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[Nathan Rooke]

I'm attempting to install a Yorkville CA1 Coliseum Amplifier but I'm having issues with it.
I'm connecting it as a 70v music system for a business. After the initial setup it began playing music fine but within about a minute I started to notice faint cracks and pops. These got steadily louder until the distortion in the audio was well beyond listenable. After attempting to diagnose it a bit I decided to remove my speakers and the input line from the unit to see what the response would be. Sure enough, after leaving the unit ON with all the dials turned to 0 and absolutely nothing plugged into it except the power cable I started to see blips on the "OUTPUT LEVEL" gauge. They steadily increase and I can even hear something in the unit making noise with the blips.

I've tried different outlets and have never had any power issues with this building so I don't think it's a power issue. And it's brand new right out of the box so I doubt it's broken. Any ideas?

I should probably mention the only thing I know about 70v audio systems is the online reading I've been doing over the last 3 weeks and have never set one up before now so try not to throw too many big words at me   

[Ivan Beaver]

I'm attempting to install a Yorkville CA1 Coliseum Amplifier but I'm having issues with it.
I'm connecting it as a 70v music system for a business. After the initial setup it began playing music fine but within about a minute I started to notice faint cracks and pops. These got steadily louder until the distortion in the audio was well beyond listenable. After attempting to diagnose it a bit I decided to remove my speakers and the input line from the unit to see what the response would be. Sure enough, after leaving the unit ON with all the dials turned to 0 and absolutely nothing plugged into it except the power cable I started to see blips on the "OUTPUT LEVEL" gauge. They steadily increase and I can even hear something in the unit making noise with the blips.

I've tried different outlets and have never had any power issues with this building so I don't think it's a power issue. And it's brand new right out of the box so I doubt it's broken. Any ideas?

I should probably mention the only thing I know about 70v audio systems is the online reading I've been doing over the last 3 weeks and have never set one up before now so try not to throw too many big words at me   

Sounds like the unit to me.  Just because it is new means almost nothing.  most electronics failures happen very early on (within the first couple of hours of usage) or quite late in life (years later).

Exactly what do you mean when you set the controls to "0".  I have not looked up the unit-but it could mean all the way down-all the way up-or somewhere else that is labeled 0.

It does not not sound like a power issue to me-I assume you have already MEASURED the voltage at the outlet-between hot and neutral and ground.  That would be FIRST easy start.

Have you MEASURED the impedance of the speaker line attached to the amp?  That would be a SECOND step.  And I mean an IMPEDANCE SWEEP-NOT a single freq measurement.

Trouble shooting is NOT a guessing game.  It is a PROCESS that involves measuring-then taking the results of those measurements and figuring out  a next logical step.  Divide and conquer.

As it seems right now-you don't know that ANY part of the system is correct (power-amp-speakers).

As with any profession-you need to proper tools to do it right.

Sorry to sound hard but you do need to know what you are doing-especially if somebody is paying you.

By your description-it sounds like it is the amplifier.

I already assume you have swapped it out with a different unit to help narrow down the problem?

[Brad Weber]

I agree with Ivan that it sounds like the mixer/amp is bad and also that before replacing it you might want to verify that there is nothing with the rest of the system or the installation that might have contributed to any failure.  Things like the impedance of the speaker line(s) and how you have everything wired at the speakers and to the mixer/amp.  It also appears that the nominal power rating of the CA1 is 60W so you may want to verify that the total of the connected speaker tap ratings is less than 60W (with some accommodation for line losses).

[John Roberts {JR}]

That symptom does not sound typical of any common fault.

Is amp running hot?

Troubleshooting divide and conquer, so disconnect wiring from amp and attach one different small speaker directly to amp. If that works, issue is speaker or wiring. If it still screws up it is the amp.

JR

[Nathan Rooke]

Sounds like the unit to me.  Just because it is new means almost nothing.  most electronics failures happen very early on (within the first couple of hours of usage) or quite late in life (years later).

Exactly what do you mean when you set the controls to "0".  I have not looked up the unit-but it could mean all the way down-all the way up-or somewhere else that is labeled 0.

It does not not sound like a power issue to me-I assume you have already MEASURED the voltage at the outlet-between hot and neutral and ground.  That would be FIRST easy start.

Have you MEASURED the impedance of the speaker line attached to the amp?  That would be a SECOND step.  And I mean an IMPEDANCE SWEEP-NOT a single freq measurement.

Trouble shooting is NOT a guessing game.  It is a PROCESS that involves measuring-then taking the results of those measurements and figuring out  a next logical step.  Divide and conquer.

As it seems right now-you don't know that ANY part of the system is correct (power-amp-speakers).

As with any profession-you need to proper tools to do it right.

Sorry to sound hard but you do need to know what you are doing-especially if somebody is paying you.

By your description-it sounds like it is the amplifier.

I already assume you have swapped it out with a different unit to help narrow down the problem?

Hi Ivan,

Thanks for the indepth reply. I'll try and hit these question by question.

By control to "0" I mean everything all the way down/off (except the power toggle of course).

I have not measured the voltage at the outlet but it's a standard outlet in a new building with no issues with the plug as of yet and I've tried a couple different outlets.

I measure the impedance in the line only with a multimeter so far. However I made sure the impedance was far above the minimum safe load. Also the issue exists with all speakers disconnected and the outputs on the unit turned off so I assume it can be them.

I don't have experience with 70v systems other than what I've been reading in online guides for the past few weeks and would LOVE if they brought in a guy for this to at least train me but according to the powers-that-be it's not in the budget. So it looks like I'm flying solo on this one.

I haven't swapped it out with another unit yet since we don't have any other units to swap it out yet and I wanted to make sure this one was bad and I wasn't making a classic 70v newbie mistake.

And just so I am clear; there should be no issue with having a 70v unit powered on with nothing connected to it so long as everything is set all the way down, correct?

---
The amp is not running hot and I have tested it with a single speaker as well as hooking up an 8ohm speaker to the 8ohm port and had the exact same results.

[Ivan Beaver]

I have not measured the voltage at the outlet but it's a standard outlet in a new building with no issues with the plug as of yet and I've tried a couple different outlets.

I measure the impedance in the line only with a multimeter so far. However I made sure the impedance was far above the minimum safe load. Also the issue exists with all speakers disconnected and the outputs on the unit turned off so I assume it can be them.

I run into situations all the time in which there is something 'wrong" with outlets.  A quick measurement (between ALL legs) will confirm if is "probably" OK,  I say probably-because this does not test for loose connections.

How did you measure the impedance with a multi meter?  All you could measure would be the DC resistance of the transformer windings and the connecting wiring.

I BET this reading was much lower than the rating of what the impedance would be.

An easy to remember " basis" for 70V is as follows.  Always remember that the impedance of a 1 watt tap on 70V is 5000 ohms.

So 10 watts would be 1/1oth that or 500 ohms.  100 watts would be 1/100th or 50 ohms.  You can easily guess (close enough anyway) at wattages/impedances in between those numbers.

Another fact to remember is that 600 watts= (or close enough) 70V @ 8 ohms.

So you can use a 600 watt amp @8 ohms to drive a 70V line directly-WITHOUT a transformer.

[Tim Perry]

A amp is not running hot and I have tested it with a single speaker as well as hooking up an 8ohm speaker to the 8ohm port and had the exact same results.

Possible crosstalk from the radio?

[Chris Clark]

Swap it for a different amplifier, If you're seeing these "pops" on the meters with no input signal and the input attenuators all the way down, I'm leaning towards something on the output stage, perhaps a faulty transistor. (Remember that 99% of the volume controls on amplifiers control the signal going to the output stages, not the signal going to the speaker directly)

If you really want to make sure its the amp and not something power related (which I'm betting its not) take the amp somewhere else (out of the building, completely different location) and see if you see the same pops on the meters...

[Nathan Rooke]

I run into situations all the time in which there is something 'wrong" with outlets.  A quick measurement (between ALL legs) will confirm if is "probably" OK,  I say probably-because this does not test for loose connections.

How did you measure the impedance with a multi meter?  All you could measure would be the DC resistance of the transformer windings and the connecting wiring.

I BET this reading was much lower than the rating of what the impedance would be.

An easy to remember " basis" for 70V is as follows.  Always remember that the impedance of a 1 watt tap on 70V is 5000 ohms.

So 10 watts would be 1/1oth that or 500 ohms.  100 watts would be 1/100th or 50 ohms.  You can easily guess (close enough anyway) at wattages/impedances in between those numbers.

Another fact to remember is that 600 watts= (or close enough) 70V @ 8 ohms.

So you can use a 600 watt amp @8 ohms to drive a 70V line directly-WITHOUT a transformer.

I measured the outlets I used. Got Hot/neutral 121.8V, Hot/ground 121.5V, and neutral/ground 0V. Same results minus about half a volt for the other socket so the outlets are probably okay.

I cant imagine I'll be hitting too many issues with impedance, I'm only planning on powering about 11 speakers at a few watts each.

Do you have any recommendations for an inexpensive speaker impedance tester?

I think I'll just take your word for it on powering an 8ohm speaker on a 70v line

And thank you again for your help.

[John Roberts {JR}]

Since you added an emoticon I hope you are kidding, but putting a typical install 8 ohm speaker on the 70v tap, will hit it very hard.

This is not the same thing as driving a 70V line with a 600W 8 ohm amp.
 
JR

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