NPN germanium recommendation for rangemaster? (Dallas)

[davepedals]

Hi,


What are some good not hard to find NPN germanium transistors for the rangemaster?  Wanting to do simple daisychainable 9v version.
Thanks for any help!

[tonyharker]

OC139
AC127
AC176

Any of these should work.

[davepedals]

Many thanks!

[mac]

That depends on how much highs do you want.
Leaky, easy to find ACxxx cut highs internally.
Bias resistors can handle some leakage, if not out of scale :-) . But high leakage could be a problem in the future, hiss, noise, etc.
Texas Inst 2N1114 or 2N388 are going to pass more highs.
Russians, I don't know.

Mine has a Matsushita 2SA102 PNP. It starts to cut highs above some Mhz.

You have more PNP options out there. Have you considered PNP, negative ground?

mac

[digi2t]

Russian GT404*. The * is the gain range letter, I can't remembered them by heart, so look it up. I think there's a thread that addresses this subject on the forum, including a translation chart for the Cyrillic characters. Whatever gain is stated for a particular range, deduct about 30% on average to get a more accurate number. I've used russian pnp and npn transistors with great results, but I've found that I generally have to go up one gain range letter to get transistors that fit the range I'm looking for.

[smallbearelec]

The OC139 that I have tested run a little low in gain for the RM. For the standard, one-transistor build, I like the OC140 better. I also have some old-stock "probably made by GE" devices that are relatively inexpensive because I found a mother-lode.

http://smallbear-electronics.mybigcommerce.com/transistor-the-rangemaster-npn-flat-hat/

The best buys, IMO, are low-gain/low-leakage types that can be wired as a Darlington pair and dropped into the RM. Properly biased, they deliver great tone and aren't expensive at all. If you have any low-gain PNP germanium lying around, the Sziklai Darlington RM is a great way to combine one of those with an NPN device. Please check out this article toward the end.

http://diy.smallbearelec.com/HowTos/BreadboardRMs/BreadboardRMs.htm

[davepedals]

Thanks for all the help!