Rangemaster & 2204 type distortion

[StingRay85]

Decided to build a board of the simplest type of pedal, Dallas Rangemaster treble booster. Main reason is learn how to work with my oscilloscope, second reason is that I found an OC44 in my stash of Ge transistors and third because it's a bit easier than a fuzz face.


https://www.electrosmash.com/dallas-rangemaster
The interesting bit about this design is that it mostly seems to effect one side of the wave. So I guess that means the phase is of importance.

Now how will this work with a 2204? The high gain channel is also affecting mainly one side of the wave, first in V1B (cold clipper), followed by V2A which is biased in a way to keep the other side of the wave clean. So in a 2204, depending on the side of the wave you want to further distort, you need to chose between high input and low input, since these two are opposite phase?

What should be the preferred strategy to make this sound the best? I wouldn't be surprised that phase or out-of-phase makes the thing sound either good or simply horrible. I can think of scenarios that more attenuation between V1A and V1B is needed in case the high gain channel must be used for it to sound best, IIRC even with preamp volume extremely low, distortion starts even at low input levels.

 

[Pete Farrington]

Try scoping the waveform at the V2 DCCF output cathode, and you’ll see that the top and bottom greatly affected by the degree of overdrive.
You’re probably worrying over nothing.
Of greater concern is that the tonal balance of the 2204 etc preamp is already rather trebly, excessively so for many people, so an additional treble boost may be a step too far.

 

[StingRay85]

You're probably right Pete. I don't have the amp here right now, but I'll do that when it returns to me. I didn't get any feedback that the 2204 had too much treble, it's mostly used on an OX attenuator with IR, MV between 5 and 6, perhaps at these high volumes the treble is much less of an issue.

I do consider 22nF or 47nF instead of the 5nF value for the Rangemaster, so the boost covers most of the useful frequency range and only filters the low frequencies.

 

[Pete Farrington]

22nF or 47nF instead of the 5nF value for the Rangemaster

Give that a try out of course, but when I did, far too much signal was passed, causing a much greater degree of distortion. Unfortunately the extreme asymmetry of the distortion sounded more like ‘broken amp’ than the sweet overdrive hoped for.
On reflection, a regular Rangemaster might work well with the low input, if the amp’s gain control was turned up high enough to overcome the effect of the 1nF bright cap.

 

[StingRay85]

You tried this too? In any case indeed, the low input channel must be used when envisioning the 2204 as a pedal platform, the high input distorts way too quickly. I cannot even use it for bass, it sounds very bad no matter the preamp gain setting. I was afraid the phase could also make the low input sound bad, therefore needing to use the high gain channel but much more attenuated

 

[StingRay85]

Build the Rangemaster, seems to work the way it should. I cleaned out a Melos Echo Chamber for this, I got it for free and it has enough space and nice chassis with holes. The OC44 works well, and seems to be reasonably biased considering the battery is a little under 9V. Put a 12 nF input cap, with another 12nF paralleled on a push pull 10Kohm pot (so pull = full range boost, while the pot serves as the level control). 47 nF output cap. I used 125V mustard caps. Gotta say this positive ground confused me a lot, and wiring these jacks required a bit of troubleshooting. When plugging in it shorted the battery (but strange enough it still worked), luckily I noticed fast enough something was wrong because it heated a lot. But it's a cool effect, especially the responsiveness to the volume pot of the guitar.

 

[thetragichero]

the magic of a rangemaster is no better experienced than with an amp with a ton of low end like the orange graphics from the 70s (bunch of 68nf coupling caps? yeah that'll do it!). sabbath-style, if you will