Scaling LFO in Electric Mistress?

Started by Mr. Lime, August 06, 2018, 06:37:48 AM

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Mr. Lime

Hi folks!

I'm currently working on an Electric Mistress flanger and plan to add an expression pedal input on the Range control which is a 100kB pot.
As there aren't many 100k expression pedals on the market and most other circuits work with a 10k pot, I was thinking about scaling the LFO down by a factor of 10.
What's not exactly clear to me is which parts apart from the LFO itself have to be scaled down as well?

Is there anything else to consider? Did I miss something?

Thanks in advance!

Thanks for help

DrAlx

You don't need to change that many values.  Just do R19,R20,R21,R27 + the range pot.

Mark Hammer

Just make the expression pedal control the brightness of an LED.  Doubtless the LDR can be a value noticeably higher than the stock 100K Range pot, so placing the LDR in parallel with the pot won't impact the Range setting much if there is no illumination of the LED, and the Range control will behave as normal.  Use of the expression pedal would require that Range be set to maximum resistance, and the expression pedal simply reduces the resistance from that point.

Pick the right LDR and the right LED to suit the exression pedal, and you're good to go.

Mr. Lime

Thanks for the answers!

Well I think I'd be better to scale for a 10k range pot as there is so little place in the enclosure that an additional LDR would hardly fit. I'd like to use a switched input jack to exchange the pot if the pedal is plugged in.
I have one to two other pedals that could benefit from a 10k expression pedal.

Anyway thanks again for the suggested parts to change!  :)

No idea why this isn't a standard mod for the Electric Mistress?
It's super simple and makes such a cool effect..
Thanks for help

Mr. Lime

#4
There's one more question before I start building my clone;

John Hollis had posted his Ultra Flanger Design with a positive and negative feedback switch (even/odd).
I would like to know if it's reasonable to use an on-off-on switch that gives no feedback at all in center position.

I read somewhere that this would basically turn a flanger into a chorus.
What's to expect really by doing this? Seems similar to a EX Clone Theory Chorus to me..


Thanks for help

Fender3D

Switching off feedback is not the same as switching off dry signal (that's what Clone Theory's switch does...)

search for EM1022 here around,
you'll find clips and tips
"NOT FLAMMABLE" is not a challenge

Mark Hammer

Quote from: Mr. Lime on August 08, 2018, 11:47:09 AM
Thanks for the answers!

Well I think I'd be better to scale for a 10k range pot as there is so little place in the enclosure that an additional LDR would hardly fit. I'd like to use a switched input jack to exchange the pot if the pedal is plugged in.
I have one to two other pedals that could benefit from a 10k expression pedal.

Anyway thanks again for the suggested parts to change!  :)

No idea why this isn't a standard mod for the Electric Mistress?
It's super simple and makes such a cool effect..
I won't say how I know, but there is a product in development that will do exactly that. (And it's not me.)

Zwachi

Quote from: Fender3D on August 10, 2018, 10:04:30 AM
Switching off feedback is not the same as switching off dry signal (that's what Clone Theory's switch does...)

search for EM1022 here around,
you'll find clips and tips

Thanks, the EM1022 project looks and sounds great!
Without feedback the flanger comes a chorus pretty close.

I have found the Ultraflange & Chorus schematic as well which has some additional ideas but nothing necessary to me..
Thanks for help!

Mr. Lime

Quote from: Mark Hammer on August 06, 2018, 09:57:20 PM
Just make the expression pedal control the brightness of an LED.  Doubtless the LDR can be a value noticeably higher than the stock 100K Range pot, so placing the LDR in parallel with the pot won't impact the Range setting much if there is no illumination of the LED, and the Range control will behave as normal.  Use of the expression pedal would require that Range be set to maximum resistance, and the expression pedal simply reduces the resistance from that point.

Pick the right LDR and the right LED to suit the exression pedal, and you're good to go.

Is there a big advantage in noise/ticking to expect?
Thanks for help