To LP Listeners: Fozgometer Experiences...

@oldrooney 

Over a decade ago I started digitizing my LPs. I wanted a good ADC. I purchased the one that was the best at that time, the Benchmark ADC1.  It was expensive, about $1K. It was later that I discovered I could also perform measurements. 

The ADC1 has a USB out. I run a USB cable from the ADC1 to my Windows computer. The REW software will recognize it as an input device. And then you are off and running. I use the Spectrum option in the REW RTA function. For initial measurements, I use a fast sweep with middling resolution. For final measurement, I use a high sample sweep and a huge amount of averages. Even this measurement takes less than a minute. But I do enjoy the realtime aspect as I can set  all kinds of things while watching the system response on the computer monitor. I don't have an expensive tower computer. I use a $1K Lenovo garden variety Windows 11 computer. Plain vanilla. 

REW is an incredible tool and it is free!. Anyone serious about making measurements of their gear, should get and learn how to use REW.

You'll need at least 24/96 performance and 32/192 would be even better, but 16 bits will not allow you to see fine details.

The ADC1 is no longer made. Used ones do become available, but cost about as much as I paid new. There are other very capable ADCs available today new. 

There are numerous ADCs available for ripping LPs. I have not used any of them.

I have tried some of the more esoteric ones, such as the Cosmos, but I keep coming back to the ADC1. 

Using a scope for alignment is a very good way to do it. However, nulls can sometimes be 1mV or less, which is somewhat difficult to see on a scope. Using an ADC allows one to peer deeper into your signals. My noise floor is less than -120dBV (120 dB below 1 Volt).. Signals can be as high as needed, up to the saturation of the source. This is a huge dynamic range.

You can get your feet wet using an inexpensive ACD1. Even if the results are crummy, you will learn what you need to improve sensitivity and you'll become familiar with making these measurements. There is no better way to learn how to do these measurements than doing it by yourself, learning all the way. I am still refining my setup and test methods. I consider my test equipment as valuable as my stereo gear and treat them that way.

When I first jumped into this thread, I'd forgotten that @colossalsound had already solicited all the members in another thread. Agenda? Well anyway, apparently the individuals using photography as an example obviously know nothing about that hobby either. For instance @colossalsound said "As I mentioned earlier, azimuth adjustment is very similar to focusing a camera lens. For perfect focus, there is only one exact position.". Yes, if it's only a single static frame and even then, under controlled conditions you have to make sure the fixed lighting you're using has a special power supply to compensate for the variations in line voltage fluctuations because it will change the intensity of the light which will affect exposure, shutter speed, f stop and ultimately your focus while you're setting up your shot. He didn't even mention depth of field! Vinyl is not a still photograph but a moving picture with infinitely more variables thrown in as well. What if your 180-gram album just ended and you plop on a record that is only 110 grams, do you recalibrate the tonearm?

Start with the laquear which is poured over machined aluminum discs from a string of overhead nozzles much like chocolate is poured over Snickers bars as they roll down the assembly line. Do you think that each Snickers bar gets precisely the same volume of chocolate of the same thickness and that each candy bar weighs exactly 1.86 ounces after it's wrapped?

If you playback a vinyl record that was cut to lacquer and you have VU or power meters sensitive enough and read down far enough, and no matter how flat that slab of vinyl you're playing appears the pointers bounce continuously away from their left hand stops constantly (as the stylus traces the unmodulated grooves) at the smallest possible increments. Try that again with a slab of vinyl at least approximately the same weight and apparent flatness cut using the DMM process and see what you observe. That's just a single aspect.

Consider the groves themselves, on a stereo record the left channel is cut at a 45-degree angle to the left of the vertical and the right channel is cut 45 degrees to the right of the vertical. Like the cutting head the stylus and cantilever have to move simultaneously up and down and side to side to traverse the minute features of the groove which can be as small as a micron or smaller. Then consider the cartridge in the head shell and the disparity of both the lateral and vertical forces imposed by the tonearm. Check out some phono cartridge bench test reviews sometime, you can easily see that the cartridge's vertical and horizontal frequency response, separation and distortion numbers have little in common with each other except at 1Khz which may be between .5 and 2 dB which are design centers manufactures want to aspire to. I could go on and on like this but I think you get the picture. Is absolute precision a means to an end or a very good rough approximation? It's never been a perfect format to begin with.

Interesting that no one has mentioned zenith alignment, which is more prone to error from even "high-end" cart manufacturers than azimuth, more difficult to correct and possibly has more impact on sound.

(I understand that wasn’t the question directly related to the fozgo)

Dear Faustuss,

Please note that I never entered into an argument with you or tried to “prove” that your method is wrong or unnecessary. Quite the opposite — I actually supported it and said that it may very well work. I simply mentioned that I would additionally verify it with something like a phase meter, just to confirm that it truly works consistently and can be used as another alternative way of adjusting azimuth.

For some reason, you started picking apart my analogies and concluded that I “don’t understand photography” simply because I didn’t mention depth of field. Fine — if it makes the analogy easier for you, let’s expand it and say we are focusing on a pencil five meters away with a static camera at f/2 rather than f/16, where even a tiny movement of the focus ring becomes much more critical. But why dive into all these secondary specifics? Are we trying to build a philosophical debate full of layered abstractions, or are we simply trying to explain to people when a phase meter makes practical sense and when it may not?

As I already said above: if a sensitive system reacts clearly to these small adjustments, then yes, of course it makes sense. If the system does not reveal such differences — even because of something as simple as speaker placement or room limitations — then the practical value becomes much smaller.

As for VTA changes caused by thicker records: yes, absolutely, a 180g pressing changes the geometry slightly. And I can tell you that some extremely meticulous vinyl listeners with highly resolving systems do compensate for this either by using thinner mats or by slightly raising the tonearm if they have on-the-fly VTA adjustment, so that the arm maintains the same relative position as with thinner records.

Personally, however, on my own system I never heard such small changes as dramatically significant — at least not significant enough to readjust the tonearm for every individual record. Perhaps I was simply less obsessive about this particular aspect. But yes, you are completely correct that the parameters do technically change. I just never felt the need to chase those tiny corrections myself, although some people certainly do — either with VTA adjustment or different mats.

And in general, when it comes to vinyl theory, I’m much more of a practical person. For about ten years I simply experimented with all these things hands-on in huge quantities because it was literally part of my work.

Right now, in my thread, I’m going to post several dozen high-resolution vinyl digitizations from different analog setups. They form a kind of scale — from more successful, better-tuned turntables to less successful ones. Many of the weaker-sounding examples are systems belonging to clients before they came to us, while the better examples are those same systems after setup, upgrades, tuning, and optimization.

By comparing those recordings to each other people can get a rough understanding of the kinds of differences that appeared in the analog chain. It’s a small practical experiment anyone can do.

Later on, I’ll also demonstrate some very specific point-by-point changes: how the exact same setup changes depending on what it stands on, what kind of platform is used underneath it, how the same cartridge behaves on different tonearms, and even how the same belt-drive turntable sounds with a regular belt versus a Kevlar thread drive.

All of these things introduce subtle but real nuances into the sound. And the beauty is that you can simply listen and compare.

Come and listen those DSD fies in about 2 hours:

Audiogon Discussion Forum

@kevemaher Thanks for sharing your experiences, I believe I have equipment to get started.