[RussKon]

on topic.... bench test...

ok.... the specs are not spectacular on the bench test.....

but i thought this was an "audio forum".....

sorry if my question about "how the amps sounds" upset you...and your concern to stay on-topic.....

[Brian Cheney]

AC is a small community who can afford to be honest with each other.  I know Stan Warren, who is a peach of a fellow and very knowledgable.  So am I.  If Stan's measurements corroborate mine but he still thinks the amp sounds great, I believe it.  Still, I have to find out for myself.  When I do I will report the pluses and minuses so our entire community has the straight dope.

I have no connection to Carver Pro.  It would be great to be able to recommend something you can buy on Yahoo Shopping at 30% off an already modest list, that approaches the state of the art, even if mods are required to get to that level.  Stan, Ric Schultz, Wayne Wanaanen and the Eighth Nerve people are in the mod business and will have a field day.  Based on what I've seen I would do at least the following improvements:
1. Replace electrolytic signal coupling caps with shorts or high quality films.
2. Replace the 12" computer cable carrying the input signal with a short teflon insulated silver twisted pair from good RCA jacks which I would also install.
3. Beef up the power supply from its current 60,000uF.
4. Install heatsinks with convection cooling.  The fan noise is an obscene joke.
5. Replace the insulated plastic binding posts with good solid brass or copper.
6. Devise a digital output filter to remove the 600 kHz switching component that infests the entire amp.
7. Find out why the amp clips nearly 2 dB below spec into 8 Ohms, and why it oscillates at that point.

Once the modders have done their magic they can send the improved ZR1600 to me for comparison with the well-burned-in stock unit I'll keep for now.  Make it a contest with a nice prize for the most sonically attractive mod.

"Reviews" consisting of mindless raves or pans don't help anyone.  I suspect that guy from the Prosound Review Carver quotes did nothing beyond hooking up the amp to whatever gear was handy and copying the Carver press release.  Otherwise he would have mentioned the serious issues the stock amp presents!

[Sa-dono]

Thanks for providing us with the specs on the Carver Brian! Definitely keep us updated if you find out any new info.

Other topic posts have been separated to a new thread for your info Brian.

[_scotty_]

Deleted

[MttBsh]

For four months now I've been listening to my favorite music on the Carver Pro ZR1000. It has delivered nearly magical resolution, dynamics and soundstage... the best amp I've ever heard.  Now, having read the poor benchmark test results, I have to ask myself if my enjoyment has all been in vain.

[blue]

Hehe MttBsh, but of course your enjoyment was in vain.  Life is all in vain.  Bah!   But really, I have been greatly enjoying the comments over the last few days.  

To me, it is absolutely wonderful to find an amp that sounds great to some people but may have strangely poor metrics (granted, there were some theories about the test setup parameters around the metrics).  

I see this as an opportunity.   Finding meaningful metrics in any field can be a challenge.  More so in high end audio.  You can measure 10,000 things, but the challenge is finding metrics that matter and what their thresholds are (does it matter if an amp is purple or pink in color, or if it faces north or east, or if it has 1000W of power, or if you said nice things to it, or if...).   So here we have an amp that apparently sounds nice, but does not seem to have at all decent metrics.   If this is the case (that it sounds good & has poor metrics), then it is a wonderful opportunity for refining the weighting of the metrics currently in use today.  

Or... maybe not.  This is the fun stuff, the sense of discovery.

I look forward to the listening tests.

[Rob Babcock]

Hey, there's still that breathtaking rise time!   I'm guessing that your comments are tongue-in-cheek, MttBsh?

I agree that given the guts of the amp it would be a playground for modding.  Certainly nicer binding posts would be nice, and convection cooling would beat a fan any day (I despise noise).

[DVV]

Testing this amplifier has been a highly informative and sobering experience for me.  John Curl, on whose equipment the measurements were made, has tested many switching amps (he had several on hand, including a Tripath output stage) and was not as surprised by the results as I was.

If I had seen the ZR1600 on my lab test bench in 1965 (when I got started) I would have been alarmed.  I would have checked for proper biasing of the output stage and the feedback loop for enough compensation.  The distortion ...

Brian, without questioning your results, may I suggest you repeat them but using a line filter this time?

My experience with digital (switching) amps is admittedly rather limited, and boils down to two commercially available models, by TaCT of Denmark and Sharp of Japan, plus a module made by an uknown designer. They ALL measured and sounded differently, and for the better, after I fed them power through my DeZorel line filters.

If possible, do it using this particular make of line filters, because it has a fairly normaly slope increasing as frequency rises, and by 40 kHz it is no less  than -60 dB down. One sample is circulating here, ask Audiojerry, he keeps tabs on it. Another is with James Bongiorno, so if you can reach him, he might be willing to loan it to you.

The reason why I specify this particular make is because I'd love to have my conclusions verified and agreed or disagreed on. On my HP distortion analyzer, with the filter there was less distrotion, less noise and improved sonics all around, from bottom to top - in fact, far more so than your typical analog amp. I assume this is at least partly because the switching noise is superimposed on line noise, causing additional internal intermodulation. Also, the power output improved somewhat, though I wouldn't call that significant.

Cheers,
DVV

[Jumpin]

Brian,

Thanks for the test results.  My hats off to you for taking your valuable time (and money invested in the Carver) to provide objective information on a very hot topic.  

Regardless of the bickering some want to partake regarding methodology, etc.. I don't see them stepping up with anything but speculation and conjecture.

Regards,
Jumpin

[rosconey]

now we know where the tube like sound comes from =distortion lol

[Jay S]

Dejan/DVV has a point.  My Acoustic Reality eAR Two digital (ICEpower) amplifier sounds much better when plugged into my power filter (a Blue Circle Music Ring balanced power supply).  Soundstage becomes much more expansive and the sound gets more refined overall.  Supposedly the eAR Two already has a built-in power filter...

[Brian Cheney]

I listened to the EAR 2 on the RM 40 at Soundguy's house for about 8 hours recently, and it impressed me with a clean, clear presentation.  My only criticism is that it sounded somewhat hard.  Breakin and warmup may ameliorate that impression.

In my home system I have heard the Spectron Musician II and found it quite good, not as natural as my analog amps but very respectable.

Listening to the ZR1600 will be through my Audio Magic Matrix Stealth and large Bybee AC line filters, just like my reference amps.  I am a big believer in AC line filtering, having monitored the AC line waveform 24/7 during my lab work days.  The line is full of garbage and the waveform has chunks missing from it.

Tube sound equates on the test bench to large amounts of even order harmonic distortion, which the ZR1600 also exhibits.  Unfortunately there are equally large amounts of odd-order harmonic distortion, and the distortion series from 1 kHz extends out to at least fourteen harmonics.
And then there's that rising noise floor, up 20 dB at 50kHz relative to 20 kHz.

The 600 kHz switching frequency is of course inaudible, but supersonic noise and garbage have a tendency to fold down into the audio range.  It is generally a good idea to suppress any RF noise in an amplifier's output.

[doug s.]

Specs do matter to some degree to ME. I couldn't live with this amp and be happy even if it sounded like a 20,000 dollar tube amp.  

=========

it's rare that i read a someting on an audio forum thread that's so funny, i actually laff out loud in real time!  congrats, warner!     what a comparo - ya couldn't be happy w/the $20k toober either, if *specs* were such a concern!

doug s.

[warnerwh]

Let's say Audio Research or Krell advertised their amp as making 300wpc. In the manual it states do not run this amp hard or it will go into oscillation. The amp doesn't make over 200 and is advertised at 300. This is fraudulant,at least in my opinion, and I would not support a company like this.

[Ears]

Didn't the Stereophool class A rated ps audio amp also measure badly?

[Jack]

OOOOPPS! Please elaborate regarding "conventional equipment". "Conventional" testing methods on this TriPath-based product is a mistake and you should know that. Carver Pro will have an official response shortly.

Testing this amplifier has been a highly informative and sobering experience for me.  John Curl, on whose equipment the measurements were made, has tested many switching amps (he had several on hand, including a Tripath output stage) and was not as surprised by the results as I was.

If I had seen the ZR1600 on my lab test bench in 1965 (when I got started) I would have been alarmed.  I would have checked for proper biasing of the output stage and the feedback loop for enough compensation.  The distortion

[Brian Cheney]

Our conventional equipment:
Audio Precision distortional analyzer with 80 kHz filter engaged
Hewlet Packard 3563 spectrum analyzer
HP two-channel scope, 350 mHz
Fan cooled 300W 4 and 8 Ohm resistive loads

Your tone implies you know something we don't, so please elaborate.
A sharp filter centered at 20 kHz at the output of the ZR 1600 should improve all measurements, but it is perfectly legitimate to make measurements without such a filter since users would not have such or want it due to the severe bandwidth limitation it would impose.
I emailed Carver Pro for a measurement protocol and filter specs and await a reply.

Right now the 600 kHz switching frequency IS the output of the amp, the signal is almost completely buried in it.  At low levels, where the signal decreases but the noise stays the same, distortion measurements go up sharply.

[Jack]

It is encouraging and intriguing to see many people in the audiophile circles using ZR amplifiers and having good results. Obviously Mr. Cheney has access to some test equipment and has seen fit to publish his findings here. As pointed out, amplifier testing is somewhat standardized and we believe that we have performed all necessary and applicable tests to the ZR line of amps.  We do disagree on some of Mr. Cheney's findings however - Power Output at 4 ohms and 8 ohms for example. The figures stated are extremely low. We would be happy to post THD+N vs. Frequency curves as measured on the Audio Precision systems that we have here. (Let us know if that's what you'd like) Dynamic headroom - in order to comment we would need to know how the test was performed. The stated 1kHz rise time of 1ns makes no sense to us so please clarify.
Correctly stated is the fact that switching amplifiers (some confuse this with switching power supplies) in simplest form have essentially two devices connected in a similar manner to a regular push-pull output stage. While there is indeed a finite time where both output devices are in the "off" state this event happens at the switching frequency of the output stage - 500kHz+. This is in no way the same as crossover distortion in a linear amplifier! Also correctly stated there are some visible switching artifacts at the amplifier output.  These artifacts, as mentioned previously, are at frequencies above 500kHz thus completely insignificant. The amplifier does in fact have significaqnt output filtering and you would most definitely notice if they weren't present. The comment regarding a sharp 20kHz filter "done in the digital domain" does not make sense here and the Scotty comment regarding AES 17 filters is also misunderstood.
Measurements of any type of switching amplifier can be difficult if you are not armed with the correct equipment. There is a very good tech note on the Audio Precision website about this topic specifically. To make a long story short, the switching artifacts from any type of amplifier of this form can cause the input sections of test equipment to be overloaded. This can result in erroneous measurements compared to those taken from a standard linear amplifier on the same test setup. Scotty points out the use of the AES 17 filter. This is indeed present in all of our AP systems. Furthermore, you will also see that AP offers a stand-alone filter AUX-0025 to be used specifically when testing switching amplifiers. In fact, AP used on of the ZR amps during its development of this very filter. When components such as these are used to test the amplifier then you would see numbers reminiscent of our own.
The ZR 1600 is capable of delivering approximately 600W RMS into 4 ohms per channel bridged. If the AC supply out of the wall is sufficinetly stiff these numbers will be obtained at the claimed specification. Mr. Cheney appeared to observe "oscillation" at the onset of clipping. While the numbers appear to be low for some reason, the apparent "oscillation" can be easily explained. It is not in fact anything like the oscillation that you may experience in linear amplifiers. Poorly designed and/or improperly compensated linear amplifiers may oscillate when connected to a load and at times can be a problem toward the clipping point. By the same token they can oscillate at any output level, in either a single half or both halves of the output waveform. In the Tripath chip, there are reset counters that come into play right at the clipping point. This is normal operation and not a result of design or compensation issues. These reset events play no part in the technical or sonic performance of the amplifier.
We hope this clarifies some of the issues and we would be more than happy to post PDF's of any particular measurement that we have on file.
Bottom line:  Under the right testing procedures the Tripath-based ZR amplifiers test favorably.  No competitive marketing mumbo jumbo or flawed test execution should deter interested parties in pursuing this amazing amplifier.  Hearing is believing.
Sincerely,
Your friends in Carver Pro Engineering

[warnerwh]

Jack: Thank you for the post. I for one would like to see a pdf of your measurements. Power, S/N, dynamic headroom, damping factor and input impedance measurements would be nice.  It's interesting that John Curl wouldn't understand the proper way to take measurements but nobody knows everything and anybody can make mistakes.  It did seem odd after thinking about it that any company these days would advertise specifications so much different than what they actually were.  I must admit I was stunned by the findings.  I think you'll find alot of good attention will come your way due to the misunderstandings. Sort of like free advertising.  Thank you for your time.

[8thnerve]

Jack, thanks for the informative reply.  My ears confirm your explanation, those test numbers looked very different than I expected.