I never thought about fluctuations in the mains electrical lines affecting class a amplifiers. Our power in the Philippines is not stable to say the least. I measured a couple times a few months ago wondering about voltage for running 110 volt power tools. Where normal would be 220 volts, we had 180, 185, 200... Although I heard the power company did something with the nearby transformers, I haven’t tested recently.
What effects could these fluctuations have on an F5 for instance? Could it have any detrimental effects on the bias of the amp or damage the power supply?
Thanks for looking & have a nice day!
What effects could these fluctuations have on an F5 for instance? Could it have any detrimental effects on the bias of the amp or damage the power supply?
Thanks for looking & have a nice day!
depending of particular combo of used parts in your F5 (practically gain of upper vs. lower half of amp), it'll result in more or less sliding DC Offset value, and -of course- decrease in Iq
sound - depending of your particular brain, maybe you'll even like it more with decreased rails and Iq, maybe opposite
🙂
sound - depending of your particular brain, maybe you'll even like it more with decreased rails and Iq, maybe opposite
🙂
Depends on what type of transformer you use and what specific amp. Some amps have zeners in the bias circuit (like the F6) and would have same bias as long as the rail voltage isn't too different.
You could also use a high quality regulated SMPS instead of a normal transformer, many such ones can handle a wide range of input voltage without problems. Finding ones with a lot of watts and +- rails is harder though. You could use a 48V brick and build a virtual ground circuit.
In my case I started with normal transformers but I got problems with humm. I also generally dislike fiddling with high voltage circuits for safety reasons so I dropped the big fat transformers and started using external 24V / 48V power bricks. I did build a virtual ground with the following circuit and can attest that it works great (I added a CL60 in series though to limit the inrush current as the SMPS has problems with the large capacitance otherwise).
Sola constant voltage transformer, the only real solution. They can be fairly cheap used.
https://solahevidutysales.com/pdf/powerconditioners/cvs.pdf
https://solahevidutysales.com/pdf/powerconditioners/cvs.pdf
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Voltage Regulation
If you want your amp to perform the same with those line voltage fluctuations, you will need to regulate the voltage supply to the channel boards. This requires using a higher voltage transformer, for example 20V or 22V instead of 18V, and a circuit that will output a fixed voltage, say +24V and –24V. There are a variety of regulators that might do the job. The simplest would be a Mosfet based capacitance multiplier with a string of zener diodes to set the voltage.
If you want your amp to perform the same with those line voltage fluctuations, you will need to regulate the voltage supply to the channel boards. This requires using a higher voltage transformer, for example 20V or 22V instead of 18V, and a circuit that will output a fixed voltage, say +24V and –24V. There are a variety of regulators that might do the job. The simplest would be a Mosfet based capacitance multiplier with a string of zener diodes to set the voltage.
The thing to worry about is the recovery from the AC line sag. There can be substantial voltage overshoot.
You may be able to convince the local power company to monitor your line voltage for a period of time.
You may be able to convince the local power company to monitor your line voltage for a period of time.
You could try SMPS; that one will not care much about input voltage. Usually, anything between 100 (110) -240V AC will work. But, class A and SMPS is a typical example of an oxymoron, so... it's hard to stay with SMPS even if the end result is really, surprisingly -> very good!
For a class A/AB amp it probably won't do much
We have a rock solid 253v here and i'm pretty sure it explains why our LED globes burn out about as often as old incandescent lights
We have a rock solid 253v here and i'm pretty sure it explains why our LED globes burn out about as often as old incandescent lights