, was also bypassed with the exact same type 330uF blue colored cap that was on the first cathode resistor.

4.The filtering caps for the middle of the board were gray colored RS caps that had dual 16uF values.

5.The screens were 2 blue caps in series (DALY 32uF's).

6.The voltage doubler were two big blue caps (100uF DALY's). The one on the outside was a blue Daly - and was a single 32uF.

7.The feedback resistor was a 47K of unknown origin.

8.His power transformer was the smaller one of that era. His OPT was also the smaller one with 1.5" stack.

The amp was either left stock into a load resistor or, a big Ohmite(or other) power resistor was placed somewhere in the circuit to cut the power of only the output stage meaning Sylvania 6CA7's were the only valves to hold up to this.

If this is true - doesent this kinda dispel the whole 'special' 67 slp 100 myth ...as almost all amps of that year had pretty much identical configurations (with the small exception of the 330uf cap on the second preamp stage?

Dankuwell !(dutch for many thanks)
Plaap

Update: 12-22-10
I have a 3 version animation I drew up a while back. It plays in this order: C errem's description, Stock67 (With Split Cathode), and Ralle Spec (as it was back in 2005).
http://i213.photobucket.com/albums/cc16 ... mation.gif

If you watch it changes to the different specs, and reveals under board wires. The way to tell which is which: The Ralle Spec has the 4 100uf Caps on the Power Board, and the C errem Spec has the 100pf fizzy cap at the Phase inverter instead of a 47pf, and the other is Stock.

Warning: there where some mistakes in my drawing. I fixed them, but when my Desktop died all I could find was this older one.

1) Missing Green wire on V3 PIn2 goes to the 1 meg on the board to the left of the 470 ohm resister on the board. I forgot to draw it in.
2)One of the input jacks is wired wrong.See how I ran the black wire to the wrong terminal on the jack
on the bottom left? The one to the right of it, is how it should look.
3)and on one of the 1.5 K resistors on the Power tubes are to the wrong terminal on the right side

If you open the file up in a Graphic program you can see each frame and print individually
Thanks for the info!

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roylfuchs
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Re: EVH Chassis Layout

Post by roylfuchs » Wed Aug 27, 2014 8:38 am

Can someone tell which tap to connect the negative feedback to?
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Re: EVH Chassis Layout

Post by vanhalen5150 » Wed Aug 27, 2014 10:43 am

roylfuchs wrote:Can someone tell which tap to connect the negative feedback to?
I think that personal preference. I know a lot of guys like the 4ohm tap.
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Re: EVH Chassis Layout

Post by stef » Wed Aug 27, 2014 1:36 pm

According to me recent findings the NFB tap depends on the pre amp tubes, among other things. With bright and hot (overdriven) sounding 12AX7's in V1 and V2 the 16ohm tap is the right choice for me, as opposed to mellower sounding pre tubes when less NFB can sound better (for :vh: )

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Re: EVH Chassis Layout

Post by roylfuchs » Fri Aug 29, 2014 8:58 am

I can't seem to keep my mod 5 2203 from sounding flubby when I dig into the E string. I haven't lowered my filtering yet. Does anyone have any suggestions?
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Re: EVH Chassis Layout

Post by stef » Fri Aug 29, 2014 1:46 pm

Yes: higher NFB, 22nf PI ouput caps, 9-38 strings etc.... the ultimate MOD would be the stock 12xxx 1959 spec, though :wink:

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Re: EVH Chassis Layout

Post by Grosh_Guitars » Wed Dec 03, 2014 8:08 am

roylfuchs wrote:I can't seem to keep my mod 5 2203 from sounding flubby when I dig into the E string. I haven't lowered my filtering yet. Does anyone have any suggestions?
Is this amp a real Marshall 2203? lowering the filtering will not tighten up the sound. If anything it will make it more squishy or compressed. Let me know if its a real stock 2203. there are two changes you can do to the circuit to tighten it up like a super lead.
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Re: EVH Chassis Layout

Post by mightymike » Wed Dec 10, 2014 3:54 pm

Here's a working link to that layout. http://www.mediafire.com/view/i4z59v958 ... mation.gif

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Re: EVH Chassis Layout

Post by uiovbged332 » Wed Jul 06, 2022 12:18 pm

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