Author Topic: Build report - ROG EA trem with alternate MOSFET amplifier stage  (Read 1543 times)

Threefish

Just finished a Runoffgroove-improved EA trem. I initially built it as per the ROG schematic and perfboard from here: http://www.runoffgroove.com/eatremolo.html , but got a fair bit of distortion, enough for me to contact the runoffgroove guys for some help. Brian very kindly replied with an image of an alternative MOSFET amplifier stage schematic designed by Gez :
http://putfile.com/pic.php?pic=5/14304484054.png&s=f5, and mentioned in this thread :
http://www.diystompboxes.com/smfforum/index.php?topic=27160.0
In the alternative schematic Gez has a couple of different cap values, but I used the same values as in the ROG schem. I might do some tweaking but Iím very happy with the sound I have. To modify the circuit from what Iíd already done I cut the connection where the 1M resistor+0.1uF input cap pair go to the MOSFET gate, and replaced that 1M resistor between the MOSFET gate and the 100k trimpot with the 1M pot (lug 1 to the 100k trim/47uF cap, lug 2 to the MOSFET gate, lug 3 to the 0.1uf input cap). I removed the 100k volume pot, with the output now going straight out with a 100k resistor to ground off it, using the ground connection that was there for lug 1 of the volume pot. Itís a bit tricky if youíve already done the standard setup, but do-able. Brian at ROG has given his permission for me to post my roughly modified pic of the perfboard with this mod :
http://putfile.com/pic.php?pic=5/14304451832.gif&s=f5
And I now have a distortion-free trem. I got bypass-level volume at about 11 oíclock on the input pot, and winding it on to about 3 oíclock I got a big boost but still didnít get any distortion

Thanks to Gez, Brian and the ROG team for the improvements on the original EA trem, and for the help in setting up the the alternative amplifier stage.


"Why can't I do it like that?"

John Lyons

Re: Build report - ROG EA trem with alternate MOSFET amplifier stage
« Reply #1 on: May 25, 2006, 01:33:49 PM »
Cool! I like when you get something with more than enough volume without distortion, especially a tremolo.
Good work
Any sound clips?

John
Basic Audio Pedals
www.basicaudio.net/

Threefish

Re: Build report - ROG EA trem with alternate MOSFET amplifier stage
« Reply #2 on: May 25, 2006, 08:31:25 PM »
I'll try to organise a sound clip - I really like the sound and I'm curious myself to hear what a recording sounds like.  It does sound similar to the ROG sample clips, and others I've heard of the EA trem - clear and smooth.
"Why can't I do it like that?"

Leetut

Re: Build report - ROG EA trem with alternate MOSFET amplifier stage
« Reply #3 on: May 19, 2019, 05:22:41 PM »
Links are dead, tried the fix from the description but get no sound, can you re-upload the schematic?

Edit: description works, Iíd removed the wrong resistor;)
« Last Edit: May 20, 2019, 08:38:15 AM by Leetut »