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The prototype TFM-75

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Over on CarverAudio, Eric ("MRHP") recently mentioned again that there was an unusual early version of the TFM-75 that Carver showed off before the amp was actually put in production. Following his clues and the timeline, I bought the full year of Stereo Review for 1992, hoping to find it there. Alas, my first search turned up nothing. But as is so often the case...
 
Tonight I was flipping through those back issues for nostalgia, when I found it: middle of page 70, September 1992 issue of Stereo Review:
 
20150213001837247.jpg 
 
Crappy cell phone pic, but infinitely better than nothing!
 
Note the switch and knob locations, exactly as Eric described them. They're approximately located where they are on the PT-1800/2400. Compare to the locations in the TFM-75 ad in the library, and then to the final version. Eric has TFM-75 serial number 1, the very first one released to the public. In fact it looks to me like he got his before the factory finalized their drawings!
 
If you ever come across the amp in the promo above, if you can't buy it, please at least take pics and get the serial number!
 
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The 75 is rare as hen's teeth.  I shall never be blessed to have one, if I did it would have to be pried from my dead cold hands.  I'm sure Gregg will never part with his, I bet he'd choose to be buried with it happy0009.gif

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This brings up a question from the peanut gallery related to production numbers...I've heard that TFM-75s are rare, so how many were made? I actually have the same question for the rest of the TFM lineup, including the 35X (for obvious reasons). I've read that the 35X only had a one year production run in '93, but when looking at the capacitors that came out of mine, they had manufacturing dates of 1995.

 

Is there any documentation around here that gives the production numbers and year(s) for Carver amps by model?

 

The 75 looks like a beast.

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This brings up a question from the peanut gallery related to production numbers...I've heard that TFM-75s are rare, so how many were made? I actually have the same question for the rest of the TFM lineup, including the 35X (for obvious reasons). I've read that the 35X only had a one year production run in '93, but when looking at the capacitors that came out of mine, they had manufacturing dates of 1995.

 

Is there any documentation around here that gives the production numbers and year(s) for Carver amps by model?
 
There is nothing formal that I am aware of and unfortunately Carver serialization changed from model to model.
Following is some information that may or may not be helpful:
 
I'm relatively sure that M-500(t) serial numbers include year (1st digit), month (digit 2-3), and count (digit 4-8).
I own M-500 s/n B10901278 (Sep 81), and M-500t s/n B50803966 (Aug 85) and M-500t s/n A51101162 (Nov 85).
(Some speculate that "B" units were made under license by Benytone but all of mine are marked "made in Japan".) 
20150213101525135.jpg 
 
20150213101606531.jpg 
 
20150213101847684.jpg 
 
Some pro amp serial numbers include year (digit 1-2), month (digit 3), model (digit 4-6) and count (digit 7-11):
PT2400 (pro version of the TFM-75)
20150213100827289.jpg 
 
20150213100930576.jpg 
 
PM1200 (pro version of the M-1.5t) 
20150213094219183.jpg 
 
20150213094450587.jpg 
 
But THIS PM-1200 manufactured in 1990 only has 5 digits
20150213094657836.jpg 
 
20150213094740424.jpg 
 
Serial numbers on the rest of the Carver amps I own don't seem to include any date coding at all:
M-1.0t
20150213095252682.jpg 
 
20150213091821558.jpg 
 
M-200t
20150213095544796.jpg 
 
20150213092123236.jpg 
 
MXR-130
20150213095917306.jpg 
 
20150213095956308.jpg
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Some pro amp serial numbers include year (digit 1-2), month (digit 3), model (digit 4-6) and count (digit 7-11):

 

...

 

Serial numbers on the rest of the Carver amps I own don't seem to include any date coding at all:

 

Carver went to date (and product) coded serial numbers somewhere around August-September 1990. I don't know if all lines changed simultaneously. 

 

The first year (1990) October was represented with a "0", which is easy to remember since a zero looks like a capital letter "O". The following years, October was "X", easy to remember since "X" is ten in Roman numerals, and October is the tenth month of the year (the reason for the original zero). November is "Y", December, the last month of the year, is "Z", the last letter of the alphabet. Easy to mistake a "Z" for a "2", however. 
 
Next three digits are the code for the product (model, voltage).
 
The TFM-35 was produced in 1992-93, the TFM-35x in 1993-96. Maybe the caps were changed during a service visit/repair?

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The TFM-35 was produced in 1992-93, the TFM-35x in 1993-96. Maybe the caps were changed during a service visit/repair?
 
For some reason, I was under the impression that the 35X was a one year only run in 1993 - the range extended to 1996 makes more sense though with the caps on mine being made in '95, and seeing 1/96 on one of the labels I've found.   

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20150213101525135.jpg 

I had not picked-up on the TFM-75 having one inverted channel like the early M1.0, or the M500 series.
 
That'd be death to the earlier Polk SDA speakers like mine.

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20150213101525135.jpg 

I had not picked-up on the TFM-75 having one inverted channel like the early M1.0, or the M500 series.
 
That's a pic of Dom's (modded) M-500, not a TFM-75. The TFM-75 is not an inverting amp. After all, there would be no advantage, because both channels have their own power supplies, and it would be a disadvantage because of the complication to build the amp modules for each channel differently. The only possible advantage then might be ease of series bridging.
 
Carver didn't include a bridging switch on the -75, although the PT's do have switches that allow you to do so (if you want to put 3000W into 4 ohms). You could still series bridge a -75 if you wanted to, most easily by inverting the input to one of the channels. 
 
 
 

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That's a pic of Dom's (modded) M-500, not a TFM-75.
Thank you.  In this case, I'm an idiot who can't read plain English.  The text around that photo should have been plain to me.
 

 

The TFM-75 is not an inverting amp.
That's what I thought before I went off-the-rails.  Now I'm assured that all is well in the world again.
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