• 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!

EQ / DSP and DAC Output Voltage (Question Answered, Thank You).

MattISO

Member
Joined
Feb 17, 2022
Messages
13
Likes
1
If my DACs max output voltage at 0dBFS is 2Vrms and I use an EQ/DSP like Equalizer APO or Roon DSP to boost certain frequencies, then apply a pre-amp gain of -4.5dB to avoid clipping and end up with a peak gain of -0.0dB, would my max output voltage now be ~ 1.19 Vrms?

I want to make sure that my DAC is delivering enough voltage to my amplifier, which has an input sensitivity of 1.5 Vrms.

Used this online calculator.
 

gvl

Major Contributor
Joined
Mar 16, 2018
Messages
3,075
Likes
3,330
Location
SoCal
If after all EQ and pre gain adjustments your resulting digital signal on the DAC input still reaches 0dB/full scale there should not be any voltage reduction on the DAC output.
 
OP
M

MattISO

Member
Joined
Feb 17, 2022
Messages
13
Likes
1
If after all EQ and pre gain adjustments your resulting digital signal on the DAC input still reaches 0dB/full scale there should not be any voltage reduction on the DAC output.
O OK Great Thank You. :)
 

levimax

Major Contributor
Joined
Dec 28, 2018
Messages
1,444
Likes
2,072
Location
San Diego
If my DACs max output voltage at 0dBFS is 2Vrms and I use an EQ/DSP like Equalizer APO or Roon DSP to boost certain frequencies, then apply a pre-amp gain of -4.5dB to avoid clipping and end up with a peak gain of -0.0dB, would my max output voltage now be ~ 1.19 Vrms?

I want to make sure that my DAC is delivering enough voltage to my amplifier, which has an input sensitivity of 1.5 Vrms.

Used this online calculator.
Peak voltage will be the same i.e. 2 volts but only at the frequency with the EQ boost. The music will sound 4.5 db quieter at 0 db than without EQ and digital pre-amp gain reduction. EQ can be a headroom hog for sure. Since digital clipping is a sonic disaster you need to avoid that and the only way to make it up if needed is with additional analog gain.
 
OP
M

MattISO

Member
Joined
Feb 17, 2022
Messages
13
Likes
1
Peak voltage will be the same i.e. 2 volts but only at the frequency with the EQ boost. The music will sound 4.5 db quieter at 0 db than without EQ and digital pre-amp gain reduction. EQ can be a headroom hog for sure. Since digital clipping is a sonic disaster you need to avoid that and the only way to make it up if needed is with additional analog gain.
OK Thank You.
 
OP
M

MattISO

Member
Joined
Feb 17, 2022
Messages
13
Likes
1
Peak voltage will be the same i.e. 2 volts but only at the frequency with the EQ boost. The music will sound 4.5 db quieter at 0 db than without EQ and digital pre-amp gain reduction. EQ can be a headroom hog for sure. Since digital clipping is a sonic disaster you need to avoid that and the only way to make it up if needed is with additional analog gain.
Another question, how would I go about making up the headroom with analog gain?
 

levimax

Major Contributor
Joined
Dec 28, 2018
Messages
1,444
Likes
2,072
Location
San Diego
Another question, how would I go about making up the headroom with analog gain?
Since small amounts of analog clipping are much more benign than digital clipping, depending on your amps sensitivity you can use a pre-amp to boost the signal to your amp. Since it is going to be rare your that the EQ boosted frequency is going to be hitting 0 dB with music you can probably get the loudness back in most cases even if there is a little clipping of the boosted frequencies. Ideally a more sensitve and powerful amp and or pre-amp that has 4.5 dB more output would get the loudness back with no clipping but that is expensive.

One thing I noticed with my system was that even though the room EQ filters I created said they required 5.3 dB of headroom when I ran a 0 dB sweep there was a lot of clipping at some frequecies (very easy to hear... no test equitment required). In order to eliminate the clipping I had to use -9.2 dB of digital gain which is a lot. By adding a pre-amp I was able to get most of the loudness back.

I think testing with a 0 dB sweep is a good check after applying EQ. REW is free and can generate test signals easily.
 
OP
M

MattISO

Member
Joined
Feb 17, 2022
Messages
13
Likes
1
Since small amounts of analog clipping are much more benign than digital clipping, depending on your amps sensitivity you can use a pre-amp to boost the signal to your amp. Since it is going to be rare your that the EQ boosted frequency is going to be hitting 0 dB with music you can probably get the loudness back in most cases even if there is a little clipping of the boosted frequencies. Ideally a more sensitve and powerful amp and or pre-amp that has 4.5 dB more output would get the loudness back with no clipping but that is expensive.

One thing I noticed with my system was that even though the room EQ filters I created said they required 5.3 dB of headroom when I ran a 0 dB sweep there was a lot of clipping at some frequecies (very easy to hear... no test equitment required). In order to eliminate the clipping I had to use -9.2 dB of digital gain which is a lot. By adding a pre-amp I was able to get most of the loudness back.

I think testing with a 0 dB sweep is a good check after applying EQ. REW is free and can generate test signals easily.
O OK, think I get it. I was looking for pre-amps, but could only find phono pre-amps, for turntables. What pre-amp do you use or would recommend?
 

levimax

Major Contributor
Joined
Dec 28, 2018
Messages
1,444
Likes
2,072
Location
San Diego
O OK, think I get it. I was looking for pre-amps, but could only find phono pre-amps, for turntables. What pre-amp do you use or would recommend?
Maybe something like this? https://www.audiosciencereview.com/...s/schiit-freya-s-preamplifier-review-2.11543/ . Search the reviews on this site for more . I built a DIY pre-amp that has tone controls (which I really like) https://sound-au.com/project97.htm. If you don't need the extra volume you don't need to do anything... in many cases the "lost headroom" from EQ is worth it for more balanced sound but if you really like to listen loud there is a "cost" for EQ.
 

Jimbob54

Master Contributor
Forum Donor
Joined
Oct 25, 2019
Messages
8,818
Likes
11,073
Maybe something like this? https://www.audiosciencereview.com/...s/schiit-freya-s-preamplifier-review-2.11543/ . Search the reviews on this site for more . I built a DIY pre-amp that has tone controls (which I really like) https://sound-au.com/project97.htm. If you don't need the extra volume you don't need to do anything... in many cases the "lost headroom" from EQ is worth it for more balanced sound but if you really like to listen loud there is a "cost" for EQ.
The Topping Pre 90 gets good reviews too but is a bit clunky (and expensive) once you get the second box with the multiple inputs. A very cheap option (for boosting a single RCA input) would be the Topping L30 headamp- OP could find a similarly well performing xlr headamp with pre outs if needs XLR
 

mdsimon2

Major Contributor
Forum Donor
Joined
Oct 20, 2020
Messages
1,495
Likes
1,892
Location
Detroit, MI
A lot of this depends on source level and where you do volume control.

As @gvl rightly pointed out all that matters is that after all processing the signal that reaches your DAC is below 0 dBFS. If you do volume control in the same place you do DSP then digital clipping really should not be an issue and there is no reason to apply an overall gain reduction to offset your boost. You do need to recognize it is possible to experience digital clipping when your volume control position exceeds your boost level, i.e. if you have 5 dB of net boost at a volume position of -5 dB or greater it is possible to clip digitally. In practice this is rarely an issue as you will naturally attenuate higher level recordings and you can safely use higher volume control positions with lower level recordings as they are nowhere close to 0 dBFS in the first place.

I will agree that if you are using a volume control downstream of your DSP (say in a DAC) then you can have issues with level. As you note the standard approach is to offset your boost with a correspond gain reduction to avoid digital clipping. You should still be able to drive your amplifier in to clipping as your DAC output voltage exceeds your amplifier input sensitivity. If you feel you do not have enough volume and add additional gain from a preamp you have now shifted the issue from potential digital clipping to potential amplifier clipping.

Michael
 
Top Bottom