How Much Current Capacity do we Need from our Amplifiers?

[peng]

These are nonsensical theoretical figures that never actually reach the amplifier's speaker terminals, nor can they be measured there.
I own several NAD 2200 units, and the current reaching the speaker terminals never exceeds 16–20 amperes. The frequently cited 60A figure represents the maximum theoretical current rating of the transistors themselves, not that of the NAD 2200 as a whole.
The 240A figure likely refers to the theoretical short-circuit current of the power supply capacitors; in reality, the transistors, emitter resistors, and output coils used can probably handle only about 5% of that value.

Obviously, as I alluded to practically it is not going to happen in real world applications. Very likely that 240 A was based on the theoretical maximum instantaneous figure that the power supply was capable of, but also the output devices that must also be rated for such high instantaneous current. Same thing for NAD, HK, Parasound, and others, all ot them did great in their marketing info..., and it worked!

 

[Roland68]

Obviously, as I alluded to practically it is not going to happen in real world applications. Very likely that 240 A was based on the theoretical maximum instantaneous figure that the power supply was capable of, but also the output devices that must also be rated for such high instantaneous current. Same thing for NAD, HK, Parasound, and others, all ot them did great in their marketing info..., and it worked!

The 240A figure is based solely on the short-circuit current of the power supply capacitors; the power supply and capacitors themselves wouldn't even manage 10A.

The NAD 2200 uses two pairs of transistors per channel, each capable of handling up to 15A—that is presumably where the illusory 60A figure comes from (4 x 15A).

Nothing in this amplifier is designed for those stated maximum currents—not even the capacitors; that’s the ridiculous part.

 

[pjug]

Obviously, as I alluded to practically it is not going to happen in real world applications. Very likely that 240 A was based on the theoretical maximum instantaneous figure that the power supply was capable of, but also the output devices that must also be rated for such high instantaneous current. Same thing for NAD, HK, Parasound, and others, all ot them did great in their marketing info..., and it worked!

Here is a short summary of the issue, with some of the points already made by posters in this thread.

The High Instantaneous Current Spec

We've all seen amplifier companies tout that their amps are "high current". This article explores that topic as well as the history of how the term became popularized by some manufacturers.

www.audioholics.com

 

[EJ3]

I wish people would stop posting photos and videos of the D1200 amps. I wanted one so bad in the 80s and they still make me jealous. The D1150 tested better than the D1200, hitting 9db of headroom over its rated 50w/ch!

Funny, that is exactly what inspired me to buy one earlier this year. (I had seen the video that I posted years before and I had run into stage manager (for doing live theater) that had 3 in his system [I never got to see them in person], who had bought them new. So I started thinking that they might have the longevity abilities of my 6 NAD 2200's one of which was tested here by Amirm], my 2 NAD 2100's and my 2 APT/Holman preamps [one also tested here by Amirm]. And that I have always liked having meters.
I had been intermittently lurking on HiFi Shark (maybe 2 times a month) and have a few things on my watch list, including the PROTON D1200.
One day there was one that appeared to be in very good shape (and had the bridge mode, something that I need for my purposes) and about 150 miles from me. So I contacted the owner and told him that I could drive there, and that if he can show it to me working properly in a system, I'll buy it and bring it home, no packing and shipping needed. It turned out that he was moving and had already planned a different audio system for his new place). He said "If you do that, I'll lower the price a bit". And we agreed, I took a day and drove there (I had some other [automotive] things that I was interested in about 20 miles further than where his place was). So that is what we did.
Now I am hunting for another one so that I can run a pair of them in bridged mono 4 OHM for my custom built (by me) subs.
As to the D1150: I'll PM you the information that I have on it.

 

[EJ3]

Exactly. This is the danger with hi-fi and parties and unsupervised kids. Someone will turn it up too loud and speakers will die and I can say this from my own experience with both. It's the tweeters that will suffer from clipping distortion and this will cause their coils to melt. A high pass filter won't protect them from that.

I have fuses on my tweeters (.75 amp) and my mid-woofers (2.5 amp). Since the fuses have, at one time or another, blown (and the speakers did not), I'll say "that worked for me".

 

[peng]

The 240A figure is based solely on the short-circuit current of the power supply capacitors; the power supply and capacitors themselves wouldn't even manage 10A.

The NAD 2200 uses two pairs of transistors per channel, each capable of handling up to 15A—that is presumably where the illusory 60A figure comes from (4 x 15A).

Nothing in this amplifier is designed for those stated maximum currents—not even the capacitors; that’s the ridiculous part.

You seem so sure, maybe you have proof, such as service manual, spec sheets etc.?

Most of what I could find about those 50/100 W, 8/4 ohms, 60 to near 70 lb Denon integrated amps are in Japanese too but there is one that could be Google translated as below:

PMA-SX1 LIMITED​

The rated output is 50W×2ch (8Ω), and the maximum output is 100W×2ch (4Ω). It is fully balanced and outputs are obtained via BTL connection. The positive and negative terminals of the speakers are directly driven by the output stage of the power amplifier, delivering high driving performance. Because the speaker's drive current does not flow directly into the ground circuit, the ground potential, which serves as the reference for amplification, is stabilized, reducing noise and interference between circuits, and enabling accurate amplification.


PMA-SX1 LIMITED
The output stage uses a single push-pull FET using the "UHC-MOS" (Ultra High Current MOS) FET, which offers excellent linearity from ultra-small to high-current regions. In methods that drive many devices in parallel to carry large currents, variability in device performance becomes a problem. Therefore, amplification is performed using the smallest unit—one pair—and since the development of the POA-S1, this has become a traditional technique refined by Denon to achieve both delicacy and power at a high level.

The UHC-MOS FET installed in the PMA-SX1 LIMITED boasts a rated current of 60A and instantaneous current of 240A, enabling playback with ample margin. Furthermore, by connecting the cascord bootstrap, the UHC-MOS drain and inter-source voltage is kept constant, stabilizing the voltage-dependent amplification factor (transmission admittance characteristic) to ensure stable operation of the entire amplifier circuit.



Again, you might have proof, though I am skeptical about a company like Denon would claim a high instantaneous current spec based only(solely, your word) on the power supply's short cct. rating, that would make no sense to me.

Here's the original Denon document, but in Japanese, though one can see the part about 60 A rated, 240 A instantaneous UHC-MOS FET output transistors/output devices part:

Not that it matters, purely marketing value only, no practical importance, imo..

 

[peng]

Here is a short summary of the issue, with some of the points already made by posters in this thread.

The High Instantaneous Current Spec

We've all seen amplifier companies tout that their amps are "high current". This article explores that topic as well as the history of how the term became popularized by some manufacturers.

www.audioholics.com

I don't think people here are disagreeing on points similar to those made in that article. In fact, some, including me, are just posting on the kind of the hype they have seen, from manufacturers publications. In my case, the one by Denon was among the what I called worst (in terms of the super/ultra hype on the high current thing), but I know that's not the right word.

 

[rjp]

There is also a phase component when driving speakers where as I = V/R is only about resisitive loads.

The unifying form that works for all loads is just to let "R" be complex. Regular old Ohm's law works just fine with complex quantities.
A "complex resistance" is typically called be the more general term impedance, and abbreviated by Z. R is simply the real part of Z.
So we write I = V/Z. When Z in complex I will also be complex, which of course is what we want since it reveals the phase change induced by the load.

 

[solderdude]

V/R ≠ V/Z ... that is unless Z = purely resistive (so R) but speakers are never purely resistive so V/R does not work.
It can give an estimate so is not completely worthless.

Some planar magnetic speakers actually can come close to being purely resistive within the audible band.

 

[wwenze]

Bigger transistors = Less distortion in the final product. (Might as well also point out that higher voltage margins and extremely low impedance power supply also produce less distortion in the final product.)

It has nothing to do with the final power rating.

Is telling people the spec of the transistor a marketing trick? Maybe. Does using big transistor help improve performance? Maybe.

End of the day if the product has good price-performance, then the end performance is what matters. Output transistors are not cheap. Nor low impedance power supplies. Nor higher supply voltages.

Add: It's no different from saying an amplifier has 40,000uF capacitors in the marketing material.

 

[Ted G]

Thank you for your article. I had to upgrade amplifiers due to low impedance speakers . The vintage Pioneer 1280 with 180W couldn’t handle my
Infinity RS 2s. I was shocked. Ended up getting a Buckeye Purify Class D.

 

[wwenze]

Digging deeper into the UHC thing...

PMA-2500NE also has UHC MOS
"The steady current is 70 A and the instantaneous current is 210 A"
And look, PMA-2500NE also has service manual
Oh the transistor is a TK70J20D

I fail to see what the confusion is

 

[popej]

In "theory" they should double the watts for each halving of the Ohms: "under perfect conditions". Which almost never happens in the real world. So it is not that it normally happens in reality.

That is a view of a pessimist. I prefer optimistic approach:
Power should be halved with doubling the Ohms. But in reality we get more

 

[MAB]

Thank you for your article. I had to upgrade amplifiers due to low impedance speakers . The vintage Pioneer 1280 with 180W couldn’t handle my
Infinity RS 2s. I was shocked. Ended up getting a Buckeye Purify Class D.

The RS-II? (as opposed to the later bookshelf RS2).
If RS-II, those have extremely low impedance (close to 2 Ohms), and are notorious for being difficult to drive, even for that monster receiver.

 

[Spkrdctr]

I think this thread has drifted pretty far from the Ops intent. Not bad, it lasted about 80 posts before the drift started in earnest. We all love th ASR posting drift. Some nice things on ASR remain the same over the years. Fantastic thread.

 

[EJ3]

That is a view of a pessimist. I prefer optimistic approach:
Power should be halved with doubling the Ohms. But in reality we get more

Pessimist?
Nope, never been one in my 69 years of living.
Just giving those that don't get the results we are discussing here reasons that their results may not be correct.
Then, again, maybe it is their gear.

 

[Gremlins]

Does the advertise ultra high curent from denon PMA2500ne is a fair statement?

 

[Gremlins]

Does the advertise ultra high curent from denon PMA2500ne is a fair statement?

I need to finish reading, seems denon has been talk already

 

[popej]

Pessimist?
Nope, never been one in my 69 years of living.
Just giving those that don't get the results we are discussing here reasons that their results may not be correct.
Then, again, maybe it is their gear.

No mystery here, it is unstabilized power supply. SMPS can behave differently.

 

[peng]

Does the advertise ultra high curent from denon PMA2500ne is a fair statement?

Good question, imo not a b&w thing.