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Differences in phono playback through the 500C were not huge. The sound was just slightly better in the areas of noise floor, dynamics and perceived distortion levels. Nothing to get excited about though. The MJQ LP was a bit more incisive and articulate and the highs airier than through the 800B. Going from the 500C to the 400, I would be hard pressed to claim I heard any large differences. I think the 400 is somewhat less mechanical sounding than the 500C, consistent with this same observation of the linestage. In addition to the difference in the output tubes already mentioned, the other difference that could possibly explain this are the different coupling caps used in the phono stages of all three receivers. The Fisher 400 uses the barrel-shaped German ERO FOL foil caps. The 500C has dark-brown/black caps apparently labeled RT3 (hard to make out exactly). The 800B has chocolate brown caps with white stripes around the ends. I don't know the brands of these two latter caps. As anyone who has changed coupling caps can attest, these could be responsible for the sonic differences. I suspect the ERO FOL caps in the 400 are superior.

The overriding sense of LP playback through all three receivers is generally pleasant. The music's crescendos are fairly well served but not with the best of resolution. If pressed, I would have to say that the phono stages in all three of these Fisher receivers are serviceable but certainly lackluster in comparison to even the less expensive high-end phono stages of today's preamps.

I confess to borrowing the "lackluster" adjective from a friend who's been using a Fisher 500 phono stage for LP playback into his DIY tube line stage preamp. A turntable inferior to my Thorens further hampers his results. If I were using a Fisher receiver as the amplifier in my main system, I would have to get some sort of budget outboard phono stage. These are hard to come by at a price that makes sense for use with these Fishers. The old Radio Shack "cigarette pack" phono stage might do the trick if they are still offering it in their catalog (probably not).

Now comes the difficult part of the review: comparing tuner sections. The FM sections of old tube tuners/receivers are notorious for needing alignment after all these years. Finding a qualified technician to do this is harder than finding someone to just repair your tube amp. Here is where my friend Charlie King comes in. Charlie has an electrical engineering degree and worked back in the 1970s on actually setting up the broadcast studio for WPKN in Bridgeport, Connecticut. Since then, he's been active in the Connecticut Audio Society, serving our members and others with tube equipment repair and design, open reel tape deck (especially Stellavox) repairs/modifications and tuner alignments.

Charlie came over one day and we carefully listened to the tuners in all three receivers. He pronounced that the 500C and 800B did not need alignments but the 400 did. This turned into quite a sticky problem. We couldn't get the 400 to lock onto the 19kHz pilot carrier signal on weaker stereo stations. You could hear distortion compared to the other tuners. Charlie performed an alignment but it really didn't make things any better. We now began looking at voltages on the tubes in the multiplex section. Without going into painful details, suffice to say that we chased our tails for many an hour due to an oversight we made in reading the schematic. However, we also found a typo in the schematic! The B+ voltage going to the multiplex section from the 40/40/40/20 multi-section filter capacitor in the power supply is listed as 390 volts. It should be 290 volts. Ugh!

We tried increasing the gain of the first tube in the multiplex section (12AX7) by changing the resistor values but to no avail. We were really getting frustrated and testy but remained determined to get to the bottom of this problem. Finally, Charlie said he would take it home again and check a few more things. This time, he did the alignment feeding a weaker signal from his FM sweep generator to simulate the weaker stations. He found it did need some further tweaking this way and that cured it.

Charlie noticed an interesting thing about the stereo multiplex sections of the receivers. The 800B used two 12AT7s and one 12AX7, while the 500C and 400 used three 12AX7s. However, all of the other parts values are the same. He theorizes that Fisher decided to simplify their inventory needs by eliminating the 12AT7 from this circuit, allowing them to just order 12AX7s in large quantities. Charlie then went on to demonstrate that the 12AT7 in the V100 position of the Fisher 400 multiplex actually improved the performance over the stock 12AX7. It allowed the tuner to lock on to the station better. So, here's one tweak you can try in your old Fishers if you experience this problem on weaker stereo stations.

Fisher's published specs for the FM section sensitivity of the three receivers are as follows:

Fisher 800B 2.5 uv, 3 IF stages
Fisher 500C 1.8 uv, 4 IF stages
Fisher 400 1.8 uv, 3 IF stages

Based on the specs, one would predict that the 500C offers the best FM performance. I did in fact find this to be the case. The 800B was the least sensitive, picking up fewer stations than the other two receivers. Weaker stations in my listening area such as 90.5 WNPR and 102.9 WDLR were received better on the 500C than on either the 800B or 400. Sound quality was also best on the 500C. According to comments on Audio Asylum's Vintage Gear group, the Nuvistor FM version of the 500C may not sound quite as good.

Before bestowing the crown on any one of these receivers, I would like to stress the strong family resemblance in sound and performance among the three. These classic Fisher products live up to their advertising and are a testimony to the manufacturing prowess of United States industry in the 1960s.

The Fisher 500C did edge out the other two receivers, most notably in FM and linestage performance. Phono stage performance was uniformly mediocre. The 800B clearly is a collectible piece but since its FM performance is the weakest, I would only recommend it for serious AM listeners. The 400 has slightly different qualities than the 500C, which some might prefer, but my vote is for the 500C.

One important design aspect that may explain some of the 500C's superiority can be measured with a ruler. Both the power and output transformers are larger on the 500C than on the 800B or 400. Its plate stacks measure 2 7/8" for the power transformer and 2 1/2" for the output transformers. On the 800B and 400, the power and output transformer measurements are 2 1/2" and 1 7/8" respectively. Larger output transformers are often associated with wider bandwidth and improved dynamics.

As a final curiosity, I decided to put the original Telefunken 12AX7 tubes back in the linestage and driver stage of the Fisher 500C. At the prices that Telefunken 12AX7 tubes sell for these days, it is hard to justify using them in these receivers. Much as I did not want to admit it, I must dutifully report that the original Telefunkens really do take things up a whole notch. With the Telefunkens, there was more presence and air. The sound was more involving, natural and refined. If you're using a Fisher receiver in your main system, I would recommend using the Telefunkens. It might be a good idea to experiment with other old stock brands, too. I have also found Fisher-labeled Sylvania 12AX7 tubes in some of their products (i.e. Fisher X-202B), so these would be worth a try.

Who would be a customer for these receivers today? Of course, there are the pure collectors who just want to fill up their homes with every model they can find but such buyers are not the targets of this review. I would recommend any of these receivers (already restored) for someone's first venture into a tube-based system. Even the most jaded high-end audiophile, especially solid-state folks, could expand their musical horizons with a Fisher tube receiver in a second system for the den or bedroom.