"Enhancements" - just for the sake of creating them
DC protect
Why? That's the consumer thing to do. They won't replace a fuse with the correct value.
Usually requires some sort of indicator.
Clipping indicator
A good idea in general
left/right/pos clip/neg clip
You can use color to indicate which rail clipped.
Overtemperature indicator
really depends on how well the temperature compensation is designed.
Input & speaker anti-thump
Generally it's part of the DC protect stuff as well.
Reset
Recycle power?
Troubeshooting mode
Some easy way to troubleshoot.
Often overlooked.
Protections sometimes need to be disabled
My amp requires me to remove and extend a connector for power+, power-, gnd, and, speaker out
It also has an RCA jack on the board itself bypassing the external VACTROL
The RC network at the speaker is not connected using this mode
A resistor in series with the line needs to be bypassed.
Displays (bar graph)
Their "cute".
Most of the time they assume 8 ohms.
Definately indicates loudness and even "close to clipping"
Remote ON
Useful because the pre-amp is limited in the amount of power it can switch.
So, you have two power cords.
One is used to enable the power (from the pre-amp). The other goes to the wall.
This **broken link removed** supports a low voltage trigger in/trigger out
signals. This is starting to become more common in home automation systems.
Convienience outlets
With remote on, it's now possible to have switched and unswitched outlets.
They basically remove clutter, but make it harder to remove just the amp.
Surge supression
From RFI filters to slow turn-on to ZNR's across the main filter caps.
Troubeshooting mode
Often overlooked
It's just ways to make troubeshooting easier.
In my amp I have to:
Remove the module by disconnecting a phono input and the connector supporting power and the connector supporting power and the connector supporting the speake
The VACTROL and speaker protection are in the chassis.
I did not make it convient to bypass the AC line resistor or jump it.
As I said before - my protection circuit needs work.
An electronic mute input
Why? An automation control input. Doorbell or phone rings.
Some amount of "always on" power
e.g. Suppose that "trigger" is implemented by AC or some other way.
A microprocessor could also used for power up stuff
Out of all that, what's the most useful?
I would vote:
Design with troubleshooting mode in mind and not mass production
Surge suppression
(A lifetime issue)
Remote power via AC
(Depends on total power: 70*2 and 100 is 240 W. Don't let the pre-amp try to switch it)
Thump - depend son the amp
Slow turn on - depends on the amp
Clip - depends on the amp power and whether one likes high frequencies.
Hi temp - might be useful for an unknown amplifer
Some of the above could be integrated into a microprocessor.
Nearly everything suggested above with the exception of the VU meter is internal.
An extra power in connector (e.g. the 3A version) supports external turn on.
DC triggers would require panel space.
DC LED (e.g. Protect), Clip Left, Clip right, Thermal require panel space.
Even if they don't work, they might be cool.
Thermal without shutting down could be easy. Protect could be part of the anti-thump. e.g. It's on for the short time the speaker relays are open during power up..
Clip is harder.
e.g.
Put labels of
Protect---TEMP--DC-- CLIP on each side of the amp and sub.
Another option is to put protect totally in a different place. e.g. On the front panel, centered in width, a few cm from the top edge or near the power switch.