Any comments on DAC directly to Power amp with no

08-18-15: Hgeifman
I am concerned about having a fully balanced DAC running into a fully balanced amplifier and NOT take advantage of the two balanced units. My test should help me decide how to proceed.

Although the L-590AX is described in various places as being fully balanced, I'm not sure that is the case. First, it seems unusual for a balanced amp to provide most of its line-level connections via RCA's, as can be seen in this rear panel photo, including the pre-out and main in connections as you mentioned. Also, the lightning bolt symbols near the speaker terminals, which are presumably intended to alert the user to the possible presence of high voltage, are adjacent to each of the red terminals but none of the black terminals. (A balanced amp would provide voltages on the black terminals that are essentially identical to those on the red terminals, aside from a polarity inversion). Also, in many cases a balanced amp will have a statement on the rear panel cautioning against grounding the negative (black) terminals, which is not present in this case. Check and see if the manual has such a statement; if not, it would cast further doubt on the amp being balanced.

So in the event my suspicion is correct, as George suggested above supplying the amp with a single-ended signal may actually be preferable to supplying it with a balanced signal, since it would eliminate a balanced to unbalanced conversion from the signal path.

Also, if you have a multimeter available you could make some simple measurements to verify whether or not the amp is fully balanced. Post back if you'd like further info on how to do that.

In any event, good luck as you proceed.

Regards,
-- Al

08-20-15: Hgeifman
My plan is:

1) Plug the Bricasti M1 DAC using balanced XLR cables into the balanced inputs on the 590ax. This means the 590ax is operating an integrated amplifier including its pre-amplifier. The Bricasti M1 will only operate as a DAC.

2) Plug the Bricasti M1 DAC using RCA cables into the RCA main in jacks on the 590ax and press the separate button on the front panel. I will turn the input selector to another setting but I do not know what setting yet (any suggestions?). This might not be important since the separate switch is on. The volume control will be done using the Bricasti M1 DAC and not the volume control on the 590ax.

The above cable wiring and operation will enable me to easily switch between integrated amplifier operation and the Bricasti M1 DAC used as a pre-amplifier (and its volume control).

Presumably selecting "separate" mode disconnects the preamp section of the integrated from the power amp section, and I would guess (and hope) that deselecting "separate" disconnects the "main in" jacks from the power amp section. However even if all of that is the case, if both inputs are connected to the Bricasti simultaneously it is possible that some low level leakage of the signals coming in on the input that is not selected could find its way to the power amp section, with audible consequences.

Therefore if you want to have both connections in place at the same time what I would suggest is that you first connect each of them individually, and verify that with the other one selected (but not connected) that you don't hear anything, or at least that you hear very little. If you do hear something when main in is selected but not connected, changing the input selection to something other than the balanced input that is being used may help.

Of course, only change connections while the amp is turned off.

Also, you may want to make use of the level adjust set screws on the rear of the Bricasti, which control the level of its balanced outputs only, to equalize the volume levels in the comparison.

Finally, I'll mention that fortunately the Bricasti drives its unbalanced and balanced outputs from separate and independent driver stages, according to its manual. With a lot of other designs, in which that is not the case, the results of your comparison might be muddled or altered if both outputs were connected at once.

Good luck. Regards,
-- Al