Rangemaster Variations

[davent]

Hello All,

A couple questions.

I'm setting out to build a copy of the Rangemaster and was wondering if there was any sonic differences to the various schemes that are out there? I'm looking at the two GGG schematics with a PNP tranny, positive or negative ground, I've got the Geo document and Tonepads document both using PNP's and I've got Doug Hammond's NPN schematic.

I don't have a suitable transistor of either type so will be ordering a few of what I need from Small Bear, any that are highly recommended?

Also is there any reason to not use permanently mounted trimpots on the board to set the bias of the transistor?

Thanks in advance for any opinions/suggestions. 

Take care
dave

[brefmint]

I built one with the positve ground GGG board. I ordered an OC44 from Small Bear. http://www.smallbearelec.com/Detail.bok?no=273
As far as I know there aren't any "tone" differences between positive and negative ground. Negative ground just makes it safer to chain with other pedals if using a chained power adapter. In my opinion these pedals do sound better when running on non-alkaline batteries though. I didn't even install a power jack on mine. I've had the same 99 cent battery in mine for months. This pedal sounded great from the start. I had no need for trimpots.
Good luck!
Matthew   

[petemoore]

  NPN Neg. Gnd
  PNP Pos Gnd.
  Work when wired right, recommended.
  PNP neg Gnd. may work.

[Krinor]

I just built a PNP version on the GGG board. At first I put an NOS american germanium transistor in it, but changed it to an OC44 when I discovered that Smallbear sells them. Not sure if these latter are the real deal though. Anyone know anything about this ? I had to change one resistor to get the bias right. Mine sounded a lot better after I installed the OC44 in it. The first one ( Etco(?) 2N1305) sounded too sharp and piercing to my european ears. If you buy the transistors from Smallbear I really can't see any reason to put a trimpot in the pedal as the transistors come tested with a little note attached where the values for R3 and R5 is written. However if you plan to change your transistors from time to time the trimpot is probably not a bad idea..?

[davent]

Hi Guys,

Thanks for your insights. I've ordered a couple transistors from Small Bear, including an OC44 to try out in my build. Being one who always takes the road less travelled I'm going to attempt the PNP negative ground version first.

Take care
dave

[R.G.]

Being one who always takes the road less travelled I'm going to attempt the PNP negative ground version first.

Sure. Go for it.

But remember if it doesn't work, the cure is changing it to positive ground.

[DougH]

It's such a simple circuit. Breadboard it and experiment with bias and (esp input HPF/Zin) tuning before committing to it. As long as your transistor is not horribly leaky, you can predict the bias point with Ohm's law. In other words- no need for trimmers...

[Dragonfly]

It's such a simple circuit. Breadboard it and experiment with bias and (esp input HPF/Zin) tuning before committing to it. As long as your transistor is not horribly leaky, you can predict the bias point with Ohm's law. In other words- no need for trimmers...

Doug is absoltely correct on this...

But i'll add one thing....

I WOULD recommend setting the "bias" by ear, not just automatically "defaulting" to the 7.2V that some people recommend...I like them biased in the 6v-6.2v range, and I know Doug likes them biased lower than recommended as well....find where YOU like it.

the breadboard is your friend

[newfish]

So - all stocked up on Germaniums (PNP) ready to make Rangemaster.

With Biasing being such an important part of the circuit, would it make sense to have an adjustable bias?

Maybe using a minimum resistor in series with a small pot (maybe 4k7) to 7.5v with the pot at minimum (for example, I've not done the sums yet...)  and dropping to 6v or lower at maximum?

Any thoughts guys?

Oh - and if anyone is after any obscure ICs, I'll post a list of ones I recently came across - including 16k DRAMs for anyone interested in delay / looper fun.

Cheers,

Ian.

[davent]

It's such a simple circuit. Breadboard it and experiment with bias and (esp input HPF/Zin) tuning before committing to it. As long as your transistor is not horribly leaky, you can predict the bias point with Ohm's law. In other words- no need for trimmers...

but need the

Sounds like fun!

I'll tweak it on the breadboard until my ears are content then box it up for real. I'm planning on putting two coupling caps on a switch to give it a variation in voicing along with playing with the resistor values to get it to the sweet spot. Waiting for parts so i can check the spacing on the PCB I've layed out, then can get down to business . (Doug, it was link Zaphod put up, on some forum somewhere,  to your build and hearing it that got me going on this little project.)

Thanks to all
dave

[davent]

Hi All,

Thanks for the suggestions. Finished up the build on the weekend. Ended up with a PNP negative ground copy using a NOS Japanese transistor from SmallBear. Also got an OC44 but at this point liked the other tranny better. Put in a switchable pair of input caps that sounded good on the breadboard but now that i can switch easily between them there really isn't that much sonic difference between them so I'm going to play around with that further.

On the breadboard I had some hiss when the guitar volume was rolled off but now that it's boxed up the hiss is gone. I socketed all the resistors and tranny so i can mess with the bias and keep playing around with different transistors i aquire. Put a 1M resistor across the input jack and a 2M2 across the output jack and get no pop when bypassing/engaging.

Pretty pleased with the way it sounds. Still playing around with it and my amp to see just what the two can do together but so far very cool !!! 










Next up I've got the parts to breadboard an Omega Booster which I've been reading good things about. The fun starts again!

Thanks for sharing everyone!!!

Take care
dave
<

[the_random_hero]

Wow, that looks amazing. A ridiculous amount neater than inside my pedal housings 

[petemoore]

  I once put two pots on the collector, first as VC and ~<10k, second as a +/- 10k bias adjust, IIRC I could adjust bias between something like 8k2 and 14k..
  Another has bias all set up, then a volume control tacked on the end like anything...not really an RM at that point.

[DougH]

Nice work!

[mac]

Isn't it cute? 



mac

[stopstopsmile]

Is there any companies making high gain high HFE germanium transistors?  Modern stock? 

[John Lyons]

Nice looking build there davent.
Did the color and the rounded board corners and pot mounting.
What type of paint is that?
Points for the inner-tube battery cover as well!

John

[davent]

Thanks Guys,

Nice looking build there davent.
Did the color and the rounded board corners and pot mounting.
What type of paint is that?
Points for the inner-tube battery cover as well!

John

John the green is Createx Airbrush Colors Pearl Lime, comes in little 2oz. bottles and maybe took a quarter of a bottle to paint the box.  The white is AutoAir Colors Base White which is also the undercoat for the green. Topped that with rattle can lacquer until I could  sand and polish to glass smooth then Laserjet waterslide decal for the label. Then another six - ten coats of lacquer to get the edges of the decal to dissappear. Lots of sanding with 400-1200 wet papers to get a smooth finish then one last coat of lacquer. Not sure how durable it will be  but time will tell.

Still trying to find a good primer for the aluminum boxes. For this one i've tried AutoAir Colors Direct to Metal Primer.

I've used up my plain Hammond boxes so next I'm going to try painting over some of SmallBear's powder coated boxes and see how well the paint sticks to them.

Confession on the innertube, not enough space down there, I couldn't get the back cover on tight when the tube was in place so had to remove it to get the back to seat properly. I've used the inner tubes in other builds no problems but this was  an old box from another build and I'd cut things too close. Need to grind away some of the jacks' insulation to move the battery forward.

Got the pot from SmallBear and really like how that worked out, be using those again, anything to avoid messing with wires is a bonus and solves my other problem of trying to figure out how to mount the board in the box.

Thanks for the interest and take care all,
dave

[John Lyons]

Ha! I should have known. Not much substitute for a lot of work to get a nice finish.
Looks great.
Try self etching primer if you can find some cheap. It bonds well to aluminum.

Thanks for the information.

[davent]

Not really a lot of work, more a case of hurry up and wait. Spray for a few seconds to coat, then wait for it to cure so you can go on to the next step.  The lacquer season is over here so I'll have to wait 'til spring and it warming up to get back to finishing.


John, very cool website!!!  Now about those wooden enclosures, they'd take a ton of work to produce. Beautiful work Are they bandsaw boxes or do you piece them together?

See ya,
dave