Fanvil PA2 buzzing noise and no sound on record out

[jk326598]

Hello,

We have an old phone system linked with an 1/8 inch stereo plug from the PBX to an amp that drives several shop speakers. The end is snipped and the bare cables are under the screw posts of the Clarity amp. It works fine. But of course I want to get rid of the old phones entirely.

I thought we could simply move the plug from the old PBX to the Fanvil PA2 and accomplish what we needed. When I do this there is no sound coming out of the speakers.

I tested the PA2 with a set of headphones and did get sound. So that is odd. The Fanvil is POE. Is it possible it needs more power to drive that signal?

Also, when I connect to the with the green SPK - and + (different wire) on Fanvil, I do get sound but a very loud buzzing sound when the the line is not engaged.

So I can have no sound, or an awful buzz.

I'm at a loss. Any suggestions would be greatly appreciated.

 

[cobaltit]

Such is the life when you don't go completely digital all the way. But firstly, if you are connecting to an amp, then no, you shouldn't need more 'power' since that's the amps job. Lookup to see what the PBX was outputting and see if the PA2 matches. You might also be able to bypass the amp and drive the speakers directly off the PA2, paying attention to the documentation to see if you do need more power.

 

[JohnS_3CX]

Hi,

You might need more power - take a look at this:
https://www.3cx.com/community/threads/fanvil-pa2-to-amplifier.80220/

 

[jk326598]

Hi,

You might need more power - take a look at this:
https://www.3cx.com/community/threads/fanvil-pa2-to-amplifier.80220/

The Fanvil is powered PoE. I tried plugging in a 12v ac adapter but the 1/8 still did not produce sound.

 

[jk326598]

Such is the life when you don't go completely digital all the way. But firstly, if you are connecting to an amp, then no, you shouldn't need more 'power' since that's the amps job. Lookup to see what the PBX was outputting and see if the PA2 matches. You might also be able to bypass the amp and drive the speakers directly off the PA2, paying attention to the documentation to see if you do need more power.

Sorry what do you mean "what the pbx was outputting"? As far as I can see it has a line out to 1/8 inch stereo connected to the amp in (Tel). Which is why I thought moving that to the Fanvil made sense.

 

[leejor]

The buzzing sound, when idle, may be because of a ground issue. It may be that the amp will have to be electrically isolated, from the input, with an impedance matching transformer.

 

[jk326598]

The buzzing sound, when idle, may be because of a ground issue. It may be that the amp will have to be electrically isolated, from the input with an impedance matching transformer.

That makes sense. We have a similar setup at another location and I believe there is a transformer there.

 

[leejor]

A very inexpensive 600 to 600 ohm matching transformer should work, but check to see if there are any specs on the input/output of the devices.

 

[jk326598]

A very inexpensive 600 to 600 ohm matching transformer should work, but check to see if there are any specs on the input/output of the devices.

The amp is the same at the other location. Also same fanvil. So in theory same transformer should work.

What is puzzling still is why the 1/8 inch out stereo on the Fanvil works to a headset but not through the amp.

 

[leejor]

Could it be that the ground, and the signal source leads, are reversed at some point?

 

[jk326598]

Could it be that the ground, and the signal source leads, are reversed at some point?

On the question of the 1/8 inch stereo plug? I don't think so. There is a cable from the old PBX to the AMP. I simply unplugged the 1/8 inch part and stuck it in the Fanvil expecting sound. Worst case I guess I could reverse the + and - at the amp ?

 

[leejor]

I'd be certain the the ground, is in fact ground, at both ends. Amps do have a tendency to hum, if inputs are left unterminated.

If you have another setup that works, when using a transformer, then I would just duplicate that.