|   High current amp | victord
Nov 11, 2003 4:34 AM | | Hello fellows. I'm setting up a hometheater system which can also provide enjoyable stereo performance. I'm quite up-to-date on the hometheater side of it, but am sorta clueless in the stereo department. Lots of people have told me to look for a "high current" amp, and not how much wattage it can produce. So my question is : how do I do that? How would I know if an amp is "high current"?
I appreciate any input. Thanks.
On the side note: I have the Def-tech BP3000TL as my main speakers. |
| re: High current amp | FLZapped
Nov 11, 2003 7:03 AM | | This has been discussed at length recently. A search should help you find the thread.
Basically, that is more marketing terminology than anything useful.
-Bruce |
| re: High current amp | Mr Peabody
Nov 11, 2003 9:20 AM | | First of all, anyone who tells you "high current" amp design is just marketing has no idea what they are talking about and lacks experience with any audio gear of substance. They shouldn't be advising anyone on a subject they have no knowledge of.
High current amps give you better control of the speaker's drivers, especially the woofers. The bass will be tighter and have more slam. More importantly high current amps can handle lower impedances, impedance swings and difficult speaker loads much better.
You can hear this for yourself. Go to a store that carries Onkyo, which is probably the best high current design in mass market receivers, and A/B it to a Pioneer, JVC or another such brand. You should be able to hear the difference. I was with someone looking at receivers and the little Onkyo 48 watt receiver killed a Pioneer 100 watt in comparison. This isn't just marketing. Something made it better, it was the amp design. Unfortunately, there are manufacturers who blurr things by claiming to be something they aren't whether it be "high current" or "24/96 sample rate" or whatever. How to tell is a good question and I don't have a definitive answer. I would say if an amps specs don't specifically say high current, they aren't. And those that claim to be, you have to rely on their reputation and some on dealer recommendations as to whether they do what they claim. That's why it's important to try equipment out at home before you buy, if possible. Try telling the engineers of brands like Krell, Levinson, Bryston or Arcam there's no such thing as high current design. There are several others as well. If these amps weren't high current there's no way they could drive some of the inefficient speakers that are on the market. When I was in the business we used to sell the Infinity Kappa series, to Kappa 8 & 9's had multiple 12" woofers and were prone to radical impedance swings. This killed a few of our amps trying to drive them because they didn't have the current. A guy I know of has an old Onkyo integra that drives the Kappa 8's great. It's the high current that allows it to do so.
High current design is better contrasted in car audio. What do you think allows brands like Rockford, Precision Power, Orion or any other American made "high current" amp to be 1 ohm stable? Why are these amps so desired for subs? The high current allows you to load one amp up with multiple woofers and have it slam the mess out of them. Non-high current car amps are less taxing on your cars electrical system but they would go up in flames trying to drive the same load. Also, in car and home, you will notice this type of high current performance costs more.
High current amp designs exist, they can be demonstrated. If I knew what type of amp you were looking for I could give you a suggestion of a high current amp to listen to. |
| re: High current amp | Kursun
Nov 11, 2003 11:37 AM | | I very much agree with FLZapped that it is more marketing terminology than anything useful.
Generally it is used to define amplifiers with good and solid power supplies and output stages.
The easiest way to spot such an amplifier would be to compare its output into 8 and 4 ohm speakers. Compared to its output into 8 ohms, if its output is almost doubled into 4 ohms, you may say this amp is "high current".
But in HT circles you may be lucky to find any receiver that has its power rated for 4 ohm speakers on its specification sheet. |
| re: High current amp | victord
Nov 11, 2003 2:01 PM | | Thanks a bunch fellows.
I forgot to mention that I was looking at a separate amp to drive my hometheater/stereo system, not a receiver. I believe it's rather rare or/and expensive to find a receiver which would perform well in both modes. I'll probably start with a five-channel amp, and then add another two-channel amp for the main speakers. So far, I'm very interested in the Rotel and Sunfire multichannel setups.
I understand that my main speakers (BP3000TL's) are very sensitive (92db) and would benefit little from an amp that can drive difficult loads (high-current amp), but I want to start with the most capable amp that I can afford.
As of now, do you guys know any capable five-channel amps for roughly $2000-3000? |
| There is no such thing | Norm Strong
Nov 12, 2003 12:09 PM | | If you think there actually is a "high-current amp", what is the maximum current of, say, the Onkyo referred to above? How does one sort amplifiers into high-current and not high-current?
There is no way, since amplifiers are voltage sources, and they put out whatever current is necessary to produce the desired power output.
I have a low opinion of any manufacturer who advertises its amplifiers (or receivers) as being "high current." I probably wouldn't buy their stuff. |
| There is no such thing | skeptic
Nov 12, 2003 1:14 PM | | I think that there are some amplifiers which can deliver inordinate amounts of current for short periods of time. This probably stems from huge capacitors in the power supply which have sufficient charge to dump quite a bit into a load before they are significantly depleted. I think some Harmon Kardon models were rated to deliver 40 amps!!! Obviously they can't do this for very long. 40 amps equals 6400 watts into a 4 ohm load and 12,800 watts into an 8 ohm load. It wouldn't be long before the output transistors fry if the fuses don't blow or the circuit breaker doesn't trip first. Is this a useful performance capability? Maybe sometimes it is, maybe a lot of times it isn't. The industry tried to differentiate the way amplifiers operate reproducing music from the way they are tested with pure sine waves in laboratories by introducing concepts like IHF (Institute of High Fidelity-remember them?) power, music power, dynamic headroom. But a horsepower race in the 60s and 70s caused the FTC to put an end to all that and set one uniform standard for rating audio amplifier power. So when you buy one, you may be comparing somewhat different maximum capabilities even when the nominal power output, bandwidth and distortion are the same. |
| re: High current amp | kevyy
Nov 12, 2003 2:13 PM | | It's a good idea to keep an amp's current capabilities in mind, amp manufacturer's with high current capabilities inclue NAD, Rotel, Adcom, Outlaw and ATI. The thing is though, unless you are planning on gettin speakers that are exceptionally cruel to an amp like Martin Logan or Theil, extreme current capabilities may not be needed for your purposes, in which case I would suggest weighing overall sonic characteristics and cost with current capabilities. By the way, one quick measure to roughly judge an amps current supply is to pick is up, transformers are heavy, and high current amps are heavy also. |
| re: High current amp | victord
Nov 13, 2003 7:15 AM | | I guess there are two contradicting camps on this issues. Is it because it's more of a subjective matter, depending on the individual, and not so much of a technical cause-and-effect thing?
Are there any correlations between a "high-current" amp and the sound qualities, as in neutrality, frequency separations, and "tightness" of the bass? |
| re: High current amp | kevyy
Nov 13, 2003 12:06 PM | | To answer youre question, well, it all depends. I think there IS generally a correlation between sonic characteristics and current supply, but one has to look at the interdependent relationship of the speakers and the amp. A lower current amp will tend to have less "control" over the speakers, and will have a woolier, less dynamic sound. This is most evident in the bass region because woofers tend to show lack of control the most and producing large amounts of bass tends to demand alot of current from the amp, but inadequate current will also manifest itself in poorer, more boxed in and more distorted treble also. BUT, i've heard monster amps that sounded muddy with poor dynamics, and it wasnt a current issue at all, its just what they sounded like, and I've heard low power amps sound very dynamic because they were matched with speakers that were very efficient and easy to drive (high impedence). There is also the issue of an amps "stability" when it comes to driving difficult speaker loads, which has to do with how the amp and the current supply are designed, apart from the sheer number of peak amperes it can crank out. This leads back to the issue of speakers, which is one half of this issue. A speaker like an Avant Gard duo is so efficient it needs almost no power or current to crank alot of sound out. Speakers popular with tube enthusiast will tend to be efficient and easy to drive. On the other extreme, you have big Martin Logans and Thiels which would make mincemeat out of a typical amp, and people hook up huge Krell monoblocks and the like to drive them correctly. It would be rediculous to hook up a 1000w ultra high current amp with and ultra efficient speaker, just as it would make no sense to try and drive a Martin Logan with a 3w tube amp. One pretty much hard and fast rule is however, very deep, very dynamic, and very tight bass REQUIRES lots of current, no matter how you slice it. THIS DOESNT MEAN you have to have this in your main amp though, if you have an excellent subwoofer with its own amp in it, you may be able to get by with less for youre main speakers. If bass performance is really important to you though, i would tend to recommend higher current amps, as long as their sonic characteristics matched youre system well. Tube enthusiast TEND to care not as much about an amps current abilities because they are more interested in a tube amps midrange and treble qualities, whereas people interested in the last word in bass performance tend to favor large, very full range main speakers which will greatly benefit from a higher current amp. What it all comes down to though, there is no single number, be it watts per channel or peak aperes, that will tell you how an amp is going to perform in your system, there is no substitute for doing research and listening to the amps you are interested in. |
| Kevy-Kev | Mr Peabody
Nov 13, 2003 9:07 PM | | It's good to know that at least one other person on a supposed "audio" forum knows what they are talking about. I am not technically enough versed to explain how the high current design functions but I know for a fact it exists. It's more than just a bank of capacitors as well. Proton, who basically ripped off NAD, had power amps with "Dynamic Power on Demand" circuitry. This was a bank of capacitors that allowed the amp to deliver about 4 times it's rated power during short bursts. This particular amp died a quick death trying to drive the Kappa 9's I referred to in my earlier post. I do know that the high current amps do have in common powerful, usually Toroidal, transformers. On the other hand Dynaudio has some monoblocks, which I believe cost in excess of $100k, that can run for 24 hours after being unplugged. That's capacitance! I would hope that those who are ignorant to the fact of high current amp design would at least keep an open mind to go out and see if the things I say are true. Just because one hasn't seen something don't mean it doesn't exist.
I agree with what you said about "high current" is not equivalent to good sound. I have some Adcom gear where the power amp is high current and I have definitely heard cleaner amps. It's a shame that one of them here says they wouldn't even buy equipment claiming to be "high current" because, unless it's tube gear, most high end gear has adopted and embrace this design. Any big amp company you can think of Krell, Levinson, Bryston, Proceed, and if I'm not mistaken PS Audio's ad said "high current". |
| Kevy-Kev | kevyy
Nov 14, 2003 7:54 AM | | 24 hours????? that sounds really excessive to me, then again, 100k should buy you excess. In the real world, lol, I had an ATI 1505 that ran for several minutes after being unplugged. To try to bring this discussion down to real world advice, i can say that living with two types of speakers, Signet 280b/u s and NHT 2.5is and various amps was enlightening as far as amp/speaker current relationships. Sonically they weren't all that diffrent, I prefer the Signets and its the pair I still own, but I would say they were in the same class. They were about the same as far as efficiency, but the Signets are very easy to drive, the NHT's were cruel (dip below 2ohms in the bass region). I have a huge, heavy old Sansui integrated amp with a big power supply, but could only drive the NHT's to moderate levels without the bass falling apart, whearas it sounds glorious and wide open with the signets. Typical recievers made a tiny and ugly sound in the NHT's, but had no problem with the signets (well, still sounded ugly but that had nothing to do with the speaker). The beastly ATI 1505 drove both of them with no problem. Insterestingly, an NAD 761 drove the NHT's with no problem. This leads back to system matching, in looking for an amp, what are youre priorities as far as the whole system goes? Bass performace? trasparency? warmth? imaging? it all matters as far as overall tradeoffs go. |
| Kevy-Kev | Mr Peabody
Nov 15, 2003 6:04 PM | | My goal is to find the system that comes the closest to sounding like real musical instruments. The system that comes the closest, that I can afford, is Krell CD player and amp driving Dynaudio Contour t2.5's. Krell delivers the dynamics, impact and detail of live music. The 2nd closest I've experienced was Audio Research, tube gear, driving Martin Logan Requests. The mids & vocals had a presence that was haunting, it seemed so real. But this system lacked the bass definition and slam of the AR system and also didn't have the dynamics. That was a lot due to the electrostat style of the Martin Logan. Not a criticism, it was just different and I couldn't have it both ways, unfortunately.
I couldn't set a priority for one particular characteristic of a sound presentation. I want my system to cover the whole frequency or musical range as well as possible. You know what I mean? What good is slamming bass without a good high end to balance it out? And if you achieve that, what good is it without the detail of midrange and vocals? But, the bottomline is, you, or me, the listener, has to enjoy it. |
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