"Ring Frobnicator" de-bugged and working !!

[MartyMart]

OK, "Almost" finished with my de-bugging projects, here's the "next to
last" one :

I built this from John Hollis's original schem, with NO substitutions, even
down to the TL062 opamp.
MPSA18 transistor though  !!
At first, I had no "ring" or "frob" going on and had read all the posts re
similar problems, mostly due to the LED's and the LED/1N4148 used.
A more recent post pointed to the forward current requirements and how
that had "solved" the problem.
I went back to this and used three 3mm red LED's from the same batch.
Also used a 20k trimpot from 9v to the pair of LED's/100uf cap to ground
to bias at approx 3.2volts, as per The schemo ( 3.42 )
The "beast" came to life !!
( previously I had three 5mm red LED's two of which were not the same
type/batch and no "bias" trim pot )

"Tremolo" - worth building just for this function, it's by far the most
smooth trem that I have built.
Great variance in depth and speed, noiseless and no "wierd" artifacts
As a tremolo circuit - 10/10  = perfect !!

"Ring modulation" -  this is not true "ring mod" as others have noted, if
the trim pot is set "just right" there is an area when the "constant tone"
is almost non-existant, it takes some "fine tuning" and seemed to be
working with both speed/depth pots at about 1/3rd rotation - approx !
You can then find some interesting tones/chimes and general "oddness"
which may be useful here and there.
as a ring mod circuit - 5/10

So use the same type of LED for all three and a trimpot may help also.

Fabulous Tremolo, which I think everyone would like A LOT !!!

Cheers,

Marty.

[MartyMart]

Bumpty - bump !

No one interested then ??     :cry:

Marty.

[Jaicen_solo]

Hey, I'm interested!!

Can you post soundclips of the Frob?? I built the ThingModulator, and I love the tone, but not the constant whine. If the frob is similar that might be a good place to start looking for a replacement. If you can't host them, can you mail soundclips? Quick and dirty is fine

*bob

[soggybag]

I have a frobnicator that I built and it worked for a while and then stopped. You have inspired me to get it working. Do you have an image of your fix?

What's a ThingModulator? I like the name. Is there a schematic on the internet?

[Jaicen_solo]

It's here:
http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html

Good man, get yous working and post some clips!!

[jmusser]

The Thing Modulator I hope will end up being a somewhat cleaner "Noise 567" circuit. I was trying to get the CMOS 567 from Mouser so I could get it with my order, but they wouldn't get in in special, so I'll have to go to Arrow and pay shipping again. I was really thrilled Marty that you solved the problem that's been plagueing this circuit since I've been reading about it on here. I knew it had to be something small, but finding that "small" thing, is the trick.

[MartyMart]

Yup, I was pleased to get that one right !
so, to sum up :

2X 3mm red LED
1X 3mm red LED (same batch) + 1X 1N4148
20k trim from 9v to the 3mm LED pair set for 3.2 - 3.4 volts across them
100k trim as per the schem
Done !!

Marty.

[soggybag]

If I understand what's going on, the V-bias is set by the two LEDs. Why not replace this with two resisters and a cap? Or is there something more going on here? It seems, from my novice view, that you could use the same set up as used in a Tube Screamer or other to set the V-bias.

[MartyMart]

If I understand what's going on, the V-bias is set by the two LEDs. Why not replace this with two resisters and a cap? Or is there something more going on here? It seems, from my novice view, that you could use the same set up as used in a Tube Screamer or other to set the V-bias.

.... not quite, the LED pair "looks" like a VB setup, but they "pulse" in
step with the rate control .... ?
So something more is going on here, which I'm not 100% sure of ... ?

Marty.

[soggybag]

I don't understand what is going on with LEDs either. I thought the V-bias was generated by the voltage drop across them?

[MartyMart]

I don't understand what is going on with LEDs either. I thought the V-bias was generated by the voltage drop across them?

Perhaps that's the "maximum" @ 3.2volts and then there is a voltage
swing down - back up to there ..  causing the pulsation in the LED's ?
Maybe someone else knows more here .....

Marty.

[soggybag]

I dug up the Frobnicator I had built a few years ago this morning. I tested it again and to my surprise it was working? The last time I had used it had stopped working and I couldn't get it to work. It had worked when I first built it.

I tested the voltage across the two LEDs and got 3.1 V. I tested it with several batteries. It worked with all of the batteries that tested less than 9V and wouldn't work with batteries that tested above 9V.

And the thing that boggles my mind is that with every battery I measured 3.1V across the two LEDs no matter what the voltage of the battery? I was expecting a change here that I could point to as tangible evidence of the problem.  

I really wish I understood what was going on here?

[soggybag]

bump

[jmusser]

I guess I'll find out what's going on here in a little bit, because I'm just about ready to start this beast on perf. I still have to look up the 3080 chip pin out, but other than that, and armed with Marty's notes, I'm ready to take a shot at it.

[Tuemmueh]

I built the RingFrob also, but have the problem that there is some LFO-noise all the time, even when I don't play.
In the RingMod-Mode the little "sirene" that was in the Tremolo-Background becomes a constante tone. When I turn the Freq.-Knob the tone changes it frequency (what a surprise ... )
I built up another Voltage divider for the LFO but had no success.
I just haven't tested your method, Marty, but I will do so in the next days, hoping it will fix my problem.

If anyone has got another idea, he's invited to post it here  

[MartyMart]

Remember, i didn't use any "layout" that's available for this, I made a new one on veroboard.
It's one of the few builds I've done, where I left a LOT of space so :
My input/output/9v and ground are about as far away from each other as possible.
Input left, output right, 9v at top of board some 12/14 strips away from
ground.
Perhaps this accidental "care" has led to a very quiet build.
My tremolo setting is very quiet and works a treat !
Ringmod does have the "constant tone" but its possible, by use of both
rate/depth control, to make it fairly quiet and "tune" it into a relevent
note.... A for instance, then play scales of A around it with great results !

Marty.

[Paul Marossy]

Good on you, mate!  :wink: