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Author Topic: FET crossfade / volume fade / pan  (Read 3874 times)

SineHacker

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FET crossfade / volume fade / pan
« on: June 28, 2012, 06:35:08 PM »

well I had some serious fun today

I had a play with some FET's today and I don't really know much about them, but through messing around I found this great way to volume fade / crossfade / pan. I was amazed at the simplicity of this, and it makes me feel like I have done something disgustingly wrong, or something that an engineer would spit on  :-\ You might know all this already but:



The FET's go down to perfect silence as far as I can tell, 10k seems like a good pot to use for mixing as I tried a 1k and everything was a lot quieter (thought the fade was very smooth) and a 100k pot cut signals in too hard. It makes a good volume fader if you just omit signal B and its FET from the diagram, and I'm sure it would be easy to implement it as a mono to stereo pan if you wanted (maybe with a 10k resistor between the signal input and the 2n3819). I'm not sure if the 10k resistors are needed before the output but I put them in just to be safe.

now I had some real fun today, I don't know if you have tried this but if you use small signal diodes to mix oscillators from something like a cmos 40106 then you get a cool unison effect between them, and this can be really interesting if you use oscillators running at super low or high frequencies - I was using the diodes after the 2n3819 pair to mix oscillators in and out (doesn't work if you place them before), it sounds freakin amazing! the unison effect creeps in really gently. I have basically sat mesmerised for quite some time this afternoon just fading between 2 oscillators  ;D ;D ;D

I have only tried this mixing with CMOS oscillators so far, but I presume it will work with other stuff as well, give it a go and I'll let you know if I find anything else if you like!

Aidan
« Last Edit: June 28, 2012, 07:41:01 PM by SineHacker »
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nochtanseenspecht

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Re: FET crossfade / volume fade / pan
« Reply #1 on: June 28, 2012, 06:55:11 PM »

hey that looks smart, thanks!
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SineHacker

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Re: FET crossfade / volume fade / pan
« Reply #2 on: June 28, 2012, 07:03:07 PM »

cheers! I have had to take a break because my brain was getting a bit overwhelmed with thoughts of possible applications  :D like I said, it has only been tested with cmos oscillators so far and I'm a bit baffled by how simple it is.

I use a home made matrix mixer in my live set which is horrible but an indispensable bit of kit. It's basically a passive matrix with a preamp section for the inputs, while it does the job, it's noisey as hell and some loud signals don't cut out even with the volume knobs turned right down. I have built two and they both took ages because of the amount of wiring, and the thought of making another one just seems a bit hardcore! but then if I could have a 6 x 4 matrix with every volume pot affecting a transistor for a smooth fade down to perfect silence... mmmmmmmm  :D this is my mixer btw: http://soundofginko.com/matrix-mixer-2-finished/
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SineHacker

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Re: FET crossfade / volume fade / pan
« Reply #3 on: June 28, 2012, 07:29:04 PM »

I just realised I made a blunder, with the post, the pot is actually linked to GND, is messed it up because I was trying to work with a +9v signal in the first place which was making it do weird things

*edit* - I updated the schematic in the OP *edit*
« Last Edit: June 28, 2012, 07:41:48 PM by SineHacker »
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SineHacker

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Re: FET crossfade / volume fade / pan
« Reply #4 on: June 28, 2012, 08:58:24 PM »

Well I was bored so I tried running some other signals as inputs and it doesn't work well at all, I guess maybe with a preamp circuit included it might be good - might try this tomorrow

if anyone is interested, this is what I was doing that I thought sounded so good:

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