Any comments on DAC directly to Power amp with no

All: I want to thank everyone above for your comments and suggestions. They were helpful and appreciated.

Philip from On Higher Note (Luxman Distributor) said "To truly separate the preamp stage from the L-590ax, you need to run an RCA cable into MAIN IN and then hit the SEPARATE switch. If you run balanced cables, you will also be using the preamp stage of the L-590ax”.

He had no comments if the 590ax is, or is not, a fully balanced amplifier. If we have to use the RCA main in jacks on the 590ax, it seems we are not taking advantage of the two balanced units (DAC and amp). I was told that, if RCA plugs separate the pre-amp section from the power amp, my Luxman 590ax is really not "fully balanced". I do not know or understand. The 590ax sounds great so maybe it probably is not important. Any comments on this?

My loaner Bricasti M1 DAC with volume control is due next week. 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).

It is going to be an interesting experiment. I received many different opinions for running the DAC directly vs. through the preamp section of the Luxman. Obviously, it is a very gray area and I need to try it both ways in my system. Thanks again.

"I've seen it all too many times. A typical example of this is my cd player which has both single ended and balanced outputs, the extra opamp they used for the balanced had gain compared to the single ended output, which bypasses the balanced opamp, therefore one less opamp in the signal path from the single ended output."

So, basically what you're saying, is that a manufacturer may raise the gain on a single ended components xlr outputs to make it appear balanced if someone were to look at the spec sheet? I never even considered something like that. My ex-girlfriend from Russia wasn't even that unethical.

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

08-20-15: Zd542
So, basically what you're saying, is that a manufacturer may raise the gain on a single ended components xlr outputs to make it appear balanced if someone were to look at the spec sheet? My ex-girlfriend from Russia wasn't even that unethical.
Zd542

No, no conspiracy, they may have to give them gain of the XLR input or output opamp/s, because many of them (the opamps) are not unity gain stable, this then will give more output voltage from a source or higher input sensitivity on a poweramp.
This then is different to what the single ended outputs or inputs specs are on sources or poweramps, compared to the XLR connections.
And yes many sources and poweramps are single ended before and after that pseudo XLR opamp.

Cheers George

I asked my Luxman dealer about the 590ax being "fully balanced" and his response is below:

"Your Luxman amplifier is a fully balanced design when operated as an integrated amp. The connection between the pre-amplifier and amplifier is internal to the unit (it does not make use of the pre-out/main-in connections on the back panel in normal operation). When the 'separate' button is pressed you gain the ability to use either the preamplifier or amplifier sections individually although this does make a compromise of using the single-ended connections (this will obviously not be balanced).

As it will be a fairly rare instance in which you will use the pre-out or main-in functionality it was a reasonable design choice to make compromises in the implementation of this feature (were it done to reference level quality with balanced in and out there would be a substantial amount of additional expense and these larger connectors would take up valuable real-estate on the back panel of the unit, all for a feature that is quite rarely utilized)".

The above answers my question about my Luxman 590ax being balanced. A loaner Bricasti M1 DAC is expected next Wednesday. The question is how will my Ayre QB-9 DSD DAC compare to the Bricasti M1 DAC. I will take the advice above and listen using only one interconnect cable connected at a time (XLR balanced for integrated amplifier and RCA unbalanced for M1 DAC volume controls). This is probably the safest approach.