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Which Fisher tube receiver had the best FM stereo tuner?

monkboughtlunch

monkboughtlunch

Super Member
Which Fisher tube receiver had the best FM stereo tuner? Was the FM topology different in each or similar?

Has anyone had a chance to compare the FM on these models?

500-B
800-B
500-C
800-C
400

I've also read that the original 800 (not B or C) is the only one that had a "Golden Cascode" used in its FM tuner, but this apparently required an external MPX adapter. How does the original 800s FM sound compared to the later B and C series?

Also, how does the AM sound quality differ, at all, when comparing the 800B to the 800C?
 
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Looking at the old catalogs, The 500C and 800C seem to share tuner sections with the R-200 AM/FM tuner. That's the "Stereo Beacon", three section FM variable capacitor, etc.

The 500B and 800B weren't advertised as having the Cascode or Synchrode front ends like the better contemporary tuners.

http://www.hifimuseum.de/fisher-handbook-1963.html

The best Fisher tuners, according to specifications and design features remain the FM-200B and FM-1000 (and the latter's rack version).

Note that is common practice for the less impressive performance specifications to reflect less labor at the factory tweaking the adjustments before shipment. A specialist can sometimes make big improvements on measured performance compared to the published specs - you just have to pay for it. That's why I shop for design features rather than advertising specs.
 
The Fisher Golden Syncrode tuner section with two Nuvistor tubes in the front end was introduced in 1964 for Fisher 500C & 800C receivers. This is the best tuner from a specification standpoint. The triode Nuvistor tubes have high gain and a low noise floor. The 6HR6 that follows downstream is a remote cut-off pentode that is high gain and resistive to overload conditions vs the sharp-cutoff 6AU6 tube installed in earlier tuners. Some earlier tuners also used a 6HS6 and a 6BA6 in this position, however just mentioned to be correct.

Note- I have no experienced overload issues with any Fisher FM tuner and a 'local' FM antenna connection exists for this issue on Fisher receivers.

The later Fisher 400s have an additional 6AU6 IF tube labeled V6 in the tuner section. Although not using Nuvistor tubes, the FM tuner is excellent with good sensitivity.

All the Fisher FM stereo tuner sections sound good thanks to the overall design and the stereo multiplexer. IMO the Fisher tube type multiplexer in the 400/500/800 stereo receivers is the best from that era.

I am more interested in the sound signature of each series receiver than the FM tuner design. All FM tuners are sensitive and sound excellent.
 
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My reference is-
wopontour.shawwebspace.ca/asset/view/4033/fisher_cascode_front_end.pdf (same as your link).

Although the 'Golden Cascode' verbiage was used earlier, the Nuvistor equipped front end was stilled called Golden Cascode in the 1964 Fisher 500C.

That FM tuner is a very good design.
 
This says the 800C had the Synchrode front end in 1964:

http://www.hifimuseum.de/the-fisher-book-1964-1.html

The same model year (1964) the FM-200B and FM-1000 used the Golden Cascode from end with two nuvistors.

My argument for looking to design features on vintage gear when purchasing is that the effects of aging will gradually swamp the design and the skill and thoroughness of the tech doing the rebuild can restore it up to the original as-shipped levels. Given you get a good tech (or are one) the original design is your best guide to refurbished sound quality. A bad tech may fail to restore the glory of an aged piece of equipment but a great tech can meet or exceed the original. One can do major redesign (adding an additional IF stage for example) but its no longer the same design.
 
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larryderouin said:
Jim; The 500C is the only model that carried 6CW4 Nuvistors. The 800-C Used 6GK5/6AQ8 Front end. Neither of my 800-C's (series 103xx and 335xx) have a nuvistor. Actually 1957 was the year for the 1st "GOLDEN Cascode" Tuner.

You might want to read this......http://wopontour.shawwebspace.ca/asset/view/4033/fisher_cascode_front_end.pdf
Click to expand...

It appeared that the 800-C would be the ultimate receiver and I cannot figure out why they used a "lesser" front end than on the 500-C. The 500-C Nuvistor front end was also used on the 600-T.

The wopontour web site is very interesting.
 
The sales literature linked to above say that the 500C and the 800C have the same tuner except the 800C has AM too.

They are both like the R-200 only the 500C deletes the AM.
 
This is a great discussion, but for our needs, much of it is academic. Unless you are listening to mono FM, the practical noise floor of FM stereo signals is controlled by the noise in the AM stereo subchannel information of the composite FM stereo signal, as received by the tuner, well before the noise level of any of the front ends being discussed becomes an issue. This is easily demonstrated by how much quieter the reception is for FM Mono versus the same station decoded in FM Stereo, on the fringe of the reception area.

My own 400 receiver -- the front end of which is not a cascode design -- displays better than advertised sensitivity for quieting, being virtually as sensitive as any of the "best" front end designs Fisher used in all of its various offerings. Still, it is the multiplex noise that determines my satisfaction of reception -- not the noise or sensitivity of the unit's front end design.

Looking backwards from a practical standpoint, while the use of Nuvistors did represent a technological advancement at the very least for marketing purposes, and did even allow for theoretical improvements in performance, their use hardly made the equipment they were used in clearly standout over non-Nuvistor equipped units, and more importantly, have comparatively short operating lives as compared to the typical 6DJ8/6AQ8 offerings.

This is even true of the 6HA5 used in the 400 receivers -- and why Fisher (as but a partial answer) killed the B+ to the front end in the later 400 offerings when FM was not selected, to help try and preserve the life of the tube.

The RF amplifiers in FM tuners operate at very high gain (particularly without a station tuned in), and therefore out of necessity, at relatively high current levels -- which creates significant heat in the tubes used. With the small package that Nuvistors represent, high current levels can spell very high operating temps. IIRC, Fisher then wisely used their Nuvistors in the oscillator and mixer positions of the front end, leaving the RF amplification duties to more traditional tubes in those unit where Nuvistors were used. Personally, for the practical matters involved, I still prefer non-Nuvistor equipped tuners as the best compromise of performance and long term dependability.

Dave
 
Is there any difference in sound quality between AM in the 800B vs the 800C? I read that because the 800B had the "AM/FM" stereo capability, it's AM may have been engineered to a higher standard to match the FM signal as best as was possible when in "AM/FM" stereo mode. So is there any difference in the AM engineering / sound quality in the 800 B vs C? Do the schematics reveal any significant differences, or is the "800B AM is better" an urban legend?
 
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The difference (if there is one) will be in the response of the IF stages, and how many of them exist. If there is a "wide" setting for the IF response characteristic, then the AM section was designed to provide the best possible fidelity.

Dave
 
dcgillespie said:
My own 400 receiver -- the front end of which is not a cascode design -- displays better than advertised sensitivity for quieting, being virtually as sensitive as any of the "best" front end designs Fisher used in all of its various offerings.
Click to expand...
You can't compare sensitivity numbers measured live to Fisher published specs for the 400 (or other more expensive models for that matter).Lots has changed in the equipment and methodologies for the determination and accuracy of these specs since 1959. As such only actual "side by side" bench measurements of completely restored tuners could reflect any sort of true "apples to apples" comparison. But you can rest assured using identical test methods you may have utilized for your 400 that the FM-200B and FM-1000/TFM-1 models would likely show similarly improved results (from 1959 specs) that will easily surpass those of the 400.
dcgillespie said:
Personally, for the practical matters involved, I still prefer non-Nuvistor equipped tuners as the best compromise of performance and long term dependability.Dave
Click to expand...
Personally, I have found the exact opposite is true and have found the Fisher front ends that used the cascoded dual triode 6DJ8 sections combined with a pair of 6CW4 nuvistors (such as the FM-1000/TFT-1 and 200B FM stereo tuners) to be not only more reliable but superior in most measurable performance metric. (as well as "by ear")

If any "compromise" exists it would be within the Fisher stereo receivers and due to their very "integrated" nature of trying to pack ALL that receiving hardware (inc. AM in the case of the 800) AS WELL as the pre-amp and main amplifications stages onto a single chassis. So there was simply less available real estate for additional I.F. and limiter stages.

These very same developments (under the guise of "advancements") spurred the initial "integrated vs. separates" debates that continue even to this day in vintage circles. But when it comes to Fisher FM performance I have yet to see/hear a 400/500/800 receiver that can hold a candle to the separate FM-200B let alone the venerable FM-1000/FMR-1 (which IMHO is Fishers BEST FM tube tuner)

JMO

WopOnTour
 
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All Fisher tuners with the modern multiplexer have the potential to sound as good as any model IMO. I work on all the Fisher FM tuners. I tune the tuners for best sonics. I am not sure if anyone else does this beyond alignment by the book.

I am taken with the 500C tuner because it is a piece of art and a hot performer. The ultra sensitivity does show up in fringe reception areas. I spend summers at a more remote NY location in a valley vs NYC receiving the same NY radio stations.

I have owned a lot of gear with Nuvistors including the Scott tuners, ham radio receivers, the Ameco Nuvistor preamps & even CB radio gear. I have noticed the Nuvistor tube does appear fail before other tubes as mentioned by Dave. However, at $5-8 each, 20 years vs 30 years life is fine with me.

Fisher FM tuners of less than the 500C design should sound as good as any Fisher tuner with the MX-65 style multiplexer and in the case of the later Fisher 400 with the extra IF/discriminator tube.

I change the audio coupling capacitors and replaced the multiplexer 12AX7 audio out tube with a RCA 12AT7 black plate, replaced the Telefunken 6AU6 with Tung Sol 6AU6, kept the Tele 6BA6 (Fisher 400, RCA 6HS6, etc in other models)) and have no preference of brand in the RF amp, and mixer positions.

Yes, tube rolling, careful alignment and the capacitor change does make for an even better sounding FM Fisher FM tuner. Try it.......
 
This has a a great read so far and learned a lot. Wondering what caps in my FM200B are now and what I might want to change, sounds ok to me though as is. :scratch2:
 
J -- Thanks for your input. For me, when you get beyond all the Fisher marketing tools as to what name they call a given front end unit, the performance is remarkably similar in terms of IHFM (that is, usable) sensitivity, for the majority of their stereo offerings. For example, the 200B tuner with its cascode RF amplifier stage and separate nuvistor mixer and oscillator stages has a usable sensitivity specification of 1.6 microvolts. And yet my own 400 receiver with a single stage RF amplifier, cascade coupled into a single combined mixer/oscillator stage has been clocked at a usable sensitivity of 1.5 microvolts, even though the unit is rated at 1.8 microvolts. No doubt that the cascode front end of the 200B could do even better than my 400. But at this point, we're almost splitting hairs.

I do not know what the IHFM sensitivity specification is for the FM1000. But usable sensitivity of an FM tuner is principally set by the gain of the RF front end. For a decade or more, this was almost always achieved by a cascode RF amplifier stage in quality tuner designs. However, when the very high Gm 6HA5 became available, Fisher changed over to this tube for RF amplification duty, since it was able to still produce very good performance, yet with a simpler design.

However, I freely admit that I have never had the pleasure of owning/listening to a 200B for any significant length of time, so I would hardly try to refute what you know from experience that I do not have.

As for the durability of nuvistor tubes, my input comes from servicing maybe one and a half or so dozen tuners which used these tubes -- primarily Mac, but also some Fisher units. The difference may come in by way of the test standards used, but I find these tubes to come in with anywhere from dead heaters, to notably low Gm, as tested under conditions published by tube manufacturers. How commercial tube testers do with these tubes, I don't know. Against that however, I find the tuners using some classic combination of 6DJ8/6AQ8 tubes to most often have these tubes be just fine.

To be fair, I will need to check how Mac used their nuvistors, versus how Fisher used them. Fisher never used them in the RF position, which can be pretty hard on a tube, where as I believe Mac did IIRC.

In any event, I appreciate your comments and your specific experience with nuvistor equipped Fisher tuners.

Dave
 
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