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Blind Test Results: Benchmark LA4 vs Conrad Johnson Tube Preamp

Worth Davis

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Nice write up. I found out by measuring my room that tube gear was not very flat when I switched in and level matched. I wrote target curves matching the tube variance and the nice solid state sounded like tubes. Try it with a umik and rew. No way that preamp is flat like the benchmark.
 

solderdude

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Easy to say for a qualified person. Not that easy to make it properly without ground loops and added noises/buzz and other mistakes made by an amateur without experience. The test is then useless.

It isn't.
When this happens it would be easy to spot in a recording and feedback could be given how to solve this issue.
Besides Matt would be clearly hearing this when he plays back the recording anyway and probably ask where the sounds come from.
It would be a matter of simply recording line level with and without the CJ.
 
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Gorgonzola

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I guess I'm not surprised by those seeking factors that might confound @MattHooper's blind evaluation method. For some it's simply takes a hard sell for them to admit that there can be obvious sound differences in amplification among properly operating devices.

Listening to, rather than simply dismissing, subjectivist audiophiles over many years has convinced me that there is broad consensus about the differences between tube preamps, (including specifically Conrad Johnson), and low distortion S/S preamps, (including specifically the Benchmark), to convince me that the differences they hear are both real and of a specific nature.

OTOH, I grant that many subjectivists are dismissive, for their part, of measurements or any explanations of sound differences that measurements might suggest. My experience here at ASR has corroborated my belief of over a decade than harmonic distortion profiles, particularly that presence or absence of 2nd and/or 3rd order harmonics, is most significant differences in sound impressions. (It is not a matter of tubes vs. solid state.)

Further, my experience listening to audiophiles -- and in the present instance, specifically to MattHooper -- is that many people prefer their sound to have rather high amounts of 2nd/3rd HD to lower distortion options. FWIW, I Personally am NOT one of those people/audiophiles.
 

Soniclife

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It isn't.
When this happens it would be easy to spot in a recording and feedback could be given how to solve this issue.
Besides Matt would be clearly hearing this when he plays back the recording anyway and probably ask where the sounds come from.
It would be a matter of simply recording line level with and without the CJ.
Recordings would be interesting to compare in something like Delta wave, they should show clear differences. Might also be interesting to see what happens if those errors were added to the benchmark version using something like distort.
 

pma

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It isn't.
When this happens it would be easy to spot in a recording and feedback could be given how to solve this issue.
Yes it is easy to analyse and I wrote it because I have vast experience with on-line tests published on internet and analysis of the issues they have in most cases.
- bad level matching
- bad or no time matching
- noise (just noise) introduced by the recording chain
- ground loops introduced by recording chain

Some of the issues are easy to detect, some are not. Anyway the properly prepared test needs both technical knowledge and experience. It is very unlikely that someone who would make his first attempt in this field will make it right.
 

thorvat

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Discussion:

Essentially I seemed to perceive the same sonic differences between the LA4 and the CJ preamp as I did during my sighted tests.
The LA4 more transparent, precise and dynamic; the CJ preamp richer, more relaxed, more "body" to the sound.

An example: A piece of music with an acoustic guitar picking and strumming, bass player, simple drum part, electric guitar doing occasional chords in the background.

The LA4 sounded more "transparent" on such material. The exact tonal differences in the drum cymbals, snare, timbre of the acoustic and electric guitar were separated and untangled, more easy to hear, as were even the slightest differences in reverb applied to each instrument. The LA4 also seemed to have greater dynamic impressions, the differences in force from the drummer, even the dynamics of the acoustic guitar strumming and picking seemed more obvious.
Also, the bass seems both more tight and dynamic - easier to hear the precision with which a bass player is playing for instance.

In comparison, sound through the CJ tube preamp sounded a bit more homogonized, a bit more 'blended together.' However it sounded richer, more full bodied, more "relaxed" both dynamically (a bit like the drummer was more laid back) and in terms of transients and upper frequencies, which felt a bit more thickened, slightly softer and 'easy on the ears.' There was also that "golden glow," this sort of slight altering of the entire timbre of the presentation "lightening" it up, making it feel more "airy" with an upper midrange/lower treble frequency texture that made instruments sound a bit more 'present' in the room. It's a weird thing because it simultaneously gives the impression of heightened upper frequencies for more "it's there" vividness yet at the same time more relaxed and easy on the ears! The bass takes a small hit in tightness, getting a bit bigger and rounder, but depending on the source material, the Benchmark's bass can sound "too much" and the CJs more laid back, or visa versa.

I used Mark Morrison’s R&B track Return Of The Mac for the tests, and it displayed those essential differences
between the preamps.

I really like both presentations for their strengths. Ultimately I have to say the tube sound still grabs me more. "Density" is something I'm always searching for. The impression of something solid and moving air, as much as can be asked for in the stereo illusion. I get more of that with the tube preamp. With the Benchmark LA4 preamp the sonic impression was like "seeing through musical objects with great clarity, almost like X-rays." With the CJ it was a bit more like like "solid objects, snares, voices, guitars, dense and occupying space, not see-through."

That combined with the way the CJ tube preamp seems to both increase the sense of sparkle and presence and texture, a more vivid and slightly to my ears "more real" presentation tonally, while at the same time relaxing and enriching the sound that makes it so easy to crank the volume...it's a hard combination of characteristics that check my boxes for me to give up.
Thank you for taking your time to perform and publish this test.

IMHO the results opened probabyl the most important can of worms that can be opened on a forum like this - and that is "are specs all that matter"?

Obviously you proved that you can hear the difference between those 2 preamps. These are the specs of CJ preamp:

Gain: 26 dB
Maximum Output: 15V
Bandpass: 2Hz to more than 100kHz
Hum and noise: 100 dB below 2.5V output
Distortion at 1.0 v output: less than .25% THD or IMD

So THD is limited with distorion, not with "hum and noise", any you were definitely able to hear it. But from your post you didn't describe the CJ preamp sound as ugly and distorted, instead you used some nice words which let me believe that you like the sound of this pre-amp.
One can speculate that maybe distorion of that preap is mostly made of 2nd harmonic distorion which tends to be quite likeable, but that is impossible to say without knowing the distorion spectrum.

I own class A tube amp and preamp which both offer very similar distorion figures. I listen to it frequently, and very much like you, I would never say that my tube compo sounds worse than my solid state pream-amp combo, which has distorion figures at least 100 times lower. I simply say it sounds different and use similar words that you used to describe what I mean when I say "different".

Once again, thank you for this interesting test!
 

acbarn

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Thanks for doing this and sharing the results, Matt. I really enjoyed reading about your process and preferences.

I guess I’m not at all surprised you could hear the differences in a blind test, and though I prefer a transparent signal chain myself, I’m not surprised you have a preference for the tube preamp. In music production, we often add subtle amounts of distortion to instrument tracks to increase the presence of a particular instrument. Doing so can add some of the characteristics you’ve described in your subjective impressions. My problem with adding an effect like this to the output chain is that it colors every aspect of every recording, all the time, and with no control over the amount or character of the distortion. This clearly isn’t an issue for many audiophiles who enjoy tube amps, but again, the “always on” aspect of this type of device is a non-starter for me.
 
OP
MattHooper

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Sorry, life got busy. I'll get back to this thread when I can.
 
D

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Thanks for the write up, it’s very interesting. I own the LA4 but I just got it and have only done a small amount of critical listening.

I’d like to hear @MattHooper thoughts and whether you think you were lacking anything with the Conrad Johnson? could you not use LA four and be happy with the CJ?

I also have a Tubes4hifi pramp, and I don’t use it all the time, but I find it quite enjoyable. This was custom-made for me, complete with XLR input and outputs, individual L&R gain controls, LED screen for volume level, it really is a nice piece and whisper quiet. Please respond if you have time thank you.
 

DavidEdwinAston

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Following our interactions on other threads recently Matt. I have just looked through this one.
Thank you for a serious attempt to blind test, and post results.
I couldn't do it, and on ASR it is very important.
Cheers.
 
D

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Following our interactions on other threads recently Matt. I have just looked through this one.
Thank you for a serious attempt to blind test, and post results.
I couldn't do it, and on ASR it is very important.
Cheers.
I have had a well respected tube preamp (custom made with XLR in and out6) and a well respected solid-state preamp on an XLR switcher. Level matched by ear only, I quickly A/B’d the two, and found out they sound very similar. In fact blindfold that I doubt I could pick one out over the other it all depends how well the tubes are done, because I’ve heard tube gear that you can definitely hear the coloration. it was a non-scientific test, but proved enough to me that tubes can be done well, or not.
 
OP
MattHooper

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Following our interactions on other threads recently Matt. I have just looked through this one.
Thank you for a serious attempt to blind test, and post results.
I couldn't do it, and on ASR it is very important.
Cheers.

Thanks, I appreciate it! Cheers!
 
OP
MattHooper

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Thanks for the write up, it’s very interesting. I own the LA4 but I just got it and have only done a small amount of critical listening.

I’d like to hear @MattHooper thoughts and whether you think you were lacking anything with the Conrad Johnson? could you not use LA four and be happy with the CJ?

I also have a Tubes4hifi pramp, and I don’t use it all the time, but I find it quite enjoyable. This was custom-made for me, complete with XLR input and outputs, individual L&R gain controls, LED screen for volume level, it really is a nice piece and whisper quiet. Please respond if you have time thank you.

Hi,

I think this thread gives some context for any individual reading it, to judge how much credence he'll put in to my observations. With that said...

The LA4 certainly isn't "lacking" anything. It's just transparent. But I could say it does 'lack' certain things in the sense of comparison to the CJ tube preamp. It's like if you are served your order of blueberry pancakes. It's not "lacking" anything. Unless of course you like adding whipped cream to your pancakes, then the original order might be seen to be a bit lacking. :)

The CJ preamp has remained routed through my LA4 all this time, allowing me to switch between the LA4 alone or going through the CJ, with my remote from the comfort of my listening sofa. I'm switching between them all the time because the difference I perceive is so fascinating. Typical of this was listening to some digitally-streamed music last night. One piece had a trumpet way off in the distant right of soundstage, a guitar lightly strummed slightly to the left of that trumpet, the drummer playing a light pattern on the cymbals, occasional snare. Using just the LA4 there was a tremendous sense of "transparency" by which I mean the sense of hearing a super clear view in to the recording, every timbral detail, and since even the most minute bits of reverb were audible, there was a great sense of the recorded acoustic around the instruments. Lovely stuff.

I switched over to the CJ tube preamp and lost a teeny bit of that sense of "transparency" but each instrument seemed to thicken slightly and "solidify." And the tone shifted to a slightly more present "live" timbre. It moved slightly from a "great recording" a more "seeing through the speakers to live instruments playing" sensation. And I love that! Also, I find the CJ premp seems to add more focus to the sound. I don't mean that it has, for instance, better channel separation or is rendering imaging with more accuracy. But the texture and body and vividness added by the CJ seems to delineate instruments a bit more obviously.

Sometimes when I'm doing these comparisons I'm using the level matched settings I used for the blind test. But otherwise I'm just doing casual listening, switching between the LA4 and CJ, so sometimes I'll switch to the CJ and the sound level will be quieter, or similar, or louder than the LA4. The volume difference doesn't seem to matter - the difference in character I just described seems to always be there. FWIW...

So in terms of the CJ "lacking" and "could I live with just the LA4?"....

The CJ lacks the sense of absolute clarity and nuance of the LA4. I appreciate the LA4 every time I use it. But I also like what the CJ seems to add.

So at this time there's no way I'm giving up either preamp!

But if someone put a squirt-gun to my head demanding me to choose only one, I suspect I'd choose the CJ preamp. A sense of density to the sound is one of my main goals for my system, and it would be very hard to give that up (along with other aspects of the CJ presentation I like).
 
D

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Hi,

I think this thread gives some context for any individual reading it, to judge how much credence he'll put in to my observations. With that said...

The LA4 certainly isn't "lacking" anything. It's just transparent. But I could say it does 'lack' certain things in the sense of comparison to the CJ tube preamp. It's like if you are served your order of blueberry pancakes. It's not "lacking" anything. Unless of course you like adding whipped cream to your pancakes, then the original order might be seen to be a bit lacking. :)

The CJ preamp has remained routed through my LA4 all this time, allowing me to switch between the LA4 alone or going through the CJ, with my remote from the comfort of my listening sofa. I'm switching between them all the time because the difference I perceive is so fascinating. Typical of this was listening to some digitally-streamed music last night. One piece had a trumpet way off in the distant right of soundstage, a guitar lightly strummed slightly to the left of that trumpet, the drummer playing a light pattern on the cymbals, occasional snare. Using just the LA4 there was a tremendous sense of "transparency" by which I mean the sense of hearing a super clear view in to the recording, every timbral detail, and since even the most minute bits of reverb were audible, there was a great sense of the recorded acoustic around the instruments. Lovely stuff.

I switched over to the CJ tube preamp and lost a teeny bit of that sense of "transparency" but each instrument seemed to thicken slightly and "solidify." And the tone shifted to a slightly more present "live" timbre. It moved slightly from a "great recording" a more "seeing through the speakers to live instruments playing" sensation. And I love that!

Sometimes when I'm doing these comparisons I'm using the level matched settings I used for the blind test. But otherwise I'm just doing casual listening, switching between the LA4 and CJ, so sometimes I'll switch to the CJ and the sound level will be quieter, or similar, or louder than the LA4. The volume difference doesn't seem to matter - the difference in character I just described seems to always be there. FWIW...

So in terms of the CJ "lacking" and "could I live with just the LA4?"....

The CJ lacks the sense of absolute clarity and nuance of the LA4. I appreciate the LA4 every time I use it. But I also like what the CJ seems to add.

So at this time there's no way I'm giving up either preamp!

But if someone put a squirt-gun to my head demanding me to choose only one, I suspect I'd choose the CJ preamp. A sense of density to the sound is one of my main goals for my system, and it would be very hard to give that up (along with other aspects of the CJ presentation I like).
I definitely get what you’re saying, but I doubt there are many people that listen that closely. But for those of us that do, I can relate to what you’re saying about the thickening of instruments, and I don’t know if that’s a little more distortion in my tube preamp, or if it’s just a characteristic of my preamp. There are times when I have switched between a solid state and tube preamp, only to find more similarities than not. But I will say that I agree with the fact that the tube thickens things up a little bit, and the low end just has a little more hefted to it. With mine (Tubes4hifi SP-14) it has more similarities with salad state than not.

Let’s not forget about the cool factor Mr. Hooper, there’s something to be said about the technology when it’s done correctly.

I only received my LA4 yesterday and after less than 24 hours with it I found one thing to be true… You better have a good recording because if not it’s going to expose it’s flaws. Thanks for the detailed reply, and I appreciate you putting a lot of thought into your response.
 
D

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If the tube gear is done correctly, ideally you would not hear a difference. I think tube distortion in a modern tube preamp should be a thing of the past.

I wanted to add that in my own set up, I have heard differences between my tube preamp and my solid-state. But I had the solid state AVP leaned out a little bit via it’s built an equalizer. One day I’ll disable everything on it, or put the LA4 and my tube preamp on an XLR switcher.
 
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MattHooper

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Let’s not forget about the cool factor Mr. Hooper, there’s something to be said about the technology when it’s done correctly.

Oh I've often mentioned the "cool factor" in my equipment choice (though I have to like the sound). I loooove the look of my tube amplification. For me most SS amps are boring boxes. I love the connection with the technological past, the concept that I'm actually able to see the musical signal being amplified in the glow of the tubes, etc.

Same with my turntable. I find it far more aesthetically interesting and appealing (including conceptually, how it works) than my little "black box" DAC.
 
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MattHooper

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If the tube gear is done correctly, ideally you would not hear a difference. I think tube distortion in a modern tube preamp should be a thing of the past.

For me that would obviate some of the point of a tube preamp. :)

(I guess there would still be the cool form factor. But if I wanted total accuracy I wouldn't be using my tube preamp in the first place).
 
D

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For me that would obviate some of the point of a tube preamp. :)

(I guess there would still be the cool form factor. But if I wanted total accuracy I wouldn't be using my tube preamp in the first place).
There’s always the coolness factor
I’ll concede that the tubes fatten things up a little.
 

tmtomh

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I can't say with certainty if @MattHooper 's test was done with a level of rigor and precision that would pass peer-reviewed scientific muster. But Matt was open about the fact that this was a best effort and he himself is not claiming that level of scientific validity.

With that out of the way, I don't know with certainty if Matt's results are meaningful, but I am inclined to believe they are. They are consistent with what many folks have reported over many years about the sonic signature of some tube gear - and crucially, those reports seem to have a degree of consistency regardless of whether people prefer the tube sound or the non-tube sound. There are also a number of potential factors that could sensibly contribute to what he heard: the distortion of the CJ amp, the high-frequency response, and I suppose also things like output-input impedance of the CJ-Benchmark connection and the simple fact that he was actually listening only for the additive effect of the CJ being put into the chain, rather than comparing just the CJ with just the Benchmark.

So it's only one data point, and it's not conclusive, but I find it a heck of a lot more probable, and therefore more useful, than 99% of the other listening impressions/tests that folks post on audiophile forums.

Thanks Matt!
 
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