Where is unity gain on a Rangemaster?

[gnugear]

I've heard that it's supposed to reach unity gain at 12 oclock but mine is nowhere close to that. It seems like I MIGHT reach unity gain when the knob is cranked all the way up.

[brett]

Unity gain should be well before max gain as far as I am aware.
Wot transistor are you using?

[bwanasonic]

Yes, I would say unity might even be a bit shy of 12'oclock, with around 2'oclock being the sweet spot. Are you testing it alone in the signal chain? Have you checked the pin voltages? Any part substitutions? What are testing it into?

Kerry M

[gnugear]

I'm trying out a couple of different transistors. I've got a Mullard OC44, a BC108, a BC109, and a NOS Germanium from Smallbear. The two germaniums seem to put out more gain than the silicons!

Well, something definitely doesn't seem right because 12oclock is like HALF the volume as the bypassed signal.

I'm running straight into a Marshall plexi.

Jeez, you think it would be hard to screw up a circuit with only three resistors and a couple of caps!

[Pedal love]

What power supply you run? also test the potentiometer.pl

[petemoore]

The Rangemaster is PNP Pos Gnd...originally.
 ...of the Q's you mentioned...
 The GE's are PNP's and should work in there.
 The Si's are NPN and won't work

[gnugear]

I'll check my 10k pot. I haven't done that yet and maybe it's off by quite a bit. By the way, is there another pot that I can substitute for even more gain.

Are all Si's NPN?

[R.G.]

Well, something definitely doesn't seem right because 12oclock is like HALF the volume as the bypassed signal.

It is quite difficult to relate something like half volume to half the pot rotation, as the human ear has a logarithmic response to loudness and pots have different tapers. I suspect that you may be having problems with pot taper. Linear taper pots have the appearance of getting loud quickly and then not much happens for a while as you rotate them. Logarithmic or audio taper pots have a more nearly linear rotation versus apparent loudness character.

But there is on top of that the basic gain of the circuit, which varies a lot from transistor to transistor. Saying "unity gain is half the pot rotation" can't be anything except a rough guide unless the circuit is specifically designed to make that true - and the Rangemaster is not.

You may have a low gain transistor or a circuit mistake.

Are all Si's NPN?

No, although silicon is more naturally a NPN material than PNP. Germanium is more naturally a PNP material. There are the other kinds in both silicon and germanium.

[analogmike]

HI,

Unity gain on a good rangemaster clone should be at 9:00 on the volume knob, with bias set correct as on RGs website.

from my website:
Has about the same output level ON and OFF with the vol knob set at 9:00. At 11:00 there is about a 10dB boost, which sounds twice as loud. At 12:00 there is a 13dB boost, and up all the way is about an 18dB boost which is nearly twice as loud as it was at 11:00.

have fun!

[gnugear]

What effect will the 10k pot have if it's not to spec? I'm looking around for some spares and all I have is a 1M pot that I could try. Do you think that could be my output problem?

[gnugear]

Here's another question ... does it matter if the pot is log or linear?

[ESPguitar]

Here's another question ... does it matter if the pot is log or linear?

Test youself:P

A log pot will "start" gently with small volume change and then when you get to almost 3:5 of the turn boom and the volume raises like hell:P

Easy and bad explained..
But, it won't hurt the circuit :wink:

RB

[dansamp]

i have some pnp transistors that i bought from small bear for the purpose of making a rangemaster
they are biased properly and unity gain is no where near 9:00
on the pot it is closer to 12:00 and i agree the sweet spot is between 2:00-3:00
i was looking to get unity gain sooner
i also built a java boost clone using a NTE158
and that sounds better than my rangemaster clone
but unity gain is also around 12:00
and the sweet spot is also around 2:00

would a tested "good" OC44 make things any better ?



thanks

[ESPguitar]

i have some pnp transistors that i bought from small bear for the purpose of making a rangemaster
they are biased properly and unity gain is no where near 9:00
on the pot it is closer to 12:00 and i agree the sweet spot is between 2:00-3:00
i was looking to get unity gain sooner
i also built a java boost clone using a NTE158
and that sounds better than my rangemaster clone
but unity gain is also around 12:00
and the sweet spot is also around 2:00

would a tested "good" OC44 make things any better ?



thanks

I bought a NTE 158 for my rangemaster the first time i made it.. It didn't work at all.. It was waaaaaay toooooo leaky..

And i was told that NTE's often are too leaky for audio purpose.. I don't know though.. I'm just familiar with the one 158 i own:P

[gnugear]

Ah, I figured it out. One of my resistors had a cold solder joint ... it reaches unity gain at around 12 on the dial, and then starts to pummel my amp after that.