Mark's 3.18uS tweak

OTL Asylum

OTL, Output Transformerless Amplifier User Group.

0

Yesterday I tryed Mark's phono stage tweak (see "tweaks" section) on my phono stage. I am running my own design that is built around a single Analog Devices AD797 Op Amp per channel. The tweak is simply to let go of the -6dB/oct de-emphasis of the RIAA curve at about 50Khz. I like it.
This has always bothered me: Because of the nature of the RIAA curve, to be able to reproduce a square wave, the rising (and falling) edge ahead of the RIAA filter would need to rise an infinite amount of voltage in zero time. Of course this is not possible; there is some limit at which the cutting head can no longer continue a +6dB/oct emphasis. It has always made sense to me that there needs to be a fourth elbow in the RIAA curve. I just never knew where.
The 3.18uS simply repersents the resistor value times the cap value of the elbow. 6.36K ohms X 500pF = .00000318.
and _____1_____
2 Pi R C = f = 50Khz where Pi=3.14159, R=6.36K, C=500pF

The fun part of hi-fi is when the equiptment can fool the brain into thinking that there is real instruments in the room. This tweak helped that. I am able to hear more of the source of the sound. For example; not just the string, but the bow going across the string, and not just the voice but the crack of the voice box creating the voice.
Buy the way the math of this mod comes out with a 1.6dB rise at 10khz, and a 2.9dB rise at 20khz.
Give it a try.

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Kimber Kable

Topic - Mark's 3.18uS tweak - Paul Speltz 13:45:44 10/03/99 (5)

Re: Mark's 3.18uS tweak - Dan 20:00:04 10/03/99 (3)

Re: Mark's 3.18uS tweak - Paul Speltz 08:21:42 10/04/99 (2)

Re: Mark's 3.18uS tweak - thanks! - Dan 10:32:50 10/04/99 (0)

Re: Mark's 3.18uS tweak - Paul Speltz 08:25:14 10/04/99 (0)

Re: Mark's 3.18uS tweak - like this? - Dan 19:49:11 10/03/99 (0)