Let me start off by apologizing since this is not concerning a guitar amp.
What I'm trying to do is find the correct potentiometer resistance to control a signal coming from the speakerphone port on a Cisco IP phone. I'm building a device for work to power some intercom speakers but the level coming out of the phone (~2-4 watts I'd guess) is overloading the "MIC" inputs on my bogen amplifier. Once I turn the volume on the phone down, it works fine--no clipping. The only problem with that is the intercom software turns the volume back up on the phone to maximum; there is no way around this.
Here is the information I know:
The speakerphone output on the phone:
The amplifier I'm plugging connecting the speakerphone leads to:
My proposed plan was to wire:
My questions:
Here's a semi-crappy phone picture of the project.
Let me know if you need anything else and a big THANK YOU in advance!
Matt D
What I'm trying to do is find the correct potentiometer resistance to control a signal coming from the speakerphone port on a Cisco IP phone. I'm building a device for work to power some intercom speakers but the level coming out of the phone (~2-4 watts I'd guess) is overloading the "MIC" inputs on my bogen amplifier. Once I turn the volume on the phone down, it works fine--no clipping. The only problem with that is the intercom software turns the volume back up on the phone to maximum; there is no way around this.
Here is the information I know:
The speakerphone output on the phone:
- About 2 watts, no greater than 5w
- Was originally connected to 8ohm 2" speaker
- This is the signal I want to attenuate
The amplifier I'm plugging connecting the speakerphone leads to:
- Going into a Low Impedence MIC Input
- 35 Watts output to 70V horns
- Has independent Vol/Bass/Treble (if that's important)
My proposed plan was to wire:
- Speakerphone output to lug 1 of the pot
- Wire lug 2 to the terminal block on the box
- Wire lug 3 to ground
My questions:
- What resistance potentiometer do I need? Will a 10k work? Linear ok?
- Is the impendence differences going to give me problems? I know the MIC input in low impedence, will the 8ohm speakerphone output be ok?
- Am I missing anything other than just attenuating the signal with a pot?
Here's a semi-crappy phone picture of the project.
Let me know if you need anything else and a big THANK YOU in advance!
Matt D
What I really need is a trimmer that I can set-and-forget. 
