Myths, Legends and the Mojo of the Dallas Rangemaster

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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DrNomis
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Post by DrNomis »

Electric Warrior wrote:Funny that you're having problems. I always thought of the rangemaster as an easy circuit. Just pop in a transistor and it works :D Most OC and japanese types worked well for me. Q1C voltage didn't change much at all. Did you have the volume pot turned down when you measured?

I found that it works equally well with single coils and humbuckers. Might be differnt with active pickups.
It does boost a lot of midrange (yours should have a tad less midrange with the 47k as you changed the high pass filters' cutoff frequency). Here's frequency response of the high pass filter:
I always thought that the Rangemaster was a dead easy circuit to build too, what can go wrong with so few parts?, I've got some unmarked Germanium transistors that look like they should work fine so I'll check them with my semiconductor analyser and I'll use the one with the lowest leakage, when I measured the collector voltage the setting of the volume pot had no effect on it, in the Rangemaster circuit, the output comes from the wiper lug of the volume pot, the other two lugs connect to the carbon track inside the pot, so the volume pot looks like a 10k fixed resistor to the transistor.... :thumbsup
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Post by kleuck »

Not so simple, because the input impedance, and so the frequency corner of the filter mainly relies on the transistor's gain, which can vary a lot, so the sound.
As for the bias : don't rely on "official" numbers, i've tried a few different transistors (OCxx, Japanese ones, European ones) and i've come to the conclusion that each can sound good (but slightly differently from the others) but definitely NOT with the "2 volts drop" : you have to tweak the bias for each brand.
OC44/CV7003 sound best with 2 volts of drop, most others are best with more, between 2,5 and 3,5.
My two cents.
Randall Aïken said :
Q: Is there any advantage to using solder with a 2% silver content?
A: Yes. Silver solder keeps werewolves away from your amp.

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Post by DrNomis »

kleuck wrote:Not so simple, because the input impedance, and so the frequency corner of the filter mainly relies on the transistor's gain, which can vary a lot, so the sound.
As for the bias : don't rely on "official" numbers, i've tried a few different transistors (OCxx, Japanese ones, European ones) and i've come to the conclusion that each can sound good (but slightly differently from the others) but definitely NOT with the "2 volts drop" : you have to tweak the bias for each brand.
OC44/CV7003 sound best with 2 volts of drop, most others are best with more, between 2,5 and 3,5.
My two cents.

I've just been doing some more testing of my breadboarded version of the Rangemaster circuit, I've got a Marshall MG Series 100DFX 100 Watt combo amp that a friend of mine has asked me to service for him, it crackles a bit, anyway I tried the breadboarded circuit with the Marshall amp and the circuit sounds like a whole different beast going into it, especially on the Overdrive channel...Wow!!, I can definitely hear the response of the circuit now, my little Legacy Valve Edition 5 Plus amp tends to have a darker midrange tone compared to the Marshall so I think it was fooling my ears a bit, out of the four OC44 Transistors I've got, I've managed to narrow it down to two that seem to bias up and sound good, I had to change the 470k to 2M2 though, one of the transistors biases up with -6.7V on it's collector, the other biases up with -6.5V, they both do sound good through the Marshall amp and really boost the output of my Vintage noiseless pickups, this whole exercise is actually teaching me alot about how to get a good tone from the pedals I make, it's not just the pedal, it's your whole signal chain..... :thumbsup

I'll definitely post some clips soon.... :thumbsup
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Post by DrNomis »

kleuck wrote:Not so simple, because the input impedance, and so the frequency corner of the filter mainly relies on the transistor's gain, which can vary a lot, so the sound.
As for the bias : don't rely on "official" numbers, i've tried a few different transistors (OCxx, Japanese ones, European ones) and i've come to the conclusion that each can sound good (but slightly differently from the others) but definitely NOT with the "2 volts drop" : you have to tweak the bias for each brand.
OC44/CV7003 sound best with 2 volts of drop, most others are best with more, between 2,5 and 3,5.
My two cents.
By "2 volts drop", I'm assuming you mean the voltage drop across the 10k pot, one of the two OC44 transistors that do sound good through the Marshall gives a 2.6V drop across the 10k Pot, the other gives 3.0V, and I think it sounds the best of the two so I'm going to use it in my Rangemaster build, I think I've got this one nailed now.... cheers for the help mate..... :thumbsup
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Post by kleuck »

Yes, sorry if i'm not always clear.
Randall Aïken said :
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A: Yes. Silver solder keeps werewolves away from your amp.

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Post by DrNomis »

kleuck wrote:Yes, sorry if i'm not always clear.

That's alright mate.... :thumbsup
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Post by kleuck »

When you are happy with your circuit, i suggest you to try some caps of different technologies but same capacity, cheap ceramics and Mallory 150 for example.
Randall Aïken said :
Q: Is there any advantage to using solder with a 2% silver content?
A: Yes. Silver solder keeps werewolves away from your amp.

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Post by DrNomis »

Will do, I was thinking of seeing if I could source a 10nF and a 5n6 Mustard style cap online or something else like that.... :thumbsup
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Post by kleuck »

There's the Sozo.
Randall Aïken said :
Q: Is there any advantage to using solder with a 2% silver content?
A: Yes. Silver solder keeps werewolves away from your amp.

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Post by DrNomis »

Never heard of those before, I definitely want to use caps that are in an RT style, rather than RB style caps, I'll do some googling and see what I can find..... :thumbsup
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Post by kleuck »

DrNomis wrote:RT style, rather than RB style caps
:scratch:
http://www.sozoamplification.com/purchase2.html
Randall Aïken said :
Q: Is there any advantage to using solder with a 2% silver content?
A: Yes. Silver solder keeps werewolves away from your amp.

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Post by DrNomis »

Doh....... :slap:
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Post by DrNomis »

I went to the Sozo website and bookmarked their homepage, definitely going to start buying some stuff from them soon, cheers ..... :thumbsup
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Post by BEMUSofNrthAmrca »

Awesome thread. I haven't made my way through all 10 pages yet. I'm a huge Rangemaster fan.

I use a Gibson SG with Lollar p-90s, into Scott Humphreys Crispy Creme Vitamin G Treble Booster (based off the rangemaster). I was able to get my hands on one of his early prototypes, so it has sockets for the transistor and a few capacitors. I'm able to switch between NKT275, and AC188 trannies. I am really liking the NKT right now.

I usually run this into a Fuzz pedal (Sunface or HP-1) then into my Marshall Superbass.

I find the treble booster is great for getting the note definition I lack when using high gain fuzz into an unmodded Super Bass amp.

I'm planning my own limited Rangemaster clone build soon, I'm just wondering whether using carbon composite resistors is worth it.

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Post by sinner »

BEMUSofNrthAmrca wrote:I'm just wondering whether using carbon composite resistors is worth it.
Yes, they are if you like the hiss ;) Use metal films, it's better choice for rangemaster IMO - Vishay CCF60 is my main choice for MF resistors as they also looks cool

Do you have any internal shots of your Superbass and fancy to share?

Cheers

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Post by LucifersTrip »

I doubt if you'll be able to hear any difference with any choice of resistor or cap. As long as you use a low leak transistor with proper gain and bias the collector to ~ 6.6 - 7.2v, you'll be good...

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Post by DrNomis »

I'm just putting the finishing touches on the enclosure for my Rangemaster build, stay tuned for some pics..... :thumbsup
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Post by DrNomis »

Sorry for the double-posting, I've finished working on my Rangemaster build and it's all working good, I found that all 4 of my OC44 transistors really don't have enough gain for use in this particular design, so I went hunting through my germanium transistors to see if I could find one that would work better, well I found an RCA PNP Germanium transistor that measured Hfe=190 and Leakage .110mA on my Semiconductor Analyser so I soldered it onto the tagboard, the collector voltage was in the right range so I decided to give it a tryout, I plugged it into my little Legacy 5Watt Class-A Single Ended combo amp, set it's gain control on full, and set the master control at a low level, I played my guitar with the Rangemasterbypassed, and only got a slight amount of breakup, when I switched in the Rangemaster it was a totally different story, now I had a good crunchy rock tone.... :thumbsup

The actual tonal colour sounds about right, very similar to what I've hear when watching demos on youtube, so what does that mean?, you don't necessarily need to use the exact same type of Germanium transistor as the originals did, as long as the transistor you're using had enough gain and a reasonably low leakage, and it biases-up with about 6.8V on it's collector, you should be able to use whatever Ge transistor you can find..... :thumbsup

After all, it's only a simple common-emitter amplifier that has it's frequency response modified... :thumbsup


Will post some pics of my build soon.... :thumbsup
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Post by DrNomis »

Okay, I've just checked the collector voltage in my Rangemaster build, how's this, with these resistor and pot values, and with the transistor measuring Hfe=190, Leakage=.110mA (110 micro-amps), the collector voltage is -6.88V:

X 1 4k7/5% 1Watt Carbon Film.

X 1 68k/5% 1Watt Carbon Film.

X1 470k/5% 1Watt Carbon Film.

X1 10k Log 16mm.


I think I've well and truly got my Rangemaster build nailed.... :thumbsup
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Post by DrNomis »

Okay, here are a couple of pics of my Rangemaster build:
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Rangemaster Build
Rangemaster Build
Rangemaster Build Insides
Rangemaster Build Insides
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