Anderton's $3 passive fuzz?

[hodad]

A friend just gave me a copy of a 1967 Craig Anderton article for a fuzz that's basically just a diode & a cap placed between the amp's output tranny & the speaker.  Looks too easy not to build, but I figured I'd ask here if anyone's messed with it, & also if you risk damage to the output tranny by putting this thing between it & the speaker load.

Thanks
Tom

[ExpAnonColin]

A friend just gave me a copy of a 1967 Craig Anderton article for a fuzz that's basically just a diode & a cap placed between the amp's output tranny & the speaker.  Looks too easy not to build, but I figured I'd ask here if anyone's messed with it, & also if you risk damage to the output tranny by putting this thing between it & the speaker load.

Thanks
Tom

Well, if you've ever put a diode in your signal unamplified... then you'll know your very low volt guitar signal can't drive it at all, it just crackles... so it seems like anderton is taking advantage of your amp and just putting a diode in there which could be driven by the amp...  not a bad idea, but it's not passive-you need the amp to be on!  

-Colin

[Peter Snowberg]

That configuration would require the diode to eat what could amount to a LOT of signal. Better use a stud packaged rectifier with a heat sink. A 50W amp with 1N400x diodes might be able to double for stage pyrotechnics.

I used to have a 300 Electronic Circuits type of book from the mid 60s that had a circuit called "98 cent fuzz". It was just a pair of back to back diodes and a 10K pot in series. I think placement in the amp was just in front of the phase inverter.

-Peter

[Mark Hammer]

The "Black Ice" passive distortion unit that Stewart-MacDonald and other places sell works on a similar principle.  These are all essentially passive diode clippers.

Of course, the trick is identifying the sort of clipping diodes suitable to both the intended use and input conditions, since diodes and their combinations vary in terms of clipping thresholds, and the input signal always needs to be supraa-threshold to result in clipping.  

In the case of the Black Ice, it is a passive device intended to be installed in a guitar, so it needs to have diodes with a low enough clipping threshold that mere humbuckers could provide enough signal to result in clipping.  In the case of diodes placed at the output of an amp, we're not only talking about diodes that will see a much higher signal, but diodes that are expected to resut in an audible sound at the speaker  too.  Similarly, a diode pair at a preamp stage within an amplifier is expected to clip at a very different threshold than the Schottky diodes in the Black Ice.

The difference between these passive circuits and the more conventional active device is that diode-clipper fuzz boxes have an on-board gain stage or two to bring the signal up to the level that results in the desired degree/proportion of clipping.  With less gain, the signal will rarely be supra-threshold, and even then only for initial peaks.  With more gain, the input signal ends up being above the clipping threshold more and more of the time, until eventually (assuming enough gain and a hot enough guitar signal) the only time the signal is *not* above clipping threshold is when you aren't playing.

What this means is that passive circuits are going to be hit and miss since the match between input signal level and diode parameters may be less than perfect, and not variable across a wide-enough range to provide more than one flavour of distortion.

[Ansil]

so what would be a good diode to use for the black ice, i was wondering about that when i saw the thing on stewmac.

[Nasse]

When I started playing gtr about 30 years ago we fiddled with germanium small signal diodes directly across guitar´s output jack. You sure can hear it, I think one diode was easier noticed than two parallel at opposite directions. Of course with cheapo and weak pickups and ultralight strings (.007 at top E) you could not hear just nothing.  My Fender had powerful pickups enough to hear it (I worked at building site all summer long and bought an used Strato). But havent tried since. I thought it was not enough good to bother to add a switch to your guitar or box it.

[brett]

Perhaps the best way to go with this is simple, active electronics (single fet booster, 2 small photographic "button" batteries like the A76/AR44/G13) and low voltage diodes (Germanium or Schottky).  Then it could be mounted on a guitar cable or in the guitar or in a very small box.