Nope. We used the term all the time in training and we didn't even carry Onkyo nearly 20 years ago!
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Onkyo TX-RZ50 Review (Home Theater AVR)
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popej
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Then is there a technical meaning to it?
There is no point asking him because I have tried, by explaining many times why the so called "high current" is a misnomer, sort of not well defined terms like the power consumption thing. It is also hard to define even if one tries, but it is possible to establish some sort of a standard, again a bit like power consumption. It is hard to define because we are talking about audio amplifiers that are usually designed to drive loud speakers that are not resistive loads and the impedance vs frequency is almost always not a straight line, not even close.. Our friend @dlaloum knows a lot about this topic but he is very fixated on the way he perceive what he seems to consider "high current design". Denon, Marantz, Onkyo, Yamaha and others clearly have different ways, and yes, in doing their won, they tend to lean on their marketing a lot, at least that's my impression, obviously. So yes, despite my disagreement with our friend, his ways, while could be misleading imo, is a lot more useful than the likes of D+M, Onkyo's marketing hype leaning ways.Why do you say the 4800 isn't a high current design? According to Amir's review, it certainly had nowhere near the clipping found in the RZ50 for 4 ohms:
Bottom line, it is a loosely defined term at best, and could be a subjective matter to some extents, in some cases.
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ban25
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Try running Audyssey XT32 with the $20 mobile app on the 4800.
If you want the RZ70, take a look at the Pioneer LX805, which is essentially identical, but on sale for $1999 at Best Buy (was $1500 last week):
Although a common marketing term (I was a sales guy), the term "high current" also helped folks differentiate good AVRs (gas in the tank) from bad AVRs (running on empty). In the early days when the FTC amplifier mandate was either too new or not heavily enforced, there just wasn't a good way to adequately convey power reserves to the customer!
Bringing it back to 2024, this would be my take:
High Current Design
Denon 4800:
8 ohm load = 134W into 2CH @ 95dB SINAD
4 ohm load = 175W into 2CH @ 87dB SINAD
Not a High Current Design
Onkyo RZ50
8 ohm load = 136W into 2CH @ 75dB SINAD
4 ohm load = ~35W (before clipping) into 2CH @ 75dB SINAD
*All numbers from Amir's testbench
Throwing around the term "high current" should imply you have informed knowledge, as we do in this case from Amir's reviews!
The following article echoes a lot of what Peng says (I think).
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
popej
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Let's be clear: Amir measured 174W into 2Ch, before protection kicked in.
Are you talking about for the 8 ohm load? If so, I ignore any power numbers where the resulting SINAD is in the 30-60dB range!
If you're talking about for 4 ohm load, I didn't see this mentioned in the first post of the RZ50 or Pioneer 505 review.
popej
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Thank you!
The RZ50 is like a Z06 Corvette that is advertised to make 670hp but under certain conditions, will limit power to the regular Vette's 490hp. Did the Z06 owner pay for the 670hp or the 490hp? It's 2024 so if I have a choice of AVRs in this tier, I'd get one w/o caveats!
Let me give you an alternate perspective....Although a common marketing term (I was a sales guy), the term "high current" also helped folks differentiate good AVRs (gas in the tank) from bad AVRs (running on empty). In the early days when the FTC amplifier mandate was either too new or not heavily enforced, there just wasn't a good way to adequately convey power reserves to the customer!
Bringing it back to 2024, this would be my take:
High Current Design
Denon 4800:
8 ohm load = 134W into 2CH @ 95dB SINAD
4 ohm load = 175W into 2CH @ 87dB SINAD
Not a High Current Design
Onkyo RZ50
8 ohm load = 136W into 2CH @ 75dB SINAD
4 ohm load = ~35W (before clipping) into 2CH @ 75dB SINAD
*All numbers from Amir's testbench
Throwing around the term "high current" should imply you have informed knowledge, as we do in this case from Amir's reviews!
The following article echoes a lot of what Peng says (I think).
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.
To maintain the same V out (volume level) as Impedance drops, the current (amps) needs to increase... halving the impedance doubles the required current.
Speaking roughly Watts = VA (volts x amps) so as impedance drops, a high current design will put out higher W's
In theory, a perfect amp would double its power output as the impedance halves... so a 100W @8ohm amp would be 200W@4ohm and 400W@2ohm
However different amp designs can also hit up against different design constraints, and may find their feedback loops getting unstable into lower impedance... thermal issues can also constrain outputs - so even if the power supply (the primary constraint) is capable of ramping up the current, other parts of a design may not be able to keep up.
An example of a high current design is the Crown XLS series... the XLS2500 is specced as follows:
XLS 2500
440W @ 8ohm
770W @ 4ohm (rises by 75% as impedance halves)
1200W @ 2ohm (rises by 56 % as impedance halves)
Compare that to the X4800
X4800
134W @ 8ohm
175W @ 4ohm (rises by 31% as impedance halves)
This is clearly NOT a high current design! It is severely constrained... and these specs do not bode well at all for 2 ohm capabilities (which are sadly, seldom specified!)
Unless the amp involved has a switching power supply (like the Crown), you can expect the size and weight of the transformer to be in direct relationship to the current capacity of the power supply.
Traditional high current amps are really heavy... the X4800 weighs in at 13.4kg... the RZ50 at 14kg, the RZ70 is 22kg (and yes this is nothing more than a rule of thumb...)
The Anthem MCA325 is 19.5kg for 3 channels - and is another good example of a high current amplifier
225W@8ohm
400W@4ohm (78% rise)
600W@2ohm (50% rise)
ban25
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They fixed those problems in the 2017 model. Source -- I have over 50 runs at Laguna Seca.
I guess the biggest difference b/w your definition of "high current" and mine is that with me, the AVR can do a "decent" job at 4 ohms whereas you need the amp to go above and beyond! There is that "doubling of power" metric on half the impedance that is definitely used as a shortcut by many but is not really necessary for the average consumer.
At least in my example b/w the RZ50 and the 3800, there is no question the RZ50 is not a "high current" design based on ANY metric as you are only paying for 8 ohm performance and not 4 ohm (which will be fine for many people)! You know this based on your Integra DRX3.4 experience.
As pointed out to you many times, it's not that simple, you need to consider other factors such as distortion levels, duration, class d vs class ab characteristics, voltage vs current, weight variations due to not just transformer in general, but the design characteristics (eg, a lighter Tx can have better VA rating than a heavier one if the design/build is not totally the same), there are more.
That said, suffice to say your example using those Crown amps is not a good/valid one for comparison with Maranz, Denon and Denon AVRs in support of your points, or criteria for what is consider "high current" design, but of course the Crown amps are much more powerful, pound for pound.
If you were to qualify your points by including the catch all phrase such as "on all else being equal basis", then I would agree a lot more.
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@dlaloum : I know you are open minded, so I have not given up trying to make the same points over and over again. Not sure if I had used the following example but here it is again regardless just to demo a case in point, using the two mid range "separate" power amplifiers that I have owned for many years.
Bryston 4B SST:
About bias: I asked Bryston the question and below is the Q&A:
Q: I am still curious about the whether my 4B SST is biased to operate in class A for the first few watts or always in class A/B regardless of the output. Can you please confirm that?
A: Yes, it does operate until it’s bias level is reached and it can be into the 20-25 watt range.
Parasound Halo A21:
Q: Same question that I asked Bryston:
A: The A 21 operates in pure Class A up to about 8w/channel. Virtually all of your listening will be in Class A.
So, based on the above facts, let's agree both could be considered "high current" (a term I use reluctantly lol..), which one would you say is "higher current" by your definition?
And which one you guess is "heavier", I trust you won't cheat by seaching for the specs for the time being.
Thanks.
Bryston 4B SST:
About bias: I asked Bryston the question and below is the Q&A:
Q: I am still curious about the whether my 4B SST is biased to operate in class A for the first few watts or always in class A/B regardless of the output. Can you please confirm that?
A: Yes, it does operate until it’s bias level is reached and it can be into the 20-25 watt range.
Parasound Halo A21:
Q: Same question that I asked Bryston:
A: The A 21 operates in pure Class A up to about 8w/channel. Virtually all of your listening will be in Class A.
So, based on the above facts, let's agree both could be considered "high current" (a term I use reluctantly lol..), which one would you say is "higher current" by your definition?
And which one you guess is "heavier", I trust you won't cheat by seaching for the specs for the time being.
Thanks.
As I pointed out, particularly with my Quad 606 experience - getting good results from a low impedance speaker design doesn't require heaps of power.... people tend to focus excessively on the power specs... back in the 70's, 25W@8ohm was considered perfectly adequate for high fidelity performance...
The 606 rates 135W@8ohm but into 1ohm it is down around 40W.... which when you consider the doubling maths, etc... is roughly equivalent to 5W @ 8ohm (at 2ohm it rates 90W@2ohm which equates - for same voltage out - to 22.5W@8ohm)
But then you look at my speaker sensitivity and MLP levels... my preferred listening level is 72db which for stereo (2 speakers) requires my 86db/wm speakers to be fed all of 0.07W.... and to cover musical peaks - providing a 20db headroom space - that becomes all of (drum roll).... 16W@8ohm
If you like things loud, and want to achieve reference levels (85 db average, 20db headroom) - then, with my speakers, a peak capability of 130W@8ohm is needed - yeah things ramp up dramatically quickly if you like things loud!! (and if you need that 130W@8ohm equivalence, for the same loudness/voltage with 2ohm that becomes 540W@2ohm.... which most amps are not capable of delivering)
And yes the Quad 606 sounds great - at the levels that I use, it is perfectly capable of driving my speakers to well beyond the loudness I require, without strain. (and I have been sticking to continuous power ratings, not peak...)
As I said, I do not recommend the RZ50 or DRX3.4 for speakers like mine that drop below 2ohm... and that is from personal experience - they don't sound great.
With a lack of 2 ohm specs / tests / ratings - I would assume that both of these designs would do well into difficult loads...
But the Bryston probably better (66% rise with halving impedance, as opposed to 60% rise)
What I would dearly love to see from amp manufacturers/designers is charts like the one Quad published for the 606
But - and here I undermine some of my own points
- the 606 rises only 30% into a 4ohm load going from 135W to 175W... it really isn't a high current design.However, it is, by design (and spec), unconditionally stable into any load... - as long as the required performance is under the continuous rating line, distortion figures are well controlled, and high fidelity results are pretty much assured.
The DRX3.4 keeps pumping out sound into my 1.6ohm speakers - no protection mode kicking in, but the symptoms of increased distortion (not clipping) are quite audible.
So rules of thumb - if you want a guarantee that the amp can handle low impedance / difficult (EPDR) loads, then look for 2 ohm specs, or in their absence look for amps that ramp up nicely into 4 ohm - if they do that, chances are they will be ok - yeah it ain't guaranteed! - And contrarian designs like the Quad can complicate things too!
The weight rule of thumb applied to both the Bryston and Parasound, would indicate that at circa 20kg and 30kg, both of these would be robust designs capable of handling difficult loads.
Tracking down specs or test result at 2ohm would provide a better indication - but those are rare.
With a lack of 2 ohm specs / tests / ratings - I would assume that both of these designs would do well into difficult loads...
But the Bryston probably better (66% rise with halving impedance, as opposed to 60% rise)
What I would dearly love to see from amp manufacturers/designers is charts like the one Quad published for the 606
View attachment 393739
But - and here I undermine some of my own points
However, it is, by design (and spec), unconditionally stable into any load... - as long as the required performance is under the continuous rating line, distortion figures are well controlled, and high fidelity results are pretty much assured.
The DRX3.4 keeps pumping out sound into my 1.6ohm speakers - no protection mode kicking in, but the symptoms of increased distortion (not clipping) are quite audible.
The weight rule of thumb applied to both the Bryston and Parasound, would indicate that at circa 20kg and 30kg, both of these would be robust designs capable of handling difficult loads.
Tracking down specs or test result at 2ohm would provide a better indication - but those are rare.
Thank you, so now you must understand why I have been countering your points about this whole "high current" hype/hearsay/vague at best term being thrown around often even when just talking about AVR amps. Also with due respect, I know you know the theories behind this, but your presentation could mislead those who don't have sufficient EE principles/theories, at least due to over simplification.
May be we can agree on some sort of a summary of this discussion by saying that we cannot assume one amp is of "higher" current design than another by simply based on the point presented in your earlier post because (reference the Quad graph), as well as some of my posts, and that there are at least the following factors to consider as well, namely:
1) continuous rating versus short term (then how long, example: transient only, 20 ms, 200 ms, 10 min, 15 min., or indefinite, ie literally/truly continuous?
2) types of power transformer used, this is a tough one because 99.9% of the time we won't know the characteristic of the transformer, even if we see the nameplate, you can have two 1000 VA 120V/80V transformer, yet one could have much better current capability and/or lower voltage drop than the other.
3) Weight, if use alone is not reliable as in 2) two transformers of the same 1000 VA and voltage rating could have very different weight depending on how they are designed and constructed, and keep in mind the size of the enclosure, materials used, also affect weight, same for the heatsinks.
4) Other cooling technique based on a combination of passive and active (such as fans) obviously would greatly affect the weight of the amp.
5) Again, as shown in your Quad amp's graph, two different amps with similar or even identical 4 ohm specs could be very different at different load phase angles because their designs may be different enough such that the output device's SOA characteristic curves could be quite different, making one performing much worse at higher phase angles while the other may not be affected much, an extreme example would be like a Purifi modules based, or even those tiny class D chip amps used by the likes of the Fosi, Ayima amps vs an Emotiva class AB amp, let alone those class AB Denon/Marantz AVR amps.
We both know full well there are many well known factors such as the level of THD used for the rated output, class AB, AAB, class D with switching PS, class D with linear PS etc., but those are obvious factors so we don't need to elaborate on.
Feel free to add as many factors, there are no shortages of them, making it, as I mentioned in the beginning difficult to say one amp, or AVR is high current because of the 4 ohm/8 ohm rated output ratio.
Back to my 4B SST vs A21 example, the two slightly different ratio is not much to go on as the 4B SST's output ratings are based 0.007% THD, whereas the A21's based on the much higher 0.2% THD. As you well know, if Bryston had used the same 0.2% THD, it's 4 ohm rating could have been much higher based on the typical class AB amp's output vs THD curve. Now feel free to Google for their weight specs, and be surprised to see that the less "powerful" Parasound amp is about 8-10 lbs heavier. Bryston used two 600 VA transformer (sort of monoblock design lol..) and the Parasound claimed a single 1200 VA transformer, so here's a case of equal VA gives a little (significant enough though) output capabilities, even when the Bryston's use of two smaller TX had obviously put them at disadvantage in terms of the way the specs are presented.
Finally, the more recent designs typically have protective schemes based on voltage and current sensing, many used ICs to help improve versatility and accuracy.
The Onkyo RZ50's issue, in my opinion, has a lot to do with their design team's choice of protective scheme/philosophy.
Based on available information, I am comfortable in saying the RZ50's voltage and current capabilities are practically the same as the Denon AVR-X3800H, X4800H and the Marantz Cinema 40 and Cinema 50. The variance in weight of those units are likely mostly size and materials used, of the enclosure and the design of the combination of passive and active cooling, not so much the power supplies themselves. The differences Amir found on the bench are most likely due to the different protective schemes used.
By the way, one of the point you made, seems to make sense but in practice it is of little use:
That's because you won't find too many amps, so let alone integrated and AVR amps, even real power amps typically do NOT provide 2 Ohm output ratings with clearly stated test conditions. They almost always provide such so called output into 2 ohms based on unspecified test duration, and THD level. So, in that case, just about any amps, yes including AVR amps, can have a 2 ohm rating if they chose to do so. And, even those that provide 2 ohm rated output that would double down from 4 ohm, you can assume it is transient, or say very short duration based, and surely we can consider that "high current" but we both know such info would be anectotal at best!
Finally, examples time, to show a couple separate/power amps that can almost double down:
Benchmark AHB2 - 100 W/190 W 8/4 ohms measured under the same conditions based on their website info.
NAD M23 - >200W/380W 8/4 ohms, spec is not 100% clear but seem to indicate it's for under the same THD level and 20-20K Hz, like Benchmark's.
You will be hard pressed to find more than a couple power amps that comes close the the above's 1.9 ratio, if you do, please provide the test conditions such as Benchmark and NAD, those are not the best to begin with, but seems close enough.
Try McIntosh, Passlab, two biggies when it comes to presumably high power/current capabile, you won't find such specs.
So, I guess one more point we could perhaps agree on, that is forget about "high current" for most (say 90%) integrated and AVR (say 99%) AVR amps if you use the criteria of close to 2:1 4 ohm/8ohm rated output measured under the same test conditions. And, there is no such thing as double down, though admittedly, the two examples used above should be considered close enough, at 1.9.
As for QUAD, yes we agree their published curve is great though I am not sure if they would provide one for all of them power amps. I can tell you though, as I might have done it before, I have never seen one single QUAD amp that passed the torture test of 1 ohm regardless of any meaningful test duration, yet at least one Denon AVR had pass such an 1 ohm test. That's ironic right? Obviously I would say that, all else being equal, just about any Quad power amp would be much preferred to any Denon AVR amps lol, just show that the issue is complicated when it comes to the narrative typically found on forums.
The post is too long, and I am too lazy to spell/grammar check, so sorry about any such errors.
Now the trouble is, we have a massive confusion of excessive facts, making it well nigh impossible for the uninformed consumer to actually evaluate whether an AVR (or amp/integrated) will work well with his speakers of choice....
What I try to do in defining those couple of "rules of thumb" is provide guidelines which would in most cases (say 80%+) be useful in determining suitability of amp to speaker matching ... which is of course almost never an issue for 8ohm speakers, but quite often an issue for 4ohm (nominal) speakers.
And yes, rules of thumb are generalisations, inherently flawed / imperfect - and yet highly useful!
P.S. the Current Dumping design from Quad is quite capable of sitting in a full blown short circuit for weeks without self destructing - there is the legendary case of a BBC recording studio that found one Quad 405 putting out insufficient power.... for some weeks... and ultimately traced it back to speaker wires short circuiting.... and yet (according to the legend) it was still putting out music, remaining stable, albeit with a very hot heatsink.
I cannot vouch for the veracity of this tale - but it has been reported by credible sources over the decades... and indicates that 1 ohm loads should not be a concern! (although output levels will definitely be current limited).
In any case, it is believable because Peter Walker is clearly a competent electrical engineer so it should be hard for him to include some sort of detection/limiting circuitry if he did choose to do so. Others might just choose to trip the circuit, I would anyway if I were the one designing an amp, there are always pros and cons either way.
I mentioned there are more than one Denon AVR that passed the somewhat 1 ohm load test and at least one Quad (yes current dumping design) that failed the same test, in fact it failed the 2 ohm test too, but performed very well in the 4 ohm test, below are the link:
I like QUAD's current dumping design/concept, would love to own one but I simply have too many amps already and with the advance of class d amp, current dumping design is not as appealing as it used to. I am not knocking QUAD amps at all, just thought in the case I cited, it seems like a good example to show doubling to 4, then 2 ohms is not a good rule of thumb at all, especially if THD levels and other factors I mentioned before are not taken into account. There are just too many inconsistencies in how amp manufacturers specifications that make it not a reliable rule of thumb, without providing more details, that as you alluded to, may result in "massive confusion".
http://www.milleraudioresearch.com/download2007/reports/yb07/quad_99_pre.html
You can see the following results (approx only):
QUAD 909, 2 channel test
157 W 8 ohms, 1% THD
258 W 4 ohms, 0.7% THD
Failed 4 ohms and 2 ohms
Denon AVR-3805, 2 channel test
164 W 8 ohms, 0.5 % THD
308 W 4 ohms, 1.1 % THD
312 W 2 ohms, 1.0 % THD
160 W 1 ohm 0.8% THD
The QUAD 909 is rated 140 W 8 ohms, the Denon is rated 120 W
Agreed 100% again, it is often difficult to strike a good balance. I usually try to get into more details and technical when I could sense a good chance someone may get mislead to believe something that could end up in making a decision that could cost them ore and may get less. The EPDR, DF (chasing super high damping factor, SINAD..), double down, ACD merits are some of those prone to result in misleading, confusion, misconceptions things as we both know, but then in trying to clarify those posts, claims, it almost invariably could/would end up with what you might call "massive confusion of facts" even if we don't think, or intend to include "excessive" facts.
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