Built a Rangemaster (NPN version)

[vanhansen]

I think I have a new favorite booster.  Last night I whipped together an NPN version of the famed Dallas Rangemaster on the breadboard using an OC140 that I got from MartyMart (thanks, Marty).  I'm not sure what the gain of these things are but boy was I surprised.  Originally I was going to make the PNP version but realized I didn't have any PNP transistors but I did remember having the OC140's.  Perfect. 

This is the schematic I started with:


Other than the transistor being NPN and having to turn the electrolytic caps around, I didn't have 25uf for the cap off the emitter so I used a 22uf instead.  All the other values are the same.  My breadboard has a 100uf power filter cap on it across the +/- rails before tapping in for the circuits so I left the 25uf filter cap out.

On the clean channel of my SS amp it's a nice fuzz like sound. On the OD channel of the amp, I backed off the gain so it's just a nice mellow overdrive but the Rangemaster throws it over the edge.  It's a very nice sound and the 60's come alive with my Strat. 

I'm going to try a 10k Linear pot and see how that sounds.  Saw that in another thread from last year about how it evens out the change of the gain across the entire travel of the pot.

I noticed on the schematic above that it says that the 4.7k may be 3.9k in some cases.  Still trying to figure out what that would do.  Couldn't find a 3.9k in my stash last night.  I've also seen a few schematics that have a .005uf input cap rather than .0068uf.  Is there that much of a difference between the two?

[dv8]

So, have you tried on the Marshall yet?

-brian

[vanhansen]

So, have you tried on the Marshall yet?

-brian

Nope.   

My cab isn't at home and I haven't gotten a 2x12 yet so I can use it at home.  If we jam this weekend, I'll be trying it then because I am perfing this thing and boxing it up before Sunday.

[Doug_H]

I like the OC140 too and think it sounds great.

4.7k vs 3.9k will affect the collector voltage/bias. Set it where you like the sound and forget it.

There is not much difference between .005u and .0068u input cap. I use the .0068 because the .005 sounds a little thin to me, but we're only talking hairline differences here.

Doug

[vanhansen]

Duh!!,  Thanks, Doug.  I shoulda known that resistor had something to do with the bias on the collector since it is going to ground off the emitter.     I'll see if I can find a 3.9k and try that out.

The .0068 cap sounds pretty good.  I was expecting it to sound thinner than it actually does actually.  It was a pleasant surprise that it didn't.

I noticed on Phillip's schematic (Fuzz Central) that he has a 1M resistor before the input cap to ground to set the input Z.  Is it really necessary with the RM?

And why is the emitter electro cap 25uf on some schematics but 47uf on others?  What was it in the original?  I've seen so many variations I don't know which is the original anymore. 

[Doug_H]

1M to ground is just to de-pop the switch. You should put one on the output too. I don't remember what the original had for a bypass cap. IIRC, I didn't hear any difference between 47u and 22u so I think I went with 22u. Check R.G.'s article for info on that.

Doug

[Khas Evets]

I personally think the input cap makes a big difference in this circuit. I've built one with a rotary selecting five caps (.005,.0068,.01,.02,.047). I'm always switching between the first three, and the two larger ones are good for a dark fuzzy sound. I'd at least socket the input cap.

[vanhansen]

Thanks, Doug.  I'll do that.  I'm sketching out a perf layout now.  The pulldown resistors will be added in.  Thanks for that clarification.

Khas:  The input cap will definitely be socketed but I'm not going to put a selector switch in it yet.  If anything, I'll settle on 2 and put a DPDT in there with the caps on it.

[TheBigMan]

Just built a Fuzz Face with CV7112s (Mil Spec OC140s) and it sounds pretty decent.  Rangemaster is next once I do/modify a layout including treble/mid/full range boost input caps.  Got to love the NPN Ge's though, the spec on them is so much better than the PNPs leakage wise.

[Khas Evets]

You can get three cap values using a DPDT switch. Wire a .005 cap in the circuit, then use the switch to add parallel caps (adding to .005). So if you had .018 and .005 on the switch, you would get .005, .0068 and .01.

[vanhansen]

Yeah, I'm lovin' the GE NPN's.  They sound really nice.  A Fuzz Face may be next.  The lower the parts count the better.

Khas: Doing what you're saying, is that assuming the switch is on-off-on?  With an on-on DPDT switch, you have two options and either one would be parallel with whatever is wired in circuit.

I got some small breadboard squares from Rat Shack during lunch and a couple 47uf caps but they didn't have any 10k linear pots.  Oh well.  I'll just stick with the 10k analog.

[Khas Evets]

Yes it should be on-off-on. If all you have is on-on, then I would just wire the two values to each side of the switch.

[vanhansen]

Cool.  Thanks.  I'm not sure if I have any DPDT's in the stockpile right now but that may be something I add in later.  Right now I'm just wanting to get it perfed and in boxed up

I did sketch out a perfboard layout using the small template from ROG and following the schematic from Aron's schematics page.  The emittor bias resistor and bypass cap are what appear to be the original values.

[vanhansen]

Put a 47uf cap in place of the 22uf for the bypass cap and found a 3.9k resistor so I put that in place of the 4.7k.  It made a difference, for the better actually.  It's biased just right, a little over 7 volts.  The tone is incredible.

[vanhansen]

She's all boxed up in a Hammond 1590B.  No LED though.  It's pretty tough to not know when the thing is on though...lol.  Ran in to a problem with the cover hitting the solder connections so I found a good use for the Radio Shack electro cap packages.  Put the cardboard between the perfboard and the cover. 

When I had it on the breadboard, I "misread" one of my pots so I was actually using 100k for the gain instead of 10k.  Ooops.    It's now 10k and still sounds great, just not as much gain than before.

Oh, and the perf layout I posted above is verified as OK. 

[cab42]

You can get three cap values using a DPDT switch. Wire a .005 cap in the circuit, then use the switch to add parallel caps (adding to .005). So if you had .018 and .005 on the switch, you would get .005, .0068 and .01.

I used almost the exact same values for my input caps. And also tho OC140.

You may wan't to add Phillips temperature stablilty mod http://fuzzcentral.tripod.com/rangemaster.html.

I also made a vero layout for it: http://aronnelson.com/gallery/Cab42s-layouts/vero_rangeblaster_3

Sounds great.

Regards

Carsten

[vanessa]

You may wan't to add Phillips temperature stablilty mod.

I'm not really sure why Phillip has a temp diode in his layout/shem. Having taken the idea from the Plate to Plate 'Brit-Face' article (http://www.geocities.com/SunsetStrip/Studio/2987/britface.html they outline in what application you would use one.

The why... In the Brit-Face article they are saying that the temperature 'run-away' is only in Q1 of a Fuzz Face. Q2 does not need one as it is covered by the 1k emitter pot.

In the Rangemaster it has a the 470k off the bass, the 3.9k resistor off the emitter and has a 10k pot off the collector. This should provide the same type temperature stability as the Q2 of the fuzz face in the above article. I quote the GEO article "The 470K resistor, in conjunction with the input divider helps set and stabilize the bias point against drift and temperature variations".

Not to mention that use of a diode does bring noise into the circuit. You need to have a diode that has very low leakage to avoid this in a Fuzz Face and if you don't need one in the Rangemaster why would you use one?

[vanhansen]

I saw those mods but don't have any germanium diodes laying around.  Plus, I wanted it to be as close to the way it was as possible.  The pulldown resistors are a must though.  No pop whatsoever. 

I ran it through the ringer today, played it through the Marshall for a few hours.  Wow, talk about amazing.  It didn't color the tone much at all.  The amp still sounded like itself, just with a little more kick to it.  I really like how the Rangemaster works with it.

I think I'm going to put a DPDT on-on switch and go between the stock 0.0068uf input cap and 0.01uf.  The stock value works great with the Les Paul but 0.01uf is better for the Strat. 

Now, if I can just get rid of the damn radio frequency coming in.  On my wah, my ZW OD (both not DIY but purchase) and the Rangemaster (Hammond 1950B enclosure) I just built pick up AM 820 at my brother-in-laws, but not at home.  Power is by battery only.  The first thing that popped in to my mind was that they don't have an output buffer but my Marsha Valve doesn't either and it does not have this problem.  Sure, it's cool when a hockey game is on and we're jammin on a Saturday night.  Just stop, listen for the score, play on..lol.  But in all honest, I'd like to eliminate it.   I'm convinced there's a tower nearby.

How do you get rid of this stuff?

[vanessa]

I just built a Java Boost (Rangemaster clone). In the JB the .0068uf and the .01uf are switched in parallel (this helps to avoid pops). I really like this one the best with my telecaster's single coils. I really have no use for the .0068uf and .047uf combo. It's too bassy for my amps and worse (for me) with humbuckers.

For the radio stuff I would check your wiring and your amps power source. I try to keep inputs, outputs, and grounds away from each other (when I can...). Also bad grounding in your signal chain (guitar, pedals, and amps) can be a source of noise as well as the house itself.

[Dragonfly]

Now, if I can just get rid of the damn radio frequency coming in. 

How do you get rid of this stuff?

try a 10k resistor on the input of the circuit.....

INPUT-------->[   10k  ]-------->INPUT CAPACITOR, ETC....

that usually works without interfering much with the sound of the circuit...ive even been able to kill the radio noise with smaller value resistors, so experiment and find which value works for you...

AC