Hey all,
Digging through my parts bins, I came across a TDA7375 that I got years back. Thought it would be perfect for a little 2.1 amp I want to build for my rec room.
Looked up the spec sheet and found that it is a 4-channel, single supply power amp, that can be configured as 4-channel, or 2-channel bridge mode, or 2.1-channel (2 normal/1 bridged pair).
Now, my experience with bridging amps goes back 40 years when I worked in the sound business, where we would bridge a stereo power-amp by sending the same signal to both channels, but physically reversing the phase into channel B (later amps had this function built in via a switch), and connecting the speaker between the two positive outputs.
But, as I look at the circuit examples for the TDA7375, it shows feeding the same signal to two of the channels, and speaker between the two outputs, but no phase reversal of one input.
This contradicts what I remember about reversing one input because in theory, (simple terms) you are amplifying the normal signal and sending to speaker POS, and amplifying the phase reversed single and sending it to the speaker NEG. Like a Balanced Drive without a ground reference, so if you did not reverse phase of one input, then the outputs would cancel each other out (phase cancellation).
I'll go ahead and lay it out as the specs show, every reference I've found shows it that way.
But, can anyone here explain to me, WHY?
Does it have something to do with the single supply topology of this chip versus the dual supply of a bigger power amp?
What am I missing?
Regards,
JohnR
Digging through my parts bins, I came across a TDA7375 that I got years back. Thought it would be perfect for a little 2.1 amp I want to build for my rec room.
Looked up the spec sheet and found that it is a 4-channel, single supply power amp, that can be configured as 4-channel, or 2-channel bridge mode, or 2.1-channel (2 normal/1 bridged pair).
Now, my experience with bridging amps goes back 40 years when I worked in the sound business, where we would bridge a stereo power-amp by sending the same signal to both channels, but physically reversing the phase into channel B (later amps had this function built in via a switch), and connecting the speaker between the two positive outputs.
But, as I look at the circuit examples for the TDA7375, it shows feeding the same signal to two of the channels, and speaker between the two outputs, but no phase reversal of one input.
This contradicts what I remember about reversing one input because in theory, (simple terms) you are amplifying the normal signal and sending to speaker POS, and amplifying the phase reversed single and sending it to the speaker NEG. Like a Balanced Drive without a ground reference, so if you did not reverse phase of one input, then the outputs would cancel each other out (phase cancellation).
I'll go ahead and lay it out as the specs show, every reference I've found shows it that way.
But, can anyone here explain to me, WHY?
Does it have something to do with the single supply topology of this chip versus the dual supply of a bigger power amp?
What am I missing?
Regards,
JohnR
Hi
if you take a look at the datasheet, and the very poor quality internal diagram (!), you'll notice that the chip contains two amps inverting, and two amps non inverting. You should then connect your input signal to IN1 & IN2 and to IN3 & IN4; speakers will go between OUT1&2 and OUT3&4. Bridge config allow you to get more power for same supply and avoid using output cap. This chip was initially designed for car audio. I found one (a very close one : a TDA7377) in a small Bose desktop speaker I grabbed in the dumpster last week....
Rgds.
Chris
if you take a look at the datasheet, and the very poor quality internal diagram (!), you'll notice that the chip contains two amps inverting, and two amps non inverting. You should then connect your input signal to IN1 & IN2 and to IN3 & IN4; speakers will go between OUT1&2 and OUT3&4. Bridge config allow you to get more power for same supply and avoid using output cap. This chip was initially designed for car audio. I found one (a very close one : a TDA7377) in a small Bose desktop speaker I grabbed in the dumpster last week....
Rgds.
Chris
so then this means the phase inversion is internal? that would make sense, but that also then means, that if you use IN1 & IN2 as two separate amps (not bridged) then they will be out of phase?
JohnR
JohnR
Yes. Chip was intended to car radio market. Car radio manufacturer were able to swap + / - of loudspeaker for rear/front with a 4 speakers config. As far as I remember, car radio output were usually two wires, not single with the second connected to chassis ground.
That's a way to avoid highlighting this annoying characteristic, but I'm sure guys at Blaupunkt, Clarion, Alpine or whoever car radio manufacturer, were properly handling it!
But, I think this kind of chip was mainly used bridged : this is where it is good.
But, I think this kind of chip was mainly used bridged : this is where it is good.
Alright then, Bridge Mode figured out...
Now, does anyone have experience with the Stand-By Input?
Do I need to supply 5V to make it play, or to make it mute?
Now, does anyone have experience with the Stand-By Input?
Do I need to supply 5V to make it play, or to make it mute?
