Paul wrote:
https://www.gearslutz.com/board/atta..._schematic.pdf
Ok first off, the TR5 is similar to the TR8 on the front end, with
the TL072 Opamp configured as an inverting, unity-gain buffer amp.
** Normally called a one op-amp, differential input stage.
So it's normal to NOT see any signal on the input differential pins 2
and 3, right?
** Depending how the inputs are driven ( one, the other or both) you may or may not see any signal on op-amp pins 2 and 3.
Secondly, on all these models, the so-called "power" switch only
turns on the LED, and turns off the mute on the two power amps,
which means the rail voltages are ALWAYS ON the Opamp and the final
amp, no matter the state of the switch, as long as the 3 prong AC
cord is plugged into the unit. This means the leakage currents in
the ICs are always there, which would explain why the back plates
of these units stayed warm, even when I turned them "Off."
Is this what they typically do with these smaller reference speakers
to maybe save money for the bean counters?
** It is commonly done like this for several reasons.
Why not put a switch
with more poles, so you can turn the rail voltages off too?
** That would require a much larger switch connected in the AC wiring and make a loud thump when operated - while the "mute" function on the LM3886 operates quietly.
Some designs even have a SMPS running continuously, generating lots more heat and often failing in a few years of use.
The Event TR series use conventional power supplies and simple circuits - so get my approval.
..... Phil