I'm brand new here. Very briefly, I'm familiar with basic analog electronics with most of experience is in the area of designing and building vacuum tube guitar amplifiers and solid state guitar effects pedals. But, I've come across a challenge in a large, somewhat unfamiliar project that I'd like a second opinion (or more) on.
I'm close to completing a "play console" for my two young grandsons, 18 months, and 3 years old. They love turning on switches and things that make noise. So I built a small angled console with lots of LED's, switches and noise making devices. These devices include: Atari punk console, a 555 timer 12 note "organ", an electronic siren, and a surplus 1 minute timer with flashing LEDs and piezo.
Since all of these generate enough output to drive a small speaker or piezo device I decided to tie them together via a simple BJT (2n2222) 4 channel mixer and then into a 1 watt TDA7052 power amp chip and then to small 8 ohm speaker. Upon testing I encountered two issues.
Devices not connected to the mixer can be heard through the amp output, not loudly but they are there. And, the output of several devices is seriously attenuated through the mixer. The power supply is 6 D cells in series for 9 volts.
In tube guitar amps, the practice of decoupling amplification stages using resistors and capacitors in the power supply is used to prevent low frequency oscillation between stages. In this project I'm feeding each device directly off the battery power supply. Is this possibly the reason I'm getting cross talk even when the output of the individual circuits is not connected to the mixer?
And is it possible I'm loosing signal via the active mixer I built? I was going to use a JFET mixer as they have a higher impedance, but went with the 2n2222 instead because i had all the parts i needed on hand.
Before diving in to make changes can anyone tell me if I'm on the right track?
I'm close to completing a "play console" for my two young grandsons, 18 months, and 3 years old. They love turning on switches and things that make noise. So I built a small angled console with lots of LED's, switches and noise making devices. These devices include: Atari punk console, a 555 timer 12 note "organ", an electronic siren, and a surplus 1 minute timer with flashing LEDs and piezo.
Since all of these generate enough output to drive a small speaker or piezo device I decided to tie them together via a simple BJT (2n2222) 4 channel mixer and then into a 1 watt TDA7052 power amp chip and then to small 8 ohm speaker. Upon testing I encountered two issues.
Devices not connected to the mixer can be heard through the amp output, not loudly but they are there. And, the output of several devices is seriously attenuated through the mixer. The power supply is 6 D cells in series for 9 volts.
In tube guitar amps, the practice of decoupling amplification stages using resistors and capacitors in the power supply is used to prevent low frequency oscillation between stages. In this project I'm feeding each device directly off the battery power supply. Is this possibly the reason I'm getting cross talk even when the output of the individual circuits is not connected to the mixer?
And is it possible I'm loosing signal via the active mixer I built? I was going to use a JFET mixer as they have a higher impedance, but went with the 2n2222 instead because i had all the parts i needed on hand.
Before diving in to make changes can anyone tell me if I'm on the right track?
