Noob question about biasing Ge transistors in Tone Bender

Started by phaseroll, September 20, 2010, 11:10:13 PM

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phaseroll



I recently received an order from Small Bear Electronics, which included a PNP transistor set for a 3-knob tone bender circuit.  The stock list mentions that these transistors are supplied with a test circuit showing the recommended resistor values.

Sorry to be a bit dense, but I want to make sure I understant this information correctly, and am hoping someone can advise (I did a number of searches - sorry if I missed something obvious).

The three transistors I received each came in an individually labeled plastic bag - the bag for Q1 identified the transistor as being a 2SB77.  The bag for Q2 had the value '70' written on it, while the bag for Q3 was marked with the value '106'.  The components were accompanied by a circuit diagram labeled "The Color Sound Three-Knob Tone Bender", which was the same as the schematic I was initially following from tonepad.com

I would be grateful if anyone could clarify the meaning of the values (70, 106) written by hand on the transistor bags - are these measured gain values?  or are they the recommended resistor values mentioned in the product description?  If they are resistor values, does this imply that I need to change some of the resistor values specified in the provided circuit diagram for the Tone Bender circuit, or add additional resistors to achieve the correct bias?

Thanks in advance for any guidance,

pr

smallbearelec

Hi--

They are measured gains. NB: When you have a specific question about things you receive from us, please write to smallbearelec@ix.netcom.com. We do respond, though sometimes not immediately. While the people on this board are an incredible volunteer "help desk," we do our best to handle as much of our own technical support and service as we can.

Regards
Steve Daniels

Solidhex

The "70" and "106" are the hfe gain of the transistors. 3 knob Tone bender sets from Small Bear are meant to be built with the stock circuit resistor values. They don't include a sheet of tweaked resistor values for each transistor set like they do with the Fuzz Face sets they sell. A germanium diode will be included in the set if its for the "3-knob" circuit.

phaseroll


Thanks very much for the replies -

Sorry if this came off as a customer service request posted to the forum.  I did send you an email at small bear, but realizing that somebody else might ask the same question decided to post on the forum (I saw similar questions on other forums where the answer was not spelled out as clearly as you guys have done here).

This wasn't intended to be a criticism of Small Bear Electronics or the parts labeling - I was guessing that this must be a common convention to label the transistors with their gains but wanted to make sure I wasn't using the wrong resistor values.  I gather that the highest gain transistor is reserved for the output stage.

Best,

Rick