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Multiple Preamps in chain?


New Member
Nov 29, 2021
I have a Topping Pre90+Ext90 connected to class d power via XLR and a sub via RCA (using the XLR+RCA out on the Pre90). This is quite good really, because it allows me to effectively switch off the sub by switching to XLR out, with just a slight volume bump.

Sometimes, however, I get all romantic/nostalgic and want some tubes in the mix. I have a nice tube preamp which has XLR out, but I'm not sure how I can have it setup without needing to mess around with connections (usually only get the time once a week and it's only a 2 minute faff, but still). In case it matters, it's a Woo Audio WA22.

The obvious thing would be a passive switcher between both the preamps and the power amp - but how does that work with the sub? Can I use a passive XLR switcher and split the XLR output into both XLR and RCA for the amp an the sub? I think not.

The alternative I think I want, but aren't sure about, is to have the tube preamp input into the Pre90? It has an output impedance of <50O but on this forum we've previously discussed that the Pre90 isn't so hot with it's input impedence. What are the ups and downs here?

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