Question about high current amps versus "not high current amps"

@panzrwagn +1 simplest test of amp current handling adequacy is to tap low frequency. driver membrane and checking voltage waveform at speaker terminals with the scope.. if voltage amplitude p-p observed is more than 10mV, then need to check speaker connectors, cable, amp relay contacts, and then try higher current amp design to see if it helps!

I just wish that speaker manufacturers who make speakers requiring high current amps with amazing damping factors to simply recommend a few amps. It doesn't have to be an endorsement exactly but give a few examples and say, "high current amplifiers similar to these in specifications, quality, and capability."  That would go a long way to keeping customers happy. I'm looking at you Magnepan, but of course there are others out there too. Not all consumers are as clued into what the needs are, then they buy speakers and are not happy with them and don't understand why and maybe end up giving those speakers bad reviews on forums and such. 

A Coda 16 has 280,000 uF of capacitance and can deliver 100 amps of current, per channel.

That’s what Coda claims about their No.8 amp as well (100A/Ch), however, my Yamaha A-S2100 integrated sounds more powerful and has considerably better bass authority than the No.8 I owned. Not sure why they feel inclined to make such an outrageous claim. They make good amps, that should be good enough.

 

I will very quietly suggest that the best tool for evaluating how well an amp drives a speaker is to listen to the combination.  You can try to think your way into decisions but using those comparison tools on your head is much more fun and they will produce the best long term results. Shields up: prepared for incoming fire. 

simplest test of amp current handling adequacy is to tap low frequency. driver membrane and checking voltage waveform at speaker terminals with the scope.. if voltage amplitude p-p observed is more than 10mV, then need to check speaker connectors, cable, amp relay contacts, and then try higher current amp design to see if it helps!

@westcoastaudiophile  This does not show if the amp is 'high current' or not. It simply shows if the amp has a low output impedance (if yes, is able to damp the EMF thus generated).

@atmasphere correct! :-) Testing amp “effective” current range is not trivia, and it is beyond what is discussed in AG! my post was a simplest debug approach to check for major amp-spkr issues, before starting to randomly change components!

As others have pointed out, if the amplifier in question doubles output power with each halving of impedance, it's a strong sign that it's a high current amplifier.  Some manufacturers will claim a max current spec, for example, the venerable Adcom 555 series claimed (IIRC) 30 amps.  With 8 output devices per channel in push pull, the summed current rating of 15 amps each makes that claim very plausible.  An amp I like even better, the much maligned HK Signature 1.5, has 12 output devices per channel, also 15 amp devices, yet the manual claims 130 amps of current.  This may be marketingspeak, as they don't mention whether it's per channel or both combined.  In any case, it seems that a combination of output devices and their summed current rating, along with the stored energy in the power supply capacitors, would be the secret to how much current can be sustained for a period of time.  It's definitely a topic I'd like to know more about as well.

@dlevi67 that was a good summary from an engineering perspective, and a good introduction to Ohm's Law, which is exactly how I learned from other engineers (fellows) when first designing amps and speaker systems as a hobbyist.

The others came in nicely with the nuances regarding load, sensitivity, etc

Given the same 100 RMS 8 Ohm amp/circuitry, but one power supply with 1000 micro F and the other with 100,000 micro F. Speaker has an impedance dip to 2 ohm at 100 Hz. Can the 100k cap amp not provide a LOT more amps (for 1 millisecond) than the 1k cap amp? Isn't that were the "100 Watt RMS, 200 Watt PEAK" nomenclature comes into the picture? 

I do remember (40 years ago) an amplifier that included a car battery as 'short term' amp booster (similar to what I think a large cap in a power supply does)?

@dishman442 

I agree that listening is the way to go. It's served me well in the past 40 years of evaluating equipment.

@immatthewj

The PIE forumla works but you need to know the amp rail voltage and not the wall outlet voltage.

The best way to find a robust, high current amp is to find one that doubles the wattage output at 4 ohms and has 2-ohm capability. Example 200 watts at 8 ohms and 400 watts at 4 ohms. Most Pass Labs and McIntosh amplifiers do this very well for example although Macs use autoformers to make sure they are stable at the desired impedance.

An amplifier that has the same output at 4 ohms and 8 ohms is an example of a less robust, low current capable design.