Thank you for your post and good question, please let us try and elaborate.
There are several general parameters to consider in judging the merit of any hi-fi circuit, the parts used in the circuit and the product that relies on that circuit: (1) subjective performance; (2) measured performance; (3) reliability, stability and user friendliness; (4) price and value compared to competing products of similar performance level.
(1) Above all else, how does the circuit/unit perform subjectively?
The Studio Six is widely received as a unit which provides an exceptionally fine level of music reproduction and delivers a high level of user enjoyment. If we achieved this level of performance using "three sticks and a rock in a shoebox" we still would have met our goal in designing and building the Studio Six.
(2) How is the unit’s measured performance?
Here we see that the Studio Six measures very well. The amp delivers generous levels of voltage to a very wide range of headphone impedances over a quite respectable bandwidth, and with vanishingly low levels of odd-order distortion and noise. The Studio Six circuit demonstrates a high level of merit in terms of measured performance and that is what a good circuit should do.
(3) How is the unit's reliability, stability and user-friendliness?
The Studio Six uses carefully chosen, high-quality and conservatively rated components throughout, which ensures an unusual level of longevity and reliability for the unit as a whole. There are no bias adjustments needed and tube matching is not required. The Studio Six is a 100% tube design, which uses very easily sourced tubes, so it won’t require locating obscure transistors or ICs for repair. These elements together means the ST-6 is a pleasure to own, easy to live with and "cheap to keep" for the long-term.
(4) What is the price and value of the Studio Six compared to competing products of similar performance level?
With the Studio Six circuit, it's sophistication is in it's refinement, not in it’s complexity. The Studio Six is a prime example of a "less is more" approach to audio circuit design with a goal of placing as few amplifying stages as possible between the signal input and the power output of the amplifier. Emphasis was placed on choosing quality amplifying devices (in this case tubes) that have as much intrinsic linearity as possible with very low levels of higher-order, odd-harmonic distortion in particular. Then we carefully implement these individual devices (tubes) into a circuit in such a way that they are functioning individually at desirable operating points, and together as complex interacting/interrelating dynamic elements with as much synergy as possible.
This design approach may sound simple, but in fact it is quite challenging to find suitable complementary parameters and operating points which allow individual circuit elements to work together holistically and thereby achieve an optimum overall result.
Another key element of this design provides the individual amplifying devices (tubes) with very well-filtered and isolated sources of voltage from the power supply. Here, ironically, a "bigger is better" approach to power supply design and transformer ratings goes well with the "less is more" philosophy implemented for the signal-chain portion of the circuit.
There was never a design directive to automatically seek out the most exotic, esoteric or expensive parts available to use in the Studio Six. Our approach was to spend generously and wisely on parts from the higher tiers of quality and performance, while also keeping an eye directed towards seeking parts which possess exceptional "price-to-performance ratio". For example; the highest quality TKD potentiometer, KOA speer and PRP resistors and top quality Teflon tube sockets. In addition, internal wiring is done with our own ALO audio conductors and in places where beneficial, internal components have been cryo-treated with our in house Cryo-Fi process.
Particular attention was given to selecting suitable transformers with generous measured performance ratings. The Studio Six weighs just under 30-lbs, and, impressively, most of this weight is in its transformers and chokes alone. All of the transformers and chokes in the Studio Six are quite conservatively rated and manufactured entirely in the USA and Canada. The output transformers are high-quality and carefully selected for optimum suitability in the Studio Six. The output transformers use high-quality, grain-oriented M6 iron laminations, have a high primary inductance, and are conservatively capable of several times the rated 1-Watt output level the Studio Six produces. This results in superior bass performance with low IMD and harmonic distortion. The output transformers also achieve a respectable high-frequency minus 1-dB rolloff point of 20kHz at full 1-Watt output into 8-Ohms.
The "less is more" sonic virtues of well-designed, zero-feedback, single-ended-triode amplifiers such as the Studio Six continue to set a high-water mark in terms of transparency, fine detail resolution, definition of space and sense of "immediacy", which is challenging to approach by any alternate amplifier design topology, regardless of technical sophistication or complexity.
In the end it is best to simply listen A-B and subjectively compare amplifiers to find the right amplifier for your listening tastes and preferences, and to find the amplifier that has a positive synergy with your prefered set-up. Our ability to listen to these products, to make these comparisons and find that perfect set-up is one of the great things about personal audio. It is also one of the things that helps keeps it fun for all of us.
Ken and ALO team
Edited by KB - 7/18/13 at 9:18am