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Modjeski's design.I have a chance to buy a pair. (They can now be modified by Elliot to accept unmatched tubes.) I'm looking for comments of owners or previous owners. What do you think? For some reason I've always thought these were amps that if they came along and you had the money to buy them and you were an audiophile you had no choice. Am I wrong?
Thanks in advance.
Follow Ups:
Hi,I would personally avoid them because I know that the 6LF6 is rare not only matched but rare period. Even with the mod. More importantly the DC servo is known to go wild with potentially catastrophic failure down the line.
I know Joe Rosen has a set that he was trying to sell a few months ago... and he probably knows as much about these amps as anyone.You should look up his posts in Tubes or Vintage on the couterpoint. I have a original Futterman myself..but it has an Output capacitor, which I trust, rather than a unstable servo circuit.Just my opinion. Now if you could get them for cheap it would be worth a go!YMMV and all that.
Thanks AJ, I'll track Joe down. What do you consider "cheap" for these? I'm having a hard time figuring out their value.
Seems like AJ knows a whole lot more about the circuit than I ever bothered to learn, insofar as I never owned a pair. 6LF6s or no 6LF6s, you might want to consider his information seriously before making a purchase.
I am not sure what the value would be.. Keep in mind condition especially around the circuit board traces as this thing runs HOT!They are beautiful to behold and I might buy a pair if they were inexpensive enough...but I think you truly would be better off today with one of Atmasphere's designs for the money and grief.
The issue with these is condition and the effectiveness of the servo and the sound it imparts... from one of Rosen's flamboyant posts:
"The Counterpoint is another "by the numbers" piece of design work. The gimmick here was to make the amp all direct-coupled, regardless of the consequences. And being a Counterpoint, it had to be totally compromised in the false hope of being reliable & convenient. The design sucks, and of course is neither. Sound is incredibly grainy & hard, very solid-scrape. This thing uses an op-amp servo to eliminate DC, a protection circuit to mute the output if things don't come out the way they should, and scads of solid-state regulators & zeners to give the desired direct-coupling. Zeners replace coupling caps in some spots to accomplish the design goals.
Cute,hunh? I was told this was the work of Roger Modjeski of RAM Labs. Poor guy. Very clever. Too clever to be smart, though, whoever really did design it. Each amp uses 11 valves. One of them is a triode. One.
See what a nice guy I am? You asked my for my opinion of 2 amps and I even threw in an extra one, hopefully for good measure. Cheers! "
6LF6-Caveat emptor.
I don't think there is anything inherently wrong or unstable about the 6LF6. Julius Futterman knew what he was doing when he selected them for his last crop of amplifiers. But as Alta Vista notes, the 6LF6 used to be plentiful and cheap. When I owned Futterman amplifiers, I could buy 6LF6s at local radio supply stores for a few dollars a piece. As for stability, one pair of Futts that I owned lived for 10 years on one set of 6LF6 output tubes. At this time, one has to go to the esoteric tube dealers to acquire 6LF6 replacements at a relatively high cost. In the modern era, most makers of Futterman-type amplifiers, e.g., Transcendent, have gone over to the PL-509, also variously known as EL509, 519, etc. These are still available at reasonable prices. I wonder why Alta Vista has not worked up a conversion option, so that one could use the latter tube type in the SA4. This would be as much of a boon to its continuing existence as is the added balancing circuitry.
I did not say anything was wrong w/the 6LF6,even though in the Counterpoint,it's a horrible tube,prone to violent self-destruction(plus the added damage inflicted on nearby components)@the end of it's 800 hr life.Please read my 2nd post;it's about availability.ymmv,fwiw,blablabla.
Lone Gunmen, can you explain? I don't know their reputation (the 6LF6, that is.) Are you talking prices or difficulty in finding matched tubes (which isn't a problem in the SA-4 anymore if you have Elliot do the mod.)
Specifically,it's an obsolete tube-type,w/a limited life-expectancy,and THE KEY COMPONENT in this amp.If you're set on getting the amplifers,buy as many of these tubes now as you can.-
The SA4 is indeed an object of lust for an OTL-phile, like myself. I had to stop myself from buying a pair only a few years ago. Here is the poop: The SA4 is basically a Futterman-type amplifier that eschews the use of output coupling capacitors, so it is direct-coupled. Thus the speakers are not shielded from DC imbalance in the output stage. This can on occasion cause problems with speakers AND with the amplifier itself. (Since I never actually owned a pair, I don't know exactly what goes wrong, but I do know that the SA4 was rather notorious for spectacular meltdowns.) The input stage, I think, uses a 12AX7, instead of the tube(s) favored by Futterman for developing the necessary drive. On the plus side, if the amplifier you are buying has recently been upgraded by Alta Vista, at least you can be sure that it is in good working order at the present time, and if you have the optional bias controls as shown in the photo, that might ameliorate the instability problem IF you are diligent about re-balancing the amplifier from time to time. Without those external bias pots, I would be more hesitant to take the plunge.
Thanks Lew, that's all good info. Do you have thoughts on what to look for in a speaker to match with the SA-4?"I had to stop myself from buying a pair only a few years ago." that cracked me up. Only an audiophile would understand this comment.
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