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Fisher 400, 500, 800 Sonic weakness?

derekva said:
With regard to smaller-value ceramics, why not mica? They're as long-lived as ceramic but without the sonic nasties.

-D
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I suggest you use polystyrene's for the small values. Silver Mica's suffer from ionic migration problems over time. The polystyrene's are available in 630volt versions (http://www.justradios.com/polystyrene.html) which can be used as coupling caps and they have better audio qualities as well.

Fisher chose their ceramics very carefully. Likewise they used high quality glass resistors in the signal path. Change these with caution and reason.
 
After changing the signal caps with a mix of hovlands,audiocaps,jenzens and doing the 220k from the 330k mod I have found the sound to objectively go from fuzzy to studio standard. A year ago I griped and stubbornly defended JJ's 7591's.
I see the light in the tunnel and its not a train.
In general any design made by man may be improved upon.
My goal was to bring a instrument, player, singer, orchestra into my den to perform as clearly and as accurately as the the record was cut.
Not to hijack a thread, but other then swapping caps the greatest sonic improvement in have found as recently as today was installing a three prong plug in my 101c. Back in the day a real danger of shock from a power cord. I installed it and hey not only was it safer but the unit sounded a lot better.Despite what others may feel as a degration of vintage equiptment

Other than that I have no guilt in replacing a 60 year old piece of wax paper,sand or mylar that stands in the way of what I consider better sonic preformance or longer tube life.
I'm getting my wish.
 
drewbolce said:
I suggest you use polystyrene's for the small values. Silver Mica's suffer from ionic migration problems over time. The polystyrene's are available in 630volt versions (http://www.justradios.com/polystyrene.html) which can be used as coupling caps and they have better audio qualities as well.

Fisher chose their ceramics very carefully. Likewise they used high quality glass resistors in the signal path. Change these with caution and reason.
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Correct me if I'm wrong, but I thought ionic migration is really only a problem over long periods of time (e.g. 40-50 years...by which time you should be recapping gear anyway). Is this not the case?

Thanks for the link to the polystyrenes. I'll try those out the next time I'm recapping small values.

-D
 
bhamham said:
Please, please don't modify your Fisher receivers... don't add thermistors to lower the mains voltage that has increased since Avery's days. Don't do individual bias schemes to increase the longevity of your output tubes or lower the grid resistors to a safer level. Those tubes are still a dime-a-dozen like they were in the 60s, don't you know? And, never ever raise the capacitance in the power supply - just keep it the way Avery designed it, bearing in mind he wouldn't want the smaller, but bigger and better designed caps that are available today.

Engineering, scientific reasoning shouldn't be allowed especially from argumentative vibes. No, we should discuss dark sciences like black plates, cables and half assumptions based on some kind of wizardry like it sounds better. Better yet, let's go back to counting with beads don't want to modify the abacus.
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NO one here has suggested that from what I can gather? :no:

Phyllis
 
TPStatic said:
After changing the signal caps with a mix of hovlands,audiocaps,jenzens and doing the 220k from the 330k mod I have found the sound to objectively go from fuzzy to studio standard. QUOTE]

Interesting on fuzzy. My Fisher 400 was a little lack luster. I swapped out tubes and brought in a fairly sharp focus. Tung Sol 12AX7 square getter grey plate at the phase invertors made for a fair amount of that focus. I think the ceramics add a little needed 'snap' to the sonics in the Fisher 400, but have not any imperical data. Usually ceramics are not good unless in a guitar amp.

I have a SS amp that will ultra detail music and sounds very good if a little lean compared to the Fisher 400. I only heard one vintage SS amp (receiver) I would keep out of about six higher-end receivers.
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12ax7

I have a half a drawer full of matched pairs of 12AX7 types to try out after I finish with the rebuild of the 400. Usually, if I rebuild using better than average quality parts, then I don't hear much difference when I roll good quality tubes. Differences seem to be more subtle.
That's past experience, but I'll try rolling tubes after the rebuild. Who knows, maybe the tubes will make a defined difference in the 400, even with the better electronics installed.

Larry D.
 
idadude said:
I have a half a drawer full of matched pairs of 12AX7 types to try out after I finish with the rebuild of the 400. Usually, if I rebuild using better than average quality parts, then I don't hear much difference when I roll good quality tubes. Differences seem to be more subtle.
That's past experience, but I'll try rolling tubes after the rebuild. Who knows, maybe the tubes will make a defined difference in the 400, even with the better electronics installed.

Larry D.
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Perhaps my Klipsch horn speakers pass details easily.
 
idadude said:
I have a half a drawer full of matched pairs of 12AX7 types to try out after I finish with the rebuild of the 400. Usually, if I rebuild using better than average quality parts, then I don't hear much difference when I roll good quality tubes. Differences seem to be more subtle.
That's past experience, but I'll try rolling tubes after the rebuild. Who knows, maybe the tubes will make a defined difference in the 400, even with the better electronics installed.

Larry D.
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Perhaps my Klipsch horn type speakers pass details easily.
 
sony6060 said:
Perhaps my Klipsch horn type speakers pass details easily.
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I was using K-horns when I was uber-modifying the electronics of an Eico HF-81. When I'd just changed the coupling caps you could still hear the obvious differences when rolling tubes, but when I'd modded and upgraded a good bit of the HF-81, then tube rolling only made very slight differences.

If I had it to do again I'd not make as many changes as I did with the Eico. I over modded in some areas and it was not to the sonic benefit of the amp. It became slow and muddy instead of its normal quick & snappy. I'd used too much capacitance when replacing the can caps. A friend came over with his homemade EL84 amp and kicked the HF-81's butt. I sold it a few weeks later.

I don't think that replacing these smaller ceramic caps will take away the snappiness of the 400. It sure wouldn't cost much to find out. Then, if it does, you can always put the ceramics back in as long as you carefully remove them. I think I will try out replacing a few after I replace the rest of my electrolytics on my 400.

Larry D.
 
idadude said:
I was using K-horns when I was uber-modifying the electronics of an Eico HF-81. When I'd just changed the coupling caps you could still hear the obvious differences when rolling tubes, but when I'd modded and upgraded a good bit of the HF-81, then tube rolling only made very slight differences.

If I had it to do again I'd not make as many changes as I did with the Eico. I over modded in some areas and it was not to the sonic benefit of the amp. It became slow and muddy instead of its normal quick & snappy. I'd used too much capacitance when replacing the can caps. A friend came over with his homemade EL84 amp and kicked the HF-81's butt. I sold it a few weeks later.

I don't think that replacing these smaller ceramic caps will take away the snappiness of the 400. It sure wouldn't cost much to find out. Then, if it does, you can always put the ceramics back in as long as you carefully remove them. I think I will try out replacing a few after I replace the rest of my electrolytics on my 400.

Larry D.
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Interesting on the over capacitance of the power supply. I suspect a PS simulator could uncover the issue. I use a current step in the PSUDII power supply simulator and look for a 16ms or better voltage recovery.

Let me know of your findings with the Fisher 400. I do find the Fisher 400 a little dark sounding, but very nice sonics. I am going to try Sylvania 5751 black plate 3 mica in the input & tone amp positions. Tubes should arrive next Wednesday.
 
Regardless if there are ceramics in the signal path or not all my Fisher 800B's tone/line stage does is makes things sound more voluptuous and warm. Nothing brittle or thin about it what so ever. My Yamaha C-4 pre straight into the Fisher SA-100 power amp is clean and accurate. I like both, if anything flat, lousy recordings seem to get a little breath of life in them going through the 800B where quality recordings sound excellent and how they are intended through the SS pre/SA-100 combo :yes:

If you want to start replacing all kinds of different caps/parts then by God eat your heart out! :D I know I'm not going to. At that point I'd rather start from scratch. To each their own.

Just for the record my 800B has 0.1uf K40 PIO's for output couplers
200k grid resistors
Individual Bias mod running EH7591's at 35ma each
716P OD's in the line/tone stage
double mica rca black plate 5751's in the line/tone stage
Completely recapped voltage doubler/power supply.
 
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