Tube Rolling Advice for the Backert Labs Rhumba Extreme?

Tomorrow I have a Backert Labs Rhumba Extreme 1.2 being delivered, which has been upgraded by Backert to 1.3 specs. It will be driving the Luxman MQ-88uSE and the front end is a Qutest with M Scaler (Innuos Zen MK III server/streamer). Speakers are La Scala IIs, placed about 15' apart in the corners at a 45º angle. Soundstage is excellent and expansive with remarkable placement of instruments across the sound field.

If all goes well it will be replacing my L-509X, which is currently only being used as a preamp for the MQ-88uSE, so it’s being underserved in my system and will need to find a better home.

I am interested in any advice about tube rolling with the Backert Labs pres. With the Chord digital front end, I am getting a very layered, dimensional, detailed sound and thanks to the Qutest filters I’m able to adjust filters to best match the amplification. The MQ-88uSE has a gorgeous, full, warm sound and right now the 509X’s solid state pre is giving a nice sharp, detailed, and dynamic profile to sharpen up the tube sound a bit.

I don’t want a syrupy or bloated tube sound, more airy and detailed on the top with holographic imaging with solid heft on the bottom end. I’ve replaced the preamp tube in my Cronos Magnum II with a Cifte and was really happy with the impact on the sound.

The Backert comes stock with new Mullards, which I expect may have a slightly warmer sound than what I’m chasing.

Any advice?

128x128Ag insider logo xs@2xjsqt

My regular Rhumba 1.3 came with the new-production Mullards.  I got some new-production Genelex Gold Lions from Jim McShane which I liked a little better.  Then some older Blackburn Mullards from Brent Jessee which honestly didn't really seem to improve on the Gold Lions.  But now I have some fancy Amperex 7316's installed, and they are the best yet.  Can't imagine rolling again any time soon.  Full rich, sound.  I would have tried the new-production Psvanes, but Amperex is giving me everything I look for.

With respect to 12sn7 adapter,  I would personally only use 12au7 and / or their exact pin out equivalent,  especially on a $7500 preamp

This thread has been resurrected over the weekend so as the OP I figured I’d chime in with my progress over the past 3 years. I have owned a Rhythm 1.3 now since last August and it was a worthwhile upgrade to the Rhumba. I am no longer using the Luxman tube amp, however; the Rhythm is paired with a Luxman M900u and it sounds spectacular. Regarding tubes, the new Rhythm came with a pair of Gold Lions, I believe, which I then swapped out with new Mullards and also a pair of Brimar CV4003s, and believe it or not I am settled back on the Mazda Ciftes. Not sure what it is about those tubes but I hope they last for a long, long time because I don’t think they are available at Upscale anymore. 

@jsqt  You are indeed fortunate to have a Backert preamp.  I have had the good fortune of knowing Bob for a couple decades, long before he made moves toward offering his own designs. Bob was known then for modifying preamps and to a lesser degree power amps.  Most of Bob's work back then was upgrading conrad johnson units.  He liked working on cj's like my PV12L because their was a lot of unused real estate inside those units so he could readily add his own proprietary circuits to improve their sound.  Bob has always embraced a "purist" philosophy with an emphasis on the power supply. (Greenforce)  Bob's circuits opened up the sound of cj's as cj gear is known to have a warm, rich sound.  Very listenable but would obscure fine details.  Bob's goal was, within my budget, to reveal all of the details in the music resulting in a more spacious soundstage when one is present in the recording.  A year ago I took my modified PV12L to Bob as the volume control and selector knobs were creating a scratchy sound as I used them.  Bob cleaned the knob contacts and then after asking him if there was any other circuit improvements he could install, he informed me that he could install a new gain stage dynamic linearity circuit that would be a significant step up. Done.

I wish I could hear my cj as it was before all of Bob's work and how it is now.  I am quite certain the openness and musical accuracy of the modified unit would be obvious and desirable over stock.

Back in 2019 in this thread, I mentioned my embrace of Herbie's Tenderfeet.  They are a nice improvement but once experiencing the musical clarity of the Isoacoustic Oreas, I now have every piece of kit sitting on them and the Tenderfeet are in the closet.

BTW...The Mazda CIFTE tubes really did sound good with Bob's circuits.  The pair I had just didn't last as long as I would have liked and have been using matched pairs of Gold Lions yielding fine, balanced sound.

PS  From everything I've heard about the Luxman M900u, I can imagine that it would mate well with the Backert pre.  I have a Luxman phono stage. Thank God there is a vinyl revival in progress!


I recently installed the Psvane ART series tubes and they seem to make music even better than the previous Psvane series. But the point is, this preamp is amazing and tube rolling adds more fun.