Rangemaster clone - volume question

Dragonfly · November 05, 2007, 01:32:10 PM

Quote from: d95err on November 05, 2007, 01:29:14 PM
Another note (not sure if it was described by anone else) - the regular volume control on a Ragemaster is exactly that - a volume control. It does not change the amount of distortion created in the circuit. So it makes no sense to add an extra volume control after it.

Actually, give the trimpot into volume idea a try..it might just surprise you...the variation is subtle, but definitely there.

yeeshkul · November 05, 2007, 02:10:14 PM

that sounds like a solution !

Gus · November 05, 2007, 03:26:07 PM

Jan I am not sure what you are looking for from the posts in this thread.

Does your friend like the RM with the volume at max or close to max?
If so what you want might not be possible.

Think of the RM as another gain stage in your friends amp. It is EQing and boosting the preamp so it is a TOTAL system sound change. If the volume is reduced the preamp is not being distorted like your friend likes it from the EQ and boost of the RM

Maybe something that might work is a clean opamp booster with a fixed gain of 3(to keep it clean at 9VDC) with a volume pot and the RM.
You switch between the outputs of the RM or booster set for about the samevolume.
This is still not the same but maybe closer to what your friend wants

yeeshkul · November 05, 2007, 03:46:34 PM

Gus unfortunately i'm convinced he wants me do impossible. I just started playing with the idea of the J-FET stage after the RM with the master volume. I have never worked with J-FETs though. I seems like they use mostly J201, but i cannot find it here. I found BF245A, which seems to be quite close to that one.

yeeshkul · November 06, 2007, 12:25:57 PM

I added the Fetzer Valve after the Rangemaster stage. The sound is quite strange though, it is not consistent - like missbiased although i have 4.5V on drain. I used BF245A J-FET. Actually are there any parts of Fetzer Valve (as described at http://www.runoffgroove.com/fetzervalve.html ) i should omit?
I just put the Fetzer valve the way it is right after the output cap of the RM. Do you guys have any idea what may be wrong? I have never worked with FETS and to be honest i don't know much what i am doing here

I have 2 J-fets now:
BF245A with Vp: 1.94V / Idss: 5mA (measured)
J112 with Vp: 3V / Idss 40mA

i cannot find J201 here

DougH · November 06, 2007, 01:10:12 PM

Make sure you have the jfet pinout correct. You can leave out the 68k but it won't hurt to leave it in.

yeeshkul · November 06, 2007, 01:15:51 PM

pinout is correct - i checked data-sheet. It sounds much smoother when i leave out the 1M resistor, is that normal?

yeeshkul · November 06, 2007, 01:20:16 PM

however when i remove the 1M, bias goes to 8V at drain and the dtain trimpot (50k) doesn't have any influence....

yeeshkul · November 06, 2007, 01:32:50 PM

oh, i just realised that Fetzer Valve works with negative ground

. I guess i will need some sort of a P channel j-fet.

DougH · November 06, 2007, 01:44:07 PM

No, you use an N-channel JFET. You will need a ground reference on the gate. Leave the 1M in. This is why the bias is getting messed up when you remove it.

Do you have a coupling cap on the output of the JFET circuit?

yeeshkul · November 06, 2007, 02:03:35 PM

Yes i have 47n cap on the output (i have no volume pot added yet though). I will put the 1M back in, but Dough how come i can use N-FET in my positive ground circuit. Sorry for my silly questions, i am just reading about FETs, trying to get into it.

yeeshkul · November 06, 2007, 02:10:45 PM

do i have to turn the schematics sort of "upside down" with the 1M from gate to -9 and so on?

DougH · November 06, 2007, 02:24:57 PM

Oh, I see what you're saying. The RM is a pos-gnd circuit. Hmmm...

Why don't you draw a schematic and we'll go from there. It will be easier to figure out with a picture.

edit: If you want to try a P-channel JFET and make the JFET circuit positive ground, that would be the simplest solution.

yeeshkul · November 06, 2007, 03:46:37 PM

I guess i am gonna get one and keep elaborating tomorrow

yeeshkul · November 07, 2007, 09:43:25 AM

I am finally through it!
I got 2N3820 P-FET today (measured Vp=2.43V, Idss= 2.5mA) and added the Fetzer Valve circuit after RM stage. And it works and sounds great. And with the master volume you can play quited&distorted sound (which is smooth, with consistent sustain). I am so glad you guys here helped me!
The 22uF cap in source gives it actually a nice boost so i am not sure if i use deluxe version of the FV circuit (omitting the cap) yet.
I'm gonna actually build one for myself with a RM/RM+FV switch, i think the 1M resistor can work like pulldown for RM itself when the FV is cut off.

DougH · November 07, 2007, 11:18:34 AM

Glad you got it working!

Have fun.

evaninsky · August 17, 2010, 02:47:26 PM

I'm glad you figured this out !! can you explain it to me... maybe a schematic of the FV ?

jaysg · August 17, 2010, 07:02:42 PM

The Rangemaster third of the BYOC TriBoost has a 100K level pot at the tail end. The RM 10K pot is just a 10K resistor. I'm not sure exactly what the OP was planning, but you don't want two pots on it. It sounds fine to me.

newfish · August 18, 2010, 06:07:50 AM

I have a fixed 10k resistor in place of the original gain pot, and a 250K pot after the output cap.

I figured I can have the transistor working overtime *all the time* to provide that lovely 'break-up' sound - but at a controlled level for feeding in to a Fuzz Face.

This combination allows a host of different Fuzz / High Gain combinations depending on how much RM signal is fed into the FF.

...plus, I can adjust the RM's volume without the pot being scratchy, as it tends to be when adjusting the DC going into the tranny.

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Rangemaster clone - volume question