Analogue Dub Siren

Rorut · Jan 5, 2017

Could not be more thankful!
I also bought the opa2134 .
Will be fun to compare them

spec · Jan 5, 2017

Rorut said:
Could not be more thankful!
I also bought the opa2134 .
Will be fun to compare them

No probs Rorut- bit of therapy for me.

If you have a HiFi signal the OPA2134 will sound excellent.

spec

audioguru · Jan 5, 2017

A hifi siren sound??

Rorut · Jan 5, 2017

Im using that opa2134 for the music coming from the dj mixer to the delay. Sirens can stay with the Lm358 that you said would do the job

Rorut · Jan 5, 2017

Wired it up but nothing happens just a huuummm anything I can measure to se whats wrong?

spec · Jan 5, 2017

Rorut said:
Wired it up but nothing happens just a huuummm anything I can measure to se whats wrong?

Oh dear. I hope the opamps are not oscillating. C1 (100nF) should be mounted as close as possible to the supply pins on the chip, with as short leads as possible, to provide good supply line decoupling. One dodge is to place the decoupling capacitor across the top of the chip and solder the leads to the top of the chip pins.

What supply voltage are you using?

Turn the 100K potentiometers to minimum (voltage gain of 1)

Measure the supply voltage and 0V actually on the pins of the chip

Measure the voltage at the junction of two pairs of 220K resistors: should be half the supply voltage.

All inputs and outputs of the opamps should at the same voltage as the respective junctions of the 220K resistors.

Good luck

spec

(PS hate to say this but the breadboard layout may be a problem)

Rorut · Jan 5, 2017

thanks spec!
I get a amplified sound on the lower channel of the circuit.
gain pot does not do much but level do

supply voltage 12v

pin1: 10.8v
pin2: 10.8v
pin3: 11.9v
pin4: 0
pin5: 5.9v
pin6: 5.9v
pin7: 5.9v
pin8: 12v

spec · Jan 5, 2017

Rorut said:
thanks spec!
I get a amplified sound on the lower channel of the circuit.
gain pot does not do much but level do

supply voltage 12v

pin1: 10.8v
pin2: 10.8v
pin3: 11.9v
pin4: 0
pin5: 5.9v
pin6: 5.9v
pin7: 5.9v
pin8: 12v

Pins 1, 2 & 3 are incorrect. looks like there is a problem with the voltage at the junction of the two 220K resistors...wrong value?

spec

Rorut · Jan 5, 2017

Happy to know where the problem is Explains why only one channel is working. Resistor values are correct. I probably connected the resistors wrong.
Need some sleep and will give it a second try tomorrow. And practice a bit more on breadboard layout
Thank you very much!

spec · Jan 5, 2017

Rorut said:
Happy to know where the problem is Explains why only one channel is working. Resistor values are correct. I probably connected the resistors wrong.
Need some sleep and will give it a second try tommorow. And practice a bit more on breadboard layout
Thank you very much!

No probs Rorut- have a good sleep and all will fall into place tomorrow.

Are you testing with an LM358? An LM358 would be best to get the circuit going.

Do not worry about hum at this stage. It would be very surprising if there was no hum.

Just to give you a clue, an opamp has a typical low frequency voltage gain of one million which means that just one microvolt at one of the input pins will result in a volt out. You can induce one microvolt on to an opamp pin by just looking at it.

spec

audioguru · Jan 5, 2017

The messy wires and rows of contacts on a solderless breadboard are antennas that pickup mains hum that is all around you. The contacts might be intermittent.

Rorut · Jan 6, 2017

I found the problem at first sight today . Had the both pins of a 220k resistor connected to IC pin3. Now I get sound on both channels. No hum at all, (2.2uF removed some little hum) Moved that 100nF closer to pin 8.

But... How impressed should I be? Gain control does barely do nothing. Level control can adjust sound to zero and to max. Everything at max gives not very much amplification. Almost the same as the first circuit "inverted" I posted.
Why is gain doing almost nothing, maybe I connected something else wrong?
Im working with the cheaper LM358

Happy I got sound

spec · Jan 6, 2017

Rorut said:
I found the problem at first sight today . Had the both pins of a 220k resistor connected to IC pin3. Now I get sound on both channels. No hum at all, (2.2uF removed some little hum) Moved that 100nF closer to pin 8.

But... How impressed should I be? Gain control does barely do nothing. Level control can adjust sound to zero and to max. Everything at max gives not very much amplification. Almost the same as the first circuit "inverted" I posted.
Why is gain doing almost nothing, maybe I connected something else wrong?

Im working with the chesper LM358

Happy I got sound

Ha Ha, good news.

The amplifiers should produce a voltage gain of x 1 (with gain potentiometer set to zero Ohms) and x 100 (with gain set potentiometer set to 100K) I suspect the gain set potentiometers (PR1) are 1K instead of 100K or the 1K fixed resistors (R3) are 100K.

spec

Rorut · Jan 6, 2017

spec said:
Ha Ha, good news.

The amplifiers should produce a voltage gain of x 1 (with gain potentiometer set to zero Ohms) and x 100 (with gain set potentiometer set to 100K) I suspect the gain set potentiometers (PR1) are 1K instead of 100K or the 1K fixed resistors (R3) are 100K.

spec

Yes
Measured pots are 100K and resistors are 1K. So values are correct. Wierd... any other ideas?

spec · Jan 6, 2017

Rorut said:
Yes
Measured pots are 100K and resistors are 1K. So values are correct. Wierd... any other ideas?

Are the lower ends of the 1K resistors connected to 0V via the 4.7uF capacitors?

Are the 4.7uF capacitors the correct value?

Are the 4.7uf capacitors the correct way around?

What is the voltage on the positive connection of the 4.7uF capacitors (should be around 5.9V)?

22uF, or higher, capacitors in place of the 4.7uF capacitors would be more suitable: lower frequency response (but not connected with the fault)

spec

Rorut · Jan 6, 2017

Yes to all.
Voltage on 4.7uF is 6.5v, changed to 33uF but no luck. (Maybe sound quality got better with te 33uF. but not sure about that one)
When i use the 100K trim pot. Nothing happens to volume. Tone of the sound only changes slightly...
It is like it is bending the tone in some frequencies on the gain pot

pin1: 5.2v
pin2: 5.2v
pin3: 5.9v
pin4: 0
pin5: 5.9v
pin6: 5.8v
pin7: 5.8v
pin8: 12v

spec · Jan 6, 2017

Voltage on 4.7uF is 6.5v This is wrong- should be the same as pin 1 & 2 or pin 5 & 6

pin1: 5.2v
pin2: 5.2v
pin3: 5.9v This is odd should be same as pin 1 & 2
pin4: 0
pin5: 5.9v
pin6: 5.8v
pin7: 5.8v
pin8: 12v

What meter are you using. Is it a digital multimeter. Can you establish what the input resistance is from the manual: sshould be around 10M Ohms.

It looks as though the opamps are oscillating, but not sure.

spec

Rorut · Jan 6, 2017

When disconnecting the siren that shares the same power source I get.
pin1: 6.06v
pin2: 6.06v
pin3: 5.99v
pin4: 0
pin5:5.98v
pin6: 6.06v
pin7: 6.06v
pin8: 12v

Using a UNI-T 139C multimeter

audioguru · Jan 6, 2017

Of course it is oscillating. It is built on a solderless breadboard.

spec · Jan 6, 2017

Rorut said:
When disconnecting the siren that shares the same power source I get.
pin1: 6.06v
pin2: 6.06v
pin3: 5.99v
pin4: 0
pin5:5.98v
pin6: 6.06v
pin7: 6.06v
pin8: 12v

Using a UNI-T 139C multimeter

Thanks. That is all good.

I will have a think.

spec

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