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Carver M-1.5t Review (Vintage Amp)

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 102 48.8%
  • 2. Not terrible (postman panther)

    Votes: 83 39.7%
  • 3. Fine (happy panther)

    Votes: 13 6.2%
  • 4. Great (golfing panther)

    Votes: 11 5.3%

  • Total voters
    209

iraweiss

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This old magazine was a joy to look through. Cigarette ads and then I saw this short snippet on Sheffield Lab selling t-shirts "Stop the Digital Madness". Sheffield Lab is about 1/2 hour from my home, I may have to pay them a visit and see if they have any t-shirts hanging around in an old storage bin.
You can spend hours. Forget that. Days, going through all the old stereo mags from an era where everyone measured the equipment as well as commented about usability and audio quality. I have. I also copied the reviews of everything I have owned since the 1960's plus a few I wish I owned. If I had the space I would download all the issues of Audio, High Fidelity and Stereo Review as I read every one since 1960 or so.
 

perdido34

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The Carver power supply is 'soft', means high voltage but low amps. This way you get relatively high peak power, for a short time, but much less constant power (as needed in bass).
I used an m1.0t, rated at 200 wpc, to drive a pair of Carver (original) Amazing Loudspeakers. These things had multiple large woofers, with scads of (somewhat wooly) bass. The amp could drive them at top volume all day long without breaking a sweat. I don't claim to understand electronic circuitry, but I can attest to the availability of plenty of power in the bass from the "magnetic" power supply.
 

JayGilb

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I used an m1.0t, rated at 200 wpc, to drive a pair of Carver (original) Amazing Loudspeakers. These things had multiple large woofers, with scads of (somewhat wooly) bass. The amp could drive them at top volume all day long without breaking a sweat. I don't claim to understand electronic circuitry, but I can attest to the availability of plenty of power in the bass from the "magnetic" power supply.
A lot of people use the vintage magnetic field Carver amps specifically to drive subwoofers.
 

mhardy6647

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So... while waiting for the caffeine to kick in this morning ;) I decided to search the Audio database at worldradiohistory.com to see if there were tests of either the m-1.0t or the m1.5t there. I found none, but I did find the usual ;) Carver advertisements -- including the aforementioned "water bucket" analogy. Offered strictly as-is, FYI, and FWIW; for entertainment purposes only :)

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ibid.

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You can spend hours. Forget that. Days, going through all the old stereo mags from an era where everyone measured the equipment as well as commented about usability and audio quality. I have. I also copied the reviews of everything I have owned since the 1960's plus a few I wish I owned. If I had the space I would download all the issues of Audio, High Fidelity and Stereo Review as I read every one since 1960 or so.
Storage space (online, local, flash drive, portable HDD or SSD) is cheap. Go for it, while the resource is freely available! ;)
 

beagleman

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"Third harmonic dominates distortion profile and with it, SINAD (relative sum of noise+distortion). Average SINAD of 55 dB for both channels is far, far below that median for all amplifiers I have tested to date (around 79 dB). On top of distortion, we have massive pulse train which oddly starts at 40 Hz. So definitely not very clean."


Wow that sounds fairly bad, but why are the Signal to noise ratings about 101-105 db?

Does SINAD matter more or less or does it make the "average" noise "Seem" higher?

I get WHAT SINAD is, but why do most manufacturers simply rate amps by distortion AND signal to noise ratio separately, but in ASR it is SINAD?

 
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mhardy6647

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prerich

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This is actually more disappointing to me than the Crimson 275 debacle, as this amp was definitely within Bob Carver's supposed area of expertise, and from a time when he was running the company. Does anyone know of any tests that were run at the time this was released, to see if the performance has somehow degraded over time? I'm rather glad I didn't have the money back then to buy one.
Sir, this amp is old....like I was a Seaman Apprentice in the Navy old...I've been out of the Navy for 25 years...this amp is at least 37 years old. I don't know what caps were used and who did the replacement. I've checked out worldradiohistory.com to find a possible measurements for the M 1.5t - alas I could only find responses to the "carver challenge" in Stereophile (I will check Audio and Stereo Review to see if I can find measurements). I would say that this amp is likely out of spec, and there are a dozen or so companies that do full restorations on these amps (Carver himself did quite a few). I think it's a wonder that it can still reach these levels of raw power. Would this be a possible go for a subwoofer amp for passive subs, as it seems that every high output class D amp fails to get a recommendation?
 

prerich

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RichB

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"Third harmonic dominates distortion profile and with it, SINAD (relative sum of noise+distortion). Average SINAD of 55 dB for both channels is far, far below that median for all amplifiers I have tested to date (around 79 dB). On top of distortion, we have massive pulse train which oddly starts at 40 Hz. So definitely not very clean."


Wow that sounds fairly bad, but why are the Signal to noise ratings about 101-105 db?

Does SINAD matter more or less or does it make the "average" noise "Seem" higher?

I get WHAT SINAD is, but why do most manufacturers simply rate amps by distortion AND signal to noise ratio separately, but in ASR it is SINAD?


It is true that, SINAD does not account for masking.
This is misleading because you do not need to rely on masking if the distortion is not present.
The "safety net SINAD" number might have to be higher to assure that the distortion components.
Yeah, and why is this bad?
If not SINAD, then what replaces it. Or better yet, what augments it?

The statements of SINAD at 80dB are not accurate (IMO) because, if this is the use case, then SINAD measured when driving at system at 80dB is less, would have to be higher depending on the system. Many amps distortion is made a maximum power but have far higher distortion and noise at low power.

Concerning noise, it is definitely system dependent which is of course true.
Yeah, consumers have to consider the efficiency of headphones and speakers and it is a measure of versatility. Versatility is up to the consumer to evaluate. Some want it, some need it, some don't.

Essentially, the argument is that one number is not enough and be misleading. Yes, is this an epiphany?

So, the conclusion is that manufacturers may still consider publishing THD and that's fine.
That's a weird position to take in a time where some manufacturers publish no specifications to products costing kilobucks.

It seems this video is basically saying, most of the public is too dumb to understand THD and SINAD, we can't handle this data. An opportunity was missed to include other data or criteria that should be considered as well as SINAD.

- Rich
 
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RichB

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"Third harmonic dominates distortion profile and with it, SINAD (relative sum of noise+distortion). Average SINAD of 55 dB for both channels is far, far below that median for all amplifiers I have tested to date (around 79 dB). On top of distortion, we have massive pulse train which oddly starts at 40 Hz. So definitely not very clean."


Wow that sounds fairly bad, but why are the Signal to noise ratings about 101-105 db?

Does SINAD matter more or less or does it make the "average" noise "Seem" higher?

I get WHAT SINAD is, but why do most manufacturers simply rate amps by distortion AND signal to noise ratio separately, but in ASR it is SINAD?

ASR charts SINAD for all reviews and rates them, this is true.
However, there are a battery of tests for reviewed products.

If the reader does not want to know more, that is fine but don't complain if you don't read the reviews. I don't claim to understand the implications of all measurements but there are learned folks here that answer questions.

Perhaps many complain about SINAD when they feel their ox is gored.
In the past manufacturers compete on the metrics of the time. Lately, there is the Logo war.
It is time for standardized measured performance to re-enter the competitive landscape.

- Rich
 

laudio

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That carver amp was never a good example of a well designed and measuring mid 80s amp. Pioneer Yamaha Nak NEC etc were
 

peng

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"Third harmonic dominates distortion profile and with it, SINAD (relative sum of noise+distortion). Average SINAD of 55 dB for both channels is far, far below that median for all amplifiers I have tested to date (around 79 dB). On top of distortion, we have massive pulse train which oddly starts at 40 Hz. So definitely not very clean."


Wow that sounds fairly bad, but why are the Signal to noise ratings about 101-105 db?

Does SINAD matter more or less or does it make the "average" noise "Seem" higher?

I get WHAT SINAD is, but why do most manufacturers simply rate amps by distortion AND signal to noise ratio separately, but in ASR it is SINAD?


That means distortion was relatively high but noise itself was much lower.
 

rdenney

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SINAD is just distortion and noise. It's usually easy enough to see from the SINAD vs. Power curve which is dominating. Usually, noise dominates at lower powers, because it is closer to being a constant than the power, and thus, the ratio of noise to power goes down as power goes up. This does not mean that noise goes down, it just means that noise does not rise as fast as power does. Most amps are noise-limited at low power, and the better the amp, the truer that becomes. Noise as a ratio usually presents as a line sloping downward.

Some amps have enough distortion to become dominant as the power goes up, at which point the steady downward slope dominated by noise turns up again, showing that noise is no longer dominant. We admire amps that don't have rising distortion with high power, but really I'm not sure how audible it is. Once the SPL gets high, lots of masking is occurring and our ability to discern distortion, which for most of us is not nearly what we think it is, become further limited. This amp showed high distortion at high frequencies, but I note that the AP had to be evaluating 45 KHz of bandwidth to see it--the harmonics of even 8 KHz are above what many of us can hear, particularly clearly. An 8K signal with a second harmonic that is 40 dB down will sound clean to us--I know I can't hear harmonics 40 dB down at frequencies above the bass register, let alone when those distortion products are above my range of hearing. If our hearing at 16K is already 40-dB attenuated, a further 40 dB down will be unhearable. (I'm not talking about intermodulation distortion, which can have products much lower down.) At power output levels and frequencies where most listening occurs, the SINAD is better than 60 dB. Where it really counts, this amp just isn't that bad.

With this amp, the SINAD curve was complicated by the fact that at the higher power-supply voltage as switched in based on power demand, the noise level jumped up somewhat.

But it's power specification was at 0.5% THD, which is just -46 dB. This example was doing 10 dB better than that at the onset of clipping and 20 dB better at usual usage levels, feeding 8 ohms, notwithstanding that the maximum power was a couple of dB (and only that) lower than spec. Given how little we know of the history of this amp, it still largely does what it claims to do, and I think a listener (who is just listening) would have to approach it pretty critically.

This is especially so given my own belief that clipping is the usual thing people hear, and this amp is going to be making some serious noise before it clips.

Would I choose it versus the similarly powered NC502MP Buckeye, which is roughly the same price? No. But I would choose it over a Benchmark if loud playing was a use case and cost was a factor.

Rick "pickier about SINAD upstream from speaker amps, because that noise gets amplified" Denney
 
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amirm

amirm

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I get WHAT SINAD is, but why do most manufacturers simply rate amps by distortion AND signal to noise ratio separately, but in ASR it is SINAD?
Every manufacturer specifies THD+N which is identical to SINAD but stated in percentage rather than dB. When they say THD, that is a mistake on their part. Their specification always includes noise like mine.

I use SINAD because it us much easier to remember than percentages with a bunch of zeros.
 

rdenney

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I think Restorer_John mentioned a Kenwood L02 amplifier as a comparison, and it made me curious. That amp was rated at 200W at 0.03% THD (10 dB better at half power). Yup, it was better.

It was also $3000 in 1982, four times the price of the Carver 1.5 that year. Sure, it was an integrated amp, but even if we take that part out (Kenwood's quite capable C1 preamp of the day was only $225), it was a LOT more expensive than Carver's amp.

That was Carver's innovation of the time--big amps did not need to be hopelessly expensive just to be big. Carver's reputation was based in part on the dollar-a-watt formula.

Rick "who voted for the Postman Panther" Denney
 

Kevinfc

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It’s fascinating how poorly some of these vintage audiophile amps preform. Some of my old, treasured stuff is likely no better.
 

Angsty

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Try as I might I have been unable, so far, to find a review of this amp but I did find a review of the Carver receiver and here is the link: https://worldradiohistory.com/Archi...iFI-Stereo/80s/HiFi-Stereo-Review-1984-04.pdf

It's on page 22. They were getting distortion under .005 up to 100 wpc.

Unfortunately the scanned review of this receiver from Audio Magazine had the pages cut out...
I used to cut out the pages I wanted to keep from my audio magazines and file them to save bulk. For all I know, that could have been one of my old copies! I still have that paper file somewhere and I'll see if I have that particular review.

Edited: Sadly, no, I don't have that review. Most of the stuff I have is from the early 90's, not the 80's. So, I do have multiple reviews of Carver Research "Lightstar" amps instead.
 
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restorer-john

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Every manufacturer specifies THD+N which is identical to SINAD but stated in percentage rather than dB. When they say THD, that is a mistake on their part. Their specification always includes noise like mine.

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.
 
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