Dallas Rangemaster info

I did up a version of the rangemaster with a Fet K30A , worked ok for a bit then died ,not sure if it was user error or not .
I did a bit of a search here but it didnt turn up much , but I do remember CJ mentioning the Dallas somewhere back along the way .
I would like to try germanium transistor , I have a few odd old transistors that might do .

If anyone has knowledge of this simple treble boost ,you might post a link to further info on it ,or alternatively post a schem of the version you built .
Thanks again.
Ill post a pic of the circuit I used later on .

Search for "rangemaster treble booster geofx"
There was a thread at ampage years ago late 90's IIRC about tracing it.

If you don't have a Ge try a power silicon transistor NPN with +9 sounds good
Go to diystompboxes and search for treble boosters.
I posted a power transistor based one at diystompboxes

It is a simple voltage divider bias circuit that is biased more to cutoff than saturation if built like the originals
The input resistance is low but that is part of the sound caused by the loading of the guitar electroincs

Thanks for the tips Gus ,
I have some funny old mullard oc series Pnps somewhere , might try one of them .

I think the Rangemaster was pretty much just a fuzzface circuit with one more Ge tacked on...Much like the Tonebender etc...I've built a bunch of derivatives with scavenged Germaniums...fun to mess around with.

Med power Si transistors can sound good.
I built one with a TIP29

A thread from diystompboxes for Si NPN
https://www.diystompboxes.com/smfforum/index.php?topic=107047.msg970682#msg970682

There have been a lot of threads about Ge or Si transistor treble boosters

Have you found the GEOFEX writeup?

Gus said:

Med power Si transistors can sound good.
I built one with a TIP29

A thread from diystompboxes for Si NPN
https://www.diystompboxes.com/smfforum/index.php?topic=107047.msg970682#msg970682

There have been a lot of threads about Ge or Si transistor treble boosters

Have you found the GEOFEX writeup?

Click to expand...

Gus is on this. DIYStompboxes.com has more info about fuzzface/rangemaster/Vox tonebender transistors  than you’ll ever need. This has to be one of the most popular topics on that forum.

BT

Yes an excellent resource over in diystompbox,  those guys really have added some nice mods to it too , Seeing as I have some old Mullard pnps I might try starting with that . So many of the greats used the Dallas , I need some of that mojo going on .

I never had the right Germs to make a Fuzz Face sound right.  Then I build a Tone Bender  with 3 trannys in the 70 hfe range and had a ball playing thru the breadboard version.  I recorded so my hendrix like guitar motif's that day. 

I just came across a bunch of germ trannys that look to be in a good range. even some NPN's .  I hope to build a real good Fuzz Face this winter with some.  Just don't have time now to do anything.

Rangemasters are just single tranny treble boosters.  I too have thought of building a Tone bender, Range master, Fuzz face with a switch to choose the circuit of the stomp box.  Rangemasters are easy to build.  I haven't been real fond of them.  They seem to work best when you drive the hell out of an overdriven amp.  I can't take the volume anymore to do that.  A good FF or Tone bender can do that at softer volumes.

Greetings,

Another very good source of all stomp box info is Freeststompboxes.org. There is a huge thread on the Rangemaster here:

http://www.freestompboxes.org/viewtopic.php?t=562

Good luck, Jim

The rangemaster is nothing like the tone bender or fuzz face. They're just different circuits. The rangemaster is a simple single transistor boost with a small coupling cap to crush LF so you can cram more signal into your Laney Supergroup which doesn't have the smaller cathode bypass like the Plexi they're supposed to be a cheap copy of.

What makes a rangemaster sound the way it does? I can only speculate because I have never even seen a real one. But I can make a few observations about the circuit:

1) Because the emitter resistor is fully bypassed, the input impedance is going to be pretty low for guitar. I don't know what the emitter resistance of a Germ is but in a Silicon transistor it's ~25 ohms. That times beta gives you something like 2-5k. But that's actually not the whole story regarding input impedance because ...

2) The Vbe drop of a Germ is only 0.2V which means the input impedance is actually going to vary greatly as the Vbe junction is exercised. So it will be high when Vbe is back-biased (defined by bias resistors so ~68k) and low when Vbe is exceeded (because emitter resistor is fully bypassed, impedance is emitter resistance times beta so maybe 2k). Even moderate strumming is going to fully exercise the diode junction and cause asymmetric rectification and thus significant 2nd harmonic. Asymmetric rectification also means blocking distortion but because the coupling cap is so small, it may be not noticeable.

3) Because the emitter resistor is fully bypassed and collector resistor is relatively high, the gain is basically "open loop" which means it's going to run out of high frequency gain. Some Germs have limited bandwidth to start with so this is going to make a HF cut.

So you need a Germanium transistor (cannot be Silicon because of Vbe and BW limiting) and my guess would be that a really good one would have limited bandwidth maybe even down to 5-7kHz. You really need to cut the HF fizzle or it's definitely going to sound like crap. If I were making a rangemaster I would just breadboard it and look at the frequency spectrum as I vary the level going in from 0.1Vpp to 1Vpp and look for a HP corner of maybe 500-700 Hz and then try every Germanium transistor I have and look for one that limits the bandwidth the most (hopefully below 10kHz at least).

Nice analysis Squarewave.  There is also a resonance with the impedance of the pickup and that’s why it’s suppose to be connected straight to the pickup where the volume , on the guitar varies the impedance against the inductance of the pickup, or something like that .  But your test setup allows you to test germs for ball park. 

Thanks

A silicon power transistor can sound good in the treble boost circuit. I find I like to adjust the circuit biasing, don't get stuck setting the collector to 7VDC.

https://www.diystompboxes.com/smfforum/index.php?topic=107047.msg970682#msg970682

They are interesting conclusions Squarewave ,

So essentially your input impedence  changes with  level, Ive noticed if you try to drive lower impedence with pickups directly they do get a bit fizzly, start to distort ,and the tone changes .Maybe this was used to good effect in the rangemaster . I think the simpler unbuffered wah pedal seems to do the same thing . Eitherway wouldnt  that  cause extra loading on the peaks and bring  a kind of dynamic growl to the sound .

Maybe you could explain ,does the impedence either rise or fall as level increases in a positive or negative direction  and how does that situation change pnp vs npn . Does it work out that thats its the transistor clipping one half cycle and the low load on the other side of the waveform causeing distortion ?

Rangemaster seems to deliver a bit of harmonic bounce and sizzle  to the sound  closely related to how hard you hit  the note ,  ,backing off the volume control on the guitar cleans it all up nicely without it turning to mud ,then in the solo a small tweak of the volume control  with pinky finger and your gone from clean to scream to full on feedback ,and you have feet free for dancing , not stompin stomp boxes 

Tubetec said:

Does it work out that thats its the transistor clipping one half cycle and the low load on the other side of the waveform causeing distortion ?

Click to expand...

Yeah, basically. The guitar can easily overdrive that tiny 0.2V diode junction of the Germanium transistor. The emitter resistor is fully bypassed so the impedance at the base is going to be something like Hfe * emitter resistance = 100 * 25 = 2.5k maybe. But when the signal swings negative, the diode starts to conduct (remember this is PNP positive ground) and thus the impedance goes to almost zero (emitter fully bypassed). When the signal swings positive, the diode is reverse biased and impedance goes high (although limited by the 68K resistor). So a proper engineer would declare that this circuit is not well designed. It's as if it was designed to distort.