xDuoo MT-603 Pre-Amplifier (tube buffer / audio switch) review

[Chrispy]

Why do you want to tweak with hardware purchases rather than eq?

 

[olds1959special]

Why do you want to tweak with hardware purchases rather than eq?

I just plugged in the Apogee Duet 2 balanced outs to the Fosi ZA3 and the sound is great, I just had to lower the DAC output to -10db

I give up on tube anything for this setup right now.

 

[Chrispy]

I just plugged in the Apogee Duet 2 balanced outs to the Fosi ZA3 and the sound is great, I just had to lower the DAC output to -10db

I give up on tube anything for this setup right now.

Lots of ways to get great sound with today's gear. Tubes are not something I'd want. EQ is more effective than changing hardware generally, tho.

 

[olds1959special]

I am using the SMSL DL200 DAC balanced out instead of the Apogee Duet 2 and it sounds a bit better. Volume set to 70. No more tubes.

 

[SMJH]

Pursuing clean sounding tube gear is a fool's errand in my humble opinion.

Aim for even harmonics dominated THD of around 1~5% for obvious tube saturation 'magic'. This most certainly means very high plate voltages. There, you will feel the tubes 'boiling', 'alive', and reacting properly to input signals. The vocal range becomes seriously boosted and pleasantly warm (like radio hosts), the highs past 5Khz get that typical sizzly distortion, you start feeling reverb tails getting boosted as if you had a compressor/expander active. It's that selective, amplitude-dependent boosting and cutting that creates the typical 'holographic' tube sound in my experience.

The currently available tube preamps and headphone amps are way too clean for any meaningful tube sound. You'll only be getting linear tube frequency response alterations at best. Indeed, even sound demos of beefy looking all-tube OTLs like TA-26S, Darkvoice and the likes prove my point. Yes they sound different (worse) than solid state, but nothing like a properly driven tube circuit.

I am sharing here the distortion graph of an extreme example of a DIY 12AU7 design with high plate voltage of mine, with gain turned all the way to the maximum.

This is quite excessive, but it is to demonstrate the possible harmonics range all with very low noise floor. By turning the gain knob down and compensating with the volume knob, you can get a very musical experience with H2-dominated distortion in the neighborhood of -60 to -40 dB, a sound that's quite honestly impossible to get even with the latest and greatest Fabfilter and NAM tube emulation/saturation VSTs on the computer. I've tried for months... Yes you can get the harmonics on point, but other aspects fall short.

Sorry for the long, practically blasphemous post praising distortion. But hey, one can appreciate both a super honest, clean SS as well as a sizzling tube tearing through their signal chain, which, tl;dr, is pretty much non-existent with modern tube designs.

 

[Billy Budapest]

My intention was to share the joy of what I'm experiencing. I posted to a few forums about this. I know ASR is not that tube friendly, and is more into measurements than subjective descriptions, but I didn't think it would hurt to post about this. Maybe there is someone out there like me who has a very

ASR isn’t what I would call “tube unfriendly,” it just isn’t friendly to tube equipment that adds drastic amounts of noise and distortion.

There are tube amplifiers that measure well—the McIntosh MC275 comes to mind.

Personally, I believe that the “euphonic distortion” argument for tubes is a myth. Any distortion products at normal listening volumes would be inaudible. What people are hearing instead is rolled off frequency response at the high and low ends of the spectrum, and poor damping factor leading to complaints of “looseness” in bass. Perhaps there is dynamic range compression at work too—the so-called “tube saturation.”

And when tubes are not fully warmed up, the distortion can be high enough to be audible. That can result in an “old-timey” midrange-heavy kind of sound that is hard to describe, but you know it when you hear it. However, this sound disappears after a few minutes after the tubes have reached their correct operating temperature.

If a listener likes this “tube” type of sound, that’s fine, but it’s not authentic to the source material, which again is fine if that is your preference. However, everything that’s achievable with tubes can also be achieved through use of EQ.

 

[olds1959special]

ASR isn’t what I would call “tube unfriendly,” it just isn’t friendly to tube equipment that adds drastic amounts of noise and distortion.

There are tube amplifiers that measure well—the McIntosh MC275 comes to mind.

Personally, I believe that the “euphonic distortion” argument for tubes is a myth. Any distortion products at normal listening volumes would be inaudible. What people are hearing instead is rolled off frequency response at the high and low ends of the spectrum, and poor damping factor leading to complaints of “looseness” in bass.

If a listener likes this type of sound, that’s fine, but it’s not authentic to the source material, which again is fine if that is your preference. However, everything that’s achievable with tubes can also be achieved through use of EQ.

My interest in this piece of gear lasted about 2 weeks before I returned it.

 

[Billy Budapest]

Pursuing clean sounding tube gear is a fool's errand in my humble opinion.

Aim for even harmonics dominated THD of around 1~5% for obvious tube saturation 'magic'.

I would think that anything lower than 3% THD would be inaudible, or barely so. But 5%? That would be audible. But pleasant? Unsure.

 

[Billy Budapest]

My interest in this piece of gear lasted about 2 weeks before I returned it.

What’s appealing to me about this piece are the push buttons. xDuoo makes a big deal about the quality of the supplier.