Question for the MASTERS here.

**Nipper** · December 18th, 2010, 06:04 PM

This is a question regarding vintage amps I have not seen addressed anywhere else. I could be looking for the topic incorrectly but I trust you guys.

If some of the gurus here (you know who you are) would share an opinion on this it would be greatly appreciated.

Older amplifiers did not have a polarized power plug. With this in mind... It is possible to plug it in upside down so to speak and have the hot and neutral switched. Would or could this have any effect on the amplifier?

If you can answer this please take a moment to explain why it would or wouldn't.

Thanks in advance!

**gvasale** · December 18th, 2010, 07:30 PM

The overwehlming majority of amplifiers discussed here all use power transformers which negate having a polarized plug. In the unusual case where one might have a 3 wire ac cord, this is for extra security. Better minds can offer additional details.

**Nipper** · December 19th, 2010, 05:01 PM

Hmmmmmm.
I dont know a lot about amplifier construction. I am just looking at this from an electrical point of view.

Newer amps that have transformers have a polarized plug. It could be a UL requirement now? Most everything that runs on 120v I buy now has one.

There are some really fanatic folks that would swear the "monster" speaker wires can make a difference. I personally never heard it. This might be a similar issue. It seems like someone who is that particular about their connections might have thought about this.

Most people here would agree that switching the speaker cables will cause them to operate out of phase. With that in mind it seems to me that the chassis of the amp should always be connected to the neutral especially since a lot of them have a ground lug.

If you had an older amp, would there be any benefit to installing a polarized plug?

**Steve Mac** · December 19th, 2010, 06:32 PM

It's for safety...there are many articles out there...this explains the basics:
WHY THREE PRONGS? Electrical ground, stray voltage

**bfish** · December 19th, 2010, 09:04 PM

(disclaimer: I claim Jack-of-all-Trades, MASTER of none status)

Everything after '48 at least had the option of polarized plugs, since all receptacles (in the US) made after that had to be polarized (NEMA 1). If there was advantage to polarization, they took it.

Things were a little different then too, we weren't so helpless as now... As kids, it was our job to unplug the TV and radio after use so lightning wouldn't get them. To reconnect, we had to look for the brass terminal and plug it into one (can't remember which) side of the outlet.

I'll bet there are at least a few here that can remember porcelain surface devices and in-the-room wiring on insulators... :mooning:

**gvasale** · December 19th, 2010, 09:09 PM

Going to the phasing question, Its an easy thing to check and noticable if the bass output seems weak or the imaging shifts as you move your head from side to side. Just replacing cables, without checking to see if the wires are done right will be 50-50 to be out of phase.

**Art J.** · December 20th, 2010, 10:07 AM

Originally Posted by bfish

(disclaimer: I claim Jack-of-all-Trades, MASTER of none status)

Everything after '48 at least had the option of polarized plugs, since all receptacles (in the US) made after that had to be polarized (NEMA 1). If there was advantage to polarization, they took it.

Things were a little different then too, we weren't so helpless as now... As kids, it was our job to unplug the TV and radio after use so lightning wouldn't get them. To reconnect, we had to look for the brass terminal and plug it into one (can't remember which) side of the outlet.

I'll bet there are at least a few here that can remember porcelain surface devices and in-the-room wiring on insulators... :mooning:

ROTF
Hey Fish, well I did get my E-1 Masters in Electrical during the time of the hot chassis.
It was great back then because it kept DIYers hands out of our stuff.
Things are a lot different now and todays answer to such questions would be Google it.

**Nipper** · December 20th, 2010, 11:30 AM

OK good people..... Not holding anyone to anything here.

I apologize if the "Master" thing made it uncomfortable for someone to answer. Everyones opinion is welcome.

Here is the reason for the question:

Phase Linear 700b (has the original non polarized 2 prong plug, no ground) had an almost inaudible buzzy sounding hum. After reconnecting and checking everything (all the regular anti-hum items) it still had the hum. I checked the outlet for correct wiring (good connection and polarity) as a last resort. Then the thought occurred to me about polarity with the amp.

So... I used the VOM to see which plug had continuity with the chassis. I flipped the plug and no hum. Flipped it back and hum.

So without moving this beast to a different outlet I thought someone might be able to tell me why.

Then I started wondering how the polarity could be reversed and not cause the speakers to be running out of phase.

Is phase only an issue if one of the two speakers are out of phase?

I remember some of the old Sansui amps had a speaker mode selector switch which included reverse, normal, mono, left, right. I distinctly remember the "reverse" function did not switch the left and right output so I am thinking it may have been for phase. I never gave that much thought back then and never used that setting. That amp also had a non polarized, 2 prong plug. Maybe someone at Sansui was on to this a while back?

Please note: This was an older home 60+ year old wiring so.......