Sunday, 2 January 2022

FAL Treble Boosters

 Found these posted by the one and only pinkjimiphoton on the usual places. Both are very old and rare always on fixed treble boosters. Should be quick fun small builds. You can easily make them NPN by flipping the electrolytic caps, power and ground connections. I believe low gain transistors will work fine in them.


FAL Treble Booster 1967



FAL Treble Booster 1969




9 comments:

  1. Yesssssss, I will try this! Thank you Rocket88!

    ReplyDelete
  2. What's up with the series input caps on the 69? Wouldn't a 4.7n or 5.6n work just as well?

    ReplyDelete
    Replies
    1. no reason you can't use those values, 10nF was in the schematic. If you go lower you will have less bass coming into the circuit.

      Delete
    2. Aren't 2x 10n in series = to 5n?

      Delete
    3. the schematic did have 2 10nF in series, so your calculations are correct.

      Delete
  3. * * * happy new year * * *

    ReplyDelete
  4. I had a question about the "flipping" from PNP to NPN technique by reversing the power and ground and the polarized parts. I know this works with a battery. I would like to make better use of my Ge PNP's an have been studying Fuzz Faces. I found a schematic of a Red Dunlop '99 Ge PNP powered with plus +9v. Am I off base in assuming this is not compatible with a +9v daisy chain power supply, only with a battery? I do have a large supply of 7660s' for Charge Pumps but always like to reduce costs, labor and part counts when possible. If the straight reversal is usable how does it compare to using a Charge Pump?

    ReplyDelete
  5. Also I have been studying Reverse polarity protection (which is probably more important in my PNP designs). Using a diode in series on the +9v input, a 1N34A Ge Schottky drops the voltage from 9.33v to 9.22 in normal flow. Reversed the power shows up as .02 volts. Is this enough to protect the circuit and what is an acceptable level of reverse leakage? And in a -9v scenario would the diode be inserted in series with the + ground or the -9v (and what orientation)? I am interested in a transistor as protection. I have seen a BJT PNP used, Emitter to +9v, Base to a current limiting resistor to ground (2.2k-3.3k?) and Collector to Vout. What PNP's would be usable? Also very interesting is an N-Channel power Mosfet used on the low side. Apparently you need to protect against V's greater than the Gate-Source breakdown voltage (Vgs). I know how to do this with a (9.1-10v) Zener and a current limiting resistor (10k-100k?). Is a BS170 (Vgs 20v) or another Mosfet up to the task by itself, without the Zener and resistor?

    ReplyDelete
  6. I see plenty of designs that use a "reversed" diode to ground as polarity protection. I realize that eliminates all voltage loss but will it really give you decent protection? Sorry about all the questions but my extensive online research seems to have left just shy of usable answers.

    ReplyDelete