Analogue Dub Siren

[Rorut]

Thanks a lot!
I have another related question. What is the best way to amplify the audio signal that is coming out from the circuit? If i connect the siren to my dj mixer and play effects when on PA sound system the effects barely hears. I want to boost the signal as much as possible. Tried the circuit attached with the LM358 but dont think it did much at all...

Is that circuit for very low signals? Maybe my signal is high enough and cant be more amplifyed by that circuit?

 

[audioguru]

Your LM358 circuit is an inverting opamp with a very low input impedance of only 1k ohms which is killing the high output impedance level of the circuit that seems to have its output wrongly coming out of the 9V battery in the schematic.
Note that an LM358 or LM324 opamp has awful crossover distortion and has trouble with high levels above only 2kHz.
Use an opamp as non-inverting with the same gain but with a high input impedance like this:

 

[Rorut]

Your LM358 circuit is an inverting opamp with a very low input impedance of only 1k ohms which is killing the high output impedance level of the circuit that seems to have its output wrongly coming out of the 9V battery in the schematic.
Note that an LM358 or LM324 opamp has awful crossover distortion and has trouble with high levels above only 2kHz.
Use an opamp as non-inverting with the same gain but with a high input impedance like this:

Thank you very much for the circuit! Can I just change what I already have to your suggestion and it will work better? With the same LM358?
Or do you recommend something else that I can replace LM358 with?
Would it be hard to make the changes you made for the circuit above to this variant that is stereo?

 

[audioguru]

The LM358 is fine to produce siren noises but is awful for music. The second opamp in the LM358 can simply be used for the second channel on your stereo pre-amplifier and its pin numbers are shown on its datasheet.

Why do you need a stereo siren? One siren circuit can feed one pre-amplifier and the one pre-amplifier can feed as many power amplifier channels as you want.

 

[Rorut]

The LM358 is fine to produce siren noises but is awful for music. The second opamp in the LM358 can simply be used for the second channel on your stereo pre-amplifier and its pin numbers are shown on its datasheet.

Why do you need a stereo siren? One siren circuit can feed one pre-amplifier and the one pre-amplifier can feed as many power amplifier channels as you want.

Thank you!
I have two sirens in the same box sharing same output connection with difference in gain/level and bought the stereo circuit kit just to connect the sirens on individual channels to match the outputs. That is working well and it would be nice if I could change the circuit to non-inverted that you showed me on the mono version. I can do two separate mono circuits for each siren but if I do that I need two LM358 instead of one. Appreciate your help a lot!

 

[audioguru]

To make a stereo pre-amp like I showed you need only one LM358 because it has two opamps in it. Its datasheet shows the input and output pins on its two opamps.

 

[Rorut]

Thanks, i will try and see if I can work it out
You changed the level potentiometer to 10K instead of 22K. Can i use the 22K in your version, dont ha e a 10K at the moment

 

[audioguru]

You van use a 22K volume control if you want.

 

[Rorut]

Thanks!
Just curious, what would be good for music if lm358 is awful for that?

 

[audioguru]

The LM358 dual and LM324 quad opamps were made for very low power supply current draw. Therefore they are noisy (hiss), have poor high frequency skew rate and have not enough bias current so they produce crossover distortion.
An "audio" opamp is used for audio. It has very low noise, has extremely low distortion and produces frequencies up to at least 100kHz easily. An example is an OPA134 single, OPA2134 dual and OPA4134 quad. There are many others.

 

[Rorut]

The OPA2134 looks similar to the LM358. Can I plugnplay change to a Opa2134 in the circuit you helped me with above?

One like this
https://www.electrokit.com/opa2134pa.44018

 

[audioguru]

The circuit I drew can use an LM358 and sound awful or use an OPA2134PA and sound wonderful with no changes.
Your schematic does not show a power supply voltage. For the OPA2134 that has a minimum supply of 5V then use 6v or more.

 

[Rorut]

The circuit I drew can use an LM358 and sound awful or use an OPA2134PA and sound wonderful with no changes.
Your schematic does not show a power supply voltage. For the OPA2134 that has a minimum supply of 5V then use 6v or more.

Sounds wonderful. Thank you very much for all help. I will try and redraw the stereo version later and post it here hoping you can have a quick look if all looks ok. Im using 9v or 12v supply.

I will use the opa2134 to boost the music before a delay Im using.

 

[audioguru]

What plays your low level music? A magnetic pickup in a record player or a tape head (they need equalization)? Or a microphone?
Will the delay circuit be driving a power amplifier? Why doesn't the power amplifier have enough gain?

 

[Rorut]

What plays your low level music? A magnetic pickup in a record player or a tape head (they need equalization)? Or a microphone?
Will the delay circuit be driving a power amplifier? Why doesn't the power amplifier have enough gain?

I have two technics 1210 record players and a DJ mixer, Vestax 05 pro 3 with FX loop (send and recieve). Im using this little delay that adds delay to the music . I also having my effects going through the delay. When I connect the mixer to big PA speaker system the delay and effects barely hears. So I need somehow to boost the signal. I think its wierd my dj mixer cant handle it, but I have the FX potentiomers on max on the mixer...

 

[audioguru]

Don't your record players use magnetic cartridges and don't the mixers have "phono" inputs with RIAA equalization and plenty of gain for them?
A mixer is designed to feed a power amplifier, not a speaker.

 

[Rorut]

Yes all that. Mixer is ofcourse always connected to a amplifier. Never directly to speakers. It is something with the send and return that is supposed to handle external effects on the mixer. Dont know how that is built inside bit it dont increases the signal enough. Works ok on low volume but when playing very loud effects is to low

 

[Rorut]

Would this be correct for a stereo version of what you did? Feels like I missed or did something wrong

 

[Rorut]

I will try to put this together later today. Would be very grateful if someone could confirm that the diagram above looks ok

 

[spec]

Hi Rorut,

Just two 220K resistors missing.

I suspect you can replace the two 2.2uF capacitors with wire links.

spec