Ring Modulator Passive or Active?

[Harry]

Will they work /well?/ with guitar passively?

[zachary vex]

usually a guitar's output isn't high enough to drive a passive ring modulator.  you will probably have to use a buffer.  remember, a ring mod also requires some sort of carrier, which can be anything from a simple oscillator to a radio.

[Marcos - Munky]

Go with an active ring mod. The Maestro Ring Mod is a great one. Like Z said, a guitar signal isn't enough to drive a passive ring mod.

[Harry]

O.k. was thinking of using the AMZ's single JFET 3volt booster for each entry and exit boost. Would this be enough gain?

[brett]

Hi.
Re passive ring mod: Low Vf diodes (Ge or Schottky) have 0.3V of loss.  For losses to be small compared with the signal, you need at least 5V of signal (10V would be better).  A 9V booster and a cranked compressor can get you a reasonable signal level for a passive ring mod IMO.  However, all serious ringmod people seem to eventually use a multiplier (eg AD633 or MC1496).  The MC1496 is available from Small Bear for a very reasonable price.
cheers

[Harry]

Thank You

[Noplasticrobots]

I've got a question on passive ring modulators and I don't htink it justifies starting a new topic.

If all a passive ring mod needs is a buffer, then what's so hard about plugging in a Fetzer Valve at the beginning of the circuit and calling it done? I've seen so many people mention the impedance problem and it just seems like such a simple fix! What's the deal?

Also, how would you add in a carrier signal jack to those transformer/diode ring modulators?

[John Lyons]

Noplasticrobots

You have to "buffer" it as well as add a carrier. So all in all for a "simple" ring mod you need a Signal buffer/amplifier, The  ring mod circuit with Diodes, Transformer or IC and then the Carrier which is the signal that modulates the guitars signal.

I have built the Maestro and will have it really to post soon. It is a true ring modulator and sounds very nice. It's a bit hard to tune correctly without proper tools like an oscilloscope but it is not impossible.

John

[Cliff Schecht]

Later today, I'll have a schematic and perfboard layout for a simple buffered ring modulator using a 4558 for both the carrier and input. I'll get some sound clips up soon also.

[Noplasticrobots]

I understand the basic workings of the circuit, I guess what I'm trying to ask is why do so many people not build the passive ring mod if all it needs is a buffer and a carrier? I understand if you need a ring mod in a live situation on a pedal board and don't want to have extra cables and some sort of noise making carrier. I have more of a "studio interest" in ring mods and don't mind the extra cables. Plus it seems like it would produce more interesting sounds if you added a carrier. It just seem slike people go "Oh, I need to build a buffer? Forget it!" Does it come down to the passive ring mods being tonally inferior to the active ring mods? If that's the case then I can understand, otherwise what's so hard about building a buffer and adding a carrier jack? 

Cliff, please post that schematic, I'm definitely interested!

[John Lyons]

I think it comes down to people not knowing enough about it or possibly just wanting something more complete and not having to supply a separate carrier and buffer. I don't claim to know much about ring modulators or anything else for that matter, I just think that simple wins out and that adding circuit blocks to an already unknown device (for the beginer) is a big leap of faith. Then you take into account all the confusion over Ring mod devices that are not really ring modulators but circuits that have sound artifacts on chords and bent notes similar to a ring mod (green ringer, fender blender, ampeg scrambler etc etc. ) I may be way off?! 
John

[Noplasticrobots]

I can definitely see where you're coming from Basic. I'm definitely no expert on anything electronic, but after building a Green Ringer my interest in ring mods has soared and it just seems so simple to use only a handful of parts. To each his own I guess! I'll have to give the passive ring mod a shot one of these days.

[brett]

Hi
to use a passive ring modulator with a guitar signal require a lot more than a buffer.
Two other key ingredients include:
1a.  an input amplifier with sufficent gain to ensure that the minimum 0.3V drop across the diodes doesn't cause gating (ie elimination of small signals).  For 50dB dynamic range, the voltage gain needs to be at least 0.3 x 10^(50/20) = 316.  That is a boost for a 100mV guitar signal to 31.6 V.  Obviously, this is impossible with a 9V supply.  Allowing for a bit of headroom, a 100 V supply would be good. OR
1b.  transformers that give voltage gain.  I've used 8ohm:1K audio output transformers (voltage gain = 11) to boost the voltage in the diode ring.  However, the transformers need to be driven by a power amplifier capable of driving 8 ohms.  For high voltages, a high power amp will be needed.  I've used a little LM386-based amp with OK results.
2.  balanced transformers.  Even a small imbalance allows a lot of carrier through.  In my limited experience, commercial transformers aren't closely matched, and you'd probably need to wind your own to get a really good result.  While most people can learn this skill fairly easily, it is probably not an attractive option for busy people.

cheers

[Cliff Schecht]

brett: I was expecting a lot of problems when I went to design the ring modulator I'm using now, but a simple preamp before the buffer is all that is needed to bring the signal up to usable levels. I'm using EMG's on one of my main axes and the 85 outputs about 1.5v (sometimes more, but were talking single notes), so I just designed a simple buffer in front that has a gain of 4.7. I haven't tried smaller values, but I did set it at a gain of 47 with just as pleasant results. Using an oscillator as a carrier has its advantages, such as being able to tune the pitch with a knob and set it, but any effect with a wet and dry output can be used with very pleasing results, especially a pitch shifter. I will post soundclips as soon as I finish boxing up my little design.

[Cliff Schecht]

Schematic, perf layout and pics here: http://www.diystompboxes.com/smfforum/index.php?topic=47132.40 

[John Lyons]

Thanks for your work here cliff.  Glad you get right in there and made the thing!
I'm anxious to here a sound clip when you have the time.

John

[Noplasticrobots]

No perf layout loaded on that page you linked to, but that build looks simple enough.

What kind of instrument is a passive ring mod more suited to?

[John Lyons]

Noplasticrobots

Just check out the other ring mod thread by Cliff. There is a Perf layout there. Not asure how the link got fouled up.
john