• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Making sense of phono amp measurements

Joined
Sep 3, 2021
Messages
62
Likes
87
Location
Princeton, NJ
I've been reading the phono amp reviews and I am hoping that more experienced members can help me make sense of a few things. (I'll edit this if I have made any mistakes or wrong statements)

1. If the input level is fixed at 5mV (for MM) and 0.5mV (for MC) - which makes sense to standardise on, my basic understanding is that:
- The 1000Hz sine wave Scope chart tells us the Vrms (when calculated from peak-to-peak values) and thus the gain.
- The FFT data is the information used to generate the THD+N Ratio and SINAD. (Which is everything left over after the 1Khz peak has been removed)

Questions:
- I've often heard hiss when turning the volume up when on the Phono input with nothing playing. To compare phono amps in this regard, e.g. the York to the Mani 2, what should I be looking for?
- If all phono amps are tested at the fixed input level, then the resulting Vrms output and Gain when compared between phono amps, could tell us how much you would need to turn up your amplifier to get similar output levels
- How does Gain factor into SINAD? For example, the Mani 2 has a gain of ~44dB and the York a gain of ~40dB, yet the Mani 2 has a better SINAD, and the Mani 2 FFT waveform starts at a level of -100, and the York at -80. So does that mean that if you matched the Gain between the 2, the York's performance would be worse?
- If CD player outputs are spec'd for 2 Vrms, and these phono amps are outputting 500-800Vrms, is that why I always need to inrease the volume on my amplifier to get a similar listening level?

2. Headroom and Pops and Ticks

My understanding is that as the stylus is moving through the groove, and hits some dirt, it will cause it to move beyond what would normally be encountered even from a maximum amplitude encoded signal in the wall - thus leading to a significantly higher output.

The part that I am struggling with is that from looking at the THFD+N Ratio and Generator Level chart, I see the sudden increase at the point that it would said to be clipping.

But why would that mean the pops and ticks will be exaggerated?

(When I think of clipping, I'm imagining a clean sine wave that starts to look more like a square wave - it sounds distorted and bad - I'm just not sure how that would relate to a piece of dirt being hit, which obviously is going to sound bad, where one phono amp has lots of headroom and the other doesn't).

Thank you in advance for any clarifications!!
 

DVDdoug

Major Contributor
Joined
May 27, 2021
Messages
1,143
Likes
1,424
- The 1000Hz sine wave Scope chart tells us the Vrms (when calculated from peak-to-peak values) and thus the gain.
You can calculate it either way. If you get 500mVRMS-out with 5mVRMS-in, that's a gain of 100 (=40dB).

- The FFT data is the information used to generate the THD+N Ratio and SINAD. (Which is everything left over after the 1Khz peak has been removed)
Correct.

The part that I am struggling with is that from looking at the THFD+N Ratio and Generator Level chart, I see the sudden increase at the point that it would said to be clipping.

(When I think of clipping, I'm imagining a clean sine wave that starts to look more like a square wave...)
Also correct. Clipping.

You can clip the output of the preamp (or the output of your power amp) or if you are recording/digitizing, the analog-to-digital converter is hard-limited to 0dBFS and it will clip if you "try" to go over.

A click that's louder than the music can clip when the music isn't clipping. Amir said something about that making the click sound worse, which surprised me!

And a click that loud probably isn't a piece of dirt.. It's probably a damaged record.
 
OP
B
Joined
Sep 3, 2021
Messages
62
Likes
87
Location
Princeton, NJ
And a click that loud probably isn't a piece of dirt.. It's probably a damaged record.

I've been focussing my record collecting on older records that aren't always available on streaming services, and unfortunately, many of them aren't in pristine condition anymore, that's why I'm really trying to wrap my head around this headroom concept to reduce(?) the prominence of disturbances (whether dirt or damage) specifically in relation to phono stages.
 

Balle Clorin

Senior Member
Joined
Dec 26, 2017
Messages
487
Likes
520
Please note the FFT plot done at home with pc and sound card does show you a better than true Noise and SINAD, Google FFT gain…
 
Last edited:
Top Bottom