Author Topic: Correct approach for Si/Ge switchable Rangemaster  (Read 819 times)

Bandwagonesque

Correct approach for Si/Ge switchable Rangemaster
« on: July 16, 2021, 03:24:30 PM »
Hello folks. Going to be building a fryer npn treble booster this weekend and wanted to build it as such to have switchable silicon and germanium npn transistors. When I usually do this with a fuzz pedal its as easy as just sending the transistor and bias resistor at the collector to a switch or daughterboard, but i've heard that the 'correct' approach when doing this with a rangemaster-esque circuit is to switch between 2 complete circuits. Can someone tell me if it matters at all or if I really should go about building another circuit for the germanium side?

And can anyone tell me what are some good germanium npn's to use? Thanks a bunch everyone :)

Pete Moore

Re: Correct approach for Si/Ge switchable Rangemaster
« Reply #1 on: July 17, 2021, 03:54:12 PM »
Ge selected for leakage ma. And gain ="requirements,
Si much simpler, just select.
Small Bear Electronics has selections of both.
Each it's owATConsidering separate circuits, bias, voicing..
See Tri-Bootser schematic (mosfet si ge).

idy

Re: Correct approach for Si/Ge switchable Rangemaster
« Reply #2 on: July 17, 2021, 07:39:27 PM »
The thing you are asking about, popping a silicon Q into a Rangemaster, is not a thing. Lots of threads discuss making a booster with silicon that will do some of the same thing as a Rmaster... but they are different circuits. The biasing arrangement will have to be different. Silicon has different impedance, so its frequency response is different. This means a different input cap at least to bring things back into "range." Maybe add extra a "tiny" cap between C and B...If you really care you will get a breadboard and try it.

OTOH, having two or three different boosts to play with is fun, maybe a vital piece of exploration. The BYOC Tri-boost allowed me and my friends to hear the difference between Ge, Si, and MOSFET. I think it would be even "funner" to have them as "chainable",  able to over drive each other. So the Tri-boost was very helpful as a diagnostic tool, pretty useless on the pedal board. It allowed you to find if you and your rig belong to one of three "tribes." Once you picked one, the others become irrelevant.

Rob Strand

Re: Correct approach for Si/Ge switchable Rangemaster
« Reply #3 on: July 17, 2021, 08:31:21 PM »
If you don't want popping building separate circuits are the way to go.
However you want to do it so you have a single volume control.

You need to wire the selector switch to switch the inputs to the input socket and the output to the volume pot.

You need separate input and output caps.  If you "re-use" those you will get pops.

You also need to add 2.2M to10M resistors on the input and output caps to ground.
So that's four added resistors.  You need those top prevent pops.
« Last Edit: July 17, 2021, 09:11:48 PM by Rob Strand »
Plopping around the pot since an early age.

idy

Re: Correct approach for Si/Ge switchable Rangemaster
« Reply #4 on: July 18, 2021, 10:07:26 AM »
Two separate circuits with double gang volume pot? Of course if gain differs, settings will too.

kaycee

Re: Correct approach for Si/Ge switchable Rangemaster
« Reply #5 on: July 18, 2021, 05:50:07 PM »
Do a search for my 'triple treble booster' post. Has schematics, layouts and switching diagrams.

Rob Strand

Re: Correct approach for Si/Ge switchable Rangemaster
« Reply #6 on: July 18, 2021, 07:08:04 PM »
Here's something close.   Should have 2.2M to ground on each of the input/output caps to prevent pops.
(not need for the 2M2 at the input shown.)

Notice you need to change how the volume control is done.
Fixed resistors on the collectors then the outputs feed a common 100k volume pot.

http://thermionic-studios.com/wiki/index.php?title=Tri_Boost

« Last Edit: July 18, 2021, 10:55:20 PM by Rob Strand »
Plopping around the pot since an early age.

Bandwagonesque

Re: Correct approach for Si/Ge switchable Rangemaster
« Reply #7 on: July 20, 2021, 04:38:45 PM »
thanks a bunch folks for all of your input and help so far on this. I would've approached this in a real bad way had it not been for this thread so its much appreciated :) :) :)