What's the frequency response of vinyl?

Tafka_steve...I am not sure I completely understood the article, but I think that they cut 61KHz at half speed, which, if played back at full speed would represent 122KHz. That's a lot different from having an actual playback capability of 122 KHz.

A phono cartridge has no problem reproducing signal well below 20 Hz, and that can be a big problem. Both the playback and recording turntables have some "rumble" (LF noise from the bearing) and LPs also can be warped. Many phono preamps have a deliberate roll off below 20 Hz so as to minimize this signal, which would needlessly use amplifier power and cause woofer cones to "pump" in and out with adverse effect on the higher frequencies. Most rumble is vertical groove modulation, and better rumble filters cut this component of the signal, starting at a higher frequency like 30 Hz, without drastic effect on the horizontal groove modulation signal. Little is lost when this type of rumble filter is used because records are usually cut without any LF vertical groove modulation because less-than-audiophile cartriges might hop right out of the groove. Another way of saying this is that LP bass is mono, which is certainly OK for people who use a single subwoofer.

I used to believe that 20KHz was tops, based on microscopic visual groove inspection. However, I now have a spectrum analyser, and although it only goes up to 20KHz it shows that some LPs still have signal at 20 KHz, and the signal level is rolling off with frequency at a rate which suggests it would go to zero in the 30-35KHz range.

If you wanted to test this you could play the record at half speed (some TT will do this) and see what you get. If you saw 20KHz that would mean that the LP grooves had 40KHz wiggles. Whether your cartridge and/or speakers and/or ears could handle 40KHz is another matter.

Tafka_steve...Flat to 100KHz is not a big deal for electronics. I doubt that my Shure V15mr cartridge goes that high, but it would still be sensitive at 35KHz. However, please note that I am inferring the maximum frequency from the behavior evident below 20KHz, a range where the frequency response of the cartridge is not an issue. An analogy would be to estimate the distance of a baseball home run by observing the height and trajectory of the ball as it dissapeared over the fence.

Has anyone done the half speed experiment? That would provide the best answer. 16 rpm turntables are not common, but a 45rpm record played at 33 would give some idea.

Tafka_steve...Whatever you think about the sonic characteristics of Shure cartridges (and other stuff) Shure does an outstanding job of testing and specification. I believe Shure specs. For the V15mr They say "esentially flat from 10 to 25KHz". The graph shows a dip of about -0.2 dB near 16KHz, and then a rise to about +0.2 dB at 20KHz (where the graph ends). The low end is completely flat to 10 Hz.

However, the RIAA curve is only defined from 20 to 20KHz, so phono preamp frequency response can really be talked about only in this range. Outside that range, say up to 100 KHz, a phono preamp can use whatever equalization is necessary for flat response. I said that 100KHz is a walk in the park for electronics. If that were not the case there would be no radios, much less radar or GPS.

My phono preamp is ancient: a PS Audio II. However it is a very simple circuit built with some very good components, and I have never felt the need to replace it. There are but two gain stages with a passive RIAA equalization network in between them. Open loop bandwidth (-3dB) is 120KHz. From 30 to 20KHz it's spec'd at 0.1 dB. There is a rumble filter that brings the response down -0.25 dB at 20 Hz. A "small" amount of negative feedback is applied "for stability and lowered distortion". With feedback the bandwidth is 1.7 MHz, but there is an RFI filter which brings this down to 550 KHz.

I really think that there are more important things than extended frequency response in a phono cartridge and/or preamp. I did like the sound of the MC cartridges which I used, but they didn't track like the Shure, and the Stylus replacement issue was an ongoing headache.