I can't help myself; or ; Carver PM 1200 incoming, what should I do with it?

[jazzmans]

I just can't keep away from these carver amps, I've owned my M1.5t since 1993, owned two PM 350's since 2007(ish), owned a PM 1.5 since 2009(ish), TFM-15 since 2007, TFM-25 for about three years now.

All amps are in daily use except the TFM-15; it's the only one that isn't a magnetic field (with Triac) amp. Sounds great, but only(!) 100 wpc, so it's my 'backup' when another amp starts performing badly. (they're all old, and parts do wear out requiring repairs)

So, I found a cosmetically beat to hell PM 1200, the biggest baddest carver Pro series amp Carver built,(I Think) 450 wpc @8 ohms, 600 wpc @ 4ohms (where I'll use it, as most of my speakers are 4ohm), and a mind boggling 1200 wpc bridged. It's somewhat comparable to the mighty TFM-75 which I'm sure I'll never find, and only second to the Lightstar, and/or the Sunfire Signature grand.

Which amp should I replace with it?

1. PM 350 directly coupled (no speaker switcher) to Infinity Renassaince 90. (bedroom and my best speakers only used when I want the best sound for focused listening)
2. PM 1.5 directly coupled to Magnepan 2.5R (living room used every day)
3. M 1.5t directly coupled to Magnepan 1.6QR (office computer speakers used every day)
4. PM 350 through niles speaker switcher driving Infinity RS 2b, M&K S80, KEF LS-50 (living room, kitchen, used every day, usually in conjunction with PM 1.5/Magnepan)
5. TFM-25 through russound 12 way speaker switch (with autoformers) driving Infinity RS 4b, Canon Fonum 200, various outdoor speakers(4 pair atm) used every day for 'casual' listening while I putter about the house doing stuff.

Of course, this (should) go without saying, after I check it out and ensure it's performing according to spec, and clean up all the old tape/sticker goo. Pics to follow once it actually shows up.

Note, None of these amps are driven to their limits much, if ever, I've seen the PM 1.5 max out, once or twice, but I've also blown the fuses on my Maggie ribbons, so I don't think it's underpowered. I've seen the clip light illuminate on my PM 350(4.), but only once, and I was listening stupid loud. I've never maxed out my first m1.5t on my maggies, the sound gets intolerably loud before the amp runs out of steam.
I've also never maxed out the TFM-25, but I have presented it with obscene ohm loads before. (I keep the autoformers set to two speakers output, but have occasionally driven 7 pairs simultaniously. The stability the TFM-25 is famous for into low ohms is why it is where it is.) I've never maxed out the PM350 (1.) and likely never will.

all the PM series have 'clipping eliminator' on them, which lowers the input up to 8db when the amp enters clipping, therefore keeping the amps from destroying speakers. The manual on the 1200 actually says, and I quote, "it saves speakers, Use it"


On further reading of the various manuals I've found (funnily enough, I've found two different user manuals as well as the service manual) It's at heart a PM 1.5 that's been beefed up with additional transistors. Wonder if it sounds the same? All my Carver amps have a similar sound.

Anyway, anxiously awaiting the amp! It's already shipped.

 

[Old Guy8]

As new Maggie owner with 200 wpc amp, vote for #2. They seem to like more power. I don't listen loudly. So your on your own there. Hope your new amp opens up your Maggies.
Enjoy.

 

[savatage1973]

It's somewhat comparable to the mighty TFM-75 which I'm sure I'll never find,

Not even close--the PM-1200 and Carver/Clair Bros PM-2.0 are almost identical. It is a slightly souped up PM-1.5. The pro equivalent of the TFM-75 is the PT-2400. Not a "triac" amp, and true dual-mono, having two separate power cords coming out of the back. I have 2 of them in the basement that had been used to drive subs for a PA rig. Real "beasts".

 

[JayBlok]

Argggh... I just missed out on one of these for $50 bucks on my local CL by like 10 minutes ! Congratulations!

 

[jazzmans]

Not even close--the PM-1200 and Carver/Clair Bros PM-2.0 are almost identical. It is a slightly souped up PM-1.5. The pro equivalent of the TFM-75 is the PT-2400. Not a "triac" amp, and true dual-mono, having two separate power cords coming out of the back. I have 2 of them in the basement that had been used to drive subs for a PA rig. Real "beasts".

the TFM-75 didn't have a triac? how did it run, as a traditional a/b amp like the TFM-15? It must have had obscene idle power draw. One of my reasons for loving my carvers is I live in the Mojave, and it's HOT for over half the year, and any waste heat generated by audio gear must be absorbed by my A/C, thusly driving cooling bills up.

I read in the literature that the PM 1200 was a souped up PM1.5, and relabled as to the bridged power output. That means I have three different varieties of the 1.5 now, (or 4 if you include the PM 350, which is also a souped up 1.5) funny how a single design lasted such a long time.

I don't know much about the TFM 75. So, I stand corrected.

 

[savatage1973]

the TFM-75 didn't have a triac? how did it run, as a traditional a/b amp like the TFM-15?

YUP--all of the TFMs are more "traditional" A/B amps--and A/B doesn't draw much of anything at idle, but when you "step on it", all bets are off. My pure Class A Krells OTOH draw 8A current each at idle and can heat a room more effectively than my tubes.

funny how a single design lasted such a long time.

Pretty much all of the consumer M-series and pro PM-series amps are various iterations of the same design. The PM models are almost identical to their M model equivalents--none of them have any conventional heat sinks--power transistors are chassis mount. The PM series just runs a little higher top rail voltage, higher bias, and adds cooling fans to prevent meltdown.

Bob Carver was essentially "the father" of what has evolved into Class D amps--how many watts per pound can I get out of this for pro-audio use--and that is where he made his "real money". Watts per dollar (using mostly off-the-shelf components), and watts per pound (so it didn't take 3 roadies or a forklift to get an amp rack off the truck). It helps that they sounded damned good, as well.

I have owned, and still own a bunch of Carver gear--both home and pro, and if I ever need to get in touch with him, I know how to.

 

[jazzmans]

YUP--all of the TFMs are more "traditional" A/B amps--and A/B doesn't draw much of anything at idle, but when you "step on it", all bets are off. My pure Class A Krells OTOH draw 8A current each at idle and can heat a room more effectively than my tubes.



Pretty much all of the consumer M-series and pro PM-series amps are various iterations of the same design. The PM models are almost identical to their M model equivalents--none of them have any conventional heat sinks--power transistors are chassis mount. The PM series just runs a little higher top rail voltage, higher bias, and adds cooling fans to prevent meltdown.

Bob Carver was essentially "the father" of what has evolved into Class D amps--how many watts per pound can I get out of this for pro-audio use--and that is where he made his "real money". Watts per dollar (using mostly off-the-shelf components), and watts per pound (so it didn't take 3 roadies or a forklift to get an amp rack off the truck). It helps that they sounded damned good, as well.

I have owned, and still own a bunch of Carver gear--both home and pro, and if I ever need to get in touch with him, I know how to.

Wait, what?

ALL the TFM amps are not 'traditional a/b amps'
the 'magnetic field' claim is the giveaway. Until you said the 75 was a traditional a/b amp, I thought only the TFM-15CB was a traditional a/b amp, the rest are triac based magnetic field amplifiers.

And, every PM I've looked inside had a traditional heatsink mounted directly to the transistors, that's what the fans blow across.

This is one of my PM-350s, I'll shoot pictures of the PM1200 when I get it. Don't think I took any pictures of my PM1.5, but it has a similar heatsink, just mounted front to rear instead of side to side.

The M1.5t doesn't use a heatsink, it mounts to the chassis, don't think I"ve a photo of its insides either, but I've been in it before.

 

[savatage1973]

This is one of my PM-350s,

Are you sure that's not one of the PXM series amps?--that's what they look like inside.

 

[a_retent]

The M1.5t doesn't use a heatsink, it mounts to the chassis, don't think I"ve a photo of its insides either, but I've been in it before.

I concure as I've owned 3 of the m1.5/m1.5t models. Transistors are mounted on the bottom of the case, no fans, no heat to speak of.

 

[jazzmans]

Yes, I'm sure. That's one of my personal PM-350s.

interestingly enough, I have continued digging, and here
at Carver audio, they say the TFM-25 is NOT a triac amp, (I've never opened mine, so didn't know) but the TFM 45/55/75 series ARE definitely Triac amps, regardless of the promotional literature, based on the service manuals. The 75 uses two triacs, one for each channel. They also say The A series amps use a lightstar-like power supply instead of the magnetic field.



Huh, I always though the 25 was a triac amp. surprise surprise surprise!

 

[jazzmans]

Rather then edit my prior post, which could mean @savatage1973 won't see the edit, I've opted to post again, sorry for multiples.

But, Savatage, you've answered my question on what to do with the new amp. Once I've verified that its functioning according to spec, it'll replace the TFM-25, as that amp is physically in my bedroom, the warmest room of the house, and this should cut down on the waste heat in that room in summer.
Thanks!

FedEx claims it'll be here tomorrow, we'll see. (rubs hands gleefully)

 

[wallacefl]

I had a PM 1.5 running Martin Logan CLSZ 2s and and M1.5 running diy Seas W18/ Fountek monitors...PM1200 is just more of the same and the TFM -75 is too pricey IMHO for what you get over a TFM -55...go for a PT-2400 and if it is ugly but works well ...maybe Front Panel Express can come up with a new faceplate.

 

[jazzmans]

Well, look at that, no heatsink, Transistors mounted directly to the chassis.
Funny, Now next time I take my PM1.5 down I have to look inside, and I expect I'll see the same thing, with no heatsinks. Surprise! My PM 350's are both from ~93 I think, I wonder when the (needed) heatsinks made their presence known. TFM-25 has a pair of traditional heatsinks.

I do like how clean everything looks, one of the fans is too noisy, so I'm exploring options, and plan on my local shop giving it a full once over, to verify the each channel is outputing the same audio range and db. It sounded great to me driving a number of speakers today.

 

[7.62]

I was just reading the specs on the TFM 75, that thing is no joke, 1200 watts down to 2 ohms ! That matches the specs on my Crown 2502.

I haven’t read about this one your getting Jazz but I see why that would be a jewel to have now. That would easily drive anything in your stable with ease.

 

[jazzmans]

I was just reading the specs on the TFM 75, that thing is no joke, 1200 watts down to 2 ohms ! That matches the specs on my Crown 2502.

I haven’t read about this one your getting Jazz but I see why that would be a jewel to have now. That would easily drive anything in your stable with ease.

Grrr, yeah, remind me again. I can't believe one came up near me.

To whomever wins that auction, congrats and i hate you. Ah well.

This is good specs, but not nearly that good specs. It's a beefed up PM 1.5.

450 wpc in eight ohms

600 wpc in four ohms

not rated for two ohms, and all documentation I've found specifies 4 or 8 ohm speakers.

 

[jazzmans]

Not even close--the PM-1200 and Carver/Clair Bros PM-2.0 are almost identical. It is a slightly souped up PM-1.5. The pro equivalent of the TFM-75 is the PT-2400. Not a "triac" amp, and true dual-mono, having two separate power cords coming out of the back. I have 2 of them in the basement that had been used to drive subs for a PA rig. Real "beasts".

Yep, you were right about almost everything in this thread.

if you zoom in, (I know, I should zoom and crop, whatevah) it's a PM 1.5A board.
No heatsinks, transistors mounted directly (sort of, there's a skeleton layer allowing airflow under and above the transistors, but it isn't by any stretch a traditional heatsink) to the chassis. The face glue-goo was just a square of adhesive left over from gaff tape I think, cleaned it off with rubbing alchohol and a bit of elbow grease.

After my shop has verified it's functioning properly, it'll go ...not sure yet. I test ran it where my tfm-25 is, driving from 2-6 pair of speakers, and was surprised how easily I got those leds, (which rarely move on my other pm 1.5, and my m1.5t.) moving at relatively low volumes. Don't get me wrong, it was loud, and I was driving five pairs simultaniously, but not 'that' loud, and the tfm-25's voltmeters showed less then 100w on the peaks.(I know they aren't at all accurate, and power rises logarithmically)

the cool thing is each led is coupled to a pair of transistors so if an led lights up, then that bank of transistors is seeing signal, it's laid out in the manual precisely which pair of transistors drives, or is linked to which leds, both left and right. I still think the concept of a transformer that only powers the next bank of transistors when additional power is required is really cool, and smart.

Other then the triac, which looks like one side has gotten a LOT hotter then the other, the internals look really clean. I didn't see any hot spots, or scorch marks, or anything negative on any of the boards, so here's hoping.

 

[jazzmans]

OK, so I think I figured it out. Adding a speaker switcher inline, adds another layer, or filter, or whate'er you wish to call it, between source and acoustic driver(speaker).

This has become obvious in my long and twisty journey through the audio landscape. when I have had the opportunity to A/B a signal through various amps, with and/or without a speaker switcher, the speakers being driven directly have always been a bit more .... 'Alive' then those that are routed through a speaker switcher, no matter how high end of a switcher it's been.

So what I think I'll do is, re-route everything so my Magnepan 2.5R will be driven by my PM1.5(as it is now) or (as I'm leaning) my PM1200, and I'll send another balanced signal to the other amp (PM1.5 or PM1200, depending) to directly drive my Infinity RS 2b, (and then) send another balanced signal (You see why I prefer a balanced signal path,right?) to my PM350,(as it is now) which is then routed through my Niles 4 way with potentiometers switcher, to whatever speakers I'm currently playing with. Currently KEF LS-50, M&K S85.

yeah, that will give my Infinity rs 2b a direct connection to their own Carver amp, allowing them to become one, like my Maggie 2.5R are.

yeah. Cool! This will allow me to run whichever amp (PM 350 i think) that's driving my switcher linked speakers at a lower level then those driving my Maggies, and Infinity speakers.

 

[jazzmans]

Hi all! I got the PM 1200 back from my shop (Audio Xpert rules!), they found a small solder failure on the right side where the coil is. Took Bobby a while to find it, he had it on his bench running for a couple of days before he could isolate it. Now it's all back up to the original spec for output, distortion, etc etc.

I've placed it in my system pretty much as I said I would, it's driving my Maggies 2.5R now, and they really shine with the extra oomph. the output led's sure do move a LOT though, which is unexpected, with my other carvers the led's rarely budge from the bottom leds, but then again, the Magnepan 2.5R are power hungry monsters. Those ribbons sound simply fantastic now.

It allowed me to also directly couple my Infinity RS 2b to the PM 1.5, so no speaker switcher degrading the sound.
having dual balanced inputs to the carver amps really makes them usefull, now I've got three of them in my main system, all chained together (PM 1200, PM 1.5, PM 350)

I Love these damn carver pro amps. Now the only problem limiting me is house power. I really need to run two new lines from my power box to the living room, each one of the three amps are capable of using the entire 20 amp circuit by themselves.

 

[roger2]

@jazzmans I can't see your PM-1200 pics. The PM-350 pics are there, but only placeholders for the 1200.

Would love to see the insides of the PM-1200 as I bought one new sometime in the 90's to run four EV pa monitors. It was a great amp. But I never looked inside it back then.

 

[jazzmans]

https://photos.app.goo.gl/4KwJZfWUPoAhuE8j8

That's a direct link to the pictures, it should work now. Can you see the earlier photos posted?

Google photos is a PITA to share photos with.