hmmm...remember kustom amps?

[pinkjimiphoton]

i have always absolutely loved the shimmery phasey vibratto (not so much the tremolo) on the old tuck n roll kustoms of the chanute days..

so my question...anyone ever try and build just the trem/vibe circuit from one of these things?

i'd love to see it if anyone has..

[Mark Hammer]

I used to play a tuck-n-roll behemoth that belonged to our bass player back in the day.  Didn't have any modulation effects, though.

I was reading in an interview with John Fogerty a couple years ago that he was trying to get someone to reproduce that trem/vibrato combination for him in a pedal (he played and endorsed Kustom amps in the CCR days).  Don't know what came of that.

[R.G.]

How hard can it be? 

(yeah, I know...  )

Find me a schematic.

[digi2t]

How about this (lower right quadrant, Captain);



For the John Fogarty fans, the K-200 schematic;

[pinkjimiphoton]

aye, that's the beast!!! what do ya think?
RG you will achieve beyond godlyke status bro...

all we need to do is update it with regular, available modern components, make it run on 9v, and fit it in a box!!

way, WAY above my paygrade!!

[digi2t]

Hmmm.... looking at the 150 model 2 schematic, if you hack out the reverb section, I wonder if the rest would work with a 9vdc bipolar supply?

[pinkjimiphoton]

the kustom 150 is indeed the one to go for. the trem/vibe on them is sublime, a lot like the old fender pro phasey kinda sound...sorta kinda.

i bet it could be done..... on vero. of course.

[R.G.]

I was just about to type in "so which one is the good one?".

The 150 is a bit tougher. I think the magic is sealed up in those dual-gate MOSFET devices. That may be tough to find.

Just to be clear, the 150 has only "Trem/vib" not two different effects, right?

The 200 has a single phase stage about equal to one of the stages in a Univibe, but with overall feedback to sharpen it up a bit. Still thinking about what the 150 does.

[pinkjimiphoton]

they sound (to me, anyways) fairly similar... the 200 (or the one in the kustom II's, the "non plexi" ones) is slightly better sounding imho,
but the 150 is the real classic one.
yes, more of a trem. the one i jones for most is the phasey sounding one.

either way, i'd be grateful, RG.

if memory serves, the discreet components ones sounded better... the ic versions had a tendency to "crackle" a bit if you pushed them sometimes.

[Gordo]

Not to be a downer here, but I seem to recall Kustom's sounding a little like geese farts when they broke up. 

I guess that's not the subject here but I found it interesting that Fogerty sounds basically the same playing a PRS and a Bogner as he did playing a Rick and a Kustom.

We now continue with our regularly scheduled thread....

[digi2t]

Just snagged ten NOS RCA 40481 dual gate mosfets.

As for the IC's, a 4558 or 1458 might be suitable replacement for the 5558. For the 80848, I found this tidbit;

"The 5558 look pin compatible with easy to get RC1458 ; the 80848 look like an early version of CA3080, being pin compatible with LM741 but having an extra pin 5 gain control; the 739 will have to be replaced, as Enzo said, with a "dead bug " mounted RC4558 or similar, with thin wire joining compatible pins and God help you with 40841 dual gate Mos Fets, if you happen to need them."

So... LM741 for the other IC?

[pinkjimiphoton]

dino, you kill me.

[digi2t]

I just had a revelation.

I was thinking about this last night, when I realized that my Ampeg tremolo circuit uses a metal can CA3080. Probably the same deal here. What I find kinda neat is the reverb circuit has a tone control along side the intensity. First time I`ve ever seen a tone control on the reverb.

I`m really tempted to breadboard this, without the reverb section, although it might lose a lot of mojo without the reverb. I`m wondering if it would be better to box it a la Fender reverb unit style? Once I get the Infinitphase off the bench, I`ll break out the breadboard. I have 4558`s and 3080`s in stock.

[Mark Hammer]

You know, usually, I can look at a schematic and think "Oh, THAT's what they did there.  Clever."   The 150, I look at it and my continuing response is "What the hell IS that?".

If those 80848 chips are CA3080s, or some comparable OTA in disguise, what in the heck are they doing in a reverb circuit, and why does it take three of them?  Cripes, I think the only part that makes any sense to me at all is the footswitch and the send/receive jacks for the reverb pan.

[R.G.]

You know, usually, I can look at a schematic and think "Oh, THAT's what they did there.  Clever."   The 150, I look at it and my continuing response is "What the hell IS that?".

That's my reaction too. What were they THINKING? Every time I have looked at Kustom schemos over the years, that comes up.

However, eventually, if you dig into it, you go ...um, OK, they're using this to do that; weird...

If those 80848 chips are CA3080s, or some comparable OTA in disguise, what in the heck are they doing in a reverb circuit, and why does it take three of them?  Cripes, I think the only part that makes any sense to me at all is the footswitch and the send/receive jacks for the reverb pan.

I can guess at that one. Some designers like to drive reverb tanks with a current source, not a voltage source. OTAs are naturally voltage-in/current-out devices, so it's possible they grabbed the then-high-tech ICs and used them in native mode. Likewise, dual-gate MOSFETs are GREAT for gain control. One gate does signal in, the other does gain control directly in the MOSFET channel. It's much like a solid-state pentode where one grid is signal input and the other (the screen grid) is gain control. They were highly prized - and priced! - in the day. They're also fragile and quirky.

[teemuk]

I think the magic is sealed up in those dual-gate MOSFET devices.

Prolly not as they are just switches to enable/disable tremolo oscilllator output.

If those 80848 chips are CA3080s, or some comparable OTA in disguise, what in the heck are they doing in a reverb circuit, and why does it take three of them?

The circuit is actually Vibrato-Tremolo-Reverb.

The reverb uses plain OpAmp driver and a NPN transistor -based recovery stage.

Tremolo is achieved with pretty simple OTA gain modulation.

Vibrato is the trickiest circuit of the three. I assume it's pretty much the basic all-pass filtering setup with two OTA's configured as variable resistors.

I was thinking about this last night, when I realized that my Ampeg tremolo circuit uses a metal can CA3080.

Yes, that they do. The cool part - that was probably unintentional in Ampeg amps - is that when you overdrive those stages they have nice soft overdrive.

[pinkjimiphoton]

teemuk.... exactly. they DO have a nice soft overdrive. the phasey nature of the vibe in these is the shiznit.

i love the balance control between trem and vibe. that's the part that brings it to life.

reverb tone control? funny, i don't remember there being one on any of the kustoms i had...and i've had a bunch over the years!!

actually, my kustoms didn't have fuzz, either. very weird. i have seen the ones with fuzz built in, tho.

[teemuk]

[teemuk]

reverb tone control? funny, i don't remember there being one on any of the kustoms i had...and i've had a bunch over the years!!

[pinkjimiphoton]

ahh, a different model.....mine were mostly the plexi front ones. this is the later version, but this is the one with the real nice sounding vibe.

the ones i'm talking about there was reverb depth only, and you had a pot that panned between trem and vibe, a pot for speed, and a pot for intensity.

i had one of these ones, a gold sparkle (i think it was a 200 or 250 tho, i'll have to look and see if any pics survive) but it was "crackly" so i asked the guy i got it from
to get it fixed. the owner of the repair shop died, never saw it again. might have played it three times. if that. actually... i do have a pic of it..



unfortunately this happened a year or two before i got into building boxes. i can do tube amps, but never messed with solid state until fairly recently.