Simple Voltage Volume Control Circuit?

[nguitar12]

I am designing a tremolo. I saw most of the design on the internet using optic couple to convert the voltage to resistor to limit the guitar signal.

Just wondering if there are any simple voltage control volume circuit out there so that we can skip the optic couple and make the build easier.

I am looking for a circuit that will attenuate the volume down to zero so that the depth of the tremolo will go wider. Will the following circuit work?



Thanks

[Kipper4]

Look how ean tremolo does it.

[nguitar12]

Look how ean tremolo does it.

I built EA Tremolo before. However this circuit is too subtle for me. It done by varying the source resistor to control the gain right?

Will this topology actually turn the volume complete to zero? I ask because I want a super choppy effect. What voltage range should I apply to gate of J201 if I want to replace the oscillator?

[antonis]

Let's make some definitions before proceed to any solution..

Vibrato is achieved by electronically emulating Doppler effect, like the pitch of a specific frequency sound source moving towards a lisener rises proportionally to the source's velocity...
In it's simple form, it uses all-pass filter(s) that alter/shift phase with no effect (or a little) on amplitude..
(pitch modulation - no distortion)

Tremolo is achieved by loudness change with usually involving distortion & altered frequency response and it uses various "mechanisms" like preamp bias modulation, final stage bias modulation, distorting or non- distorting divider, rythinc mixing (approaching vibrato), VCA e.t.c. 

Although, most people use the term "Tremolo" for both kind of effects, there are major differences in sound and circuit design...

With a simple Volume control (probably on output) you will not result in any of the above effects...

[bool]

Search for Schaller tremolo first.

You can use and adapt the EA tremolo phase-shift osc. to drive the control element (the simple BJT transistor) like in the Schaller trem.

Also search for Univox tremolo (that was built into some of their amps).

You will have to fine-tune the simple circuits a little bit; but it's a "walk in the park" compared to nightmares resulting from jfet parameter spreads ...

[PRR]

Circuit you posted may not give "ANY" gain change, depending what drives it.

You *need* some impedance (a resistor) between source and FET. The typical small JFET will go from infinity to some hundreds of ohms, so resistor needs to be K-Ohms. (22K is a fine trial.) And of course the source needs to drive that KOhms when gain is low, so a naked guitar wants a buffer.

After that: JFETs will distort then splat if signal is higher than a few-tenths Volt for certain gain conditions. They are not miracle audio controllers.

Photo-resistors are low distortion to couple-Volt levels and never splatt, but the lamp needs real power.

'3080 is a good-not-great audio controller but needs significant interfacing.

The THAT Corp VCA chips can be (with interfacing) truly wonderful audio controllers, but are "new" (post 1990) and complex; never seen a trem designed around one.

[Kipper4]

If you want choppy try this maybe.

http://www.diystompboxes.com/smfforum/index.php?topic=114965.msg1067541#msg1067541

[amptramp]

Check out the trick in Figure 6 and Figure 7 in this paper:

http://www.vishay.com/docs/70598/70598.pdf

for getting linear resistance change when using a JFET as an attenuator.

[nguitar12]

Let's make some definitions before proceed to any solution..

Vibrato is achieved by electronically emulating Doppler effect, like the pitch of a specific frequency sound source moving towards a lisener rises proportionally to the source's velocity...
In it's simple form, it uses all-pass filter(s) that alter/shift phase with no effect (or a little) on amplitude..
(pitch modulation - no distortion)

Tremolo is achieved by loudness change with usually involving distortion & altered frequency response and it uses various "mechanisms" like preamp bias modulation, final stage bias modulation, distorting or non- distorting divider, rythinc mixing (approaching vibrato), VCA e.t.c. 

Although, most people use the term "Tremolo" for both kind of effects, there are major differences in sound and circuit design...

With a simple Volume control (probably on output) you will not result in any of the above effects...

Yes I know what you are concerning about but what I mean by tremolo is exactly the volume change not the pitch change.

[nguitar12]

Check out the trick in Figure 6 and Figure 7 in this paper:

http://www.vishay.com/docs/70598/70598.pdf

for getting linear resistance change when using a JFET as an attenuator.

Thanks for your info. Is Figure 6. the solution to what PRR mentioning at #5 ?

[Groovenut]

Check out the trick in Figure 6 and Figure 7 in this paper:

http://www.vishay.com/docs/70598/70598.pdf

for getting linear resistance change when using a JFET as an attenuator.

Thanks for your info. Is Figure 6. the solution to what PRR mentioning at #5 ?

No, that would be in Figure 5. Paul was stating that you need some amount of source resistance for the FET to work against in order for signal attenuation to be attained.