Seek Wah - question for Zachary Vex

[Ge_Whiz]

Mr Vex, I was just reading a review of the Seek Wah in a guitar mag, and now I clearly understand what it's doing! One question - the mag discusses its use as an arpeggiator, and it occurred to me to ask, is the filter a low pass, or a band pass? If the latter, relatively sharp or broad?

Just out of curiosity...

[bobbletrox]

So it's like an arpeggiator circuit controlling a VCF?

[zachary vex]

yes, it's basically a sequencer controlling a vcf.  the vcf consists of a vactrol connected to a twin-t wah-wah filter, which is a bandpass filter.  

http://zvex.com/seek-wah%20excerpt.mp3

[Arno van der Heijden]

How does the working principle differ from a sample and hold effect?

[Yuan Han]

I think the effect of sample and hold (from moose's website, mastro sample and hold) sounds similar to the seekwah.

VCF with an sequencer would set different wahs at different position and then play and cycle through them.

Sample and Hold would take a sample at the particular point (might be some related frequency to what is being played), and play it out.

I'm not sure if i'm correct, but this is what i *think*.

On another note, RG's article about the sequencer thing is pretty informative, and Mastro S&H seems like a great build.. really great sounding from Moose's website....

Han

[bobbletrox]

http://www.geofex.com/Article_Folders/udrand.htm

That looks like the ticket.  Hook it up to a tremolo and you'd get something like the new Seek-Trem.  Hook it up to Circuit Snippet's PWM and you'll have an effect unlike any other -it'd be a pretty small part count effect too since it'd basically be 5 ICs and a bunch of pots.  The Seek-Pulse Width Modulator!

[zachary vex]

How does the working principle differ from a sample and hold effect?

a random sample-and-hold-controlled-filter will not repeat, because every voltage sampled is an unpredictable value.  a sequencer will always repeat the same pattern.

[maximee]

bobbletrox: yes, amazing, isn't it?

i am going to seperate the sequencer and stick it in a small hammond enclosure with a 1/4" jack to connect to other pedals...from now on i'm gonna build my pedals with a "out to sequencer" jack...
man, i can't wait for the ICs to arrive...

or imagine multiple sequencers synced to the same clock...  

[bobbletrox]

That's a great idea!

The thing that stumped me when I was thinking about it was how to scale the output of the sequencer to other pedals.

[Elektrojänis]

or imagine multiple sequencers synced to the same clock...  

Try that with two sequencers controlling two twin T filtters (audiopaths in parallel). I think some sequenced wovels could be made.

[maximee]

Elektrojänis:

I'll try some sequencer combinations next week when I have the ICs I need...I am so looking forward to it  

[The Tone God]

Check out the Vanishing Point at the site.

The Tone God's Domain

Some suggestions pointed out and others are mentioned at the end.

Andrew

[Ge_Whiz]

Thanks, Zachary (and others).

[Mark Hammer]

Q for ZV

Many of the analog sequencers and sequencer projects/circuits I've seen over the years had a variable smoothing control to "de-stairstep" the repeating voltage-pattern.  I will admit to not being intimately familiar with the Seek-wah or Ooh-wah, but to the best of my knowledge they do not incorporate any such control (at least not one you can access from the outside).

The omission of such a control might be simply something as mundane as "no room", but my past experience with you suggests that would be interpreted as a challenge rather than an obstacle ( :lol: ).  This naturally leads to my next question, which is whether you found any sort of CV-smoothing to be of practical use in your circuit, or whether the use of a given Vactrol on the receiving end of the CV made a smoothing control less useful than one would initially think for the length, duration, and range of filter changes the pedals produce.  

I suppose it is worth noting that stand-alone sequencers NEED to have some sort of adjustable smoothing, if only in anticipation of the unexpected.  Such sequencers could be used to generate very slow changes over long periods of time and could be used to control not only filters but oscillators audio and LFO), VCAs, etc.  It is entirely reasonable that such smoothing means diddley squat when applied to a filter intended to cover the range of voice-like formants for a target instrument over a relatively brief pattern duration.

[R.G.]

You are, as usual, quite correct, Mark. Variable smoothing is a critical feature. Especially in something like a vocal tract filter - wink, wink, nudge, nudge.

[mikeb]

This is a very flexible lag / smoothing arrangement for CVs....


Mike