Phonopre headroom vs. frequency

[AnalogSteph]

So in Amir's phonopre reviews, we can see two types of behavior in this regard:
1. Headroom stays ~constant with frequency
2. Headroom diminishes with frequency

What I would expect to be seeing, however is:
1. Headroom increases with frequency (typical global feedback designs whose gain steadily drops)
2. Headroom stays constant with frequency (e.g. passive RIAA designs with a flat gain stage at the input)

What gives? Is Amir's generator level subject to change with frequency as per IRIAA curve and just normalized at 1 kHz? That would explain it. Fundamentally this approach potentially has its perks (giving a better representation of what to expect with given audio material) but does make things harder to interpret and may lead to confusion.

(BTW, the behavior you generally want is (1).)

 

[pma]

So in Amir's phonopre reviews, we can see two types of behavior in this regard:
1. Headroom stays ~constant with frequency
2. Headroom diminishes with frequency

What I would expect to be seeing, however is:
1. Headroom increases with frequency (typical global feedback designs whose gain steadily drops)
2. Headroom stays constant with frequency (e.g. passive RIAA designs with a flat gain stage at the input)

I have also noticed that, quite long time ago.

Normally I measure, with my phono preamps, constant output clipping voltage with frequency, as shown below. Input clipping level thus of course rises with frequency, this goes without saying.


Another example with Aikido (passive EQ), now oscilloscope plots, yellow is the input and blue is the output. Again almost constant output clipping level with frequency.


This is fully understandable, as long as the output is able to feed current Io = C*dv/dt to the RIAA EQ network.

However, steady state sine wave testing IMO does not tell the story (again). My concern is of preamp response to a click or multiple clicks (cartridge mistracking). Yes they are sharp thus having HF spectrum, but .....

A single click may look like this:

an this is how phono pre responds:

One can see long "tail" settling, because phono pre is a kind of an integrator.



Now, if multiple impulses arrive to the preamp input, output gets saturated due this long LF settling.



Again, not a part of a "common set" of measurements.

 

[Soniclife]

So in Amir's phonopre reviews, we can see two types of behavior in this regard:
1. Headroom stays ~constant with frequency
2. Headroom diminishes with frequency

What I would expect to be seeing, however is:
1. Headroom increases with frequency (typical global feedback designs whose gain steadily drops)
2. Headroom stays constant with frequency (e.g. passive RIAA designs with a flat gain stage at the input)

What gives? Is Amir's generator level subject to change with frequency as per IRIAA curve and just normalized at 1 kHz? That would explain it. Fundamentally this approach potentially has its perks (giving a better representation of what to expect with given audio material) but does make things harder to interpret and may lead to confusion.

(BTW, the behavior you generally want is (1).)

I'm mystified by this as well.

 

[cgallery]

Could it be that op amp gain is inversely proportional to frequency?

 

[nagster]

This is a THD vs GeneratorLevel measurement of the Fosi Audio BOX X5 Phono Preamp.
The first plot without generator EQ was reused from a previous post.

Fosi Audio Box X5 Phono Preamp Review

I still don't understand how this poll is rating the Fosi Audio Box X5 Phono Preamp great when no input MM capacitance is supplied in the specs

www.audiosciencereview.com

And an AP loopback measurement with and without EQ.

The Inverse RIAA EQ used is here.

Fosi Audio Box X5 Phono Preamp Review

There we have it, again. 240uV (10Hz ...22kHz) noise with cartridge, but only 28uV with AP as source, about 18dB worse and SINAD would take a similar hit. ... Finally strict on topic, see below. But here are some blank numbers from my LTSpice simulation at 20°C, as we are dealing with thermal...

www.audiosciencereview.com

 

[nagster]

This is a THD+N vs Generator Level measurement of the Fosi Audio BOX X5 Phono Preamp.
I tried to guess amirm's measurement settings.

Fosi Audio Box X5 Phono Preamp Review

This is a review and detailed measurements of the Fosi Audio Box X5 stereo Phono stage. It was sent to me by the company and costs US $109.99. Company manages to bring a touch of class in a category that is universally utilitarian with those rounded corners and orange power button. Flexibility...

www.audiosciencereview.com

 

[pma]

Frankly, I am not sure that these THD+N vs. level plots at various frequencies are any helpful, regardless X-scale calculation (RIAA or not), to tell us about "headroom" under real overload situation. The only dangerous situation is track mechanical click or mistracking. Let me show you REAL measurements from vinyl record.

Red track is the cartridge voltage output and blue track is the preamp output measured simultaneously. Supraphon #3 measuring vinyl record.

1. Normal situation, groove signal is 80Hz with 40um amplitude:

cartridge output with better resolution:

2. same vinyl record, between the tracks is an unintentional surface click (this may happen with signal as well):

the click:

Anyone would make a meaningful relation to the THD+N vs. level plots at various frequencies???

Note: preamp gain is 36dB/1kHz approx.