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anyone compared or know the differences between The Fisher X-101 with the old brass faceplate and the input jacks underneath, vs the X-100 aluminum faceplate amp?
Steve
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The earliest brass faced Fishers, "The 101" and X-101 and X-101ST, had lay-down trannies by Todd Transformer Co., the same tranny maker for the highly desirable Fairchild amps. Their EIA number begins with #926___. The 3 numbers after the 926 should indicate the mfg. date. If there are another group of numbers, they can be the in-house Fisher design/mfg. spec #s. These 926 opts are truly golden, wide bandwidth delights.
The X-100 versions I recall had "stand-up" type trannies, with probably a different tranny maker. Note the numbers and we can research them later.
The aluminum fascia units tend to have ss diode, voltage doubler power supplies, no more GZ-34s. They can still sound very nice. Power supply caps and diodes have come a long way. Resto and upgrades could be very worthwhile. Noting the tranny numbers can come in handy for historic knowledge...
Some of the very first 101 amps actually have two different opt trannies on the same chassis ! Not only the wire leadout differences, but the E-I tranny iron laminations and size can differ. When I collected these, many lunar eclipses ago, I had to buy a few units to actually pair up the opt iron. The phono preamp sections on the brass fascia units are very worthy of resto. Remembering these units run hot, I advise using taller than stock "feet" under the amp chassis for better ventilation, which will also allow a better grade of cables to fit underneath...
Thanks, very informative! I will have to go check OPT numbers.The thing that got me asking was seeing the X-100 with aluminum faceplate, 5AR4 rectifier, and, sure enough, stand up trannies, here on the auction site:
Edits: 12/12/16
I like the early amp. Cant lose with a tube rectifier and good sounding 12AX7s. Unfortunately the on the later amp the only good sounding 12DW7 I heard are extremely rare CBS manufacture.
According to the service manual linked below, the early Fisher X101 used 3 12AX7's and 3 7025's. So, essentially 6 12AX7's along with the 7189 outputs and the 5AR4 rectifier. While the X100 uses 4 12AX7's and 2 12DW7's (7247)in the preamp section. The 7247 is a dual triode with each bottle being half a 12AX7 and half a 12AU7 inside. You can search here for posts about the benefits of this. I have no idea if the transformers are the same between the two models or not. I have never heard one of the early x-101's but I do have the X-100...
good luck
--Matt
"When you think everything is someone else's fault, you will suffer a lot."
--Dalai Lama
I wish they would have used a 7247 for the phase-splitter driver for the output section.I have a 101 that I bought for a dollar at a hamfest in 1989 and I left it stock. I have rebuilt a few but mine has all 12AX7s.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I have 2 X101 amps waiting for restoration, and just became aware of the X-100. Thanks!
IF you really want to do them up, think about a rethink rather than a 'restore'.Don't waste money on NoS 7189s or A's, the EL84M is a fine neutral tube.
In particular think about using a low-gain high GM tube to drive the EL84Ms, not a high gain low-gm type like the 12AX7/7025.
Why? You will get lower distortion, and can use less loop NFB.
You do need to have heater current in reserve.
But, IF you drop the GZ34 rectifier and go with SR SS diodes, maybe even Schottkys, you can use its 5V heater rail inveigled to 6.3V, to heat the low mu High GM valve.
You can also get much higher storage in the PSU because you no longer have any serious PIV issues. Modern 400 to 500V / 100 degree electros have a lot more uf than the Fishers had as OEM.
Even PP film caps can exceed the original values and still fit. If there's no choke-filter in the PSU think about adding one if it will fit. CLCC or CLCCC.
If there's enough heater current with that extra rail you could use a 6CG7/6FQ7 - with a FET CCS under it - in perfectly balanced LTP mode.
Much nicer sound, higher headroom, far tighter bass.
If they have an RIAA section, find Eli's fet assisted version - here at AA - of the 'RCA twin 12AX7 stage' and make those mods too.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 12/10/16 12/10/16
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