I used my Analogue Productions test LP to set up my new mc cartridge. This is the first use of this test LP for me. I have used the HiFi News Test Record 001 since 1996. It is used sparingly and is in pristine condition. I noticed that the pink noise tracks 2, 3 on side 2 of the AAPT-1 is very much lighter in the bass (below say 500 Hz). I would estimate about 4 dB down. This is consistent with all my carts and phono stages. Has anyone else noticed this? My speakers are 3-way active and are set up to be flat on the pink noise track of the Test CD HFN 020. So, the HFN pink noise test tracks on LP and CD are in good agreement but the AP pink noise shows a bass shelf down. Any opinions on why this is so?
Gross Pink Noise Error in Analogue Productions Test LP
You are right. I borrowed the Analogue Productions Test LP from a friend and found that the pink noise cuts do not have a constant 1/nth octave spectral level below 500Hz. A plot of the spectrum of the so-called "pink noise" tracks that I measured is attached. The 5dB dip is not my analyzer and it's not my cartridge. It's what's on the Test LP.
You are right. I borrowed the Analogue Productions Test LP from a friend and found that the pink noise cuts do not have a constant 1/nth octave spectral level below 500Hz. A plot of the spectrum of the so-called "pink noise" tracks that I measured is attached. The 5dB dip is not my analyzer and it's not my cartridge. It's what's on the Test LP.
Attachments
Good agreement with my measurement. Yours is probably more accurate since I was just providing a heads up (which no one else seems to have commented on). Since the error appears below 500 Hz, the recording curve bass cut EQ is excessive for the AP. I suspect a second order pole at 500Hz instead of the normal first order pole. Using the AP disc to tune an LP based system to be flat would make the bass excessive on normal LP recording. Is this deliberate? I wonder how many cartridge reviews use this test disc?
I have used the HFN 001 Test Record for over 20 years. It has been replaced by Hi-Fi News & Record Review Analogue Test LP HFN 002, which I have not used but it should be at least as good. Pity about the AP test LP. It is not a reliable reference IMO.
There are a number of other discussions of test records around. Searching the relevant forums ought to be worthwhile.
No one said that it would. The discussion is about in-built bass error in the AP Test Record unrelated to any wear issue.
I had a close listen to all tracks and can find nothing as obvious as the -5 dB bass shelf on the pink noise tracks. It is flat and noise free and the hole is centred. Maybe someone will put a scope to it and post measurements of the levels.
Your measurements agree with my 1/3 octave pink noise RTA measurement. I don't have an accurate W&F meter or frequency counter to measure the test tones. Visually there is minimal side-to-side movement of the tonearm. I can't hear obvious wavering of the tones due to eccentricity. My copy of AAPT-1 is 4 years old. It seems like QC has slipped even more. The results reported here and elsewhere undermine confidence in the AAPT-1. I am going to invest in HFN 002.
Just a note to point out that the discrete-frequency sweep is ruler flat from 1kHz to below 20Hz. So, whatever is responsible for the problem with the pink noise cuts below 500Hz, it may be confined solely to the pink noise cuts. Nonetheless, given the cost of the Test LP, the problem with the pink noise cuts is a unexcusable. Additionally, it makes me wonder about the accuracy of the numerous other cuts on the Test LP which I am unable to easily test.
No. I meant exactly what I said. As per the published description "Tracks 7 & 8 are used to calibrate the RIAA low frequency equalizer of a phono preamp.
Track 7 1 kHz to 20 Hz sweep at 0 VU (Lateral). Ideally, the output will be flat across all frequencies. When viewed on an oscilloscope, the amplitude would remain constant during the frequency downsweep."