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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
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rauliruegas
13,101 posts
 
Dear Dan: Absolutely and José and I already tested about, the colorations/distortions/degradation are differents depending where in the frequency range are those inverse RIAA eq deviations.
Almost all phonolinepreamps have its own " colorations " other than the RIAA eq but the ones in the RIAA are more " be present at " because any single frequency deviation affects almost three octaves and this three octaves deviation we noted like a coloration, this special coloration is really a degradation to the cartridge signal because those frequency deviation does not exist in the cartridge signal.

One of the first critical and important task in any phonolinepreamp ( is one of the reasons why they exist ) is to mimic in accurate way the RIAA eq, this inverse RIAA eq must be that " mimic/accurate " to be ( at least in this stage ) truer to the recording .

A good phonolinepreamp IMHO has to have a inverse RIAA eq. deviation no more than 0.05db from 20 to 20kHz.

Our Phonolinepreamp RIAA eq deviation spec is: 0.015db but normally we are below that figure. Obviously that this spec not tell us how the audio device will sound, José already explain other very important subjects to have a good quality performance in a Phonolinepreamp device.

Hagtech, I agree with you about the misunderstood when we name " balanced " to a phono cartridge, it is not, our design is fully differential input to output and the connection is " floating ".

Regards and enjoy the music.
Raul.
hagtech
175 posts
 
>>RIAA eq deviation no more than 0.05db<<

Why?

Just how many cutting lathes in the 50's and 60's were built to this specification? And let's put this into perspective by comparing to the average speaker response. Why are speakers allowed 100x more error? Does that make sense?

The key here is that the stereo channels be matched. They need to be very tight. The relative matching is what preserves the spatial cues, soundsage, focus, etc. An absolute error of even 1dB can be reasonable as long as the channels are equal.

Hey, I've been promoting accurate RIAA eq for years, but let's not go off the deep end like the 70's chase for lower THD. What's next? +/-0.00005dB equalization? This is looking to me like its all about marketing.

jh
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rauliruegas
13,101 posts
 
Dear Thom: About the line stage and specially in an analog audio system the whole design has to be very carefully and almost perfect in every single block on the line stage.

When we begin the Essential 3150 Phonolinepreamp design we don't start with the phono stage but with the line stage, one of the reasons was that the signal that comes from the phono cartridge not only has to pass through the phono stage but through the line stage too and at this line stage we have to take care that the signal does not " suffer " any or almost any degradation, from this point of view the line stage is critical at the same phono stage level design and that line stage has to be optimal in all circuit/operation parameters to conserve ( at least ) the same quality performance that comes from the phono stage, very hard to achieve but IMHO this has to be our target about. The people that already hear the Essential 3150 comments that the performance is good not only with analog source but with digital source too.

Regards and enjoy the music.
Raul.
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rauliruegas
13,101 posts
 
Dear JH: I respect your point of view and I understand it.

My point of view is a little different: I'm looking for the best don't distorted/colored sound performance, the high deviations in the RIAA ( as you say ) have to be added to many other deviations in the whole audio system and this means that when the sound comes from the speakers what we are hearing is the original signal plus/with a exponential deviations/distortions added.
What happen if any one of us try to remove or at least take to a minimum all those frequency deviations/distortions in any single link in the audio chain?, IMHO all of us will be nearest to the recording and nearest to the live event: this is my target and this is what we try to do in our designs, nothing less: a very hard task btw but with lovely quality sound reproduction rewards for all of us.

We are starting the amplifier and tonearm design and that is our first target in those designs: we don't care if before or after our audio devices the deviations/distortions are bigger, as a fact this subject is what promote in José and I the Essential 3150 Phonolinepreamp self design.

Regards and enjoy the music.
Raul.
thom_at_galibier_design's avatar
thom_at_galibier_design OP
729 posts
 
Hi all,

It's great to get some brilliant designers involved in this thread (ain't sucking up ... I call 'em as I see 'em).

Whoah, Thom! Look what you started here.

I'm loving this discussion and hope that it will bring light to the general philosophy of how we achieve the goal of a realistic and SATISFYING musical illusion in our homes. I hope this is everyone's goal. Yes, I'm 5 small steps ahead of Doug in this area and miles behind you guys, and that's part of the fun in watching this thread unfold.

Indeed, the automobile metaphor was incomplete at best, but you need to kick off a conversation with a provocative statement. Like all designs, it is the entire system context that is important, as Nick, Jim, Ralph, Raul, and Jose all pointed out.

Jose brought up some great points, but I'm still puzzling through the difference between what Arthur Salvatore would call "noise floor" and "sound floor". My Artemis is not the quietest piece of gear out there (noise floor - it is quiet but not the quietest) and yet it has the uncanny ability to extract musically significant nuance from recordings (sound floor). Other great designs accomplish this differently

I too have read from more than one individual that a phono cartridge is not balanced, but rather floating single ended. Victor Khomenko's (BAT) writings over on Asylum are one source, and I've heard Jim comment about this on several occasions.

If I recall correctly, when you "balance" a phono cartridge (using a center tapped transformer, for example), you don't get the normal 6dB common mode rejection, because you are "halving" the signal in order to balance it. My explanation may not be perfectly clear on this.

I too have to wonder about the necessity of obsessing over small fractions of a dB in RIAA accuracy when in room speaker response varies by such huge amounts. I would agree with Jim however about left vs. right channel balance as far as treatment of the delicate stereo signal and its implications for imaging and such.

Now, I certainly understand that distortions build through the signal chain or through the gain stages in a single component for that matter - that if you were forced to choose in reducing distortions within an active amplification stage, that larger gains would be had by "improving" the earliest gain stage.

Surely you want to address all issues if you can, but the point here relates to the impact cleaning up the signal as early as possible. How much is too much, and when should we shift our focus away from trying to get the RIAA eq. to vanishingly low levels? I suppose the only way to validate this would be to construct an experiment and introduce larger and larger RIAA errors in several different systems.

Cheers,
Thom @ Galibier
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