Amperage 2 vs 4 channels amplifier

I would ignore those specs altogether. Amplifier current ratings are among the most useless of specs, IMO, as they almost always represent how much current the amplifier (or in some cases just its power supply by itself) can supply into a dead short (zero ohms) for an unspecified tiny fraction of a second. Consider the following:

60 amperes into 2 ohms corresponds to 7200 watts
60 amperes into 4 ohms corresponds to 14400 watts
60 amperes into 8 ohms corresponds to 28800 watts
120 amperes into 2 ohms corresponds to 28800 watts
120 amperes into 4 ohms corresponds to 57600 watts
120 amperes into 8 ohms corresponds to 115200 watts

So obviously those amounts of current are never supplied into real-world speakers.

For further discussion of this see the following thread:

https://forum.audiogon.com/discussions/current-limit-onset-definition

Regards,
-- Al

What Al said: ignore.

Although an amplifier max current rating doesn't represent anything useful, however, if two amplifier both rated 100watt/channel, one max current rated 50A and the other one rated 30A, we can assume that the 50A rated one has a beefier power supply.

Max current represents how beefy the output stages are but it does not  mean the power supply could handle more than 1 channel doing this at once. It's' just a measure if the amps ability to handle difficult loads. Bragging rights, if you will.

Also keep in mind for HT, the center channel has most of the output, surrounds have the least, especially if following the THX model of crossing them all over at 80 Hz. 

@imhififan
Not necessarily, especially if the amps being compared are from different manufacturers, because (using your example) the amount of time the 50 amperes and 30 amperes can be supplied for is not usually specified. For example, the 50 amperes may be suppliable into zero ohms for only 10 milliseconds, while the 30 amperes may be suppliable into zero ohms for 25 milliseconds.

Also, the amount of current that can be supplied into zero ohms for these brief amounts of time may be limited by the output impedance of the particular amp, which is unrelated to the power supply.

So generally speaking I don’t think these specs can be used as an indicator of power supply "beefiness," or of anything else for that matter.

Best regards,
-- Al

We have 2 amplifier from one manufacturers.

Amp 1 - 4 channels, 125 Watt, Maximum Current: 60 Amperes peak per channel.
Amp 2 - 2 channels, 125 Watt, Maximum Current: 100 Amperes peak per channel.
If we connect these amplifiers to identical speakers, first amp using bi-amping (all 4 channel in use)
and another (2 channels) just using bi-wiring cable.

Which amplifier will have more control on speakers?

Not necessarily, especially if the amps being compared are from different manufacturers, because (using your example) the amount of time the 50 amperes and 30 amperes can be supplied for is not usually specified. For example, the 50 amperes may be suppliable into zero ohms for only 10 milliseconds, while the 30 amperes may be suppliable into zero ohms for 25 milliseconds.

@almarg
That's true, thanks!

We have 2 amplifier from one manufacturers.

Amp 1 - 4 channels, 125 Watt, Maximum Current: 60 Amperes peak per channel.
Amp 2 - 2 channels, 125 Watt, Maximum Current: 100 Amperes peak per channel.
If we connect these amplifiers to identical speakers, first amp using bi-amping (all 4 channel in use)
and another (2 channels) just using bi-wiring cable.

Which amplifier will have more control on speakers?

Hard to say. 125W of average power is 250W peak. That implies only 11.2A peak at 2 ohm load. You will never need 60A for anything. You might assume that 100A amp has beefier power supply, but it might not be true. 60A amp can have better and well regulated power supply, but has current limit of 60A by design. Within this limit 60A amp might actually have lower output impedance than 100A amp.

Difference of output impedance between, for instance, 0.05ohm (DF=160) vs 0.1ohm (DF=80) means nothing for control of the speaker (damping) since you already have speaker’s resistance in series, that is in order of many ohms. The best DF that you can get in reality is about DF=1.5 since impedance of the speaker at bass frequencies is about 2/3 of nominal (1kHz) speaker’s impedance. You don’t want to make it worse but 10x better DF=15 for amp should be satisfactory. Big numbers like 60A or 100A is pure specsmanship. Would you buy computer keyboard because it allows to type milion words per minute?