Carver M-1.5t Review (Vintage Amp)

[RichB]

With respect Amir, that's not true. Manufacturers have been quoting THD only since the mass adoption of spectrum analyzers/FFT in the 80s. The noise was quoted separately (or not at all), as an A-WTD residual noise in uV.

My old analogue THD analyzer lumps THD and N together in its distortion measurement, but it's trivial to measure and quote separately with FFT.

Manufacturers always go with the best number and that isn't THD+N, especially with large power amplifiers due the significant residual noise.

It is not clear that the Parasound A21+ are THD+N, so I suspect not.

Model Halo A 21+ « Parasound

Power Output – Stereo Mode (0.1% THD)
300 watts x 2, 8 Ω both channels driven
500 watts x 2, 4 Ω both channels driven

Power measurement are at 120 VAC:
0.1% THD, RMS continuous power,
full audio band (20 Hz - 20 kHz)Current Capacity
60 amps peak, per channel
Slew Rate > 130 volts per microsecond

Frequency Response
5 Hz - 100 kHz, +0/-3 dB
20 Hz - 20 kHz, +0/-0.25 dB

Total Harmonic Distortion (THD)
< 0.1 % at full power
< 0.03 % at typical listening levelsIM Distortion
< 0.04 %

S/N Ratio
> 115 dB, input shorted, IHF A-weighted
> 110 dB, input shorted, unweighted

It is not specified if the frequency range for the THD and THD+N is not explicitly listed.

Benchmark specs are THD+N.

Benchmark AHB2 Power Amplifier

Benchmark's new AHB2 Power Amplifier - "The Quietest, Cleanest Audio Amplifier on the Planet"

benchmarkmedia.com

< 0.0003 % THD+N at full rated power, 20 Hz to 20 kHz
100 Watts per channel into 8 Ohms, both channels driven
130 Watts per channel into 6 Ohms, both channels driven
190 Watts per channel into 4 Ohms, both channels driven
240 Watts per channel into 3 Ohms, both channels driven
200 Watts into 16 Ohms, bridged mono
380 Watts into 8 Ohms, bridged mono
480 Watts into 6 Ohms, bridged mono

The Monoprice Monolith amps are THD+N.

Monolith by Monoprice 5x200 Watts Per Channel Multi-Channel Home Theater Power Amplifier with XLR Inputs - Monoprice.com

The Monolith™ 5X is a state‑of‑the‑art, high‑performance, audiophile‑grade multichannel home theater amplifier. Rated at a full 200 watts per channel into 8 ohms an

www.monoprice.com

FTC Full Bandwidth Output Power at 8 Ohms** 200 watts
FTC Full Bandwidth Output Power at 4 Ohms** 300 watts
** FTC Full Bandwidth Power refers to maximum average power in watts from 20Hz to 20kHz with 0.03% THD and noise.

PSAudio S300 Amplifiers does not include THD+N.

S300 Amplifier

From the deepest bass to the warmest, sweetest highs, the Stellar S300 makes any loudspeaker sing and is our most affordable stereo power amplifier ever.

www.psaudio.com

THD&IM
1KHz, 1W/4Ω <0.02%
10-20KHz, 1W/4Ω <0.02%
10-50KHz, 1W/4Ω < 0.05% (90kHz BW)
1KHz, 37.5W/4Ω < 0.01%

Output Power
Both channels driven 120vac mains, 1kHz, 1% THD
8Ω 140W minimum
4Ω 300W minimum
2Ω Stable for musical transients

It's a mixed bag but no noise specifications.
Though, nobody beats PSAudio for eloquent prose:

The S300 combines the slam, linearity, and toe-tapping pacing of a Class D output stage with the warmth, grace, and rich inner detail of Stellar’s Class A Analog Cell. The results are nothing short of ground breaking. Liberate a wealth of untapped energy trapped in your media library. Plumb music’s subterranean depths and finally hear the bass your speakers were capable of. Revel in rich layers of fine, full detail. Marvel at the deep, extraordinary, wall-to-wall soundstage. Effortless. Lush. Stellar.

Vive le liberte!
If you want toe-tapping, forget SINAD and THD_N, there is only one choice

- Rich

 

[agiletiger]

Except for the underrated power, this tracks with my experience with the two Carver amps I’ve had. Both of them had a hum when nothing was playing. When you cranked the volume high, the amp sounded great. I remember when I got my first non-Carver amp and I was shocked that I didn’t hear that him anymore.

 

[restorer-john]

It's a mixed bag but no noise specifications.

Specifications these days are often incomplete or unlear. But once you get down to the low 0.00x% numbers in a high power amplifier, you can be pretty sure the noise is not included.

Typical power amplifier residuals are 15-50uV (or greater). With respect to 250mW @8R (1.41V), your 15uV becomes 99.5dB down and 50uV becomes 89dB down. So even if the amplifier has exactly zero THD, its THD+N (SINAD) can never exceed that 89dB when correctly FTC rated from 250mW to rated power. Its THD alone however can be significantly better as the noise and the PSU harmonics are excluded and/or weighted out.

The benchmark has phenomenally low residual noise.

 

[amirm]

With respect Amir, that's not true. Manufacturers have been quoting THD only since the mass adoption of spectrum analyzers/FFT in the 80s.

Unless they show actual instrumentation, I don't believe their numbers. Some subtracted noise from THD+N in hopes of showing better numbers but not using FFT based THD. To get THD numbers alone out of AP, you have to dig in. Its standard measurement is THD+N, confirming what I said about its popularity.

 

[Marmus]

Thanks for the mosfet correction, I did look in there and saw they were different PN's and the stamp on the back, upper right (outside) clearly said where they were each made. I just never noticed until he said that. Was a telecon from him which was nice. They are in boxes now like other large things so cannot look. I don't know that the updates done there did anything really.

 

[EJ3]

They worked and lasted a long time. Would love to see someone send in the competition: Adcom GFA-555, Proton D1200, and a Hafler DH-500. A 1980s high power shootout.

A properly operating resto-modded Proton D1200 (slightly higher end sister amp to NAD 2200-2600 series with the same Chief Designer input) should meet & beat the specs of my NAD 2200 reviewed by Amirm here

NAD 2200 Vintage Amplifier Review​

Conclusions
Nice to see innovation like this from equipment that is over 30 years old! Shame on manufacturers that produce amplifiers for much less power, more distortion and higher prices these days. No, you don't get a fancy case here and sheet metal is strictly budget category. But you are not going to sit on the amp. The guts are where it matters and NAD 2200 delivers.

NOTE: the output relay on stock 2200 gets corroded and fails over time. There are videos and DIY threads on how to upgrade the relay there to fix the problem. The unit tested here has that fix. Other than that, there are not reports of many other reliability issues even though NAD products are often said to be less reliable than other brands.

Overall, I am happy to recommend the NAD 2200. I almost gave it the highest honors but given the upgraded nature of the test unit, and the fact that used amps may have issues, I avoided that. But you could have easily pushed me to give it the golfing panther.

 

[beagleman]

Seems pretty good to me. I think your metrics are skewed.

I do not personally care about the Carver brand. We sold them back when I was in Sales in the 80s, but frankly remember them seeming fairly good not only standing alone, but in comparison to anything else we sold.

There was never any mention of anyone finding them subpar or any talk in audio mags of the time of mediocre sound or performance, as far as THD or noise etc.

Just a bit perplexed. Of course there is always the real life truth, that in actual usage, none of these shortcomings were audible?

 

[Walter]

I was extremely critical of this amp in an earlier reply. However, after some research, it appears that the "t" series amps were specifically designed to match the distortion characteristics of high end tube amps. (For the budget minded audiphools?) So while this amp does perform quite poorly, it is probably not fair to use it as an example of a typical Carver amp from the 80s.

 

[Sonny1]

Great review. Honestly surprised me because I expected this one to not perform as well. It was a pleasant surprise because I really wanted one of these when they first came out. Nice work Amir!

Also, what happened to the recent amp review rust disappeared? It was here one day and gone. I forgot the brand but believe it was from Underwood LSA? That one was good as well but it was strange to see it taken down. What gives?

 

[H-713]

I wouldn't read into this much, if at all.

1) As a few people mentioned, the T version is the version that was transfer function modified to sound like some other amp.

2) The amp doesn't meet its published specs. Of bigger concern is that THD+N is not stable, and does not stabilize with temperature. That strongly suggests to me that this amp is not in good working condition, regardless of whether or not it's been "serviced". These things are significantly more complicated (and more difficult to align) than a typical linear solid-state amplifier. If some self-proclaimed "recapping guru" had their hands on it, I wouldn't trust that the power supply is aligned properly.

The Carver amps were never my cup of tea, but they aren't this bad.

Also, someone mentioned Hafler. FWIW, I measured my DH120 at 0.005% THD+N (at 1 kHz) into an 8 ohm load.

 

[amirm]

Also, what happened to the recent amp review rust disappeared? It was here one day and gone. I forgot the brand but believe it was from Underwood LSA? That one was good as well but it was strange to see it taken down. What gives?

We have never deleated a review.

 

[Sonny1]

We have never deleated a review.

Thanks Amir, I didn’t mean to imply anything. It must have been an older review because I can’t find it. It was a $3k new amp from underwood that had some quality issues but you fixed some of the bad solder joints. I was trying to find the review but it seemed to have disappeared. I will check again.

Edit: I found it! Thanks

 

[Chrispy]

Thanks Amir, I didn’t mean to imply anything. It must have been an older review because I can’t find it. It was a $3k new amp from underwood that had some quality issues but you fixed some of the bad solder joints. I was trying to find the review but it seemed to have disappeared. I will check again.

Edit: I found it! Thanks

Now that you've piqued my curiosity, gotta link?

 

[Sonny1]

Now that you've piqued my curiosity, gotta link?

LSA Voyager GaN 350 Teardown (Class D Amp)

This is a follow up teardown of the review of LSA Voyager GaN 350 Class D amplifier. The motivation was to diagnose the problem with balanced input in one channel. Four screws allow the top to come off, exposing the whole unit: [click on image for larger size] Architecture is dead simple and...

www.audiosciencereview.com

 

[Prana Ferox]

I have a Proton D1200 on the shelf but it is very much not restored. I think one of the VU meter lights is out.

 

[Ralph_Cramden]

For 1976 measurements of the then new 2x100 watt Quad 405 current dumping amplifier, see: http://www.meridian-audio.info/public/quad_405_test_reports[2314].pdf The later 405-2 and even more so the 1986 2x140 watt 606-2 improve on this even more. This goes to show that already at that time sonically perfect amplifiers were possible.

Hmmm. Maybe I should dig my 405-2 out of storage and send it to @amirm for testing. Heavy little bugger, would be a small fortune to ship…

 

[CDMC]

I have a Proton D1200 on the shelf but it is very much not restored. I think one of the VU meter lights is out.

Always wanted one of those.

 

[anmpr1]

Take the assertions with a large grain of salt. Rosenberg’s connections to truth and honesty were at best tenuous.

I always viewed Harvey as a marketeer, on the borderline of lunacy. In spite of that, I think he was a true believer. In this, he was not unlike many (or most) in the tweako camp, back then. Even Mark "I never met a preamp that was too expensive" Levinson couldn't tell you why is circuit was 'better' than anything else. It was just part of the belief system of the day.

I can't say I followed all of Harvey's moves over his years, so I am asking sincerely. Was he 'dishonest'? That is, did he knowingly market fraudulent goods? The reason I ask is that there is an ethical difference between selling 'snake oil' if you actually believe the product is doing what you think and claim it is doing, even if it is not, and selling what you know to be false goods, but doing it anyway because you are engaged in scamming.

 

[SIY]

I can't say I followed all of Harvey's moves over his years, so I am asking sincerely. Was he 'dishonest'?

He started new companies to avoid creditors, warranty costs, and customer returns. Those were significant because the gear was highly unreliable.

The Futterman family maintained that he took advantage of Julius, who made nothing off the licensing "deals."

I met him once, and wanted to take a long shower afterward to wash off the creepiness.

 

[anmpr1]

1) He started new companies to avoid creditors, warranty costs, and customer returns. Those were significant because the gear was highly unreliable.

2) The Futterman family maintained that he took advantage of Julius, who made nothing off the licensing "deals."

3) I met him once, and wanted to take a long shower afterward to wash off the creepiness.

1) The first is not uncommon. Certainly not the most ethical business practice. That's bankruptcy, for you. [FWIW, last I heard, George Kaye (NYAL designer) was offering repairs for NYAL and Moscode era products.]

2) The second does not surprise me, taken at face value. But I would point out that Julius had made at least two other attempts to market his amplifier from licensing, and both failed. I do not know the details, only the outcome. One that comes to mind (i.e., from memory and without doing research) is his H3a, for a short time sold by Harvard Electronics. I guess this was 1965 or thereabouts. I'd be surprised if Julius ever made any real money from licenses, or for that matter, whether he made any 'money' off his hand made product.

Julius was an iconoclast. He spent his intellectual life 'perfecting' one circuit, which he believed to be the 'solution' to the Tube Question. Yet he came across as a decent human being. From all appearances Julius was an unassuming and gentle man, who built amps in his Manhattan apartment, one at a time, for word of mouth customers. His sort of thing could never integrate very well within a large (or even small to medium) mass market production model.

You can still find a people like that, today. Especially in tube land. Often offering products cosmetically a cut above whatever Julius made--his were pretty rough and ready looking.

3) That does not surprise me, either. In fact, I would sort of expect a kind of reaction. I think, however, it sort of goes with the tweako territory. I hate to say it, but in a way, 'true believers' are the worst of an intrinsically distasteful bunch. In this day and age, the true believer really has no excuse. At least with the scammer, one can more readily understand a primary pecuniary motivation. So they've got that going for them.