What Makes a Good RIAA or Line Stage?

Hi Doug,

In a currently running thread on a certain RIAA / Line stage beginning with the letter "E", some very provocative comments were made that are of a general nature.

I fear that this conversation will be lost on the many individuals who have soured on the direction which that particular thread has taken. For the purpose of future searches of this archive, those interested in the "E" thread can click this link.

For the rest of us who are interested in some of the meta concepts involved in RIAA and Line Level circuits, I've kicked this thread off - rather than to hijack that other one. In that thread, you (Doug) mused about the differences between your Alap and Dan's Rhea/Calypso:

... the Alaap has the best power supplies I've heard in any tube preamp. This is (in my admittedly unqualified opinion) a major reason why it outplayed Dan's Rhea/Calypso, which sounded starved at dynamic peaks by comparison.

Knowing only a bit more than you, Doug, I too would bet the farm on Nick's p-s design being "better", but know here that "better" is a very open ended term. I'd love to hear Nick's comments (or Jim Hagerman's - who surfs this forum) on this topic, so I'll instigate a bit with some thoughts of my own. Perhaps we can gain some insight.


Power supplies are a lot like automobile engines - you have two basic categories:

1. The low revving, high torque variety, characteristic of the American muscle car and espoused by many s-s designers in the world of audio.

2. The high revving, low torque variety characteristic of double overhead cam, 4 valves per cylinder - typically espoused by the single-ended / horn crowd.

Now, just as in autos, each architecture has its own particular advantage, and we truly have a continuum from one extreme to the other..

Large, high-capacitance supplies (category 1) tend to go on forever, but when they run out of gas, it's a sorry sight. Smaller capacitance supplies (category 2) recharge more quickly - being more responsive to musical transients, but will run out of steam during extended, peak demands.

In my humble opinion, your Alap convinced Dan to get out his checkbook in part because of the balance that Nick struck between these two competing goals (an elegant balance), but also because of a design philosophy that actually took music into account.

Too many engineers lose sight of music.

Take this as one man's opinion and nothing more, but when I opened the lid on the dual mono p-s chassis of my friend's Aesthetix Io, my eyes popped out. I could scarcely believe the site of all of those 12AX7 tubes serving as voltage regulators - each one of them having their own 3-pin regulators (e.g. LM317, etc.) to run their filaments.

Please understand that my mention of the Aesthetix is anecdotal, as there are quite a few designs highly regarded designs which embody this approach. It's not my intent to single them out, but is rather a data point in the matrix of my experience.

I was fairly much an electronics design newbie at the time, and I was still piecing my reality together - specifically that design challenges become exponentially more difficult when you introduce too many variables (parts). Another thing I was in the process of learning is that you can over-filter a power supply.

Too much "muscle" in a power supply (as with people), means too little grace, speed, and flexibility.

If I had the skill that Jim Hagerman, Nick Doshi, or John Atwood have, then my design goal would be the athletic equivalent of a Bruce Lee - nimble, lightning quick and unfazed by any musical passage you could throw at it.

In contrast, many of the designs from the big boys remind me of offensive linemen in the National Football League. They do fine with heavy loads, and that's about it.

One has to wonder why someone would complicate matters to such an extent. Surely, they consider the results to be worth it, and many people whom I like and respect consider the results of designs espousing this philosophy of complexity to be an effort that achieves musical goals.

I would be the last person to dictate tastes in hi-fi - other than ask them to focus on the following two considerations:

1. Does this component give me insight into the musical intent of the performer? Does it help me make more "sense" out of things?

2. Will this component help me to enjoy EVERY SINGLE ONE of my recordings, and not just my audiophile recordings?

All other considerations are about sound effects and not music.

Thom @ Galibier
Years ago the Library of Congress did a study; they concluded that any laminated media was not/is not servicable as an archival media. IOW any laminated media would fail within years or 2 decades at the most.

Non-laminated (amorphous) media is preferred as it cannot delaminate over time. So far the only examples of this sort of media are LPs and 78s, and the stampers that made them. LPs have a projected storage life that goes into centuries if properly stored!
I can simultaneoulsy monitor AND record the digital RIAA setup with 11% cpu usage. It is not convoluted.
I don't have the patience to read this whole thread, so this may already have been addressed: high capacitance PSs charge "faster", not slower than low capacitance PSs. That is, unless there is some series resistance between them and the rectifiers. High capacitance equates to low impedance. This results in very small conduction angles. The current pulses through the PS transformer in short, high current pulses that cause ringing and generate lots of high freq. harmonics. This is a plus for using minimal capacitance in these PSs. They take longer to charge and draw current though the transformer more smoothly. Both my line stage and phono pre have choke input PSs with minimal capacitance (30uF or less) and rely on cascoded MOSFET CCSs to block the ripple (some of the current supplied to the gain stage is shunted across a resistor to develop the B+ voltage). With the gain stages being differential triode pairs with "stiff" CCS "tails", each gain stage is very isolated from the PS. I mention all this because when Kevin Carter had this phono pre in development he had to dispense with the choke input to have enough B+ to work with. Even with CCSs that have an AC impedance >80M ohms the sound was noticably degraded by the capacitive input PS. Lesson here: PS hash is real and can be an issue with low level signals.
That is why stiff regulation and effective Constant Current Sources are a must. IMO, an effective CCS is one that will create immunity to the supply- independent of the fact that the amplification is fully differential.