The hum you read about was not inherent in the preamp, but was caused by the higher output impedance of the preamp combined with poor interconnect cable layout between the preamp and amp. Once the guy on the stevehoffman site got the layout right, the hum was gone.
While it does have an XLR output, it does not support the balanced standard. If it did, the hum with the interconnect cable layout would not have been an issue.
I know the Backerts having had the good fortune to visit their home a few times to have my gear modified. All proprietary designs as Bob worked on cj preamps for many years and developed his own board to open up the sound and enhance the dynamic response of the stock unit. Like all of the finest designers of audio gear, his work emphasized maximizing the design of the power supply circuitry. He holds patents on his power supply designs prior to launching Backert Labs.
Bob is one of the finest people I have ever associated with in my 40+ years in audio.
Sorry I can't relate personal experience with the Rhumba but I can unconditionally attest to the character and talents of the designer.
@david_ten , will try to reach out and discuss with them.
@atmasphere , I wanted to make sure that it was not really a generic issue. Backert Labs do mention that all their preamps are single ended, with XLR out. I don't think, for that matter, that my Parasound A21 is fully balanced. But when it is connected to the preamp via XLR, it sounds amazing.
@1markr ,You have a beautiful setup. I see that that you even have tube power amps. Did you compare the Coincident Line stage with Backert? Good to know that you don't have issues with the Rhumba. Wonder why not many folks are using it. Does your Coincident amp have XLR in? Did you get a chance to compare the Backer Lab connected to the amp via XLR Vs RCA?
@hifiman5 ,Thank You for the reference.
@milpai thanks for the system compliment! At the time I was looking for a preamp, I did want to try a Statement preamp, but none were popping up, so I decided to buy the Rhumba from a dealer instead (something to be said about a 30 audition policy!).
Anyways, I loved what I was hearing, and obviously it didn't go back. Haven't heard the Coincident Statement, unfortunately.
The amps don't have XLR inputs, so I do not use the balanced input or output of the Backert.
As someone in the same boat as you -- solid state guy looking to add a tubed pre for the first time -- thought I'd chime in FWIW. My goal is to introduce some of that tube magic into my system with as little or no sense of a loss of transparency or bass control. The Rhumba is also one of the top three on my list, and given what I've read it's really hard to see going wrong with it. But the other two on my list are Don Sach's SP14 pre and Ralph's MP3. The fact that the MP3 does away with coupling capacitors intrigues given my concern about compromised bass. BTW, there's a very nice, almost new MP3 available now on US Audio Mart that might very well be on its way to me now if I had the scratch.
Anyway, since we seem to be going down the same road I just thought I'd share what I've been looking at. Best of luck!
You are welcome. Good to know that you liked the Rhumba so much, as to not return it.
You are more than welcome to add to this thread. While I blame Ralph for getting me to start looking into tubes, I want to "wet my feet" first. The MP3 may be really good, but is currently out of my price range and also comfort (no. of tubes) range. Don Sach's SP14 looks good, but not on my list. Thank You for sharing.
I have decided to reach out to Backert Labs with my specific questions. But one point on their site that concerns me is - " A side-effect of using a single gain stage is that our models invert phase.". The link to that page is missing.
HI Milpai - I too know Bob for many years and have found him to be a gentleman of the utmost character. His preamps are wonderful and an absolute bargain in terms of what they sound like and how they are built. Phase inversion is not a problem- to compensate, you just switch plus and minus at the speaker input to revert to being "phase correct" for the purists, although many recording engineers do not pay attention to absolute phase. Good Luck!
@jwpstayman , thanks for pointing that. But I managed to talk to Andy at Backert Labs and he answered all my questions. Looks like the new Rhumbas do not do phase inversion issue, since a transformer that they use inside does it (not sure if I put it the right way, as Andy explained).
I am impressed how much time Andy took to answer my specific questions related to hum, phase inversions, tube life, volume control, etc. Andy also told mentioned about a very good upgrade path for existing users. Besides the Parasound JC2 and Jeff Rowland Capri S2, I think I will seriously consider the Rhumba as a preamp upgrade. Frankly this is probably my number one preference for now.
The MP3 may be really good, but is currently out of my price range and also comfort (no. of tubes) range.@milpai The Rhumba is a line stage. If you get the MP-3 as a line stage, it only has 4 tubes. The remaining tubes you are probably thinking about are for the optional phono section. The MP-3 has a polarity inversion switch.
Since I know Andy really well, and sorta know Ralph as a former customer, I won't go on in any detail here, but wanted to point out that it's pretty cool that both the Backert & Atma-Sphere gear is voiced by performing (in Andy's case -- professional) musicians. That may not matter to you, but I think it's cool and perhaps relevant. Cheers,
@sbank Thanks- I often wonder what people mean when they use the word 'voice' in that manner. I've often interpreted as some sort of tonality? - but it could mean something else. FWIW we don't do anything to compensate our circuits for bandwidth, and while we do listen to the gear of course, we don't do that until we've optimized for least distortion and maximum headroom.
@atmasphere Ralph, when I said "voice" I certainly wasn't implying that you are doing anything to taint the signal, but rather that when listening and developing designs your judgements are coming from a musician's perspective. For example, trying different types of wire and making choices of what sounds most realistic.
I have heard stories from Andy at Backert such as "we spent the day listening to impact of ten different capacitors".
Glad you guys do that so we can enjoy the fruits of your labor. Cheers,
With the original Rhumba 1.1 you needed to reverse the speaker polarity and the XLR were not truly balanced. The current model, Rhumba 1.2, both of these design issues have been changed. With the Rhumba 1.2 you do not need to reverse the polarity at your speakers and the XLR line in is now balanced. The Rhumba's sound is very transparent, detailed and dynamic. You can fine tune the final sound of your system by tube rolling, which is a lot of fun. It's ability to create a wide and deep sound stage is second to none. I really am 100% satisfied with the Rhumba 1.2 preamplifier. It is a line stage, there is no phone stage. The unit does have a HT pass through, which is a great feature for people who plan on using this in their multi-channel set up, and the preamplifier has a second pair of line outs so you could run dual subs along with your main speakers if you choose to. I cannot say enough positives about the preamplifier.
Yes, I spoke to Andy about the polarity and he did mention that it was correct polarity with the new models. But he did not mention anything about the "true balanced" design for XLR. In fact, if you go to the following page, it mentions " The Rhumba has 9dB of gain (we can adjust this to suit your specific system) and is single-ended".
So, I am not sure the difference between "Balanced" Vs "true Balanced" that Ralph often refers to.
I am hoping that the Rhumba is much more transparent than my TVC. I am assuming that, it being active, it would naturally sound more dynamic. I do not have a turntable, so phono stage does not matter. But Andy mention that they are coming up with a phono stage later. HT pass through - again it is of no use to me. I would rather have that converted to another XLR IN, if they do it.
Thank You for sharing your positive experiences with this preamp. I found the following instragram message from Backert Labs that is interesting:
From my conversation with Andy, in which I did specifically inquire on this issue, his response was that the XLR is a "true" balanced connection with the 1.2, if that helps. In my opinion, if you are using quality interconnects and your run is not abnormally long, a typical meter interconnect, then a balanced or unbalanced connection is not going to play a big difference in sound quality. What is nice about the balanced connection is how positive the connection is, it really snaps into place.
So, I am not sure the difference between "Balanced" Vs "true Balanced" that Ralph often refers to.'True balanced' is not a thing I say so much as I harp about supporting the balanced standard. The circuit does not have to be balanced to do that properly- it can be single-ended as the Rhumba is, and use an output transformer as the Rhumba does. Transformers can drive balanced lines quite well.
In my opinion, if you are using quality interconnects and your run is not abnormally long, a typical meter interconnect, then a balanced or unbalanced connection is not going to play a big difference in sound quality.The whole point of balanced line is that the interconnects don't have to be expensive (which might be the same or not as 'quality'). What this means is that you have the same benefit if the cable is 6" or 60 feet, which is to say it will sound right and cheap cables should sound the same as expensive ones, regardless of length.
Tim de Paravacini uses transformers to provide the two pair of balanced/XLR outputs on his EAR-Yoshino 868L line stage (two pair of unbalanced/RCA outputs as well). Only two 7DJ8 tubes in the pre amp. Tim does lots of work in the pro sector (Pink Floyd’s studio in London, the tube electronics in the recorder and mics Kavi Alexander uses to make his Water Lily recordings, amongst the highest fidelity in the history of recording. Ry Cooder’s favorite label!), and is well aware of and adheres to the standard to which Atmasphere refers, unlike many designers of consumer gear (excluding Ralph, of course ;-).
as a Backert Labs Rhythm user myself, i can highly recommend their fantastic linestage. i upgraded from Rhumba to Rhythm . From experience, the simpler the design the less problem you encounter from it, and the more easier to solve if any. It also doesn't necessarily mean a balanced connection or a fully balanced design circuit (i.e MP-3) will give you lower noise or have any advantage over single ended design. Fully balance design circuit will also susceptible to hum problems too.
i'm being a BL user for 2.5 years and quite familiar with their pre. so if you need any advice about Backert Labs pre, feel free to ask .
One question - when I think about tubes and the demos at audio shows it was always some vocals or smokey jazz or classical. But I do occasionally listen (and I am not bashful about it) to Michael Jackson, George Michael, etc - so pop from 80s/90s. My kids do sometimes come into the room and listen to the current pop like Justin Beiber, Uncle Kracker, etc. How does this kind of music sound with tubes? With my TVC, it sounds pretty transparent and clean. Does tubes make this kind of music sound "slow and syrupy"? Will I have to keep switching between the tube preamp and the TVC to get best of both worlds? Mind you - I listen to female/male vocals, classic rock, jazz and classical 80-85% of the time.
It also doesn't necessarily mean a balanced connection or a fully balanced design circuit (i.e MP-3) will give you lower noise or have any advantage over single ended design. Fully balance design circuit will also susceptible to hum problems too.Just a correction here, since this statement is essentially false.
The advantage that balanced operation has is several- immunity to interconnect cables, and the system was also devised to prevent ground loop hum and it works quite well! "Fully balanced design circuit" (sic) is far less susceptible to hum problems- it is better able to reject noise in the power supply and far more able to reject hum from close by power transformers and the like. It is also possible to get lower noise, since if the balanced design is also differential, careful use of well-designed constant current sources will reduce noise while also increasing gain and reducing distortion.
The first bit: immunity to interconnect cables, is likely the most important aspect, since audiophiles are well-known to pay serious money for interconnect cables in search of the cable to rule them all. In effect, cables are the 'hidden cost' of operating single-ended preamps.
with due respect and i do mean it as your preamps are a true technological marvel, not to mention its excellent sonic that many people are enjoying the transparency and speed out of tubes in your pre.
however, my encounter with preamp MP-1 is otherwise. In exactly the same setting, all variables are fixed and nothing changed (ie. interconnects, power etc..), i get hum from MP-1 , but i don’t experience hum after i swap to single ended pre. At a friend place, the same MP-1 preamp function just as great.
i understand it could be something faulty (i’m unable to find the cause of it) at my place but i didn’t experience the benefit of balanced design preamp as compare to single ended pre at my place. so i came to understand that balanced equipment doesn’t guarantee a better sound, irregardless if the improvement in sonic is audible or not.
i don’t wish to risk a debate here and i’m only expressing my opinion with balanced designed vs single ended audio gear.
all the best,
And how does one acquire an immunity to interconnect cables? Is it from a consistent exposure to same that you build up a natural resistance to them? Sheeeesh!🤔😝Proper inoculation I guess.
however, my encounter with preamp MP-1 is otherwise. In exactly the same setting, all variables are fixed and nothing changed (ie. interconnects, power etc..), i get hum from MP-1 , but i don’t experience hum after i swap to single ended pre. At a friend place, the same MP-1 preamp function just as great.@philipwu The most likely cause is that the amp you were trying to drive wasn't actually balanced. It may have had the XLR connector (an example of an amp like this is the Lamm 1.1, also any VTL amp equipped with an XLR input), but if the circuit inside wasn't balanced you would totally get a hum. The reason is that the output of a balanced source occurs between pin 2 and 3 of the XLR, and **ignores** ground. If that's connected to a single-ended input, essentially the unused pin (usually pin 3 when this problem shows up) acts like an antenna for noise because the circuit isn't completed! There are several solutions, certain adapters can be made to work, line transformers and its often possible to modify the amp slightly so that it will accommodate a balanced input.
I frequently show at audio shows with speakers that are 105db 1 watt/1 meter and do it with no hum.
the version i upgraded from isn't all that important, simply because v1.2 is better than v1.1
If you are asking ,for example whether Rhythm v1.1 is better than its cheaper and latest Rhumba Extreme v1.2, that i have no answer as i didn't A/B audition it before.
What i hear is an overall enhancement by about 10-20% in every sonic attributes, going from Rhumba to Rhythm. i.e sound stage, clarity, dynamics, palpability, airyness, details, transparency and speed too. i'm not good in describing the sonics but it's definitely noticeable improvement.
Another good thing is Backert Labs preamp are responsive to tube rolling, even though i don't like the addition cost involve with NOS tubes $$$
you may wish to discuss more in depth with Andy about new enhancement in the later versions.
" Does tubes make this kind of music sound "slow and syrupy?"
I can tell you from my experience with the Rhumba 1.2, and using the excellent CBS 5814a tubes, your statement is about as far from the truth as can be. This is no vintage Conrad Johnson preamp!
I have also used close to a dozen other tubes in the Backert, and never did it become slow and syrupy.... warmer, sure, less detailed, sure, but slow.... never!
Hello - nice to see this thread, we thank milpai and the rest of you.
Something above referred to "the higher output impedance of the preamp" .... actually the Rhumba 1.2 preamp has an output impedance of less than 75 ohms, which is quite low. It allows the Rhumba to mate nicely with any power amp you might select.
Thanks again and please don't hesitate to write us, or call if you have any questions.
I have now lived with the Backert Labs Rhumba 1.3 for about 4 months and thought I would give my feedback on this preamp. First I should acknowledge that this is a preamp that has ALL the traits of my TVC (sold off), AND adds dynamics that I only found out after adding this preamp to my system. My ProAcs sounds the "full range" that they are.
My biggest worry was the loss of transparency if I went active. On first listen thought that I had lost transparency, only to immediately realize that the transparency is still there, but I was not used to the extended low end that this premp produced in my system. The highs are also more airy than the TVC. Contrary to what I feared, this preamp adds "life" to discs that have excellent dynamic range. I say this because the CDs that are a "loudness mess" sounded fine with the TVC, but the well recorded CDs (example Hobo, Sara K) did not sound as impressive as they do with the Rhumba. I can say this NOW, because I have now experienced how these CDs should sound like. I have a feeling that a TVC would sound great with a tube amp and a super sensitive loudspeaker. In my system, it sounded very good, but nothing close to the magic that the Rhumba 1.3 is doing.With the Rhumba 1.3, I am enjoying my music collection as if I purchased them all new again. At my listening position I can actually "feel" the bass that it produces with my ProAc D48. This never happened with the TVC. But again, I should not blame the TVC for that. If anything I have to blame myself, because I was always worried to take the volume past 18 (of the 24 positions) on the TVC, fearing that it would not sound good. My gripe about this preamp is that CDs that have messed up recording (dynamics) are played as-is, without making them sound good. Example is John Mayer Continuum CD. It sounds pretty loud at 9'O clock position and it does not sound as impressive. I always thought of tubes as "thick syrupy" sound. Fortunately this is not true. Some "brittle" sounding CDs still sound bright in the treble range.This preamp comes with the new issue of Mullard tubes. They sound pretty good. But Thanks to @almarg. I have replaced them with Gold Lion tubes for the added midrange magic and extended dynamics at both end of the sound spectrum. Vocals sound so real with these tubes. Of course, with the new preamp, I had to reposition my loudspeakers for the best possible sound. Thought I never missed remote control for the past 9 years that I used the TVC, I love the remote volume control. The remote has only 2 buttons, but the weight is substantial. The tube replacement cover is pretty neat. I used to keep it open while listening to the system, for the first month. But I was told that this premp has the appropriate design to vent out heat and I need not keep the cover open.All in all, I am super happy ( as if you cannot make that out from above) with this preamp. Sorry, if it sounds as if I was advertising this preamp - but no, I am not. I am thrilled with what it has brought in my system and listening experience. Thanks to Ralph, Almarg and my dealer who pushed me to get a tube preamp. And thank you to all the Rhumba users who provided me with their feedback.
@rdoc,Good to know. What are your source and loudspeakers?The Rhumba throws a huge soundstage in my system.
The Rhumba acts as a measurement tool for me. If I am able to listen to CDs at 10 o'Clock position, it tells me the recording on the CD is not dynamically compressed. If it gets loud by 9 o'clock position, then the recording sucks.
I am absolutely thrilled by this preamp.
I use a Musica Pristina Server with a 1 TB ssd to hold my music. The MP is connected to a PS Audio Directstream dac via I2S which is a lot better than usb. Loudspeakers are Sonus Faber Elipsa SE's and REL Carbon Limited subs. Soundstaging is glorious in width and depth. One of my non audiophile friends that sat to listen for the first time asked, "Do you have speakers behind us?". The system is very easy and non fatiguing to listen to for hours. You can see a picture of my system on the PS Audio forum under the "System Photos" thread. The Rhumba 1.3 is a very big part of sound of my system.
@1markr and rdoc
I am actually considering the Pass Labs XA30.8 and I was recommended to go with the XP22. I was interested in a tube but I did not want to deal with the maintenance of tubes. It looks like I might be pulled back in with the Rhumba.
The speaker I am considering are the Verity Otello’s and they definitely work best with tubes....Help...🤔
Can’t help you with recommending a SS preamp, haven’t used one in many, many years! I can tell you the Backert Rhumba is a great match with my Pass XA-25, and @jackd is right, the tube maintenance is nil for the Backert; it’s easy on it’s pair of 12au7 tubes, and very easy to replace. It also gives you the opp to tune your system based on tube choice for the Backert.
I have never had tubes in my system. Last year was the first time I went with tubes. The Rhumba runs the tubes gently. So the tube life is pretty good. I believe it is a few years. And replacing tubes is not that difficult. I used to think that tubes have thin glass. That changed when I replaced the Mullards in the Rhumba with a pair of Gold Lions. This is a very musical preamp and I hope you get to try one in your system. If it does not work, you can always return it. Which I doubt you will.