Got hands on some new 2SD2390/2SB1560's, Gotta say they are very nice Darlington BJT's for power amps. But looking for potential do's and dont's. I have 7 pairs for my 7.1 amp project and plan to clock the surround channels at 100w. Sub amp still in the works with 3 pairs of 2SC5200's and 2SA1943's. Also would the 2SC4793 make a good VAS for a 450ish watt amp?
One pair of anything is a stretch for a single output pair to do 100 watts. You will have to dispense with any effective SOA protection and limit operation to 8 (not 6 and certainly not 4) ohms unless the power supply voltage is reduced to compensate. A lot of todays receivers have a 4/8 ohm switch that changes taps on the transformer. But it affects all channels.
That particular Sanken pair is nice. I just wouldn’t use singles beyond a 60 watt application. If you are going to be gentle with it, they will work. Just don’t short the speaker wire. If you put in a circuit that limits peak short circuit current to a safe 3A on a 50V supply, many loudspeakers will have it limiting all the time - at frequencies you really don’t want it to. Try it sometime and you’ll see what I mean. There won’t be any mistaking it when strong male vocals send you screaming from the room with your hands over your ears, Take the SOA protection out and it’s fine, until you brush the speaker wires up against one another with music playing.
The C4793 is more of a VAS transistor than a driver in high power applications. 100W (and larger) 4 ohm capable amps often use two in parallel as drivers, pro amps use them for VAS’s. The TTC011 is their current offering in TO-126, and is reportedly the same die as the C4793. Data sheet characteristics are spot on. I guess they realized you just can’t run them as hard as the old C3298 or it’s old non-encapsulated equivalent predecessor (I forget the # off the top of my head though). And put them in the more appropriate TO-126.
That particular Sanken pair is nice. I just wouldn’t use singles beyond a 60 watt application. If you are going to be gentle with it, they will work. Just don’t short the speaker wire. If you put in a circuit that limits peak short circuit current to a safe 3A on a 50V supply, many loudspeakers will have it limiting all the time - at frequencies you really don’t want it to. Try it sometime and you’ll see what I mean. There won’t be any mistaking it when strong male vocals send you screaming from the room with your hands over your ears, Take the SOA protection out and it’s fine, until you brush the speaker wires up against one another with music playing.
The C4793 is more of a VAS transistor than a driver in high power applications. 100W (and larger) 4 ohm capable amps often use two in parallel as drivers, pro amps use them for VAS’s. The TTC011 is their current offering in TO-126, and is reportedly the same die as the C4793. Data sheet characteristics are spot on. I guess they realized you just can’t run them as hard as the old C3298 or it’s old non-encapsulated equivalent predecessor (I forget the # off the top of my head though). And put them in the more appropriate TO-126.
Thanks for the feedback, Just realised I had mentioned the wrong transistor for the Subwoofers VAS, plan on using a 2SC2911 as the VAS then use the 2SC4793/2SA1837 as drivers. Heres the schematic for the main surround channels if you would like to have a look?
+/-45 rails really aren’t a stretch for those trannies - as long as you don’t go trying to drive dual woofer speakers (or subs) with them. But you will find that in the real world you will fall below 100 watts per channel, because you’d need 2 kVA or larger transformer for it not to droop below 40 at high load. Small signal transistors in the VAS are a little light. I’d run “small driver” types and either darlington or cascode the active NPN (With the C1845) if you want to get it’s intrinsic input capacitance down. Or find something in between that has about a 1 watt 25C ambient rating. Diodes, Inc (formerly Zetex) has some pretty nice stuff - and a very small TO-92 compatible package rated for a full watt. The lead frames are better at getting heat out than your typical 92 case.
As I said earlier C4793 is too light duty for 300W application. If that’s what you have, use two. They work fine paralleled.
As I said earlier C4793 is too light duty for 300W application. If that’s what you have, use two. They work fine paralleled.
I'd like to jump into this.
Is there any source of how to safely parallel these "good" Darlingtons? Simply tie the bases and collectors and give the emitters each own Re resistor?
There's a plenty amount of cheap AV-receivers with dead DSP/HDMI sections.
Most of the "better" receivers have two supply rails, one for 4Ohms and a higher one for >6Ohms, given they didn't save on the transformers higher rail current capacity, this would result in a pretty solid 2.x operation.
Sorry, I'm not into simulations.
Is there any source of how to safely parallel these "good" Darlingtons? Simply tie the bases and collectors and give the emitters each own Re resistor?
There's a plenty amount of cheap AV-receivers with dead DSP/HDMI sections.
Most of the "better" receivers have two supply rails, one for 4Ohms and a higher one for >6Ohms, given they didn't save on the transformers higher rail current capacity, this would result in a pretty solid 2.x operation.
Sorry, I'm not into simulations.