Dano Chicken Salad Vibrato

[Dan N]

I did a down and dirty trace of this little guy. Could not get the values of the SMT caps, but figure the ones doing the vibrato will be the same values as in a univibe or easyvibe.

http://users.rio.com/senorris/junk/dcsv.gif

The top is very similar to John Hollis's Easyvibe, while the bulb driver is taken from the old Univibes.

If anyone has any thoughts on where to add a chorus/vibrato switch, I'd sure like to give it a try.

Dan

[Boofhead]

Good chance the Depth pot is should be grounded.

[Mark Hammer]

I'm reminded of the old Casiotone keyboards that would all use the same voice-generation-keyboard-scanning chip, but simply tap different available features of it, proclaim it a different model and charge another 70 bucks or something.

What you've drawn out is essentially a phaser with the phase/vibrato switch permanently in the vibrato position.  Take any standard 4-stage phase-shifter and lift/disable the connection between the dry signal coming off the first stage, and the point downstream where wet and dry are combined, and you'll get a vibrato effect.  Apparently, more phase-shift stages will yield more pitch-bending, but 4 seems to be about optimum.

The "chorus/vibrato" switch on the Univibe is, of course, mislabelled.  While one setting does provide vibrato, the other does NOT yield what anyone would call "chorus".  Of course, since it was well over 30 years ago that the Univibe was first made, before the advent of BBD chips that would eventually be used to produce time-based chorus effects, and since they had to call the other switch setting something, and since it did not sound at all like a phaser, it appears they called it chorus because that sounded about right.

In fact, the "chorus" setting on a Univibe is essentially a phase-shifter configuration, except that the staggered cap-values in a Univibe produce a  qualitatively different kind of notching effect when combined with a dry signal.

None of this is to reprimand either you or Danelectro.  Rather, it presents an opportunity: Run a 100k resistor between pin 1 of the first op-amp on the left (wherever it is on the board) and pin 5 of the op-amp over on the right, and you'll have yourself a phaser.  If you can find space in there for a SPST minitoggle that can enable/disable that connection, you'll have yourself a phaser/vibrato pedal.  I can't tell from your comments whether C113/112/116/107 are identical or staggered values.  Certainly you can get vibrato whether they are the same OR different.  However, if they are staggered values, you will get Univibing with the added resistor and connection, phasing if they identical values.

[Torchy]

Comparing with the EZvibe something like this ?
Or replace the spst with a 100k pot as a blend control ?
http://server6.uploadit.org/files/Torchy-chvibcs.jpg

[Mark Hammer]

Adjusting wet level makes sense to me, but I tend to see dry level as something you use in an all or nothing manner.  That's just me though.  What I usually recommend in such an instance is a combination of fixed and variable resistor for the wet path that permits one to go from (in theory) just a bit more wet than dry, to much less wet than dry.  That gives you the room to nail a flawless 50/50 mix for maximum notch depth in addition to scaling back the intensity of the effect.  Note that in the case of vibrato, "effect intensity" is determined by the sweep width, and NOT any wet/dry level adjustment.

[Torchy]

Thanks for the insight Mark (as usual  :wink: )
Ive built 3 EZvibes so far (stock), Ive now got one Im tinkering with and it does lose a lot of 'that' sound when I reduce the dry level ...

[Dan N]

Thanks very much Mark. How funny if we opened up a mini phaser only to find the same pcb!

Slightly off topic is this site where no casio keyboard is safe!
http://users.informatik.haw-hamburg.de/~windle_c/TableHooters/instruments.html

Thanks also Torchy!

Boofhead, you are right and I corrected the schematic.

I expect my pcb will find it's way into some kind of wild fuzz/vibrato like the psychodelic machine or something. Where'd I put that French Toast?!?

[Mark Hammer]

Great link!! Thanks.

[John G]

Dan,
I did the Vib/Phase sw mod a couple of weeks ago, and works well. R116 is the dry path mixing resistor, I lifted it off with two fine point soldering irons. R116 (100K std size) now gets attached to the sw.
The phase caps are per the origional.
Cheers
John G

[Dan N]

Dan,
I did the Vib/Phase sw mod a couple of weeks ago, and works well. R116 is the dry path mixing resistor, I lifted it off with two fine point soldering irons. R116 (100K std size) now gets attached to the sw.
The phase caps are per the origional.
Cheers
John G

Thanks John! I did just as you wrote and got the phaser sound!

Man, those surface mount resistors are hard for me to deal with. Switching back and forth between lupe and reading glasses!

By the way, I peeled open the light box, and there's a grain of wheat incandescent in there. I wonder if that is why these have a reputation as battery hogs?

Dan

[John G]

Dan,
I'm glad you have had success, I hope you wired the sw in series with R116, on reading my post again I could have caused confusion. I am working towards rehousing it in the squarish Hammond box. I will be adding an insulated stereo jack so I can use a remote foot pedal to change speed.  Maybe I will also put the Vib/Phase on a f/sw. I am also trying to figure out how to turn the first phase section into a Tremolo stage !!!! You are right the grain of wheat bulb is the current sucker. The first op- amp stage is a non inverting stage, I notice that you have it as inverting.
Cheers
John G

[Dan N]

Hi John,

Yea, I did wire the resistor correctly.

I did the trace from this:

http://users.rio.com/senorris/junk/dcsf2.gif

and am pretty sure the opamp pins are right.

About the tremelo. The Shin-ei RT-18 Reslytone had trem as as well as vibe and "chorus". Maybe the schematic can point you in the right direction?

http://www-public.rz.uni-duesseldorf.de/~pelz/schematics/SHIN-EI_RT-18.pdf

Thanks again,
Dan

[John G]

Dan,
Thanx for the info and the link.
Cheers,
John G

[brett]

Hi.  Mark H wrote

I can't tell from your comments whether C113/112/116/107 are identical or staggered values. Certainly you can get vibrato whether they are the same OR different. However, if they are staggered values, you will get Univibing with the added resistor and connection, phasing if they identical values.

What interested me the first time I saw them were the numbers used for the phasing stages in a univibe.  They seemed staggered in some sort of pattern of prime numbers, presumably so that there was no even spacing of notches.  Anybody considered this pattern and can offer ideas?  

If it's just a matter of replacing (staggered) some caps or resistors, and adding that 100k phaser resistor, it might be worth buying an old D chicken salad just for conversion to an almost univibe.  Yes?  No?

[puretube]

the staggered caps go back to the 1940`s, when a guy named Dome
(yes, the one of the Filter...)
patented a way of achieving SSB radio transmission...

in those old times, (esp. 50`s) the organ guys (Hammond, Wurlitzer, Leslie a.o.)
used to call those "half-phaser" kind of circuits "CHORUS" or "Celeste",
when it spun @ less than ~3Hz.

Later, BBD circuits took over the name for the similar effect.

[John G]

All,
The "Salad" is an op amp (surface mount) clone of the "Univibe", complete with staggered cap values, and lamp driven LDRs. It has the advantage over the origional in that it has a buffered input and bypass switching. Does it sound like the origional?? I don't know not ever having heard one. One thing about the Salad is that at high depth settings and at medium speeds there (to my ears anyway) seems to be a far amount of Amplitude modulation going on. My theory is that  the large 0.22mF phase cap is causing it, like shorting most of the signal out Maybe Mr Hammer or someome with greater knowledge could comment.
Cheers
John G

[travissk]

I have the mini phaser, unfortunately it's in storage. I can check if it is a similar circuit when I go back to school, but I've heard it's a Phase 45 or Phase 90 clone.

I think the French Toast Fuzz is a Foxx clone?

[brett]

So is there a "chicken salad" AND a "chicken salad vibrato" ??
And the former is a univibe clone?  Sorry for the dumbie questions, I wouldn't know a Danelectro pedal if I fell over one.

[b_rogers]

i have 2 chicken salad pedals, and one of them has a pretty good "univibish" sweep. the other doesnt quite have the wobble of the first. a little noisy and  sounds best with the middle?? pickup of my strat .. for 25 bucks its not bad..


Brent

[brett]

Is the univibe "work-alike" the "DJ 15 vibrato"??  I'm confused. :oops: