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In Reply to: RE: Futterman H3 Question posted by Fishfood on November 20, 2009 at 20:38:55
Hello,
I have an H3 and Piquet refurbed ESL57s. I would not call the that combo muted at all. It is extremely revealing in the midrange. It could called a bit grainy but not muted.
There are numerous good-all couplers and the big electrolytic cans that need to be changed. I will eventually put good quality film caps to replace the electrolytic cans in mine.. if you not have done this work you should before you pass further judgement.
What output tubes do you use in your H3?
Follow Ups:
6HB5s. I just opened it up with my local tech and it's absolutely been redone...actually completely rewired. Totally clean. It's beautiful. On the schematic it show a couple of things have been taken out of the circuit but I left that with the guy that's checking it out. I think I blew a tube yesterday, there's suddenly a ton of distortion equally on both channels so we think its either the OA2 or 6EM7, but it could also be a power supply problem. He's checking it out this week and then we are going to listen to it together and see how the midrange is.
What output tubes do you use?
It sure sounds like you have a problem with a bad ground at the speaker terminals. Check and see if the speaker terminals have a common ground connection. If so, I suspect it is bad.
Thanks. Just got a call and there was a fuse problem of some sorts that they worked out. I'll start listening again tomorrow and report back how it sounds long term....
Hi,
I use the 6FW5 octal sweep tube. Make sure the regulator tubes match the circuit as the labels may not really indicate the real tubes. i.e., my screen regulators are 6dr7s yet the chassis is labled 7734.
He used whatever tube was in fashion(cheap, I understood that he tested new tubes for some manufacturers or distributors) and did not change the silksreen on the chassis.
Change the diodes in the B+ and bias as well they are old types and leak.
Good luck with it , it really is a very nice amp.
What do you do about a power switch? I messed up a tube by mishandling plugging and unplugging. Did you install a power switch or do you have online on the cord? Thanks.
Thanks for the tips!
As I recall, based on the last Futterman amps I owned which were the giant Prodigy OTLs once made in Texas, the necessary coupling capacitance is of fairly high value, such that one would be hard-pressed to achieve the required value with film caps. What I did was to bypass the electrolytics with a 10uF Infinicap. High voltage types are not necessary in this application; 200V rating is overkill. Then I bypassed the Infinicap with some smaller value film types. This really paid off in sound quality. Nowadays you might consider use of even higher value Mundorf film caps made for speaker cross-overs in this application, or motor-run caps.
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