Stereo / 2 chan Audio cut off

S

stuee

Member

• Sep 4, 2015

• #1

Hi.
Im after a circuit for a 2 channel audio cut off.
I run a venue in my town and have the jukebox going through a mixer then to a active yamaha speaker.
I put the mixer in so the volume can be controlled and set the speaker at what i want maximum and removed the knob.
The problem im having is the smart kids work out how to turn this up and im getting complaints also when they plug a phone it the level is louder too.
I want to add a small circuit between the circuit and speaker so it keeps the constant line volume from the mixer.

Can anyone help me with this?

thanks

 

crutschow

Well-Known Member

Most Helpful Member

• Sep 5, 2015

• #2

You could perhaps add some type of automatic gain control (AGC).
The problem with that is it tends to make all the parts of the music the same level, so the quiet parts of the music become louder and the loud parts become softer.

 

L

Les Jones

Well-Known Member

Most Helpful Member

• Sep 5, 2015

• #3

Why not just a fixed attenuator to set the volume with all the gain controls set to maximum. (Just two resistors on each channel.)

Les.

 

alec_t

Well-Known Member

Most Helpful Member

• Sep 5, 2015

• #4

Perhaps use diodes to clip levels above some threshold? That would introduce enough distortion near the threshold to (hopefully) encourage the kids to turn the wick down.

 

K

KeepItSimpleStupid

Well-Known Member

Most Helpful Member

• Sep 5, 2015

• #5

stuee: While researching something similar, I ran into these https://www.canford.co.uk/Index/Sound-level-control-units units, Pricey and note the mains voltages.

Measuring levels the right way can get pretty tough.

Automatic volume controls get wierd too, because of silences.

An idea was to base it on a LOG scale bar graph display driver, using opto-isolators where the LED would go. Use a priority encoder to get the max level exceeded over a time period. You'd have a warning phase before the power/audio input would go away.

The harder problem is tamper and interfacing and/or using signal levels or levels measured by a microphone.

 

S

stuee

Member

• Sep 6, 2015

• #6

Im liking the suggestions, the line out from the mixer goes up and through the roof to the wall mounted speakers so i can put anything inline in the roof so they cant access it.
So how would i go about the diode limit as i like the distortion idea.
I just wanted it so it wont go higher than a certain loudness.

 

K

KeepItSimpleStupid

Well-Known Member

Most Helpful Member

• Sep 6, 2015

• #7

Wireless control is a "possibility" too. Sending up, class II (Power limited, low voltage) power doesn't require anything special.

 

S

stuee

Member

• Sep 6, 2015

• #8

wireless control?

 

audioguru

Well-Known Member

Most Helpful Member

• Sep 6, 2015

• #9

Distortion sounds bad. Kids do not know about High Fidelity so they LIKE distortion.
Tweeters are easily blown by the high power in the many harmonics of distortion.

Diodes to limit the power and produce distortion are connected as negative feedback in the amplifier circuit, not in the lines to the speakers.

 

alec_t

Well-Known Member

Most Helpful Member

• Sep 7, 2015

• #10

stuee said:

So how would i go about the diode limit as i like the distortion idea.

Click to expand...

The limiter would need to be in the preamp stage, or an early stage of the power amp. Do you have a schematic of the preamp/amp?