1979 Op Amp Muff Questions...

[Gristlepig]

Just curious what y'all think...

So I just recently got a 79 Op Amp Muff for a good price and I'm dissatisfied with it's performance. It sounds great, but the bypass boosts my clean signal significantly, thus when engaged the effect has a volume drop.

I don't really need to keep it, as I've built a couple of IC Muff clones which sound great as well.

Now, I could throw a dpdt in there and mod it to true bypass, but if I do so, will I diminish it's value?

My other thought was perhaps seeing if Howard Davis still does Muff mods and have him do the job; my thought being that the pedal's value would be preserved if the guy who designed the circuit did the mod... But it seems kinda silly to send a pedal out and pay for work I could easily do myself...

Or I could just throw it on ebay for $200 and see what happens...

I dunno... what do you folks think?

[pinkjimiphoton]

Just curious what y'all think...

So I just recently got a 79 Op Amp Muff for a good price and I'm dissatisfied with it's performance. It sounds great, but the bypass boosts my clean signal significantly, thus when engaged the effect has a volume drop.

in bypass, it's not boosting your signal. it can't, in bypass, in fact. the most it could do would be suck some of your signal away. what you're describing is a volume drop problem when it's engaged, which is totally different.

I don't really need to keep it, as I've built a couple of IC Muff clones which sound great as well.

Now, I could throw a dpdt in there and mod it to true bypass, but if I do so, will I diminish it's value?

yes, it will diminish it's value somewhat. any change you make to an original will diminish it. that said, there's zero reason you can't true bypass it carefully, and keep the original parts so you can restore it to stock. it WILL lose *some* value, even then, tho.

My other thought was perhaps seeing if Howard Davis still does Muff mods and have him do the job; my thought being that the pedal's value would be preserved if the guy who designed the circuit did the mod... But it seems kinda silly to send a pedal out and pay for work I could easily do myself...

even if howard does it, it's modified. modified is modified. if you like the pedal, but just want it a little louder, you can play with the circuit and definitely get more volume out of it.  it depends whether you intend to keep the pedal, or turn it over. if it's worth more to YOU, do the mod yourself. if you can live without it, sell the thing.

Or I could just throw it on ebay for $200 and see what happens...

I dunno... what do you folks think?

i'd go ebay, if you have ones you've built that you like better.

[Gristlepig]

Hey, thanks for the response...

I may just go Ebay with it... I dig the cool vintage look factor of it and love the sound, but I do have a couple plain old 1590BB boxes that do the same thing louder and with true bypass. ...they just don't look nearly as cool.

As for the bypass, it definitely does boost and color the clean signal. The bypassed signal runs through those opamps which bring the volume up considerably. Apparently it is a trait of this circuit and, from what I've read, is a common complaint.

Or maybe I'll just track down a cool looking Carling DPDT switch and just wire it for true bypass; so long as that doesn't involve cutting traces. I just hate the look of a big old blue 3PDT under the hood of a vintage pedal...

[pinkjimiphoton]

i could see it coloring the bypass, but not boosting it. the output of the opamps isn't connected to the output jack in bypass, even stock from what i see.

gotta schematic for this particular beast?

i'd be very very surprised to hear it "boosts" in bypass.

[Gristlepig]

I found this schem
http://sovtek.webs.com/apps/photos/photo?photoid=77120321

It's definitely boosting in bypass. I put it in a TB loop to verify it. And the output is still pretty weak from the true bypassed tone.

So I decided to put it side by side with an NYC Muff I recently modded to Violet Ram's Head specs, and wow... The IC Muff is kind of a tone turd. Not nearly as much volume, and sounds weak and thin in comparison. There's definitely something going on here... I'm gonna have to crack her open and poke around... I'm sure there's some cold solder joints going on (at least)

[Gristlepig]

I'm beginning to suspect dried out electrolytics might be a factor as well.

Think I may be off on that? Pots date it to 1979.

[pinkjimiphoton]

+1 on the bad electros. probably bring it back to life.

still hard to believe it would make your signal louder in bypass, even if using a buffered bypass system.

weird.

[Pyr0]

+1 on the bad electros. probably bring it back to life.

still hard to believe it would make your signal louder in bypass, even if using a buffered bypass system.

weird.

Well here's a schematic of the IC version, and it looks like the bypassed O/P is taken after the first op-amp stage, so that may explain the gain.



If it's an original pedal, it could be just something as simple as a dry/cold solder joint, I'd use an audio probe and try and determine where the volume drop happens.

[Gristlepig]

Sooo...

I reflowed a bunch of the joints and redid the hack wiring of the tone bypass switch. A noticeable improvement; louder, though still not quite loud enough.
And the bypassed tone is still boosted. Oh, well... It works fine in a bypass looper.

[pinkjimiphoton]

cool!! did ya replace the electros?

looking at the schematic pyro posted, i can see where it would indeed be possible to boost in bypass...weird!!

but that said...maybe you can replace the 330k resistor with a 500k trimmer and dial it back a little on the first opamp stage?

could probably do the same on the second stage to get more baals out of it maybe.

or, like you said...just sell the damn thing, and keep the ones you built!

[Gristlepig]

I left the electros, cuz I'm leaning towards selling it. The couple of clones I built off guitarpcb.com boards sound better to my ears anyways.

The reflow helped quite a bit though. The pedal has noticeably more body and character now.

[Mark Hammer]

I fixed one of these last fall and believe me it ISN'T supposed to behave like that.

By "bypassed", do you mean the tone bypassed or the pedal bypassed?

[Gristlepig]

Sorry, I should have been more clear. I was referring to the bypassed (clean) tone.

Mark, can you perhaps let me know what was going on with the pedal you repaired?

If indeed, this pedal is in need of repar, the ebay seller is going to be hearing from me.

[pinkjimiphoton]

it's probably them caps, bro.

caps drift...either up or down.  either way can throw the whole circuit out of whack, and quite possibly result in more gain.

i had a big muff pi deluxe...the one in the trapezoidal box, with the muff ciruit and a compressor. that thing was all kindsa messed up.

somewhere, it sits in a friend's basement in a box of forgotten shit... i hope to get it back one day and restore it.

if you have the caps on hand, i'd change 'em out, and see if the problem goes away.

resistors (carbon comp) can drift too, and may explain the gain changes. as i recall, it should be at unity when bypassed.
but then, i never looked inside this particular model.

[Gristlepig]

Yeah, I'm just a bit leery of swapping out the electros and diminishing it's vintage value... That said it's value is already diminished by it's tone issues, so...

I emailed Howard Davis to get his take on the situation... and the seller as well...

So after I hear from Howard, I'll decide whether to swap out those caps. And if I do that I suppose I'll just throw a Carling DPDT in there and true bypass it as well...

Hopefully the seller will be amenable to a partial refund. When an item is billed as "Works great, sounds amazing" I don't expect to have to be poking around in there with the soldering iron. I've since had to resolder the replacement switch (dodgy solder job) and replace the batt snap, which was hanging on by a thread...

I initially thought I got this unit for a good price... now I'm feeling kinda burned.

[pinkjimiphoton]

swapping out the electros won't diminish the value, it should increase it. "vintage" doesn't apply to caps bro.
sounds amazing is subjective, and IMHO holding the seller responsible for dodgy soldering done by EH back in the day really isn't fair...
especially after this thing is so old now.
the seller most likely has zero knowledge of electronics. if they put their guitar thru and got fuzz, that was probably enough for them to say "it sounds amazing".
we're not "normal" people, guys like us.
i'm sure howard will be more than willing to look at it and take your bread, but imho (and not to deny him his living) it's kinda overkill.
it won't make a fuzz worth more because an original eh designer worked on it. it's still what it is,
and you obviously are capable of replacing the couple electros in it. ymmv, but to me, if ya really wanna waste your money...
send it to me, i taught roger mayer how to mod stuff for hendrix, and for only 300 bux, i'll restore your fuzz with the original vintage parts.

just kidding there, of course... but i hope ya see where i'm going with this.

if you don't wanna mess with it, let it go. if you wanna keep it, fix it. if you don't want some jerk like me to buy it on ebay and leave ya bad feedback, fix it THEN sell it.

but i believe IMHO you're kinda wasting time, money, and resources to send it out to do what you are most likely perfectly capable of doing yourself.

it's not like howard is gonna use 40 year old capacitors. he's gonna use fresh ones, just like we all would. ancient caps even if never used are likely to be bad, and need to be "formed" if you intend to use them.

by all means do what ya want... don't listen to me. but if it were me, i'd just fix the thing and be done with it bro. but again, imho, asking for a partial refund unless stated to be pristine is just bad karma.
peace.

[Gristlepig]

Good points... I guess I'll just swap out the electros and order up a couple of Carling DPDT's from Smallbear.

As for the dodgy soldering, I didn't fully elaborate... The slider switch was replaced at some point, and the solder job was a hot mess. The leads were burnt to shit, like the person doing the soldering was having a seizure. Melty burn marks from the iron all over the insulation for at least an inch or so from the connection. The connections themselves were huge gobs of dark grey cold looking solder. Easy enough to fix as the leads were plenty long... It just sucks to buy a pedal billed as 100% awesome, only to have it on the bench within minutes of plugging it in.
I should have asked the seller to provide less blurry photos of the guts...

As for the seller, he alluded to having experience with vintage muffs, claiming this one sounded great... And it sure doesn't... It sounded okay until I put it next to my clone build and then, wow... hella flat. I'm not giving him a hard time though... I've let him know what's up and he seems cool and cooperative

As for Howard, since he's the designer of the circuit, I was kinda looking for his definitive answer as to what I'm experiencing with this unit. Whether it's normal or not... I've read elsewhere folks having similar problems and it was attributed to the design of the bypass... I've also read loads of conflicting opinions regarding replacing electros in older pedals

I agree with you though... It is kinda silly to have him do work I could easily perform myself. And I believe I've got a bunch of current Illinois Capacitor electros that look very similar to the old ones.
Can't get to it now though, I'm all set up and ready to take the plunge and etch my first board tonight!!! Colorsound One Knob Fuzz...  Let's see if I can't get from Press n Peel to a completed pedal before midnight!

[pinkjimiphoton]

diggit!!
good luck with the fuzz...the colorsound stuff is a lot of fun.

so...i didn't realize the guy claimed to know about muffs. if he's on ebay, it's a gamble.

i've seen EH boxes like that right from the factory, especially back in the 70's. their QC was pretty horrible.

but it does sound like the guy monkeyed with it...so...lock and load.

howard is cool as hell, so i'm sure he'll help you and advise. i contacted him a few years (hell, more than a few) back about building me a clone theory..
he told me EH was reissuing them soon, so i waited, and bought one.

the reissue was GARBAGE. my bunghole still hurts from that one. noize to the point of being utterly worthless, and didn't sound or react anything like the original.

so...anyways...i bet if you replace the electros, you're fuzz will improve a lot. if not...sell the damn thing, be done with it. there's an arse for every seat, they say!!

[Mark Hammer]

Sorry, I should have been more clear. I was referring to the bypassed (clean) tone.

Mark, can you perhaps let me know what was going on with the pedal you repaired?

If indeed, this pedal is in need of repar, the ebay seller is going to be hearing from me.

The one I fixed had some wires with free ends. Nothing that might constitute aregular problem with that pedal.  When I fixed it, we agreed to omit the attenuation of the tone bypass, such that it could be set for very mild clipping yet still push an amp hard.  The owner likes it.