don't mean to butt in here rather rudely, but I think Mooly and another user did explain why: becuase of instability with the midpoint voltage, and the need for a phase inverter (mind you a transistor with taps on emitter and collectro would work fine I suppose).
But mainly for this reason, which is my own:
This is a circuit that was designed decades ago, when bridging wasn't even a word in audio. It would be counter-intuitive to apply modern-day techniques to an old design which will only show more its shortcomings in bridged mode. It will not retain its essence. At least that's what I think. I have an amplifier that is a copy of an EICO Cortina 3070, just like the schematic (very close) and can tell you that the midpoint voltage is not only subject to instability, but has the "thump" when you turn it on...
If you want more power, why not then take another design, like the more common PNP-NPN push pull circuits?
Or simply raise the supply voltage...
But mainly for this reason, which is my own:
This is a circuit that was designed decades ago, when bridging wasn't even a word in audio. It would be counter-intuitive to apply modern-day techniques to an old design which will only show more its shortcomings in bridged mode. It will not retain its essence. At least that's what I think. I have an amplifier that is a copy of an EICO Cortina 3070, just like the schematic (very close) and can tell you that the midpoint voltage is not only subject to instability, but has the "thump" when you turn it on...
If you want more power, why not then take another design, like the more common PNP-NPN push pull circuits?
Or simply raise the supply voltage...
This problem exists with today's modern amplifier also.
This problem is solved using individual components.
I want to say that there are seeds that will solve it
I know that will need me to phase inverter for bridge amplifier.
I send you a scheme very simple inverter.
Edit my sheme with the differential pair of transistors requires a good knowledge constructors.I do not have to.
If I had the offset of the 2-3V, I know that it is more complex and spam.
Then I have a big problem to make the bridge amplifier
I hope so that I don't have that big ofset.
I think that dissipation of offset voltage to be spend on emiters resistors on output transistors?Am I right?
Can you tell me whether this amplifier can really give 25W?
The voltage of 30V, I think I can not get 25W?
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Many thanks for mentioning these amps and for the links - I have made one of these "black devils" way back in 1986, I think, but it had such a good sound that some studio people never gave it back to me. Why did that design not create more attention? Even in those days simple design with output caps were somehow suspect...
Gerhard Haas published another article with some modifications to the original circuit, do you have this informations? (I have only the orginal ELRAD mags with the basic article. - ELRAD was btw also the first magazine which published John Lindsey Hood in german)
R5 is capacitively coupled, the DC gain is 1. How bad could it be with just a little resistor selection? 50 mV?
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funny how old questions resurface in different threads - I'm referring to the discussion about output capacitors. I think it's wrong that some commentaries on the web refer to output capacitors as bad. I'm 100% with Hugh and Lumba on this one - the power supply is in the path of current that flows through the speaker. The a.c. current flow through the speaker flows through the output stage of the amplifier and also the power supply - through the filter caps.
The only real question for me is where the feedback is taken from. If the output capacitor is outside the nfb loop then the behaviour is different than if it is put inside the nfb loop (with attendant problems).
The only real question for me is where the feedback is taken from. If the output capacitor is outside the nfb loop then the behaviour is different than if it is put inside the nfb loop (with attendant problems).
A single amp that runs on 2X volts will generally have better perfromance than a bridge that runs on X volts. Lower distortion, higher output swing as a percentage of supply voltage, lower parts count. But perhaps a bridge amp may be worthwhile if you're trying to get the most watts out of what you may already have. Say, a 30 volt high current transformer that may or may not have a center tap, a bunch of big 50V soup can caps, 100 volt power transistors...
Frend, could you help me when and if I bild this amplifier in bridge mode.
I build first in the kit,with 2N3055( my first shematic),than later I wont build with AD150.
If I am satisfied with the sound than I make as bridge mode(AD150- second shematic).
Can I count on your help?
I like to do in bridge mode ,bacause in 8 ohms amp give me only 10-12W(this is too small power),and I like to build with Germanium transistor.
Thanks for help!
I build first in the kit,with 2N3055( my first shematic),than later I wont build with AD150.
If I am satisfied with the sound than I make as bridge mode(AD150- second shematic).
Can I count on your help?
I like to do in bridge mode ,bacause in 8 ohms amp give me only 10-12W(this is too small power),and I like to build with Germanium transistor.
Thanks for help!
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The second is curiosity value only... germanium devices...
Build the first one as per the circuit. You will be amazed at how good it sounds, and from a kit you have a better chance of success if you take it slowly and check everything along the way.
Forget bridging it too.
Why do you want to use Germanium... ? It would be so prone to problems, possible unreliability and thermal issues. Anything warmer than a cold cup of coffee and you would be in trouble
Build the first one as per the circuit. You will be amazed at how good it sounds, and from a kit you have a better chance of success if you take it slowly and check everything along the way.
Forget bridging it too.
Why do you want to use Germanium... ? It would be so prone to problems, possible unreliability and thermal issues. Anything warmer than a cold cup of coffee and you would be in trouble
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