ALO Audio Studio Six Reviews and Impressions Thread

Discussion in 'High-end Audio Forum' started by shigzeo, Jul 29, 2013.
  1. Currawong Contributor
    Another interesting swap was an Amperex PQ 6922 with adaptor. The only problem was it rings like a bell, so it, or the adaptor, need physical damping. But it sounds quite divine. It's pretty similar to the VT-231 though, overall.
     
  2. TomSix
    Using the HifiMan HE-6 with the Studio-Six (ST-6) --Some Observations:

    Right up front, let me say that the HE-6 is among my very favorite headphones to use with the ST-6. In particular, the presentation of percussive elements/dynamics and bass performance of the HE-6 is simply incredible.

    As most know, the HE-6 was long seen to be something of the standard reference as a "hard to drive headphone". All over the web can find comments such as "the HE-6 needs at least 5-watts of power" and "the HE-6 requires a loudspeaker amp" and similar.

    It is true that the HE-6 has a considerably lower than average sensitivity of around 83dB. An amplifier needs to have sufficient gain and be able to cleanly swing enough voltage for the HE-6 to play at a satisfying level. it is not really a question of power. As the posted measurements of the HE-6 undertaken by innerfidelity.com show, to produce an SPL of 90dB the HE-6 requires only a power of 19.69 milliwatts.

    If one further looks also at the innerfidelity.com impedance plots for the HE-6, one sees that the impedance stays extremely flat from at least 10Hz to over 20kHz. Such flat non-reactive load impedance is a hallmark/virtue of planar headphones in general.

    Electrically speaking, the upshot is that if an amplifier can swing sufficient voltage, the HE-6 is otherwise a very easy load for an amplifier.

    So why the "hard to drive" reputation of the HE-6? Simple: a good number of headphone amps out there cannot quite swing sufficient voltage into the 50 ohm load presented by the HE-6.

    Can the Studio-Six deliver sufficient voltage swing to play the HE-6 cleanly to a satisfying level? I find that it can. In fact, the Studio-Six has the power to drive even two HE-6s simultaneously to satisfying SPL at low distortion .

    So.... why is there a perception which emerges at times that "the Studio-Six cannot adequately power the HE-6" ? I think there are a couple of factors:

    (1) Because the HE-6 has lowish sensitivity, one ends up using most of the voltage gain (not power) of the Studio-Six to drive the HE-6 to loud SPL levels. This manifests as the fact one needs to "crank the volume knob" up much higher than usual. I personally use up maybe three quarters of the range of the volume control for regular HE-6 listening with the ST-6.

    (2) There is a perception that an amp is "running out of gas" or "pushing hard" when the volume control is advanced near the maximum of it's range --this is not so with the Studio-Six.

    Here are a few excerpted measurements (generated by myself, and published by ALO Audio) of the Studio-Six which are of particular relevance to this discussion:

    Amplifier input Voltage for *full-rated output voltage into various headphone impedances (1,000 milliwatts = 1 watt):

    1.30V RMS input for 5.7V RMS output into 32 Ohms (1,015 milliwatts into load)

    1.70V RMS input for 7.5V RMS output into 75 Ohms ( 750 milliwatts into load)

    1.85V RMS input for 8.3V RMS output into 150 Ohms (459 milliwatts into load)

    *Note: All of the above listed output levels correspond to no more than 5% THD


    THD+N (1kHz input) at 250 milliwatts output into stated impedances:

    32 Ohms: 1.0%

    150 Ohms: 2.0%

    THD+N (1kHz input) at 1V RMS output into stated load impedances:

    32 Ohms: 0.26%

    150 Ohms: 0.12%

    Significant fact gleaned from the innerfidelity.com HE-6 measurements: The 19.69 milliwatts needed to bring the HE-6 to 90dB SPL output corresponds to a voltage swing of only 1.018 Volts RMS.

    What can we make from the above? It becomes clear that the ST-6 can drive much more voltage and power into the HE-6 ( at low distortion) than it needs to play at an average 90dB SPL. There is also more than ample headroom remaining to cover music peaks/transients well above the average listening level.

    Here are a few caveats:

    Standard line-level output voltage from a source is pretty much universally considered as 2-Volts RMS. If your DAC, Preamp or other source can provide at least 1-Volt RMS (preferably a full 2-Volts RMS) to the ST-6, then you should be good to go with the ST-6/HE-6 combo.

    If you want to play your HE-6 at an SPL level that is considered injurious to your hearing, then you will have to pretty much max-out the volume control on the ST-6 due to its gain limits (not power limits). Needless to say, I absolutely advise against listening to music at anything approaching a 90 dB SPL--You will damage your hearing!!!

    To state it all very simply: yes, you can enjoy the virtues of the HE-6 fully with the ST-6, you just have to crank-up the volume control.

    Whew... I sure typed a lot of words just to make that point --Ha!

    Cherish your hearing --please listen at safe levels!

    -Cheers
     
    Last edited: Sep 22, 2017
    sejsel and Currawong like this.
  3. Currawong Contributor
    Ok, this IS a surprise. The Susvaras work out of the Studio Six. Initially when they arrived they had a problem where they sounded like they were clipping out of every amp I had. Turned out it was that the driver needed some hours, where the crackling sound would go away. But after that I never tried them out of the Studio Six again until I read your post. Now I have just shot a video about them and I'm going to have to shoot (part) of it again.
     
    Last edited: Sep 22, 2017
  4. longbowbbs
    The Hifiman Edition X V2's are fantastic out of the ST-6. No problems with plenty of volume either.
     
  5. TomSix
    Indeed, it can at first seem a little counterintuitive. When one needs to advance the volume knob on an amplifier to near full to achieve a loud listening level, the mind is quick to form an initial impression the amp is straining or "running out of steam'. With many amps this is in fact the case, but if an amp has a good margin of headroom, such as the Studio Six, there will not be an actual drive/power problem.

    Admittedly, since the average levels of various recordings can vary quite a bit depending on how "hot" a recording was mastered, at times a markedly "softer" recording which is at a lower average level can require advancing the volume knob of the ST-6 very close to maximum if you want to listen to the HE-6 at a relatively loud level.

    A side note: back when I presented the prototype ST-6 unit to ALO, ironically, about the very first question was: "Ok, but can it drive the HE-6?". That was sort of the gold standard test for HP amp drive capability back then --Ha!

    Back when deciding about the desired gain of the ST-6 during the design process, it was decided that, on one hand, you didn't want so much gain that with really sensitive phones like Grados you would "get blasted" by just barely advancing the volume knob; and on the other hand, one needs at least enough gain to produce a reasonable SPL with the less sensitive phones on the market --such as the HE-6.

    Also: If one designs an amplifier with too high of gain, one begins to run into signal-to-noise problems and headroom/clipping issues. The gain of the ST-6 was purposefully set at a conservatively modest level due to just such considerations.

    Alas, design is a game of compromises :wink:
     
    Last edited: Sep 23, 2017
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  6. sejsel
    ....which could raise a question (taking the Grados and the HE6 as opposite ends of the "spectrum"): was it feasible at any point to consider or implement a gain switch - would that compromise the amp - circuit in any way ?
     
    Last edited: Sep 22, 2017
  7. TomSix
    Indeed, a gain switch would have been be possible, in conjunction with a higher-gain input tube, but there are potential caveats with that too, such as: increased noise; input impedance/capacitance issues; the necessity of using a different input tube (for higher gain) which could have degraded other desired operating parameters...

    "Small" circuit changes can often involve more complexities than initially anticipated.

    Again, design is a delicate balance of compromises :wink:
     
    Last edited: Sep 23, 2017
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  8. MN8372
    Hi all

    I've spent a bit more time playing around with different 6SN7 tubes - which has helped me to better understand the sonic characteristics of each tube.

    I originally started with a RCA Redbase (which was fine - in fact sounded really good as I had nothing to compare it to).

    I then purchased a Tung Sol Black Glass Round Plate on EBay but it was defective (only one channel working).

    So I turned my attention to a Sylvania VT231 - initially I thought it was at the wamer end of the spectrum but I now know that was due to me swapping my headphone cable and not giving the cable (the Lazuli Ref) long enough to burn in and open up (which was a bit silly but I didn't think the cable would make as big a difference as it did). After several weeks of listening I now appreciate that the Sylvania is a very transparent airy sounding tube. I really like it and it opened up the sound quite a bit compared to the Redbase. The sound was just cleaner - truly amazing with some recordings but quite ruthless with poorer recordings.

    I was still hankering after the Tung Sol BGRP though. This time I tracked down one from a dealer (I wasn't going to chance my arm on EBay). I also made sure I didn't change any other components and gave it 40-50 hours burn in before really listening to it. I don't know if you would call it better or worse than the Sylvania. It's maybe not quite as transparent and airy but has the most amazing liquid midrange (but its not muddy or congested). Silky is probably a better way of describing it. It is however different to the Sylvania and I think I prefer it. It is absolutely incredbile with vocal music and also makes listening to brighter pop/electronic music less fatiguing. I've read some comments online that treble detail suffers with the BGRP but that is not my experience. The detail is there - it's just not strident. It somehow cures the sybillance I was getting on some tracks which I knew were well recorded. Everything sounds so natural. Amazing that changing between two (very) high quality tubes can make such a difference. Now if I could just add that last ounce of transparency that I get with the Sylvania it would be perfect..

    Think I need to stop tube rolling now. Keen to see Currawong's video review of the Susvara - especially how it gels with the Studio Six. Not sure if they should be my next buy (which would mean selling the HEK v2) or if I should keep the HEK v2's and pair them with the Focal Utopia.
     
  9. Currawong Contributor
    If you don't listen loud with the Susvara, it can work with the Studio Six. If I try and turn up the volume on the Hugo 2 to make it loud, then I get distortion, so it is still limited to a degree. I don't listen at loud volumes though, so it's not a problem for me.
     
  10. longbowbbs
    I use the ALO Audio Phono Stage as my Phono Pre. Anyone know the minimum cartridge output that it can work properly with?
     
  11. TomSix
    The Studio-Six phono stage should work well with Moving Magnet, Moving Iron or High-Output Moving Coil cartridges of a rated output as low as 1-mV. I suggest 1-mV as the minimum level acceptable. Carts producing 2-mV or above will net a better signal-to-noise ratio.

    What cart are you considering?
     
    Last edited: Nov 10, 2017
  12. longbowbbs
    Dynavector 20X2 or the Soundsmith Carmen.
     
  13. TomSix
    I just looked at the specs for those two carts. Both are rated above 2mV output, and so likely great choices. In truth, the range of 2mV to 5mV is pretty much the "sweet spot" for the Studio-Six phono stage. I'd definitely avoid the low-output 0.3mV version of the DV-20X2, however --that one's virtually guaranteed to be incompatible.

    BTW: haven't you been using a Dynavector 10X5? That cart is known to work very nicely with the Studio-Six phono stage.
    Also: the Nagaoka cartridges work really well too --I can personally vouch for that.

    Finally: the output of the Studio-Six phono *really* likes to feed an amplifier or preamplifier/linestage inputs of around 100K Ohms impedance. It will drive lower impedances down to perhaps 20K Ohms without too much degradation, but increased LF/Bass roll-off and higher distortion will result. Also: the output cables from the phono stage to the amplifier or linestage should be as short as practically possible and of relatively low capacitance too --this will help avoid excess roll-off in the HF response.

    The Phono stage was carefully designed to be very frugal with current draw from the ST-6 amplifier power supply, and so the current drive capability of the output stage is somewhat limited, but indeed mates well with the highish 100K Ohms input impedance of the Studio-Six. A 10K input impedance as found in many solid state amplifiers is simply too low of an impedance for the Studio-Six phono to drive well.

    I hope that was helpful, and wasn't too much of a " tech specs" overload --ha!
     
    Last edited: Nov 10, 2017
  14. longbowbbs
    I do have a 10X5. It is a great cartridge. I am just looking around because that is what we do!
     

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