How does a high current amp work and is there any benefit of having one versus an A/B or D Class amp? Thanks.
How does a high current amp work and is there any benefit of having one versus an A/B or D Class amp? Thanks.
usually in looking at amplifiers your going to notice that alot of the CURRENT designs are leading toward class d supremacy.Originally Posted by meanman101
The sound quality is "supposedly" better in a class a/b design but this is being addressed by many manufacturers, check out the SQ class D amps by xtant. The efficiency and current draw is much higher in the d, whereas the warmth of sound is slightly degraded in the d. So you have to make some choices.
Now when you look at a high current amplifier versus a high voltage the designation is usually given in
High Current Bridges to lower ohm loads and is what was considered a cheater amp for competition. Think Orion Reds back in the day. 1/2 ohm mono stabble or 1 ohm mono. They acheived 800 watts at either of these ratings but at 4 ohms that were used by contests were rating these monsters at 50 watss. Get it?
High Voltage made its max power in the realm of 2- 8ohm woofers bridged out to 4 ohm mono or 2 dvcs at 2ohm stereo. think the old orion xtr's or blacks.
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OK so the high current bridging goes on inside the amp. Do these high current amps require more current to preform than a class D amp? I'm currently using a class X amp which is the same as a class T. I am considering getting a High Current amp but not if its going to tax my car's stock electrical system.
So these cheater amps as the ohm load is dropped start to put out real power, is that power efficient like the class D or will most of it decipitate into heat?
yep the orion hcca amps were the best i got them now. cheater amps big timmme. high current 2x25 at 4 ohms and 1x400 at 1 ohm mono. see the difference you can compete in a class of 50 watts and have 400 watts toatal god clena power.
Thanks for the responses, they clarified quite a bit of info for me. :thumbsup
Current (amps) is what powers your speakers. (Guess that is why they call it an amplifier and not a wattifier ehh?)
First you have to understand that a speaker's resistance changes with the freq. response/output. Depending on it's output, a speaker will require an amp to deliver a fluctuation of current.
A 4ohm speaker can fluctuate from 2-8ohms or more.
Assuming 50 watts continuous (RMS) on that speaker:
At 2ohms the speaker will be required to provide 5 amps.
At 8ohms its 2.5 amps. That is just for that speaker.
High quality "high-current" amplifiers will provide continuous high-current at their rated power. That is why you will find a Zapco, McIntosh, etc. 50watt RMS amp will often be described as more powerful and cleaner-sounding than many common amplifiers of the same wattage rating. The speaker is getting the current it needs to genuinely reproduce the frequencies.
A continuous supply of high-current is the only way to let your speaker accurately reproduce the frequencies you are asking it to. This is what is reffered to as good transient response.
Many will describe a high-current amplifier as one that simply can handle low impedence loads. - Yes high-current amplifiers handle difficult speaker loads, but there are a ton of 2 and even 1ohm stable amps out there that get super-hot, have peaky power supplies, and have big THD numbers. They are built to "survive" a low impedence load, but not give continuous high current.
So - watch out.
Are high current amps power hungry (more so than a quality A/B amp)?
A "quality" Class A/B amplifier would be - a high-current amplifierOriginally Posted by meanman101
A Class A amplifier is what high-current is all about, but you'll never get one in your car.
You can have a class A/B that has good continuous current output, or bad continuous current output.
A,B, A/B, D, etc. are amp "classes" that relate to transistors conducting the input, and how "faithfully" they reproduce a signal (fidelity). In car audio, you will probably only hear of the efficiency differences.
A - best fidelity - most current draw (I've never seen a class A car audio amp. They require huge amounts of power and can weigh hundreds of pounds.)
D- worst fidelity - least current draw (but Xtant claims to have a SQ class D - switching) Im not familiar with it, but IMO if it is "switching" to different topology, then it is swithcing to a different class.
You can get by with using a class D for a sub, because you dont need the all the fidelity; you only need the subsonic frequencies, at which distortion levels are harder for our ears to detect.
To put it simply:
Class A is a high-current amp
Class A/B can be a high current amp
Class B inherently isnt a high-current amp (but who sells them now anyway)
Class D inherently isnt a high-current amp (but it doesnt need to be, if used for sub-bass ~ Xtant excluded.... I guess)
now try to explain class T which supposedly gives you the low current draw of class with close the SQ of a A/B
Originally Posted by nismboy6986
Sounds like a digital amp. Lots of "other" classes popping up here and there. From the home hi-fi digital chip amps I've heard, they haven't yet reached the quality of a decent A/B. And all sound "processed", but apparently are easy as hell to build. I'm sure eventually they will take over the analogue beasts we use now.
Last edited by Lusso5; 10-23-2003 at 10:53 AM.
High current is simply a marketing term used to identify an amp that can drive loads lower than 2 ohms stereo. In general, an HC amp will always be less efficient than an amp designed for higher impedance loads. In other words, it will require more current for an HC amp to deliver 500 watts into a 2 ohm mono load than it would take a typical a/b amp to deliver 500 watts into a 4 ohm mono load.
Lusso - Digital amps don't exist yet. Exactly how would they go about amplifying a 1 or a 0? Digital is just the name some marketing departments have used to refer to the switching nature of the output transistors. Plus, it just seems to go well with "D".
Class T's are just class D's that use the Tripath chip to remove the distortion created by the switching outputs. I'm not sure about class X, but I believe it's just another marketing derivative of class T.
By "digital", I was referring to an amplifier with a digital component - a "chip". Of course there would be no fully-digital amplifiers. And anyone with basic knowledge would know you can't digitize current.Originally Posted by n2audio
To the best of my knowledge - which isn't much - the only amps using any type of chip would be the ones using tripath's technology. And that only functions as a filter. It's not part of the amplification proess.
Tripath Only? I know one other co. is in the process of making a chip/digital amp for an oem app and I've seen and listened to a few different names for home-audio over the last few years. To my knowledge - which isn't much either - the chip is a true processor and is the switch for the converter and the filter/protection. I agree its not part of the amplification process. Technically it can't be, and it isnt even wired to be. The power supply would go through the converter then to the amp section, while the processor would feed a loop, of the signals, from the amp section back through the converter - doing the filtering and switching.Originally Posted by n2audio
I understand what you are saying, but it's not exactly accurate.Originally Posted by Lusso5
I just wanted to comment, so there isn't any misinterpretation of "high power" vs "high current" modes of operation, and the different amp classes.
...that is, fidelity is only a side effect of each amp class...
...and modes of operation are not tied to amp class.
One comment - Class A amplifiers have been manufactured for the car audio marketplace - Way back before SoundStream was bought out, they had a successful Reference Class A series, and there have been a handful of others.
Also, something to ponder for a minute...
SoundStream Reference series amplifiers used to have a mode switch on them, allowing the user to select whether the amp was going to be used in "high current" or "high power" modes of operation. Later Reference models had an impedance detection circuit, that would automatically determine the ideal "mode" to be in, given the load connected to the amp...
Clearly amp classes and amp operation modes are completely independent.
It's simpler even, than what's been stated:
Amp classes are simply how the transistors switch, internally, inside the amp.
Picture an amplifier as having two transistors that work together, to produce the amplified audio signal.
Class A amplifiers are the least efficient type of amplifier.
This is because both transistors are "on" 100% of the time, both transistors are working to produce both the positive, and the negative half of the waveform.
This also means large current is flowing through them 100% of the time - even when there is no audio signal present!
A side effect of a class A amplifier [because of this] is as perfect of a waveform as you are going to get out of a type of amplifier. Cleanest sound quality, or "fidelity" as worded above.
Class A/B amplifiers are much more efficient than class A, but not nearly as efficient as class D.
Class A/B amps have one transistor working to produce the positive half of the waveform, and one transistor working to produce the negative half of the waveform. Unlike the class A amplifiers, current is not flowing at 100% through them all the time - only when each of the transistor's half of the current is present will current be flowing at that level.
A pure class B amplifier would actually have 0 current flowing through it when there wasn't a half of a waveform present for it to produce.. but this causes distortion, where the two halves of the waveform meet.
A class A/B amplifier virtually eliminates this distortion by not completely turning each transistor off, but simply reducing the current through the transistor when there isn't signal present to reproduce.
As a result, the sound quality of the class A/B amp is not perfect (as class A theoretically is), but nearly perfect, and obviously dramatically more efficient.
Class D amplifiers are the most efficient class of amplifier on the market today.
With class A, B, and A/B amplifiers, while current may (or in class A's case - not) switch on and off, there's voltage all the time, to both transistors.
Class D is interesting, because not only does power switch on and off (like the pure class B, described above), but the actual voltage switches on and off too.
So, the transistors are literally off - no voltage, no current - when their half of a waveform isn't present to reproduce. Like the class B, there's still a little distortion where the two halves of the waveform combine, but it's not as bad simply because the voltage is also switched off (as counterintuitive as that may sound).
The result of the voltage switching on and off is a dramatic reduction in heat - and that's where the huge gain in efficiency comes from.. current isn't being wasted burning up into heat.
Now, amp modes of operation are quite different...
And as I mentioned - as with the old SoundStream amps - are completely independent of amplifier classes.
It's really a simple thing though: how much current must flow through the amplifier and speaker, to produce the rated power of the amplifier.
Since Power = Voltage x Current....
1000 watts could be produced by a 100v source, and only 10a of current flowing..
Or it could be produced by a 20v source, and 50a of current flowing.
Same end product - same power level - in either case.
Typical "2 ohm stable" class A/B amps aren't stable to 2 ohms because there's some impedance "thing" in the amp... it's because the load on the amp causes a certain amount of current to flow:
Voltage = Current * Resistance.
As you reduce the resistance, you need to increase the current, if voltage is to remain a constant.
And with a car amplifier, the voltage essentially remains a constant (assuming a sine-wave, constant signal... it'll fluctuate with music).
So really, "high current capable" amplifiers (or amplifiers operating in "high current" mode) are those that are stable down to low impedances...
They are amplifiers whose componentry can withstand higher current flowing through it.
While "high power" mode amplifiers are those that are still designed to put out higher power levels - but at higher impedances (2 ohms and above), where the actual current flowing through the amp will be inherently lower.
...and ANY class of amplifier, can be designed to be a "high current" or "high power" type of amplifier.
Last edited by geolemon; 10-23-2003 at 10:23 PM.