• 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). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Cost of XLR outputs in DACs

DuxServit

Senior Member
Forum Donor
Joined
Apr 21, 2018
Messages
385
Likes
368
#1
Just wondering about why some DACs don’t have XLR outputs:

(a) Does XLR outputs increase the complexity of the DAC design?

(b) Does it increase the BOM costs? If so, by what percentage?
 

NTomokawa

Addicted to Fun and Learning
Forum Donor
Joined
Jan 14, 2019
Messages
655
Likes
1,056
Location
Canada
#2
Correct me if I'm wrong: XLR output level standard is 4 volts while RCA is 2 volts.

A simple inductor-based boost circuit will measurably degrade the output performance. That is without taking into account the fact that XLR is supposed to be balanced (3-pin vs. 2-pin) so you have a more complex signal path implementation.

Also bigger connectors = bigger board = bigger casing = higher cost.
 
OP
DuxServit

DuxServit

Senior Member
Forum Donor
Joined
Apr 21, 2018
Messages
385
Likes
368
Thread Starter #3
Also bigger connectors = bigger board = bigger casing = higher cost.
Right. But by how much?

Or is it simply a marketing strategy (call the XLR version a "new product", the big brother of the RCA-only, then charge extra 50% to 70% more).
 

KSTR

Addicted to Fun and Learning
Joined
Sep 6, 2018
Messages
529
Likes
1,226
Location
Berlin, Germany
#4
BOM cost of a basic XLR output derived from an output buffer is, well, the XLR socket and two (2) equal break-out resistors, 100Ohms typically. One goes to the buffer, the other to ground. This fulfills the balanced connection requirement of that there shall be impedance symmetry. Signal symmetry (wrt ground) is NOT required to exploit the virtues of a balanced connection, but impedance symmetry is.
This kind of XLR output of course has the same signal level of the corresponding unbalanced output (derived from the buffer output with a single break-out resistor, again 100Ohms typically).

In most consumer gear, the balanced out is often made with a unity-gain inverter tapped off from the unbalanced output (the actual buffer output, that is) and hence offers signal symmetry and twice the total signal level. Sometimes, the level of the XLR out is made the same as the RCA output, at increased complexity.
In yet other cases, when the signal path of the device is fully balanced internally, we already have the signal-symmetric balanced output and then the unbalanced output is made from a simple differential amplifier of unity-gain (hence same signal level) or gain on 0.5x (half the level, to avoid headroom issues -- clipping) of that gain stage. Again, the break-out resistors are used, they provide isolation of capacitive loads (long cables) so that the op-amps used won't oscillate.
 
OP
DuxServit

DuxServit

Senior Member
Forum Donor
Joined
Apr 21, 2018
Messages
385
Likes
368
Thread Starter #6
Looking at the DACs that Amir has measured, there is a price threshold of say $200, above which XLR output is required.
 

LTig

Major Contributor
Forum Donor
Joined
Feb 27, 2019
Messages
2,138
Likes
3,138
Location
Europe
#8
My Tascam outputs about 12 Vrms differential at full volume.
Tascam is not consumer gear. My RME DAC outputs +19dBu (6.9 Vrms) unbalanced and +24 dBu (12.3Vrms) balanced maximumat 0dBFS, can be reduced to +13 dBu (3.5 Vrms) and +4 dBu (1.2 Vrms).
 
Joined
Feb 3, 2020
Messages
32
Likes
2
#10
Does reducing the volume by 2 dB reduce the voltage from +16 dBu to +14 dBu?
 

sergeauckland

Major Contributor
Forum Donor
Joined
Mar 16, 2016
Messages
1,631
Likes
3,477
Location
Suffolk UK
#11
Does reducing the volume by 2 dB reduce the voltage from +16 dBu to +14 dBu?
Yes.

By the way, the EBU defines 0dBFS = +18dBu, as that provides 12dB headroom above the normal European peak operating level of +6dBu. The UK normally operates at +8dBu, so we have only 10dB headroom. Most US practice is, I understand, 0dBFS =+24dBu as that provides 20dB headroom on 0VU (+4dBu) necessary when using VU meters rather than PPMs.

Aren't standards wonderful........

S
 
Joined
Feb 3, 2020
Messages
32
Likes
2
#12
My DAC (Steinberg UR44C) says it has a +16 dBu line-out. This clips my amp (Monolith THX Desktop) input - it has an "OVER" indicator on the LCD. I'm assuming reducing the DAC volume to -2 dB results in +14 dBu (< 4 V RMS) on line-out, which the amp can handle without clipping.
 

sergeauckland

Major Contributor
Forum Donor
Joined
Mar 16, 2016
Messages
1,631
Likes
3,477
Location
Suffolk UK
#13
My DAC (Steinberg UR44C) says it has a +16 dBu line-out. This clips my amp (Monolith THX Desktop) input - it has an "OVER" indicator on the LCD. I'm assuming reducing the DAC volume to -2 dB results in +14 dBu (< 4 V RMS) on line-out, which the amp can handle without clipping.
Yes, that's right. +16dBu is just on the threshold of what the Monolith can handle on its XLR inputs, so +14dBu would be better.

S.
 
Top Bottom