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two opposed transistors to clamp audio signal
two opposed transistors to clamp audio signal
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Old 9th April 2013, 09:56 PM   #1
anwaypasible is offline anwaypasible  United States
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Default two opposed transistors to clamp audio signal

you get the positive rail, the negative rail.. each one gets a transistor (or row of transistors) with the positive or negative preamp connection to set off the transistor to let out the amplified power like a relay.

i realize using the opposite rail can clamp down on the audio signal to give it a tighter control.

i read somewhere that if you leave the preamp wire connected to the pin, and then flip the other two pins around.. the output will be 180 degrees out of phase with the signal from the preamp.

i figure that it needs to be noted, if you've got one soundwave playing through the positive rail transistor.. and the opposite phase soundwave playing through the negative rail transistor .. those two soundwaves will come together to create a constant line instead of a wave .. and that means the speaker cone won't move (if the electricity even makes it out of the amplifier) the coil would just gather up heat.

what i was wondering,
connect the positive rail to the negative rail pins without swapping the two pins noted above.. the capacitors would pop?
the transistors would pop?

flip the two pins around to get 180 degrees out of phase with the preamp signal, but touch positive rail to negative rail to clamp the audio signal..
the capacitors would pop?
the transistors would pop?

i know 1:1 ratio transformers can go in the preamp section, but i don't know anything that big for the capacitor rails.. and i also don't know if it would help with component failure.
but i read something about the darlington transistor where it was like a transistor inside of a transistor.. maybe that one would give enough isolation to prevent component failure (if any) ?

i figure the output voltage would drop to half if i clamped both rails.
would the current capacity also drop to half or double?
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Old 9th April 2013, 10:30 PM   #2
GoatGuy is offline GoatGuy  United States
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What on earth are you smoking? [LOL]

I'm sorry to be unhelpful - but this is not the way you design amplifier stages, Grasshopper. You start one of three ways - utilizing sections of designs that others have perfected (or at least written about in detail), or second, by starting with your mental Library of Desired topologies to implement, or last - the hard way - from the characteristics of the amplifying devices and passives themselves. The third way, the "hard way" is hard, because it requires so much education in the particular aspects of the active and passive components involved. Yet, that's what we do, who have the EE background, and the AF/analog experience. Its satisfying to design from that vantage, but the other two ways are good too.

FIRST though - you're not going to get phase reversal by reversing pins on a transistor. You're going to most likely get a blown transistor, and no amplification.

Second, don't try to "clamp" anything to a rail just because the word "clamp" sounds like it might increase "control" or anything like that.

Third, even if the transistors don't pop, the electrolytic capacitors will most likely fission on you. Expensive fuses, capacitors are!

Fourth, please - pretty please - read more than "something about a Darlington being a transistor inside a transistor". The answer is very specific: a small transistor and a larger transistor, with collectors in common. The emitter of the small transistor is connected to the base of the larger one. This leaves a 3-terminal "device", if its all in one can. The most notable effect of this configuration is that the gain of the pair of devices is the gain of A and B multiplied.

Don't go clamping rails there. You're heading into dangerous territory.


PS: remember WIKIPEDIA is your friend. You can look up almost every kind of circuit-topology detail, and get a decent explanation. Start clicking!

Last edited by GoatGuy; 9th April 2013 at 10:32 PM. Reason: no PS
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Old 10th April 2013, 12:41 AM   #3
Ian Finch is offline Ian Finch  Australia
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Location: Coffs Harbour, NSW
Get some education and practice in solid state electronics first before trying to reason out circuit operation for yourself. You can try almost anything at low voltages on a breadboard with protection resistors to save your parts but you still need to know how to do this this suitably and you need a systematic guide through the maze of design possibilities.
This book is among the best comprehensive texts but there are also plenty of books (and e-books, of course) pitched at general and DIY interest level and plenty of teaching forums focused on popular topics like audio electronics.
If only I had listened....
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Old 10th April 2013, 04:08 AM   #4
Pano is online now Pano  United States
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two opposed transistors to clamp audio signal
OT and Personal remarks removed
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Old 10th April 2013, 07:09 AM   #5
GoatGuy is offline GoatGuy  United States
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Thanks Pano GoatGuy
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Old 10th April 2013, 10:53 AM   #6
AndrewT is offline AndrewT  Scotland
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A diode connected transistor makes a good diode.
These can be used to clamp voltages.
I think it was Jung that said some models of transistor make better low leakage diodes than using real diodes.
regards Andrew T.
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Old 10th April 2013, 01:16 PM   #7
Cal Weldon is offline Cal Weldon  Canada
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two opposed transistors to clamp audio signal

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Old 11th November 2013, 07:40 PM   #8
costis_n is offline costis_n  Greece
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Is it wrong to admit I love the posts of this guy?
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