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In Reply to: RE: Futterman H3 amp 'upgrades' posted by rogerh113 on July 31, 2019 at 10:31:43
Thanks for all of the information and feedback. Looks like an interesting project, so I have placed a couple of 'want' ads - maybe I will get lucky!!
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And then, if you really like it and want the provenance, pick one up when it comes on market, which won't be often.
I have thought of that. Problem is that I have not found an H3 schematic where ALL of the component values are clearly specified. I also gather Futterman tuned many of these to work properly, and I would rather have something that had clearly worked, and replicate that.
I also think it would be best to have the original case and possibly transformer. At the end of the day, that is about what you are left with if you do a major rebuild. Maybe add in the tube sockets...
Likely if I cannot someone selling an original one, I will just abandon the concept. Just see how things play out....
I also gather Futterman tuned many of these to work properly
I've heard that more than once- which is why a good number of later iterations of his circuit made by others didn't work as well.
Our amps are a bit easier to clone- no tuning involved. There is a DIY thread on DIYAudio.com about building OTLs. You might take a look if this is an option.
Otherwise, if that Futterman is cheaply available, get it serviced out. We've done that sort of work plenty of times.
Another option is Transcendent Audio- they make kits (as do we) which are a modification of the Futterman circuit.
It sounds like you have upgraded a Futterman H3 'plenty of times'. I would be most curious to hear your impression of a fully upgraded Futterman H3, the good and the bad. That would provide a lot of perspective for me.
thanks -- Roger
I've not played them a whole lot simply because they had to go back to their owners. But compared to our gear they are brighter while at the same time not sounding as fast (if that makes any sense; keep in mind our amps have bandwidth to 200HKz). I also found them less robust in the bass, but well extended.
Much depends on the speaker load; the Futterman uses a lot of feedback and our amps don't. But your particular driver choice will work fine with either amp.
Thanks very much for the perspective - it really does help a lot. I understand what you are saying about the comparison. Sounds like some slightly different flavors of a good thing!!
-and that, as you say is a 'good thing' :)
I think that I actually read a good part of it, and there was a lot of information provided - not sure there was ever a final schematic.A scratch build certainly would be an option. I have built a SET amp from scratch, but I did find that milling of the top plate and the construction of the case was extremely time consuming (perfectionist), and a big aside from putting the actual amp together. The upside is that you can get the transformers and other structural parts you really want and custom fit the case.
My going in preference is for the Futterman, just because of the history and I would like to hear one. It would require careful replication, as there must be things there that contribute to making it work (like the tall rising wires out of the tube sockets). It would be fun and highly educational. Hopefully it would also work at the end of the day....
regards -- Roger
Edits: 08/08/19
not sure there was ever a final schematic.
Its on page 3.
The Circlotron OTL has a history too. Although we were the first successful company selling one, a Circlotron OTL was patented around 1955. It integrated the driver tubes into the Circlotron which IMO was tricky to set up.
Historically the Futterman sort of dead-ended with Julias. There were other amps based on the circuit- NYAL, Fourier and (to a lessor extent) Counterpoint, to name a few which really cemented the idea in audiophile's minds that 'if its an OTL, its going to blow up'. Futterman didn't help that much- according to Harry Pearson of The Absolute Sound, Julias showed up at his house with a pair of monoblocks, one of which promptly failed, taking a loudspeaker with it. After his death, the only serious evolution of the Futterman idea was Transcendent Audio; the latter seem to hold together rather well.
Atma-Sphere is the oldest OTL company in the world (43 years we've been around much longer than Futterman was) and the simple reason that is so is because we were the first to figure out how to make OTLs reliable. That's important, especially if a vintage and possibly rare loudspeaker driver is involved- our amps aren't known for eating speakers (if they were, we'd have been gone long ago).
Ralph, You forgot "KSS" and Non Pareil, two of the most unreliable and short-lived amplifiers ever. Those two products alone were enough to smear the reputation of all OTLs. The Counterpoint and the KSS were direct-coupled and relied upon a servo mechanism to zero out the DC. (Not sure about the Non Pareil.) As if.I briefly owned a Non Pareil, having been influenced by glowing reviews. It was the cheapest made piece of c**p I ever saw and sounded awful.
PS. I could be wrong, but I think it's "Julius", not Julias.
Edits: 08/14/19
Just to clarify, I am interested in the Futterman on a purely arbitrary basis. I have heard nothing negative about the other options you mention, and I am sure they have their merits (and perhaps stronger ones).
I have never heard an OTL before, so rebuilding the Futterman will be fun and allow me (hopefully) to hear something that I really would like to experience. I am expecting that it will not be able to beat out my SET amp, but who knows.
Perhaps I will not be able to locate a reasonably priced Futterman H3, and may have to forget it or select a different option. I am just starting my search, and research, so it is too early to know.
Nt
Interesting option - did not know something like this existed. Thanks
These amps are rare and precious. I think you will probably have to prepare to pay a considerable amount for them.
We shall see. In their current state they are unusable, but could be considered art. To genuinely bring these amps back to life, pretty much everything will have to be replaced. Since most amps were unique, the circuit will have to be traced to replicate it. Considering all of that, and the sourcing of a specific, quality part for everything replaced, it is an expensive and time consuming effort.
The sales on HiFiShark would indicate that a rebuilt Futterman is not as expensive as you might think, and a H3 like I am looking for sold for $400 in 2017. They do not come up often, so who knows. Given the amount of work and cost of parts, I certainly am looking for something at the lower end of what is mentioned above.
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