Pro-Ject Tube Box S2 Phono Preamp Review

[tomelex]

Sounds cool. Please share photos, given your project has materialized already.

 

[tomelex]

Subsonic filters are useful to get rid of the 0.1~2 Hz signal that gets generated by the slight vertical variation in an LPs height. And if there is ANY warp to the vinyl, such low frequency garbage can destroy expensive speakers.

Remember what a phono pickup's job is: to transduce minute motions of the stylus to an electrical signal to be amplified many many times and played through speakers. Some of the movement of the stylus for treble detail is around the wavelength of light in size - REALLY REALLY REALLY tiny motions are converted to electrical signals. So imagine what the cartridge will produce if one part of the LP is 0.01 mm thicker than the other, which variation in thickness it will "ride" every revolution of the record.... The phono pickup will convert this unintended motion into a signal just as faithfully as it does the nuance of Norah Jones' voice captured in the groove.... you don't want this 0.5 Hz "signal" being passed through to your speakers.

YEARS AGO many turntables had rumble issues. The precision of bearings, belts, pulleys, idlers, etc used to create consumer record playback gear was not all that great - these things were built to a price point - and so amp manufacturers often included a "Rumble Filter" in their deluxe units. In those days, gear was based on tubes and the amp circuit and output transformers acted as an unintentional infrasonic filter- transformers are not very good at passing these very low frequencies- so generally a 0.5 Hz "warp" signal didn't make it to the speaker.

Once we entered the solid state era and then after a time more advanced solid state designs came along, it was possible to design amplifiers that worked all the way down to 0 Hz (DC) so now the ultra-low frequency signals from the phono cartridge COULD make it all the way to the speaker and it became desirable to include a high-pass filter in phono circuits. By this time, manufacturing had improved so that even mid-fi turntables had very low levels of actual mechanical "rumble" so the filter was not intended to clean up noisy turntables but to filter out the useless ultra-low frequency junk that gets picked up when playing vinyl.

Vinyl is not a very transparent medium; but people are used to the sound and their brains identify it as "natural" or "musical" sounding. For older audiophiles- who tend to be the ones with money to spend on gear- vinyl sounds like music did in their youth. And for young people, playing vinyl offers a ritual and object-fetish cult that they enjoy. Some day Amirm will measure vinyl playback like he measures a DAC, and you'll see some TRULY awful SINAD.

I would add that it is not totally a ritual for younger folks, there is a genuine sound from vinyl, the distortions can certainly make a two channel playback "sound" better, notice I said sound better, not more accurate to the original signal before it was put on a disc. The whole process adds pleasing arifacts all the way from the original third harmonic producing tape machines, to the cutters inter phase mixing, then the consumers playback selection of the cartridge that "sounds" best to them, and a little bit about the turntable itself. Just adding that in for our young audiophiles information. In fact, I would say the digital does the lower mids down to lowest bass best and vinyl does lower mids on up best, as far as pleasing sound to me through two channel stereo playback.

 

[anmpr1]

... the distortions can certainly make a two channel playback "sound" better, notice I said sound better, not more accurate...

I'd certainly call it different. But there's something else. If you are downloading or trading digits there's nothing really to hold on to. If you are 'streaming' you don't own anything.

I was in a guitar store the other day and they had a record bin. Mostly rock--in fact all rock. I saw Are You Experienced. I had that when it first came out. Picking it up and looking at the cover brought back a ton of immediate but long forgotten memories. There's something about holding a record, splitting the shrink wrap, pulling it out of the sleeve... It's sentimental. I don't deny it. A tea ceremony. Yet it's like Deckard told Tyrell: Memories... You're talking about memories! I don't think I'll ever get that from digits.

Not sure if it's the same 'feeling' for the kid at the store who is just getting in to records. With the Internet it's all changed. We'd put the record on and try and figure out the chords. Pick up the tonearm and reset it as we'd play. Who does that now?

 

[tomelex]

I'd certainly call it different. But there's something else. If you are downloading or trading digits there's nothing really to hold on to. If you are 'streaming' you don't own anything.

I was in a guitar store the other day and they had a record bin. Mostly rock--in fact all rock. I saw Are You Experienced. I had that when it first came out. Picking it up and looking at the cover brought back a ton of immediate but long forgotten memories. There's something about holding a record, splitting the shrink wrap, pulling it out of the sleeve... It's sentimental. I don't deny it. A tea ceremony. Yet it's like Deckard told Tyrell: Memories... You're talking about memories! I don't think I'll ever get that from digits.

Not sure if it's the same 'feeling' for the kid at the store who is just getting in to records. With the Internet it's all changed. We'd put the record on and try and figure out the chords. Pick up the tonearm and reset it as we'd play. Who does that now?

I guess I am sort of an odd man out, I hated listening through whole albums, most had few songs that I really liked, and I always went straight to open reel with the songs I liked then sold the record or gave it away, when I married my wife several "gave away" records came back to me. My open reel deck allowed me to have auto reverse, so I just put on the reel I wanted and listened away for several hours, so for me, storing stuff as digits and not having the art is not that important, but yes, I did enjoy looking over the liner notes etc. I wanted the steak not the sizzle I guess.

 

[anmpr1]

I always went straight to open reel with the songs I liked then sold the record or gave it away....

Back in the day some folks copied records on tape in order to 'save them'. That is, not wear them out. All records had pops 'n clicks, and some folks used half-track machines to edit out imperfections. Where was Audacity when you needed it? But you had to be a high-roller with a lot of time on your hands in order to do that. I read stories of (mostly classical I presume) radio stations doing that.

Quarter track consumer open reel was used to copy records and, as you say, make mixes, but was soon supplanted by cassettes which were 'good enough' and certainly a lot easier to use for mixes. And cheaper. And you could take it to your car. I think the car thing made that format win out as much as any other reason. It certainly wasn't pure fidelity.

I mostly used open reel to record radio programs. My Teac X-10R was good for Met opera broadcasts--except Wagner. Those went on longer than the tape. I soon moved away from pop music and never felt a need to edit classical or jazz programs.

I once splice edited Bruno Walter's Mahler's Second, since IMO most of that is repetitious filler and not very good. Some think he's first rate but I always considered him more a pastiche hack (excepting his lieder work, which is typically better). Anyhow, I cut it down to about twenty or twenty-five minutes-- that to my ears was more coherent. I read somewhere that this release was an edit of four different recordings anyway, mixed together to make one 'performance'. So I just tightened it up a bit. LOL

 

[mhardy6647]

Quarter track consumer open reel was used to copy records and, as you say, make mixes, but was soon supplanted by cassettes which were 'good enough' and certainly a lot easier to use for mixes. And cheaper. And you could take it to your car.

Now that you mention it -- I think it would be really cool to have an Otari MX-5050 in the car...

mono Otari2 by Mark Hardy, on Flickr

 

[anmpr1]

Now that you mention it -- I think it would be really cool to have an Otari MX-5050 in the car...

I don't recall Otari in the consumer space. I've seen 3--one in a college radio station, another in a small studio, and another in a pawn shop. Definitely one of the sturdier looking pieces of open reel gear.

 

[mhardy6647]

I don't recall Otari in the consumer space. I've seen 3--one in a college radio station, another in a small studio, and another in a pawn shop. Definitely one of the sturdier looking pieces of open reel gear.

Heh. I had three for a while Ex-radio station decks, and - as they say - rode hard and put away wet.

DSC_9662 by Mark Hardy, on Flickr

Gave two to local friends/audio gurus and kept one (that one pictured before). They are quite rugged and pretty good decks; they can be made into borderline great decks, and -- in the fullness of time -- I will get mine rehabbed. It's good enough for now, though.

 

[magicscreen]

That's OK, they love you.

 

[RaphaelMabo]

Having polystyrene caps near a heat source is not a good idea for long term reliability.

@amirm What are the tube types? That may help us in guessing the input impedance, critical for MM operation.

The tubes are JJ Electronics 12ax7/ecc 83. Re-branded as Pro-Ject. They are not in the input stage but in the output stage. The input stage is JFET’s.

The input impedance is selectable between 10 ohms, 100 ohms, 1 kohm, 2 kohms and 47 kohms.

The basic input capacitance is 47 pF. Then one can get 147pF, 267pF, 367 pF, 487 pF and 587 pF.

I have this little Tube Box S2 and I like the sound.

 

[RaphaelMabo]

FTFY. With a starting point likely to be a minimum of 150pF, that throws those numbers off significantly.

No. The basic input capacitance is 47 pF. This is with all capacitance settings set to off. If you then turn on first switch then it adds 100 pF so you get 147 pF. If you turn off first switch and turns on the next swith that adds 220 pF you get 267 pF, and so on. With all switches on you get 587 pF.

 

[SIY]

The tubes are JJ Electronics 12ax7/ecc 83. Re-branded as Pro-Ject. They are not in the input stage but in the output stage. The input stage is JFET’s.

So the tubes are basically just decoration.

 

[RaphaelMabo]

So the tubes are basically just decoration.

No. If you read the first post in this thread you see that it gives an effect on the signal the same way as tube amplifiers do. So not just decoration. They do affect the sound.

 

[SIY]

No. If you read the first post in this thread you see that it gives an effect on the signal the same way as tube amplifiers do. So not just decoration. They do affect the sound.

I did, but saw nothing there specific to tubes. Nor anything in the distortion spectrum shown to be audible.

 

[RaphaelMabo]

I did, but saw nothing there specific to tubes. Nor anything in the distortion spectrum shown to be audible.

Then please allow me to quote the first post:
”
SINAD is mainly determined by the "tube 2nd harmonic distortion" to the tune of -72 dB. Add a bit of noise to it and you arrive at our SINAD of 69 dB. This naturally ranks near the bottom of our rankings.
[…]
Distortion versus input level is again "tube like" with proportional rise and without hard clipping until the end.”

I’m sorry that you have listened to the Tube Box S2 and didn’t find the tube character audible. Then I guess we simply has different ears. I do like and enjoy the character and the added texture and extra richness it gives to sound. And I have excellent ears, as have been proven in medical tests.

 

[SIY]

Then please allow me to quote the first post:
”
SINAD is mainly determined by the "tube 2nd harmonic distortion" to the tune of -72 dB. Add a bit of noise to it and you arrive at our SINAD of 69 dB. This naturally ranks near the bottom of our rankings.
[…]
Distortion versus input level is again "tube like" with proportional rise and without hard clipping until the end.”

I’m sorry that you have listened to the Tube Box S2 and didn’t find the tube character audible. Then I guess we simply has different ears. I do like and enjoy the character and the added texture and extra richness it gives to sound. And I have excellent ears, as have been proven in medical tests.

Amir is a very smart guy and knows far more about the computer and software end of things than I ever will. He is not particularly expert in analog circuit design, and even less expert in tube design, so his speculation there outruns his data.

I assume you did controlled comparisons to validate your audibility claims. Could you please provide the procedure you used?

 

[RaphaelMabo]

Amir is a very smart guy and knows far more about the computer and software end of things than I ever will. He is not particularly expert in analog circuit design, and even less expert in tube design, so his speculation there outruns his data.

I assume you did controlled comparisons to validate your audibility claims. Could you please provide the procedure you used?

Thank you for asking.
I have the diagnosis autism spectrum disorder, commonly known as aspberger. Part of my disgnosis is that I am oversensitive to stimulis from the senses, including an oversensitivity to sounds. Scientific studies shows that 8 out of 10 with autism spectrum disorder has an oversensitivity to some or more stimulis. Common is an oversensitivity to sound, physical touch, light, smell and/or taste. I have a milder form of the medical condition known as hyperacusis. I won’t go in deep explanation what this means, but it basically means that the filter in my brain that sorts out sounds isn’t working according to the norm and it let through more sounds than for most others. Our ears are a fantastic instrument, we all pick up a lot of sounds - but it’s the filter in the brain that sorts out which sounds that we becomes aware of. And the filter in my brain is letting more sounds coming through.
So when someone claims ”it isn’t audible”, I do react. I know for sure that things are more audible for me than for many others.
It’s regarded as a ”hearing disorder”, or ”disability”, but it just differs from the norm. I don’t like the words ”disorder” or ”disability”. It often gives an idea of ”being leds capable off” something. But they are used when one differs from the norm.

So I do trust my ears, when there’s a difference - I will definately hear it.

The Tube Box S2 is basically a Phono Box Ultra with tubes. So to find out what the difference the tubes are doing, one must of course listen to both in an A/B comparison using the same source and music.

Digging deep in, listening deeply on one lengthy set of music several times and doing notes about the bass, the midband and treble. The soundstage. The definition of notes. The transient response. Listening to the track several times and listening with focus on different sounds the music.

After spending, let’s say 30 minutes with one unit, then swith to the other unit and doing this again.

It’s good to have a paus in between, 10 minutes to unload the mind.

Then repeat this procedure. Do it at least three times. For each repetation use different music.

 

[SIY]

Thank you for asking.
I have the diagnosis autism spectrum disorder, commonly known as aspberger. Part of my disgnosis is that I am oversensitive to stimulis from the senses, including an oversensitivity to sounds. Scientific studies shows that 8 out of 10 with autism spectrum disorder has an oversensitivity to some or more stimulis. Common is an oversensitivity to sound, physical touch, light, smell and/or taste. I have a milder form of the medical condition known as hyperacusis. I won’t go in deep explanation what this means, but it basically means that the filter in my brain that sorts out sounds isn’t working according to the norm and it let through more sounds than for most others. Our ears are a fantastic instrument, we all pick up a lot of sounds - but it’s the filter in the brain that sorts out which sounds that we becomes aware of. And the filter in my brain is letting more sounds coming through.
So when someone claims ”it isn’t audible”, I do react. I know for sure that things are more audible for me than for many others.
It’s regarded as a ”hearing disorder”, or ”disability”, but it just differs from the norm. I don’t like the words ”disorder” or ”disability”. It often gives an idea of ”being leds capable off” something. But they are used when one differs from the norm.

So I do trust my ears, when there’s a difference - I will definately hear it.

The Tube Box S2 is basically a Phono Box Ultra with tubes. So to find out what the difference the tubes are doing, one must of course listen to both in an A/B comparison using the same source and music.

Digging deep in, listening deeply on one lengthy set of music several times and doing notes about the bass, the midband and treble. The soundstage. The definition of notes. The transient response. Listening to the track several times and listening with focus on different sounds the music.

After spending, let’s say 30 minutes with one unit, then swith to the other unit and doing this again.

It’s good to have a paus in between, 10 minutes to unload the mind.

Then repeat this procedure. Do it at least three times. For each repetation use different music.

Autism does not obviate the need for basic controls.

 

[Frank Dernie]

I have the diagnosis autism spectrum disorder, commonly known as aspberger.

Me too.

However I know that a level matched comparison has shown differences weren't actually there in the past.

People with Aspergers often end up in the scientific and engineering community like I did.

 

[avanti1960]

I had the Tube Box DS for a while. Nice construction and sound- the rumble filter worked well to tighten bass response. Swapping tubes was challenging- eventually made some silicone grippers from some measuring cups. In hindsight the stock Tung Sol tubes sounded best.

The key here was the sound stage. Once I heard David Gilmour's guitar burst forth up forward, left and right like a frenzied 3D animated sonic landscape (The Division Bell- "What do you Want From Me") the DS became my tube gateway.