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?

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Showing 3 responses by hifiman5

Herbie's products are well designed and carefully implemented with materials that are musically friendly.  I have Herbie's Tenderfeet under every component in my system. SO musical.  Their decouplers are great for speakers and subwoofers.  With them in place the rest of the house isn't vibrating with the deep bass of many favorites...also the vibes aren't stressing the Tenderfeet.  Tuning a system is that last, best step in realizing a system's full potential.

@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!

@jsqt Interesting that you mentioned not using the damping rings when you install the Brimars. I just put a new matched pair of Gold Lions in my pre last night as the tubes had been in circuit for over two years. After having read others experience with and without dampers, I installed the new tubes without the dampers. I’m looking forward to listening this weekend. I mentioned the Oreas in my previous post and agree entirely with your assessment of their impact on the system’s sound. As far as phono preamps go, I have no doubt that the Backert is great but I love what my Luxman has done for the sound of vinyl in my system. The vinyl I have been receiving is really flat and quiet. Amazingly so.  I have so many silver and gold discs as well as a vinyl collection dating back to the 1970s that I plan to stay with hard media rather than adding download capabilities.