[Sam21]

Standalone DACs with no volume knobs usually have a fixed output when you set their volumes to max in Windows. Which is usually around 2Vrms ? For example, To use Atom DAC+ and SMSL SU-1 DACs you have to set their volumes to max in Windows and then they both output around ~2Vrms ?

(By DAC/AMPs I mean combo units like: (Topping DX5 , Creative G6/X7 , FX-Audio DAC-X6 MKII)

With Some DAC/AMPs, The volume knob affects the RCA-outs and with some, it doesn’t. some even have a switch to change between fixed and variable output.
Is my understanding correct ? please confirm.

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I have some questions:

Why do some DAC/AMPs have variable output through their RCA-outs that is controlled by the volume knob ? When using them as DACs only, why don’t they just output a fixed signal (~ 2Vrms) like a standalone DAC ? Does turning the volume all the way to zero makes the DAC/AMP to output a fixed signal ?

Doesn’t the signal get degraded when the output is variable ?

When used as DACs only(USB-Optical to RCA-outs), Do the following units output a fixed or variable signal:?

Creative X7
Creative G6
FX-Audio DAC-X6 MKII
Zorloo ZuperDAC

 

[tomb]

Don't use a DAC-amp and it solves your questions. Once a design goes down that cost-cutting path of sharing casework, power supplies, etc., there's no telling what the mfr will decide to compromise.

 

[GREQ]

Why do some DAC/AMPs have variable output through their RCA-outs that is controlled by the volume knob ?

If it's cheaper to implement and can be bypassed with a switch - it becomes a 'feature' which can be marketed as a convenience.
The Chinese market for example, is laser-focused on 'convenience'.

 

[buke9]

The variable output is usually used for powered monitors/speakers .

 

[ProtegeManiac]

I have some questions:

Why do some DAC/AMPs have variable output through their RCA-outs that is controlled by the volume knob ?

So you can use them with speakers.

If you use them with passive speakers you can use a power amp. As in it's not an integrated amp...because it does not have a preamp.

If you use them with active studio monitors with one amp on each speaker unit you don't need to adjust two knobs on each speaker every time you adjust the output.

If you use them with non-pro active speakers you can still set the speakers far from you and far apart from each other without having to reach over to the the volume knob on the Master unit.

When using them as DACs only, why don’t they just output a fixed signal (~ 2Vrms) like a standalone DAC ?

Because

1. Some have a separate pair of output for that

2. If they don't have a separate output for that (or a toggle, in some cases) then it's because the manufacturer was hedging bets that people need to control speakers and would be more interested in a $99 DAC-HPamp-Preamp than if it was just a DAC-HPamp with a fixed 2V output (eg NuForce uDAC).

It's kind of like with other things. Let's say a camera. Maybe a camera manufacturer will bet that for this price point people buying it only use the LCD screen, so no viewfinder.

Does turning the volume all the way to zero makes the DAC/AMP to output a fixed signal ?

In most cases it will output no signal.

And technically the mere fact that there's a knob means it's not fixed - what you're going for there is where 2.0V is and no, turning it up to max ain't it unless it's a passive preamp.

Doesn’t the signal get degraded when the output is variable ?

Usually, yes. The preamp will add some amount of noise and distortion, and can overdrive the receiving amp for example.

But in the case of modern DAPs where they don't even have an electronic switch, not so much, since it's not feeding into exactly the same sort of hardware. You're just capping it, and what hardware it does have just can't go any farther.

In the case of DAC-HPamps with the hardware though...you're supposed to use that kind of DAC with a power amp driving speakers, or at worst, a powered speaker for convenience, not a transparent headphone amp driving drivers inches from your eardrums that will make any noise more audible than with speakers measured at 1m but realistically if it was a living room and not a desktop system you're be closer to 2m.

When used as DACs only(USB-Optical to RCA-outs), Do the following units output a fixed or variable signal:?

Depends on the DAC's hardware design.