High current amplifiers

Antman27 · « **on:** 24 May 2007, 04:45 pm »

Hello all .
I was wondering if someone could explain high current amplifiers to me ?
I was reading that the speakers I am using sound much better with high current amplifiers not high power .
When I did a goggle Parasound amps came up as high current amplifiers
Could I get a amp with lower and high current ?
I do not have much space left in the rack so a large amp is out of the question
It may be fun to see what the parasound Zamp would do it is tiny
Thanks

PaulHilgeman · « **Reply #1 on:** 24 May 2007, 05:25 pm »

High current means that the amplifier has the capability to supply large amounts of current through the speaker when it is demanded. This can be demanded two ways, either by loud passages in the music, or low impedance in the speaker.

For the same power output, roughly 1.414 times the current is required for a halving of the impedance, and roughly 1.414 times the current is required for the doubling of power output.

So, using an amplifier than can supply large amounts of current is important for the dynamic passages in music as well as being compatible with large numbers of different speakers.

That said, it is important also to be able to supply high voltage levels as well, though this is much easier and cheaper to accomplish in the design of the amplifier.

If you know the peak current delivery of the amplifier and you know the lowest impedance of your speaker, the RMS power delivery into the lowest impedance of the speaker will be:

Peak Current = I
Lowest Impedance = R

RMS Power = (I^2 * R)/1.414

If you know the peak voltage swing of your amplifier, and the highest impedance point of your speaker, the RMS power delivery into the highest impedance point will be:

Peak Voltage = V
Highest Impedance = R

RMS Power = (V^2 / R)/1.414

So, as you can see, there are many factors that go into power ratings and high-current is a necessity as is the proper voltage swing as is just matching the loudspeaker's sensitivity and impedance to the proper type of amplifier, not to mention the 'sound'.

Hope this helps,
Paul Hilgeman

mcgsxr · « **Reply #2 on:** 24 May 2007, 06:38 pm »

For me, the high current thing has always been easiest to describe via a car audio amp - the old Orion 225 HCCA.

25 wpc at 4ohm.
50 wpc at 2ohm
100 wpc at 1ohm
and unbelievable stable at 200 wpc at 0.5ohm in stereo!

So, low power at "normal" R, but BEASTLY power at low R!

TomS · « **Reply #3 on:** 24 May 2007, 06:46 pm »

Quote from: mcgsxr on 24 May 2007, 06:38 pm

...and unbelievable stable at 200 wpc at 0.5ohm in stereo!

This seems to be falling into the welder territory for me

I'm still trying to figure out if current is so great, why the little Trends and Sonic amps sound so good, even to fairly decent levels. Maybe it has something to do with most things in that fall in the "first watt" zone.

PaulHilgeman · « **Reply #4 on:** 24 May 2007, 07:32 pm »

Quote

Maybe it has something to do with most things in that fall in the "first watt" zone.

Exactly.

If that part isn't gotten right, none of it can be right, we cross back through that first watt thousands of times per second.

-Paul

mcgsxr · « **Reply #5 on:** 24 May 2007, 07:55 pm »

First watt - totally, explains why my 3wpc SE Pentode EL84 amp makes me so happy!

Tweaker · « **Reply #6 on:** 24 May 2007, 08:37 pm »

Quote

I'm still trying to figure out if current is so great, why the little Trends and Sonic amps sound so good, even to fairly decent levels. Maybe it has something to do with most things in that fall in the "first watt" zone.

They have to be matched with fairly efficient speakers to sound good. Speakers over 90 dB efficiency aren't going to need much current, it seems, to rock and roll. My old Acoustat and Magnepans, however, really didn't sing unless mated to a high current amp.
I wish more manufacturer's published the current delivery spec as I have come to place a fair bit of importance on it, although perhaps a bit less so now as my present speakers are fairly efficient.

warnerwh · « **Reply #7 on:** 24 May 2007, 09:44 pm »

You can get an idea if an amp is truly high current by the power specs. Into 4 ohms it should be a minimum of 1.5 times more powerful. Being able to deliver more power as the impedance drops tells you it's a high current amp.

Antman27 · « **Reply #8 on:** 25 May 2007, 12:47 am »

Man the more I try to learn the more I get confused what to do

Tweaker · « **Reply #9 on:** 25 May 2007, 01:21 am »

Quote from: warnerwh on 24 May 2007, 09:44 pm

You can get an idea if an amp is truly high current by the power specs. Into 4 ohms it should be a minimum of 1.5 times more powerful. Being able to deliver more power as the impedance drops tells you it's a high current amp.

I'll add to the confusion.
I had a Carver amp years ago that spec'd 200/400 wpc 8/4 ohms. It had a current delivery of about 27 amps peak to peak, (which ironically made it a poor match for for the Carver Amazing Loudspeaker, a very current hungry design). I replaced it with a B&K which was rated 200/350 wpc 8/4 ohms yet it's current output was around 45 amps peak to peak.

If you need a high current design but have space limitations try an ICEPower based amp. They all double their output into 4 ohms and can be very compact. Some affordable ones are made by Murano Audio, Wyred 4 Sound, and D-sonic.

crossroadazn · « **Reply #10 on:** 25 May 2007, 02:32 am »

But the Autoformer stable at the same wattage in different impedance and have the same curent.
McIntosh MC202 200/8/4/2 Ohm with peak to peak 50 Ampere. aa

sleepysurf · « **Reply #11 on:** 25 May 2007, 02:50 am »

Some interesting specs...

Plinius SA 103- 50 amp peak current output
Pass Labs X350.5- 20 amps peak current output
Belles 350A Reference amp- 64 amps peak current output

Feel free to add others for comparison.

bummrush · « **Reply #12 on:** 25 May 2007, 02:53 am »

I'm listening to Tandberg 3012,that beatiful int. grips my speakers like any number of amps could only dream of,it didnt make one bit of difference whether the other amps doubled power into into 4 ohms or not,also the bottom end of 3012 is mind blowing.

Tweaker · « **Reply #13 on:** 25 May 2007, 03:49 am »

Quote from: bummrush on 25 May 2007, 02:53 am

I'm listening to Tandberg 3012,that beatiful int. grips my speakers like any number of amps could only dream of...

Maybe due to a high damping factor?

rabpaul · « **Reply #14 on:** 25 May 2007, 07:02 am »

Antman,
It would help to know what speakers you are using. A high current amp is one which has the ability to drive speakers with low impedences (typically below 3 Ohms) without clipping (running out of power). Famous examples are Krell and Mark Levinson.

denjo · « **Reply #15 on:** 25 May 2007, 07:59 am »

Innersound ESL amplifier (now Sanders ESL amplifier) - 135 amps

Extract from Stereo Times, "Innersound Electrostatic Amplifier
Doubletakes!" by Frank Alles & Martin Appel, 1 June 2000
http://www.stereotimes.com/amp060100.shtml

Quote

Basically, Roger Sanders has designed this amplifier to handle the very demanding and taxing loads that electrostatic speakers place on them (as low as 2 ohms) and consequently work extremely well with the less demanding loads of more conventional magnetic speakers.

If I can sum up his philosophy in a nutshell it would be that adequate, clean power is required to truly convey all the musical information through your system by eliminating the harsh effects of clipping and that this should not come at the cost of a new car! He does this by providing a massive output stage. Says Roger, "Each output transistor is capable of delivering 250 watts-and there are eighteen of these per channel. As a result, it could deliver a staggering 135 amps of current with a combined power rating of 4,500 watts per channel." I called Roger to clarify this statement. He said that one would need a power supply four times the size of the amp to truly produce this amount of power. The reason for using this number of output transistors was to provide a very large safety factor without the use of protection circuitry, which could have deleterious affects on the sound quality. All of this is done to produce music, effortlessly, clearly and accurately without that "transistor-sound."

NewBuyer · « **Reply #16 on:** 25 May 2007, 08:20 am »

Musical Fidelity A5cr stereo amp is spec'd at:

255 watts per channel @ 8 ohms;
416 watts per channel @ 4 ohms;
more than 600 watts per channel @ 2 ohms;

and 200 amps current peak-to-peak.

denjo · « **Reply #17 on:** 25 May 2007, 08:40 am »

Newbuyer

Yes, those figures are peak-to-peak and I would be quite surprised if the power is sustainable over a continuous period of time. You might find this link of interest: http://forums.audioholics.com/forums/showthread.php?t=22029

Dan Banquer · « **Reply #18 on:** 25 May 2007, 11:50 am »

Adding fuel to the fire:
http://www.audioholics.com/education/amplifier-technology/the-high-instantaneous-current-spec

d.b.

ctviggen · « **Reply #19 on:** 25 May 2007, 12:28 pm »

Not to mention that the amp is still hooked up to a 20 amp (max) circuit. Even if it's the only thing on the circuit, it can only withdraw 20 amps (perhaps a little more, depending on how quickly the breaker reacts to over current conditions). Sooner or later that 200 amp output is going to have to stop.

By the way, nice article, Dan.