RangeFinder - Bias discussion

[phi1]

Here's my Range Finder build. I love the 8-way switch to tune the filter. The stock RM cap (position 2 on this switch) is quite thin, and I haven't enjoyed it into dirt pedals, but I've like 3-4 more. 5-6 sound cool clean, not full range transparent but a warm mid-focused sound.

Initially I biased to Collector = -7V according to info all over online, but once I got to position 5 and beyond, it distorted easily with my middle-of-the-road tele pickups, and the distortion was not very pleasant. I re-biased to around C=-4.5V, and I find it to be much nicer. It doesn't distort as much, and when it does it's much more pleasant to me. (I assume due to more symmetric clipping, vs the asymmetric and gating at the -7V setting). At the stock RM (position 2), it doesn't make much difference that I can hear.

I'm curious, has anyone else found biasing to around -4.5V more pleasant than the recommended -7V?

To fit it sideways in the 1590B, I did have to file the top and bottom of the pcb a bit, but I was watching for any traces (besides the GND fill) and made sure to leave clearance. I soldered the socketed resistor after the picture.

The enclosure is the new metallic candy red from Tayda. I have the copper, which is not sparkly, but this red is very noticeably sparkly. It's maybe not the most vintage look for this circuit, but I like it for something different than my other builds.

 

[masonlewisdiesel]

Here's my Range Finder build. I love the 8-way switch to tune the filter. The stock RM cap (position 2 on this switch) is quite thin, and I haven't enjoyed it into dirt pedals, but I've like 3-4 more. 5-6 sound cool clean, not full range transparent but a warm mid-focused sound.

Initially I biased to Collector = -7V according to info all over online, but once I got to position 5 and beyond, it distorted easily with my middle-of-the-road tele pickups, and the distortion was not very pleasant. I re-biased to around C=-4.5V, and I find it to be much nicer. It doesn't distort as much, and when it does it's much more pleasant to me. (I assume due to more symmetric clipping, vs the asymmetric and gating at the -7V setting). At the stock RM (position 2), it doesn't make much difference that I can hear.

I'm curious, has anyone else found biasing to around -4.5V more pleasant than the recommended -7V?

To fit it sideways in the 1590B, I did have to file the top and bottom of the pcb a bit, but I was watching for any traces (besides the GND fill) and made sure to leave clearance. I soldered the socketed resistor after the picture.

The enclosure is the new metallic candy red from Tayda. I have the copper, which is not sparkly, but this red is very noticeably sparkly. It's maybe not the most vintage look for this circuit, but I like it for something different than my other builds.

Phi1,

i'm wrapping up a build right now of a RangeFinder. I dig the PCB in there sideways!! i might have to try that out on my next one. Question: looking down, to the right (Bottom in your case) of the transistor...why the diode? R6 is the spot on my pcb. just curious.. awesome build!

-M. lewis

 

[phi1]

Ah.. yeah that’s typically the resistor for the LED. My initial plan was to use a relay bypass pcb with a nice soft switch. My own pcb design that functions the same as the PPCB one, but fits 1590B a little better, and I wrote my own code for. But my relay pcb doesn’t have a protection diode built in, so I was gonna use the diode there and jumper the LED pads, and use that SW pad (now a protected 9V line) to conveniently feed my bypass board. I opted to use a 3PDT stomp instead. I’m still using that pad to feed my led, but the diode is not necessary at all in this case

 

[masonlewisdiesel]

Ah.. yeah that’s typically the resistor for the LED. My initial plan was to use a relay bypass pcb with a nice soft switch. My own pcb design that functions the same as the PPCB one, but fits 1590B a little better, and I wrote my own code for. But my relay pcb doesn’t have a protection diode built in, so I was gonna use the diode there and jumper the LED pads, and use that SW pad (now a protected 9V line) to conveniently feed my bypass board. I opted to use a 3PDT stomp instead. I’m still using that pad to feed my led, but the diode is not necessary at all in this case

ahh. that makes sense now. when I grabbed my first round of Pcbs from ppcb I picked up 3 of the 3pdt breakout ((with LED))board# pcb594) which i havent used simply due to not knowing how.. I can use a similar method to what you described? is it as simple as jumping the pads? or do need to alter anything?
I was just about to run the CNC program for the holes and words... but I may have to go with your knob config. not a big fan of the over under way it comes.
Thanks!

 

[phi1]

Hmm idk how that board works since there’s no docs. But since there’s no resistor on the stomp/led board, I guess you still need the resistor in R6 of the RangeFinder. But other than that I don’t know how it’s configured, you could put up pictures if you want me to try to trace the patterns to figure it out that way.

By the way, I had to file the top and bottom of the RangeFinder pcb to get it to fit sideways in the 1590B. Gotta be careful not to damage any traces

 

[Chuck D. Bones]

-7V bias might be fine with a stock RangeMaster because most of the bass is attenuated. When you turn the RANGE knob and let more of the lower frequencies through, then you will need more headroom and biasing closer to Vcc will be advantageous.

 

[kristopher]

Get that bias trim pot out of there. And get it out in front with the Volume and Range. I have started to do that with most of the circuits that have a bias trim pot. Like Chuck said, every cap on the Range knob will have a different smooth-splatty bias position. Trust the Wizard.
That being said, I love your Pot placement. Turning the board was a great idea. High five.

 

[phi1]

-7V bias might be fine with a stock RangeMaster because most of the bass is attenuated. When you turn the RANGE knob and let more of the lower frequencies through, then you will need more headroom and biasing closer to Vcc will be advantageous.

by closer to Vcc do you mean closer to -9v on the collector? I found closer to -4.5v to have more headroom. On a trip so I won’t be able to mess with it for a few days