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Carver M-1.5t Review (Vintage Amp)

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 98 50.8%
  • 2. Not terrible (postman panther)

    Votes: 80 41.5%
  • 3. Fine (happy panther)

    Votes: 10 5.2%
  • 4. Great (golfing panther)

    Votes: 5 2.6%

  • Total voters
    193

JohnFred

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I use two m1.0t amplifiers in mono mode and i have to say that they are on my Audiostatic es300rs speakers the cleannest ánd best souding amplifiers i have used. I came from a ARC vt200 which sounded dull and a bit lifeless in comparison.
 

Doodski

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I use two m1.0t amplifiers in mono mode and i have to say that they are on my Audiostatic es300rs speakers the cleannest ánd best souding amplifiers i have used. I came from a ARC vt200 which sounded dull and a bit lifeless in comparison.
The ARC vt200 is certainly a beautiful amp.
P1010044.JPG
 

traderitch

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That's not a stock unit. The 50/80v rail caps were of a 2 in 1 variety that soon became impossible to source and Carver supplied a separate pcb that
held the 4 replacement caps for the 50/80v rails. The unit in the image has had those caps replaced.

Edit: I checked my old capacitor box and was able to find an original 2 in 1 caps from a TFM 45 I once worked on.
View attachment 195926 View attachment 195928
I have refreshed my share of Carver products.

The "stock" photo is indeed how it arrived from the factory.
You are correct that availability of original sourced components did change builds.
It was common for different product runs to have different cap configs in them.
 

DonR

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I have refreshed my share of Carver products.

The "stock" photo is indeed how it arrived from the factory.
You are correct that availability of original sourced components did change builds.
It was common for different product runs to have different cap configs in them.
Most gear from Shenzen looks that way today. Variation in supplier given whatever was on offer in the local market that day. Only the big boys can guarantee consistency of supply because they order parts 10K at a time.
 

JayGilb

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I have refreshed my share of Carver products.

The "stock" photo is indeed how it arrived from the factory.
You are correct that availability of original sourced components did change builds.
It was common for different product runs to have different cap configs in them.
Interesting, I figured it had been modified post production due to the cap vibration pads that are still visible where they would have been placed to support the end of the 2 in 1 caps.

Carver.PNG
 

Doodski

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YMMV, but (FWIW) -- I don't like seeing/using vacuum tubes (especially tubes with substantial plate dissipation) on PC boards.
How does one know about the substantial plate dissipation. Is it because they look gray?
 

mhardy6647

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How does one know about the substantial plate dissipation. Is it because they look gray?
My point was only that I don't lke sockets on PC boards especially for power tubes.
I don't know anything about that amp, so I don't know what kind of tubes those are, but they look like power tubes -- more to the point, tubes that generate a fair amount of heat in operation.
Small signal tubes are less of a concern on PC boards, but still not my idea of a best practice.
There's also the matter of physical stress on the boards when a tube is removed/replaced from a soldered-in socket.

All in all, I like sockets firmly mounted to the chassis and (therefore) P to P wired way better in terms of robustness.
 

Doodski

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My point was only that I don't lke sockets on PC boards especially for power tubes.
I don't know anything about that amp, so I don't know what kind of tubes those are, but they look like power tubes -- more to the point, tubes that generate a fair amount of heat in operation.
Small signal tubes are less of a concern on PC boards, but still not my idea of a best practice.
There's also the matter of physical stress on the boards when a tube is removed/replaced.

All in all, I like sockets mounted to the chassis and P to P wired way better in terms of mechanical robustness.
Ahhh I see. Yes, I have serviced a bunch of the Luxman LV-105 hybrid integrated amps and the PCBs at the tubes where full of very bad solder. Lotsa heat there.
1216899-40a7f201-vintage-luxman-lv105-hybrid-tube-integrated-amplifier-and-luxman-t105-tuner.jpg
 

traderitch

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That's not a stock unit. The 50/80v rail caps were of a 2 in 1 variety that soon became impossible to source and Carver supplied a separate pcb that
held the 4 replacement caps for the 50/80v rails. The unit in the image has had those caps replaced.

Edit: I checked my old capacitor box and was able to find an original 2 in 1 caps from a TFM 45 I once worked on.
View attachment 195926 View attachment 195928
I have to apologize… I checked with a few other techs that have worked on dozens of 1.5t’s and they have run into 2 in 1’s as well.
 

tyreman

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Thank you Amirm so much!: For including vintage gear in your reviews. It allows some of us who have some of this gear (or a lot of this gear) to see if our choices were good (perhaps even good enough). It helps (at least some of us) decide: SHOULD we refurbish what we have, or step up to a different unit or even a modern unit when we are adding more modern sources to our gear. I have added Bluetooth capability (APT-X), a DAC (via my oppo 205 UDP) and the ability for my TV audio to go through my 2.2 stereo, due to finding out that my main system gear is "good nuf" (for me, anyway). Otherwise, I would have been starting from scratch again & wasting resources (in more than one way). The financial resources I have been able to put toward buying and renovating a home instead of stereo gear (making my wife happy that she has a new gas cooktop).
She is unaware that the new kitchen came from money that I had formerly allocated to stereo gear.
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. :)

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Best to have a unit brought to new specs completely before testing to get an objective picture
 
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perdido34

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Dec 13, 2021
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Actually no. But...you may seen one modified. There are a lot out there.
Actually, yes, it does. Or at least mine does. I bought it new from an authorized dealer in the mid 1980s. Nobody has modified it. It was repaired and brought back to factory specs by Carver just before the company closed, but the power switch has always been there.
 

Head_Unit

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Phase Linear 400 amp, a very well-measuring amp for the day. At the time I was very confident that I had a amp that was as good as any. It took me 20 year to understand that the PL 400 was a truly hideous sounding
Had one of those at work, didn't seem bad to me but not lovely either. On the other hand, maybe the problem was the Phase Linear CD player, which as I've posted before badly chopped up the reverb tail of Don Dorsey's "Ascent" (Telarc's Time Warp CD). My Magnavox CBD-650 played it fine.
 

Gorgonzola

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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.
The one in the comparison that I'd like to see would be the Adcom GFA 555 II, (rather than the 555). The 555 II was a Nelson Pass design and had the better rep This Ken Rockwell review showed the 555 II to be powerful and decently measuring. THD was low overall though higher order harmonics were definitely present. Resale values have held up rather well

I briefly owned one. I like the sound which was a tad on the dark side, however its transparency didn't really approach the Bel Canto eVo2i integrated, (Tripath class D), I owned in the same interval.

Interestingly Adcom is still selling an upgraded version of the 555 II, the 555se. It is pretty reasonably priced at US$1700.
 

EJ3

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For a small monthly fee, we will maintain her ignorance. You can Zelle me, [email protected]
She is only unaware (she knows the new kitchen is part of the total home remodel) due to the fact that she is over 8000 miles away in a place that is not home. She will be here soon enough (sometime in June) when I will give her $15K (I owe her about $85K anyway). When she gets here, she will note that nothing has changed in my stereo system & ask "is that where the kitchen money came from?" Just because she doesn't care about the stereo doesn't mean that she doesn't pay attention to the goings on with it (like a new piece or an old piece missing due to having been sent out for refurbishment).
 

agiletiger

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I have an M200t that my dad bought new 38 years ago. I started using it again when I got my miniDSP Flex. Getting the hiss over always heard in Carver amps when nothing is playing.

Would I get any improvements from switching to a Hypex NC252mp based amp? I’m assuming I’d get some power consumption savings especially with the new amp being able to shut itself off. How about any sound improvements? It looks like the power would be about the same.

If it matters, my speakers are Rega ELA and I have two RSL Speedwoofer MkII.
 
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