How to improve the "inductorless wah" from a Zvex Ooh Wah?

[gigimarga]

Hi all,

I've built a couple of months ago a clone of Zvex Ooh Wah using a project from "another site".
As you know, the filter part is a Colorsound Inductorless Wah: http://analogguru.an.ohost.de/193/schematics/Colorsound_WahWah-RI.gif.

In the project that I've built there are 2 little differences: R10 is 470K (instead of 47K), R3 is 2.7M (instead of 3.3M) and R8 is 330K (instead of 33K).
I used a VTL5C10 which has the lowest value around 150-180 ohms. In the project is indicated a VTL5C3 which has a lower minimum in the datasheets (around 5 ohms!), but I had only a VTL5C10 and there are very expensive.

The sequencer and the random generator works OK, but the effect isn't so strong as I want.
I replaced R8 with a 33K, after that with a 50K trimpot and I got some changes (even some oscillations), but not what I wanted.

Another thing that it seems strange to me is that with all the pots (including the speed) at maximum I can't hear any sound (an older clone of Seek Wah sounded as a tremolo with all the pots maximized).

So my questions are:

1. How to make this filter to sound stronger (something like the filters of the EHX Bassballs)?
2. It is possible to switch some caps and to be able to use it for bass guitar, too?

Thx a lot and best regards!

[frequencycentral]

The ROG Phozer uses a similar twin-t filters to the Colorsound, albeit opamp onstead of transistor, but the Phozer puts two filters in parallel, tuned slightly differently for a thicker effect. I think you could do the same - build a second filter and parallel it with the first, tweak the values of the additional filter to have a slightly different response to the first.

http://runoffgroove.com/phozer.html

[gigimarga]

The ROG Phozer uses a similar twin-t filters to the Colorsound, albeit opamp onstead of transistor, but the Phozer puts two filters in parallel, tuned slightly differently for a thicker effect. I think you could do the same - build a second filter and parallel it with the first, tweak the values of the additional filter to have a slightly different response to the first.

http://runoffgroove.com/phozer.html

Thx frequencycentral, but it's hard for me to add an opamp (or I must to parallel the second filter with the first directly?).
My greatest desire it's to make a combination of an EHX Bassballs or of a Maestro FSH with this sequencer...

[fuzzo]

the inductorless is weak for me too. I made a wah probe pedal and I think, adding a boost after the output of the filter could be a good thing (zvex did that on his pedals).

Otherwise, I've two of them (I hoped use one like a fixed wah but I didn't 'cause the weakness of the effect) , you can change the 100Kpot for a 25K (and even less) to have a good range. But I'm not really convainced by that circuit.

the anderton anti-wah/wah or even the Dr. Q filter section (ehx) sound better.   

You can easily change the wah circuit by another one, juste use a LRD for controlling the movement.

[bean]

Hmm, actually that gives me an idea to adapt the project to fit in a Crybaby shell. Why not just go with a the real deal? The rocker could be set up to control the filter range or the speed with a switch. Actually, maybe it could be adapted to serve as a normal wah and a sequenced one. I need to think on that a bit. I have a Wah design already so I'll check into making some kind of hybrid out the two.

[gigimarga]

Thx a lot all for your ideas!

I have a Gargletron which I don't use, too...but I think I need a double vactrol for it (it was disscused in another thread).

[soggybag]

I built one of these inductorless wahs and had similar results. The effect was weak. I own a Seek Wah, which supposedly has the same type of wah, and the effect seems stronger. So it could be a problem with implementation. The suggestion to add a buffer is a good one this could help. Looking at the schematic it seems the effect might be improved by a adding a buffer on the input as well.

[earthtonesaudio]

Use an op-amp.


Alternatively, if you miss the single-transistor distortion, buffer the transistor's collector, and take the feedback from the op-amp, as well as the output signal.  The only caveat is the op-amp must be able to make the same voltage swing as the transistor (which may be very close to the rails).

[gigimarga]

I built one of these inductorless wahs and had similar results. The effect was weak. I own a Seek Wah, which supposedly has the same type of wah, and the effect seems stronger. So it could be a problem with implementation. The suggestion to add a buffer is a good one this could help. Looking at the schematic it seems the effect might be improved by a adding a buffer on the input as well.

Thx a lot soggybag!
I assume that the problem is from the VTL5C10 that I used. Can you post some voltages and the maximum resistance of the vactrol?

[gigimarga]

Use an op-amp.


Alternatively, if you miss the single-transistor distortion, buffer the transistor's collector, and take the feedback from the op-amp, as well as the output signal.  The only caveat is the op-amp must be able to make the same voltage swing as the transistor (which may be very close to the rails).

Thx a lot earthtonesaudio, but I will try first to improve it as it is

[soggybag]

I built one of these inductorless wahs and had similar results. The effect was weak. I own a Seek Wah, which supposedly has the same type of wah, and the effect seems stronger. So it could be a problem with implementation. The suggestion to add a buffer is a good one this could help. Looking at the schematic it seems the effect might be improved by a adding a buffer on the input as well.

Thx a lot soggybag!
I assume that the problem is from the VTL5C10 that I used. Can you post some voltages and the maximum resistance of the vactrol?

I'm using a VTLC9, but it's very similar to the VTLC10. Take a look at the datasheet: http://www.datasheetcatalog.com/datasheets_pdf/V/T/L/5/VTL5C10.shtml

[mountainking]

If you want to allow more low end to come through the circuit get rid of R9 and C7, together they attenuate low frequencies. Doing this will also increase the output level so you may want to make R10 a pot wired as a volume control/voltage divider.

Alan

[frequencycentral]

The ROG Phozer uses a similar twin-t filters to the Colorsound, albeit opamp onstead of transistor, but the Phozer puts two filters in parallel, tuned slightly differently for a thicker effect. I think you could do the same - build a second filter and parallel it with the first, tweak the values of the additional filter to have a slightly different response to the first.

http://runoffgroove.com/phozer.html

Thx frequencycentral, but it's hard for me to add an opamp (or I must to parallel the second filter with the first directly?).
My greatest desire it's to make a combination of an EHX Bassballs or of a Maestro FSH with this sequencer...

Yeah, I meant for you to duplicate the wah circuit using a transistor, parallel it with your original transistor wah circuit, and tune the two filters apart slightly. As ROG did with the Phozer. Quote from ROG: "Inspired by the Electro-Harmonix Bassballs, we chose two parallel filters tuned to different ranges. This results in a thicker and more convincing effect."

[soggybag]

I just tested my wah circuit out. I took out R9 and C7 and this did make things a little louder.

I compared it to the sound of my Seek Wah and I found the Seek Wah to have a more resonant tone. Especially in the higher frequency. I opened the Seek Wah to take a look at the values. The parts are really small, not surface mount, just 1/8 watt resistors and very small ceramic caps, so the values are hard to read.

[gigimarga]

.............................................
I'm using a VTLC9, but it's very similar to the VTLC10. Take a look at the datasheet: http://www.datasheetcatalog.com/datasheets_pdf/V/T/L/5/VTL5C10.shtml

Thx a lot soggybag!
I've looked at the datasheets and the mainly differences seems to be at the response times (VTL5C9/VTL5C10):
1. Turn-on to 63% Final RON (Typ.):  4 ms / 1 ms
2. Turn-off (Decay) to 100k (Max.): 50 ms / 1.5 s

As you can see, it's a big difference between them at the decay, but I have no ideea if this is the source of my problem.

[gigimarga]

..........................................................................
Yeah, I meant for you to duplicate the wah circuit using a transistor, parallel it with your original transistor wah circuit, and tune the two filters apart slightly. As ROG did with the Phozer. Quote from ROG: "Inspired by the Electro-Harmonix Bassballs, we chose two parallel filters tuned to different ranges. This results in a thicker and more convincing effect."

Thx a lot frequencycentral!
It's possible to control the filters from a Bassballs (modded with blend, attack, decay and pots instead of the trimmers) using the LFO and the randomness part from Ooh Wah?

[gigimarga]

If you want to allow more low end to come through the circuit get rid of R9 and C7, together they attenuate low frequencies. Doing this will also increase the output level so you may want to make R10 a pot wired as a volume control/voltage divider.

Alan

Thx Alan very much!
I will try to remove them tonight. By the way, what are R9 and C7 for?

[fuzzo]

The ROG Phozer uses a similar twin-t filters to the Colorsound, albeit opamp onstead of transistor, but the Phozer puts two filters in parallel, tuned slightly differently for a thicker effect. I think you could do the same - build a second filter and parallel it with the first, tweak the values of the additional filter to have a slightly different response to the first.

http://runoffgroove.com/phozer.html

I didn't understand that circuit, that's a "phaser" (or something like) or a auto -wah control by LFO ? the title"phozer" seems corresponds to a "phaser" ,  but the two filters showed suppose a wah filter 

[B Tremblay]

I didn't understand that circuit, that's a "phaser" (or something like) or a auto -wah control by LFO ? the title"phozer" seems corresponds to a "phaser" ,  but the two filters showed suppose a wah filter 

The Phozer name is based on the circuit being a "faux phaser" that provides sounds similar to a phase shifter while actually being a twin-T filter with LFO.

[fuzzo]

Ok thanks for the explanation ! I'd try that soon !

(just a last question, I understood  the LFO but what's the role of the  transistor ? )