Marantz PM6003: what is the "loudness" feature doing in details?

[Mwahahaha]

Hi,

I've recently acquired a Marantz PM6003 amp which works perfectly fine.

I'm curious about what the "loudness" feature is doing exactly on this particular amp.
Is the bass/treble lift level related to the voume control knob position? The actual volume output to the speakers? Nothing (fixed level)?

Which frequency range is impacted by:

• The "Loudness" feature?
• The "Bass" knob?
• The "Treble" knob?

I couldn't find any way to switch the "Loudness" feature on/off using the remote control but I'm able to switch the "Direct Audio" (tone settings disabled) on/off so I'm looking for a way to mimic the "Loudness feature" using the Bass/Treble knobs.

Thank you in advance!

 

[dankik]

I couldn't find a loudness curve for your amplifier, but in the classic Marantz amplifiers the lower and upper frequencies were boosted dependent on the volume control position. The lower the volume, the more boost and at some higher volume level the boost was eliminated. This was performed by the mechanical volume control.
Here is a typical set of curves for a 2270 from http://akdatabase.org/AKview/albums/Marantz/Marantz 2270 Review 2.pdf


Here is some information on the effect of bass and treble controls on frequency response for a PM5003. If, in addition, you turn on the Loudness, it will impart additional boost to the bass and treble (dependant on the volume control position).


https://www.stereophile.com/content/marantz-pm5003-integrated-amplifier-measurements

Here's an excellent reference article that explains the Loudness Control, what it does, and modern DSP implementations.
https://www.extron.com/article/loudnesscontrol_ts



As you can see in the PM6003 schematic, the Loudness button is only a switch that is read by the integrated circuit to see if it is activated. The processing is done in IC61 (Toshiba TMP86FH12MG CMOS 8-bit Microcontroller). Since it is FW, it's hard to tell what loudness curve it is implementing.

 

[Mwahahaha]

Thanks a lot!

This shows the importance of settling the volume on the amp rather than on the phone (I’m using AirPlay to broadcast my music, volume set to 100% on the phone).

If I understand your post correctly, on Marantz systems:

• The “bass knob” setting is centred on 75 Hz, raising by 11 dB on its maximum.
  
• The “loudness bass lift” is flatter and raise bass equally from 10 to 100 Hz then decreases until being zero at 1 kHz. The raising value depends on the volume control knob position.

This being said, it means I can’t mimic the loudness feature bass lift entirely using the bass knob only…

 

[dankik]

Correct. If you had a graphic equalizer you can get closer by increasing at multiple frequencies, but the bass "boost" would not be volume control sensitive like a loudness control.

 

[Mwahahaha]

I’m not really concerned for the volume control thing but more by which frequencies are raised.

My amp RC let’s me engage/disengage the “Direct Audio” feature and subsequently the Bass/Treble knobs impact but the “Loudness” feature is switched off when “Direct Audio” is engaged and its state is not restored when disengaged!

 

[Mwahahaha]

One question: is there a way to analyse (with a laptop) the frequency response of my amp? In terms of wiring, I'm thinking about plugging the audio output of my laptop to an input of the amp and to plug the headphone output of the amp to the mic input of my laptop.

By doing so, I'd be able to analyse precisely the effect of the tone control knobs to mimic the loudness feature as much as I can.