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High Current Amps

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Posted on April 10, 2022 at 10:34:26
itolduso1000timesb4
Audiophile

Posts: 190
Location: Canada
Joined: March 7, 2018
That was a concern a decade or more ago. I have not seen much talk about the technical concern that a great amp had to be high current.

Not exactly losing sleep over this particular issue. Has it disappeared because most power amps have high current or did it fall by the wayside from lack of interest?


Have newer switching designs made it a non-issue?


Or is it simply the ad copy changed because of a lack of interest in such notions?

 

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RE: High Current Amps, posted on April 10, 2022 at 11:37:14
6bq5
Audiophile

Posts: 3771
Location: SF Bay
Joined: August 16, 2001
High Current amps were in great demand when there were lots of inefficient speakers that needed lots o'power to come to life-
now that there are more options on the efficiency front - and fewer speakers coming to market below 90dB @ 1watt/1meter - the issue has become less necessary-
That said - there is still a huge market(?) for them driving Maggies....
Happy Listening

 

RE: High Current Amps, posted on April 10, 2022 at 12:36:10
Story
Audiophile

Posts: 6239
Location: NJ
Joined: December 11, 2000
high current was a fancy buzzword used to describe solid state amplifiers that could deliver the higher currents called for in lower impedance speakers like 4 ohms instead of 8 ohms that were the usual.

In days of yore, you'd commonly see 50 watts rms/8 ohms, 75 watts rms/4 ohms both channels driven. It was rare to see an amp that could double its power at half the impedance.

As usual you have to see specifications and what they are referenced to, and the newer digital or Ganfet's are no exception I would think

edit - it's almost all in the amp's power supply capability



 

Don't forget cost shift, posted on April 11, 2022 at 06:19:27
airtime
Audiophile

Posts: 11135
Location: Arizona
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Building a GOOD power supply is NOT cheap. Manufactures wanted to get away from building big expensive power supplies. Enter the Class D - power for pennies.

Believe me, if they could sell you a current amp that can make the profit margin they are making on Class D, right now we would all be chattering about current amps and not class D amps.

Addendum: I really have to proof read more often.

 

RE: High Current Amps, posted on April 11, 2022 at 06:27:56
cawson@onetel.com
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Posts: 2060
Joined: September 27, 2004
I go more for Storey's description - nothing to do with power (in terms of watts) as that's another matter, but in terms of the amp's ability to deliver undistorted juice to low impedance speakers.

I had KEF Reference 107 speakers 20+ years ago (90 dB but only 4 ohms) and on reflection, probably never heard them at their best because my amps (AVI S2000MM monos) weren't entirely suitable. Not that they weren't powerful enough (they had plenty of that for 90 dB speakers), but more they were not entirely happy with the speakers' low impedance - nominally 4 ohms.

My present speakers are 107 dB and 18 ohms nominal, so little for any amp to worry about. This means I can choose an amp based solely on how it sounds through my speakers in my particular room.

 

Power for Pennies.... except when its not, posted on April 11, 2022 at 09:55:07
AbeCollins
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You make a valid point about Class D "power for pennies". While that is generally true along with fantastic bang for the buck and excellent sound, it doesn't explain the mega-buck audiophile Class D amp. You know, the ones where the manufacturer boasts about applying their own special secret sauce in marketing hype cleverly disguised as technical whitepapers.... so they can bamboozle and charge mega-bucks.

The real heavy lift engineering is done by the Class D module manufacturer, not the amp assembler. Some D module manufacturers even provide ready made switching power supply modules. Stuff these in a pretty case with a little tweak and charge 10 grand. Don't you love it!

If I were to pay near 10 grand (US) and up, I would buy a traditional A or AB amp with a massive power supply from a reputable brand like Pass Labs or similar. But a Class D amp in the 10 grand (US) range? I laugh and shake my head.

I'm running a pair of Class D monoblocks that sound fantastic and are priced around $3K/pair MSRP but I got mine for around $2K direct from manufacture with trade-in.

Class D SHOULD offer fantastic bang for the buck but when some audiophile brands charge mega-bucks for Class D you know they're just gouging the buyer. A pretty case and slick marketing will bamboozle many audio jewelry buyers.


 

RE: Power for Pennies.... except when its not, posted on April 11, 2022 at 12:03:43
Ralph
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Location: Minnesota
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You make a valid point about Class D "power for pennies". While that is generally true along with fantastic bang for the buck and excellent sound, it doesn't explain the mega-buck audiophile Class D amp. You know, the ones where the manufacturer boasts about applying their own special secret sauce in marketing hype cleverly disguised as technical whitepapers.... so they can bamboozle and charge mega-bucks.

The real heavy lift engineering is done by the Class D module manufacturer, not the amp assembler.


Some of your hyperbole is real, and some isn't.

You can get inexpensive class D power but often its in chip form and distortion is 10% at 'full' power.

The more expensive amps that actually use a module like Icepower or Hypex tend to also have better distortion specs!

We use a toroid power transformer in our class D; to do so and have the amp survive shipping we had to make the chassis fairly heavy- out of 3/16" aluminum. So the amp is a bit heavier than you'd otherwise expect- nearly 14 pounds. To make a chassis like that in 'small' quantities you do have to pay for it- and then finish it; that all can be a bit of an investment.

We designed our own module. All the engineering was done in-house. All these things tend to be more expensive, especially if you build the amp to last.

 

RE: High Current Amps?, posted on April 11, 2022 at 12:13:17
Ralph
Manufacturer

Posts: 4384
Location: Minnesota
Joined: April 24, 2002
I love how 'high current' means something other than the only thing it can mean, which in this case is an amp can make a certain power into a certain impedance.

Current cannot exist without voltage and vice versa. Together they are called 'Watts'.

A lot of times the 'current' advertised is actually how much current is present when the power supply is shorted and nothing to do with the output section at all, other than an extra bit of capacitance in the power supply.

For example, I've seen '80 Amps' advertised. If you give the amp the benefit of the doubt, and assume that into a 1 Ohm load it can make 80 amps, that means that into 1 Ohm it can make 6500 Watts! Power = Current (squared) X Resistance (in this case 1 Ohm). If you increase the resistance you see the power going up quite a lot. I don't know of amps that powerful- for that matter I don't know of a 6400 Watt amp either!

So that means a current value like that means something else- and that 'else' is the current when the amp's power supply is shorted. Briefly.

Let's say you need 400 Watts into a set of Maggies to really make them sing.

400 Watts = Current (squared) X 4 Ohms

solving for current we get 10 Amps. That's really not that much current as these ads I've seen go, but if you want 400 Watts into 4 Ohms that's the current.

It might be that too many manufacturers have been called on making outrageous claims that can't possibly be true. Is that why we don't hear about this so much anymore?? :)

 

RE: High Current Amps?, posted on April 12, 2022 at 05:59:34
Utley1
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As usual so clearly stated. Thanks Ralph ; UT

 

RE: Power for Pennies.... except when its not, posted on April 12, 2022 at 15:39:03
John Elison
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> While that is generally true along with fantastic bang for the buck and excellent sound, it doesn't explain the mega-buck audiophile Class D amp.

In my opinion, there's little justification for mega-buck anything in audio except for the fact that some people are willing to pay these ridiculously high prices.

I've spent my whole life searching for, and often finding, reasonably priced high-end components. I need fairly hefty power amplifiers for my Thiel speakers, but I can no longer afford appropriate class-A/B amplifiers. Fortunately, I discovered that PS Audio produced some outstanding sounding class-D amplifiers and I bought a pair. Still, they weren't exactly cheap at $6,598 a pair. However, like Abe, I was able to negotiate a discount and I paid only $4500, but the ones I really wanted were the Parasound class-A/B monoblocks at $17,998 a pair. Even PS Audio makes a pair of class-A/B monoblocks for $16,498. These monoblocks are only half the power of my class-D M1200 monoblocks, yet they're more than twice the price.

Fortunately, I'm overjoyed with the sound of the PS Audio M1200 class-D monoblocks. These things really sound spectacular.

I'd been using a Parasound Halo A21, which is no slouch. It's rated at 450-wpc into 4-ohms but it appeared to produce about 750-wpc on 1000-Hz tone-bursts into my Thiel CS3.7 speakers. The Parasound Halo A21 was just beginning to clip at 50-volts RMS at 1000-Hz. The impedance of the Thiel's at 1000-Hz is about 3.3-ohms. Nevertheless, the improvement in sound quality with the PS Audio 1200-watt class-D monoblocks was absolutely stunning. I'd never heard such dynamic contrast. In fact, I even wrote to PS Audio asking them if the M1200's contained dynamic range expanders. Of course, they didn't, but they sounded so much more dynamic than my Parasound Halo A21 that I was flabbergast. The M1200's also sound smooth and pleasing in the highs with a very natural and transparent midrange. They didn't sound anything like my old Crown XLS-1500 class-D amplifier. Then again, they weren't that cheap, either!


.
.
1000-Hz tone-bursts from my Parasound amplifier into my Thiel CS3.7 speakers



 

Can any 100 watt amp double down to 400 watts at 2 ohms?, posted on April 12, 2022 at 17:51:11
Rod M
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My old Classe DR-9 is touted to be a high current amp and it surely can handle difficult loads. The specs claim 100 watts at 8 ohms, 200 watts into 4 ohms and 400 watts at 2 ohms.

While that 400 watts may be true, I recall that a review measured it at 150 watts into 8 ohms. In theory, the DR-9 seems to have the power supply with 4 coke can sized caps to support the required 14+ amps. It strikes me that marketing department went backward from the 2 ohm spec while under rating the 8 ohm power resulting in perfect specs.



-Rod

 

No, not all can., posted on April 13, 2022 at 11:16:28
Ralph
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Posts: 4384
Location: Minnesota
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400 Watts into 2 Ohms is about 14 Amps.

The output section has to be safe with that, the heatsinks have to be adequate for that, and finally the power supply has to be able to provide the current without collapsing the voltage.

The point here is that as long as the amp can make the current into the load such that the power is made, you're 'golden'.

 

High end audio isn't driven by price, its driven by intention., posted on April 13, 2022 at 12:16:06
Ralph
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Location: Minnesota
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Sometimes that's cheap (Radio Shack made some products that were definitely high end) and sometimes its not.

Its also important to keep in mind that economy of scale plays an enormous role.

 

RE: Suitable output section, heatsinks, and power supply, posted on April 13, 2022 at 13:04:57
peppy m.
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This was what the term "high-current amp" was supposed to signify back in the day. The term was not necessarily meaningless but it may have been somewhat ill-defined.

 

The problem is many manufacturers advertised outrageous 'current', posted on April 13, 2022 at 13:22:16
Ralph
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Location: Minnesota
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which had nothing to do with the actual power the amp made. I gave an example earlier.

 

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