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
All things equal I wouldn’t be planning to roll tubes on a new pre until you’ve listened to it and after a reasonable run-in period. Congrats on the new Backert!
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 believe this preamp uses 12AU7's. Do you know how many and is there a phono stage?

Amperex and Telefunken fit your requirements. Amperex Bugle Boys have deep 3D imaging, they're transparent with a liquid midrange Can be too extended on top in some systems. Older Amperex Command Series are more refined with the same qualities.
Telefunken is a revealing and dynamic tube with excellent 3D sonics. Mids are more upfront. But, they are costly.
Cifte, made by Mazda, has the same attributes as the Amperex Bugle Boys.
A best buy tube is the RCA Cleartop, neutral to warm with extension and air on top.

Read about tube types at

Brent Jessee is one of the best dealers and his website is most informative. He also does exchanges on tubes. Upscale does not.

I believe this preamp uses 12AU7's. Do you know how many and is there a phono stage?

Yes, it's 2 12AU7's, Mullard reissues from Russia. 

Thanks for the suggestions! I will take @three_easy_payments' advice and live with the Mullards for a couple weeks then possibly check out the Bugle Boys or possibly another pair of Ciftes. 
My faves for my Backert.... a pair of CBS 5814a. Just a well balanced sound across the range, but with a lively presentation. I tried a bunch of 12au7s, but always come back to these!
My faves for my Backert.... a pair of CBS 5814a. Just a well balanced sound across the range, but with a lively presentation. I tried a bunch of 12au7s, but always come back to these!
Thanks - I'll be checking those out too.

What Backert do you have? What does the rest of your system look like? Thanks!
I have the Rhumba 1.2, with upgraded output caps (a pair of Audyn True Copper Max), and an upgraded SR Blue fuse.  Great preamp; responds very well to tube rolling!

Check my system here on Audiogon... a lot easier than trying to describe. Pics are outdated, but the equipment listing is current.
@1markr wow, that is some impressive gear, I bet it sounds awesome. 

I just got my FedEx alert that the preamp has delivered at home... now just 8 more hours until I can get home and start working with it!

What difference did you notice with the SR Blue fuse? Have you found an improvement with an upgraded power cable? 

Thanks @jsqt!

Christmas in August! Love it! Have fun with your new toy!

Adding the SR Blue fuse was like a power cord upgrade from stock. Sounds cleaner, a little more open, a little more detail, but not because of  added brightness. Not a massive difference, but IMO worth the cost of upgrade.  The Rhumba definitely responds to power cords, but interestingly enough, it likes my homemade Oyaide power cord I made vs. more expensive ones I have from Audience, Verastarr, and others... 
The Backert is getting its first workout tonight. I'm not ready to make any gushing endorsements just yet but I am very impressed, particularly with the imaging and separation. I've noticed it's a little "soft" sounding - not syrupy or bloated or muffled, just a little polite, particularly on the bottom end. I suspect it may be the Mullards.
Call Andy at Vintage Tube Services and tell him your gear and what sort of sound you are looking for and see what he says. Something as simple and reasonable as a pair of RCA Cleartops or Raytheon Black Plates like the ones used by Baldwin and Conn might get you where you want to go without spending a fortune.  But I wouldn't do anything until you get about 150 hours on it.  

I find most tube gear is soft on the bottom end before running in ~80 hrs.  At that point the bass tends to tighten up in my experience.

I've noticed it's a little "soft" sounding - not syrupy or bloated or muffled, just a little polite, particularly on the bottom end.
Thanks everyone... so it seems like there is a fair amount of burn in time required for these caps then. This could explain why I was a little surprised by what I was hearing with the "softness" in the bass, versus so many of the online reviews and marketing material that say if anything the bass is a standout feature of these preamps.
Hi jsqt,
I upgraded from the Rhumba 1.2 to the 1.3 Extreme a few months back and happier I could not be. With both of these units I saw a marked improvement in sound after just 30 or so hours with the stock tubes. Andy Tebbe at Backert mentioned it would continue to improve (and I believe it has) but around the 30 hour mark is where I saw the most dramatic change. In regards to the bass, tubes can definitely influence that but I would be patient and let it play out. My 1.3 Extreme had plenty out of the box with the stock Mullards. In terms of tubes, I have tried a bunch, most NOS including Raytheon, RCA, CBS, Mazda, Tesla, Mullards, Amperex and I am sure there are a few others. All of these were rolled in my 1.2. As @jackd mentioned, the Raytheons and RCAs are fine tubes if you happen upon some good ones and they can be had at very reasonable prices. I ran a pair of Raytheon triple mica's before I splurged on a set of early 60's Bugle Boys which were my favorites until I tried a pair of late 50's Amperex 7316s which are the bomb in my setup. Personally I would heed the advice given earlier, take your time and enjoy the ride. Everyone's system, room and preferences are different so what works for one person may not work for another. I think finding a good source for tubes is can try ebay but that is a real crapshoot and you need to read the fine print. Personally I have had great luck with Brent Jesse and I am sure other dealers mentioned are also very good. Congratulations on the new acquisition and good luck on your journey! 
After a full day of tweaking and experimenting I can say I am very happy with the Rhumba Extreme!

Andy at Backert Labs was a great help throughout the day yesterday with further recommendations to my setup to get the best sound out of the preamp in my system. 

Here are a few observations I wrote up about the process & end results. 

I am plugging the Qutest directly into the REC OUT, which bypasses Inputs 1-4, since the Qutest is my only source. It did help with cleaning up a bit of the softness and restoring some snap and detail to the sound.

After initial setup on the glass top of my BDI Corridor Andy mentioned  that glass tops were not recommended for placement.

The BLRE went on a wooden shelf in the cabinet and the bass did focus a bit more and overall sound was cleaner and smoother. HOWEVER, because I have my Orbi satellite and Hue Bridge close to that shelf, I noticed some motorboating (digital cycling noise) in the background.

So I stole my wife's cutting board and using IsoAcoustic Oreas I replaced the BLRE on the top of the cabinet. This did result in a massive improvement in the overall sound.

I also eliminated the high level speaker wire connection from my MQ-88uSE to the JL Audio eSub and went directly from the OUT 2 of the preamp into the sub.

This restored a great deal of balance to the bottom end. I also did some further experimenting with the crossover and phase settings of the eSub, moving the crossover from 70Hz down to 60Hz. The result was a much better blend with the La Scala IIs and eliminated some directionality I hadn't noticed before.

All of these tweaks got me to the point where I no longer feel the need to swap the L509X back in to compare - currently I have solid, well-controlled bass with presence and heft, better transients and cleaner background.

This combined with the strengths of the BLRE over the 509X (massive soundstage with pinpoint placement accuracy, well-defined space around the notes, more musical unspooling of the music/greater liquidity) have me at a place where I am pretty confident I'll be able to let the 509X go to a new home, and explore further gains through tube rolling with the Rhumba Extreme.

Fit and finish of the Rhumba Extreme is top-notch. It's not an exceptionally heavy unit, but it is a solid, attractive, exquisitely machined piece. The toggles are satisfying to flip around and the remote is a heavy piece of jewelry - the best remote I've ever owned from any component. I'm really glad I was able to restore placement on the top of the cabinet with the wood cutting board because this is not a component you want to hide away in a cabinet.

The final piece of the puzzle was the delivery of a new Hugo M Scaler late in the afternoon.

Although not related to the Rhumba Extreme, the gains are jaw-dropping when feeding the Qutest dual BNC inputs at full resolution. Suddenly all boundaries between the listener and the music disappear. It's like a portal has opened to the soundstage; it's almost unreal how much of an improvement it makes. It does, on some recordings - particularly with male vocals - add a bit of thinness to the sound I've experienced when upsampling from Roon in the past.

But I chalk that up to the limitations of the Qutest more than anything else, and I can definitely see a DAVE upgrade in the next year.

A note about the M Scaler and Rhumba Extreme - I should clarify that I'm not intending to project the gains of the M Scaler to the Rhumba Extreme.

When putting the M Scaler in bypass mode, listening to the non-upscaled audio through the system is still remarkably transparent, engaging, and dynamic.

All-in-all this is very close to end-game for me.

In fact if it wasn't for the tiniest bit of thinness in male vocals when upscaling to the Qutest, I'd probably not even think about further upgrading to the DAVE, but knowing me, I'll always be nagged that there's "one last step" to achieve.

I'm excited about doing some tube rolling with the Rhumba Extreme, and will definitely explore some of the recco's mentioned in this thread.

@jsqt,Very recently I found that I prefer the sound of the Rhumba with the orange rings OFF the tubes. It felt like the sound stage widened and clarity improved so much. I don't think the O-rings that are on the tubes that the Rhumba comes up with, helps it's sound. Of course, YMMV.BTW, I use Genalex Gold Lion 12AU7 with my Rhumba 1.3. This is a fantastic preamp. The reason for my findings was that the preamp is so precise that it is scary sometimes. I played a Patricia Barber CD where the vocals were slightly to the left. And immediately after this I played Neil Diamond's 12 album, Song 2 (Hell Yeah). Here too the vocals are on left. I was damn sure that the tube on the right is dying and hence the tilt. So I shut down the system and changed the tube positions. While doing that I removed the orange o-ring and played the songs again. The sound stage did not tilt right, as I had expected. After playing another song I realized that the system was really doing pin-point positioning with improved clarity, depth, wide-stage and impact. Super happy to have made the accidental discovery of NOT using those orange rings on the tubes.

Thanks for the heads up @milpai  I will have to do some experimenting with that myself. 

I have swapped the stock Mullards for a matched pair of Mazda Cifte 12AU7, after being so impressed with the Cifte's in my Rogue CM2. I have found the Ciftes seem to really magnify everything the Rhumba Extreme does well - they are a good compliment to the airy top end, pinpoint accurate stereo field, and authoritative bottom end without changing the sonic character of the sound in any way. 

I will pull off the tube rings this weekend and see what kind of difference it makes. I'm curious to compare; the preamp is already using terracones, sitting on a butcher board, which is sitting on 3 IsoAcoustic Indigo Oreas so I wonder what difference the stabilizers are even making at this point. 
Would like to hear your experience after removing the rings.
Please do let me know. 
So I liked the sound without the O-rings for 2-3 days after which it started sounding fatiguing. I started looking into dampers that would not "constraint" my music. I came across Herbie's tube dampers. I was recommended the Ultrasonic SS tube dampers. I got them earlier this week and installed them right away. Well, I am pretty happy with how they got rid of the noise that I initially mistook as "open sound". The music and instruments sounds natural with these dampers. Love to get that musicality back in to my system.
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.
NOS medical grade Amperex from Brent Jesse.Not cheap but wonderful sounding.
@milpai that is interesting to hear, thanks for the follow up. I did remove the o rings on my Cifte’s for a couple of days and I could not really detect a difference to be honest. I do have mine on a slab of wood that is also sitting on 3 IsoAcoustic Oreas, so that combined with the terracones on the unit itself may make it less susceptible to noise? Or the Mazda Cifte could be less microphonic than the Gold Lions. I replaced the o rings and have left everything as-is.
A little over a month in and it is still sounding amazing with the MQ-88uSE. I did replace both power cords on the Rhumba Extreme and MQ-88uSE with Transparent High Performance PCs and I have noticed an improvement in detail, which I attribute to a lower noise floor overall in the system. 
I’m currently awaiting the Hugo TT2 to replace my Chord Qutest DAC; along with the M Scaler, I believe the Hugo TT2 will likely be end-game on the system. I couldn’t justify the expense of the DAVE and I have read rave reviews of the TT2/M Scaler combo (together surpassing the sound of the standalone $12K DAVE).
Recently changed to a Psvane 12AU7 and love this tube over the Gold Lions. These are much more open, slightly less warm, but tons of details and superbly balanced. I got mine from Viva tubes in MA.

My dealer tells me that using tube adapters and 12SN7’s sound better than 12AU7’s. Has anyone tried this?

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.

@hifiman5 and @milpai thanks for the updates! I'm glad to see this thread continue, as I think there are a lot of Rhythms and Rhumbas out there but they don't get talked about much in the forums. I've done a 12AU7 inventory recently given the events in Eastern Europe and I have 4 Mazda Cifte's, 2 Genalex, 2 Russian Mullards, and 4 Brimar CV004s, so I should be in pretty good shape with the tubes I have now to weather any shortages. This weekend I'm experimenting with swapping the Brimar CV4003's back into the Rhythm and this time without O-rings. @hifiman5 were you ever curious about Bob's Xphono phono pre? I have just gotten back into vinyl since January and I have a Parasound JC3+ on order to complement my current SL-1200MK2 and my future Pure Fidelity Harmony. The Luxman and Xphono both looked really good but a little over my budget for where I'm at with vinyl these days. However since Oreas were mentioned somewhere in this thread, here's something I found - I am using an extra glass panel from my Naim Fraim to support the SL-1200Mk2, and I experimented with supporting it by either 3 Stillpoint Ultra SS vs 3 Isoacoustic Orea Indigos. The Oreas definitely seemed more natural and relaxed than the Stillpoints. Stillpoints seemed to tighten up the bass to a fault - I enjoy a bit of that analog fat bottom end (think a Fender P Bass and Ampeg cabinet) and the Oreas seemed to do a better job of tightening up the space between the notes while maintaining the natural presentation and flow of the music. 

@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. 

@jsqt ,

Since you have such a nice inventory of the 12AU7s, I would like your thoughts IF you get a chance to listen to the Psvane's new ART series. They have bowled me over. The work "mesmerizing" comes to my mind.

As this thread is about tube makes and models that do especially well in Backert preamps, I'm going to reiterate my recommendation of the--admittedly rare and costly--Amperex 7316.  This is what Brent Jessee has to say about them.

Simply an amazing tube. Amazing both because it sounds so incredibly good, and amazing how rare it is today. The 7316 was made by Amperex in Holland, I have never seen this in any other brand, nor have I seen it made by Amperex North America. It is a medical grade/aircraft equipment grade super low noise tube, not sold to the general public. It is Amperex's answer to the ECC802S produced by Telefunken, and the 10M series made by Mullard. Most have the Bugle Boy on the label, although I have seen plain Amperex labels, and OEM labels such as Beckman Instruments. The 1950s vintage with the long plates and D-getters are to die for. They are among the best sounding and rarest 12AU7 around today. Don't miss the 1960s halo getter version of this tube, as well. They sound nearly as good as the D-getters and are usually half the price. Very few dealers ever have the 7316 of either type in stock, well worth seeking out and worth the higher price. We try to keep a few of each type in stock, but it is not easy. Better buy them when you can find them!

Unfortunately, it's all true.

@milpai I’ve just started my tube rolling journey with my Rhumba Extreme 1.3, and my first change was to the Psvane Art Series. Holy mother of tubes! After only 9 hours on them, they are already a giant leap ahead of the stock Mullard tubes. Thanks for rec! After the first hour, they excelled in all areas except bass extension and the vocals were still somewhat thin. But now, the sub-bass region is gaining some weight and overall, in the Extreme 1.3, they make my system sound really incredible. I’m looking forward to the other tubes that are en route to me, but i think these will be hard to beat... I suspect even by the NOS stuff.

Edit:  By the way, I'm not using any damper rings on the tubes.  The Backert pre is on Townshend isolation pods and the cables going to it are also isolated from vibrations.

I was talking to a long-time audiophile on the phone a couple days ago and he said that tubes don't make that much of a difference in sound compared to fuses.  This is just two 12AU7 tubes on a linestage, and the difference is very profound.  I'm more doubtful than ever about his claim


Good to know that the Psvane ART tubes worked for you. Hope you enjoy them for a long time. I have no experience with tubes and hence in no position to comment.

I will endorse the latest iteration of the Psvane tubes as the best new-production 12AU7's to use in the Backert.  In my experience they are only surpassed by the NOS Amperexes that I mentioned above, which are very hard to find and very expensive when you do.

@twoleftears ,

I did not know that you too tried them. Good to know. It was the Art series…..right?

Yes, the 12AU7-S ART's surpass new-production Mullards (supplied by Backert as standard) and Genelex Gold Lions.  I don't know of any other new-production 12AU7's that would be contenders for the crown.

@oddiofyl : Would you please explain in technical terms why you say "With respect to 12sn7 adapter,  I would personally only use 12au7 and / or their exact pin out equivalent,  especially on a $7500 preamp". I find many of your posts informative and helpful. Jeff

I just stick with the exact tube type the component came with or the mfg. says is safe.    

The are not the same bias.   There is no direct sub for a 12sn7 according to my Hickok manuals.  There are many great 12au7 still out there as NOS and several new options.  It doesn't even make sense .

Personally I treat this book and it's addendum like they are Gospel.   If it's not listed in that middle column I would advise against,  do so at your own peril.   I used that guide and other tester documentation long before I got a tube tester.   

I've never had a component damaged by a tube and I think it's because I never took another enthusiast's word for it that something was a good substitute. 


On that particular list the middle column should say Acceptable Sub , not direct sub.    Direct sub narrows it down to 5418 6189.  Those are the same tube but ruggedized 

I ran into this when searching for an E180F tube.   Many varieties,  more than you would imagine actually and I checked with my Amp's mfg. and he said 7788 was fine .   So I always do that.   I reached out to Mike at Quicksilver a while back just to check if 5751 were OK and he said no problem.  So that's really who you should be asking, not the dealer.

I almost bought a Rhumba , looks like a fine pre.  I actually called them in my last search for a pre.  They picked up right away and answered my questions honestly I believe.   They seem like a good outfit.  I know some of their designs auto bias but still, do you really want to be using adapters in such a nice pre?   I wouldn't , that's all.   Some of the best tubes are the RCA 12au7 if you can get them from a reliable source .   I picked up a pair from Tube Museum out of NY and they test better than new super high emissions.    I paid $300 for the pair and unfortunately sold my preamp before I ever got to use them.   Those are the kind of 12au7 that should be going in such a fine music machine.   I always feed my babies the best !