A full FFT analysis of this is the ultra-flat frequency response you see above. It starts with a very low level so you likely won't hear it for a while. This allows you to adjust recording/playback level, and detect clipping or distortion by looking for 600hz or 6000hz signs of second-order distortion.50-60 seconds is full band white noise at -20dB, this plays to make sure that frequency response goes above 24KHz (I had a problem where Windows 7 would keep dropping the output sample rate to 48KHz if anything else had played audio)The remaining six minutes is the tone sweep. There's just some negligible aliasing artifacts around 2k.Here is the test tone:0-50 seconds is a 300hz+3000hz+30000hz tone at -1dB (with -0.3 dB modulation every 5 seconds).
As I think I mentioned one other time, there have been moments where I was sure an LP was down about -5dB or so, but the test record showed me it was as flat as can be.Īnalyzing the tone gives me a frequency response graph that looks like this:That would be +/-.0005 dB for you and me.
Click to expand.I have those three, as well as a couple of Stereo Review test LPs from the 1970s and a couple of the HFNRR records.The pink noise passages are useful for checking phase and tracking, and the response sweeps are pretty conclusive. I used to use a HP-400 Meter a pencil and some graph paper to record my results.I have the following test records:CBS STR 100 - Professional Test RecordCBS STR 112 - Square Wave Tracking & IMCBS STR 120 - Wide Range Pickup TestCBS STR 130 - RIAA Frequency ResponceCBS STR 170 - 318-MicroSecond Frequency ResponseShure TTR 102 - Phono Cartridge Test RecordShure TTR 103 - Phono Cartridge Trackability. Click to expand.I've been able to get cartridges that flat as well with my Levinson preamp.
I was floored by how accurate it was.BTW, there are software programs that will just take the raw output of a turntable and apply a 'virtual' RIAA curve to it to apply the correct playback EQ after the fact. What specific test record are you using? If it's a name-brand - CBS Labs had some great ones in the 1960s and 1970s, and even the newer ones from Hi-Fi News & Record Review are good - it should be fine.Every time I've played back the test signals through my Krell KSP-7B preamp, it's flat within about.1dB all the way to about 18kHz or so (the limits of the signals).
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