• Registered: 2021-10-31
  • Posts: 1

Topic: The ABC's of ADI-2 DAC VOL Control

Hi,

I know nothing about audio-engineering.  I am a programmer.  I tried reading through the manual without much success (have already read page 63 - didn't understand much).  I find the vol control on the ADI-2 very interesting, and I was hoping you can help me understand how it works.  I feel that I don't understand the very basic concepts so I can't even being to understand what is laid out in the manual.  I hope to learn these concepts - it is pretty interesting...

Before my questions here is my setup (as a way to provide context - sorry if it is not helpful):
* PC hooked up to ADI-2 DAC via USB
* ADI-2 DAC connected to (integrated) Hegel 190 via balanced output
* (not sure if this helps) but I have atc 40 (passive) speakers

When I adjust the main volume control on the ADI-2 a couple of things (that I can see) start to happen:
* dbr measurements changes in +/-0.5 steps
* dbu measurement changes in steps of +/-6 (at certain dbr thresholds)

WHAT is DBR:
--------------------
* I learnt this morning that decibel can either be an absolute value or express change in value.  I assume dbr is displaying change in value. 
* What does 0 dbr signify?  Does it mean that at 0 dbr the DAC is not changing the volume and the signal is just being passed to my amp?  or  0 dbr is the loudest level before distortion kick in?
* Currently I have it set to -15 dbr...what does that mean?  Does that mean the DAC is changing the volume to less than the reference setting?

WHAT is DBU:
--------------------
* Regurgitating what I've read dbu relates decibel to voltage...simply put higher dbu means more voltage?
* if dbu describes the relationship of decibel to voltage then why doesn't the dbu change (in 0.5 steps) as I change the dbr (in 0.5 steps)?
* In the manual they mention that there are 4 discrete dbu settings to realize full dynamic range.  I listen mostly to classical music, and in orchestral works the dynamic range can be large.  Is there an optimal dbu for balanced output & my-amp?

What is the best way to set & change the volume for the system?
---------------------------------------------------------------------------------------
* Since I'm using RME as a DAC, my amp is just receiving analog input, so (I am guessing) the amp's vol knob controls how much power is sent to the speakers.  But changing the vol on the DAC also effects how loud the final output is...
* What is the best way to set & change the volume for system? 
* Should I set the dac vol to dbr/dbu that is 'optimal' for my system, then use the amp vol control to adjust the volume level?

Thanks in advance for your patience and help.

  • Registered: 2019-01-07
  • Posts: 1,462

Re: The ABC's of ADI-2 DAC VOL Control

Baba!

What's the issue?  Turn the Vol control Clockwise to make it Loud.  Opposite to make it Quiet.

Where then do you find your preferred Vol Setting?  This isn't Rocket Science! 

This matter has been discussed no fewer than 1.21 Giga Times.

The Forum "Search" tool is really cool!  Try it!

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes

3 Reply by KaiS (edited by KaiS 2021-10-31 22:15:21)

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,152

Re: The ABC's of ADI-2 DAC VOL Control

dBr is displayed if “Auto Reference Level” is active, else you see straight dB (without r).
dBr is related to the maximum reference level of ADI-2 DAC.
dBr is controlled in the digital+analog domain.

dBu relates to 0.775 V (the strange value originates from historic analog phone lines).
ADI-2’s dbu display is one of the 4 level steps “Auto Reference Level” has switched in the analog domain.
[The real voltage is for the RCA, on the XLR it ‘s 6dB higher than the displayed value].

With this smart 2 stage design, quasi-continuous digital- combined with a 4 stepped analog volume control, ADI-2 maintains an almost full usage of it’s DAC chip over a 24 dB volume control range.


Look here how to set this up.
(With your typical setting of -15 dBr you’re already at the right point):
https://forum.rme-audio.de/viewtopic.ph … 21#p161721

KaiS's Website

4 Reply by Johannes AU (edited by Johannes AU 2021-11-01 08:02:23)

  • From: Hongkong
  • Registered: 2021-06-30
  • Posts: 720

Re: The ABC's of ADI-2 DAC VOL Control

Curt and KaiS are both correct.

And I jump in to explain it in a layman way and terms.

I am a novice few months ago, in the old days, we use RCA as interconnects and almost foolproof by just connect the equipments and it works.

Today some comes with XLR balance connects, like the RME and your Hegel.

RCA is a typical 2V device, XLR is double, 4V.

An RCA 2V device equals to 8.23dBu,and XLR is 14.26dBu, which is approx. 6dBu more.

The display of the RME dBu value is for RCA, you have to take into account at XLR it delivers 6dBu more, got it?

Then at RME Auto Ref  set to "on", you turn the volume of the DAC to 13dBu minus 4.5dBu, then is good for RCA, also for XLR in general.

Playback and listen to a track, turn up the volume of the Hegel from zero to the desired listensing level, then you are good, mark down the volume value of the Hegel and play other source apart from the RME, you will find the loundness roughly the same.

You can adjust the volume of the Hegel higher or lower according to you need. you can also lower the volume at the RME if you want to control it from the DAC, because I do not know the details of the Hegel (their manual is not clear), I do not recommend to turn up the RME more than the value I suggested it above. If you think it is safe to keep it at that level, you can lock the volume of the RME at "Line Out". Headphone and IEM out still adjustable even you locked the "Line Out"

Try it first, come back and ask if you encountered something you are not sure.

Note: as the Hegel is an intergrated Amp, that said it as a pre-amp inside, I do not know the pre-amp input maximum value allowed, so I suggest the above value, same as my Yamaha amp, it states the max. input voltage is 2.4V, I still keep it at 2V to be safe and offers a bit headroom for the RME EQ and Loudness.

Pacifist, dumb, not stupid
Listen music out from a box which sounds
Reading words on paper/ screen
  • From: Hongkong
  • Registered: 2021-06-30
  • Posts: 720

Re: The ABC's of ADI-2 DAC VOL Control

Curt962 wrote:

Baba!

What's the issue?  Turn the Vol control Clockwise to make it Loud.  Opposite to make it Quiet.

Where then do you find your preferred Vol Setting?  This isn't Rocket Science! 

This matter has been discussed no fewer than 1.21 Giga Times.

The Forum "Search" tool is really cool!  Try it!

Curt, yes, indeed.

RME design the DAC as a plug and play unit, just connect it and play a track, turn up the volume gradually and enjoy, thats fun !

For more fun, dig deeper and find more :-)

Pacifist, dumb, not stupid
Listen music out from a box which sounds
Reading words on paper/ screen