lhquam. During his tenure at Threshold Corporation, Mr. Pass used 2N3440 [NPN] and its complementary 2N5415 [TO-5 packages] as drivers to STASIS output stages which operated at +/-50V PSU.
I mostly trust to manufacturers datasheets, but in my experience BC639/640 are noticeably sturdier pair than BC550/560 - I use BC639/640 produced by Philips (0.83W declared).
There's nothing wrong with BC550/560 too, if you make an effort to cool them a bit, in interest of long-term reliability .
Of course, you can experiment with other BJT types - I'm sure there are a lot of good BJTs with adequate Pd, hfe, BW...
I'd like to build version with k246/j103. I'd like to know the following:
1. Does both R9 and R24 are required?
2. How big heatsinks is recommened for 78/79xx and mosfets?
3. Is it good enough to use one power supply or one per channel is recommended here (not to say obligatory)?
4. I put C6 as film instead of elco. It that ok?
Many thanks.
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1. Yes if you keep C7 between them because Jfet's gate needs a firm DC reference
2. I didn't use them, but if you think you need them, something like this will be OK
3. One for both channels is fine, but if you are willing to try, one per channel might be marginally better
4. OK
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Oops, my fault! Many thanks Juma for this and previous post. New schematic is in attachment.
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Sorry for the OT Juma
Did you try this pre together with your K2013/J313 based F5?
Yes, it's my current setup and I enjoy it very much. Few days ago a friend came to visit and his comment was: "it sounds expensive" ...
Huh, "copy&paste" error. Here is new schematic with two channel and single PS. First version of PCB single layer (no jumpers required) if finished. If this layout is correct I can also make version with single channel if someone find that interesting.
Maybe everything is too small and I put very small heatsink on 78/79 to spare some space.
Thanks in advance for comments and suggestions.
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Thanks buzzforb. I'll further modify this one to be capable of accepting additional RC (R14, C3 from post #66) and possibly increase PS section to host bigger heatsinks as Juma suggested.
Absolutely, but to be honest, most of my builds can be categorized as the turtle type.
My work require me to frequently be out of town for extended period, was out of town mid of november to end of december. When I got home, I have to remind myself that I am a grandpa already and have to do this patiently and carefully (for me, patience supply is getting leaner with age, lost a 2sk79 last week when I was chasing a barely audible hum on a Baby AKSA amp style - 2sj74gr diff input, 2sk79 vas, darlington out - the second project that started on august after a 25 yr hiatus, had to revert back to 2sc2271 for the vas, and still no joy on the hum)
Just completed collecting required parts this week (still needs apropriate heatsink though), but will be out of town beginning next week. Again. Can still post messages and drool over the forum, but no hot iron. Like I said on post #137, I simply don't have the time I want for this hobby, but I savor whatever time I get and enjoy this fantastic journey as the scenes unfolds.