I must have been day dreaming and reversed the amp and speaker sides on a VC.

It played like major crap for about a minute before I turned it off. I pulled the VC, fixed my problem and fired it back up. I thought I could still hear a problem with the speakers so I moved the wires at the 1230 amp to another pair. Luckily I only needed 5 out of the 6 pairs (although I was going to bridge the outdoor pair...) This time when I fired it back up everything sounded fine.

My question is, what exactly happens when the VC is wired up backwards? Does it mess up the speakers? The amp? Based on my un-planned experiment, it looks like the amp got messed up, but maybe it was just overheated and would have recovered?

I am kinda surprised I have never done this before now....

Wiring an IM VC backwards can create a majorly funky load to the amplifier that will vary with the position of the knob. You'll typically find that it will work fine when the VC is full up, but shut down the amp as you back down the VC.

I've seen amps shut down and in many cases blow up from reversed VCs.

I once wired a VC backwards... It sounded a little "pinched" in that room, but I just assumed bad room acoustics... I left the system on overnight, so that when the builder walked in the next morning, he would be so impressed with the fact that I finished ahead of schedule!!!
Well, the next morning I get this panicked screaming phone call..."Hey get out here ASAP!!! There is a BIG problem out here"!!! I get there, (2.5 million dollar house), open the front door and was almost overcome with that really funky burnt electrical odor...The music was still on, but smoke was coming out of the top of the receiver... The top cover of the receiver was so hot, the paint was bubbling up, and thick white smoke was everywhere (from the amp)! Maybe an hour or two later, could have burst into flames... I was amazed the amp didn't go into thermal protection, or shut down... but there it was (a Pioneer), jamming away, but glowing hot!!! Ever since that experience... it triple check before sticking the VC into the wall!!! I was SO damn lucky...

I believe it creates avery low load when reversed. I always turn VC al the way down and check with an ohm meter before connecting. If using a speaker selector just connect everything as normal and plug the meter leads into the input. You can check individually and all on. Worth the extra 2 minutes time.

i have a great idea... dont use v/c's sell them a cheap multi room multi zone instead

ed

ALL transformer-type VCs are a dead short when wired in reverse and turned all the way down. What you think would draw the least current will torch your amp if you are unlucky. The only impedance then is offered by the speaker wire to the VC. If you did things right, this will be really thick, really low resistance, and you will have SUCH a problem!

After wiring VCs, check how they operate. Even at low volume, a reverse-wired VC raiss and lowers volume differently from the others, and if you go from room to room running them through all their volume steps, you will hear this difference (at least you will after you do one backwards). If the amp is underpowered, lowering the backwards VC will cause the volume to sag at the other speakers.

Wow, I guess I got lucky and it could have been a lot worse.

ed, I do try to always sell a multi-zone system but sometimes it is just not in the budget. At least I use the vc's with dedicated channel amps.

Thanks for the comments guys.

The only time we use volume controls is for the bedroom/bathroom zone smaller (2-5k sq ft) houses. This way they can listen in the shower while the significant other is still sleeping, etc. Basically we use volume controls for subzones only.

Like someone else said, you can typically sell some type of multizone system.

Keep in mind that auto-transformer VC's not only present a low impedance load to the amp, they also step up the voltage to the speaker. The lower the setting, the greater the step-up ratio.

I have a better idea. "HIRE A PRO".
Seriously, in this day and age, why waste your time selling VC's with no form of control?????

.25 cents please

ed

my .25 cents please.

i could not agree more.....

i cant be an asshole everyday, i'm triing to be more nice and even understanding......

I walked into to a job ,that some other gentleman wired, to troubleshoot a problem with one of the customers rooms. When I got there and checked out the room with a volume control I noticed the volume was really low and for some reason the volume control was singing to me. I checked the wiring and it was reversed so I fixed it. From there out everything was fine. It was the funniest thing though to hear the music coming out of the electronics in the volume control.
jc

Ernie, aren't they nearly a DC short either way? Transformers are transformers, after all?

What are typical readings on either side of an impedance matching VC compared to a typical non-matching transformer type?

Larry,
they step UP the impedance shown to the amp by any particular speaker. This allows several of them to be put in parallel. In so doing they step DOWN the volume. The only way a volume control could step up the voltage to a speaker would be for it to put out more power than goes into it because the speaker is the same impedance either way, and more volume would equate to more power. Another way to look at it is that the volume control steps down the power to each speaker so that all speakers share the available power.


The full down position of a volume control is likely to be a short circuit on the speaker end just because it's easy to make that way, and that will keep speakers from vibrating sympathetically. The next to full down position on the input will be a high impedance; the full down can be either an open circuit so no power goes to the speaker or some other arrangement so that the speaker gets no power. I have read continuity with a Testum phone signal generator, but haven't bothered to read actual ohms, with some VCs at zero volume, and have found some are open circuits and some aren't.


Sorry, I haven't read these. When I am troubleshooting this stuff, I usually use a dumb continuity tester or a VOM. The VOM reading will be way off of the impedance because it is reading DC resistance, and the coil dynamics don't add in. You can compare readings from one VC to another and feel your way around without knowing the actual AC impedance at any frequency.