Fet Phaser Idea

[mac]

I started a new thread with the BJT version,

http://www.diystompboxes.com/smfforum/index.php?topic=69002.0

It uses a 10mm yellow bright LED. It shares almost the same topology as the FET version.
BJT --> 4M7 form B to C
FET --> 1M from G to Gnd.

I still have to test and draw the new FET version.

mac

[mac]

I replaced fets, a mix control like in a P90, and used a single led to control the ldrs.



As you can see, different Vgs fets have very different bias voltages. Both mpf102 and 2sk246 sound good, better IMHO than the bjt version.

mac

[mac]

New sound sample at:

http://guitarfxs.tripod.com/index.html

I used a RM and a FF (not at the same time) before the phaser.  I had to supress CRT noise so you may hear some strange things in the high content.
First 3 takes fet v.3, the rest bjt version.
Home recording at low volume, sorry.

mac

[frequencycentral]

Really only just got into this thread, but now I am thinking of using it as a jump-off point for a tube phaser - replace the Fets with tubes - maybe change a few resistor values. Hmm!

http://www.diystompboxes.com/smfforum/index.php?topic=69437.0

I recently experimented with fets for a phaser. I guess that fets could easily be replaced in my design with low voltage tubes since tubes and fets share almost the same topology. I do not know what tubes can add to the sound, but worth the try.

mac

[mac]

I do not know much about biasing a tube, but if voltage is over 200V I'd start with 100k. IIRC My Laney has a tube with 2 x 100k resistors at 300V.
It'd be interesting to compare both if the tube experiment is similar.

mac

[frequencycentral]

I do not know much about biasing a tube, but if voltage is over 200V I'd start with 100k. IIRC My Laney has a tube with 2 x 100k resistors at 300V.
It'd be interesting to compare both if the tube experiment is similar.

mac

I'm planning to run at low voltage - 9 or 12 volts. I'm not really into frying myself with high voltages. If it doesn't work at low voltages I won't bother!

[bioroids]

I found it makes a notable difference in the sweep, when using the 1 led/4 ldrs setup, if you glue the ldrs to the led with transparent glue (like UNIPOX).
I guess the light must be diffracted, or something like that, and it gets more evenly distributed to the LDRs.

Greetings!

Miguel

[Morocotopo]

Bioroids, aclaracion para argentinos, unipox sería POXIPOL TRANSPARENTE?

[bioroids]

Ja, yo lo compre como UNIPOX, lo conseguis en cualquier ferreteria. Lo fabrican los mismos de Poxipol.

Ahh, la globalizacion... 

Saludos

[Morocotopo]

Globalizacion? Que globalizacion?



Saludos