Design for my job at station

[Johnny1234]

Hi all any advice is greatly appreciated.

I need to modify a box at work. The original has an amplifer driving a 2 inch 16 ohm speaker.
I need to:
1 Add a line out
2 Have a switch to alternate between speaker and line out
3 Add a volume control for the line out and speaker

Below is a little diagram of my thoughts. All ideas are greatly appreciated, but simpler is better.
Many Thanks

 

[Johnny1234]

Sorry I know the pot has to be before the switch my bad.

 

[ccaudle]

1 Add a line out

How is the signal delivered to the amplifier in the box? Do you already have access to a line level signal coming in, or the speaker is part of something else and you cannot easily access as line level?

What is the level sent to the speaker? (presumably pretty low since it is a 2" speaker, but you will still need to know typical and max to determine how to adapt to line level).

What nominal "line level" do you want? What consumer equipment considers line level and what pro equipment considers line level is quite a bit different.

 

[Johnny1234]

The box is for a college game show that we will host. Signal is derived internally, it just beeps lol. I don't have easy access to the line level input. Speaker level very low I would imagine about 1 volt. Nominal level would be for pro audio input.

 

[Johnny1234]

level to speaker about 17 volts peak.

 

[Brian Roth]

Sorry I know the pot has to be before the switch my bad.

Actually, the pot is in a good location for the mod. However, the way it's drawn means the amplifier's output will be shorted when the pot's setting is turned "off".

Bri

 

[Johnny1234]

Actually, the pot is in a good location for the mod. However, the way it's drawn means the amplifier's output will be shorted when the pot's setting is turned "off".

Bri

Great point, I will put a 100 ohm 5 watt resistor in series with the wiper of the potentiometer.

 

[ccaudle]

I will put a 100 ohm 5 watt resistor in series with the wiper of the potentiometer

Or you could just wire it more typically, where the signal connects to the top of the pot, and the wiper connects to the output.

 

[Johnny1234]

Or you could just wire it more typically, where the signal connects to the top of the pot, and the wiper connects to the output.

Thanks even better. Any ideas for a transformer, it is very low fi just a beep.

 

[Brian Roth]

Thanks even better. Any ideas for a transformer, it is very low fi just a beep.

What are the specs for the input being fed from the beep-o-matic <g>? +4 dBu or -10 dBV line level, low Z mic level, guitar amp instrument level, etc. etc.



Sorry....couldn't resist....

Bri

 

[Johnny1234]

What are the specs for the input being fed from the beep-o-matic <g>? +4 dBu or -10 dBV line level, low Z mic level, guitar amp instrument level, etc. etc.



Sorry....couldn't resist....

Bri

LOL I love it made me smile after a tough week at work. Input will be like a Makie line input 10K ohms.

 

[Brian Roth]

level to speaker about 17 volts peak.

OK....curious how you figured that voltage spec. Oscilloscope? Regardless, seems like a step-down xfmr would be a good idea.

I'll pick this up later after I have some tacos for dinner<g>.

Bri

 

[Johnny1234]

OK....curious how you figured that voltage spec. Oscilloscope? Regardless, seems like a step-down xfmr would be a good idea.

I'll pick this up later after I have some tacos for dinner<g>.

Bri

Thank you Brian, Yes measured on a oscilloscope. Beeps to fast to measure with rms volt meter.

 

[Brian Roth]

Thank you Brian, Yes measured on a oscilloscope. Beeps to fast to measure with rms volt meter.

OK.....peak or peak to peak?

Regardless, maybe something like a xfmr "rated" for 10K:600 Ohms. Nice step down ratio to drop the signal to a reasonable level. I seriously doubt you need the beeps to slam the mixer's VU meter....lol.

Damn....their prices have gone up:

https://edcorusa.com/products/wsm-s...-matching-transformers?variant=41117605298363

What do you have in your junkbox? Like, any xfmrs intended for "70 Volt" loudspeaker distribution systems (ie the 8" speakers attached on frisbies in the ceiling tiles at Applebees)?

Bri