Is my amp "High Current"?


Hi, I own a McCormack DNA 0.5 amp that has been upgraded to rev. A at SmC Audio. I read about speakers benefiting from using a high current amp, and was wondering if mine was considered to be one.

Thank you.
koestner
yes it is
Yes, McCormack amps are high current design.

Steve at SMc Audio (where mods were done) will gladly talk to you. You have a very NICE amp there!! Have fun!!! Only thing I like better is tube amp, but for solid state McCormack is great!!
What is the definition of "high current" amp?
High Current is most commonly used to describe an amp with the ability to deliver increasing amounts of current into low impedence loads. The ideal amp would deliver twice the current as the load halves. For example, 100 watts into 8 ohms and 200 watts into 4. Many designs are able to deliver brief peak amounts of current far in excess of their rating, but can't sustain current demands for very long.
You can check the specs on the amplifier for "amps" no joke. That tells you if the peak current is high lets say 40 amps but big SS are higher. Whereas the cheap 5 lb 100wpc uses a power transformer delivering 100 volts which is all the amperage it's going to get vs, a 1kilo volt transformer -now the amp weighs closer to 100 lbs more - and has 1,000 volts to draw on. That's why there is a warning not to try to service it yourself "Lethal Voltage". The advantage is that you have head room for demanding passages.
Mechans, confusing volts with amps and also throwing lbs for good measure renders your answer less than helpful.
Respectfully, Bob p.
One easy definition of a 'high-current' amp, as Monty mentioned, is one that has a continuous-power rating of double its output power as the load halves its impedance. This test is rather strenuous, and many amps just can't do it. The key word here is 'continuous'. For a short-enough period, any amp can double its power when the load halves. To be able to pass twice the current continuously, almost ALL parts in an amp that pass current, and that's at least all the power supply and active circuirty, have to be larger and the entire system has to be able to dissipate the heat*. A few amps are built with large-enough parts that that they'll double output again into 2 Ohms, and fewer still will double again into 1 Ohm. I had a Lazurus HA-1 stereo poweramp that was rated 50WPC into 8, 100WPC into 4, and 200WPC into 2.

So maybe one definition of 'high-current' is having a continuous-power rating into 4 Ohms of double the 8-Ohm power. Others have more-strenuous definitions.

* This requirement is what prevents many multichannel amps such as my Outlaw 770 from doubling its power continuously--each amp module is so close to the next, there just isn't enough airflow over each to remove the additional heat created by the doubled current flow.
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Dear Koestner: +++++ " I read about speakers benefiting from using a high current amp " +++++

It benefit if the electrical speakers impedance curve goes really down, say below 3-4 Ohms. Along with this HC desired factor is a desired too low output amplifier impedance, say below 0.1 Ohms.

Now if your amplifier meets what Montytx posted then it is a HC one.

Regards and enjoy the music.
Raul.
I think y'all are confusing power with current.

1. Watts are a product of volts times current
2. So 200 watts could equal (A) 1V x 200A or (B) 200V x 1A
3. When impedance (ohms) drops, and the speaker wants lots of watts, you could give it A or B, but an electrostat would prefer A because it's a current hungry device, not a voltage hungry device like a cone driver which prefers B.
4. Tube amps (generally speaking) have more amps in each watt while SS amps have more volts in each watt,
5. Ergo, a 35 watt tube amp may be capable of delivering the same amount of CURRENT as a 200 watt SS amp.

So if it's current you're after, a good tube amp will do it -- if it's voltage you need, you'd be happier with the SS amp. The thing is, that unlike stats, cone drivers generally don't drop significantly in impedance as the frequency rises, however they do call for more power (in the form of volts not amps), when controlling (damping) large woofers.
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Wow, That was an excellent response. I finally saw the light bulb above my head go on. I only hope I can generate the watts to keep it lit :-)

Thank you. You really did explain that well.
"High Current is most commonly used to describe an amp with the ability to deliver increasing amounts of current into low impedence loads. The ideal amp would deliver twice the current as the load halves. For example, 100 watts into 8 ohms and 200 watts into 4."

Aren't Mcintosh some of the highest current amps on the market, and don't they claim their amps deliver the same power at 2, 4, and 8 ohms?
"3. When impedance (ohms) drops, and the speaker wants lots of watts, you could give it A or B, but an electrostat would prefer A because it's a current hungry device, not a voltage hungry device like a cone driver which prefers B.
4. Tube amps (generally speaking) have more amps in each watt while SS amps have more volts in each watt,
5. Ergo, a 35 watt tube amp may be capable of delivering the same amount of CURRENT as a 200 watt SS amp.

So if it's current you're after, a good tube amp will do it -- if it's voltage you need, you'd be happier with the SS amp. The thing is, that unlike stats, cone drivers generally don't drop significantly in impedance as the frequency rises, however they do call for more power (in the form of volts not amps), when controlling (damping) large woofers."

Oh my. That's exactly backwards, Nsgarch.
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Jeffreybehr, please explain what's reversed. I'll fix it if it's wrong.
Here is what is wrong, Nsgarch. Electrostatics do not demand high current, but are voltage driven. In fact, all speakers respond to the voltage applied at the terminals, depending on their sensitivities. that is why sensitivity is stated as sound output (db)/2.83V into 8 ohms (which is 1 watt).
Thus, if a speaker outputs 90db at 2.83V input and it is an 8 ohms speaker (at that frequency) and we expect 90db at the same 2.83V input, but at a different frequency which is at 4 ohms, then the power requirement will be double, therefore the amps double.
Electroststics are essentially voltage driven devices, i.e. the membrane responds to the varying voltage of the stator panels. generally 'statics' don't demand a lot of current. Dynamic speakers also respond to voltage, but due to their drive systems, they also need power, thus the need for more current at lower impedences, therefore more amps. Note, if the amplifier is incapable of supplying the necessary current for the power demand, it is the voltage that sags, thus the output from the speaker 'sags'.
Tube amps are generally not great current producing devices beyond their power limits into specified loads, but their stability with voltage makes them a good marriage with electrostatics. High current capability SS amps do much better with varying impedence dynamic speakers than tubes, usually. That is the part that you had reversed, I think.
Respectfully, Bob P.
Inpep, you state:
Electrostatics do not demand high current, but are voltage driven.
Is that your opinion, or do you have a reference for that 'fact'?

Electroststics are essentially voltage driven devices, i.e. the membrane responds to the varying voltage of the stator panels.
Except for the Quad 57, all other commercially manufactured electrostats have a constant, DC, high-voltage/low-amperage potential in the stators (supplied using AC from the wall) and a varying potential in the moving membrane which is derived from the audio signal. They are NOT voltage *driven* since there is no work for the voltage to do, ie, no electrons for it to MOVE between two points. Only electroSTATIC forces are created. An electroSTATIC speaker is simply a big, flat, capacitor. As I'm sure you know, a given value capacitor passes more and more signal (alternating CURRENT) as the frequency increases -- which is why the impedance (resistance) of stats GOES DOWN AS THE SIGNAL FREQUENCY GOES UP ;-)

For a freally clear expanation of circuits and how they work, I highly recommend this site:
http://www.allaboutcircuits.com/vol_1/index.html
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Adman227, your quote (from Montytx) is why I said I thought there was some confusion over power vs. current. Again, I recommend this site:
http://www.allaboutcircuits.com/vol_1/index.html
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Nsgarch, you could have used a better example than an ESL. How about a B&W? ESLs are neither looking for current or voltage- they are expecting constant Power. That is why tube amps generally sound better on them too, so long as they are able to make the constant power into all frequencies.

The idea of constant voltage appears to have nothing to do with the way we hear. Its odd how it keeps showing up.
Nsgarch, I am aware that the impedence goes down with rising frequency, but that does not necessarily mean that the power requirement and hence the current demand goes up. usually, the amount of high frequencies is very low and therefore the voltage necessary to move the membrane is less also, therefore not much power necessary to do the job. since, as you stated, there really isn't really much work done by these 'capacitors' not many amps are necessary.
Again, as you say, it is the varying voltage on the membrane between the stators that cause the membrane to move, thus making sound. Tht is what i mean by 'stats are voltage driven'. Not much energy is used through that action. Most of the energy is used in maintaining the constant voltage in the stators through their circuits.
Inpep, voltage is defined as the POTENTIAL to do WORK by MOVING electrons from one point to another. In an electrostatic speaker, electrons do not move across the gap between the membrane and the stator(s) unless of course the two happen to touch, or the current builds up to the point where there is and electrostatic discharge -- arcing -- in which case the speaker is damaged by a hole being burned in the membrane. The membrane's movement is generated solely by the (alternating) attraction/repulsion of the charged surfaces, nothing else.

A constant high voltage (potential) is maintained on the stators, generally on the order of 20,000 volts. You don't get a shock because there's virtually no current associated with it, no capability of those volts to push any electrons through you ;-) The membrane has a constant potential as well, but it changes from + to - at whatever frequency the signal dictates. The faster the polarity alternates, the more current is required. That's how AC works, only in reverse. It produces current by CHANGING polarity, and NOT by pushing electrons through miles of wire (which BTW is what we'd have if Westinghouse hadn't prevailed over Edison ;-) ANYWAY, Ohms Law says I = V/R. Current = Volts divided by Resistance. Higher frequencies require more current to produce them (just the opposite of an AC generator) and from Ohms formula, if I gets bigger, and V stays constant, then R must get SMALLER. And there you have it. Yes, the amp must provide more power (watts) at higher frequencies, but only as much as necessary to increase the CURRENT to the membrane. The membrane doesn't need volts, because very little WORK is being done to move it. P (watts) = I (Current) x V (Volts) So if an amp can deliver watts which consist mostly of current instead of volts, that'll be just fine for a stat. In most (high or low wattage) SS amps, the current they deliver is rather a smaller proportion of each watt. Whereas, a tube amp's watts consist of a rather higher proportion of current in each watt. So if all you're after mainly is current, why not choose a lower wattage tube amp? And you get the bonus (IMO) of tube sonics to boot ;-)
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To me the "high-current" label is just marketing hype.

Chris
Nsgarch, itm is the speaker that 'decides' what it needs to produce sound, not the amplifier.
The electroststic speaker's membrane moves in concert with the alternating Voltage with which it is charged, just as you said. And, as you said, not much energy (watts) is used during that action. Not much more energy is necessary to produce the high frequencies (in fact less is usually necessary due to the low volume of those frequencies)in spite of the lowered impedence, thus no real need for 'high current' capability. The biggest problem for the amp on electrostatics is ringing or oscillation due to the highly capacitive nature of the load, not current draw.
Inpep, it's OK to think of it this way I suppose:
it is the speaker that 'decides' what it needs to produce sound, not the amplifier.
so long as it's understood that what is meant by "decides" is whether the speaker presents an electromagnetic load to the amp, or an electostatic load to the amp. If the load is electomagnetic, the amp will be required to supply voltage, but at a more or less constant current. If it's electrostatic, the amp will be required to provide current but at a more or less constant voltage.

So lets say you have a 40W tube amp, and that at 40 watts output, you're getting the product of 10A x 4V (= 40W) Now lets say you have 100W ss amp and that at 100 watts output you're getting the product of 10A x 10V (= 100W).

So both amps can deliver 10A. But the tube amp can deliver 10A at 40W output, while the ss amp delivers 10A at 100W output. If you need big voltage to provide power to drive an electomagnetic load like a big woofer, the high output ss amp makes more sense because it delivers 10V at it's max. 100W output. The toobie only delivers 4V at its max. 40W output. But if you're driving an electrostatic load, then the tube amp makes more sense because you can get the same current at less than half the power output of the ss amp. And you're gonna say, "So what, you're still driving the stat with 40W instead of 100W, so it won't be as loud as with the SS amp." However, that's not true if you're delivering the same high current (not voltage) the stat needs to generate strong electrostatic attraction/repulsion. In fact it is this property of tube amps which leads to the (erroneous) statement, which you may have heard, that "Tube watts are more powerful than SS watts." This is of course bullpuckey. I just depends what kind of watts your speaker "decides" it needs ;-)
Nsgarch, if a speaker needs big voltage (say 40 v) to drive it to a certain level then that is what it needs, and the subsequent power that it needs will follow if the amp can supply the current. The tube amp will give it that voltage (40V) and what ever current is necessary up to its power limits. If the speaker needs 40V and 100watts to produce that certain level, then the amp will supply the 2.5 amps x 40 Volts quite easily. The 40V requirement and 100watts requirement are fixed by the speaker. The amp can't decide that, because it can't produce 40V but can supply 25V at 4 amps thus 100watts, it will do that. As long as the voltage demand and power demand are within the tube amp's specifications, the voltage will not be be dragged down by the load. This not the case with SS, unless it is capable of increasing its amps into lower loads in order to make up for the increased power demand. That is why dynamic speakers are considered more 'current' driven.
At any rate, as you have said there is not much current involved in electrostatics, therefore it is varying Voltage that drives them. Electrodynamics, due to the varying current demands along with the varying voltage driving them, are more current driven. This the opposite to what you have contended.
Inpep, you still appear to misunderstand the the terms voltage, power and current, and more important, how they relate to each other. If you will spend some time with this site:
http://www.allaboutcircuits.com/vol_1/index.html
until these relationships are second nature, you will understand what I am trying to say.

Speakers (with voice coils, and primarily woofers) need power (watts) if it takes work to move them (power = voltage x current.) BUT, they need those watts (power) to come primarily from a larger reservoir of voltage since voltage drops as power is consumed. An ESL needs power too, but from a reservoir of current. As the frequency rises and the impedance drops, yes, they need power too, but they are going to draw current out of those watts to maintain the strength of the static charge on the membrane. They don't need volts for that!

All amplifiers supply BOTH increasing voltage AND current as the volume (input signal to the amp) is increased. The maximum output of the amp (in watts) is a product of its max. voltage times its max. current, and those two can be in ANY proportion. But with tube amps, current is usually in larger proportion to voltage than in ss amps where it's the reverse. I just don't know how to say it any more clearly.
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Nsgarch, this discussion is getting nowhere precisely for the reason that you think that my understanding of power etc. is faulty, when in fact I can say the same for your understanding.
I guess my fault is in trying to explain in layman's terms what the relationship is among power, potential and current.
let's leave it at that.
One lat note, though. I am not the only person who pointed out that your understanding was reversed.
respectfully, Bob p.
Bob, so far, no one has explained just what it is that's "reversed" about my description(s). I am just using Ohm's Law as it exists for all circuit design. And although I'm still confused as to the point you're making, my point is simply that if you are driving an ESL, you can enjoy equal performance with either a ss or a tube amp, but you'll have a lower electric bill (use less watts) using the tube amp. Conversely, if you want to drive a speaker with a lot of electomagnetic drivers, a SS amp will use a lot less power (from the electric company) than a tube amp capable of delivering equivalent performance. Maybe I didn't make that clear at the beginning ;-)
That the discussion was about about amp efficiencies, no you hadn't made that clear.
Tube amplifiers are always less efficient in producing power, it is inherent to their nature and independent of the speaker load or type (ESL or dynamic). I.e., for the same power output, tube amps consume more power (from the electric company) than a SS, even a Class A SS.