Author Topic: Foxx Tone Machine unity gain problem  (Read 1571 times)

deaconque

Foxx Tone Machine unity gain problem
« on: May 19, 2008, 11:17:56 PM »
I built up a Foxx Tone Machine using the layout at GGG but after I got everything together and working I noticed that even with the volume pot maxxed, I was just a little below unity gain. It also seems like I'm getting a little less fuzz than a stock model has.  The only substitution I made from GGG was that I used all 2N5089's and 1n34a's in it.  I've checked this thing 100 times already, the soldering is fine, everything's in the right place and the right value and I'm stuck.  Please help.  I love the sound of this pedal it's just not loud enough.

petemoore

Re: Foxx Tone Machine unity gain problem
« Reply #1 on: May 20, 2008, 01:37:48 AM »
I love the sound of this pedal it's just not loud enough.
  I've read this line and lived it.
  And so I'm inclined to suggest putting a boost stage after the loved sound to get the volume up instead of figureing out why there isn't boost available [there should be boost].
 
 
 
Convention creates following, following creates convention.

Solidhex

Re: Foxx Tone Machine unity gain problem
« Reply #2 on: May 20, 2008, 01:50:29 AM »
Yo

  Yeah I've built 2 FTM's and both are very wimpy in both output and gain. Voltages good, components and wiring correct, many different transistors tried out and scrutinized for orientation.

--Brad

gigimarga

Re: Foxx Tone Machine unity gain problem
« Reply #3 on: May 20, 2008, 02:25:04 AM »
I used BC548C and silicium diodes for clipping (i had only 2 germanium diode) and it sounds enough loud, i think (i have no ideea if it reaches the unity gain or not).

deaconque

Re: Foxx Tone Machine unity gain problem
« Reply #4 on: May 20, 2008, 02:47:53 AM »
That's not quite the answer I was hoping for guys   :icon_wink:.  oh well, i guess I'll do some experimenting and see if i can figure anything out.  i'll post what i find.

Processaurus

Re: Foxx Tone Machine unity gain problem
« Reply #5 on: May 20, 2008, 03:06:10 AM »
My FTM has ample gain, meaning ridiculous amounts, I wonder what the deal is with low gain builds.  Silicon clipping diodes will cut less volume, that will help.  LEDs would cut even less.  Both will be less distorted (sustain-ey).  To keep the ungodly amount of distortion, either modding the output stage, changing the tonestack to a different type that doesn't cut as much volume, or brute force, adding a fixed gain stage to the end (MXR microamp would be good) would be necessary.  It's interesting that the foxx tone machine has such low volume, even though it has a transistor gain recovery tacked on the end, a la the BMP.  It would be nice to mod that for more gain.  I don't know if it would make it clip in that stage in a yucky way, but at the last transistor stage you could add another 1.5K resistor to the emitter, and the other end to a 4.7uF electrolytic cap to ground, to double the gain of that stage.  Smaller resistor for more gain than that.  The resistor + electrolytic in parallel with the existing 1.5K (R24) gives more gain to ac signals but keeps the DC gain were it is (~6.6 from the looks of it?).

The little plastic Danelectro french toast is a FTM clone, but with Si clipping diodes, and it is great, plenty of fuzz and a little more output.

deaconque

Re: Foxx Tone Machine unity gain problem
« Reply #6 on: May 20, 2008, 03:34:55 AM »
i might break down and switch out the 1n34a's i have in there.  i suspect that they're a big part of the problem.  that mod to the last stage sounds like a great idea i'm gonna try it out and see how it sounds.

Mark Hammer

Re: Foxx Tone Machine unity gain problem
« Reply #7 on: May 20, 2008, 07:57:09 AM »
My two FTMs have GE diodes and lots of output.  Not like any of Joe Davisson's high-gain monsters, mind you, but leagues above a Distortion+ or a Tube Screamer.

alex frias

Re: Foxx Tone Machine unity gain problem
« Reply #8 on: May 20, 2008, 12:20:09 PM »
I built several FoxxTone's using, 2N222, 2N5088, BC238 and 2N3904. I've tested Ge diodes, Si diodes and LED's for clipping.  Each one sounded more or less distorted, but everyone offers lots of level even when used in conjuction with the "experience" swell circuit after ithem.
Pagan and happy!

bmsiddall

Re: Foxx Tone Machine unity gain problem
« Reply #9 on: March 07, 2018, 03:49:15 AM »
Hi all.

Sorry to resurrect this thread, but I might have another angle to this.

Have recently built an FTM. I have 2 amps (hiwatt and deluxe reverb clones from Barwatt here in Australia). Through the hiwatt, there is plenty of gain above unity. With the DR Iím constantly cranking volume to max to try and match other fuzz I have in the chain. Even fully cranked itís not as loud. Seems very amp dependent. One caveat, I play at bedroom volumes and the DR goes through an attenuator (volume set to 4). Master volume on the hiwatt adjusted accordingly.

Have been lurking for some time but Iíve learned plenty. Hope to return the favour.

Cheers,
Brett

antonis

Re: Foxx Tone Machine unity gain problem
« Reply #10 on: March 07, 2018, 07:15:53 AM »
Wellcome Brett...!!  :icon_biggrin:

Just for info: Has your DR amp a dual input (Hi - Low)..??
Can't follow your signature changes, Stephen..!!

Kennt82

Re: Foxx Tone Machine unity gain problem
« Reply #11 on: March 07, 2018, 02:22:18 PM »
I doubled up on the clipping diodes (or tried silicon). I did the same for my Fender Blender which was under unity. The main octave fuzz  character was still there for both.  ( oops, old thread!)