I built this metronome, with an added volume knob at the end:
http://www.555-timer-circuits.com/metronome.html and I built this guitar preamp: https://electronicscheme.net/guitar-pre-amp-with-jfet-2n5457/guitar-preamp-design/ and it works fine on its own, but when I connect the metronome to the same 9v battery, the metronome leaks into the preamp's output. Is this because of the capacitor between power rails in the preamp? It's not in the preamp circuit. If that's the problem, how do I separate the capacitor from the metronome's power rails? Also, I built the mixer circuit#2 on this page to mix the two signals: http://www.all-electric.com/schematic/simp_mix.htm using a TL022, but I'm not getting a signal out of either opamp.
http://www.555-timer-circuits.com/metronome.html and I built this guitar preamp: https://electronicscheme.net/guitar-pre-amp-with-jfet-2n5457/guitar-preamp-design/ and it works fine on its own, but when I connect the metronome to the same 9v battery, the metronome leaks into the preamp's output. Is this because of the capacitor between power rails in the preamp? It's not in the preamp circuit. If that's the problem, how do I separate the capacitor from the metronome's power rails? Also, I built the mixer circuit#2 on this page to mix the two signals: http://www.all-electric.com/schematic/simp_mix.htm using a TL022, but I'm not getting a signal out of either opamp.
Just use a separate 9V battery for the metronome to stop the noise.
The other problem is distinct.
The other problem is distinct.
With a resistor and a second capacitor from the downstream side to ground. Unless the separate battery idea works for you. What value resistor? Depends on the current draw from your 555 metronome circuit. Maybe pick to drop a volt or so to the cap. What value cap? Electrolytic 10 - 100 - 1000 uf; whatever you have lying around, good for 9V. Hopefully, you have this stuff on hand.
The mixer circuit should work.
But the circuit shown assumes Dual rail power supply.
If using a Single Rail power supply. Such as single 9 volt
Few changes are needed. Which is mainly a virtual
ground for some connections.
The 555 timer square wave output is close to the full 9 volts
so you could add volume adjustment on the output which
would provide a easier load for it to drive.
If you would rather have it as a output signal for a mixer.
Rather than directly driving a speaker. Somewhat tough load for it to drive
directly. Could use a small speaker for a TV or such that is 16 or 32 ohms
so the power rail wont be pulsed so much.
Likely yes it would pulse the power supply so could use 100 uf
power rail decoupling capacitor to help.
Could use a small resistor in line with the preamp power rail like 8 or 10 ohms
and increase the decoupling cap as well.
But the circuit shown assumes Dual rail power supply.
If using a Single Rail power supply. Such as single 9 volt
Few changes are needed. Which is mainly a virtual
ground for some connections.
The 555 timer square wave output is close to the full 9 volts
so you could add volume adjustment on the output which
would provide a easier load for it to drive.
If you would rather have it as a output signal for a mixer.
Rather than directly driving a speaker. Somewhat tough load for it to drive
directly. Could use a small speaker for a TV or such that is 16 or 32 ohms
so the power rail wont be pulsed so much.
Likely yes it would pulse the power supply so could use 100 uf
power rail decoupling capacitor to help.
Could use a small resistor in line with the preamp power rail like 8 or 10 ohms
and increase the decoupling cap as well.
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That was just the assumption why the mixer circuit
was not working.
If powered by single supply 9 volt.
It just needed some changes. Mainly R1/R2 is a
simple voltage divider which would be 4.5 volts reference voltage.
or 1/2 supply to form virtual ground.
Virtual Ground was just needed for both + non inverting opamp inputs
to work properly. All other connections same.
TL022 is obviously a dual package and both opamps
share same power pins 8 =Vcc 9volts and 4 = Gnd ( Battery Ground) .
I just show additional connections
for it to work in the spice program used.
was not working.
If powered by single supply 9 volt.
It just needed some changes. Mainly R1/R2 is a
simple voltage divider which would be 4.5 volts reference voltage.
or 1/2 supply to form virtual ground.
Virtual Ground was just needed for both + non inverting opamp inputs
to work properly. All other connections same.
TL022 is obviously a dual package and both opamps
share same power pins 8 =Vcc 9volts and 4 = Gnd ( Battery Ground) .
I just show additional connections
for it to work in the spice program used.
For the Guitar pre to help isolate big power surges from the 555 timer
if using same supply. Just add small resistor around 47 to 100 ohms
and increase decoupling capacitor to 100 uF
Same thing with the 555 circuit pretty common to add 100 or 220uF decoupling
cap close as possible to supply pin. Could add small resistor similar to shown
with guitar pre. But 100 ohms might cause to large voltage drop
anything from 3.3 ohms to around 15 ohms. likely just the cap would
help more than anything.
if using same supply. Just add small resistor around 47 to 100 ohms
and increase decoupling capacitor to 100 uF
Same thing with the 555 circuit pretty common to add 100 or 220uF decoupling
cap close as possible to supply pin. Could add small resistor similar to shown
with guitar pre. But 100 ohms might cause to large voltage drop
anything from 3.3 ohms to around 15 ohms. likely just the cap would
help more than anything.
Standard 555's are very very noisy(*) on the power line - replace with a CMOS 555 (such as the 7555) and it should be quieter and easier to filter out, or change C3 to a much larger value. Learn about star-grounding - you must avoid sharing the metronome spike currents on the same wires that contribute to the guitar input signal (often the ground is the culprit - you forget that ground wires are low value resistors that will exhibit voltage drops).
If you can't star ground, use thicker ground wires.
(*) original 555's can pull something like 250mA spikes direct from their supply, its their dirty little secret - CMOS versions don't spike like this.
If you can't star ground, use thicker ground wires.
(*) original 555's can pull something like 250mA spikes direct from their supply, its their dirty little secret - CMOS versions don't spike like this.
Thanks everyone. I fixed it by using the simpler version of the mixer on that same link, still including the input capacitors, and fixed the metronome noise by using a lower value pot for it's volume control. Now it's almost inaudible at lowest volume compared to the preamp at the highest volume.