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decoupling capacitor issue !
- Thread starter day747
- Start date
That is true of any DC-coupled amplifier and there are many such.
The definition is wrong, however: a capacitor in series with the signal, a DC-blocking capacitor, is a coupling, not decoupling capacitor. A decoupling capacitor is meant to decouple (isolate) the voltage from any AC signal and so is typically found in the power supply. The DC filtering capacitors in a power supply are decoupling capacitors. The series capacitors in the signal path are coupling capacitors used to pass through AC signals whilst blocking DC.
HTH - Don
The definition is wrong, however: a capacitor in series with the signal, a DC-blocking capacitor, is a coupling, not decoupling capacitor. A decoupling capacitor is meant to decouple (isolate) the voltage from any AC signal and so is typically found in the power supply. The DC filtering capacitors in a power supply are decoupling capacitors. The series capacitors in the signal path are coupling capacitors used to pass through AC signals whilst blocking DC.
HTH - Don
Make sure whatever is driving the amplifier is not DC-coupled or has a correction circuit (feedback loop) that suppresses DC on the signal to the amplifier. DC coupling is usually advertised as a "feature" in the specifications or you can ask the manufacturer of whatever component is driving the amplifier.
Ask Audiophonics unless someone here owns one and can answer. A smart strip is usually the same as turning on and off the power switch so should work as long as it has a physical power switch you can leave on. Some devices use a "soft" power switch that requires power to be applied to activate (turn on) the device. Worst case you can buy or build a trigger circuit, but in your case the simplest solution is to use the trigger output from your Denon to drive the amplifier.
- Thread Starter
- #5
I want to use trigger but I'm afraid of this warning
The warning has nothing to do with the trigger circuit.
This warning is valid for all amplifiers with DC coupled input. To avoid the DC fed into the power amp you may use a capacitor in the signal line (the inner conductor of the shielded audio cable). The value depends on the input impedance of the power amplifier. The data of the AUDIOPHONICS MPA-S250NC don't tell it, also Amirs evaluation not as far as I saw.
Amir's review shows input sensitivity is about 1.7 Vrms (https://www.audiosciencereview.com/forum/index.php?threads/audiophonics-mpa-s250nc-amp-review.45306/). If the Denon's maximum output is 1.2 V you will not achieve full power output from the amplifier but about 30% less (1.2/1.7 ~ 0.7). That is about 3 dB, a significant but not huge reduction in maximum power.
MaxwellsEq
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I think you are a bit confused. There are two types of current: 1) alternating (AC) which includes mains power, video and audio signals (whether analogue or digital) and 2) Direct Current (DC) which is the sort of thing generated by batteries and power supplies.
There is nothing wrong with a DC-coupled power amplifier, except if you put a DC signal into it, in which case it can amplify this signal and send it to your speakers. Speakers hate DC, they like AC. So, to avoid this problem, make certain your device that is plugged into the power amplifier is AC coupled (has a capacitor in series), or is working well and not sending DC on its outputs.
This has a) nothing to do with how much AC signal your previous device outputs which is that 1.2V AC value above.
This has b) nothing to do with trigger circuitry at all
You might find it helpful to read up a bit about Alternating and Direct Current e.g. https://www.allaboutcircuits.com/textbook/alternating-current/chpt-1/what-is-alternating-current-ac/
There is nothing wrong with a DC-coupled power amplifier, except if you put a DC signal into it, in which case it can amplify this signal and send it to your speakers. Speakers hate DC, they like AC. So, to avoid this problem, make certain your device that is plugged into the power amplifier is AC coupled (has a capacitor in series), or is working well and not sending DC on its outputs.
This has a) nothing to do with how much AC signal your previous device outputs which is that 1.2V AC value above.
This has b) nothing to do with trigger circuitry at all
You might find it helpful to read up a bit about Alternating and Direct Current e.g. https://www.allaboutcircuits.com/textbook/alternating-current/chpt-1/what-is-alternating-current-ac/
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