The Generation V RangeMaster will still use the 1967 original circuit design - meaning that it uses PNP Germanium transistors, is positive ground, and has certain "peculiarities", which you can read about below, if you are interested.
What has been changed in Gen V are the following:
The PNP Germanium transistors are an OC76, an OC44, and an AC125. This gives a broad range of behavior from the RangeMaster, and coupled with the Frequency Cutoff Selector, offers a huge tonal variation; everything from a duplicate of the original 1967 RangeMaster, to a raucous, distorted and compressed screamer for when you are feeling particularly nasty.
I have modeled Gen V extensively with SPICE, and the prototype was complete in January. No doubt there will be some fine tuning of the circuit, but after that I will build 6 production units, available March 1st, 2018.
The Gen V RangeMasters will sell for $110. Check back here for availability, or to be placed on the list to reserve your RangeMaster. If you are on the wait list, I will e-mail you as soon as your unit is ready to ship. (There is no obligation to purchase the unit if you change your mind and don't want it.)
Generation V RangeMasters are being made as we speak.
Series III RangeMasters are sold out.
The series III of the RangeMaster (in photo) are the small enclosure, similar to the original. There are 8 units in this series, of which 4 are spoken for. (Just e-mail me if you want to reserve one.)
I am making these with CV 7003s, which are the UK military OC44 designation. To me, they sound identical to the Mullards, but are available in high Hfe ratings (100 or higher), which I can no longer find in the Mullards. Plus, they don't cost a million dollars.
Series III pricing is $75 plus shipping - still vastly less expensive than other reproductions which sell for $300
The thing about the legendary RANGEMASTER treble booster
is that once people start using it, they find it hard to play without it.
Now, I'm not saying the Rangemaster is addictive and dangerous
to experiment with, but, no, wait...that is what I'm saying.
The Germanium transistor is highly unreliable, extremely temperature sensitive, unstable, leaky, prone to hum and hiss, and fails short if you look at it funny. It's no wonder it was replaced as soon as possible by silicon.
The peculiarly endearing potentiometer in the original Dallas Rangemaster was a UK Welwyn 10k ohm (sometimes 20k) unit with two mounting screws instead of the ubiquitous hex nut over the shaft arrangement of USA pots from that era.
The Rangemaster's primitive (and incorrect) G-Clef with a little arpeggio (in the key of Asia Minor) let the unfamiliar know that this device had something to do with music. The not-overly-complex Rangmaster had two controls: an on-off switch and a boost knob. The boost knob was quite noisy due to the DC voltage present on the Welwyn, so you were clearly supposed to set the boost where you liked it, and then NEVER TOUCH IT AGAIN. …unless you like the sound of frying bacon.
The Welwyn pot was cleverly isolated from the chassis of whatever
it was mounted on; the potentiometer body was Bakelite or other
thermoset, and the plastic knurled knob was non-conductive.
Not that this isolation was necessary for the Rangemaster's low-
voltage, low-current signal, but it was distinctive and made the
Rangemaster that much more novel.
There are a plethora of Rangemaster clones and near-clones and replicas and reproductions and tributes out there, but none of them employ a genuine isolated Welwyn potentiometer. Until now. Because we do it the HardWay!
Does the Welwyn potentiometer make a difference in the sound? Of course it does! It makes as much difference as cloth-covered wire versus plastic insulated wire. It makes as at least as much difference in the tone as does a vintage capacitor compared to a new high-quality capacitor of identical capacitance and leakage. Ahem.
Germanium, from Germania
The highly regarded OC44 germanium transistor was just barely serviceable. A friend who worked for a manufacturer in the 60s told me that they had to do 100% testing of all the germanium transistors because as many as 50% of them didn’t work when they were brand new. A lot of them would fail as soon as you tried to use them. To this day, you have to sort through hundreds of Mullard OC44s to find a handful that are just right.
[ A side note for you do-it-yourselfers: There are a lot of OC44s for sale
on eBay and elsewhere. I have tried buying a lot of these and have usually
been disappointed. Some of them are dead on arrival, some have abysmal
hfe (20 !) some have spectacular leakage, and some are not OC44s at all,
but SFT307s painted black (true). A good seller will tell you the leakage
and the real hfe (not just the apparent hfe, which includes leakage) of each
OC44, or he will be happy to find it out for you. If the seller says the
transistors are “untested” you should assume that they have, in fact, been
tested, and been found wanting at some point in their history.
I’m not saying that these sellers are unscrupulous, I’m just saying they seem unscrupulous.]
The OC44 germanium transistor does have some interesting compression and distortion characteristics when biased properly. Electrical engineers have long designed clever biasing circuits which ignored the range of hfe (amplification factor) of transistors; especially these transistors. So if an OC44 fanboy tells you that his OC44 has an hfe of 175, and that it would be totally awesome in a Rangemaster, you can point out that any OC44 hfe between about 35 and 200 would be equally awesome in the Rangemaster circuit, due to the modulating effect of the bias circuit design.
Leaky, as in "they are all leaky"
Since high leakage can mask true hfe, and since all OC44s are leaky,
unless you measure leakage of transistors separately from hfe, you will
never really know the true amplification factor of your OC44, anyway.
Here is an article by R.G. Keen about germanium transistors for the FuzzFace;
a bit down the page is a method for measuring leakage and hfe, and a schematic
for a true hfe measuring circuit you can build in about 10 minutes on a breadboard.
Regardless, the trick to the Rangmaster circuit is the bias circuit.
The best Rangmasters are biased to about the middle of their range.
In this way you get nice compression-like effect as well as pleasing
distortion and attack sensitive response from the Rangemaster.
Biased improperly, the Rangemaster just sounds like a treble booster, which still ain’t bad, by the way.
The HardWay RangeMaster is a precise reproduction of the original. It is hand-made and each one is custom biased for each individual OC44.
The RangeMaster is not a stomp box. If you stomp on it, bad things will surely occur.
It sits on top of your amplifier. You plug your guitar into it, and you plug the RangeMaster into your amp. Extensive testing has shown that, like the original, the RangeMaster does not work and play well with others; If you have a big effects chain, and a colorful array of stomp boxes, and a high-tech effects loop in your amp, this is probably not the effect for you – check eBay for “OC44 stomp box AWESOME!!!”.
The RangeMaster uses a 9V battery, replaceable by removing the 4 screws on the case and lifting the lid. Similar to the Fuzz Face circuit, the Rangemaster is sensitve to temperature changes and battery voltage. I'm sure you have heard the story that Stevie Ray Vaughn used to use only used 9V batteries in his Fuzz Face, because he liked the tone he got from a lower voltage battery.
Each OC44 in each RangeMaster is biased at a battery voltage of 8.2 VDC. This is about mid-way between a new battery and a dead battery, and insures that you will get optimum performance of your RangeMaster throughout the life of the 9V battery. A 9V “wall wart” supply is not an option, and not recommended.
As with the original, the boost control will make scratchy noises as it is turned; this is due to a DC voltage present on the pot. If you want a silent adjustment, check eBay under “OC44 stomp box AWESOME!!!”.
I will warn you in advance of two things of which I am certain:
1. This device is addictive – you may find it difficult to turn off.
2. Eric Clapton did not use a Rangemaster on the Beano album.
I built this RangeMaster with a socket mount for the OC44
so that it is easy to replace or change. This is the last one
for a while because I can't find any more Welwyn pre-sets.
They are getting extremely rare. -Rarer than OC44s!
This last one is for sale on eBay (SOLD). It is bias adjusted for
this particular OC44 to be in the middle of its range.
The effect is excellent. I tested it through a little Harmony
H303a amplifier and the results were dramatic.
Smooth, liquid distortion, superb treble boost and
good compression and sensitivity.