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Fisher 400, 500, 800 Sonic weakness?

sony6060

sony6060

Super Member
Banned
I have not connected my new Fisher 400, but will this week. Sonics are subjective.

However, I noticed use of ceramic coupling caps throughout the preamp sections including the RIAA phono stage and tone controls. The 7868 tube grids use poly type in the 400. Ceramic caps sounds good in a Marshall guitar amp, but not best for audio.

Has anyone converted their Fisher receivers to poly, paper/oil or teflon type capacitors?

I plan to use K40Y-9 in all positions less then RIAA stage that will use polycarbonate type. May change the 7868 tube grids to teflon and find out if better too.

As for the RIAA circuit it appears to limit bass response. Anyone modify the RIAA values?
 
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audiodon said:
The ceramics are not in the signal chain. Don't worry about them.
Click to expand...

Yes they are in the signal chain. Anytime a plate cap is connected to the grid in the next tube, it is called a coupling capacitor. This capacitor blocks DC and passes the AC audio.
 
They are out.......no game here

I'm out.[/QUOTE]

According to the Fisher 400 schematic and parts list from Fisher-

C67, 68, 69, 70, 75, 76, 77, 78, 79, 80, 83 & 84 are ceramic coupling capacitors in the audio chain. C81, 82, 93, 94, 95 & 96 are mylar in the audio chain. The RIAA & tone sections are also ceramic flat packs with internal resistors and capacitors in the audio chain. Also the FM multiplexer in & out at 12AX7 includes C218, C220, C221 & C222 that are ceramic are in the audio chain. Me thinks a poly type capacitor will make for a better sounding FM section too.

Per being 'out' you are stating to all that read the original post upgrading the ceramic capacitors that are known for higher distortion is of no importance? Perhaps Fisher has some distortion cancelling attributes from section to section I am unaware of?
 
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sony6060 said:
I'm out.
Click to expand...

According to the Fisher 400 schematic and parts list from Fisher-

C67, 68, 69, 70, 75, 76, 77, 78, 79, 80, 83 & 84 are ceramic coupling capacitors in the audio chain. C81, 82, 93, 94, 95 & 96 are mylar in the audio chain. The RIAA & tone sections are also ceramic flat packs with internal resistors and capacitors in the audio chain. Also the FM multiplexer in & out at 12AX7 includes C218, C220, C221 & C222 that are ceramic are in the audio chain. Me thinks a poly type capacitor will make for a better sounding FM section too.

Per being 'out' you are stating to all that read the original post upgrading the ceramic capacitors that are known for higher distortion is of no importance? Perhaps Fisher has some distortion cancelling attributes from section to section I am unaware of?[/QUOTE]

Stable and perfectly fine when the correct type is chosen.
A member here turned us on to that one! :yes:
Worrying over your same question!
Just because they all look alike, they work differently.
We used this type where film and foil would not fit or the value wasn't available.
http://www.mouser.com/catalog/specsheets/XC-600144.pdf
No need to be rude or argumentative to Don, he's a sweet heart and knows a LOT! :yes:
Seems to happen a lot when people don't like an answer.
Everyone has a way they like to approach things in this hobby as we have found! And a basis for that approach, sometimes objective, sometime subjective.
We figured that one out about an hour after we decided giving it a shot at restoring Daddy's old 500-C
You asked, he answered.

Phyllis
 
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PShuff said:
According to the Fisher 400 schematic and parts list from Fisher-

C67, 68, 69, 70, 75, 76, 77, 78, 79, 80, 83 & 84 are ceramic coupling capacitors in the audio chain. C81, 82, 93, 94, 95 & 96 are mylar in the audio chain. The RIAA & tone sections are also ceramic flat packs with internal resistors and capacitors in the audio chain. Also the FM multiplexer in & out at 12AX7 includes C218, C220, C221 & C222 that are ceramic are in the audio chain. Me thinks a poly type capacitor will make for a better sounding FM section too.

Per being 'out' you are stating to all that read the original post upgrading the ceramic capacitors that are known for higher distortion is of no importance? Perhaps Fisher has some distortion cancelling attributes from section to section I am unaware of?
Click to expand...



Stable and perfectly fine when the correct type is chosen.
A member here turned us on to that one! :yes:
Worrying over your same question!
Just because they all look alike, they work differently.
We used this type where film and foil would not fit or the value wasn't available.
http://www.mouser.com/catalog/specsheets/XC-600144.pdf
No need to be rude or argumentative to Don, he's a sweet heart and knows a LOT! :yes:
Seems to happen a lot when people don't like an answer.
Everyone has a way they like to approach things in this hobby as we have found! And a basis for that approach, sometimes objective, sometime subjective.
We figured that one out about an hour after we decided giving it a shot at restoring Daddy's old 500-C
You asked, he answered.

Phyllis[/QUOTE]

Rude? I did not use the word rude. You did though. Don did not explain any more than 'I'm out' (perhaps that is rude) dismissing the potential attributes of upgrades just like in any receiver and specifically the Fisher 400, 500 & 800.

'You asked, he answered'- Don's post is not correct- no coupling caps. From an engineering standpoint Don's post did not offer anything.

I never heard of an 'audio quality' ceramic cap. The ceramic caps have different temperature coefficients that can be critical in tuned circuits at RF frequencies, but not at audio. I have no concerns with ceramic capacitors in a shunt circuit to ground or applied to RF/IF applications.

However, I would like to hear from others if they upgraded their Fisher ceramic coupling caps before dismissing my original post. Distortion measurements of various capacitors have been posted on the internet with oscilliscope pictures. One can hear it & see it. And, some may actually like it, but I never read that anywhere as applied to high-end audio playback.

Edit- Being new here, perhaps this Fisher site is more about restoration vs modding for higher performance. When I finish the Fisher 400 mods in the FM tuner, audio & PS sections, I'll document the results in Tube Audio section of the AK site.
 
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sony6060 said:
I have not connected my new Fisher 400, but will this week. Sonics are subjective.

However, I noticed use of ceramic coupling caps throughout the preamp sections including the RIAA phono stage and tone controls. The 7868 tube grids use poly type in the 400. Ceramic caps sounds good in a Marshall guitar amp, but not best for audio.

Has anyone converted their Fisher receivers to poly, paper/oil or teflon type capacitors?

I plan to use K40Y-9 in all positions less then RIAA stage that will use polycarbonate type. May change the 7868 tube grids to teflon and find out if better too.

As for the RIAA circuit it appears to limit bass response. Anyone modify the RIAA values?
Click to expand...

I'm sorry if you took what I said the wrong way but you are giving off the vibe of wanting to argue with people that are offering up their feelings on what you asked about and you haven't even listened to your 400 yet!
It's like you're trying to prove some point.
If you already know that Mr. Fisher's parts are wrong then why ask, just go for it and change them all?!
Just weird to me is all I am saying and I am sorry.
Hope you find what you are looking for! :yes:
Merry Christmas! :banana:

Phyllis Shuff
P.S.: And I think you are right. From what we have learned from here, most of the guys are into restoring The Fishers and only making changes that help preserve them and their precious tubes and make them run cooler, not into possibly changing that oh so wonderful Fisher sound! :yes:
 
cer. cap.

Ceramic caps. can also be microphonic. I experienced that in the rebuild of my Dynaco. I kept the cap in the circuit but put a glob of silicone on each one.
They picked up the mere touch of my insulated probe stick as I touched them just like a cheap microphone.

Paul
 
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.
 
I'm in.....

I'd also like to know if there would be any discernable differences in changing out some of the ceramic caps for better quality ones. I've just started using my partially rebuilt 400 (haven't rebuilt all the top chassis can caps yet, only the black one) and I love the sound I get from this receiver. The phono section is quite good and is dead silent, even when the volume is turned way up. Playing CDs and the FM section also sound wonderful.

I've put in the 10 ohm cathode resistors and the 100 ohm screen resistors on each output tube. I have all the parts for the IBAM, just haven't installed them yet. I've replaced the coupling caps (plus others) with K-40Y and Cardas Clear caps and all the below deck lytics and diodes. So, I've done a lot already and like what I'm hearing.

I hate wasting time and money on things that don't make any audible difference, so I also want to know if there is anything further that can be done to improve the sound beyond the common upgrades and mods we already have discussed in depth on this Fisher forum. Thanks guys & gals.

Larry D.
 
idadude said:
I'd also like to know if there would be any discernable differences in changing out some of the ceramic caps for better quality ones. I've just started using my partially rebuilt 400 (haven't rebuilt all the top chassis can caps yet, only the black one) and I love the sound I get from this receiver. The phono section is quite good and is dead silent, even when the volume is turned way up. Playing CDs and the FM section also sound wonderful.

I've put in the 10 ohm cathode resistors and the 100 ohm screen resistors on each output tube. I have all the parts for the IBAM, just haven't installed them yet. I've replaced the coupling caps (plus others) with K-40Y and Cardas Clear caps and all the below deck lytics and diodes. So, I've done a lot already and like what I'm hearing.

I hate wasting time and money on things that don't make any audible difference, so I also want to know if there is anything further that can be done to improve the sound beyond the common upgrades and mods we already have discussed in depth on this Fisher forum. Thanks guys & gals.

Larry D.
Click to expand...

I started this thread. I rolled tubes & met all my requirements- beautiful sonics. GE 7868 & a few others were not for me + a wrong phased speaker (oops).

I read an audiophile at AA that upgraded a Fisher 500B coupling caps and complained the receiver had the life sucked out of it. Usually ceramics do not sound so well. Fisher must have spent a lot of time fine tuning these receivers. I will experiment with a new RIAA section and leaving the rest alone. Brimar CV4035 tuned the phono section exquisitely.

Some audiophiles perform upgrading the coupling caps at the 7868 or 7591 tube grids. Plus reduce the 7868 or 7591 330K grid resistors to 200K with .1uF caps.
 
sony6060 said:
I started this thread. I rolled tubes & met all my requirements- beautiful sonics. GE 7868 & a few others were not for me + a wrong phased speaker (oops).

I read an audiophile at AA that upgraded a Fisher 500B coupling caps and complained the receiver had the life sucked out of it. Usually ceramics do not sound so well. Fisher must have spent a lot of time fine tuning these receivers. I will experiment with a new RIAA section and leaving the rest alone. Brimar CV4035 tuned the phono section exquisitely.

Some audiophiles perform upgrading the coupling caps at the 7868 or 7591 tube grids. Plus reduce the 7868 or 7591 330K grid resistors to 200K with .1uF caps.
Click to expand...

I have reduced the grid resistors to 200K and use the 0.1uf Cardas copper film caps in addition to many Russian K-40 Pios in the phono section. I'm looking at doing as much as I can to improve an already great sounding receiver. I want the best out of the 400 without spending a mint on buying uber-expensive copper/teflon caps.

Larry D.
 
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I don't rehab them for the SQ as much as reliability and longevity. Kinda like putting new kingpins or shocks on a car(for those who who are 20-25 younger than the Fisher's we didn't have McPherson struts, or cardon joints, or independent suspensions back then in the average car). Bring it back to original spec (or as close as you can with today's parts). I'm not looking for it to sound like a McIntosh, or anything in the 5K-10K range. I want something that sounds good to me, works reliably, and will work for the next 20-30 years without problems.

That doesn't include changing every ceramic cap, or carbon resistor in the whole unit. If I wanted to do that, I'd a bought a Dynakit.
 
I hear ya.....

I'm not looking to make a Rolls-Royce out of it myself, but I am looking for a very nice sounding centerpiece for my living room system. I'd just like to get all I can out of it. I'm all for reliability and longevity and I'll probably put a start-up delay in it also.

My 400 is sounding REALLY good right now, so any further improvements are just more icing on the cake. I'm looking to make inexpensive or reasonable upgrades and mods. It would be nice to put together a sticky with only Fisher 400 upgrades and mods that can be done during a rebuild. That way there would be a concentrated amount of information in one place instead of spending hours sifting through threads to find out what works and what does not.

Larry D.
 
idadude said:
I'm not looking to make a Rolls-Royce out of it myself, but I am looking for a very nice sounding centerpiece for my living room system. I'd just like to get all I can out of it. I'm all for reliability and longevity and I'll probably put a start-up delay in it also.

My 400 is sounding REALLY good right now, so any further improvements are just more icing on the cake. I'm looking to make inexpensive or reasonable upgrades and mods. It would be nice to put together a sticky with only Fisher 400 upgrades and mods that can be done during a rebuild. That way there would be a concentrated amount of information in one place instead of spending hours sifting through threads to find out what works and what does not.

Larry D.
Click to expand...

The ceramic coupling caps present very little risk for failure. The sonic signature of ceramic can be a little brittle, but I do not hear it in the Fisher. A load of daisy chain 12AX7s has a tendency to sound a little dark due to the high miller capacitance. I suspect the ceramic caps give the Fisher a little needed snap. The four caps at the 7868 tubes have somewhat higher risk, but are high quality- I believe ERO from Germany. I measured no leakake, they stay for now. NOS 7868 are not at risk for runaway like new manufacture 7868s. The RIAA rebuild is worthy and I have Sonicaps plus Russian K40Y-9.

Although I measure no leakage with the PS caps, I will change out to new can type. Can type from CE look stock. I will place a new cap inside the insulated can to maintain the stock look & place the other matching cap for the B+ doubler under the chassis. I will try a 1HY choke and 10uF poly cap on B+ doubler output & listen. I will also replace the bias caps at 1000uF input and 4000uF output (CRC).

Sonics were improved by changing tube types. I posted what fine tuned the Fisher 400 to my preference in another post a few days ago.
 
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sony6060 said:
The ceramic coupling caps present very little risk for failure. The sonic signature of ceramic can be a little brittle, but I do not hear it in the Fisher. A load of daisy chain 12AX7s has a tendency to sound a little dark due to the high miller capacitance. I suspect the ceramic caps give the Fisher a little needed snap. The four caps at the 7868 tubes have somewhat higher risk, but are high quality- I believe ERO from Germany. I measured no leakake, they stay for now. NOS 7868 are not at risk for runaway like new manufacture 7868s. The RIAA rebuild is worthy and I have Sonicaps plus Russian K40Y-9.

Although I measure no leakage with the PS caps, I will change out to new can type. Can type from CE look stock. I will place a new cap inside the insulated can to maintain the stock look & place the other matching cap for the B+ doubler under the chassis. I will try a 1HY choke and 10uF poly cap on B+ doubler output & listen. I will also replace the bias caps at 1000uF input and 4000uF output (CRC).

Sonics were improved by changing tube types. I posted what fine tuned the Fisher 400 to my preference in another post a few days ago.
Click to expand...

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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