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HiI just bought my Fisher 400CX-2. Any recommendation on the tubes, particulkar on the 6V4. Thanks
John Keung
Follow Ups:
HiThanks for all respondence : )
I am now using Amperex EZ80 with D shape getter and a combination of Mullard/ Telefunken 7247. The 12ax7 are Valvo & Telefunken.John
Here's a very early CX of mine, after getting the full treatment a number of years back. The CX is slightly sweeter than the later CX-II, but a little too rounded and wooly at times on sharper arrangements. So, like you, I run a CX-II.
What process did you use for the cleanup? Sorry to ask you for a large posting.Thank you
Bill
Another view. But a blurry conversion of the original 35mm.
All the finishing steps are described somewhere in the archives.This one, one of the first 100 CXs off the assembly line, produced in 1959, I no longer have. But most will turn out like this unless there is corrosion or more than moderate oxidation of the cadmium plating.
It is hard to find these still with original tubing. For whatever reason, they get yanked out along the way.The original rectifier was a Mullard. It is nice, but a Holland Amperex is nicer still and gives a slightly livelier pace to the output, but still very sweet.
My experience is that the best sounding combination of line stage tubes are Mullard 7247s (UK made, not the RCA/US made ones) and TFK smoothplates, which is not too far off from the original complement. Others prefer all TFKs, including in the 7247 positions. But I think the particular strengths of both tube makers combine very synergistically when in this instrument. The 7247 is an increasingly difficult tube to source this precisely, however, so tubing options may be limited. If need be, the GE 7247 is a good alternative, but not as good as the others mentioned.
I have had several CX and CXIIs over the years, and a near minty one resides in my main system.
This instrument benefits greatly from a recapping of all the small electrolytics. The heater power supply is a little undersized, draws more current than I'd like to see for the parts specified, but should suffice. Be very protective of power supply integrity, as replacement power transformers are impossible to source, and rewinding is a $400+ proposition. There are also some big 2 watt carbon comps that should be checked and replaced if needed, as the sound can develop tonal irregularities if the drift grows significant. While recapping the films is optional, on the one example I did recap with fresh polyesters, the sonics were significantly improved while still retaining the beautiful voicing characteristics. The phono stage is surprisingly good. Somewhere in the archives are some improved methods of attaching the faceplate jewels that I came up with that does not involve the use of white glue.
Of all the preamps I have heard over the years (including modern high end models), the CX and CXII fall in the top echelon for overall sweetness of timbre and faithfulness to the musical nuances found in the source media. The CXII in particular does all this without losing one iota of raw audio information across the entire range. This, despite what some may view as an excess of tonal and sound management controls. It is in the first rank of vintage tubed preamps.
John, before bothering too much about the rectifier tube, you should first replace those old tired FP cans with fresh low ESR types. That will have a more dramatic effect on sound than any of the best NOS EZ80 tubes you could throw at it...Hendrik
Thats a beautiful piece. I think the tone of fisher pres is wonderful. Others think they are overally complicated and have an underrated power supply.The market obviously agrees with you. I would post to the fisher yahoo group many including alan at that group are great resources.
Im pretty sure stock was a mullard tele combo buti could be wrong. Also depends on what date the pre was made.
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