eAR amps

[Brandon B]

Anyone have any info/opinions oin the eAR amps from Acoustic Reaility they are talking about at Harmonic Discord?

ICE module powered digital amplifier in a very funky spiked triangular case. Intro'ed at $3K, is now $5K and has a junior version for about half that. Curious as to any opinions on this amp (especially Jon's).

http://www.acoustic-reality.com/ear/ear_frame.htm

BB

[JonMarsh]

Hi Brandon,

The claims made are very interesting, especially the 80 dB of rejection of power supply noise (which implies a current mode output with feedback to give an output voltage control) but not easy to accept for a digital switching amp. They achieve this by using in essence a self oscillating hysteretic control methods, without a conventional high frequency carrier; this extends the control bandwidth, and removes the reuqirement for a precision carrier generator.

They may also reflect a little bit of specsmanship; for instance, re the signal to noise ratio quoted, "A weighting" limits the noise measurement bandwidth to the audible range, which of course isn't where much of the noise in a switching amplifier is generated. Also, they are quoting not based on IHF spec, but in relation to "peak" output (500W), which isn't the same as sustained RMS output. RMS output is quoted as 300W, which implies some power supply limitations.

Switching amps don't have conventional crossover notch, because they don't use an AB analog output stage- but many/most still have some issues when load current changes direction, if it uses a conventional half bridge with clamp diodes; I had to come up with a tapped inductor system to suppress this effect in the Class D amp I developed (published in the 92 AES Journal). OTOH, I have an output stage design for an AB amp using extended beta driver transistors and outputs which running open loop (no negative feedback, the only way I go these days) is in the point double zero range of distortion for crossover distortion- IM and THD. And that only becomes measureable above 15 kHz in test frequency. Should this be compared with the 2-3% distortion reported in the newest MECC ICEPower modules open loop in their most recent AES PrePrint? Gee, maybe that wouldn't be fair, since they reduce that distortion with a fair amount of negative feedback, whereas I don't use any at all...

I would be very interested to see a revew by a mag like Stereophile, which combines critical (well, sometimes) listening tests with comprehensive measurements. Mag's that are pure subjectivist are purely useless to me. If they do sound good, then this is interesting, but at the quoted prices and planned increases, not any kind of breakthrough, at least not yet. The dream of digital amps has always been to elminate parts and reduce size and cost compared with the tradidtional analog solution. But, the complexity of working digital designs tends to mitigate against that, even at high output power.

The ICEPower Home page is here,, for those inclined to follow up further. This page has links to AES Preprints covering ICEPower technology. ICEPower is a subsidiary of Bang and Olufsen.

I used to sell B&O gear in the 70's; their 4002 radial arm turntable was something of a classic, but the sound quality of their gear didn't match the esthetics; I used to do some custom modifications of B&O receivers, with outboard capacitor banks, signal path capacitor replacements, and other tweaks to improve sounds. One of my modd'd B&O recievers could actually drive a Dahlquest DQ10 fairly decently, which was not remotely the case for the "stock" item.

$3-5K isn't cheap for a stereo power amp; at that price, it's got to better an Ayre V-5, sonically. That would probably be an interesting comparison to make.

I'm not from Missouri, but I've lived there; so "show me"!

Best regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[Lex]

It's a novel look, interesting design. However, imagine wanting to put it in a rack, what a PIA making the connections would be. In short, I think don't buy this amp if you plan to have it rack mounted. Floor mounted or low stand by itself, sure.

Initial glance at stats look good, doubling of wattage at 4 ohms, sign of a good quality amp. But I will leave the tech to Jon.

My last Caveate, the Neutrik Speakon speaker connections. I don't like anything that limits functionality of existing cabling, nor anything that isn't industry standard, and IMO, these are not industry standard. Hey, I am in the cable biz, and I know very little about them. I would much rather see a 5 way binding post-

Again, after seeing Jon's post, I agree, at 5K, it's got some SERIOUS competition from long time contenders. The place for an amp like this, from a smaller concern, and a new contender at that, is undercuting the market. At 5K, it's not doing that. 5K get's a nice Proceed HPA-3 with change. leaving a spare channel for a center. As Jon said, the Ayre is a contender as well, maybe even Dreadnaught.

Lex

[Brandon B]

The Ayre V-5 seems to be the benchmark everyone over at HD would like to se it referenced too as well.

Thanks for the detailed response!

BB

[AndrewM]

I belive PS Audio has a Class-D amp, a little less power, not a fancy cabinet...but half the price.



8 ohm power
- 150 watts rms
4 ohm power
- 225 watts rms
2 ohm power
- 275 watts rms
Input connections
- 1 pair each balanced (XLR) and single-ended (RCA)
Output connections
- 1 pair 5-way binding posts
Frequency resonse
- 10 - 20 KHz (+/- 0.5 dB)
THD+N
- 0.2% at full rated power into 8 ohms (1 KHz)
Voltage gain
- 30 dB
Input impedance
- 100K
Input sensitivity (full output)
- 1.15v
Weight
- 35 lbs
Dimensions
- 17" W x 4.5" H x 14" D

http://www.psaudio.com/products/hca.asp

Review from Secrets.
http://www.hometheaterhifi.com/volum...er-6-2002.html

Andrew

[JonMarsh]

Hi Andrew,

The PS Audio HCA2 is a bit more conventional in configuration and performance. There has been a lot of talk about it at a place where discord is more common that not; some memebers are pretty enthusiastic... sight unheard.

I came across the recently published review at SOHT&HF earlier today; it includes some basic measurements, including THD at 1 kHz, and 11 & 12 kHz difference tone distortion, plus frequency response. If one were the sort to buy based on measurements, this wouldn't be your amp :P unless distortion in the two to three tenths of a per cent is your preference. It still may sound pretty fair; it's billed as being a "low feedback" design; if the open loop THD is 2-3%, and 20 dB of feedback is used broadband, then these numbers are right in line with what you'd expect.

PS Audio takes feedback after the output inductor; the eAR ICEPower circuits use two nested loops, one before the output filter, one after.

To the best of my knowledge, both the previous amps use output stages with fairly conventional half bridges.

The design I like the best that's currently in production is the Crown K series amps; Gerald Stanley developed a nice circuit with his Balanced Current amplifier; he's actually charging two symmetric inductors, with upper and lower transistors turned on at the same time driving opposite ends of inductors that are tied together for the output. Benefits include the impossiblity of every having transistor destroying shoot through current (when both transistors are on, due to switching time variation or noise), and an effective doubling of the output ripple frequency.

Additionally, it's possible to use additional switch elements in quadrature, operating at the same switching frequency, and get the noise and distortion reduction benefits that would result if operating at 2X the actual switching frequency. I don't think they're the last word sonically as full range amps, but they'd be my choice to use a "pro" amp in the home to drive a power hungry sub, such as a Stryke or Blueprint powerd monster. :B

Best regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[AndrewM]

I came across the recently published review at SOHT&HF earlier today; it includes some basic measurements, including THD at 1 kHz, and 11 & 12 kHz difference tone distortion, plus frequency response. If one were the sort to buy based on measurements, this wouldn't be your amp :P

Ain't that the truth, what really caught my eye on the SOFHT&HF review were statements like

Because I was used to hearing an edgy sound in some previous digital switching amps, I was sort of expecting the HCA-2 to be not all that much different. Maybe a little improvement. However, I was very surprised to hear it sound much like my Balanced Audio Technology VK-75SE triode power amplifier (which is several times the price I might add). One reason for this is that both amps use only two gain stages and none to very little negative feedback. However, triodes are supposed to sound a lot different than solid state. So, even with the gain stages and negative feedback similarities, they should still sound different because one is tube and the other solid state, shouldn't they? Well, I am not entirely sure why they sounded the same (and the word is "fabulous" if I haven't mentioned it already)

That's a pretty strong set of sentences there, considering the BAT is a good 4x the price (about and around), and I've found those guys usually don't beat around the bush when it comes to reviews (not one of those guys who gives every piece of equipment a good review).

I'm just not in the market for some amps right now, or I would put this on my list to look at and try and listen to, it appears that it offers good performance at a good price.

Andrew

[LarryB]

Speaking about class D's, does anyone have any experience with Spectron amps?

Larry