"Dark sounding" rangemaster

[Herec]

Hey guys,

I built a rangemaster. It works but...

It sounds kinda dark? And its not adding all that much gain (Db). Its almost the same volume as when it is bypassed.

Could bad capacitors be the suspect? I tried different transistors, and pretty much had the same results...

[hairyandy]

There's definitely something wrong there.  Are you sure that the transistor orientation is correct?  Sometimes a circuit will still function if the transistor is backwards but it will sound like crap.  Also, the tone of this circuit is very dependent on the amp or pedals that follow it.  Sometimes they'll act weird with a solid-state amp or in the presence of a buffer.  I would double check that you have the right value caps and resistors and that the transistor is biased correctly.

Good luck,

Andy

[R.G.]

When something doesn't sound quite right, especially if it's a well known, many-built circuit, the order to suspect problems in is:

1. Soldering errors.
2. Part value errors.
3. Wiring errors.
4. Polarity errors on polarize parts.
5. Pinout errors on ICs and transistors.
6. Board/etching flaws,
...
(this goes on for quite a while, long list)
...
187. Wrong phase of the moon.
188. Bad new parts.

[hairyandy]

187. Wrong phase of the moon.

Amen!  This one seems to get me every time...

Andy

[Herec]

I'm pretty sure the transistor oreintation is correct, its a well documented oc44. The other transistors are PNP types with the normal pinout.

I used some tropical fish capacitors, if they were bad or off spec could they affect the build? I've ordered some regular new production caps, i'll switch those in and see if anything changes...

[ildar]

"Other transistors"?
Doesn't the RM have just one?

[DryRoasted]

Check what the voltage of the transistors collector is at, if its not around 6 to 7V then you'll not likely get a decent sound.  to adjust the voltage, change the 68K resistor for a 100K pot wired for a variable resistor then set the pot for 68K (using your multimeter) then use the pot to adjust til the collector is at 6-7V then when your happy, whip out the pot and measure the resistance, then replace what was 68K resistor with the new one.

[Herec]

When I say other transistors, I have the 1 transistor socketed and test different transistors in it.

It is biased around 7 V (I think 7.3).

I used the "negative ground" layout at guitar gadgets. (I thought I could use NPN transistors, but alas they don't work and thats when I read exactly what I had made  .) Turns out its a negative ground layout for PNP transistors. Maybe if I changed it to the conventional positive ground it would sound like it should?

Here's the negative ground layout for PNP transistors that I am currently using.



Here's the posistive ground layout for PNP transistors.

[Herec]

No more thoughts?

I'm getting some parts soon, be able to fiddle with it then...

[R.G.]

Nothing much to add. Lots of people get into trouble with negative ground adaptations of positive ground circuits.

[hairyandy]

I've built a lot of negative-ground PNP Rangemasters with no problems using my layout here:

http://aronnelson.com/gallery/album26/Rangemaster

This circuit is so simple that you should be able to compare what you did with the GGG layout to any of the others out there to see if you have made any mistakes.

Andy