AudiogoN Forums: What Makes a Good RIAA or Line Stage?

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

Thom_mackris (Threads | Answers | This Thread)

02-24-07

Responses (1-50 of 98)

Click title to read one, or click date to read all below it.

02-25-07 Thom, sheesh, i'm glad you didn't title your thread "h ... Dougdeacon

02-25-07 Dear thom: imho the audio device whole design is what determ ... Rauliruegas

02-25-07 Hi doug, do you have any pictures of your system? i think it ... Acoustat6

02-25-07 Hi raul, indeed, holistic thinking is required - both in li ... Thom_mackris

02-25-07 Hey doug, what kind of car should i drive??? o o . Nrchy

02-25-07 Atmasphere recently shared some interesting thoughts on the ... Unsound

02-25-07 Bob, thanks for your interest. i've been promising to post ... Dougdeacon

02-25-07 Nrchy, i didn't know you owned a car. once you've driven a ... Dougdeacon

02-25-07 Other designer's comments? well, i think you guys got it ri ... Hagtech

02-25-07 Hi doug, thanks for the response. i am looking forward to se ... Acoustat6

02-25-07 I have been smitten by tom evan's work for several years. hi ... G_m_c

02-26-07 Hello, my .02 1- there are no perfect supplies or audio ampl ... Ndoshi

02-26-07 . thom, great thread. . doug, nice acceptance speech. . nic ... Cello

02-26-07 Thanks to you designers for posting your thoughts. good one, ... Dan_ed

02-26-07: Atmasphere
The idea that power supplies somehow compare to engines falls apart fairly easily. What if you have large capacitances *and* tight regulation for example?

In addition to excellent power supplies, a good RIAA section will be low noise with as few stages of gain as possible, to minimize distortion. In addition, the best of them will be tube, and passive EQ. Passive EQ allows one to avoid negative feedback, which puts an unnatural 'sheen' on top. Expect first-rate components throughout- handpicked to meet the RIAA curve and for low noise, etc. If on a PCB the material will be something other than FR4 to minimize dielectric effects of the board. Layout will include star grounding for low noise, and attention to RF suppression and improving stability by providing grid stop resistances and local power supply bypass.

I am also of the opinion that since the LP is recorded in balanced mode, and since the cartridge is balanced, that the phono section ought to be balanced too and to that effect we created the first balanced phono preamps in 1989.

The line stage ought to have similar characteristics- simple signal path, zero feedback, quality components, etc. A little understood issue is that the line section is supposed to control the interconnect cable to the point that the cable drops out of the system equation- IOW the cable between the amp and preamp will make little difference. If this is not the case for you your line section lacks this ability.

The volume control will be manual multi-position switch, or if it is remote, a motor drive operating a multi-position switch which is the only way to build up a decent volume control.

Power supplies will be outboard to minimize noise, and locally bypassed for the same reason. I can go on and on...
Atmasphere (Threads | Answers | This Thread)

02-26-07 I cannot contribute to a technical discussion here, but can ... Whart

02-27-07 Whoah, thom! look what you started here. i have to disagre ... Hagtech

02-27-07 A line or riaa stage could be characterized as "good&qu ... Jmaldonado

02-27-07 Jose, or anyone else, have you correlated riaa error to colo ... Dan_ed

02-27-07 Dear dan: absolutely and josé and i already tested about, th ... Rauliruegas

02-27-07 riaa eq deviation no more than 0.05db why? just how many c ... Hagtech

02-27-07 Dear thom: about the line stage and specially in an analog ... Rauliruegas

02-27-07 Dear jh: i respect your point of view and i understand it. ... Rauliruegas

02-27-07 Hi all, it's great to get some brilliant designers involved ... Thom_mackris

02-27-07: Atmasphere
Ok- I have to clear up some misconceptions:

To have true balanced, you need 3 signals. A reference level (return), positive polarity, and negative polarity. A cartridge obviously has only 2 pins per channel.

The reality is, the pins of the cartridge are the inverting and non-inverting outputs of the cartridge. In a differential balanced system, there is no ground signal at all- ground exists only for shielding and it is possible to operate a balanced line without shielding (IOW with only 2 wires...). In this case, the ground wire is the shield and is also the tone arm itself which is shielding the wires.

>>RIAA eq deviation no more than 0.05db<<

Why?

Because if there is an error, it won't be *our* error. You'd be surprised how good the pre-emphasis on older cutting machines actually is. My Westerex system employs hand-picked components to insure accuracy against the serial number of my cutter head.

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.

The balanced source which is the cartridge arrives at the input of the balanced phono section without any transformer. If you refer to my comments above, the inverted ('-' pin) goes to the inverting input (pin 3 of the XLR), the non-inverted output ('+' pin) goes to pin 2 of the XLR and the tone arm ground to pin 1 of the XLR. Very easy, very simple, and nothing 'halved'. The cartridge is normally a balanced source and you get common mode noise rejection like crazy.
Atmasphere (Threads | Answers | This Thread)

02-27-07 Dear thom: +++++ " i too have to wonder about the neces ... Rauliruegas

02-28-07 Thanks ralph (about balanced) ... yours is a different pers ... Thom_mackris

02-28-07 "riaa eq deviation no more than 0.05 db... why?" ... Jmaldonado

02-28-07 The magnitude of riaa error is not particularly useful unles ... Jcarr

02-28-07 Interesting reading, a bit heavy on methodology but the edit ... Ndoshi

02-28-07 Thanks ever so much for visiting this thread, jonathan. you ... Thom_mackris

02-28-07: Atmasphere
Hi Thom, having been in the business of balanced phono production longer than anyone else (since 1989- all the prior balanced phono circuit art were not *production* circuits) I can safely tell you that there is a lot of misconception brought out in the links you provided. I wish I had seen them when they were current!

The advantage of a balanced differential phono section is not that the cartridge will somehow act differently, it is the fact that the cable and the electronics act differently! To take advantage of the improved behaviors, we need to hook up the cartridge itself in balanced mode. This is easy as cartridges take quite naturally to this.

The result is lower noise throughout the phono system. In our case this allowed us to eliminate a stage of gain. That made the preamp more transparent, as it now makes less noise and distortion with wider bandwidth. IOW the signal path is actually simpler, not more complex, quite the opposite of the usual drone of balanced circuits being more complex!
Atmasphere (Threads | Answers | This Thread)

02-28-07 again, your quality sound reproduction targets/priorities ar ... Hagtech

02-28-07 Yes, the beauty of the marketplace is that we all have choic ... Thom_mackris

02-28-07 Dear thom: fortunatelly, like jh told us, there are differen ... Rauliruegas

02-28-07 Dear thom: +++++ " 2. will this component help me to en ... Rauliruegas

02-28-07 Dear thom: this is the subject of your thread: +++++ " ... Rauliruegas

03-01-07 Hi raul, yes, layout is indeed important. jim hagerman is ... Thom_mackris

02-28-07 dan, in my experience the term "coloration" invol ... Jmaldonado

03-01-07 Raul, give it a rest. you're making the same points over and ... Audiofeil

03-01-07 Thom, a replay curve that deviates more from the riaa standa ... Jcarr

03-01-07 Dear thom: with this i'm finish: +++++ " your "it ... Rauliruegas

03-01-07 Raul:you probably mean "truer to the reference riaa de- ... Gregm

03-01-07 Dear greg: you are right. yes, we added the 3.18us pole. yo ... Rauliruegas

03-01-07 Thanks, jonathan. you've filled in the blanks better than i ... Thom_mackris

03-01-07 Dear thom: imho thanks to our quest of exellence in the audi ... Rauliruegas

03-01-07: Atmasphere
Hi Thom, I thought I ought to point somethings out. A phono section needs to be really accurate. Many seem that way, but are not as they add something in trying to be 'detailed'.

I have found that high overload is a good thing. So our MC section overloads at about 250mV so that even a high output moving magnet can't overload it; at overload the output is making over 120V peak to peak.

What happens is that less than perfect recordings can thus still be enjoyed. IOW bad sounding LPs should be utterly playable on the best of systems without a lot of fatigue while the best sounding LPs transport you to the music.

In practice this works and yet our RIAA accuracy is within 0.05%. We extended the curve all the way to 100KHz and the low frequency cuts off at about 1.5Hz, so tone arm resonance defines the lower cutoff. In order to pull this off the power supply has to be very very stiff, and I think I mentioned before that we created a proprietary regulation setup just for this purpose (our regulators are quieter than the 'Super Reg' for example).

Differential amplification comes into play here as differential amplifiers have a 'cross mode rejection ratio' which is an ability to reject noise in the power supply. This is further enhanced by using two-stage constant current sources that are also designed to reject power supply noise.

Overall this gets you is a phono section that is unperturbed by poor recordings. It does seem if a phono section has issues, that often bad recordings will reveal that more than good ones!
Atmasphere (Threads | Answers | This Thread)

03-01-07 "it made perfect sense to compare component colorations ... Cardani

03-01-07 Thom: regarding playback eq deviations, a small width one m ... Jcarr

03-01-07 Hi raul, if i may offer you a bit of friendly advice, and r ... Thom_mackris

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