• Registered: 2020-11-16
  • Posts: 23

Topic: Gain matching between ADI-2 and KEF M23 power amp.

Hi there - I have added my RME ADI-2 DAC fs back into my main set-up although it normally sits on my desk. I am looking at a few dedicated pre-amps next week for my main set-up, but before spending more money, I wanted to see how the RME works in this configuration.

The RME is connected via USB from a raspberry pi 4 running ropieee, it has a second source from my Cambridge Audio CXC transport via optical. The RME then feeds my NAD M23 power amp via XLR before finally feeding my kef Reference 1.

The DAC is in auto-ref mode.

I wanted to make sure the gain was set-up correctly. The amp has been set-to low gain mode, which I understand to be 19db.

When I play white noise, and measure via my umik mic I get the following results, with the RME at -30dbr, the volume is 60db in my listening position, at -20dbr, the volume in the listening position is 68db, and at -10dbr the volume is at 77.5db.

Is this gain match optimal? I do have some JTS (-30,-20 and -10db) and some Rothwell (fixed -20db) available.

What is the level I should be aiming for? Any help appreciated.

2 Reply by KaiS (edited by KaiS 2024-05-10 17:27:26)

  • KaiS
  • DAW Mastermind
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  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,524

Re: Gain matching between ADI-2 and KEF M23 power amp.

That‘s simple:

• Play some music the loudest you might ever need.
• Note ADI-2 DAC‘s volume dBr value, (example: -12 dBr)
• Use one of your passive attenuaters with a value set close to this (example: -10 dB).

Now Auto Ref Level can use it’s full working range, optimizing SNR and resolution.


Remark:
The white noise measuments are irrelevant for this purpose, it’s only the practical use with music that counts.

KaiS's Website

  • Registered: 2020-11-16
  • Posts: 23

Re: Gain matching between ADI-2 and KEF M23 power amp.

Thanks @KaiS - I think around -12 to -14dbr is pretty loud, therefore I have put the JTS attenuators in, connected directly to amplifier set to -10db. I have just been sat listening a bit above normal level and its around -8dbr on the RME.

A couple of questions, I think the attenuators should be amp end, is that correct? The main issue is the feel a little unsecure, I might try and get something to slide under them to support them.

I am cautious and aware of potential issues where a DAC is connected directly to the power amp, although not with the RME, is this something to be concerned about?

  • KaiS
  • DAW Mastermind
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  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,524

Re: Gain matching between ADI-2 and KEF M23 power amp.

Yes, the attenuators should be on the amp side.

The reason is:
- They increase impedance, which you don’t want on a long cable.
- On the amp side they attenuate noise that might have crept into to interconnection.


Main thing to watch for:
Don’t plug something while the amp is on, or you might blow your speakers.

KaiS's Website