eq_shadimar Posted October 12, 2001 Share Posted October 12, 2001 Okies tube guys. I have a chance to get a Fisher 500B Tube Receiver. I know absolutly nothing about tube stuff other than everyone says I should get one to power my Cornwalls . Is this a good starter point? The cost would be $150US. Thanks, ------------------ FOR SALE OR TRADE COMPLETE R*3 SYSTEM FOR 3 HERESY'S Main System - Cornwalls (L/R main) RC-3 RS-3's (white) SVS 20-39CS Harman Kardon AVR 510 Hafler P505 (running sub) ProMedia 4.2 v400 for PC Quote Link to comment Share on other sites More sharing options...
GeorgeC Posted October 12, 2001 Share Posted October 12, 2001 I have the 500c. Tried them with Cornwalls, Legend 30s, Dahlquist DQ-10s, JBL L100s and Quad ESL 57s. Makes all of them sound wonderful. I also tried these with my Denon 5700, Quad 405, Naim Nait2, and Decware Zen tube amp, and to my ears and a friend's, the 500c sounded the best of all. Now, about this US $150 - that's a heck of deal - let me know if you don't take it, I'd be interested! Quote Link to comment Share on other sites More sharing options...
eq_shadimar Posted October 13, 2001 Author Share Posted October 13, 2001 Cool thanks for the information. I will let you know how it turns out. Laters, ------------------ FOR SALE OR TRADE COMPLETE R*3 SYSTEM FOR 3 HERESY'S Main System - Cornwalls (L/R main) RC-3 RS-3's (white) SVS 20-39CS Harman Kardon AVR 510 Hafler P505 (running sub) ProMedia 4.2 v400 for PC Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted October 13, 2001 Share Posted October 13, 2001 I have a Fisher 500c, which I rebuilt (basically replaced bypass caps + other critical caps with high quality ones, bullet proofed the grid bias, slightly increased the grid bias voltage to 20.5 volts to help prevent overracing those precious 7591A power tubes, which run SMOKIN' HOT in with the stock 17v grid bias - heck power tubes used to only be a buck). The receiver really sounds great with the Cornwalls and will drive them to impressive sound pressure levels. Good first watt, too. Zero noise from my unit. No hiss either. Andy Quote Link to comment Share on other sites More sharing options...
eq_shadimar Posted October 13, 2001 Author Share Posted October 13, 2001 Andy - Again thanks for the input. I am very good at soldering and electronics work but I do not know my way around the older "analog" stuff. If you don't mind can I contact you after I have the unit and have you tell me what to replace with what etc...? Thanks, ------------------ FOR SALE OR TRADE COMPLETE R*3 SYSTEM FOR 3 HERESY'S Main System - Cornwalls (L/R main) RC-3 RS-3's (white) SVS 20-39CS Harman Kardon AVR 510 Hafler P505 (running sub) HT Room now X10 Controlled ProMedia 4.2 v400 for PC Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted October 13, 2001 Share Posted October 13, 2001 Yes EQ, But what you really need to do is get the back issue of Vacuum Tube Valley featuring the Fisher 500 (issue #6, winter 1997, available thru Antique Electronic Supply (602) 820-4643). They have a wiring diagram and basic instructions for a rebuild, including some pictures. What they don't tell you how to change the grid bias voltage to preserve those lovely 7591A's, so here it is: replace the 5.6K resistor located near the BIG ole brown bias cap inside the chassis (the only one that fits previous description) with about a 1.1K resistor to give -20.5 volts (you want -20 to -21 range + you can experiment with different resistors). Stock voltage is -17V which is info that will help verify your looking at the right resistor. By the way, the voltage is NEGATIVE voltage, so your meter leads will need to be reversed. Contact me privately if you need more details. Just for fun, I'll list the specs for the 500C amplifier section - read 'em and weep boys. Power: 32.5 WPC THD: .7% at 30W Intermoduation distoration: .7% at 30W Frequency response: 5 to 45,000 Hz, +0 and -2dB Hum and Noise: 80dB below rated output Channel Separation: 50dB Total variation of tone controls: 23dB AC power consumption at 1/3 power: 205W Andy This message has been edited by Klipschguy on 10-13-2001 at 04:47 PM Quote Link to comment Share on other sites More sharing options...
joemcten Posted October 13, 2001 Share Posted October 13, 2001 EQ, you should be happy with the sound of the Fisher on y9our Cornwall's. Up until recently I had a professionally rebuilt Fisher 100x integrated which I believe is a very similar amp circuit. It made wonderful music on my LaScala's. There is a great guy who rebuild's Fisher gear to incredible specs. His web site is www.2baudio.com He is excellent to deal with and know's the fisher gear inside and out. The new Electro Harmonix big bottle 7591 is outstanding. It is in current production and is modestly priced. Have fun. Joe Quote Link to comment Share on other sites More sharing options...
eq_shadimar Posted October 14, 2001 Author Share Posted October 14, 2001 Andy - Thanks that issue is on its way to me. I have access to all sorts of electronic parts suppliers so I am sure I can get the needed parts. Joe - Thanks for the link. He seems to be a Fisher fan for sure. It looks like I have lucked into a decent quality tube receiver. I understood everything he was takling about except for the following upgrades: TUBES A new matched quad of larger 7591A Electro-Harmonix output tubes are only $88. (fit 500-C & 800-C, not 400) 12AX7 & 12AT7 tube upgrades are only $10 each. There are 9 of them in each receiver! MODS & UPGRADES TONE/LOUDNESS BYPASS for unbelievable wide-open tone! Only $65 more Can anyone here decribe the pros/cons of these items. Again I am "tube" dumb so thanks for all the help!!! Laters, ------------------ FOR SALE OR TRADE COMPLETE R*3 SYSTEM FOR 3 HERESY'S Main System - Cornwalls (L/R main) RC-3 RS-3's (white) SVS 20-39CS Harman Kardon AVR 510 Hafler P505 (running sub) HT Room now X10 Controlled ProMedia 4.2 v400 for PC Quote Link to comment Share on other sites More sharing options...
eq_shadimar Posted October 14, 2001 Author Share Posted October 14, 2001 Another stupid question. I see that most of you have mentioned the 500c. The unit I am thinking about getting is a 500b. What is the difference? Thanks, ------------------ FOR SALE OR TRADE COMPLETE R*3 SYSTEM FOR 3 HERESY'S Main System - Cornwalls (L/R main) RC-3 RS-3's (white) SVS 20-39CS Harman Kardon AVR 510 Hafler P505 (running sub) HT Room now X10 Controlled ProMedia 4.2 v400 for PC Quote Link to comment Share on other sites More sharing options...
ShapeShifter Posted October 14, 2001 Share Posted October 14, 2001 eq, I'm not familar with the Fisher 500B/C, as I have the Fisher 800-B Stereo Multiplex Tube Receiver w/ 65 dual-channel watts. It's presently stored, but I plan to have it refurbished. It produced some really wonderful sounds from my Klipsch Heritage speakers. The link below takes you to a page with a schematic diagram for the 500B. Manuals can be bought on Ebay or directly from the Fisher Doctor. http://mcallister.simplenet.com/Fisher/500B/schemmpx.gif Fisher Doctor web site: http://fisherdoctor.com/ Should be a great sounding unit. Wes Quote Link to comment Share on other sites More sharing options...
joemcten Posted October 14, 2001 Share Posted October 14, 2001 Ed, the matched quad of larger 7591's are the output tubes and they are excellent. They are matched so there spec's are very close to one another. The 12at7's are of a new long plate variety that he claims offer wider control of the volume. They are a tube with less gain and he has found that they work and sound better. I also know that he replaces all major caps and increases there value significantly. He say's this is to allow the bass to have better low end response and control. I believe the 500b was just the previous generation. Just buy it and enjoy. Joe Quote Link to comment Share on other sites More sharing options...
ShapeShifter Posted October 14, 2001 Share Posted October 14, 2001 Some additional info: Fisher 500B Stereo FM multiplex receiver, 37 watts per channel. 7591 output tubes. Magic Eye tuning tube. Mint condition units usually sell for $400-500.00. Quote Link to comment Share on other sites More sharing options...
mobile homeless Posted October 14, 2001 Share Posted October 14, 2001 Go to see you are curious and interested in giving tubes a try. I have a good friend that has a Fisher X100 integrated that I thought made very good sound. There were several versions of this unit and later model has solid state rectified power supplies. I personaly believe that tube recitifation is a better way to go in this regard, as it offers a sweeter sound and appears to be more musical, especially in the vintage implementation (most modern SS quaility amps use HEXFREDs for their SS rectification - a much better source). All this being said, I thought the EICO HF-81 bested the Fisher amps I heard. It seemed to be more musical and open sounding, while retaining some serious growl, given the 14wpc. In addition, I would probably opt for an integrated amp without the tuner to keep the vintage piece simple. Tube tuners can be had very cheap... One more note that is very important to think about; I personally would try to shoot for an EL-84 output tube amps (or even the EL-34) over the the 7591. Frankly, there are not that many 7591 tubes out there. Your selection will be very limited. As for the EL-84, it is a GREAT tube and very nice sonics. There were a bevy of EL-84 amps, some with triode input stages that sounds quite nice. Good luck in your search. kh f>s> Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted October 14, 2001 Share Posted October 14, 2001 Basically, the 500B, when compared to the 500C, has the 7591A's mounted in front of the output transformers vs. behind, uses the excellent Golden Cascade FM front end vs. the Nuvistor front end, uses a tuning eye vs. a meter, also has a deeper champagne color in the face plate, and slightly different knobs. Also rated at 32.5 wpc RMS. One last thing, the diode rectification in the grid bias (Fisher 500) circuit produces the -17v DC for the grid and has nothing to do with the sound (it's just -17V DC that is acting like a valve to tell the tube how hard it should run in response to an input). Tube or diode rectification does not matter - it ONLY converts AC voltage into DC voltage - it's just plain old DC current, it is not in the "sound circuit" and it does not matter if comes from a tube, bridge rectifier or the cat next door. However, in the main power supply, the AC does need to be filtered to get the ubiquitous 60 cycle AC hum out of the line, whether it is from a tube or a diode. The more heavily filtered, the less the hum, however, the more it's filtered, the HARDER THE LOAD on the rectifier tube - you'll burn that baby up if you try to over filter the power supply. Note: filter caps are used to filter the power supply, if one is bad, your unit will hum - now you know where to look and how to fix it. Heavy duty silicon diode bridge rectifiers can easily take the heavy filtering and therefore can be used to produce less hum/noise, hence BETTER sound than a tube. Again, we're just talking about the noise floor, not some endowment of "warmth." The germanium diode in the Fisher grid bias circuit is subject to deterioration and should be replaced, in all Fisher 500 units, with a silicon bridge rectifier in conjuction with a 4.7 ohm 5W resistor (resistor needed, due to the slight increase in voltage that will occur with the silicon rectifier). If the germanium diode is deteriorating, you'll burn your power tubes up. Don't get me wrong, I LOVE tube rectification because of the nostalgic, purist in me (love that big ole tube rectifier glowing), but because of filter capacity, tube rectification is noisier, and is also much less reliable than a silcon bridge rectifier. Warm happy, just tryin' to help regards, Andy This message has been edited by Klipschguy on 10-14-2001 at 05:13 PM Quote Link to comment Share on other sites More sharing options...
mobile homeless Posted October 14, 2001 Share Posted October 14, 2001 I have to totally disagree with the preceding post. While the rectification may not be in the audio circuit per say, it DOES indeed make a difference in the way the amp sounds. Some of the benefits of solid state rectification is a supposed increase in bass solidity, but I have found this usually comes at the expense of a slightly more coarse sounding amp. Granted, HEXFREDs are a more linear and fast device and do a better job. However, tube rectification, once again, give TWO advantages to my ears. I have found that, on the whole, tube rectified power supplies DO lend a more relaxed presentation with the amp that a solid state rectified supply does not involve. Secondly, and far more easy to argue, is the fact that tube regulation usually lets the power tubes warm up very slowly unlike the blast of B+ from a SS rectified PS. Personally, I have amps from both camps, and I have ALWAYS preferred the tube rectified units for this relaxed presentation. Even though they are not directly in the signal, the rectifier choice DOES affect the sound. khf>s> ------------------ s y s t e m Linn LP-12/Linn Basic Plus/Sumiko Blue Point Rega Planet Cary Audio SLP-70 w/Phono Modified Creek OBH-12 Passive Welborne Labs 2A3 Moondog Monoblocks DIYCable Wire - Various ProAc Mini Towers Alternate System: EICO HF-81 ASUSA A-4 EL-34 UL EICO HFT-90 Tube FM Tuner Sumo Aurora Tuner Nakamichi CR-7af>s> Quote Link to comment Share on other sites More sharing options...
eq_shadimar Posted October 16, 2001 Author Share Posted October 16, 2001 Whew certainly lots of information her. I have purchased the unit and I expect to receive it sometime next week. Hopefully it will arrive in good condition. I will post to this thread after I receive it. I am sure I will have addtional questions then :-) Thanks, ------------------ Main System - Cornwalls (L/R Main) Heresys (L/R Surrounds) RC-3 SVS 20-39CS Harman Kardon AVR 510 Hafler P505 (running sub) HT Room now X10 Controlled ProMedia 4.2 v400 for PC Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted October 16, 2001 Share Posted October 16, 2001 I have to chime in with mobile homeless here. Klipschguy, the entire power supply is very much in the "soudn circuit", including the rectifier. It's not inaccurate to view the entire "downstream" section of the amplifier (gain, driver, output stages) as meerly "modulating" the output of the power supply in response to the chaning input signal. Rather than go into some long boring explination of why I feel that way, which I'd probably get wrong anyway, check out this link for some interesting thoughts on the matter... http://www.sasaudiolabs.com/theory7a.htm Ray ------------------ Music is art Audio is engineering Quote Link to comment Share on other sites More sharing options...
Chris Robinson Posted October 16, 2001 Share Posted October 16, 2001 Let us eschew obfuscation and pay homage to the importance of RBLs and PFM circuits, without which the preceding would be unnecessary. Ray, hope biz is picking up a bit and the stock price is back through the roof. Always enjoy your missives and interlocutions. Ciao bene. ------------------ If you don't like what is coming out, you wouldn't like what is going in." -PWK- --------------------- Klipsch 1968 ALK Cornwall "II"s (LF/RF) ALK Belle Klipsch (Center) Klipsch Heresy (RR/LR) Klipsch KSW-12 sub Sonic Frontiers Anthem AMP1 (driving Cornwalls) Sonic Frontiers Anthem AMP1 (driving Heresy's) Denon AVR-4800 Toshiba SD-3109 DVD Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted October 16, 2001 Share Posted October 16, 2001 Thanks for the input guys. I read the info on the web link, and while I stick by my position, I respect yours. The info was good, but remember the guy who wrote that info is pushing tube amps - so his bias (no pun intended) is apparent. Anyway, I've done some switching between tube and diode rectification in the past, and I can't hear the difference, but that doesn't mean you guys can't. You definitely need to let your own ears be the boss, as you know. Really, I've just been trying to help EQ get a good reliable 500B unit, so he can enjoy it for years to come. I also don't want him to think his unit is second class because it does not have tube rectification in the power supply. Like I said before, I do love tube rectification, but I also have a lot of respect for solid state rectification. Anyway, my sincere apologies if I offended anyone, and hope you all are well. Andy Quote Link to comment Share on other sites More sharing options...
Chris Robinson Posted October 16, 2001 Share Posted October 16, 2001 Andy, I don't think any offense was taken ... I think the counterpoint of the discussion revolved on perceptions, not emotions. In fact, all I was trying to do was inject a little levity into the discussion ... perhaps I was being too obtuse. Sorry. ------------------ If you don't like what is coming out, you wouldn't like what is going in." -PWK- --------------------- Klipsch 1968 ALK Cornwall "II"s (LF/RF) ALK Belle Klipsch (Center) Klipsch Heresy (RR/LR) Klipsch KSW-12 sub Sonic Frontiers Anthem AMP1 (driving Cornwalls) Sonic Frontiers Anthem AMP1 (driving Heresy's) Denon AVR-4800 Toshiba SD-3109 DVD Quote Link to comment Share on other sites More sharing options...
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