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Carver M-1.5t Review (Vintage Amp)

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 100 49.8%
  • 2. Not terrible (postman panther)

    Votes: 82 40.8%
  • 3. Fine (happy panther)

    Votes: 12 6.0%
  • 4. Great (golfing panther)

    Votes: 7 3.5%

  • Total voters
    201

gattaca

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^^^ I owned quite a few CarverM200T cube units at one time in a larger HT setup using 1 per channel. I sent them in for recapping and general service every few years and the last time I asked Rita (no longer in business) if there was any way silence them better. As I recall, her response was these were always a bit "hissy" mainly due to the routing of internal wiring and PCB layouts - especially with higher efficiency speakers. She managed to re-route wiring and they got a bit quieter but were not silent 6" away.

I'd hope the Hypex would be dead quiet. IDK about the delivered power.
I still recommend switching off any AMP when not in use b/c these components will only last so many hours "on"...

Check out the "Buckeye" thread where you can have one made with the 12V triggers. YMMV. Peace.
 

davidc

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Wonder how much deterioration due to age affected the measurements?
A huge amount. There is a very large cult following for Carver stuff from the 80's and 90's. There are a few very well qualified restoration companies that will fix these things up for $250-$350 and make them perform better than new. It's a shame we don't know exactly how this unit has been refurbished. The owner saying "the capacitors have been upgraded" is enough to make me think this amp was NOT suitably restored.
 

davidc

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I should mention that peaking through the heatsink shows a very clean amp. So it was well taken care of.
Not necessarily. It just means it was cleaned up when the caps were replaced.
 

Aperiodic

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A huge amount. There is a very large cult following for Carver stuff from the 80's and 90's. There are a few very well qualified restoration companies that will fix these things up for $250-$350 and make them perform better than new. It's a shame we don't know exactly how this unit has been refurbished. The owner saying "the capacitors have been upgraded" is enough to make me think this amp was NOT suitably restored.
In which case, even the most diligent, careful testing really tells us nothing about what John Q. Audiophile heard in 1980-something when he hooked up his Radio Shack interconnects and 18 gauge zipcord speaker cables. Even if you recapped the whole thing "properly", isn't it possible that the lower ESR's of today's caps might cause the circuit to behave differently in some ways? In other words, "You can't go home again"?
 

Chrispy

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In which case, even the most diligent, careful testing really tells us nothing about what John Q. Audiophile heard in 1980-something when he hooked up his Radio Shack interconnects and 18 gauge zipcord speaker cables. Even if you recapped the whole thing "properly", isn't it possible that the lower ESR's of today's caps might cause the circuit to behave differently in some ways? In other words, "You can't go home again"?
What do the RS interconnects or zipcord speaker cable have to do with what he heard if they were sufficient?
 

davidc

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In which case, even the most diligent, careful testing really tells us nothing about what John Q. Audiophile heard in 1980-something when he hooked up his Radio Shack interconnects and 18 gauge zipcord speaker cables. Even if you recapped the whole thing "properly", isn't it possible that the lower ESR's of today's caps might cause the circuit to behave differently in some ways? In other words, "You can't go home again"?
Ehh... Not so much.

Well, today's lower ESR capacitors might make a difference compared with new capacitors from when the unit was new, the difference between those two would be far far less than the difference between 40-year-old leaking capacitors and what capacitors were used when the unit was new. Hope that makes sense what I'm trying to say...
And while I didn't use radio shack interconnects way back then, what's wrong with 18 gauge ZIP code if you're only talking about a 5 or 10 ft run?lo
I've offered Amir a unit for testing that has been suitably upgraded. I have quite a few different amplifiers from Carver in the '80s and '90s.
 

Aperiodic

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What do the RS interconnects or zipcord speaker cable have to do with what he heard if they were sufficient?
Nothing. That's my point. They were sufficient. You're not noted for your sense of humor, I bet.
 

Aperiodic

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And while I didn't use radio shack interconnects way back then, what's wrong with 18 gauge ZIP code if you're only talking about a 5 or 10 ft run?
NOTHING
No more jokes from me. I've learned my lesson.
 

Chrispy

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Perhaps. Sorry... Meant to be a comment on audiophile mindsets, then and now.
LOL was my mindset then as well as now :) Still have those RS interconnects (the gold plated ones...I splurged) altho I find 12g more useful in my setups these days, but still have some basic zip in use here and there.
 

SkywarriorA3

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I bought one of these amps brand new back in 1988 while in the service and still run it. Currently use it to power a set of Cerwin Vega LS-15's. Except for a 2 year period the amp has been in continuous use. It may not be the cleanest amplifier out there but at my age and years around Navy jets, I can't hear noise level differences like that anyway. Besides that, at the volume this thing generates, few chose to stay in the same room with it. And yes, I can crank it enough to get the headroom LED's to flash. Love my vintage amp...lol
 

Doodski

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I bought one of these amps brand new back in 1988 while in the service and still run it. Currently use it to power a set of Cerwin Vega LS-15's. Except for a 2 year period the amp has been in continuous use. It may not be the cleanest amplifier out there but at my age and years around Navy jets, I can't hear noise level differences like that anyway. Besides that, at the volume this thing generates, few chose to stay in the same room with it. And yes, I can crank it enough to get the headroom LED's to flash. Love my vintage amp...lol
O' Yeah! Cerwin Vega. I sold the D9 a 18", 4 driver 3 way back in the 80's..
They had plenty of slam, lotsa mids and good top end for the day. All around great rock and country speaker or anything with some enthusiastic bass slam and they where right in their element.
s-l1600.jpg
 

Fixer2004

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This is a review and detailed measurements of the Carver M-1.5t vintage stereo amplifier. It was kindly sent to me by a member.

View attachment 187157

The M-1.5t came in an era where rack mounting meant serious business. As a Carver (receiver) owner myself, I remember all the advertising for the M-1.5t. Oddly, there is no power switch anywhere:

View attachment 187158

I got a chuckle seeing that monster cable tag:

View attachment 187159

And found the power specs ridiculously complicated but I am sure was appreciated by the aficionadas of the amp:

View attachment 187160

The front LEDs don't light up until it is putting out a lot of power. I liked the top LED which was the limiting lights and nice protection circuit which kept the unit on no matter what.

This amp was part of Carver "Magnetic Field" amplification line which varied the power supply voltage to substantially reduce the size and weight of the transformer. As a result, the unit ran quite cool, maybe a bit warmer than modern class D but still, impressive for the time.

The owner has replaced the capacitors in this unit. Otherwise I think it is untouched.

Carver M-1.5t Measurements
I can see why there is no power switch as the amp did not stabilize for the 14 minutes I measured it:
View attachment 187161

The level of instability is quite large, going beyond 10 db variation in SINAD! I am used to seeing 1 or 2 dB, but nothing at this level.

When I had the unit connected, and before I fed it signal, I could see constant switching noise:
View attachment 187162

Not sure what that is about.

Here is our dashboard at 5 watts with 1 kHz tone:

View attachment 187163

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.

SNR though was better:
View attachment 187164

Frequency response was nice, flat and extended:

View attachment 187165

Crosstalk was "OK:"
View attachment 187166

Multitone shows more than usual increase in distortion vs frequency:

View attachment 187167

Front of the unit says it has low feedback which is likely responsible for this.

Claim to fame is lots of power so let's see how it does:

View attachment 187168

We see a distinct jump in distortion at around 66 watts which must be when it switches to higher power supply voltage. Allowing for copious amount of distortion, there is good bit of power at 273 watts. Here is the same at 8 ohm:

View attachment 187169

Now let's test peak performance:
View attachment 187170

There definitely is a lot of headroom, allowing power to almost double! The 600 watt number and such must have been at higher distortion levels than what I allow.

Testing for frequency sensitivity we again see the higher distortion at higher frequencies:
View attachment 187171

20 Hz performance also dropped with rising distortion at just 20 watts.

Finally, here is the ultrasonic spectrum:
View attachment 187172

Conclusions
It is nice to test products that were iconic during my youth with state of the art measurements that didn't even exist then. Using that, we see that in noise and distortion the M-1.5t is outgunned by vast number of amplifiers today. However, it produces copious amount of power which would have been even more impressive then. The efficiency rivals class D amps today which was unheard of at the time.

Looking online, I see that non-upgraded but working units go for $500 or so. They seem to be a decent alternative to pro class D amp if you have a soft spot in your heart for vintage amplifiers. :)

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I worked at a local Audio King store for over 8 years. I was constantly comparing amps, preamps and speakers, along with accessories. I've listened to integrated amps and separates from Nakamichi, Sony ES, NAD, B&O, Yamaha, Denon, and even the occasional McIntosh. While I don't doubt your measurements on the Carver amps, I question whether any serious listener or audiophile would hear the extreme noise and recorded artifacts. The only true test from my years of experience is a blind a, b, or even a 3rd piece of equipment played against each other, or at least a reference component. Point is, I've never heard a problem with with Carver amps, preamps, or most of their equipment. A Nelion Carver rebuild is awesome to my ears. An actual hearing audition wou6deem to be much more fair!
 

Doodski

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The only true test from my years of experience is a blind a, b, or even a 3rd piece of equipment played against each other, or at least a reference component.
What's wrong with a proper instrumentation grade test of gear?
Point is, I've never heard a problem with with Carver amps, preamps, or most of their equipment. A Nelion Carver rebuild is awesome to my ears. An actual hearing audition wou6deem to be much more fair!
Fair to who? If the gear measures poorly then it measured poorly. Or if it measures good then that's how it measures.
 
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