My understanding is that turning off one of the amps stops the preamp from using that signal path.
However it does not stop the preamp from being loaded by the combined input impedance of both amps, given that almost all preamps providing dual outputs drive both outputs from the same output stage.
Consequently I would rule out the Rogue preamp that was suggested. The balanced input impedance of your Benchmark amp is 50K; the balanced input impedance of the Luxman amp is 34K. Assuming those numbers apply when each amp is powered down (which is not always the case) their combined impedance is (50 x 34)/(50 + 34) = 20K.
Stereophile measured the balanced output impedance of the Rogue RP-7 as rising from extremely low values at mid and high frequencies to a very high 5.64K at 20 Hz. Not a good match, given the wide variation of output impedance coupled with the ratio of amp input impedance to preamp output impedance of less than 4:1 at 20 Hz.
The Makua, Ayre, and W4S preamps that have been suggested should be ok in that respect. Not sure about the EAR.
Good luck. Regards,
I owned the Makua but not with the DAC + streamer. I am sure you can find one online for way less than $20k I recently sold my Kaluga and Makua. I also own the Lumin X-1 after previously owning the A-1. I absolutely love the X-1 and that will be my streamer / dac for at least the next 10 years. The Lumin App was so good in my mind that I did not need ROON.
The Makua, Ayre, and W4S preamps that have been suggested should be ok in that respect. Not sure about the EAR.Thanks all for these great suggestions, it would have taken me a while to find them. I am actually aware of the suggested preamps, and I must have heard the W4S during a show demo, but did not know they had dual outputs. It was something that I never was looking into until this recent need.
Now I have some research to do while I work on my job.
@almarg Thanks for the math. Do not really understand but I will take your word for the suggestion.
@willgolf I am working with a dealer on the Makua so I plan on getting it from him if I go that way, not at MRSP as I listed but something with a discount. There is a unit available today on A’gon from Australia for $10K but I started with the dealer so I will continue to do so.
Did you use the Lumin A1 as the DAC with the Makua?
Are you using the Lumin X1 directly to an amp? I do not mind doing that myself and buying a $2.5K Benchmark preamp for my analog sources. That is if the direct to amp Lumin X1 is not compromised, especially at low volumes.
I should add that I am really interested in doing my streaming from a fibre optical network such as supported in the Lumin X1. It would only cost me about $300 to buy the network gear to do this. I also have a lifetime subscription to ROON so I will stick with that. Roon is actually becoming pretty amazing with the latest release.
I just spent some time reading the reviews of the W4S preamp. They make it seem like a slightly noisier version of the Benchmark LA4, but with the specs I am looking for with dual output XLR. Both peamps are being described as "straight wire with gain".
When I first saw photos of W4S a long time ago I had the impression it could not be the ultimate in sound quality. Then a few years ago I heard W4S demo their then new mono blocks with a full W4S stack and KEF Reference 1 speakers. I was really impressed by the sound and how much I was into the music. They were playing some Pink Floyd in a nice hotel room. The sound of their gear was was completely deceiving to me given my impression of the looks (though looks do not matter if the sound is excellent).
The W4S 10 year anniversary DAC should also be something I should consider if I persue the W4S preamp. The ESS Sabre DAC’s maybe a good choice with the softer sounding Yamaha NS 5000 over the Denafrips (Lumin X1 is also Sabre).
I am really excited about the pre-amps listed in this thread. It is only recently that I came to understand what those dual XLR outputs can do. It took me about a year of figuring things out to get me to this point. I am lucky I was broke last year and could not afford to prematurely buy the wrong gear.
I should add that I am looking for the XLR outputs of the preamp to support the Balanced XLR AES48 standard. I have confirmed with Benchmark and Mola Mola that their units do support it. This is important to me because I plan on putting everything, except the amps, far away from the speakers. I may need something like 25 feet of XLR to reach the amps. I do not indent to spend a lot of $$ on the XLR’s if the AES48 standard is supported.
Now off to read about the other preamps listed above.
Like others have said, there are several preamps that have dual XLR outputs. However, the only preamp I know of that actually has a separate analog output stage driving the second set of XLR outputs is the Classe CT-800. I think the new Classe Delta preamp may work the same way, but you should check with Classe.
The Atma-Sphere MP-3 and MP-1 both have dual balanced outputs and no worries driving low impedances. FWIW Atma-Sphere made the first balanced line preamps anywhere way back in 1989.
A tip: If your preamps supports the balanced line standard also known as AES48 (Audio Engineering Society file 48) then you will have the ability to drive longer cables without coloration, and less coloration from cables in general. You will also have less likelihood of encountering a ground loop. This will allow you to place the amp right by the speaker if you want, allowing you to run a shorter speaker cable. You also won't have to spend as much on the interconnects!
@atmasphere You are my AES48 hero (save me $$$) and I have been including that feature as an essential requirement when I look into the preamp - amp interface. With my limited experience with Benchmark gear, which support AES48, I tend to agree with your statements about the XLR interconnects. I just did not understand why my Benchmark observations were that way until you explained AES48 in some other threads.
I am not sure if a tube preamp would work well with the Yamaha NS 5000 speaker. I am also not sure if I would get the benefit of super low noise floor of the Benchmark AHB2 with a tube preamp. The Yamaha system will already be a softer sound with the Luxman and the KEF LS50 will be very detailed with the Benchmark. This is my intention to have 2 flavors of sound in my room. I will read up on these 2 atmasphere preamp units though.
So far the W4S preamp jumps at me as being in the same vein as the Benchmark and Mola Mola Makua in design, "straight wire with gain". Though the W4S is supposed to only add gain after pot 64 in the volume control, not sure what that means. I have posted a question to W4S on Facebook about support for AES48. If they respond I will post the answer here.
I would have suggested Ralph’s preamps, but it seemed like you wanted only SS.
To save you some research Ayre KX-R supports the AES 48 standard. If you can find a non-Twenty version, it would be a less expensive route- while still giving you the option of upgrading when finances allow.
That is what I did.
I have not heard the Ayre but I know people consider the 20 reference caliber. I will keep any eye out for a used unit since I have not bothered a dealer with an audition for that one. I have no problem buying used but not if I demo the same gear at a dealer.
You were correct in your assumption about tubes for the reasons I mentioned above and also the heat factor in my corner room that gets hot in the summer. I spend 8 hours+ a day working and listening to tunes in there. So cooler temp equipment is important. I also have 7 thin computer screens in this room too and they give off heat right into my face. Only 2 silent computers though.
Anyways, the list of preamps that is compiled here is really awesome.
I was just conversing via email with another Ayre KX-R owner. He and Mr. V. agreed that the Twenty update brought the KX-R to significantly higher level.
I own both the KX-R (non Twenty) and an Atma MP-1 3.3. I used to own the MP-3 3.3, but the KX-R was a definite upgrade, so I had to have Ralph build me an MP-1. Thanks Ralph!😊
I have only had the MP-1 for a month, so things are still burning in, but I think Ralph's work will be the winner.
So, when Ayre has one of their upgrade 'sales', the KX-R will be going in for a tune up- finances permitting.
I really don't need 2 preamps (nor Amps, I also have a set of MX-R's), but after 35 years, I just had to scratch the SS vs. Tubes itch.
To my mind, you wouldn't be unhappy with either the Ayre or Atmasphere preamps, both provide super clean sound. I would have to have my head in a vice for hours to find a negative thing to say about either.
@don I used to own the BAT VK 42-SE preamp. I do not recall now if it had dual XLR’s but it was pretty good. A little soft on the top but a relaxing sound, at least compared to the Bryston BP25 preamp it replaced.
I bought that one used without hearing it first. It turned out to be the best gear I had at that time.
@zprr The place where I may buy the NS 5000 is also a dealer for Simaudio. Something to consider. I may also consider buying the NS 5000 online to have a 60 day home trial. I am almost 100% certain that a CONVOLUTION file for DSP running on ROON will solve any room issues with this rather big "bookshelf" speaker. There is company/guy up in Canada who can create these DSP files given some room measurements and other info. I am reading his book to see if I can do it myself.
I thought the Simaudio 850A preamp and second from top amp were great with the Paradigm Persona 5F I auditioned at the NS 5000 store.
To my mind, you wouldn't be unhappy with either the Ayre or Atmasphere preamps, both provide super clean sound. I would have to have my head in a vice for hours to find a negative thing to say about either.That is the sound I am gravitated towards. I seem to like a lot of variation of sound but clean sound (not colored) seems to be what I like the best. In reality I can enjoy a transistor radio if the tunes are good.
From the measurements section of Stereophile’s review of the BAT VK-51SE:
The balanced output impedance was twice that specified, at 410 ohms over most of the audioband. This is low, though it did rise to a high 4.7k ohms at 20Hz, due to the size of the output coupling capacitors.
Which means that this preamp is not compliant with the AES48 requirements Ralph has described. It also means that it would not be a good match for the 20K load it would see when connected to both amps, assuming (as is highly likely) that its two balanced outputs are driven by the same output stage.
YYZ ---I had the Lumin A-1 connected to an Emm LAB Dac V2X1. Once I got the Lumin X-1 I sold the EMM Lab. It is to bad I got rid of my brand new Mola Mola's. I traded them in to a dealer for Canary Audio Tubes. You could have purchased mine which were never used for a great price. Good Luck in your search.
Man I cannot believe I did not remember the Luxman c900u has this dual output XLR feature. I demoed this preamp 2 times too. Getting old.
Selects an output mode from the following 3 kinds: unbalanced output, balanced output, and bi-amplifier output
If you can find a used one, the Threshold T2 has dual XLR outputs. I'm using both on my system, one with short XLR cables going to a Threshold SA/4e, the other going with 35 foot long XLR's to a pair of Emotiva XPA-1 monoblocs. The signal with both sets of amps is dead silent at the speakers with no signal,
Questions to W4S:
1. Does the STP-SE preamp support the Balanced XLR AES48 Standard for the 2 XLR outputs?
2. Can I hook up 2 amps to the preamp. I want to use a Benchmark AHB2 amp and a Luxman m900u amp connected to 2 different speaker sets. I would turn one of the amps OFF when using the speakers connected to the powered up amp.
3. The balanced input impedance of your Benchmark amp is 50K; the balanced input impedance of the Luxman amp is 34K. Assuming those numbers apply when each amp is powered down their combined impedance is (50 x 34)/(50 + 34) = 20K
Answers from W4S:
Thank you for your email and interest.
BTW - that Luxman c900u does not support AES48. I forgot that I asked the engineers.
The W4S is what I will do a home trial with first. I many even try their w4S Anniversay DAC though the Lumin X1 DAC is something I wanted to try with a preamp that does not have an internal DAC. In about 10 days I see where the money to do this comes from.
am not sure if a tube preamp would work well with the Yamaha NS 5000 speaker. I am also not sure if I would get the benefit of super low noise floor of the Benchmark AHB2 with a tube preamp.@yyzsantabarbara A good tube preamp had better not be a tone control! It should just be neutral. This is not a bandwidth thing either- for example the line stage our our preamps goes out to about 400KHz- higher than many solid state preamps. The thing here to be aware of is the brightness of solid state is not on account of frequency response; just about all preamps tube or solid state will be nice and flat in the audio band. The brightness of solid state is the result of distortion, and really not a lot of it because of how the ear works.
The ear uses higher ordered harmonics to sort out how loud a sound is and because it has a range of over 120dB, it has to be very sensitive to higher ordered harmonics. So if a circuit makes higher ordered harmonics even in very small amounts it gets interpreted by the ear/brain system as brightness and harshness. We are talking about THD that might only be 0.005%.
That is different from simply being neutral. Your Yamaha speakers might be easy going on top, but if you put something extended that is also neutral this will not cause them to sound rolled off!
Regarding noise, its nearly all power amps are lower noise than a preamp. Yet people use tube preamps in systems with **horns** all the time; your Yamahas are not as efficient as horns so you've got no worries in this department :)
@atmasphere What you wrote is very interesting. I would like to have a phone conversation with you when I have the cash to buy. I am inclined to get a SS preamp, but I some flexibility in this choice, maybe get both to have some great combinations in the pairings. I need to talk to understand a few things.
Getting very close to buying time.
Thanks guys and gals who posted suggestions on this thread. I have more than enough options now.
I can assure you Ralph and his staff will give you great advice.
Like I said, I owned both the MP-3 and now the MP-1.
Had I not moved to an Ayre KX-R, I wouldn't have known/cared about the difference between the two Atma preamps.
So, if your budget limits you, I would consider an MP-3 in a heartbeat.
-And, you can always upgrade when finances allow- like I did.
My Esoteric C-03x had two pairs of balanced analogue outputs and two pairs of RCA outputs. I assume most Esoteric preamps of the past decade would also. The C-03x also lets the user turn off either the RCA outputs or the XLR outputs. Another option few will wish to take but which has worked for me is a professional monitor controller. I'm overall very pleased with the Crane Song Avocet II. It includes their Quantum DAC with three AES digital inputs, three analogue inputs on XLR, and three analogue outputs on XLR. The analogue outputs are switched: only one is active at a given time. Anyway, for what it's worth, it replaced the 4 or 5 times more expensive Esoteric C-03x and drives my active speaker system via 30 ft. Mogami 3173 interconnects (excellent for both analogue and AES digital).
@dr_joe That is some out of the box thinking.
Do you do streaming from Tidal or Qobuz. If so how do you do it into this DAC?
Is there a streaming device that is ROON READY and can output AES into this Crane. DAC?
This system is for my office and I am really open to something different.
@yyzsantabarbara If supporting the balanced standard is important to you (it results in better sound...) one thing you can look for on any balanced preamp is whether it has RCA outputs as well. If there is no switch to go between the balanced operation or single-ended, then you can conclude that the preamp does not support the standard.
The switch would be used to sort out the ground issue. If there is no switch that means that all the outputs of the preamp reference ground and so ground is used to complete the signal circuit.
One exception to atmasphere's comment directly above is a pre-amp using a transformer to create the balanced output(s). That's exactly how Tim de Paravicini does it in his EAR-Yoshino pre's. There is an EAR 868PL (phono and line stages) listed on Audiogon at the moment, and it has two pair of both XLR and RCA outputs.
One exception to atmasphere's comment directly above is a pre-amp using a transformer to create the balanced output(s). That's exactly how Tim de Paravicini does it in his EAR-Yoshino pre's. There is an EAR 868PL (phono and line stages) listed on Audiogon at the moment, and it has two pair of both XLR and RCA outputs.Actually if a transformer is used, it has to have a switch so one side of its secondary can be tied to ground in case the output is to be single-ended. So a switch is required.
The only way to do balanced otherwise using a transformer and no switch is a a transformer with a center-tap. But this would sacrifice a lot of common mode rejection performance since the center tap can't be exactly placed at the center of the transformer windings. which is why no-one does it that way (as far as I know).
Ralph & Eric ( @atmasphere , @bdp24 ) I looked at a schematic of the EAR 864 preamp, which is included in the owner’s manual that can be found at hifiengine.com.
Its output coupling transformer has two separate secondary windings. One connects to pins 2 and 3 of its single (per channel) XLR output connector. One end of the other winding connects to the center pins of its two paralleled RCA output connectors (per channel) via a 100 ohm resistor, with the other end of that winding connected to circuit ground. Pin 1 of the XLR connector and the ground sleeves of the RCA connectors are connected to circuit ground. There is a 1K resistor across each of the two secondary windings.
So the use of two secondary windings explains why there is no XLR/RCA switch. Presumably the 868 is similar in that respect, and I’d imagine that these and perhaps other EAR designs are fairly unique in that respect.
@bdp24 Well there you have it. A transformer with a dual secondary so that the single-ended and balanced connections can't mix. The upside is that both connections can be supported at once; the downside is there is additional capacitance due to the presence of the second output winding. This probably does not affect bandwidth much on account of the transformer being fairly low power. Note though that it is designed to support the low impedance aspect of the balanced standard; the 1K resistors @almarg mentioned are there to load the transformers to prevent ringing if used with a load of higher input impedance.
Great, thanks fellas. Isn’t education and knowledge a wonderful thing? ;-) This kind of information was regularly included in reviews in Audio Magazine (except those of TAS alumni Anthony Cordesman), and Stereophile when Gordon Holt and Dick Olsher were doing them. Harry Pearson and his pals at TAS had no technical education or knowledge, and set in motion the subjective-only style (no bench tests, no circuit descriptions) of hi-fi reviewing.
At one of his S. California instore appearances in the 1980’s (to introduce a new model), Bill Johnson told the assemble crowd a story about sending Pearson a new ARC pre-amp (I don’t recall which model). Bill soon thereafter received a call from Pearson, who told him it was defective. He had Pearson send it back, and of course tested it when it arrived back in Minnesota, where the pre-amp worked fine.
Johnson asked Pearson a series of questions to get to the bottom of the problem, and soon had his answer: Pearson had installed shorting plugs into the pre-amp’s unused output jacks! He knew enough to know that shorting plugs can prevent noise getting into unused input jacks, but not enough to know that you shouldn’t short output jacks. Golden ears, perhaps, but is that all that is required to be a professional hi-fi reviewer?