Chorus circuit gain

[DylanMac]

Hi, i was wondering if it is possible to mod this circuit so it has more gain. I think it can be done by adjusting one of the buffers? I don't want much more gain but i have it on the breadboard and it's just very slightly below unity.

thanks

[antonis]

Hi & Welcome..

Although I never had any volume issue with Jenny Greenteeth (greetins to Merlin..)..

[DylanMac]

great, thanks very much. what is the 470 capacitor there for?

[antonis]

great, thanks very much. what is the 470 capacitor there for?

It forms a Low Pass filter with 22k feedback resistor of about 15kHz corner frequency..
(you can omit it if you like but I shouldn't suggest it..)

[Radical CJ]

If only a small increase in volume is required, wouldn't it be easiest to increase the value of the 100k on the output? Say to 500k or 1M.

This would lower the cutoff frequency of the high pass filter made by the 100k and last decoupling capacitor (10uf), but this filter is already set very low (0.15Hz), so doesn't have an audible eq function.

Or perhaps reduce the value of the two 10k resistors feeding into the + input of U1B to 1K?

(Disclaimer: I'm not an EE with heaps of sage advice to impart, these just strike me as the easiest things to try first as they don't involve adding extra components. Others here may explain why these solutions are not ideal)   

[antonis]

wouldn't it be easiest to increase the value of the 100k on the output? Say to 500k or 1M.

That should result into no audible difference..
100R/100k -> 99.90   100R/500k -> 99.98 (0.007dB)   100R/1M -> 99.99 (0.008dB)

[Radical CJ]

wouldn't it be easiest to increase the value of the 100k on the output? Say to 500k or 1M.

That should result into no audible difference..
100R/100k -> 99.90   100R/500k -> 99.98 (0.007dB)   100R/1M -> 99.99 (0.008dB)

Described that way, I can immediately see why it wouldn't make an audible difference.  haha

[PRR]

A simpler argument suggests that a 10K+10K mixer is no different from a 1K+1K mixer (both into an infinite impedance amplifier).

The plan as drawn has gain near 0.98. DylanMac asserts this is "very slightly below unity"; true, but that implies incredibly good ears.

My observation over the years: if you put a thing in a chain, and it does not give gain, musicians say it is "below unity". Maybe really other degradations are at work here? Anyway, IMHO you may as well build 1dB gain in any flavor box, just so it does not sound "less". 

[ElectricDruid]

The plan as drawn has gain near 0.98. DylanMac asserts this is "very slightly below unity"; true, but that implies incredibly good ears.

My observation over the years: if you put a thing in a chain, and it does not give gain, musicians say it is "below unity". Maybe really other degradations are at work here? Anyway, IMHO you may as well build 1dB gain in any flavor box, just so it does not sound "less". 

In summary: "Loud is good"

[antonis]

Easier to add 2 X (+) signs rather than copy and rotate 90^o an electro cap symbol..

[PRR]

Yes.

[anotherjim]

If the OP is measuring the amplitude rather than AB listening against bypass, then they may be worrying about nothing.

If anything, a chorus that mixes wet & dry equally should sound a little louder than unity simply because it's adding 2 signals together that are of similar magnitude. If those signals happened to be identical copies (they won't be due to the delay), then it's x2 boost.

The wet/dry switch has a disadvantage in that it mutes the dry without boosting the wet, so loses the doubling effect.