Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Need to take 3 amplified signals, mix and get pre-amp out.

Status
Not open for further replies.

mramos1

Active Member
I have low, mid and high levels out from an amplifier.

I would like to mix them into one channel and convert them to line level out (actually have .5-4 volts out). I see a lot on mixing audio on the internet. They are as simple at 10K resistors and tieing them all together.

Anyone have something that will do this? Or direction? Would I use an op-amp and AGC to do it?
 
If the levels are a known quantity, then simply mix them using different value resistors, and preferably a virtual earth mixer - no need for AGC, unless the signal vary a lot, and you want to change that.
 
Perfect. Second link will get me rolling.

Another question on audio and the earth mixer. It shows 1 wire inputs. So it the output of an amplifier, if I tied the positive wire to the input, where does the negative wire connect to? The op-amp will use +/- rails, the input is one side of the amps output (wire for the speaker).

I will read a few more links, but thought I would ask as well.

Thanks again for the name of the mixer.
 
mramos1 said:
Perfect. Second link will get me rolling.

Another question on audio and the earth mixer. It shows 1 wire inputs. So it the output of an amplifier, if I tied the positive wire to the input, where does the negative wire connect to? The op-amp will use +/- rails, the input is one side of the amps output (wire for the speaker).

I will read a few more links, but thought I would ask as well.

Thanks again for the name of the mixer.

The screens of the cables connect to 0V (also known as ground or chassis).

But I suggest you try posting the circuit?, so we can see exactly what you're trying to do!.
 
I found a nice circuit, I will draw it up and my modifications and upload in the next couple days.
 
They are from a car stereo/amp. There is a low frequency output, a mid-range and high. They are for independant speakers. I want to mix them and feed them into another amp and speakers. So I use the factory radio, but another amp and speakers.

I will get the actual names. But it is a new factory car radio.
 
mramos1 said:
They are from a car stereo/amp. There is a low frequency output, a mid-range and high. They are for independant speakers. I want to mix them and feed them into another amp and speakers. So I use the factory radio, but another amp and speakers.

Right, so they are probably the same levels then?, something as simple as three 10K resistors may do all you need?.

Not as nice as a proper mixer, but it's not a very critical job.
 
That was the original thing I found, and did not try. I was worried about the line level out. Maybe I will try that and see how it sounds.
 
I just had a thought.

This is out of the radio amplifier to the speakers. It would go to an 8 ohm load. Would that be a problem for the amp going into 10K? Not matching the load on the output. I am still going to try it :D I have seen quite a few on the internet as well.
 
Transistor amplifiers have an extremely low output impedance, 0.04 ohms or lower. If they have the same output impedance as a speaker then half the output voltage is lost and the output power would be only 1/4 as much as with a very low output impedance. Vacuum tube amplifiers matched their output impedance to be the same as the speaker impedance.

Because the output impedance of a transistor amplifier is so low, a 10k load causes the same output voltage as an 8 ohm load.
 
Thanks AudioGuru and Nigel. Phase 1 will be 10K network.

EDIT: For some reason I was thinking it was like an RF amp and if no load the output transistor would cook.
But that was a long time ago when I played with RF amps. I guess technology has changed there too.
 
Last edited:
An RF amp with a tuned circuit needs to have a certain load impedance or the tuned circuit will increase the voltage and bust the transistor if the antenna is removed. If the load impedance is too low then the current is too high and the transistor gets busted again.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top