Vocal ECF

[RaceDriver205]

Has anyone been to the boss website and heard their sounds samples.
Their new AW3 autowah has a vocal mode:
http://www.bosscorp.co.jp/products/en/AW-3/specs.html
Click on the demo button, and its the 3rd sample.

Does anyone know of any shematics/diy projects of vocal ECFs? (as in makes vowel sounds)

[Dave_B]

R.G. has some interesting stuff here, but I don't know if anyone has built one.   

[RaceDriver205]

Yeah, but thats for a wah pedal. I want a ECF so it does it for me!
Only DIY ECF ive heard make a 'vowel sound' is the funny cat, which moosapotamus modified to create a "woah woah" sound.
Also, that ya-ya pedal sounds uncanny!

[Mark Hammer]

The schematic for the Schaller/Kent Yoy-yoy has never really clicked in my head so I have no idea exactly what sort of filter it is, but I'm a big fan of it.

The "vocal" sounds that some pedals produce are essentially twin counterswept filters.  The current Line 6 Otto Filter has a "talking filter" mode that nicely illustrates this when used in stereo (you have to extricate it rom the mono dock it normally comes in and plug the module into a stereo dock to hear it).  There are two bandpass filters, one of a slightly lower range than the other.  As one sweeps upward, the other sweeps downward (flick the direction switch and they do the opposite but still sound kind of talk-ey).  Stereo isn't necessary for the effect but by turning one amp off at a time, you can hear the actions of the two separate filters.

Tim Escobedo's Gargler and Gargletron are nice simple attempts to do this.  I imagine the replacement of one of the 2N5088 transistors in the E-H Bass Balls with a control element that changes resistance in the opposite direction could make that circuit do the talking thing.

[RaceDriver205]

Interesting. Do you have this schematic for the 'Yoy-yoy'?

[Paul Perry (Frostwave)]

http://www.diystompboxes.com/pedals/schall.gif

[RaceDriver205]

Cheers, frost.

[Mark Hammer]

Paul,

Do you have any idea what the extra cap and inductor actually DO to make a yoy sound?

[puretube]

sorry - I`m not Paul.

the Yoy-setting adds a second (higher) resonant peak,
which sweeps up and down in parallel to the basic one.

When all other things are settled, Mark,
I`ll mail you a freq.-plot...

[Mark Hammer]

You are not Paul, but you are a scholar and a gentleman all the same.

Should one assume, then, that the second resonant peak can be moved around by means of that 22nf cap?  If so, that makes for a very interesting pedal.

[puretube]

probably...

I just see, that (of course) the inductors interact:
fres_max of the basic peak is being tuned down a little when the 2nd inductor gets parallelled.
This 2nd peak varies roughly in the 2-5kHz region,
while the basic peak goes from ~400-1500Hz @ "Wah-Wah",
and from ~300-750Hz @ "Yoy-Yoy"

(this info is from a book by the "german C.A.": "Helmuth Lemme" from `78)

[johngreene]

Actually the way I see it work is a little different.

First of all, the circuit show in the schematic in that link will not work as drawn.

The second inductor is in series with a 22nF capacitor, this forms a series trap at 1.5 kHz. This is right in the middle of the sweep range of the first inductor. Because it is series resonant at 1.5kHz, the 'variable' 4.7uF cap doesn't have much affect at all on the response of this part. This notch attenuates the input at 1.5 kHz but also eliminates the negative feedback, so the gain of the circuit is the highest at 1.5kHz. It also loads the first inductor lowering its Q. So, imagine a low-Q, tunable bandpass response with a big notch right in the middle of it. That's where the 2 peaks come from.

The output will always be a minimum at 1.5kHz. So there will be kind of a 'dead spot'.

--john

[puretube]

I only tried to describe the plotted gain/frequency graphs which the author has measured, from that book...

[EDIT]: the notch wanders from ~1.5 to 2kHz @ "Yoy-Yoy"

[johngreene]

Having never seen the book I could only describe what I see from the circuit/schematic. I didn't intent for my post to state anything negative about yours. I apologize if it appeared that way.

--john

[puretube]

hehe - I never analyzed the schemo...
those thingies sounded so thin, ~30 years ago,
that I threw out the innards of those 2 I had (gotten used ones for free),
for (ab-)using only the shell & pot...

I guess they where intended for "string-"keyboards, rather than "jazz-"guitar