T51/s:flo2 Volume Control?

I believe you might have mistaken the line-out (green) with the headphone-out (black). The volume pot only affects the headphone-out.

lolz

noticed on mine that i only need my amp volume very low from the line out ,on the cowon hp out its at between quarter to the hour to ten to the hour(if you get my drift) but less on the sflo.(using caffine ultra)
btw isnt a true line out unaffected by eq ? not that im complaining it sounds amazing

Yes, and that is because S:Flo has some of the strongest output I ever heard.

The modern generation of DAP processor has all kind of functions integrated into it, EQ is just one of them. Since EQ is done on the processor level before the signal is decoded by the DAC, there is no way to avoid it. Actually many DAP out there just use their firmware to set a flat EQ on their line-out, which make them 'sound' like having no EQ at all. In fact, many DAP's line-out are variable too. The control are just disabled on the firmware so they would appear as 'proper' line-out.

TBH i always thought a line out was a very low amplified analogue signal or not amplified at all i.e an amp bypass. i know the sflo has a dedicated opamp for the line out , im just a bit confused by all this ,i.e isnt my signal still being double amped by my caffine ?same as my cowon was?

To be qualify as a line-out, the signal needs to be on line level. What that means, at least on my understanding, is that the dynamic range of the signal must be at its best (and over a certain voltage). Best dynamic range is just a way of saying the output signal is at its maximum before distortion starts to increase due to over-stressing the circuit. In short, you get the cleanest, best possible SNR on the line-out, which makes it the best option for amplification. Due to the fact that headphone-out can be variable (which means its dynamic range / SNR isn't always at its best), amping is less ideal - thus why if you want to amp the headphone-out (HO), you should keep the volume high but make sure you don't hear any distortion. That way you get the best possible dynamic range from the HO, though it is most likely not going to be as good as a real dedicated line-out. BTW, some people like to call it a 'virtual line-out', but hmm...

IIRC, on the case of S:Flo2 (dual WM8740, and actually on some DAC chips), the DAC chips themselves do not output your regular analog signal directly, thus you will need an opamp to 'convert' the signal, and that is why the opamp is there for. Some time the amp is there to amp the signal to line level as well. In some case, especially on SoC (System-on-Chip), the DAC output line-level signal and you don't need an extra opamp. Technically you can say it is double amping - but it is double amping on line-level signal, which usually doesn't deteriorate the SNR like amping HO.

Also, it is usually better not to pair two of the same opamp if you know which opamp is on the line-out. Though you are amping a line level signal, there is no way to avoid the sound signature of each opamp in the signal path. If there is two in a chain, the sound signature will likely to be exaggerated. For example, if there is an AD8620 on the line-out, you will be better off not using Corda MOVE (which is dual AD8610, the mono version of AD8620). In theory anyway.

That's very interesting ClieOS, makes sense. I saw that you replied a few times in a couple of Fuze threads (sorry for the slight hijack) and was wondering whether the signal from the Fuze is true line out? Seems there is a lot of confusement about whether or not it is. Also I read that the hp out is of better quality than the line out, even when amped? Could you enlighten me?

By spec, Fuze does have a true line-out. It is a little bit complicated since Fuze doesn't actually has an independent DAC or amp section as everything is integrated into one SoC, but it is a line-out nonetheless. As for whether it is better on the LO, my answer is yes. But whether you will find the improvement enough for you to carry an extra amp around, I don't know. I can only tell you I do use my Fuze + LOD + T4 more than just the Fuze alone. At least for me, (Fuze + LOD + amp) > (Nano4 + LOD + amp) > Fuze >> Nano4.

Going back to the topic, I do find S:Flo2 headphone-out is just about as good as my Fuze + LOD + T4, but not quite as good as Fuze + LOD + 3MOVE.

That is mighty interesting I'm considering both daps, probably going to get both! How would the line-out from s:flo2 compare to the other setups (in stead of headphone-out)?
Also I do like amps and there's an Ibasso p3+ coming my way as we speak, to that's gravy. Where can I get the LODs for the Fuze, any idea? When I buy the Fuze (quite soon) I want to get a LOD immediately with it.

The headphone-out on S:flo2 is so powerful that I just don't need to use an amp with the line-out, especially for my IEM. I do find the line-out to be a tab better than Fuze, and insanely high output (more than twice louder than Fuze or Nano's line-out).

If you don't know how to build the LOD yourself, try eBay or ask a DIY'er to build one for you.

cheers i sort of get it now ,im also now itching to try a differant amp with my sflo or maybe an amp that allows amp rolling (not that im unhappy with the caffine)