Can anyone tell me what the "Phase Reverse" switch is for on the 500B ?

I did some research and a search on the AK forum but I didn't come up with anything definitive.

I'm asking only because my newly acquired 500B has undergone a complete re-build, but there seems to be an issue with this switch. The person whom I have entrusted the re-build tells me that the switch has to be replaced. I trust him to do what is needed. He rebuilt my 500C (which after the rebuild ROCKS).

So, what does this Phase Reverse switch do, and how is it detrimental to the unit itself?

Sometimes, in the early days of stereo, records were mixed and/or mastered out of phase. Several Nat King Cole stereo Capitol albums have Nat's vocal out of phase (instead of coming from the phantom center, it seems to come from all around you like a fake "surround" deal).

By flipping the switch you can reverse that problem for that album only.

The switch is also useful to make sure your speakers are wired correctly. Play a mono source. In correct mode the sound should seem to come from directly in between the two speakers. With the phase switch activated, the mono sound once again comes from all around no, no defined center space.

Hope this helps. Others here I'm sure will elaborate.

If you want to keep your unit stock, fix the switch. If you don't care, bypass it.

Dang- and all this time I thought it was for people too lazy to flip the connections for one of the speakers when they realized they connected them wrong. lol! Did you notice the "Stereo Reverse" switch too? That also harkens back to the early days of stereo recordings/broadcasts in which L-R transpositions would occur.

The Phase Reverse switch basically switches the polarity of your speakers. "Off" is negative ground. Flipping the switch reverses your positive and negative speaker leads, more or less as a test that your speakers are wired "in phase". According to the manual, once the speakers are properly set, you shouldn't have to touch it again. That's why it's on the back on the 500B.

The Channel Reverse switch sends the output of the left speaker to the right and right to left. Early stereo broadcasting was sometimes mixed up so flipping this switch put the instruments and vocals back where they belong.

The switches themselves are physically the same and I've had to take a couple of them apart. Sometimes, the sliding contacts in the switch get weak and won't make contact anymore. I even brazed one that was slightly broken.

As for the Phase Inverter: How do you have the right speaker connected--using the "Impedance Selector" wire from the switch or is it bypassed/disconnected?

Check the library here. The Owner's Manual is posted: http://akdatabase.com/AKview/albums/userpics/10004/Fisher 500B Owners Manual.pdf

Thanks for the replies everyone.

@walyfd: thanks for the manual link.

walyfd said:

The Phase Reverse switch basically switches the polarity of your speakers. "Off" is negative ground. Flipping the switch reverses your positive and negative speaker leads, more or less as a test that your speakers are wired "in phase". According to the manual, once the speakers are properly set, you shouldn't have to touch it again. That's why it's on the back on the 500B..

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I'm sorry, I don't want to argue with you but the switch only reverses ONE set of speaker leads, throwing the sound "out of phase". Nothing to do with absolute polarity, an issue that wasn't even really discovered, talked about or worried about until the 1980's...

walyfd said:

According to the manual, once the speakers are properly set, you shouldn't have to touch it again. That's why it's on the back on the 500B.

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Funny, on the 800B I had, the Phase Reverse switch was located on the front panel. :scratch2:

Steve Hoffman said:

I'm sorry, I don't want to argue with you but the switch only reverses ONE set of speaker leads, throwing the sound "out of phase".

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Agreed. Otherwise the whole point of the switch would be defeated.

People used this option to gain watts, my understanding is you can gain 3-5 watts by switching the phase.

Not true. Take the speaker wires on your rig. Reverse one side. If everything was in phase (speaker wise ) beforehand, now the speakers will be out of phase, one pumping toward you and the other away from you on the same note. It'll sound muddy, and unclear. Now put the speaker wires back to the original way you had them. With both speakers pumping forward or backward at the same time, sound is clearer, and more diefined. There is no loss or gain in watts by doing this. Just muddy or clear sound. Put a scope on the amp while doing this and you'll see no increase or decrease in wattage.

I'm relatively new to the Fisher Family so the way I interpreted the manual was by polarity. My bad, I suppose.

The guy who did the work on my set cut the lead from the Phase Inverter switch and said it wasn't necessary, thereby rendering the switch dead. What he didn't do was say that the process of connecting the speakers without that lead would differ from what's in the manual.

walyfd; Don't confuse the "PHASE REVERSE" switch with the "PHASE INVERTER" pots. Two separate and different items. Phase reverse switches the phase to ONE Speaker. Phase inverter changes the phase of one 1/2 of the signal to the outputs so they can be a PUSH-PULL combination. Think of a sine wave. Above the center line is pull and below is push. You use the phase inverter to change the phase of 1/2 of the signal to accomplish this. And to set it correctly needs a scope and a IM Distortion meter.

You interpreted the manual correctly if you are referring to ultimate speaker polarity. Actually a lot of the better early stereo amps and receivers had this feature, not just FISHER. It only works on one speaker. You can do this manually on ANY AMP/RECEIVER. They later dropped it when the manufacturers came out with or realized 1) it was too confusing to most consumers, 2) Color coded or Polarity Marked connections worked just as well if not better PIONEER went so far as to come out with Polarized speaker connectors (basically a plug into the unit, that you screwed the wires to. It was and still is a PITA). If you set up your speakers the same way everytime (I use the striped speaker wire as ground or NEG to both the speaker and amp) on both sides you really don't need the phase reverse switch. But in the interest of historical accuracy, have the tech reconnect it. He works for you, and should have totally explained the role it plays and let YOU make the decision as to take it out or keep it in. If it were mine and it was functioning in the 1st place, I'd be raising all kinds of hell. NOTE: There are test records that actually test for speaker phasing. The switch makes it nice to change back and forth without having to power down and back up to make the change. I'll scan the section of the instructions for mine and post it up later for an example of what to listen for.

Fisher made the Receivers/amps from 1958-59 to 1963 absolutely too complicated on the back for the average consumer. But the "high-brow crowd" were calling for complete control of the unit. I have a X-202 here I'm doing some work on for NAPTOWN. It's got something like 20 screw connections on the back, mainly having to do with the speakers in one way or another. I have to look at the manual EVERYTIME just to connect speakers to it when I test it. My 800C on the other hand is intuitive to a 5 year old.

Larry

So I was kinda right... So the switch only affects one speaker--which one?

As I understood it, it was fairly easy to mix up the speaker leads and this Reversed them or "corrected" one's mistake.

BTW: I reconnected the Phase Reverse wire myself. I wasn't asked ahead of time whether I wanted to keep it or not.

Good help is hard to find!!!

I have a X202B Amp and was confused as well..called the guy that restored it and he said the switch was to give more headroom to one speaker...it works fine so I hooked it up as per manual and it sound great. I never have hit the reverse switch. Its idol at present, went back to my 800C for awhile..

May I ask a question about the phase reverse switch...I have the 500B and I have more fullness and bass when the phase reverse switch is in the on position. The manual says,If this happens to switch the left speaker wires around and move the switch to off. I have check all speaker wire connections at both ends and have them correct positive to positive... negative to negative. Why is this happening. Is it OK to keep the wires in the correct position and keep the switch in the on position? Here is a pic of my receiver connections. I think there right.

Connections look right. Hopefully, you are using 16 ohm speakers. Most speakers are 8 ohm but 16's aren't unheard of.

I THINK you can just disconnect the Imp Sel wire from the 16 ohm junction and just move the positive wire to the 16 ohm spot. That should bypass the switch.

Yes my speaker are 16 ohm JBL Apollos. Is it OK to leave the speakers connected positive to positive and negative to negative and the phase switch in the on position? That is opposite of what the manual says. Just trying to figure out why my speakers according to the manual are out of phase.

2string1 said:

Yes my speaker are 16 ohm JBL Apollos. Is it OK to leave the speakers connected positive to positive and negative to negative and the phase switch in the on position? That is opposite of what the manual says. Just trying to figure out why my speakers according to the manual are out of phase.

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When speakers are connected out of phase, it will result in "muddy" bass as opposed to "tight". This is often perceived as "more" bass than what would be heard otherwise. But your stereo imaging will be severely compromised. The music will have a diffuse and directionless quality rather than having the proper placement of the instrumental ensemble. For the best fidelity, the phase reverse switch should not be used unless the recording is out of phase. (Assuming the amp-speakers connections are correct)

With the wire coming from the switch disconnected from the 16 ohm speaker screw, you have to connect your right speaker like the left one is connected--speaker ground to ground and pos to 16 ohm. Once that wire is out of the equation, on or off, the Phase switch should have no bearing on what you hear.

Do what provides the best overall sound. Have you tried swapping your left leads with the right to see if ONE speaker is more affected?

62caddy said:

When speakers are connected out of phase, it will result in "muddy" bass as opposed to "tight". This is often perceived as "more" bass than what would be heard otherwise. But your stereo imaging will be severely compromised. The music will have a diffuse and directionless quality rather than having the proper placement of the instrumental ensemble. For the best fidelity, the phase reverse switch should not be used unless the recording is out of phase. (Assuming the amp-speakers connections are correct)

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Now that you said that,I totally get it. I can't believe my system has been out of phase all this time. More bass is not what to listen for,like explained in the manual. I mistakenly took muddy as being more fuller and in phase but was totally trick by the manual. There must be an absolute test for phasing other then listening? I really can't tell by watching the speakers in and out movement because they don't move. Maybe I need to play some Hip Hop lol

2string1 said:

Now that you said that,I totally get it. I can't believe my system has been out of phase all this time. More bass is not what to listen for,like explained in the manual.

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If it's any consolation, after switching to mono to help make a weak FM station listenable, it was a few days before I realized I forgot to switch back to stereo. :stupid: lol