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Preamps with Dual XLR Outputs

I am looking for preamps with dual XLR outputs to drive 2 separate stereo amps which are connected to 2 different speakers sets. My understanding is the Mola Mola Makua w/DAC and streaming board that is ROON READY can do this. It costs $20K and is my leading contender for my next preamp + DAC + streamer. I am going to output the signal to a Benchmark AHB2 amp + KEF LS50 speakers for one path. The other path is Luxman m900u amp + Yamaha NS 5000 speakers. My understanding is that turning off one of the amps stops the preamp from using that signal path. Perfect. I have heard all the components except the Mola Mola Makua so I will likely do a home trial on that.

My question is what other brands have an analog preamp with dual XLR outputs to do what I describe above? The preamp does not need to support an internal DAC. I could go for an external DAC like a LUMIN X1 or Denafrips Terminator.

BTW - if the Mola Mola Makua or any other brand cannot support my use case (I have been told it can). I will buy 1 preamp, such as the Benchmark LA4 to go to the AHB2 + LS50 system and also buy a DAC, such as Lumin X1,  to go direct to the Luxman + Yamaha system. Both speakers will be in the same room.
yyzsantabarbara

Showing 3 responses by almarg

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almarg
9,670 posts
 
Ralph & Eric ( @atmasphere , @bdp24 ) I looked at a schematic of the EAR 864 preamp, which is included in the owner’s manual that can be found at hifiengine.com.

Its output coupling transformer has two separate secondary windings. One connects to pins 2 and 3 of its single (per channel) XLR output connector. One end of the other winding connects to the center pins of its two paralleled RCA output connectors (per channel) via a 100 ohm resistor, with the other end of that winding connected to circuit ground. Pin 1 of the XLR connector and the ground sleeves of the RCA connectors are connected to circuit ground. There is a 1K resistor across each of the two secondary windings.

So the use of two secondary windings explains why there is no XLR/RCA switch. Presumably the 868 is similar in that respect, and I’d imagine that these and perhaps other EAR designs are fairly unique in that respect.

Best regards,
-- Al


almarg's avatar
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almarg
9,670 posts
 
From the measurements section of Stereophile’s review of the BAT VK-51SE:

The balanced output impedance was twice that specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20Hz, due to the size of the output coupling capacitors.

Which means that this preamp is not compliant with the AES48 requirements Ralph has described. It also means that it would not be a good match for the 20K load it would see when connected to both amps, assuming (as is highly likely) that its two balanced outputs are driven by the same output stage.

Best regards,
-- Al

almarg's avatar
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almarg
9,670 posts
 
My understanding is that turning off one of the amps stops the preamp from using that signal path.

However it does not stop the preamp from being loaded by the combined input impedance of both amps, given that almost all preamps providing dual outputs drive both outputs from the same output stage.

Consequently I would rule out the Rogue preamp that was suggested. The balanced input impedance of your Benchmark amp is 50K; the balanced input impedance of the Luxman amp is 34K. Assuming those numbers apply when each amp is powered down (which is not always the case) their combined impedance is (50 x 34)/(50 + 34) = 20K.

Stereophile measured the balanced output impedance of the Rogue RP-7 as rising from extremely low values at mid and high frequencies to a very high 5.64K at 20 Hz. Not a good match, given the wide variation of output impedance coupled with the ratio of amp input impedance to preamp output impedance of less than 4:1 at 20 Hz.

The Makua, Ayre, and W4S preamps that have been suggested should be ok in that respect. Not sure about the EAR.

Good luck. Regards,
-- Al


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