whatever happened to impedance switches?

[Jessica]

Anyone else remember when amps had a switch to select your ohm load? i remember my brothers old kenwoods had them and i thought some RF amps had a board in side you would adjust dip switches or something(never owned one) and my grandfather gave me a tube amp that had a 8/16/24 ohm load selector on the back.

[ALPINE408]

Never seen it.... The fosgate chips where cross over adjustments... I've owned them before my friend still has some

[Colin - STAPUFT]

I *think* the Linear Power amps have one or something like that, but inside the amp?

[Johnny2Bad]

There is really no point to an output impedance switch on a Solid State power amplifier, but I can see it being part of a crude protection scheme (adding a power resistor for safety sake) which basically means a poor or budget design.

Vacuum State amplifiers put out the most power when the output transformer and the load are well matched in impedance, but less power if the output transformer's impedance and the speaker impedance are poorly matched. As long as the impedance is matched, a Tube amp puts out the same power into any load. So you would want to use the 4 ohm tap with 4 ohm speakers (for example) on a tube amp for best power delivery, and it's common for a tube amp to have multiple taps (4,8 and sometimes 16 ohm).

Properly hooked up, a tube amp rated at (for example) 20 watts it would be 20 watts into 4, 8, or 16 ohms if it had all three taps.

Note that there is such a thing as a transformer-coupled output state in a Solid State amp, but it's rare, found mostly on 1960's gear.

Note also that we are referring to impedance taps on the output transformer, not the actual measured output impedance (which is relatively high in tube amps but generally lower than 1 ohm).

[RooTxBeeR]

Class has started, and I don't have a pencil. How many more lessons? lol good info man. That could be a cool feature. You just plug up all the +/- off the subs to the amp and just select eh ohm load or something?