Well, not any more. 2N3055 is still useful if you want 30-50W of power. TBH i probably wouldnt even use them as PSU pass transistors now - the die is small which limits its heat dissipation, and the more advanced devices are now minimal extra cost.
Maplin used to do a 2n3055/mj2955 based amplifier in the 1980's.
It used a pair of each on the output.
It was 225WRMS into 4 ohms.
I used one on my disco for years and it was very loud and reliable.
I wouldnt use 2n3055's in designs now as there are many much more newer and powerful transistors available now.
It used a pair of each on the output.
It was 225WRMS into 4 ohms.
I used one on my disco for years and it was very loud and reliable.
I wouldnt use 2n3055's in designs now as there are many much more newer and powerful transistors available now.
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Hello
Here is a high power 2N3055 amp that I've done last year for a friend and that was revised by few diyaudio guys, it's use the output transistors in serial/parallel, so it can hold the 60 volt rails. The thd spectrum are low and with mostly 2nd and 3rd harmonics.
Bye
Gaétan
Here is a high power 2N3055 amp that I've done last year for a friend and that was revised by few diyaudio guys, it's use the output transistors in serial/parallel, so it can hold the 60 volt rails. The thd spectrum are low and with mostly 2nd and 3rd harmonics.
Bye
Gaétan
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Hi all
Still some bad press about the 2N3055? I used RCA devices in my first amp. Weren't bad, but then I heard the quality of epi devices (2N3716/2N3792). Had to admit the RCA devices were no longer the best for audio. Never used them since - and although obsolete, Magnatec devices appear to stick to the original (RCA - "H") spec.
But the current generation are epi and considerably faster than the old RCA. THey give a better sound as a result. THe latest version from ON Semi has a better SOA too- 60V at just under 1A, so you could use this in a linear PSU, or still any type at lower voltages (<40V).
ALthough they are rated at 100V Vcbo they only need a small current to change from "Vcbo" to "Vceo" - and bang. I would not run 2N3055/MJ2955 (and there is a howler in the circuit diagram- the 2N2955 is NOT a power transistor at all - it was a PNP, 25V, germanium TO-18 transistor) at over +/-40V rails max, but you might get away with +/-45V rails if you check your devices first.
+/-55V is far too high so this amp circuit is nonsense.
Could use 4 ohms on 40V rails with a pair or three as Maplin did for high powers.
John
Still some bad press about the 2N3055? I used RCA devices in my first amp. Weren't bad, but then I heard the quality of epi devices (2N3716/2N3792). Had to admit the RCA devices were no longer the best for audio. Never used them since - and although obsolete, Magnatec devices appear to stick to the original (RCA - "H") spec.
But the current generation are epi and considerably faster than the old RCA. THey give a better sound as a result. THe latest version from ON Semi has a better SOA too- 60V at just under 1A, so you could use this in a linear PSU, or still any type at lower voltages (<40V).
ALthough they are rated at 100V Vcbo they only need a small current to change from "Vcbo" to "Vceo" - and bang. I would not run 2N3055/MJ2955 (and there is a howler in the circuit diagram- the 2N2955 is NOT a power transistor at all - it was a PNP, 25V, germanium TO-18 transistor) at over +/-40V rails max, but you might get away with +/-45V rails if you check your devices first.
+/-55V is far too high so this amp circuit is nonsense.
Could use 4 ohms on 40V rails with a pair or three as Maplin did for high powers.
John
I have had the idea for a long time that if you take an opamp and a 2N3055 or what ever power transistor you should be able to make a power amp out of one dual opamp and two power transistors.
It wasn't until recently that I have figured how amps actualy work but that is my own deliema.
I see no reason why it should not work.
I have been using that transistor for years and there are better ones,
but because it is still so available it is hard not to think about coming up with some better design using it. jer
It wasn't until recently that I have figured how amps actualy work but that is my own deliema.
I see no reason why it should not work.
I have been using that transistor for years and there are better ones,
but because it is still so available it is hard not to think about coming up with some better design using it. jer
3055's were very successfully used in many classic lower powered hi fi amps such as Leak Stereo 70, A & R Cambridge A60 and NAD 3020 amongst many others. In totem pole they formed the basis of many a higher powered PA amp back in the day. I can't see any point in using them in a modern design though when there are so many much better types available today. They are probably THE most legendary power transistor though 
about3055's were very successfully used in many classic lower powered hi fi amps such as Leak Stereo 70, A & R Cambridge A60 and NAD 3020 amongst many others. In totem pole they formed the basis of many a higher powered PA amp back in the day. I can't see any point in using them in a modern design though when there are so many much better types available today. They are probably THE most legendary power transistor though
http://www.diyaudio.com/forums/soli...i-complementary-power-output.html#post2026127
there are a lot of models listed, partly with schematics
MJ2955/2N3055 as driver stage I have never seen before. What happens with the pre-driver AC signal by full output power?
Hi all,
Thanks for fantastic response always good to hear all of your comments. But what mystify's me is the Collector to Emitter argument that it won't handle the voltage. Most 2n3055 datasheets will handle at least 60 volts between there collector and emitter the rails in the schematic i put up are 55 +- between ground that means that the collector emitter will not be getting more than what it should so where does this the amp can only have rails of 35 to 42 come from. Unless the data sheets lie. the full +- rail does not sit across the output transistor. So i don't see voltage rails as the problem in that regard. I think where a lot of amps fail in my experience is in cooling. I've come up to some 2n3055 amps at the back where the heat sink is and you could cook a egg on them. I couldn't imagine that would be doing them much good. I had a look at 2n3055 inside comercial famous amps not many schematics plus not many powerful 2n3055 schematics as in you want some grunt out of these suckers as there generally used for either a bass amp or some sort of bang for buck pa application. People generally don't use cheap transistors in hi fidelity amplifiers. I know i wouldn't build a bang for buck amp for my lounge room. But for pa a bass amplifier perfect loud and cheap.
Thanks for fantastic response always good to hear all of your comments. But what mystify's me is the Collector to Emitter argument that it won't handle the voltage. Most 2n3055 datasheets will handle at least 60 volts between there collector and emitter the rails in the schematic i put up are 55 +- between ground that means that the collector emitter will not be getting more than what it should so where does this the amp can only have rails of 35 to 42 come from. Unless the data sheets lie. the full +- rail does not sit across the output transistor. So i don't see voltage rails as the problem in that regard. I think where a lot of amps fail in my experience is in cooling. I've come up to some 2n3055 amps at the back where the heat sink is and you could cook a egg on them. I couldn't imagine that would be doing them much good. I had a look at 2n3055 inside comercial famous amps not many schematics plus not many powerful 2n3055 schematics as in you want some grunt out of these suckers as there generally used for either a bass amp or some sort of bang for buck pa application. People generally don't use cheap transistors in hi fidelity amplifiers. I know i wouldn't build a bang for buck amp for my lounge room. But for pa a bass amplifier perfect loud and cheap.
When the output swings to each of the rails under full power signal conditions the off transistor sees nearly the rail to rail supply voltage. There are much better choices for most of the semis in this amp - they were chosen way back when there were not many
devices to choose from. If you really want to use older style devices 2N3773 is what you should use for outputs, bigger die, much higher Vce, better beta.
It is also very odd to be using BD140 devices in the diff pair and the TIP device in the VAS.
I expect that the 2N2955 will fail.
I don't suggest building this, but if you really want to, use 2n5401 for the diff pair, and MJE15032/33 for drivers.
Find something better for the VAS.
devices to choose from. If you really want to use older style devices 2N3773 is what you should use for outputs, bigger die, much higher Vce, better beta.
It is also very odd to be using BD140 devices in the diff pair and the TIP device in the VAS.
I expect that the 2N2955 will fail.
I don't suggest building this, but if you really want to, use 2n5401 for the diff pair, and MJE15032/33 for drivers.
Find something better for the VAS.
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Your in the USA. Mother mouser has MODERN njw0281/0302's for under $2/25 , ($2.31 apiece) why would you bother with ancient history ? 4pair-250w = a $16-$18 Op stage @ 250Vce - 30mhz Ft.
OS
Iam fully aware there are better semiconductor devices out there. In fact some would wonder why you would even bother building a bjt based amp anymore. But this is not about better semiconductor transistors its about just using up old supplies in a junk box and making use of them. I KNOW YOU CAN GET BETTER. The thing is they are readilly available and most guys can put a amp together for next to nothing that they basically don't care to much about and use in situation where the care factor is next to nothing. Sometimes at a party you don't want to be sitting there worrying about your role royce amplifier. Does anyone have the Maplin 225 watt schematic that i keep hearing about i can't find it anywhere thanks.
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