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Old 31st January 2005, 08:41 PM   #1
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Default High Current Amps

I'm afraid i do not know alot about amplifiers, or types of amplifier classes, but i wanted to learn what the point of having a high current amplifier was.

I have a really old technics amplifier (class a+), and i was told it was a high current amplifier, although technics no longer makes their amplifiers high current.

I also have a yamaha, which supposidly is high current.

Can anyone shed a light on this for me, and how i can tell if my amp is high current or not?

Thanks!
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Old 31st January 2005, 09:05 PM   #2
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You must look at parametres declared by manufacturer : If is there written, that load impedance can be 2 Ohm or lower, you have high current amp.
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Old 31st January 2005, 09:39 PM   #3
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Merkheth,

Manufacturers have historically stretched the "highness" of current for a given amplifier as there were no common benchmarks available.

High current is a relative term. To some it means driving a reactive 8 ohm load (as is in the case of several far east manufacturers) to the common audiophile it is the ability to drive 2 ohms without issues, to me it means driving a dead short.... So there you have it.

For most practical purposes, the Class A+ from Technics is not high current. It might be able to drive low impedances (current limiting circuits or series resistance with the load are implemented to drive low impedances) but that does not denote a high current drive, infact those implemenations actually reduce the available current.

To give you a simple answer: As a start.... Normal amplifiers should be able to drive 16 to 4 ohms without issues, to get the high current certification, it needs to drive 2 ohms with a 20% headroom for a reactive load without significantly increased distrotion or non-linear anomalies.
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Old 1st February 2005, 03:30 AM   #4
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Of course driving a reactive load requires no more current than
a resistive load of the same impedance. That does not
define "high current".

That an amplifier can drive 2 ohms is also not a good criterion -
an Aleph can drive 1 ohm, and is still not a high current amplifier.

Since no definition of "high current" exists, you can simply
judge by either the current rating of the amp or it's power into
some low impedance. Does it look high to you? Then its high
current.

Of course if it's good sound you're after, then buy something
that claims "good sound".

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Old 1st February 2005, 12:54 PM   #5
K-amps is offline K-amps  United States
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Nelson: How about we set a definition for our DIY community.

Here's a start: (others can add to it).

Med current, drives 4 ohm resistive load with 1.5x the power of the 8 ohm drive.

High current: Drives 4 ohm loads with 1.66x the power and 2 ohm loads with 1.5x the power of 4 ohms.

Very high current: Drives 1 ohm load with 1.5x the power it delivers to 2 ohm load (provided the higher loads are as good as or better than the crietia above).

Ultra high current: voltage drive stays with 10% down to 1 ohm.

Super high current: Will turn a 6 foot lamp cord into a heating element.

All these ratings should happen with thd below 0.9%, driving all channels, driven from 16Hz to 16khz (yes I do not hear till 20khZ so there you have it.)

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Old 1st February 2005, 01:02 PM   #6
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My take on high current has nothing to do with impedance. A 1 watt amp driving a 1 ohm load is not high current! I would say high current is the point when you have to be careful with wiring and parts ability, 10 amps RMS or more.
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Old 1st February 2005, 02:04 PM   #7
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Wiring and parts ability is a pre-req for any design. It is not dependant on high current alone but all design parameters . i.e. You need appropriate parts even for hi-volt low current amps. You need to ensure the insulation is such that a tube amp will not shock the heck out of the serviceman etc.

I think we do need to make it reference to loads and in this case to the standard 8 ohm load otherwise we will be blind fishermen.

I would like to think a 1 watt amp designed to drive a 1 ohm load in the context of audio is a high current amp.
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Old 1st February 2005, 04:10 PM   #8
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Now we are back to the problem again, high current is a relative term.
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Old 1st February 2005, 04:20 PM   #9
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I'd say any amplifier with a lot of stuff written on it, claiming stuff you have not got a clue of what it is, is utter garbage.
The manufacturer is not likely to explain to you what their statement means.

Yamaha in my opinion is a good example.
Yamaha amplifiers used to be highly rated in Germany, with a general liking of high frequencies.
The ones i heard ranged from $ 800 integrated to 10 k plus power amplifiers.
Each and every one delivered massive highs, sure enough to give me a headache within 15.
In those days the perfect companions for Apogee's, the ultimate ticket to drive me up the wall screaming.
Yamaha and Technics were THE brands with all the mumbo jumbo terminology, a Yamaha would be the absolute last i would use.

Strange really, they have been building piano's for over a century, really good ones.
I often wondered why a Yamaha piano does not sound like the amplifier.
But then, they would have had to market it as a "high current"
piano !

Mr Pass said it about right: good sound is possible without high current, and high current does not necessarilly mean good sound.
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Old 1st February 2005, 06:10 PM   #10
K-amps is offline K-amps  United States
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Quote:
Originally posted by jacco vermeulen
snip

Mr Pass said it about right: good sound is possible without high current, and high current does not necessarilly mean good sound.

But thats not what the thread starter asked for...

He asked if his amp was high current or not, he didnt ask (with due respect to all ) if high current sounded good or not.

Cunningham: Yes it is relative in the absence of standards, thats what i was trying to get agreed upon, seems to be folks are happy with this "vague" definition the way it is.
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