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Author Topic: Protecting speakers from nutters  (Read 5604 times)

Sangram Rakshit

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Re: Protecting speakers from nutters-Payments?
« Reply #10 on: November 18, 2010, 12:54:57 am »

@Charlotte: Thanks - This would be fine on the input, but if Pin 1 is a floating cold pin would that not cause undesired operation?

I have a E-mu 1212m with a fully balanced output, and grounding the cold end really makes it sound terrible if the amplifier is unbalanced, so I run it with pin 1 floating instead.

@Ivan - we have certain 'political' reasons which compel us to continue working for this client. I agree with everything you've said and we've finally decided to pad the system down to the extent that will avoid damage even at the loudest volume, and tell the client that that is that. If they want more level, they need new speakers.
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John Roberts {JR}

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Re: Protecting speakers from nutters-Payments?
« Reply #11 on: November 18, 2010, 10:39:08 am »

Sangram Rakshit wrote on Wed, 17 November 2010 23:54

@Charlotte: Thanks - This would be fine on the input, but if Pin 1 is a floating cold pin would that not cause undesired operation?


Pin 1 is shield ground and should always be connected on properly designed gear.

Quote:


I have a E-mu 1212m with a fully balanced output, and grounding the cold end really makes it sound terrible if the amplifier is unbalanced, so I run it with pin 1 floating instead.


Hot= pin 2
Cold= pin 3
Shield=pin 1

Some poorly designed gear will have hum issues if stray shield/ground currents between chassis are allowed to corrupt the audio (bad internal design).

Some "balanced" outputs don't load sense the outputs,  so a dead short on pin 3 or pin 2 will cause distortion and lots of ground current that can cause crosstalk into other feeds.

So depending on the gear, to interface a (3 wire) balanced output to (2 wire) unbalanced input, the cold audio output line is either shorted to ground (pin 1) or left floating, which ever works best with the particular gear design.


Quote:


@Ivan - we have certain 'political' reasons which compel us to continue working for this client. I agree with everything you've said and we've finally decided to pad the system down to the extent that will avoid damage even at the loudest volume, and tell the client that that is that. If they want more level, they need new speakers.


JR

PS: I will apologize in advance for making this bad joke, but what country do customers from India get when they call customer service?  Laughing
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Sangram Rakshit

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Re: Protecting speakers from nutters-Payments?
« Reply #12 on: November 19, 2010, 12:40:20 am »

Quote:


Pin 1 is shield ground and should always be connected on properly designed gear.



Sorry I meant Pin 3.

Quote:

Some "balanced" outputs don't load sense the outputs,  so a dead short on pin 3 or pin 2 will cause distortion and lots of ground current that can cause crosstalk into other feeds.


Pretty much what I face, so I just float the ring terminal of the output TRS connector since all my downstream equipment tends to be RCA-input only.

Quote:

 what country do customers from India get when they call customer service?  Laughing


Thankfully, not the US or Britain! Laughing Laughing

Seriously though, I sympathise completely. The typical CS guy is not very fluent in English, and our language does not adequately support technical conversations. Education standards in the English language are not very good except in top-tier schools (which the masses cannot afford). It's a bit of a vicious cycle, though things have improved significantly in the last decade or so, at least from where I'm standing.

The real culprits are companies who shift the support base outside the comfort zone of their customers to lower their operating costs, instead of just making more reliable products and services. So don't blame us for everything! Smile
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John Roberts {JR}

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Re: Protecting speakers from nutters-Payments?
« Reply #13 on: November 19, 2010, 09:40:05 am »

Sangram Rakshit wrote on Thu, 18 November 2010 23:40



Quote:

 what country do customers from India get when they call customer service?  Laughing


Thankfully, not the US or Britain! Laughing Laughing

Seriously though, I sympathise completely. The typical CS guy is not very fluent in English, and our language does not adequately support technical conversations. Education standards in the English language are not very good except in top-tier schools (which the masses cannot afford). It's a bit of a vicious cycle, though things have improved significantly in the last decade or so, at least from where I'm standing.

The real culprits are companies who shift the support base outside the comfort zone of their customers to lower their operating costs, instead of just making more reliable products and services. So don't blame us for everything! Smile



Actually I find the language skills quite good, and I can understand them better than some of my neighbors in MS. It's a little passive-agressive game to make them repeat stuff over and over, and tell you their name is betty or billy, when you know it isn't.  Twisted Evil

I would much rather speak with a CS person in India with answers, than sit on hold for an hour or more.  My only bad experience was with a square problem that didn't fit into the round customer service holes available.  I had a DSL modem dropping out because of a telephone line problem. The phone company menu kept dumping me to India with folks telling me to unplug and reset my modem. I finally lied to get somebody from the telephone side to come out and fix where a squirrel was chewing on their wires. Its a sad day when you have to outsmart the customer service to get a good result.

JR





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Sangram Rakshit

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Re: Protecting speakers from nutters-Payments?
« Reply #14 on: November 30, 2010, 03:02:33 am »

Just to offer up an update on the status.

We have had this problem a few times before I ever started working with this company, so the service engineer in his infinite wisdom had already plugged in a 4.7 ohm resistor in series with the positive terminal before the signal even went to the speakers.

Unfortunately the resistor was only rated for 5 watts so it kept cooking and eventually burnt right out, all four at the same time so it's safe to assume there was a ton of power going into the system. The drivers were all safe.

We replaced all the resistors and turned the level control on the NAD preamplifier down to -12dB, plus we routed the signal through the highpass filter on the Velodyne subwoofer that was installed. Hopefully there is sufficient reduction in the power being dumped into the speakers, but it's wait and watch.
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