Ring Stinger Photos

[HrD]

sorry for my beginner question...but there is something that i don't understand:

when i'm going to match diodes...i have to look for the same-nearest mV...
i make an example:

i have many diodes 1n34

and i found 4 diodes @ 263 mV

other 4 @ 248 mV

and other 4 @ 290 mV

the ? is: on matching..is important to find only the same mV ...or it's important also the mV?
...in the previous example,for the Ring Stinger ..if i found those mV values ....what diodes i have to put : 263mV, 248 mV or 290mV?
thx

[Gripp]

Well, my line of thinking about this was, in order of priority:

1) Get the diodes matched as close as possible in order to maximize carrier supression,
2) Get the voltage drops as low as possible in order to minimize diode losses

so if it were me, I'd go with the 248 mV set if they are as closely matched as the others.

Best!
Pelle G

[markusw]

What can I say, this has been a really fun day!

Seems you really had fun with this little PCB 

When running a computer generated carrier I got just a little bleedthrough at two frequencies, one was easy to dial out with the trimmer but the other not. The frequency that still was bleeding through was the same as the carrier frequency.

Maybe the xfmr trimmer also is'nt a perfect solution to compensate for not-perfectly matched xfmrs or diodes. So, probably it won't be possible to eliminate carrier breakthrough over the entire freq range. Any comments would be highly appreciated   

The IPS-33b, often refered to as the poor mans eventide, does +/- 2 octaves of "clean" pitch shifting, it has some character but that is one thing I like about it. It has no waveshaping functions at all but you just gave me an idea. There would be no problem running some fuzz (probably Tim Escobedos simple square wave shaper made simpler) on the pitch shifted carrier only, we'll see what that sounds like when that enclosure gets back from powder coating.

I'm pretty sure that this will give you a cool "intelligent-ring-mod" sound.

Well, my line of thinking about this was, in order of priority:

1) Get the diodes matched as close as possible in order to maximize carrier supression,
2) Get the voltage drops as low as possible in order to minimize diode losses

so if it were me, I'd go with the 248 mV set if they are as closely matched as the others.

Exactly my way of thinking.

Regards,

Markus

[Gripp]

Hi Markus!

I spent some time today tinkering with this thing, investigating the carrier breakthrough. First, it wasn't that loud yesterday either, clearly something I could live with.
Second,  I will really have to read some theory about how passive ring modulators work. I know the results and pitfalls but not the exact how

Do you know why Lovetone chose to put the carrier on the primary of the transformer? The way I've seen it in other schems (eg http://www.cgs.synth.net/modules/cgsrr.html) it has the carrier on the secondary. It shouldn't matter which is X or Y  should it? For impedance reasons only, because of the balancing of it or something else?

Ok, when testing with scope and signal generator (sine wave about 5V p2p), input grounded and signal injected to carrier only, the trimmer behaves in this way: It cancels out the carrier fundamental but leaves a frequency an octave up from the carrier and it shows on the scope (about 10mV p2p so not that much). The balance setting is however dependant on the amplitude of the carrier, when balanced with a 5V p2p carrier, it isn't balanced anymore when lowering the carrier amplitude to 2,5V p2p. The octave when balanced however stays about 10 mV p2p for a range of carrier amplitudes but increases when larger than 6-7V p2p and goes down at perhaps 1 V p2p.  I must have heard that octave yesterday. Adjusting the trimmer either way just make the fundamental more prominent.
So there must be some crosstalk or something, the carrier getting in to the input modulating itself maybe.
When grounding the carrier and injecting signal to input, there is more bleedthrough and the trimmer does nothing, as expected. The temperature sensitivity of germanium diodes was easily seen too, if one was picky, the trimmer would have to be set with changing ambient temp. The xfmr board wasn't shielded at any time.

And now for the difference between seeing something on the scope and listening to it.
It turns out that when I properly ground the input directly to ground of the board while injecting carrier and listening, it goes almost totally completely silent. "Normal" hum is louder. There must be grounding/crosstalk/noise issues with the listening setup because when I listen with my guitar connected to the input via booster and turn down the volume, the bleedthrough is louder then when it was properly grounded. This is what was heard yesterday. The action of the trimmer is also heard as was seen, ie adjusts fundamental to octave of the carrier and is the most silent with the fundamental supressed. I have to turn up quite loud to hear the bleedthrough, "normal" hum is about the same level. One time I thought that it was 50 Hz getting in modulating itself but it wasn't. It tracks the carrier freq an octave above perfectly.

Best!
Pelle G

[guitarhacknoise]

The temperature sensitivity of germanium diodes was easily seen too, if one was picky, the trimmer would have to be set with changing ambient temp. The xfmr board wasn't shielded at any time.

Pelle G

One thing I had noticed with my trials at the passive r.m. was in matching the diodes that just touching/handling the Ge diodes affects your readings. It seemed best to layout all the prospective diodes and let them "stabilize" before taking the measurements,WITHOUT HANDLING THEM measure them and write them all down then measure them again, and repeat, you could end up with three different readings for each diode!
Matching is a B....!
I think you would need to find the four with the lowest CONSISTENTLY matching voltage drop.

[Gripp]

Yup, that's what I did. I have some experience matching GE transistors prior to this so the same precations were taken when matching the diodes.
It was just interesting seeing the waveforms change at the touch of a finger.
Maybe a new control element lurking here 
Best!
Pelle G

[soggybag]

Could anyone give me a quick guide to matching ge diodes? Can they be matched by the reading from the diode tester on my DMM?

I have all of the parts me and a friend are planning to make a couple Ring Stingers. we're just getting started.

thanks

[guitarhacknoise]

Well, If you have a diode setting on your DMM and it uses the probes to take the measurement your in business!
if you have to plug the diode into a socket........well it'll take a while but I guess it would work.
With the GE's:
make sure the Dmm's probes are clean.
make sure the Diode leads are clean.
follow my description in previous post.
with black probe on the side of diode with black band,
Red probe on the otherside, you will get a reading of .xxxV,
if you do it with the red lead on the side with the black band the reading will be .000V
how's that?
-Matthias

[markusw]

Hi Pelle,

I know the results and pitfalls but not the exact how

Same for me 

Do you know why Lovetone chose to put the carrier on the primary of the transformer? The way I've seen it in other schems (eg http://www.cgs.synth.net/modules/cgsrr.html) it has the carrier on the secondary. It shouldn't matter which is X or Y  should it? For impedance reasons only, because of the balancing of it or something else?

Suppose for balancing.

Ok, when testing with scope and signal generator (sine wave about 5V p2p), input grounded and signal injected to carrier only, the trimmer behaves in this way: It cancels out the carrier fundamental but leaves a frequency an octave up from the carrier and it shows on the scope (about 10mV p2p so not that much). The balance setting is however dependant on the amplitude of the carrier, when balanced with a 5V p2p carrier, it isn't balanced anymore when lowering the carrier amplitude to 2,5V p2p. The octave when balanced however stays about 10 mV p2p for a range of carrier amplitudes but increases when larger than 6-7V p2p and goes down at perhaps 1 V p2p.  I must have heard that octave yesterday. Adjusting the trimmer either way just make the fundamental more prominent.

Interesting observations. I have to admit, I didn't analyse balancing that thoroughly.

It turns out that when I properly ground the input directly to ground of the board while injecting carrier and listening, it goes almost totally completely silent.

I had the same observation with the whole circuit. Don't know, but maybe using shielded wires for the input signal (between main PCB, switch and xfmr PCB) might help a bit. On the other hand breakthrough isn't that  dramatic (at least with my clone), so maybe I'll leave it as it is (hm, not really as it is, since I still have to add all the jacks and put it in a box ).

I have to turn up quite loud to hear the bleedthrough

Same with my clone (as already mentioned).

regards,

Markus

[soggybag]

I got my Ring Stinger etched and soldered, it've wired everything up and it's almost working. The LFO seems to work the Drive seems to be working.

There seems to be a problem with the VCO. I get no signal from the VCO out jack? I have looking around at IC 2 and everything looks correct. Here are the voltages at each pin of IC2(<edit should be IC 2), if anyone sees anything obviously wrong please point it out.

1 = 4.24
2 = 4.24
3 = 4.24
4 = 8.47
5 = 3.99
6 = 6.35
7 = 1.46
8 = 6.93
9 = 4.24
10 = 4.24
11 = 0
12 = 4.24
13 = .01
14 = 4.24

Any suggestions?

Edit: These are IC 2 I made a mistake.

[markusw]

Hi soggybag,

the posted values are from IC1? Were they measured in LFO-lock mode?

What voltages do you have at IC2. Would probably be more relevant since it includes the VCO.

Markus

[markusw]

Hi soggybag,

at a first glance pin 13 is way too low. Should be around V/2.

For my circuit with LFO locked and in octave mode (VCO not active!) with 12,22V PS

1 = 6,11V
2=  6,11V
3=  6,11V
4=  12,22V
5=  5,69V
6=  9,16V
7= 1,54V
8= 9,72V
9= 6,11V
10=6,11V
11= 0
12= 6,11V
13= 6,11V
14= 6,11V

Regards,

Markus

EDIT: so, from the voltages you've posted it looks like you might a: be in octave mode and b: might have a bug around IC2/4 (maybe a short from pin 13 to gnd?)

[toneless]

Brilliant work!  How much time did it take to reverse engineer it? 

Keep sharing...!

[soggybag]

Thanks Markusw, I'll have a look at pin 13 and everyhing connecting to it and see what I find.

[soggybag]

It appears that everything is working now. I'm not sure what the problem was. I think either something was loose or on of hte pots or jacks may have been shorting against something else. I'll have to take extra care when putting it inside the box.

I'm working with a friend. When he's finished we can compare the two.

Here's a photo.

[ovnifx]

Yeah, I'm that so-called "friend"  .  When we had the board just sitting on his worktable, we kept getting all kinds of intermittant odd issues, like LEDs lighting up at illogical times.  But then we popped it up into the stand, and separated the flying pots away from each other, and the problems disappeared one by one.  So as he says, probably some parts shorting against each other, or maybe some weak solder points.  We'll have a better idea when my board is all wired up and testable.

[markusw]

It appears that everything is working now. I'm not sure what the problem was. I think either something was loose or on of hte pots or jacks may have been shorting against something else. I'll have to take extra care when putting it inside the box.

I'm working with a friend. When he's finished we can compare the two.

Cool!  Congrats!

Looks pretty similar to mine (regarding all tose crocodile cables ) And I can compare it directly because mine isn't boxed yet (distracted by other projects )

Will you put it in one of your great etched boxes??

Brilliant work! How much time did it take to reverse engineer it?

Keep sharing...!

Don't remember exactly. The main part was done after about 3 weeks working mainly in the evening. The worst part was finding a tiny trace to gnd that I missed.  Without it biasing of the VCO was completely messed up. Took me ages to find it. But it was pretty cool when I added this trace to the Spice sim, because the VCO immediately worked as supposed. Anyway, it definitely was fun and I learned a lot, believe me. Before, I just played with distortion pedals and some envelope filters. So I did'nt have a clue on oscillators. It was especially nice to see the respective subcircuits starting to "work" in Spice thereby revealing their identity/function. Besides the simple opamp buffer and distortion circuits basically everything was new to me..

Maybe the ? Flanger next ?? I just fear that the this one is a completely different league...I don't have a real clue on flangers...


Markus

[soggybag]

The enclosure we are using is a bare sheet metal type with a sloped front. These are the closest we could find to the original in the Mouser catalog. The PCB for this project is so large there are not many boxes that will fit it. The Mouser catalog number is    537-MDC973-01.

As far decoration goes we're still debating whether silk screen might be best. There was an idea to make an etched brass face plate that might be bolted or riveted on the top...

[markusw]

Insert Quote
The enclosure we are using is a bare sheet metal type with a sloped front. These are the closest we could find to the original in the Mouser catalog. The PCB for this project is so large there are not many boxes that will fit it. The Mouser catalog number is    537-MDC973-01.

Should fit nicely. Do you have any datasheet that tells a little more than 9x7x3 inch??

As far decoration goes we're still debating whether silk screen might be best. There was an idea to make an etched brass face plate that might be bolted or riveted on the top...

I like the idea with the brass plate. Saw it somewhere in the net. Looked pretty cool! IIRC the plate was highly polished and somehow glued to the enclosure.
How much will you charge for the one with the brass plate, btw ?

It's really a pitty that the Lovetone enclosures are not available. Would be cool for other projects too!

Markus

[soggybag]

The Lovetone enclosures are very nice. It looks like the top is hinged for easy access. The paint looked good too.

I hadn't really thought about selling these, though I had been thinking about making a second. I got a few ideas from building the first that I'd like to try out.