What Makes a Good RIAA or Line Stage?

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!

"It made perfect sense to compare component colorations to those of concert halls. The language has been in our hi-fi vocabulary for some 30 years. I look at the term modern in a component to be analogous to the frequency bias of many modern concert halls like Avery Fischer. As an aside, I've heard that Portland has a fairly new concert hall that resembles many of the fine halls of the past with more of a mid-bass and lower midrange center of gravity.
Unquestionably, the Essential is Avery Fischer Hall, and I've received quite a few private e-mails to back me up on this. Is Avery Fischer a bad hall? Absolutely not. Do some people prefer the hall in Rochester, NY (can't remember its name). Certainly."
Thom: with all due respèct but your analogy of comparing a concert hall to a phonostage does not make sense to me at all. Certainly as a profesional muscian myself I can tell you that Avery Fisher hall is one of the worst concert halls ever build. The NY philarmonic has been trying to get away from there for years (concerts at Carnegie) although they are stocked there due to the Fisher foundation legal issues. Coming back to Raul,s phonostage imho it will sound as Avery Fisher hall if thats what its feeded but it will also sound as Amsterdams Concertgebouw,or Boston,s Symph. hall(great halls)if thats what is played through it.
The problem with comparing a phonostage with a concert hall is that lets say for ex: The Musikverain in Vienna has sort of a rich full bodied warmth that the Vienna Phil. players have come to adopt as part of their sound and playing tradition; that it in itself some may say that its a colored sound but again its their sound in an aesthetic and artistic conception. The problem comes when you try to convery those same parameters to an electronic component and what comes out of it is going to be a an edited deviation of a VALID artistic coloration.
As for myslef , i,ve rather try no to edit and stay as true to the source and not only in the phonostage where I think counts not as much as with speakers-room.

Thom:

Regarding playback eq deviations, a small width one may indeed be rarely noticed. Wider band deviations will almost certainly be noticeable if you have a more accurate playback curve at hand for comparison (or have experienced one recently), but if said wider band deviation is the best that you have experienced (or some time has passed since you listened to a more accurate network), maybe you won't mind (or notice). However, although I haven't measured the Lamms, I know from my own work that what we perceive as measureable frequency deviations (as would be the case with an improperly designed RIAA network) may not always be so. Component choices, HF bleedthrough via the power supplies, resonances in the RF range all play a role in the perceived frequency balance. For example, although it appears to be accepted knowledge now that different capacitors (or resistors) have their characteristic signatures, the same also applies for active devices (even if they conform to the same nominal spec). If I don't like the perceived frequency balance that I am getting, it is therefore not a problem to change that while keeping the measured frequency response in the audible band the same. The process may involve some trial and error, and it may take me a few tries to get where I want, but it certainly can be done.

Regarding the analogy with concert halls, I get your point, but I am not sure if it is on target. Many instruments have very different tonal balances depending on the angle and distance that you listen to them from, and you need to physically put your ears where the microphones are to verify whether what you think you should be getting is really what is inscribed on the LP or not (and don't forget that mikes have different frequency responses from our ears). I am fortunate enough to have friends who are recording engineers and have allowed me to sit by the microphones (sometimes on a ladder!), tap into the mike feed, go back to a normal seat in the audience, listen to the analog tape master on the same day, and then a few days later, listen to the lacquer masters. Very, very educational. I encourage you to search out opportunities to experience this.

I very much agree with Ralph's comments on the desireability for high overload margin, and I will add that this is needed at ultrasonic frequencies as well as audible ones. Groove dirt and damage played through the cartridge manifest themselves as transient impulses (very high amplitude, very high frequency content) that at least the front end of the phono stage needs to deal with. If the phono stage doesn't have good overload margins and recovery, pops and ticks will be emphasized, so will record noise in general, and this can also shift the perceived tonal balance upwards so everything sounds brighter than it should.

To add another point, good behaviour in the RF region is also desireable, because there is enough energy (particularly in the 500kHz~ 2MHz range) normally reaching the phono stage that, if the phono stage has problems in this range, IMD can result in inharmonic distortions subheterodyned down into the audible range. Obviously, AM radio stations broadcast in this band, and need to be dealt with. However, phono cartridge loading can also generate resonances in this same region. The inductance of the cartridge's signal coils will react with the capacitance of the interconnet cable to create a resonance in the RF range. Let's take a Denon DL-103. Measuring, I get 40.5uH coil inductance. phono cable capacitance 150pF, resonant frequency 1.94MHz. Now let's see what happens to the measured frequency response when we vary the input load resistance of the phono stage. With a load of 47kohm, the electrical response is flat out to 100kHz but starts to rise, and by 1.94Mhz it is about 7dB up. If we say that the correct load resistance is sq.rt. (L divided by C), we get 500 ohms, and while the frequency measurement looks the same as with the 47kohm load, it stays more or less flat out to a -3dB point of 1.77Mhz. Even if we load at 270ohms, approximately half of the optimal 500ohms, the frequency response still stays flat out to 100kHz, and at 1MHz, we are only down by 2dB.

So, even when you give a low-medium input impedance MC various loads, the audible frequencies are not directly affected. The measureable frequency variations are occuring at ultrasonic frequencies. So why do people report major difference in sound when the input loading is altered? IME, HF behaviour of the phono stage and IMD is the answer. IOW, if the phono stage has exemplary behaviour at RF frequencies, whether the triggering source is a radio station or a resonance between the coil inductance and cable capacitance, that stuff will remain at RF frequencies and you won't hear it (at least not easily - grin). But if a sensitive part of the phono stage has performance issues at those same RF frequencies, IMD will make it far more likely that, for example, changes to cartridge loading result in big changes to the sound. And listening while altering the input loading of phono stages with high HF overload and good RF behaviour as compared to those that do not, bears this out (at least in my experience).

Do note, however, that since coil inductance and cable capacitance determine the resonant frequency, with enough coil inductance and capable capacitance, the resonant frequency can drop to within or close to the audible range, and the likelihood of hearing the effects becomes far higher, regardless of how well the phono stage may do at RF frequencies.

If the designer has taken this sort of stuff into account as well as obvious things like an accurate RIAA network and low noise, the greater the chances are that all of your LP collection (or at least more of it - grin) will sound good.

Again, I agree with Ralph that nasty recordings are often a better guide to the real worth of a phono stage than kind ones. Usually, when I am testing or auditioning equipment, I prefer to put on "system-breakers" - recordings that I know from experience have a good chance of throwing a system into fits. None of that sissy audiophile stuff! (^o^).

regards, jonathan carr

Hi Raul,

If I may offer you a bit of friendly advice, and remember ... free advice is usually worth a bit less than what you pay for it.

I know that we have " to fight " not only against limitations in electronic parts, technology limitations but more important than that limitations in the way people think: this is our challenge, 90% or more of the Essential 3150 ( presentations ) were on tube lover audio systems, not an easy task I can tell you.

This is where you need to be patient. You will not convert everyone, and most of those whom you do convert you will not do so overnight.

I think I can state with confidence that each and every one of the designers participating in this thread have the same amount of pride in their product that you do, as well as the vision that they have a unique window into musical reality. I would expect no less.

Fighting the limitations in peoples' thought is one of those Zen paradoxes however. The more you try, the further behind you get.

It's important to take a historical perspective on this - to realize that many great concepts did not benefit the innovator ... until years after their death. Now, none of us are arguing that we like this, and many of us have achieved some degree of notoriety in our lifetimes (still waiting on that 40 foot sailboat), but one still needs to accept the possibility that success (no matter how you define it) may not be in the cards for you.

There are all sorts of reasons why consciousness moves slowly. Certainly, people are slow to move out of comfort zones. Have you ever heard the expression: "whom are you going to believe? Me, or your lying eyes?". You have to accept that people change at their own pace, and you can't force your reality on others. If you push, they will push back.

Oh yes ... the last thing I want to do is to be the "boss" of any thread. I am humbled by the great minds who are participating here.

Cheers,
Thom @ Galibier

Dear Thom: Ok, its done.

Ralph bring here a critical point in the phono stage: high overload, and not only is a good thing but a necessity.

We found that with increment on the overload we can have lower distortion and better quality performance all over the frequency range.

" that often bad recordings will reveal that more than good ones! ", IMHO both could tell us a lot of the performance designs: in a good designs the bad ones will sound " less bad " and the good ones a lot better, the average sound will be " good sound ". In a " bad dsign " the bad recordings will sound unlistenable and the good recordings only " ok ". At least that's what we experienced about, others could have different experiences.

A good design is the sum/add-up of many subjects and the right synergy between them: an accurate RIAA eq per se means nothing if it not coming along: low distortion, low noise, high gain, high overload, high common mode rejection, right lay out, precise ground planes/star grounding, wide bandwidth, low output impedance, right output attenuator/volume control ( by the way this subject is the Aquiles heel in many designs. ), linearity, execution/build design, etc, etc. and many other parameters that you already posted about.

The challenge is to link all those parameters when some of them " fight " one against " other " or when we have to fight with non-linearities or high order harmonics like in the bipolar design that we are using.
Here it is when we have to use not only the technology that we can reach but the experience, know-how and skills that every single designer has and that is different form each other, that's why exist several differences/approach on the Phonolinepreamp designs, some ones better than others or simple differents.

Obviously that any single of us could think that our design is the best one and many of us could think that we can prove it. We think that our design is different.

Regards and enjoy the music.
Raul.