TDA1541 and others current out DAC tube out stage.

[Zoran]

If You have in dac device Iout-Riv-tubeAplification-bufferOutput, then You aready have IN phase output. IF the data line input in the dac positive or original like it is in all interface devices.
What is going on about phase is:
+Iout>@Riv(Vout=-180deg)>TubeGainStage(Vout=-180+(-180)=-360=0deg IN phase>Buffer no phase change, IN phase output.
.
BUT if we have Preamplifier with only one gain tube stage after preamp the phase will be again -180deg into the amplifier input.
So, for the preamp with single ended tube stage, to be phase in = phase out, input transformer is a must and more optimal then Output transformer in anode. Because of the higher Ri of tubes it is harder to employ good output transformer. Much easier way to configure preamp with input transformer and use Buffered low impedance outputs from DAC, Riaa preamps and other sources to the preamplifier.
In this way You will always have proper phase for all sources to the loudspeaker terminals. 🙂
.
I will maybe draw the pictures latter will be maybe more clear?
Thanks

 

[diyiggy]

Many thanks for the detailed answer. Do not bother with a schem, it is clear enough 🙂

 

[57786]

That is what I ask 🙂 ...how to add 180 degree for the output to stay in phase ?
Coming back to a 2 stages conf one tube for I/V and a second for the buffer ? No if I read tje answer.
Or does it not matter much ?

Simply reverse the speaker cable polarity ;-)

 

[diyiggy]

.... nice an simple way to check if it sounds better 🙂
Sometimes you just see that you listened your loudspeaker not in phase for 30 years...uh!