I have posted the draft of what to be the ouput and speaker arrangement. This might work smoothly without turn on thump as per mr Nico Ras.
I am also planning to incorporate a dc protection circuit tap from amp ouput in case there's a failure in the amp. The only question is it will be incorporated? Any ideas?
I am also planning to incorporate a dc protection circuit tap from amp ouput in case there's a failure in the amp. The only question is it will be incorporated? Any ideas?
Isn't this thread a bit narrow minded from the begginning?
If you have a single 140V rail and full bridge results in both too high complexity and too high power, consider trading your 250V capacitors for others rated at 100V, adding a center tap to the capacitor bank and calling it ground.
Since no substantial DC current must flow through the speaker, a simple linear balancer circuit with transistors and op-amps is enough to correct for the minor DC current unbalance (amplifier bias, capacitor leakage) and keep the center tap at the middle (in average).
Then, any amplifier circuit intended for +/-70V can be used.
QSC made this topology popular back in 1970s and 1980s, with one secondary winding per channel, but with grounded output and floating supplies (which in turn requires independent winding(s) for each channel, provided by a standard transformer with only 2 secondaries). Switched rails made it more complex and less beatiful on paper in later circuits...
EDIT: For a stereo pair of channels, and since L and R signals tend to be quite closely matched at low frequencies, the capacitor bank may be relieved from the ripple current (and voltage) due to speaker current. This is accomplished by inverting the input signal to one of the channels and wiring the corresponding speaker output with reversed polarity. As a result, much less capacitance is required for full LF output.
If you have a single 140V rail and full bridge results in both too high complexity and too high power, consider trading your 250V capacitors for others rated at 100V, adding a center tap to the capacitor bank and calling it ground.
Since no substantial DC current must flow through the speaker, a simple linear balancer circuit with transistors and op-amps is enough to correct for the minor DC current unbalance (amplifier bias, capacitor leakage) and keep the center tap at the middle (in average).
Then, any amplifier circuit intended for +/-70V can be used.
QSC made this topology popular back in 1970s and 1980s, with one secondary winding per channel, but with grounded output and floating supplies (which in turn requires independent winding(s) for each channel, provided by a standard transformer with only 2 secondaries). Switched rails made it more complex and less beatiful on paper in later circuits...
EDIT: For a stereo pair of channels, and since L and R signals tend to be quite closely matched at low frequencies, the capacitor bank may be relieved from the ripple current (and voltage) due to speaker current. This is accomplished by inverting the input signal to one of the channels and wiring the corresponding speaker output with reversed polarity. As a result, much less capacitance is required for full LF output.
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Yes Eva, this thread is narrow minded for the experts here like you but for us amateurs maybe not, that's why I am asking anybody here to help me out to design my project to fit in my available parts with a little concept of old and new designs.
As you said, bridging this amp or having a +/-140 rails will definitely give enermous power whish i dont require so just opted for a single rail.
As what you suggested,I will just add another 250V capacitors(which i have) in series to the PSU is no problem just to have a center tap point or ground.
If i invert the other channel input signal and the speaker terminal so the two channel is out of phase. just like push and pull?
As you said, bridging this amp or having a +/-140 rails will definitely give enermous power whish i dont require so just opted for a single rail.
As what you suggested,I will just add another 250V capacitors(which i have) in series to the PSU is no problem just to have a center tap point or ground.
If i invert the other channel input signal and the speaker terminal so the two channel is out of phase. just like push and pull?
Simple voltage balancer... The 100uF capacitor is compensating a very-low-frequency feedback loop (and reducing dissipation by averaging the error) and may need adjustment depending on total supply capacitance.
This circuit should be able to correct more than 50mA of unbalance between the currents supplied by each rail.
If the input to one channel is inverted, and the output polarity of that channel reversed, the effect could be called "center tapped" full bridge. When one channel is sourcing current the other will typically be sinking a similar amount of current, so ripple current and stress on the 10000uF 100V balancing (center tap) capacitors is very small. In fact, these capacitors would only see the difference in AC current between both speakers.
DC protection is strongly recommended.
Ssingle supply and output coupling caps for something with 140V (+/-70V) rails is really narrow thinking.
This circuit should be able to correct more than 50mA of unbalance between the currents supplied by each rail.
If the input to one channel is inverted, and the output polarity of that channel reversed, the effect could be called "center tapped" full bridge. When one channel is sourcing current the other will typically be sinking a similar amount of current, so ripple current and stress on the 10000uF 100V balancing (center tap) capacitors is very small. In fact, these capacitors would only see the difference in AC current between both speakers.
DC protection is strongly recommended.
Ssingle supply and output coupling caps for something with 140V (+/-70V) rails is really narrow thinking.
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Now Eva I see and understand what you're talking about and thanks for kind explanations.
I will try your voltage balancer and i hope it will be better than capacitor output coupling.
Will the 10,000uf of capacitances can handle the need for stereo operation?
If I'm going to increase the capacitance to about 20,000uF, will these be better or just the same result?
Hi Eva,
Regarding the transistors in the voltage balancer, does it require a large transistor ,medium size or a small signal transistor that will do the job?
I have seen some of the QSC schematics and I really appreciate it. They used the supply caps as signal paths just to connect the collector grounded. this is just the another way around. I just dont see the voltage balancer there. this might be a good additional things...
Regarding the transistors in the voltage balancer, does it require a large transistor ,medium size or a small signal transistor that will do the job?
I have seen some of the QSC schematics and I really appreciate it. They used the supply caps as signal paths just to connect the collector grounded. this is just the another way around. I just dont see the voltage balancer there. this might be a good additional things...
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