Rangemaster

[enigmur]

I was thinking I'd build the Rangemaster from Dragonfly's vero when I get home today

Just a quick question - approx what Hfe should I look for in a Ge Trannie?

For people who have built this, what do you all think? Could I easily add a tone control and use it as a drive aswell as a boost?

[enigmur]

I built this circuit last night - http://aronnelson.com/gallery/album143/DALLAS_RANGEMASTER_001

If I swap the 68K Resistor in front of the Base of the transistor going to ground for a 100K Trim, will this let me dial in the voltage for the transistor Bias? Would I just use 2 legs of the trimmer?

I only have a 100k pot, can I just run a 90k resistor from lug 1-3, and it will leave me with a 10k??

Cheers!

[Krinor]

Hi,

I actually built this exact same circuit last night too! 
It works wonderfully just the way it is. I didn't bother to bias. I used the suggested components.
I tried different germanium transistors. First an AC126 which I found to be way over the top when it comes to gain. It sounded really dirty. The one I eventually left in there was an OC75 which sounds a bit mellow and very, very vintage.  It's got just the right blend of warm boost and a little bit of grit at the end. I tried OC45's too, but they seem to be extremely low gain (?)
I have built an LPB1 replica and another LPB1 which I have modified to become a treble booster (with 0.01uF caps.) The last sounds great when put in chain with the Rangemaster at the end. I also tried to chain all three boosters and this provided an extremely distorted signal.

[Krinor]

Oh and for biasing the Rangemaster don't miss the article at Geofex:

http://www.geofex.com/Article_Folders/Rangemaster/atboost.pdf

(I hope it's okay to put links in here ?)

[ambulancevoice]

I tried OC45's too, but they seem to be extremely low gain (?)

[enigmur]

I finished and housed this last night.

It was a bit bright on the clean channel so I upped the input cap to .01uf and it sounds a bit better.

Im using a ge transistor at around 80hfe, it does crunch nicely!.

One question - I am using a 100kB pot, i figured putting a resistor across the outer tabs would work as stated in a thread I read yesterday. For some reason, when I put a 91K resistor across the tabs, at full turn, I only get 47K resistance  -each way...
So the knob is only in function for about 30%... Any idea why the readings I got were weird? I thought that should turn the pot into 9K?

The pedal is quite noisey, it adds quite a lot of hum, especially if used on a dirty channel, but I read that is quite normal, and I can cope with it.

I'll see how it performs at band practise tonight, I may just house my NPN boost in that enclosure and leave the Rangemaster in the finished circuits pile if it isnt what I'm after - I'll build an OD.

[Hanglow]

One question - I am using a 100kB pot, i figured putting a resistor across the outer tabs would work as stated in a thread I read yesterday. For some reason, when I put a 91K resistor across the tabs, at full turn, I only get 47K resistance  -each way...
So the knob is only in function for about 30%... Any idea why the readings I got were weird? I thought that should turn the pot into 9K?

Does this not mean that it is a 100k and a 91k in parallel? Which would give you the 47k....if you put a 10k across the tabs you will get a 9k (I think)

I built a keeley Java Boost today, which is just a rangemaster with selectable input caps and a bog standard tone control, its a nice pedal. First treble booster I've built, and it works surprisingly well with my SS carlsbro amp, which I didn't think it would. Having the selectable input caps is a bonus I think, it makes it more versatile certainly. The tone control isn't realy needed imho though.

[petemoore]

if you put a 10k across the tabs you will get a 9k (I think)
  The 10k pot is a volume pot, and it's wafer connections [lugs 1 and 3] serve as ~10k bias resistor for the collector.
  IIRC  used 87k parallel 12k to make ~10k bias pot with use of 100k pot [which measures 87k.
  parallel resistances are easy to measure.

[enigmur]

So how would I wire this up? I'm a little confuzzled...

[petemoore]

  Verifying were talkinga about a pot between collector and V...power supply.
  On the schematic this is shown as 10k.
  Normally a volume control [like dist + volume wiring] can be..whatever value.
  But in the case of the rangemaster, the wafer of the pot is the bias resistor for the transistor collector, 10k [or probably a measured 8k7 or so], if you use a 100k pot, the resistance between lugs 1 and 3 [across the wafer] is 10x bigger than the value shown...certain to throw bias off.
  Usinga 12k resistor in parallel with the potwafer, [connect the 12k fixed resistor across lugs 1 and 3] this should drop the resistance between collector and supply rail to about 10k.
  If you have a 100k pot handy, or use the one in the circuit, put a 12k across lugs 1 and 3, measure the resistance, then try 15k or whatever until you get somehing like 10k there, 8k2 should suffice, 100k is well out of bias parameter for RM.

[enigmur]

I tried a 10K across the pot and it put it in range perfectly, except for some reason I was getting massive volume control between 1-2 and nothing else from 3-10.

My 10k pots arrived yesterday from back-order and I tried one in. Also I found I was using a 160hfe transistor, so I swapped it for an 80hfe.

It sounds perfect now, at 10 it has a nice amount of grit, but it is a much smoother boost. Sounds great for lead or solos where you need a volume kick and to cut thru the sound.