Adding a transistor selector switch to a RangeFinder
- Thread starter BJG
- Start date
It can be done, but can I ask why?
Not sure you'll gain a ton vs the biasing issues you may have. I.e., the bias setting that's best for one transistor may not match the next. For Si, this is much less of a problem but for Ge, it could be a big issue.
If you find 2 germs that sound good without rebiasing, then yeah, a 3pdt will work.
You can usually get by with 2 poles, but it's probably not worth the effort in this circuit/easier to just mount them to the switch.
Get a switch with lugs, not pc pins, and wrap the legs through it for an easier time soldering. Match C, B, and E on each side and to the PCB.
Not sure you'll gain a ton vs the biasing issues you may have. I.e., the bias setting that's best for one transistor may not match the next. For Si, this is much less of a problem but for Ge, it could be a big issue.
If you find 2 germs that sound good without rebiasing, then yeah, a 3pdt will work.
You can usually get by with 2 poles, but it's probably not worth the effort in this circuit/easier to just mount them to the switch.
Get a switch with lugs, not pc pins, and wrap the legs through it for an easier time soldering. Match C, B, and E on each side and to the PCB.
I have an OC76 and a CV7007 that bias out within .1V of each other when swapped and I can't decide which one I prefer so I figured why not both. Ive been swapping them back and forth for a while and decided I like both and they feel different enough to have in one circuit. The OC76 has a little less low end and more aggression while the CV7007 feels a little thicker/smoother.
Last edited:
Feral Feline
Well-known member
You can order a PCB for transistor swapping:
MOONN WHYNOTBOTH? 2 transistors
MOONN WHYNOTMORE? 4 transistors
There used to be a few other places offering such a PCB, but I can't remember who and can't find the answer in my notes.
It's not hard to wire it up yourself, though...
More than likely, you'll want to use the 3PDT method:
When there's a common-leg, you can get away with a DPDT
Here's a 3-transistor Rotary option, in case you find yet one more transistor you like:
or
If you need to adjust the bias...
Lastly here's a Cornish thing that may inspire some extrapolation...
MOONN WHYNOTBOTH? 2 transistors
MOONN WHYNOTMORE? 4 transistors
There used to be a few other places offering such a PCB, but I can't remember who and can't find the answer in my notes.
It's not hard to wire it up yourself, though...
More than likely, you'll want to use the 3PDT method:
When there's a common-leg, you can get away with a DPDT
Here's a 3-transistor Rotary option, in case you find yet one more transistor you like:
or
If you need to adjust the bias...
Lastly here's a Cornish thing that may inspire some extrapolation...
Final Update:
I did a bracket style competition with the Ge transistors I had and originally landed on the CV7007 as my classic Rangemaster sound with a low gain MP39B as option two. I was about to wrap it up when I decided to throw a silicon PNP in there.
All the germaniums sounded like different versions of a Rangemaster while the silicon made it sound like a completely different pedal. There was a little high-gain buzz at first and the bias was high so I had to add some resistors to clean it up and it sounds great now. The silicon has a totally different EQ curve and gain characteristics than the CV7007.
I'm still new to super new to this, but I think I correctly diagramed out what I landed on. Before I box it up, I need to decide if I want the option on a toggle switch or another foot switch. I'm loving how many different sounds I can get with the capacitor array and transistor switch.
I did a bracket style competition with the Ge transistors I had and originally landed on the CV7007 as my classic Rangemaster sound with a low gain MP39B as option two. I was about to wrap it up when I decided to throw a silicon PNP in there.
All the germaniums sounded like different versions of a Rangemaster while the silicon made it sound like a completely different pedal. There was a little high-gain buzz at first and the bias was high so I had to add some resistors to clean it up and it sounds great now. The silicon has a totally different EQ curve and gain characteristics than the CV7007.
I'm still new to super new to this, but I think I correctly diagramed out what I landed on. Before I box it up, I need to decide if I want the option on a toggle switch or another foot switch. I'm loving how many different sounds I can get with the capacitor array and transistor switch.
