Multiple transistor rangemaster question.

[frank_p]

I want to build a rangemaster with a switch to select between a silicon and a germanium transistor.
Now, I can't decide between a positive (pnp) or a negative (npn) ground version.

I was just beginning to do it with two npn transistors, and then I asked myself why not with PNPs with positive ground.

What would be the best option and why...

Noise, uses with other stompboxes, ... (and I don't know)

What would you do ?

For me now, I don't see differences.  But it does not harm to ask for some advices...

[kurtlives]

I would go with PNP positive ground. Its the only way to get the true RM sound imo. I found the NPN versions just don't cut it.

Also I think you will have issues with switching between sili and germ.

When I built my RM I had a switch for OC44 and OC71. I used a pot to bias and it was such a fine (small) portion of the pot that I could use to bias them both so they sounded good.

I could bias the OC44 to sound amazing but then the OC71 wouldn't even work, it was at cutoff. The bias line I guess was just so small. I had to find a middle reference point where both sounded good and both worked.


Anyways if you did have this sili germ switch I would add a bias pot.

[DougH]

I would go with PNP positive ground. Its the only way to get the true RM sound imo. I found the NPN versions just don't cut it.

[earthtonesaudio]

Why wouldn't you just flip the schematic "upside down" and make it negative ground PNP?

Maybe there's some subtlety I'm missing, but as long as the potentials are the same the circuit doesn't care if the schematic looks funny.

[frequencycentral]

Such a simple circuit, why not just build it twice, one Si and one Ge?

[mac]

frank,

Just build it positive gnd if PNP. Who says that gnd has to be neg? Be positive!
Mine is pos gnd and it sounds perfect. The Matsushita 2sa102 Ge in it is amazing. And the varaible input cap makes it more versatile.

When you switch from Ge to Si you need to raise the 68k to 120k or 150k so as to have near 6.7 - 7.0v at Vc.
Besides, you might hear some pop.

I'd try to get a low gain PNP Si (maybe a BD140-10), and build both in the same box with a switch. But I bet you'll never use the Si!

Remember to add a 1 - 2.2 M after the output cap to avoid bypass switch pops.

mac

[DougH]

I'd build two separate circuits and optimize each for its transistor. Then if you want them in the same box, implement a way of switching between the circuits via bypass or etc.

[jacobyjd]

another possibility might be to get a switch with enough poles to do both the transistor switching AND bias resistor switching...

[Solidhex]

If you used a 3pdt switch or even a 4pdt like this: Http://www.smallbearelec.com/Detail.bok?no=709  you could switch between the transistors and a specific emitter resistor biased for each transistor. I've never found external rangemaster bias controls to be much "fun". More of a set it and forget it thing for me. That way you wouldn't have to readjust the bias every time you switch between the tranny's.

--Brad

[Solidhex]

haha dur!

--Brad

[kurtlives]

I would go with PNP positive ground. Its the only way to get the true RM sound imo. I found the NPN versions just don't cut it.

What?

I have found it dosent sound as good with NPN transistors as PNP.

[frank_p]

Ha ha, Thanks guys, yesterday I was saying to myself: "can't belive that I am asking this question, it sounds so stupid,but I still don't know what to do..."

And today everybody have an answer !

I think I RELLY love this forum...

FHP

[petemoore]

  Idunno..3PDT put each transistors bias network 'inside' the transistor switching EBC assignment to the 'columns' [each column being a throw on each side of the pole.
  no room left for indicator, you can probably tell which is Si and Ge from the tone or the output level.

[frank_p]

  Idunno..3PDT put each transistors bias network 'inside' the transistor switching EBC assignment to the 'columns' [each column being a throw on each side of the pole.
  no room left for indicator, you can probably tell which is Si and Ge from the tone or the output level.

Yes that is exactly what I am going to make Peter. 

[jacobyjd]

I generally don't bother with indicators for toggle switches--you can usually see where the lever is pointing

[DougH]

I would go with PNP positive ground. Its the only way to get the true RM sound imo. I found the NPN versions just don't cut it.

What?

I have found it dosent sound as good with NPN transistors as PNP.

Yeah, I guess this doesn't "have the true RM sound", whatever that is: http://www.aronnelson.com/gallery/main.php/v/DougH/booster/NPN_RM/

[kurtlives]

I would go with PNP positive ground. Its the only way to get the true RM sound imo. I found the NPN versions just don't cut it.

What?

I have found it dosent sound as good with NPN transistors as PNP.

Yeah, I guess this doesn't "have the true RM sound", whatever that is: http://www.aronnelson.com/gallery/main.php/v/DougH/booster/NPN_RM/

Nope that's all wrong...Wrong Wrong Wrong!

Just joking


I'm not going to argue this one with you. I set up two Range Masters one  PNP one NPN on my bread board a while ago and I thought the PNP sounded better and more of a classic RM sound to my ears. And yes I did set them up the same, bias, etc.

[jacobyjd]

With the amount of variance in Ge transistor parts, it seems like it would be more likely that you'd have some difference between any 2 transistors...I would venture a guess that it has little to do with whether they're PNP or NPN.

[DougH]

Right. For Rangemasters, my NPN Ge's sound much better than my PNP's. But I know it has nothing to do with that. It's just differences in transistor models, etc.

[earthtonesaudio]

[Non-essential technical info]
Just to be clear, there is a difference between NPN and PNP transistors, all other factors being equal, due to the fact that electrons move about more easily than "holes."
Whether you, or anyone, can actually hear a difference in a given circuit is a completely different matter.
[/Non-essential technical info]