Pro-Ject Phono Box DC MM/MC Phono Preamp Review

[Carl-Fosi Audio]

Usually subsonic: below 20Hz, typically 10Hz

So the High-pass filter band is 20Hz?

 

[Rja4000]

So the High-pass filter band is 20Hz?

What do you mean ?
It's a high pass filter.
If cut off frequency is 10Hz, that means it's decreasing level in subsonic frequencies.
Level at 10Hz is -3dB and below that it's decreasing more or less quickly, depending on the filter order.

The goal is to remove unwanted frequencies that may be generated from, as an example, a warped disc.
Those frequencies are unwanted, and can't be heard directly, but may consume amp power and generate unwanted heavy slow woofer moves, and therefore induce audible distortion.
They may even induce a feedback loop, which could be destructive if power is enough.
(A subsonic filter is a must for DJs using vinyl)

 

[AudioSceptic]

Usually subsonic: below 20Hz, typically 10Hz

If you mean the turnover frequency, 10 Hz would be too low as that is where the cartridge/arm resonant peak is often centred. Ideally you want nothing at all below 20 Hz, which means in an analogue system you have to start at 30 or so. Here's a good example <https://www.audiosciencereview.com/...o-mc-pro-phonostage-review.47139/post-1685245>

 

[DSJR]

The unwanted LF will depend a lot on how well the tonearm-cartridge mass is matched to the cartridge compliance and damping. I wonder how well that is understood by those who've joined the "vinyl revival"?

VERY late reply to this (I forgot I said basically the words below some time back ), but from the numerous plots I've seen over the decades, the LF resonance is usually 10dB up or more at usually 10 - 15Hz and all this does is waste power on a wide-range amp and adds intermod distortion in a typical two way box as the cone pumps in and out. In my experience and vibe today, best that sub 20Hz wasn't there

 

[AudioSceptic]

VERY late reply to this (I forgot I said basically the words below some time back ), but from the numerous plots I've seen over the decades, the LF resonance is usually 10dB up or more at usually 10 - 15Hz and all this does is waste power on a wide-range amp and adds intermod distortion in a typical two way box as the cone pumps in and out. In my experience and vibe today, best that sub 20Hz wasn't there

Yes, as Mr Dernie has reminded us, anything below 2x the resonant frequency is rubbish anyway so don't waste any resources at all on sending it out into the system. <https://www.audiosciencereview.com/...-vinyl-playback-discussion.34143/post-2336940>

 

[Nick_Sukhov]

in 2022, in the new (I emphasize, new, not updated) edition of the IEC 60098:2020 Analogue audio disk records and reproducing equipment standard, justice has prevailed, and exactly in the sense that I mentioned above. I quote page 15 [HBC9]: PLAYBACK equipment must comply with FOUR continuous times: 75 μs, 318 μs, 3180 μs AND MANDATORY 7950 μs. Period! Now all phono preamplifiers without 7950 μs are to be thrown out or reworked! The most interesting thing is that on pages 13-14 [FIG. 10-11] of IEC 60098:2020, requirements for standard RECORDING equipment are given, which contain only THREE correction time constants: 75 μs, 318 μs and 3180 μs, which recognizes that all previously released records without 7950 μs are suitable without any reservations, and the 7950 reproduction correction is due to the low-frequency resonance of the head + tonearm. Amen. See more here [ https://www.patreon.com/posts/97802586 ]

 

[morillon]

in 2022, in the new (I emphasize, new, not updated) edition of the IEC 60098:2020 Analogue audio disk records and reproducing equipment standard, justice has prevailed, and exactly in the sense that I mentioned above. I quote page 15 [HBC9]: PLAYBACK equipment must comply with FOUR continuous times: 75 μs, 318 μs, 3180 μs AND MANDATORY 7950 μs. Period! Now all phono preamplifiers without 7950 μs are to be thrown out or reworked! The most interesting thing is that on pages 13-14 [FIG. 10-11] of IEC 60098:2020, requirements for standard RECORDING equipment are given, which contain only THREE correction time constants: 75 μs, 318 μs and 3180 μs, which recognizes that all previously released records without 7950 μs are suitable without any reservations, and the 7950 reproduction correction is due to the low-frequency resonance of the head + tonearm. Amen. See more here [ https://www.patreon.com/posts/97802586 ]

The question is what standard do our more or less old discs correspond to, no? before 2022...

 

[markstein]

Despite what is written within any technical standard - a well engineered low cut filter should be implemented into any phono preamp. I personally would not use one without this feature.

 

[Nick_Sukhov]

Despite what is written within any technical standard - a well engineered low cut filter should be implemented into any phono preamp. I personally would not use one without this feature.

You are right ! https://www.patreon.com/posts/masterklass-po-118530913

 

[Nick_Sukhov]

The question is what standard do our more or less old discs correspond to, no? before 2022...

all disks are recorded with 75-318-3180 , read my last 3 sentences @ #86