Hello,
I've made several recent posts regarding an amp I'm building based on the TDA7294. This will be for a pair of speakers connected to two computers, plus an aux input. It has a built-in mixer to select between the three inputs, plus a low-level subwoofer output and a headphone jack. The ring switch on the headphone jack activates the mute function of the main amplifier.
The completed proposed circuit is attached. It has been mostly prototpyted on a breadboard, and I am getting ready to solder it together 'for real'. But first, I'd like to post it here for any comments.
The power on-off sequence (thank you to crutschow) turns off the standby and mute after the amp is powered on, and turns them back on again before the amp powers down. The 10,000 uF and 1,000 uF caps in the power circuit keep the amp running long enough for the power off sequence to work.
The input mixer is based on this from CircuitLib http://www.circuitlib.com/index.php/tutorials/product/39-how-to-build-an-audio-mixer
I've replaced the trimmer pots with conventional resistors.
For the headphone output, I've tweaked the cmoy headphone amp (thank you to audioguru, Nigel Goodwin and others for your comments) to make it inverting. I haven't prototyped this part yet, so don't know if it works as expected.
The subwoofer output uses a variable low-pass and volume control, taken from this post **broken link removed**
My subwoofer amp actually has both, but the amp is stuck in pypass mode and is tucked way under my desk where it's inconvenient to adjust the volume - since I'm building this just for me, easier to add these functions here so I can tweak them from my desk rather than crawl under to turn down the subwoofer whenever my wife says it's shaking things too much.
I appreciate the help I've received so far, and I'm sure this amp could use some more tweaks. One thing in particular I'm unsure about is my selection of Op Amps. I've used whatever was suggested from the circuit I'm copying, so I have three separate Op Amps for three different circuit functions. I confess I understand very little about the differences between the multitude of Op Amps out there. I've read a few postings and webpages on this, but my eyes have quickly glazed over trying.
Thank you all and I appreciate your helpful comments.
I've made several recent posts regarding an amp I'm building based on the TDA7294. This will be for a pair of speakers connected to two computers, plus an aux input. It has a built-in mixer to select between the three inputs, plus a low-level subwoofer output and a headphone jack. The ring switch on the headphone jack activates the mute function of the main amplifier.
The completed proposed circuit is attached. It has been mostly prototpyted on a breadboard, and I am getting ready to solder it together 'for real'. But first, I'd like to post it here for any comments.
The power on-off sequence (thank you to crutschow) turns off the standby and mute after the amp is powered on, and turns them back on again before the amp powers down. The 10,000 uF and 1,000 uF caps in the power circuit keep the amp running long enough for the power off sequence to work.
The input mixer is based on this from CircuitLib http://www.circuitlib.com/index.php/tutorials/product/39-how-to-build-an-audio-mixer
I've replaced the trimmer pots with conventional resistors.
For the headphone output, I've tweaked the cmoy headphone amp (thank you to audioguru, Nigel Goodwin and others for your comments) to make it inverting. I haven't prototyped this part yet, so don't know if it works as expected.
The subwoofer output uses a variable low-pass and volume control, taken from this post **broken link removed**
My subwoofer amp actually has both, but the amp is stuck in pypass mode and is tucked way under my desk where it's inconvenient to adjust the volume - since I'm building this just for me, easier to add these functions here so I can tweak them from my desk rather than crawl under to turn down the subwoofer whenever my wife says it's shaking things too much.
I appreciate the help I've received so far, and I'm sure this amp could use some more tweaks. One thing in particular I'm unsure about is my selection of Op Amps. I've used whatever was suggested from the circuit I'm copying, so I have three separate Op Amps for three different circuit functions. I confess I understand very little about the differences between the multitude of Op Amps out there. I've read a few postings and webpages on this, but my eyes have quickly glazed over trying.
Thank you all and I appreciate your helpful comments.