Monday, 1 January 2018

Vox Distortion Booster V8161

First layout of the new year!! Figured we'd start off right with another classic fuzz. The original Vox Distortion Booster is a Fuzz Face variant unlike the reissue, which there's a layout posted. The Vox Distortion Booster V8161 is stupid rare, so no video clips, but being a Fuzz Face variant I'm sure we all have an idea of how it will sound. The Distortion Booster V8161 was made to be plugged directly into your guitar, similar to other effects of the time period.


  1. This is my kind of pedal - one knob! Can I assume that a 2N2904 will work here? Thanks

  2. Built. I made 3 changes to reflect the schematic by Phillip Bryant:

    (1) The first 330pf capacitor should run from the collector of Q1 to the collector of Q2 and not to the base of Q2 as shown on the strip board (move the leg from row I to row H).
    (2) The 10nf capacitor shown running from the emitter of Q2 to ground should be a non polar 10uf.
    (3) The capacitor between the 220R resistor and ground should also be a non polar 10uf rather than the 10nf shown.

    Even having made these changes and trying a range of transistors (2N3904, MPSA42, 2N2222, 2N2369, BC107, BC108 etc…) and combinations of transistors in varying hFe values and Q1:Q2 hFe ratios the effect was very disappointing.

    I have checked that my components are all are within specification. Perhaps the published schematic is incorrect, or I have somehow missed other strip board errors, or just possibly the original was equally poor?

    Sorry I do not have any digital recording equipment, so no samples.

    I found the ‘volume’ control to not so much to control the volume, but rather the extent and nature of the distortion. Most of the single pot control range is in my opinion pretty unusable because of either low/no volume, significant loss of higher frequencies, ’spitting’, or early break up/loss of the note. There is just a very small pot range where an indifferent ‘Fuzz Face’ alike effect is possible, but without further volume control.

    1. could you try using a 500k linear instead of 50k log? i might actually build this to see if i get the same results.

      did some googling and i found this: which doesn't seem to be the same pedal, but this looks similar

    2. man that looks like spam but i promise it's not

    3. I think your first clip is of a later (1970s?) Vox Distortion Booster and the second clip the Vox Treble Booster. I could not find a video clip of the V8161, but I did find a song sample of a 'modded' V8161:

      Yes, I tried all different input volume levels on this build last week in an attempt to get a reasonable sound and it did oscillate on zero guitar volume.

      Thanks for the suggestion on the pot. I will try changing the pot for a higher value when I get a chance (may have to be Monday now - no soldering allowed at weekends!).

      But note that the small usable range on the A50K was only near the physical centre position with a resultant volume at or just below unity. Going less than this on the pot giving first little or no distortion then little or no volume, going much above 1/2 way producing first spitting then complete beak up. I would not describe it as a volume control.

      BTW... The voltages with a typical Fuzz Face set of transistors (2N2369 hFe 80 and BC108A hFe 140) were pretty much what you would want on a Fuzz Face, save possibly for the Q2 collector, which was 10% high:

      Q1 C 1.6V B 0.7V E 0.0V
      Q2 C 4.9V B 1.6V E 0.9V.

    4. Sorry 'song' sample should have read 'sound' sample.

  3. I tried a B250K (no spare B500K pots at present). For me it was a significant improvement with both higher volume available and a finer control. Even the zero guitar volume oscillation was somehow less unpleasant.

    I guess that I should now go back and listen to Lou Reed on the VU's White Light White Heat and see if this anywhere near.

    I have ordered some Nichicon 10uf non polar caps to replace the cheap Chinese ones I have currently on my board. After they arrive and I have made that change, than I will call it a day on this effect.

    1. No, as I suspected, the Nichicon Muse 10uf NP caps made little or no audible difference.

      In conclusion, it works, but in my opinion it is not the greatest one knob fuzz.

  4. Yeah, unfortunately with a very rare pedal like this, and no gut shots, you have to completely rely on somebody's ability to trace a circuit (which is generally extremely poor). I have no doubt many of these component values are completely wrong, which is why nobody has achieved good results. If you want a one knob fuzz, build a Fuzz Face with the fuzz pot replaced with a 1K resistor instead.