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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.

Cheers,
Thom @ Galibier
128x128thom_at_galibier_design
dougdeacon
3,338 posts
 
Thom,

Sheesh, I'm glad you didn't TITLE your thread "Hi Doug". Opening with a salutation is embarassing enough. Still, I'm glad if my speculation on p-s "goodness" helped spark an interesting thread.

Once I heard the musical clarity of effective power supplies, it became much easier to hear and identify the musical mud caused by ineffective ones. Some are just inadequate. Others are overly complex in the way they're regulated. I don't have the knowledge to explain one vs. the next but I can hear the differences. Anyone could, with a little exposure.

In addition to a starved p-s, another sonic characteristic I've heard in many preamps is a kind of general congestion or confusion of phase timing and frequencies. It sounds (to me) like the result of overly complex designs and, as you already said, too many parts. Being an electrical ignoramus I can't put it any more accurately than that.

I've heard three preamps which don't do this (or rather, which do it notably less than all the others). They come much closer to Bruce Lee, which is a pretty good analogy for my ideal too.

Hope you get some responses from people who actually know what they're talking about. It's an interesting topic.

Doug
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rauliruegas
12,786 posts
 
Dear Thom: IMHO the audio device whole design is what determine which kind of PS do you need.

Which are the voltages/current where the active parts run optimal for the best quality performance, overload margins, we can run those active devices full or at 30% of their specs ( like in the Essential 3150 ), what are the current/voltage needs in the worst stage, cascode source/fountain or not, type of regulation and filtering, how many ps stages, gain stages, needs on output level, distortion/noise levels, chokes or not, whole needs of the whole circuits, separate ps for each " stage " or not, circuit running in class A or what?, ps " power on " all the time or not, etc, etc.

As you can see there are more a lot more subjects than only capacitance. A good ps has to take in count those subjects and many more ( including the ideal capacitance number ) and the " secret " in a good ps design is to optimize any single ps area.

A good audio device design with a bad ps design will sounds bad and a good audio device design with a good ps design will be sound superb.

regards and enjoy the music.
Raul.
acoustat6
357 posts
 
Hi Doug, Do you have any pictures of your system? I think it would help myself and others when we read your responses as to a reference to what you are listening to. Also what are you sound reproduction goals?
Bob
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