Leach Amp and its TO-5's

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Would it e possible to use these transistosr in place of the 2n3440/2n5415 .... aside from case differences would the circuit function?

Thanks for the radio shack tip, but ever since a bad bridge rectifier blew up a brand new mosfet amp i built i refuse to purchase any of there old substandard parts ;)
Type the part numbers into a Google search. Pretty amazing what pops up.

Jameco has both transistors for less than $1 each. Leach also recommended Ack Supply whose website also lists these transistors and gives the RCA SK replacement numbers as well.


You may want to look at 2SA1210 (pnp) and 2SC2912 (npn). These are in a TO-126 case and so may require some "cleverness" to twist leads to fit. These parts have a much higher beta and much lower Cob than the specified parts, so you will probably need to at least check the frequency compensation. I'ved used these in similar designs for years and they quite work well as voltage gain stages in power amps.

mlloyd1, that is a cool tip on the 2SA1210/2SC2912 pairs. I am seriously considering a design that uses the 2SD669/649 pair, and am looking at alternatives to get multi source availability.

I have some general questions regarding VA stages though, and I was hoping someone can shed some light on this. Is there any downside at all in using transistors in the VA (transimpedance) stage with high ? Is there such a thing as too much gain? Are the gains of the individual transistors that compose a cascode VA stage really important when driven in a Darlington configuration?

Thanks, and I wish everyone a happy new year.

Update : Please disregard the previous nte16/17 reference, if you managed to read it before I removed it :rolleyes:. I fogot to pay attention to the Ic and the Vce params, which are unsuitable for audio amp designs.
As far as datasheets, I beleive both the 2sa1210 / 2sc2912 as well as the 2sb649 / 2sd669 are made by Hitachi. Go here and search hitachi discrete transistors web site

As far as purchasing, any of the usual Japanese semiconductor houses (Dalbani, MCM, CEI, etc.) should stock them. You can also get them from Borbely Audio in Germany. That is actually where I got my first ones some years ago - as part of a Servo 50 MOSFET amp kit.


(aka mlloyd1)
I'm sorry, the link I posted doesn't seem to have all the info I thought it would. ALso, the 2SC2912/2SA1210 are made by Sanyo (the 2SB649/2SD669 are made by Hitachi). Some time in the next day I will post a link (maybe to my own website to make it easy) to the datasheets for all four devices in question.

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