Author Topic: SF.T 306 transistor for Dallas range master?  (Read 760 times)

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SF.T 306 transistor for Dallas range master?
« on: December 30, 2016, 10:27:37 PM »

I think the sf.t306 (NOS BULGERIA) is like oc44.  Any good in this pedal?
Vcb: 18.  Vce: 15.  Leakage Icbo: ioau.  Vcb: 15v. Gain: 40. Pwr: .150 W


Re: SF.T 306 transistor for Dallas range master?
« Reply #1 on: December 30, 2016, 10:59:24 PM »
I would think that hfe 40 is too low for a range master. I usually aim for 90110.  I have some of those SFT306 and a handful of OC44. While they might have some similar characteristics on paper I wouldn't make any comparison between them when actually used in an audio circuit.  The SFT306 that I have are bright and noisy while the OC44 tend to be less noisy and darker (in terms of frequency response). That may not make much difference in the range master. In my experience the RM doesn't seem to be too fussy about the transistor type. I have made great sounding range masters with 2SBxxx, 2Nxxx and even those cheap AC125 that are still so plentiful. All good. Give that SFT a go. In the worst case you can swap it for something else.

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Re: SF.T 306 transistor for Dallas range master?
« Reply #2 on: December 30, 2016, 11:39:17 PM »
I thought 40 may be too low but wasn't sure.  Haven't got the trans yet so I think I'll opt for the modern version range master.  Just heard a clip, it's nice and I have a bunch of bs170 & 2n5457 on the way. I'll build the original eventually, thanks!


Re: SF.T 306 transistor for Dallas range master?
« Reply #3 on: December 31, 2016, 12:17:58 AM »
If you have some PNP germanium in the 40s and want to make them a little "hotter" for an RM, try setting up a Sziklai Darlington pair. Notes are at the end of this article.

You may have suitable low-gain devices for Q1 in your spares drawer; if not I have lots of possibilities and they are not expensive:


Re: SF.T 306 transistor for Dallas range master?
« Reply #4 on: January 03, 2017, 12:10:57 AM »
I found imho that anything between 60-90hfe with low leakage is fine. I have had great success using 2n1302 and 2n1304 texas instruments NPN germanium. I have made 20 rangemasters and different variations of transistors. . I like the npn they seem to be better to me. Everyone has cherry picked the pnp transistors  The best part is you can use negative ground so no need for charge pump or special supply or battery only.there will be subtle differences but i think thats more on the leakage and hfe and bias. check out the Geofex technology of the rangemaster . its important to get the bias right with the 3.9k and 68k resistor. I like to bias around 6.9v    . i make almost all my fuzz and rangemasters with npn now i bought several hundred a while back. the 2n1306 is a little hotter  80-130 hfe. Great for fuzz faces and works out pretty good with the npn they are rare but i have found much better specs compared to all the other pnp that are left these daYS.

with the exception of the fine folks at smallbear. if your only building one or two get a good oc44 from smallbear he will give you the right resistors for the bias. you cant go wrong.i did that for my first one then scored a ton of the 2n1302 and 2n1304 transistors locally and unless i sell 300 pedals im set for life.These sound as good as any of them they have low low leakage . now for tonebenders sometimessome  leakage isnt a bad thing for Q2
« Last Edit: January 03, 2017, 12:17:13 AM by strassercaster »


Re: SF.T 306 transistor for Dallas range master?
« Reply #5 on: May 15, 2017, 02:21:16 PM »
I have roughly 150 of these sft 306 and the hfe in mine go from 55-175 most are around 80. I've used them in alotta different things and they are vastly different from the other Soviet era germanium transistors I have accumulated. The leakage is usually too low to worry with but they are really bright in the upper mids area. I like these in fuzz faces and as q1 and q2 in fz1 and tonebenders. But take all of this with a grain of salt bc ymmv with the eastern bloc stuff. Never had a bad batch of anything from Bulgaria or Russia. Get out a breadboard, and plug and play until it sings, is the best advice I have ever received. Biasing shouldn't be too big a concern

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Re: SF.T 306 transistor for Dallas range master?
« Reply #6 on: May 15, 2017, 03:58:51 PM »
one of my best RM's was a darlginton pair using small bears tutorial.  You can make your Hfe anything value you want this way or get a certain tone by mixing and matching the two bjts. Mine ended up with two old hitachis from a 10 transistor vintage radio i pulled apart. I also got a .015 big round mojo looking tone cap out of the radio too  ;D