Preamps - Analysis and Reviews

[gmgraves]

21 hours ago, Johnseye said:

I think I can speak for the majority of this community when I say we're all in a constant search for improving our two channel sound.  About a year and a half ago I began an endeavor to focus on rebuilding a two channel system.  I've made many changes since then.  This most recent being the addition of a preamp.  I have a Marantz prepro that I use for multi-channel and my Audio Alchemy DAC has a pre.  Both do a good job.  I was very happy with how the AA sounded, but I had read quite a bit about using a tube pre and I wanted to see what that was all about.  So I began a several month effort to audition a handful of respectable tube pre's and tried to stay around the $5k range.  During this time I learned about Benchmark's release of their DAC3 and because I've found their AHB2 amp to be the quietest amp I've ever heard, after talking to Rory at Benchmark I threw that in the mix as it has a pre.  Then a local dealer told me about the upcoming Anthem STR Pre, another solid state.  He had a new Anthem integrated with a similar design concept so I gave that a listen as well.  There are macro changes we can make to our system and there are micro changes.  After the choice of speakers or headphones, the preamp can make this biggest difference.  That said, I find it interesting that there is no section in this forum for the likes of preamps or amps, which is why this review landed in the General section.  If others would like to contribute to this thread by adding their own preamp review, including any I've discussed, I'm good with that.

 

Testing was done in both analog and digital realms.  I'd be happy to share the various cables I swapped out, turntable and music sources if requested but otherwise won't get into that in this first post.

 

The contenders:

 

Rogue Audio RP-5 - $3.5k

Backert Labs Rhumba 1.2 - $3.4k

Backert Labs Rhumba Extreme - $5.5k

Benchmark DAC3 HGC - $2.2k

Anthem STR Integrated - $4.5k

Audio Research LS28 - $7.5k

Atma-Sphere MP-3 - $5k

Atma-Sphere MP-3 with phono stage and Vcaps - $7k

 

 

Rogue RP-5

http://www.rogueaudio.com/Products_RP5.htm

This was the first tube pre I took home.  It's been a while so my recollection won't be as detailed as the other pre's.  I plugged it in, let it warm up and man was I disappointed.  I had heard so much hype about tube pre's and while I've heard them at Axpona and in stores, that was with completely different equipment.  There is one caveat to this experience.  The RP-5 doesn't have balanced outs so I had to use my older Emotiva amp as the Benchmark only has balanced in.  Noise level from the Emotiva aside, the RP-5 sounded flat.  The dimensionality shrunk by comparison to the AA pre.

Backert Labs Rhumba 1.2

http://backertlabs.com/to-purchase/

The Rhumba sounded much better by comparison to the Rogue.  There was more dimensionality as well as very good top and bottom end clarity and oomph.  It was more in line with what I was looking for, but it still sounded a bit like solid state.  I also had the Benchmark DAC3 and ARC LS28 at the same time so was able to compare all back to back.  The Rhumba's remote is a simple volume control, that's all.  Andy, Backert's president was very communicative.  When I gave him my initial feedback he sent me out another set of tubes to try.  When you get to my comments on the ARC you'll understand why.

 

 

Backert Labs Rhumba Extreme

Very similar to the 1.2.  If I were to describe the difference it would be that the Extreme is slightly cleaner sounding.  The $2k is probably better spent elsewhere.

 

Benchmark DAC3 HGC

https://benchmarkmedia.com/collections/digital-to-analog-audio-converter/products/benchmark-dac3-hgc-digital-to-analog-audio-converter

The Benchmark sounded extremely clean.  It paired up nicely with the AHB2 from that perspective.  The remote is solid and everything is very well built.  It was however very similar to my AA DAC in almost every respect.  The only real difference was in the clarity which contributed to a bit more dimensionality.  But it was clinical to my ears and not in the direction I wanted to go.  My entire two channel system up to that point was built around clean and clear.  Now I needed to add some body and musicality, not more crispness.  If I were to choose between the AA and the DAC3 I'd probably take the DAC3, but the improvement was so slight it didn't justify keeping it.

 

Anthem STR Integrated

https://www.anthemav.com/products-current/model=str-integrated-amplifier/page=overview

I won't go into this one too much as I didn't give it that long of an audition.  It's a decent sounding solid state amp.  Where it shines is in its room correction which I didn't setup.  It also allows for a more seamless subwoofer integration.  If I were looking for a new solid state pre I would strongly consider the upcoming STR for these features.  From a sound quality perspective without the room correction it sounded flat and 2 dimensional.  The reason why I didn't use the room correction is because it was setup for the store and they didn't give me the mic.  Not a good way to audition a pre.

 

Audio Research LS28

http://www.audioresearch.com/en-us/products/preamplifiers/ls28

I had been sharing my plans and experience with @Ralf11 in another thread and he recommended I give ARC a listen.  While I had heard some things about ARC I hadn't given them serious consideration.  Many of the commentaries in reviews I read people had tried ARC, then moved on to something else.  Audio Research has been around for a while.  I found a local dealer and the owner agreed to let me take an LS28 home.  His store was about an hour and a half away but he lived about 45 minutes from me so we met close to his home.    I hadn't even asked about the price yet.  When he told me what it was I was thinking, well this is about double what I want to spend.  I thought I'd give it a listen but couldn't imagine taking it much further.  When I got it home and started to listen I thought wow.  Just wow.  This is what people were talking about when they hear something good from a tube pre.  The soundstage the LS28 creates is big.  Not overwhelmingly big,  but it made other pre's I'd listened to small by comparison.  It was like when I heard Magnepan for the first time.  A large, full soundstage.  Then there was the fullness and balance of the sound.  A full midrange combined with excellent highs and lows to probably the best combined tonality I'd ever heard.  This is what may lead to the next thing I noticed and that was the timing.  That blew me away.  I was hearing the timing between musicians where their changes were clear as day.  This I had never heard in a system.  Mick, the owner of the store who lent me the LS28 said he thought it was incredibly close in sound to their Ref 6 and that this was a new step up for Audio Research.  I then went out and read whatever reviews I could find on the LS28 and others were confirming a lot of what I heard.  It's an incredibly light unit by comparison to the other pre's.  I think the chassis must be made out of a lightweight aluminum.  The remote is hefty and solid however.  Unlike the Backert remote it can do everything the interface can.  I could go on about this pre and likely will later, but this was my new standard.

Atma-Sphere MP-3

http://www.atma-sphere.com/Products/#MP-3

Ralph, the owner of Atma-Sphere spent a couple hours over multiple calls chatting with me about technical details.  He's an incredibly patient and knowledgeable engineer.  Unfortunately when I receive the MP-3 it was out of phase.  I couldn't get a center image, so he recommended I swap polarity on a single speaker.  That did it.  There were a couple other issues I clarified with him and he eventually sent me out a replacement which I just got today.  This time I opted for full Vcaps as well as a phono stage on his recommendation.  I've had the other MP-3 for a few weeks now so plenty of time to compare it to the LS28, which I still have thanks to Mick's graciousness.  The MP-3 is the closest thing I've heard to the LS28 and by some characteristics it's better.  It carries the same soundstage which I found very interesting.  The coincidence is that ARC, Atma-Sphere and Magnepan are all based in the Minneapolis-St. Paul area, and they all have amazingly similar soundstages.  What the MP-3 does better, and only very slightly, is in its clarity.  Instruments are a little more defined, maybe a little brighter.  However the MP-3 doesn't have the same feeling of timing that the LS28 has.  Perhaps there's a slight lacking in the midrange, I'm not sure.  The replacement MP-3 I received also has a remote where the first one didn't.  The remote is the exact same one as the Backert, just volume.  There is an actual belt motor that turns the volume knob inside of the MP-3.  This is by design to keep with their minimalist approach to the circuit board.  Unfortunately I've run into some issue with this version of the MP-3.  The volume control has steps for each level and the remote doesn't seem to match with those steps.  I will also hear a significant amount of white noise when the volume is in between steps and the remote volume lands right on those spots sometimes.  Another issue I've found is that this version has a significant amount of noise when idle.  It's possibly due to the phono stage as when that's active there's much more hiss.  But the linestage also has more noise than the other MP-3.  I'm not sure what the issue is, but it's a shame because this is a really nice sounding pre otherwise.  It's also fully balanced and has a patent on that engineering.  Take a look at the website for full details.

 

 

And the winner is the Audio Research LS28.  Thanks Ralf.  Mick has extended his offer and allowed me to keep his store's model until mine is built and arrives.  He'll stop by when it's ready to sit down for a listen in my theater room where this is all setup.  I've asked him for some advice on any additional room treatments and equipment positioning.  I've built all my current room treatments with acoustic cloth and duct dampening insulation.  I've had a pro come by and calibrate my theater equipment, but never from a 2 channel perspective.  Mick was trained by some well known room acoustic engineer in Germany who's name I've forgotten so I'm looking forward to his opinion.

 

During the past few months I've also played around with moving the pre away from the amp and speakers using a balanced run.  For some reason when I did this I thought the sound closed up a bit.  I went from 1m XLR to 4.8m between the pre and amp, but this allowed to shorten the length of my current phonostage to pre single ended interconnect.  It could be that the new XLR cable is from DH Labs where the previous is Audioquest.  Ralph at Atma-Sphere included a 5m XLR pair of Mogami cables with Neutrik connectors, and that sounded closer to the Audioquest cables.  This is another area where more testing is needed.

Have you listened to the Parasound JC-2? It was designed by John Curl and is considered State-of-the-art for about $5k.

[gmgraves]

16 hours ago, Johnseye said:

 

I briefly considered listening to one. I almost bought an A21 amp and would have had I not discovered the Benchmark. I wanted to stick to tube pre's and the only reason why I tried the DAC3 was because I really wanted to hear how it paired with the AHB2, and the Anthem because I've been looking for a better way of blending my sub for 2.1.

 

Luke Manley of VTL makes a couple of very good, very capable tube pre-amps. Don't forget to look at those. Also Audio Research preamps do have tubes, but traditionally, their line-outs are solid state. 

[gmgraves]

1 hour ago, Johnseye said:

 

VTL is another I'd never heard of, thanks.

 

What do you mean ARC's line outs are solid state?

 

VTL is Vacuum Tube Logic. They are very respected name in tube audio electronics and are a spin-off of Manley Audio. By the statement that ARC's line-outs are solid-state, I mean that although they have tubes in them, the final stage of ARC preamps is transistorized. IOW, they aren't completely tubed. So if it's pure tube you're interested in, ARC is probably not what you're looking for.

9 minutes ago, Johnseye said:

 

I don't think they make any solid state preamps

 

I don't know if they make any 100% solid state equipment any more or not, but traditionally, the final output stage of ARC preamps have been transistorized. I can't verify that the REF-6 has a solid-state output stage or not, as I cannot find any mention of it or a schematic online, but it is traditional for them. Again, to make sure, contact ARC directly. 

[gmgraves]

15 hours ago, pkane2001 said:

 

Never? How can you be so sure that adding one more complex, active component with additional interconnects in the path of analog signal will improve signal quality?

 

I don't know about sound-wise (the simpler the circuit, the better a preamp should sound - in fact, a passive preamp or one using a stepped transformer for gain, always sounds better than a powered one), but certainly the "preamp" section of a DAC is not going to be as flexible  as a stand-alone preamp. Of course, it depends on one's needs. Perhaps the OP doesn't need any flexibility as his only sources are digital and all he needs is USB, optical and coax SPDIF, a way to switch between them, and a volume control.

[gmgraves]

46 minutes ago, Speed Racer said:

 

If that were true a Schiit Sys would sound better than any quality preamp. Freya sounds better in tube gain mode than passive mode. 

 

I’ll take a tube preamp any day over a passive preamp. 

An awful lot of people disagree with you. I know a number of people who own Freyas, and all of them found that the passive mode sounds better than either of the active modes. The best I've heard was a British- made transformer based "preamp". It had a stepped volume control that switched different taps on the transformers in and out to change the gain. Sorry, I don't recall the make.

[gmgraves]

32 minutes ago, 4est said:

Music First using Stevens and Billinton xformers?

You know, now that you mention it, I think that's correct.

[gmgraves]

14 minutes ago, 4est said:

You make that sound as if there is no reason for a preamp to exist or that it is some new fangled device. Traditionally the preamp was used not only as a selector, but as a buffer fore and aft the attenuator. Those were and still are good reasons. I've yet to hear a DAC direct that wasn't helped by a great preamp. I am sure there are some, but I've yet to hear one.

 

If that were strictly correct and all the preamp did was provide switching and a buffer stage before and after the volume control, the line-in inputs would all be unity gain. But all active preamps generally provide about +10dB of gain for the high-level inputs (of course that doesn't include the phono stage, if any).

[gmgraves]

20 hours ago, 4est said:

The buffering is often still there.

By definition, the buffering is always there with active stages. The difference is that with unity gain, the amplitude coming out of the preamp is the same level as the input. With gain, the buffering stage will still be the same (tube or solid-state) but the ratio of the resistors used in the stage will be a different ratio, thus giving one gain. Of course the same thing applies with a transformer-based "preamp". gain is obtained by the turns ratio of the primary to the secondary coils in the transformer. Often the secondary is tapped and the taps fed through a rotary switch to attenuate the gain in steps. In this case, the transformer provides the buffer from the source, but with the output, occurring after the stepped volume control, the impedance of the different taps on the transformer varies the output impedance where, with an active stage after the volume control the output impedance remains constant. Ideally, you want audio components to have a very high (>10KΩ) input impedance and a very low (as low as possible) output impedance. In solid-state power amps the output impedance is often much less than 1Ω. Preamps CD players, DACs, tuners tape recorders et al, the impedance is most often less than 100Ω.

[gmgraves]

6 hours ago, pkane2001 said:

Absolutely, I agree with most of your points. I have my own biases about what 'good' sounds like.

 

I disagree with the "if it sounds 'good' to me that's all I need, I don't care if my idea of good sound is different from others" attitude. I believe that 'real' sounds good, and anything that differs from that is wrong. Music-loving audiophiles should recalibrate their ears as often as is possible. One should do that by listening to as much live, unamplified music as is practicable. If one keeps reminding one's self what the real thing sounds like, one is less likely to go off the rails. If you find that you prefer overly bright highs, and boomy bass, you should at least know that's not what real music sounds like, even if you believe that's what real music should sound like!

[gmgraves]

19 hours ago, pkane2001 said:

 

I agree with your sentiment about the need to hear live, unamplified music. I live not far from NY city and go to various live performances and concert halls at every opportunity. I also play the piano, and its sound has been one of my main measuring sticks for tuning my system. 

 

But, I also think that whether or not you know what 'unamplified music' or the 'real thing' sounds like, you will not be able to get that from a large number of recordings, no matter what you do to your system. If you are trying to tune each recording to sound like what you think it should sound like, you'll wind up chasing your tail. Some recordings will sound better, some worse with every adjustment. The only reasonably achievable goal is to try to faithfully reproduce what was recorded. That's about as good as your system can possibly get and no more.

 

The piano works as a reference! I also agree with you about recordings. It's one of the things that drove me to start recording. The reality is, that most recordings sound terrible. They're either overproduced to the point of ridicule, or they're incompetently recorded. There used to be a producer at RCA Victor named J. David Saks. I once almost got into a fist-fight with him at a AES convention in New York. I naively thought that if I told him how bad his recordings of the Philadelphia Orchestra sounded and why they sounded so bad, he would mend his ways. Boy was I wrong! Instead of thanking me for my suggestions about minimal, true stereo miking technique, he defended his multi-miked, console mixed method of recording as being "better than real". This ended in a shouting contest that almost came to blows. John Eargle and someone I didn't know came between us and prevented a donnybrook. As I walked away with Eargle, he whispered to me, "I agree with you."

[gmgraves]

19 hours ago, pkane2001 said:

 

I agree with your sentiment about the need to hear live, unamplified music. I live not far from NY city and go to various live performances and concert halls at every opportunity. I also play the piano, and its sound has been one of my main measuring sticks for tuning my system. 

 

But, I also think that whether or not you know what 'unamplified music' or the 'real thing' sounds like, you will not be able to get that from a large number of recordings, no matter what you do to your system. If you are trying to tune each recording to sound like what you think it should sound like, you'll wind up chasing your tail. Some recordings will sound better, some worse with every adjustment. The only reasonably achievable goal is to try to faithfully reproduce what was recorded. That's about as good as your system can possibly get and no more.

 

 

I agree that the best one can do is to faithfully reproduce what was recorded. And, if your system is neutrally accurate, to the sound of real un-amplified music, then generally speaking, it will faithfully reproduce anything you play through it. 

[gmgraves]

14 hours ago, Ralf11 said:

By that 'real' do you mean only wooden instruments?

 

brass instruments came later and required some rustic metallurgy.

 

or only acoustic instruments?

 

or just excluding synthesizers, but allowing electrically amplified instruments?

 

or??

For "calibration" purposes, acoustic instruments. Where did you get the idea that we were talking about wooden instruments?

[gmgraves]

3 hours ago, Ralf11 said:

must have gotten it from your post, eh?

 

Don't know where. I never mentioned "wooden instruments"