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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
atmasphere's avatar
atmasphere
11,834 posts
 
One exception to atmasphere's comment directly above is a pre-amp using a transformer to create the balanced output(s). That's exactly how Tim de Paravicini does it in his EAR-Yoshino pre's. There is an EAR 868PL (phono and line stages) listed on Audiogon at the moment, and it has two pair of both XLR and RCA outputs.
Actually if a transformer is used, it has to have a switch so one side of its secondary can be tied to ground in case the output is to be single-ended. So a switch is required.

The only way to do balanced otherwise using a transformer and no switch is a a transformer with a center-tap. But this would sacrifice a lot of common mode rejection performance since the center tap can't be exactly placed at the center of the transformer windings. which is why no-one does it that way (as far as I know).
bdp24's avatar
bdp24
9,816 posts
 
Hmm Ralph, that's interesting. The EAR pre's don't have an XLR/s-e switch, yet have multiples of both outputs (double of each on the 868). I'll have to look for a schematic to see what's what.
almarg's avatar
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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


atmasphere's avatar
atmasphere
11,834 posts
 
@bdp24 Well there you have it. A transformer with a dual secondary so that the single-ended and balanced connections can't mix. The upside is that both connections can be supported at once; the downside is there is additional capacitance due to the presence of the second output winding. This probably does not affect bandwidth much on account of the transformer being fairly low power. Note though that it is designed to support the low impedance aspect of the balanced standard; the 1K resistors @almarg mentioned are there to load the transformers to prevent ringing if used with a load of higher input impedance.
bdp24's avatar
bdp24
9,816 posts
 

Great, thanks fellas. Isn’t education and knowledge a wonderful thing? ;-) This kind of information was regularly included in reviews in Audio Magazine (except those of TAS alumni Anthony Cordesman), and Stereophile when Gordon Holt and Dick Olsher were doing them. Harry Pearson and his pals at TAS had no technical education or knowledge, and set in motion the subjective-only style (no bench tests, no circuit descriptions) of hi-fi reviewing.

At one of his S. California instore appearances in the 1980’s (to introduce a new model), Bill Johnson told the assemble crowd a story about sending Pearson a new ARC pre-amp (I don’t recall which model). Bill soon thereafter received a call from Pearson, who told him it was defective. He had Pearson send it back, and of course tested it when it arrived back in Minnesota, where the pre-amp worked fine.

Johnson asked Pearson a series of questions to get to the bottom of the problem, and soon had his answer: Pearson had installed shorting plugs into the pre-amp’s unused output jacks! He knew enough to know that shorting plugs can prevent noise getting into unused input jacks, but not enough to know that you shouldn’t short output jacks. Golden ears, perhaps, but is that all that is required to be a professional hi-fi reviewer?

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