Before someone calls me out, at 6:50, the emitters of the differential pair transistors are near 0v (~.7v) with a normally functioning amp. When the prototype amplifier had full +rail on the output, there was about 8v across the base to emitter on the right hand differential transistor.
Excellent video. After working on a fair few DC coupled HiFi amplifiers - fault finding can occasionally send you bonkers, with every component having the wrong voltage on it, it can lead you a merry dance. The shift in gain from that transistor was fascinating. Transistors are often used with reverse biased base emitter junction to act as a zener.
Hi, I assume transistors within the same DIL package could be well matched, and they would certainly be at the same temperature. So why are they not used in audio amps?
I have been using the transistor tester on the cheap harbor freight meter to match my transistors, just like you heat from fingers throws off the readings!!
Wild idea, you could reverse bias transistor in order to match them. If you have one with slightly more gain than another, you could reverse bias it for a few minutes and regularly check the gain until it is the same as your other one. I don't know if it would have any other effects, though.
Poor cat, 3 days by himself - must be very attached to you. The input transistor on the NF side gone. I think that's what killed my old Sima amp (50W per ch, but very high current 1000W in transformers) which was similar to Mr. Leach design - literally everything got fried VAS, voltage multiplayer, predrivers, drivers after the output section gave up when I was away. Maybe someone thought it was suitable for dance club, as I never learned what happened to it. I think of reusing the remains for D-class amp if I can get really good modules that run on +/-36V rails (Ice, Hypex) - I don't really need more 17-18dBW. If I can get magnet wire I could rewire the secondaries for more voltage - just an idea.
The diode? There isn't a seperate diode in the transistor, it is like two diodes pointing at each other, but they share the same silicone. Instead of NP doped silicone like a diode, its PNP or NPN doped silicone. So basically, 1 1/2 diodes make a transistor :P Though you are right ignoring semantics. You damage the doping in the silicone.
Before someone calls me out, at 6:50, the emitters of the differential pair transistors are near 0v (~.7v) with a normally functioning amp. When the prototype amplifier had full +rail on the output, there was about 8v across the base to emitter on the right hand differential transistor.
Excellent video. After working on a fair few DC coupled HiFi amplifiers - fault finding can occasionally send you bonkers, with every component having the wrong voltage on it, it can lead you a merry dance.
The shift in gain from that transistor was fascinating. Transistors are often used with reverse biased base emitter junction to act as a zener.
Very interesting John 👍 I have a guitar amp that pics up a radio station when I adjust the guitar tone 😱 so I basically have a 100 watt radio😂
I have seen in some Audio Amp they bind the two differential amplifiers pair transistors to each other with a simple common aluminum plate.
Hi, I assume transistors within the same DIL package could be well matched, and they would certainly be at the same temperature. So why are they not used in audio amps?
I wrote "I have seen that soloution" and why they do it you may ask them.
I have been using the transistor tester on the cheap harbor freight meter to match my transistors, just like you heat from fingers throws off the readings!!
Wild idea, you could reverse bias transistor in order to match them. If you have one with slightly more gain than another, you could reverse bias it for a few minutes and regularly check the gain until it is the same as your other one.
I don't know if it would have any other effects, though.
If Snickers won't come to UA-cam, UA-cam comes to Snickers 😻
Poor cat, 3 days by himself - must be very attached to you.
The input transistor on the NF side gone. I think that's what killed my old Sima amp (50W per ch, but very high current 1000W in transformers) which was similar to Mr. Leach design - literally everything got fried VAS, voltage multiplayer, predrivers, drivers after the output section gave up when I was away. Maybe someone thought it was suitable for dance club, as I never learned what happened to it.
I think of reusing the remains for D-class amp if I can get really good modules that run on +/-36V rails (Ice, Hypex) - I don't really need more 17-18dBW. If I can get magnet wire I could rewire the secondaries for more voltage - just an idea.
The way I see it, you got a SERIOUS 'talking to' by Snickers!!! Don't ever leave me like that again HOOOOMAN!
You damage the diode inside the transistor....ahhahhaha talking with the cat like a cat was the best part
The diode? There isn't a seperate diode in the transistor, it is like two diodes pointing at each other, but they share the same silicone. Instead of NP doped silicone like a diode, its PNP or NPN doped silicone. So basically, 1 1/2 diodes make a transistor :P Though you are right ignoring semantics. You damage the doping in the silicone.
So does reverse biasing the B to E junction damage the transistor? I wanted to use a transistor as a voltage reference for a power supply.
Hi john. Is 7293 ic heatsink is connected to +ve Or -ve voltage
it was kinda bad to leave snickers locked up for 3 days. =/
but why there is a capacitor in the feedback resistor?
This allows DC gain to be unity so that slight thermal effects don't cause large offset voltages on the output.
@@JohnAudioTech i see, thanks for your explanation
Our cats are same.