Vintage EH Clone Theory Q

[Electron Tornado]

I've repaired a 1977 EH Clone Theory for a local guitar shop. I've heard there is an "alignment" that can be done on it. The unit sounds fine, but if there are any numbers to check I would like to do that. (Just dotting I's and crossing T's.) Does anyone have any info on the "alignment"?

[Mark Hammer]

I'm guessing the alignment consists of appropriate adjustment of the trimpots.  The oldest schematic I have for the Clone Theory shows an SAD1024, used as two cascaded 512-stage sections.  There is a 10k bias trimpot on the input to the first section, a 5k "gain" trimmer that adjusts the output level of the first section prior to feeding the second one, and a 1k balance trimpot on the output of the second section to provide for optimal clock noise cancellation.  If the unit works, then clearly you have the bias set right, which leaves adjustment of the section-one output level for purposes of effect-bypass volume balance, and adjusting the 1k balance trimpot for least clock bleedthrough.

[Electron Tornado]

Thanks for the reply, Mark. With three trim pots, that's what I figured, but wanted to find out if there was info on anything specific to measure.

This is an early one, graphics are black and gray (no red), and it has the SAD1024A delay chip.  Two pots show date codes in 1977, and one shows a date in 1976. From what I've found, this is the first version of the Clone Theory. 

Fortunately, the only problem with it was a bad power cord. So I just replaced it with a three prong cord, and it seems to have helped with the noise a bit. I might fiddle with the trim pot for the clock noise, but I know EH stuff has a reputation for having some noise.

[Electron Tornado]

Adjusted the 1k trim, and it was fine where it was, so I set it back to its original setting. Nice chorus. 

[pinkjimiphoton]

these bugs are noisy as @#$%. but NOTHING sounds like them!! NOTHING!!!

i LOVE mine.. still looking for one of the originals with the chor vibe switch (i built one, love it) and i have one with the "edge" switch now, which is nowhere near as good sounding as the originals that you've got.

imho, to improve the noise floor, two things come to mind..
one, a small cap (you'll have to play with the value)  between output and ground to nuke some of the hiss

or, replace the shitty 4558's in it with some nice TL082's or something with a better noise factor.
it changed my clone from nite to day... very quiet, works great~

[Electron Tornado]

This is one of those with the "edge" switch. The edge does just what you suggested. There is what looks like a 1.1k resistor in series with a 0.1uf cap, that the edge switch connects to ground. This is just before the output cap. They are connected to ground when the edge switch is "off". You can hear the slight noise drop and slight high end cut.

[pinkjimiphoton]

those are the later ones, the earlier had the vib/flange switch. it's hard to tell. my original was from around christmas of 1976, and i got it in a trade for my small stone in 77 later that year.

that's not a treble cut!! <g> that's a "treble boost feature!!!"

lol 

[Govmnt_Lacky]

@Tornado

When you replaced the power cord with the 3 prong.... Did you connect the safety ground to the enclosure or did you leave it floating?

[Electron Tornado]

those are the later ones, the earlier had the vib/flange switch. it's hard to tell. my original was from around christmas of 1976, and i got it in a trade for my small stone in 77 later that year.

The Clone Theory isn't as extensively documented as the Big Muff. So the circuit board number, EH 1317A, the date codes on the pots ('76 and '77x2), and the fact that it has the SAD1024A delay chip, is the best info I have.  The photos here show the version I have as "v1". It's the black and gray one at the top left. http://www.effectsdatabase.com/model/eh/clonetheory 

[Electron Tornado]

@Tornado

When you replaced the power cord with the 3 prong.... Did you connect the safety ground to the enclosure or did you leave it floating?

I used a crimp terminal and attached it using one of the nuts and screws holding the transformer on the case.

[Electron Tornado]

these bugs are noisy as @#$%. but NOTHING sounds like them!! NOTHING!!!

I read part of an interview that Howard Davis had supposedly done where he said he was trying to get the best chorus sound, not the quietest. To be fair, I don't recall which specific version of the Clone Theory he was referring to.

or, replace the sh*tty 4558's in it with some nice TL082's or something with a better noise factor.
it changed my clone from nite to day... very quiet, works great~

Did you do that in an old original, or one you built? If I was the owner I might consider doing that. Then I could take those mid-70s 4558s, drop them into a couple of Tube Screamers and charge an arm and a leg for using "vintage" 4558s. (ROFLMAO..."vintage 4558s"....LOL)

[pinkjimiphoton]

the originals had the chor/vib vib/flange switch with the mn3007... and they were the really noisy ones. the "edge" switch came later, i've seen both overlap ...the SAD and the MN version.  i've toyed with the idea of swapping the oa's in my original out and doing just what you suggest.

it drops the noise floor substantially!! but then it's not "vintage".

i suspect the overlap between the two styles of the box came as the supply of SAD chips waned. i don't know if my original had the sad or the mn3007, it's been gone since long before i became savvy enough to check.

if anybody out there has an ancient clone theory that's beat to shit with a replacement knob that says "floydian sound"  and a jp symbol that looks like an infinity sign with an exit ramp on it with almost worn out gold magic marker, well, it used to be MINE!!

LOL!!