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Topic:
Auto switching an amp from Zone 2 to surround speakers
This thread has 19 replies. Displaying posts 1 through 15.
Post 1 made on Friday December 16, 2016 at 21:41
Craig Aguiar-Winter
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I have a client with a very large garage. One side of it has a man cave run through a Marantz preamp, amplifier combo. It has the TV etc. That system has a five channel amplifier. Currently only two channels of it are being used. We may put a centre channel on it later. The other two channels were to be used for future rear speakers obviously. We were going to add a small two channel amplifier for two outdoor speakers in zone three that don't need a lot of power. Zone two is about to be set up with two big JBL pro audio speakers running off of a crown CDI 2000 and an 18" woofer run off of an XLS 2502. This will be to provide loud sound for the garage versus the quieter but really high-quality that the current system has.

The two JBL speakers, while about 30 feet behind the listening area, are in a good place to act as rear speakers. I had a thought that I could run the pre-out from the rear speakers and the pre out from zone two into a switcher that would be triggered by one of the 12 V triggers on the Pre-amp. The amplifier would default to the rear pre out but when zone two is activated switch to the zone two per-out.

There is no good place in the listening area for the rear speakers to go. This solves that issue, and this way I could re-purposed two of the channels on the five channel amp to power the outdoor speakers. The power output to the JBL speakers is way overkill for rear speakers of course but the level would be dictated by the settings for the rears in the preamp. Just because they can be offensively loud doesn't mean they have to be.

In my opinion it's no different than using something like a Niles Amp with an auto switching input. Just on a larger scale.

What are your thoughts? Any input is appreciated.

Thanks, Craig.

Last edited by Craig Aguiar-Winter on December 16, 2016 23:59.
My wife says I can't do sarcasm. She says I just sound like an a$$hole.
Post 2 made on Saturday December 17, 2016 at 00:02
Ernie Gilman
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I did this, more or less, some ten years ago. It was speaker level switching, and I switched mains and surrounds to Zone 2. But here's how I'd do it today:

You say you have a pre/pro, so I assume you have left and right front, and left and right surround, preamp outputs, among other things.

The Niles AVS-2 ([Link: nilesaudio.com]) lets you switch between line level signals using your trigger.

I'd get two line level switches and set up the audio so that mains and surrounds are either on the main zone or are on Zone 2. You just have to Y out the Zone 2 audio into the switch. Remember you can easily and simply Y a signal to feed two inputs; the thing that's difficult is Y-ing together two signals.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 3 made on Saturday December 17, 2016 at 06:39
thecapnredfish
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Agree with Mr. Gilman. But, maybe because its so early. I dont get the part about needing 2 switchers. Oh, verify the preamp can provide enough current for the old school switcher. Many modern rec or prepros need another relay switching an alternate power source for the switcher trigger. The Niles requires 100mA. A current Marantz prepro provides 150mA. not even enough for a universal auto type relay you find at an auto parts store. Mousser electronics has a good selection.
OP | Post 4 made on Saturday December 17, 2016 at 08:24
Craig Aguiar-Winter
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Thanks for the input guys. If needed, I can wire up a relay and a wall wart no problem.

That looks like it would do the trick, but I also am unsure of why I would need the second switcher.

Maybe I'm thinking too simply but why can't I just get a project box, screw some RCA connectors on the outside and wire up two solid state DPDT relays inside. I have all of the parts minus the project box.

Am I over simplifying it?

Thanks

Craig.
My wife says I can't do sarcasm. She says I just sound like an a$$hole.
Post 5 made on Saturday December 17, 2016 at 08:31
thecapnredfish
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No reason you cant make your own. I just had a boat trim tab control box have a relay fail. Found exact one for a dollar seventy but have to buy 50 dollars worth. So I took four SPDT auto relays wired up for voltage reversal, port and starboard bow up/down. 20 bucks. New relay box was 140.
Post 6 made on Saturday December 17, 2016 at 10:42
ceied
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ada makes such a device.
Ed will be known as the Tiger Woods of the integration business, followed closely with the renaming of his company to "Hotties A/V". The tag line will be "We like big racks and tight holes"...
Post 7 made on Saturday December 17, 2016 at 12:34
buzz
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On December 17, 2016 at 08:24, Craig Aguiar-Winter said...
and wire up two solid state DPDT relays inside. I have all of the parts minus the project box.

I'm not sure what you mean by "solid state" relay. If you mean a relay without any mechanical contacts, this is a bad idea for audio because there is a little "glitch" as the signal passes through zero. This is not an issue for most lamps and motors, but it will tear up the audio.
Post 8 made on Saturday December 17, 2016 at 12:43
Ernie Gilman
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Why two switchers?
On December 17, 2016 at 00:02, Ernie Gilman said...
I did this, more or less, some ten years ago. It was speaker level switching, and I switched mains and surrounds to Zone 2.

I was describing a setup where you'd switch front and rear speakers to Zone 2. That's four channels from the surround preamp, so, two switchers.

On December 17, 2016 at 08:31, thecapnredfish said...
No reason you cant make your own. I just had a boat trim tab control box have a relay fail. Found exact one for a dollar seventy but have to buy 50 dollars worth. So I took four SPDT auto relays wired up for voltage reversal, port and starboard bow up/down. 20 bucks. New relay box was 140.

Admittedly, if this is your boat, you're not going to charge yourself labor, but what was the value of the time you put into sourcing, buying, designing, and constructing this replacement? Now that it's done, does it look good enough to be on a client's boat? Is it in an enclosure to ensure that it stays dry?

Little projects like this are nothing when we do them for ourselves but have huge other dimensions when we install them for clients.

If you didn't use Bosch automotive relays, be aware that they are usually easy to get and can be used for stuff like this, but they require more coil current than I'd expect A/V trigger outputs to supply. (I once ran across a Marantz projector that outputted about 5 mA at twelve volts. Had to build an amplifier for it!)
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
OP | Post 9 made on Saturday December 17, 2016 at 12:43
Craig Aguiar-Winter
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On December 17, 2016 at 12:34, buzz said...
I'm not sure what you mean by "solid state" relay. If you mean a relay without any mechanical contacts, this is a bad idea for audio because there is a little "glitch" as the signal passes through zero. This is not an issue for most lamps and motors, but it will tear up the audio.

That is what I meant. Is there a simple solution. To that? Or is that solution to buy the Niles or similar device?

Could I use a regular relay with mechanical contacts? I have one that I bought a while ago to try this out on my own system which has enough contacts to handle all of the connections.

Craig.

Last edited by Craig Aguiar-Winter on December 17, 2016 12:56.
My wife says I can't do sarcasm. She says I just sound like an a$$hole.
OP | Post 10 made on Saturday December 17, 2016 at 13:27
Craig Aguiar-Winter
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On December 17, 2016 at 06:39, thecapnredfish said...
Agree with Mr. Gilman. But, maybe because its so early. I dont get the part about needing 2 switchers. Oh, verify the preamp can provide enough current for the old school switcher. Many modern rec or prepros need another relay switching an alternate power source for the switcher trigger. The Niles requires 100mA. A current Marantz prepro provides 150mA. not even enough for a universal auto type relay you find at an auto parts store. Mousser electronics has a good selection.

So it appears that since the Marantz can provide up to 150mA we should be good?

Craig
My wife says I can't do sarcasm. She says I just sound like an a$$hole.
Post 11 made on Saturday December 17, 2016 at 14:29
buzz
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Craig Aguiar-Winter,

Solid state relays behave similarly to back to back to back (in parallel, but anode of one diode connected to the cathode of the other) diodes connected in series with the speaker wires. You can try this with a pair of 1N4004's or similar. There is a forward voltage drop associated with each diode and from about -0.6 to +0.6 Volts, neither diode will conduct. This is not a big deal for a 120V lamp, but audio will be sliced up.

A mechanical relay will have a small resistance. If you want to get fussy, the surface contamination on the relay contacts might form some low grade diodes and muck with the sound, but these "diodes" break down at very low voltage and the actual voltage drop is usually very low compared to the audio. As the contacts age, this contamination can build to the point where it may cause audible trouble -- requiring contact cleaning or replacement of the relay. In case you are wondering, gold plating the relay contacts is not a long term solution for speaker relays because the small arc that is generated when switching under load will quickly blow away all of the gold. On the bright side you can exploit this arc to burn away surface contamination by repeatedly opening the relay while the amplifier is operating at full power and driving a speaker.

For super high quality audio I prefer that the speaker "protection" relay be omitted, but this is a much more complicated amplifier design project because the little clicks and pops normally created while an amplifier starts up or shuts down are directly sent to the speakers and can be beyond annoying. (Think of a little 200W "click"). And, if an output transistor shorts, the speakers are at risk.
OP | Post 12 made on Saturday December 17, 2016 at 15:25
Craig Aguiar-Winter
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Thanks very much for such a detailed response. I believe I understand that yes I can use a regular relay, just be prepared for it to wear out over time? I should put a diode across the coil as well correct?

I found a great deal on one of those Niles AVS2. I'm leaning that direction but I'm still very interested.

Thanks again.
My wife says I can't do sarcasm. She says I just sound like an a$$hole.
Post 13 made on Saturday December 17, 2016 at 16:10
buzz
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Yes, a "freewheeling diode" across a DC relay coil will manage the inductive kickback created as the relay coil current is interrupted. This will protect mechanical and semiconductor switches.
Post 14 made on Saturday December 17, 2016 at 18:39
Ernie Gilman
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EVERY relay powered by DC should have a diode across it, connected such that it does not conduct the electricity sent to close the relay. When the relay is turned off, the collapse of the magnetic field of the relay coil creates a voltage spike that can sound like a click in your audio. I use a 1N4003 or 1N914 for this.

Yes, if you have four relays, each relay should have its own diode. There's no point in having a diode across a relay ten inches of wire from a relay that' creating a spike. Short it out at the relay, not at the adjacent relay.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
OP | Post 15 made on Saturday December 17, 2016 at 19:02
Craig Aguiar-Winter
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I have one relay. 12v coil. 4 poles. Double throw. Just need one diode. Thanks again for all of that detail.

I'll rig up the relay and try it on my own system to see the result as far as pops and such. If it's good I'll use it and if not I'll grab the Niles piece.

Craig
My wife says I can't do sarcasm. She says I just sound like an a$$hole.
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