Variable vs Fixed DAC?

Is it true that DACS with fixed output do not have a preamp stage ? and that DACs with variable output have a preamp stage which causes added noise/distortion ?

Would you say that Schiit Modi with a fixed output is superior to Creative X7 with variable output ?

Before I answer, a little disclaimer, I never used Modi or Creative X7 before.

Yes it is true. As the name suggest, the fixed output will output the signal at line level at all times.

Yes it is true, but for this price range, I wouldn’t worry about it for too much because there are other factors that are more important and more affecting than the variable volume control.

So, if I want to be pedantic about it, every additional stage or process to the signal will affect the signal in one way or the other. In DAC at this price range, most likely the resistors or the system that they use for the preamp stage is not that good. From my own experience, the low quality resistors that they use in this price range does impact the sound in a negative way, but again, I would only notice this when I’m having a critical listening session. If you want an absolute performance, then you can consider having a preamplifier in your system, but IMO it’s better to put your preamp money to a better DAC.

But when you connect any DAC through USB to a PC, there is a digital volume control in windows that can be increased or decreased…Creative X7’s volume knob is digital. Turning the knob would increase/decrease the digital volume in Windows. Does this mean that X7’s DAC does not have a preamp ?

Some DACs come with a potentiometer on them, and do not control the volume digitally. The volume control is analog… these are the DACs that have a preamp, right ?

Hmmm, I think yea it doesn’t. I think the X7 only communicate with Windows to control the volume.

Yes that’s true.

You are better off adjusting volume in the analog realm vs the digital realm. Set windows to 90+ and adjust volume via dac/amp.

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Most DACs (there are exceptions) have some kind of output stage (Buffer, Op-Amp, Discrete Circuit, etc.). Does not matter if there is a pre-amp section built in or not.

Depends. There are good and bad designs and good and bad components.
In theory, one could make an output stage with a lower noise floor than the DAC before it.

I am not familiar with the APIs and Soundstack in Windows (or the X7) to give a qualified answer.
It might be possible to get the full bit-depth from Windows and then attenuate/boot volume after the Digital to Analog conversion.

It is possible to have digitally controlled “analog” volume control (Digi-Pot, voltage controlled amplifier, etc.)
But in general, a volume pot is a good indication of a pre-amp section being present in the DAC.

By output stage, you mean the analog stage right ?

There are two types of DACs:

(1) DACs without preamp: DAC chip >>> analog stage >>> RCA outs
(2) DACs with preamp: DAC chip >>> analog stage >>> preamp stage >>> RCA outs

How to figure out my X7 is type 1 or 2 ? Since it has a digital volume knob, I guess it is type 1…

if it has a volume knob, by definition it’s a pre amp.

The output stage is the last component or component group before the signal leaves the device. All of the types of output stages, by nature of the signal they handle, are analogue.

There are way more. And with the variety of ways to lay them out, putting them into classes like that is impossible.

The Creative X7 acts as a Pre-Amp, how that is executed layout wise, no idea. Would have to see detailed pictures of the internals.

would you say that a DAC with a preamp is inferior to a DAC with no preamp sound quality wise ?

If a DAC has a preamp, wouldn’t it add noise/distortion to the signal ?

Absolutely. DACs have come a long way since the X7 was released and the hardware was more about the unique combination of features than any outstanding qualities.

IMO, the X7 is a pyramid of steaming shit because Creative couldn’t/wouldn’t fix the firmware/software. Common story with Creative products and a big part of why I’m still annoyed I bought an X7 after knowing better from previous experiences.

It depends on the implementation, can’t make a generalized statement on it.

Here are the pictures of the internals:

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