Just a follow up…
I got that FiiO D03K DAC yesterday. I must confess I’m a bit disappointed… But I guess I set my expectations too high for a 30 euros device.
It’s definitely an improvement over the TV’s poor internal DAC, but still miles away from the Presonus BT internal DAC.
Some of those cheaper DACs are quite sensitive to load impedance.
What have you got it feeding into ?
Some simple things you can try:
Put a shunt resistor (to common) on each output of the DAC (left and right).
Try values between 560 ohm to about 3K3.
Some DAC output stages need a DC load to common.
Most audio equipment has AC couple inputs.
Put a series resistor on each output, between the DAC and the next stage, audio amp I’m assuming.
If you find the DAC lacks a bit of high-end, you can make a simple passive pre-emphasis filter like such (only 1 channel shown):
Experiment with the values, you want the pre-emphasis to gently roll in from about 4Khz and up.
You will get some gain reduction, but you can make it up with the amplifier’s volume.
Resistor R2, may not be required.
If on the other hand the audio is too boomy/muddy, then you can experiment by using shunt capacitors to reduce
some of the low-end.
Of course, nothing stopping you from doing all of the above and changing the fixed resistors to variable ones,
to give you more control.
R1, C1 and VR1 control the high end.
C2, VR2, C3, VR3 and R1 control the low end.
Note that since it’s purely a passive circuit, there will be some interaction between all of them.
I will leave the formulae and working out the values, up to you. 
Where are you getting your parts from? The Radio Shack® that I used to walk to seems to be a Hair and Nail Saloon now.
Koz
The Radio Shack® that I used to walk to seems to be a Hair and Nail Saloon now.
Radio Shack/Tandy went belly up a while ago.
Maybe the hair saloon still have some old parts in the back, next to the hair curlers.
You can get pampered while they scratch around looking for them.
In the U.S. you can get from several places, here are three of them:
https://www.digikey.com/en/products
https://www2.mouser.com/Electronic-Components/
Their sites have a good inventory search option and they will ship anywhere in the U.S.
Some will even ship world-wide.
Another option, do you have a local TV repair shop?
They will probably have the parts laying about as the values of the resistors and capacitors are not that critical.
Thank you for the suggestions Paul.
I’m connecting the FiiO DAC between the TV’s optical out to the RCA input on a pair of Edifier R1280T speakers.
But for a true comparison of all the DACs available I also did some tests with the Presonus E3.5 BT.
So basically the 3 testing scenarios using the Presonus were:
Source was some youtube music videos (ranging different genres, from jazz to classical to folk, rock, indie, blues, etc)
Results for each test:
For the end purpose (connecting the TV to the Edifier speakers), I think the FiiO DAC does a decent job and I’m happy with it for now. I think it’s not worth investing any more time on it now, but I’ll save your interesting suggestions for the future.
Koz, not sure how they work in the US, but Farnell is usually also a good place for online shopping of electronic components… The prices may not the best, but they have a lot of stuff in stock and fast delivery.
Over here we have Farnell which deals mostly with trade accounts and bulk purchase, and CPC (Farnell) that deals with domestic purchases including small quantities.
Yes, noise entering after the signal input is inversely proportional to the input signal, because a low signal requires more amplification which also amplifies the noise floor. This is why gain structure is an absolute priority for all audio chains. The rule of thumb is to get the signal to unity gain (0 VU) as early as possible and keep it there throughout the entire analogue chain. Unity (gain 0 VU) input to ADC outputs at -18 dBfs (digital), these are targets to aim at, not peak limits. Generally you can peak at least +10 VU without clipping in analogue, but hard clipping in digital is 0 dBfs & must be avoided with prejudiced, because it’s oh so much worse.
So, metering gain structure is important to minimise S/N. Unit gain is a major priority in all quality mixing & production work.
0 VU = +4 dBu = 1.782 dBv = -18 dBfs = 1,228 V(RMS) = 3.472 V(p2p)
Ken
Hi guys,
Here I am revisiting this topic again… 
I can believe (more than) 1 year has passed already! Time really flies!
I hope you’re all doing well!
After one year using the Presonus Eris E3.5 BT, I must say I’m still quite happy with them! BUT… I’m still missing a recording device… so I’m on the hunt again…
After Paul2’s sample on the Scarlett 2i2 I was pretty much sold for one, but after some more research I’m now actually leaning more towards some other options:
Motu M2
UA Volt 2
Audient iD14 MKII
All prices are from Amazon, except the Volt 2 which is from Thomman.
The price on the refurbished M2 is quite tempting.
On the other hand, Audient’s allegedly superior mic preamps are tempting too, but the linux issues are a big turn down, which is really pushing me away from this one…
The reports on good Linux support for the Volt 2 are quite appealing.
Apart from those differences, all 3 units seem to be quite similar otherwise and all seem to have a bit of an edge over Scarlett 2i2 (which BTW sells for 148 € on Amazon, occasionally dropping to 128 € for very brief moments… which I just missed one recently…).
I’ve watched Julian Krause’s reviews on youtube of all 3, but I still haven’t made up my mind…
Anyone in here have tried any of those interfaces and would like to share any thoughts?
Some of the most important aspects to me are:
Hi there bgravato, nice to hear from you again.
I’ve heard good things about the Scarlett 2i2, and driver problems on Linux seem to be a thing of the past (positive review from 2017: https://sanderson.band/2017/09/04/focusrite-scarlet-2i2-in-a-linux-home-studio/)
I’ve also heard good things about the Behringer UMC202HD, which as you might expect from Behringer, is about half the price of the Scarlett 2i2.
I’ve not used either, but there’s a comparison of the two here: https://thehomerecordings.com/umc202hd-vs-scarlett-2i2/
Hi bgravato, time does fly, can’t believe that a year has flown passed already.
As to the recording device, you didn’t mention the max sample rate you are after.
Do you need up to 192K or is 96K/48K OK?
You will find that the more expensive ones, will record up to 192K at 24 bit.
As for Linux compatibility, I can confirm that the Onyx (by Mackie), the Presonus 96 (max sample rate 96K)
and the Scarlett 2i2 all work on Debian 10, 64 bit.
Just be careful which generation of 2i2 you get, as I believe the older ones may not work or only partially work
and not all can do very high sample rates if that is important to you.
As to pre-amp and USB noise, the above are pretty good and often use them for broadcast work.
I find in general, that the Behringer products are not at the same level but, they are cheaper.
Have heard good things about the Motu and the Audient, but have not tried either so cannot confirm.
Hi Steve and Paul,
Thank your for your replies.
I don’t think I have ever used more than 16bits/44.1kHz, so not exactly sure what to expect of higher specs… I guess the more options the better?
As usual, probably Behringer has the better bang for buck ratio… It costs half the price of the competitors…
Although, as Paul mentions, there seems to be a bit of a difference… Whether it’s worth paying twice the money for maybe 10% or 20% increase in quality is subjective, but considering my disappointing experience with the AudioBox 96 from my friend last year, I’m willing to pay the extra for a bit better…
From a technical point of view I’ve been basing my opinions in great part on Julian Krause’s reviews and tests, which I think is regarded as unbiased and accurate tester by many people: https://www.youtube.com/c/JulianKrause
I’ve also watched quite a few other videos and read some blog and forum posts which tend to confirm those results in general.
This other guy also has some interesting reviews about running multiple audio interfaces on Linux: https://linuxgamecast.com/linux-compatible-audio-interfaces/
One thing I know is that I don’t want an AudioBox96… (which unsurprisingly was one of the worst in terms of input noise on Krause’s tests)
Last year I was pretty convinced Scarlett 2i2 (3rd gen) was the best option for me, but from what I’ve been reading now, devices such as Motu M2 or UA Volt 2 seem to have a bit of an edge over the Scarlett… (they also cost a bit more, unless I get a refurbished one, which I might).
There seems to be a general consensus also that the “new kid on the block” that seems to be superseding these (at least in the quality of the mic preamps) is the Audient iD14 MKII. I could wait a few more months to see if the linux issues it has are solved, but probably by then another new and better interface is out and it’s an endless loop… 
SSL 2 and SSL 2+ also get good reviews, but I really don’t like the form factor… I think it would be too big for my desk…
Bottom line, I guess I’ll probably be happy with either Motu M2, UA Volt 2 or even the Scarlett 2i2 3rd gen… so I’ll probably go with one of those. Which one I guess will depend on availability and price… or maybe due to some particular feature (volume meter on M2 looks pretty neat!) or just the best looking one
Edit: forgot to say, if it wasn’t for the reported linux issues, I’d possibly go with the iD14, for the better preamps, but I really don’t want to risk not being able to use it properly on linux, so…
I have had OK results with the AudioBox 96, but it’s nowhere as good as say a Scarlett.
Another feature you may want to consider before making a final decision, check that the interface has direct monitoring output’s.
Can be very handy in some situations.
Thanks. I’ve checked and I believe all the ones I’m considering do have direct monitoring outputs.
One thing that stands out in Motu M2, that the other seem to lack, is the ability enable/disable 48V phantom power separately for each input, while Volt 2 or Scarlett seem to be either both or none. This might be valuable if I want to use two very different mics and only one needs phantom power.
So overall I think I’m leaning more towards the Motu M2…
Well… Yesterday another refurbished unit popped up in Amazon Warehouse in (allegedly) very good condition, for a fairly decent price, so I decided to not wait any longer and order it before someone else did
I should get it next week and I’ll post my first impression on it by then.
Got the Motu M2 today.
I haven’t tested the mic input yet, but I’m very happy with the output so far! Both line out and headphones out seem to be virtually noise free (at least with my gear - monitors and a couple of different headphones - I couldn’t hear any added noise coming from the Motu M2).
This was with inputs monitoring off. If I turn on monitoring for inputs (unplugged) and crank the gain all the way up there’s some white noise of course, but doesn’t seem to be very loud. I’ll report back once I get the opportunity to try it with a mic.
Edit: forgot to say… for playback it worked out of the box (plug and play style) on Linux (Debian 11 running kernel 5.16 from backports).
Thanks for reporting back that the Motu M2 works on Linux (Debian), another option available, along with the other two I mentioned previously.
Obsessive reporting in.
Checking mic amp noise with nothing connected doesn’t tell you anything useful. The amp turns into a little radio receiver responding to any trash that happens to be flying around. Extra points if you live near a radio station or an airport. You should do that test with an “artificial microphone” such as a metal film 150 ohm resistor inside a metal XLR connector. Yes, I do have one here and I’ll post a pix shortly (after breakfast).
It’s also good to know the amp gain. It’s not unusual for a home style amp to only supply 40dB out of the super handy 50dB or 60dB you probably need.
That’s Marketing. Too Loud and Overloading equipment gets sent back. Too Quiet equipment doesn’t.
Koz
You’re right!
I got a meeting canceled, so got some unexpected free time and I was able to connect the mic. I’m happy with preliminary testing! I’ll try to post a sample later.
It also worked pretty much out of the box on Audacity for recording.
Hi Bruno,
good to see you back again - hope all is well with you.
Peter
If you look up the M2, do it from the Sweetwater site…
https://www.sweetwater.com/store/detail/M2--motu-m2-2x2-usb-c-audio-interface
… not Amazon. The Amazon listing is broken. The front picture of the interface is too wide and the specifications tell us it’s a 16 channel interface. I get the impression they got the ad from floor sweepings.
Since you’re about to try out a stereo interface with, we assume, one microphone, you need to decide how you’re going to manage that. You can capture mono, but most techniques reduce the volume by half to “make room” for the missing channel. This doubles the noise. You can totally capture stereo with one really good microphone channel and a silent one. Then you split the track into two monos (menu on the left of the track) and delete the silent one. Perfectly valid. It’s just more work.
Sometimes the driver software will allow you to capture mono without the dip in volume.
Koz