What Preamp Configuration Should Sound Better (Passive Versus Active)?

[EddNog]

I've got a new Schiit Saga 2 preamp coming in. It has only single-ended inputs, but for outputs, it has fully differential balanced XLR as well as single-ended RCA outputs.

The Balanced output only works in Active modes. The Single-ended output works in Active as well as Passive modes--there is only one single-ended output.

My DAC (Topping D90 III Discrete) is rated ~131dB SNR in balanced output mode and ~127dB SNR in single-ended output mode.

The Saga 2 is rated ~124dB SNR in Low Gain Active mode. Passive mode would yield unlimited SNR.

I have to hook up a pair of monoblocs to drive my speakers but also a subwoofer. The monoblocs (Topping B100) have SNR of 149dB with single-ended input and 151dB with balanced input.

-Ed

 

[Blumlein 88]

If you are using monoblocks and they aren't close together I'd use active mode so there won't be any high frequency roll off. Any difference of a few db in SNR will be meaningless with the gear you have.

Assuming the pre outputs RCA and balanced work at the same time, I'd probably use the balanced to the main amps and RCA to the subs. Choice #1 in the poll.

 

[EddNog]

If you are using monoblocks and they aren't close together I'd use active mode so there won't be any high frequency roll off. Any difference of a few db in SNR will be meaningless with the gear you have.

Assuming the pre outputs RCA and balanced work at the same time, I'd probably use the balanced to the main amps and RCA to the subs. Choice #1 in the poll.

Just curious: what would cause high frequency roll-off with the passive configuration? The RCA y-splitters?

The monoblocs are about 3 feet apart, center to center, with the DAC and preamp sitting between them.

-Ed

 

[Blumlein 88]

Just curious: what would cause high frequency roll-off with the passive configuration? The RCA y-splitters?

The monoblocs are about 3 feet apart, center to center, with the DAC and preamp sitting between them.

-Ed

The passive configuration will have a high output impedance. This will interact with the cable capacitance to cause a high frequency roll off of 6 db per octave. The frequency at which this occurs will depend upon cable length and cable capacitance per foot. At only 3 feet of interconnect length it won't suffer a roll off until the ultrasonic region with normal interconnect cables. So it would not be a problem.

If you were to use the wrong cable and run the cable 10 or 20 feet then it could dull the high frequencies.

 

[Sokel]

Passive attenuation has to have impedance in mind.
Go active and balanced all the way if you can.
Such a chain mixing and matching components has the potential to destroy any noise figure if it will introduce grounds loop at some point.

Ah,@Blumlein 88 got me by seconds

 

[Waxx]

with the gear you've got active is the best choice i think. Passive preamps can be good in the right setup, but mostly they are not fit. I ran a passive preamp for years in a certain setup where it worked very well, but then i changed the setup, and the variable output impendance of the passive preamp became a problem (even if i just needed unity gain) so i went active again. Modern design amps expect a active preamp with a fixed output impendance to work well. If you only need unity gain (no gain) a passive preamp with a buffer is enough, but the buffer is needed to make the impendance fixed so the power amp get the input that it wants. Active preamp are mostly not because the gainstage, but because the buffer important.

If you use passive preamps, always use very short cables (i used 0.5m ones) to connect to the amp or it may indeed become a low pass filter.