The Gyraf Magneto-Dynamic Infundibulum

[leigh]

Look, audio nerds, check it:

The Gyraf G21 Magneto-Dynamic Infundibulum is a stereo, multi-band saturator/clipper. Sounds kinda run-of-the-mill and boring, right. But wait...

1. It's completely passive. Not just Pultec "passive EQ" passive - it has NO active electronics or makeup gain stages, and hence no power plug.

2. The audio path for each of the two stereo channels consists of *a single transformer*. One side is the input, the other side is the output.

3. The controls affect a sidechain path, which in turn alters the audio signal by affecting a tertiary winding of that single transformer.

I just thought you should know how rad that is.

(The best writeup I've seen of this box is in the current issue of Sound on Sound. Here's the article, subscription needed to view though.)

http://gyraf.dk/g21/index.html

[Marlowe]

I just read the review in SOS yesterday. I found the idea fascinating. Now I want to hear what it sounds like!

[ubertar]

I'd like to know more about how this works. Seems like it could be simplified and adapted into a passive distortion pedal. Or is the clipping too subtle? I don't have an SOS subscription, so I couldn't read the rest of the article.

Does the transformer actually have three windings, or is one side center-tapped?

[leigh]

I just read the review in SOS yesterday. I found the idea fascinating. Now I want to hear what it sounds like!

On the SOS website they have some audio clips up. Haven't gotten to listen yet (they are all bundled together into a zip file, so not mobile-friendly), but here you go:

http://www.soundonsound.com/sos/sep13/a ... -media.htm

[leigh]

I'd like to know more about how this works. Seems like it could be simplified and adapted into a passive distortion pedal. Or is the clipping too subtle? I don't have an SOS subscription, so I couldn't read the rest of the article.

Does the transformer actually have three windings, or is one side center-tapped?

I'm curious to know more about how it works too! There are some technical details in the manual on the Gyraf website. They initially note there that the transformers are "without galvanic isolation", and later go on to say:

The clipping is done at the audio transformers - the clipping circuits just presents (in parallel) a complex impedance that loads the transformers magnetic field, resulting in various degrees of collapse in transformer flux - which in turn attenuates the passing-through audio.

So it sounds like it's not the case that one side of the transformer is center-tapped. The SOS article states it as "the clipping stages and bands are tapped via a tertiary winding on the transformers, meaning that the clipping circuits present an impedance to the transformers' magnetic fields". So, yeah, sounds like there's actually 3 windings.

As for a passive distortion pedal, you'd definitely need a boosting stage beforehand. The manual says that the input impedance can drop as low as a few hundred ohms, depending on settings. They also mention that you need to feed the G21 with a healthy signal from pro-audio hardware, and that driving it from consumer level hardware won't work so well.

[gyraf]

The first user comments are starting coming out:

http://www.gearslutz.com/board/high-end ... bulum.html

Jakob E.

[leigh]

The first user comments are starting coming out:

http://www.gearslutz.com/board/high-end ... bulum.html

Jakob E.

Congrats, Jakob! I continue to be fascinated with the signal flow concept you came up with.

The SOS review explains some of the technology in more depth than the user manual on your site. Did the writer interview you for that additional information, or was that just stuff they figured out on their own? They mentioned specifically how each clipping band runs a frequency-specific transmission line off that 3rd transformer winding.

cheers,
Leigh

[gyraf]

Thanks Leigh,

Actually, Hannes Bieger of SOS magazine managed to figure most of this out by himself - but asked us for confirmation before publishing.

I really respect that sort of in-depth work from a reviewer, when it comes to describe complex stuff like this.

And btw you're right - this type of circuit won't really work for a guitar pedal effect, at least not the way the G21 does it.

Jakob E.

[gyraf]

The full SOS review is now public:

http://www.soundonsound.com/sos/sep13/a ... af-g21.htm

Jakob E.

[gyraf]

Independent review by Bob Macc - one of the first-movers of G21:

http://bobmaccsblog.wordpress.com/2014/ ... um-review/

Jakob E.