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Completed my Crown Jewel build, pedal sounds great, very happy with the range of sounds this thing can put out. Bought it with the MOSEFET boost module and it was ok, but wanted diff sound so got the Germ Boost. Sounds fantastic into the drive section on the CJ and really does a good job by itself, pushing the lead channel of my Marshall. Does the Rangemaster thing very well! But I have an issue, hoping someone with more tech knowledge can help with...


The Germ module comes with an AC128 and as far as I can tell, I'm supposed to be biasing this to -4.5V with the trimpot. (someone please correct me if I've got this wrong) Problem is, from the complete "off" position (full counter clockwise on the trim) to about -6.75V on the dmm, it's so noisy, it's basically unusable. Lots of static and hiss. The sound of the boost and into the drive sounds really good, but just way too much noise at that voltage. I have to push it all the way up (or down, I get confused with the +/- voltage) to full clockwise, about -7.5V. Sounds ok and seems pretty quiet at that level.



Not sure if I just need to replace the AC128 with another, or if I bias to something else, or if I should just leave it where it is. Any suggestions out there???


**UPDATE...

So I did some more searching and rumor and hearsay on the interwebs is that some folks that build high end, hand made Rangemaster clones suggest that you need to bias at 6.66v for the fat but quiet Ge sound. So I need some experts to weigh in here so I can stop googling things and getting more confused...

There are plenty of people more knowledgeable than I am on this subject. But my view is this - germanium transistors are very old devices that are simply all over the place in terms of where they want to bias. Biasing to a fixed voltage is a bit silly in my opinion. You can easily have 2 transistors that sound identical when one is biased at 4 volts and the other is biased at 7 volts. That's just how they are. When I use them, I just bias to the point where they sound good - low enough noise to use, enough boost/gain to drive the amp input, and with that cool, grainy germanium character.

If you're biasing to 7.5v and it sounds good, has low noise, and boosts the output enough to be usable, I'd say you have it dialed in. But that's just one nerd's opinion...

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You should have a range of about 2.5V ~ 7.5V give or take a half volt. Are you able to get that full range? I biased mine by ear, and coincidentally, it's at about 6.5V, but like Morgan said, you can't really expect every single one to bias at an exact number and sound exactly the same. It's best to just use your ear.

When you bias it to 7.5V, would you say that the noise it makes is about the same as your MOSFET boost?

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Please do not PM me. email is prefered. keith@buildyourownclone.com

Thanks for the replies, good to get some clarification for a non-tech guy! To answer the question - I can bias from somewhere around -2v to -7.5v as a range, with -6.5v to -7.5v (or close to when maxed) and it's pretty quiet. It doesn't sound like the MOSFET, it still has that sputtery Germ sound to it. I just left it maxed out around 7.5 since I was just tuning by ear and it seemed quiet.

I know Ge can be very finicky about the temp, power supply, etc. and can be hit or miss on quality of the part. I thought I might have a bad one, and maybe should swap out. But now I'm thinking I should just leave as is and just bias down to where the noise starts and I should be fine. You get so much misinformation out there and it's hard to decipher what you really should be doing.

Correct me if I'm wrong, but PNP Rangemasters usually bias to around -7v right? Not -4.5v akin to Fuzz Faces. That's what my stripboard DAM Red Rooster biases best at.

I even think that David Main of D*A*M pedals laughlingly recommends -6.66 volts

That certainly sounds consistent with the numbers being kicked around here. Mine runs right around -6.5V.

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“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Keep in mind that the original rangemaster had a 470k resistor where we are using a 1M trimpot. The idea being that if you have your trimpot set pretty much dead center, it would give you about the same resistance as the stock rangemaster, and this usually biases around 6.5V.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com