[R Giskard]

Quote:

Robot Giskard! I've been waiting to meet you. Well, glad you could make it here despite your obvious lack of organic parts. Whatever the situation, I know that you are watching out for us earthlings.
 
Also, I'm ashamed to hear that prices are even sky high in your time... bugger. We need to get humans into the stars as soon as possible. Personally, I'm probably a spacer though who knows. 
 
Away from Asimov and back to SS, I will be doing proper tests of the outs come Sunday evening and monday morning to see how many headphones at what impedance settings the amp can handle. I have a feeling that it will have little trouble, though again, best listening is done on the same exact headphone models plugged in parallel. 

LOL!! 
Well, I doubt Asimov thought we'd be approaching the 8 billion number so soon but as history has shown us, progress is underestimated in the long run. Be it progress or not, I hope we'll have enough food though it is questionable whtether we have enough even today. Not that I need it, just sayin'. 
 
I will be be looking forward to your further comments. It is an important amplifier I think because there are not so many amplifiers that don't pretend towards symmetrical design and are simply meant for musical enjoyment. Let's see what you discover!
 
Cheers!
Antun

 

[bcschmerker4]

Thanks for the information on an ALO Audio® product to take under advisement for future production-studio additions.  As of 4 August 2013, I'm on the search for a headset for my XONAR®-equipped Asus® CM1630-06, and the Studio Six looks a natural as an upgrade candidate to supersede my current Pyle® PCA-2 stereo power amplifier on the XONAR's® dual-RCA's.  (The stock Texas Instruments® TPA6120A2 in the XONAR® Essence™ series is driving my requirement for a medium-impedance headset.)
 

 

[mikemercer]

Quote:

nice review, hope to see more impressions on this amazing amp.

I actually reviewed the amp for Positive Feedback!  That's where Srajan got his quote from regarding my wife's reaction:
 
Sonic Satori - ALO's Studio Six Valve Headphone Amplifier...
Class Defining
 
I'm going to be writing more coverage on the amp as I've been doing alot of tube rolling recently!
VERY interesting results thus far:
 
my vintage RCA 6SL7, Sylvania OB2 gas regulators, TUNG-SOL 6V6's, and a JJ power tube seem to aid in getting the most coherent, and liquid-like playback
(so great fluidity without any haze - there's authority, without being over-the-top)
I swear right now this amp is so seductive my wife is starting to get justifiably pissed - as I've been at the desk all the time!!
 

my rig at the LA Head-Fi Meet recently...

 

[shigzeo]

It's almost two weeks in so I decided to run hardware tests on the Six. Since there are four headphone outputs, I hooked up four different headphones with different input specs, different loads, and different sensitivities. 
 
Here's the setup for torture test 1:
 
1x DT880
1x PS500
1x HE500
1x ES10
 
Driven in parallel, each phone runs at full resolution in comparison to test files with no drop in current at any moment no matter square waves, sine waves, or any other test waves. Truly amazing. The Grado and ES10 would have pitched a lesser amp. I even substituted the ultra-low Ω, ultra high-current-necessary Earsonics SM2 for the ES10 and overall response was similar. Again, the Six isn't an earphone amp. You will hear some hum in the signal with earphones, but even lowΩ phones can be driven with great authority from the Six. There is some current drop out running sensitive earphones, but less than any amp I've tried that is in the Six's running.
 
I'm truly amazed. 

 

[R Giskard]

That is certainly interesting. What I would try to do just for the fun of it is connect four highly sensitive low-impedance headphones just to see how the amplifier handles the current draw. 
 
What is the output impedance of the amplifier? I wonder just how much negative feedback runs through the circuit. I suspect it might be quite a lot.

 

[shigzeo]

I don't have a multimeter or a dummy load here. I left that in Korea so I can't give actual numbers but I'm guessing it is pretty low for a full-size headphone amp, 3-8 or so.

 

[Gneiss]

Is the ability to drive 4 heaphones at once a very in demand feature?

 

[shigzeo]

Quote:

Is the ability to drive 4 heaphones at once a very in demand feature?

Good question. I think it would be great for headfi meets. Whatever it is, it is a pretty damn interesting feature. I'm not sure that my house is the place for such a feature. I know that my wife and I have enjoyed dual outs of a few headphone amps. It seems, though, that a number of headphone amps run one or the other. 

 

[yogi1ab]

Quote:

 
What is the output impedance of the amplifier? I wonder just how much negative feedback runs through the circuit. I suspect it might be quite a lot.

 
FYI: Just to clarify, as noted on ALO's website; the amplifier is actually a zero-feedback design: http://www.aloaudio.com/amplifiers/studio-six.

 

[shigzeo]

Quote:

 
FYI: Just to clarify, as noted on ALO's website; the amplifier is actually a zero-feedback design: http://www.aloaudio.com/amplifiers/studio-six.

Thank you for pointing that out. You preempted me.

 

[Gneiss]

Quote:

Good question. I think it would be great for headfi meets. Whatever it is, it is a pretty damn interesting feature. I'm not sure that my house is the place for such a feature. I know that my wife and I have enjoyed dual outs of a few headphone amps. It seems, though, that a number of headphone amps run one or the other. 

 
Interesting indeed. I just wonder if it is supposed to be the selling point of the amp or just a 'why not' feature added on.

 

[shigzeo]

Certainly not. You don't just take on three extra parallel headphone ports. The amp is quite well thought-out, extremely polished, and a very easy platform for rolling.

They designed every in of this thing for sure.

 

[R Giskard]

Quote:

 
FYI: Just to clarify, as noted on ALO's website; the amplifier is actually a zero-feedback design: http://www.aloaudio.com/amplifiers/studio-six.

I wouldn't bet on it and there are number of reasons for that. A zero-feedback design would require substantial (and I do mean substantial) power filtration. As a general rule, transformer output amplifiers employ a good amount of feedback, usually more than 20 dB. This is to cut costs on the size of transformers and said filtration. This also means less control in the bass and more color in the mid-range as well as diminished top end. However, there are variations to this rule depending on tube arrangement.
 
I will ask this though - are there any switches on the front or the back of the amplifier? There might be a feedback switch and if there is, then this amplifier might be zero-feedback but only in it's highest gain setting reserved for high impedance loads.

 

[x838nwy]

I wouldn't bet on it and there are number of reasons for that. A zero-feedback design would require substantial (and I do mean substantial) power filtration. As a general rule, transformer output amplifiers employ a good amount of feedback, usually more than 20 dB. This is to cut costs on the size of transformers and said filtration. This also means less control in the bass and more color in the mid-range as well as diminished top end. However, there are variations to this rule depending on tube arrangement.

I will ask this though - are there any switches on the front or the back of the amplifier? There might be a feedback switch and if there is, then this amplifier might be zero-feedback but only in it's highest gain setting reserved for high impedance loads.

I don't see any said switch/selector in the various photos. However, I never really understand what people mean by 'overall' or 'global' or just normal feedback. May be alo are talking about one and not the other??

 

[R Giskard]

Not really, no. What they should mean is one and the same. But it'd be a lie if I said that manufacturers have only honorable interntions. Hence a lot of false infromation and specifications that really cannot be substantialized with measurements that conform to recognized standards. That makes it a lot harder for the honorable bunch because their products then look inferior on paper. 
 
 am not saying this is the case with ALO but it is something I've encountered too many times.
 
One other question about the headphone outputs - are they all intended for a wide variety of headphones or are they impedance-specific? For example, one output being best suited for headphones with an impedance of 150 - 300 Ohm and so on. Some amplifiers, like the E.A.R. / Yoshino HP4 (4000 Euro), have a similar configuration. If that is the case, then the amplifier doesn't need the feedback switch because each output is configured with a calculated amount of feedback in order to counter the higher current demans with lower impedance loads.