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tbsn
0
Oct 29, 2015
This looks like it might be against the o2/ODACs 'no derivatives' license considering there's some kind of switching in the back to have the RCA serve as both input and output. I'm curious how that is implemented.
tbsnI posted pictures of the daughter board a few pages back. The RCA input/output doesn't require any switching, it works based on how the RCA jacks are wired to the board.
hertzberg
2
Oct 29, 2015
WillHi Will - Are you saying the combined RCA in/output is done without altering anything on the o2 amp and o-dac? I have now search through the all posts, and cannot find the pictures of the daughter board - could you guide me? Thanks
Tigole
464
Oct 29, 2015
hertzbergLogically, this would seem like the standard O2+ODAC from JDS with the 3.5mm input at the front right. On this version, that jack is replaced with RCAs on the back. JDS doesn't warn against using that as an input for the O2, but recommends against using it as an output for the ODAC.
mateopase
16
Oct 29, 2015
hertzbergThe O2 board and the ODAC board are completely unaltered. I built one of these a year ago, and what essentially happens is that the ODAC's outputs are connected to both the RCA jacks and the O2. So, if you leave the O2 off but have the ODAC powered, the audio will go out through the RCA jacks. If you leave the ODAC unplugged but turn the O2 on, the RCA jacks go to the ODAC, but then keep going to the O2's input.
hertzberg
2
Oct 29, 2015
TigoleWhy do JDS recommend against using it as an output for the ODAC?
I found something about it here - https://www.jdslabs.com/pdf/Instructions_O2-ODAC.pdf - but do not quite get it - will the sound be degraded if using the inbuilt ODAC as a source for other amplifiers? In other words - would it be better to use a seperate ODAC for other amps?
Tigole
464
Oct 30, 2015
hertzbergThe O2's input, ODAC's output, and those RCA jacks are connected together essentially in a 3-way. Any time something is connected to those RCA jacks, the O2 essentially has 2 inputs and the ODAC has 2 outputs. That changes the impedance they see, even when the other half of the device isn't powered. The performance specifications for each were tested with one input/output with impedance that's typical for what they're designed for. At least for the ODAC, JDS warns against it because the performance of the ODAC is likely not within its specifications when it's connected to an external amp and the O2 simultaneously.
hertzberg
2
Oct 30, 2015
TigoleSo it'll be the same as using a splitter cable - essentially? One dac/source to two amps?
Tigole
464
Oct 30, 2015
davidly
7
Oct 31, 2015
TigoleTigole,
I'm not sure I fully understand the 3-way implementation. Would this DAC/Amp be invalid for RCA output to powered speakers? For example, if I have powered speakers hooked up to the RCA output, what happens when I plug in the headphones into the headphone jack? Would the audio signal switch to just headphones? I didn't see a switch of sorts at the front panel.. I had this issue with Aune T1 Mk II, the signal split to the amp and the RCA out but didn't switch. So when I plugged my headphones in, my powered speakers would still be playing.
Tigole
464
Nov 1, 2015
davidlyI doubt it'll switch to the headphones. It'll likely behave the same way as the Aune with audio going to both the powered speakers and the headphones, probably with a bit more distortion to both as well. I'm no expert though, but I did stay at a Holiday Inn Express last night. Just kidding. All I know is that JDS warns that the ODAC's performance with an external amp might not be within specs when the O2, ODAC, and input/output jack are connected together that way.
It sure would be nice if @Will could jump in and clarify all of this for us by answering my questions on page 6 of this discussion.
davidly
7
Nov 1, 2015
TigolePerhaps my desire to use both headphones and powered speakers with a switchable DAC/amp isn't a widespread one. I've had a difficult time finding a DAC/amp that does this at a reasonable price. I had a Audioengine D1 which auto output-switched between headphone amp and RCA out, but didn't drive high impedance cans very well.
I moved up to the Audio-gd NFB-15 since then, but is there another method that people use to switch headphones <-> powered speakers? Maybe majority of the people only use headphones for their DAC/amps...
SadCack
14
Nov 1, 2015
davidlyI'm looking for the same thing. The main reason that I joined the drop is because of the USB in and RCA in-and-out. I want to be able to use it with my JBL 305s as well as my headphones. Is what I'm hearing that it won't be feasible?
Tigole
464
Nov 1, 2015
SadCack@davidly@SadCack
In terms of the added distortion to both audio paths, you likely won't notice a difference via the speakers. The speakers' onboard amp will add more distortion, and it's a lot harder to get speakers to reproduce sound as transparently as headphones. You can reduce distortion to the headphones by unplugging the RCAs. If you want to avoid that, you could get the standalone ODAC and O2, and get an RCA switcher to switch the ODAC's output between the O2 and the speakers. Otherwise, you could use a separate DAC for the speakers and switch the output between the two DACs in the OS. Personally, I use the onboard sound to output to my speakers and a separate DAC/amp for my headphones. For Windows, I use a little piece of software called SoundSwitch that places an icon in the system tray to easily switch output devices.
SadCack
14
Nov 1, 2015
TigoleThanks for the response. I have no problem just removing the rca cables when I want to use my headphones. If that's the worst part of the procedure, I can handle it. The reason I want some sort of interface is because the 305s, when plugged directly into my motherboard, had too much interference and don't get loud enough. Hopefully using the Odac will help.
Tigole
464
Nov 1, 2015
SadCackFrom my personal experience, I can hear a high pitch whine on my headphones when I use either the motherboard's onboard sound or any sound card plugged into the motherboard--likely due to RF interference from a lack of shielding inside the case. I don't really notice it when I use the onboard sound with my speakers though, so that works for me. I suspect any external DAC would be immune from that interference problem.
I don't know about that "loud enough" problem with your JBLs. I would think that if you're getting a proper line level signal, not being loud enough would be a problem with the JBL's internal amp. If you want to avoid having to unplug the RCA jacks, a Behringer UCA202 would be a pretty good and cheap external DAC with line outputs for your speakers. It's under $30; NwAvGuy reviewed it, and he even has a mod for it to perform better:
http://www.amazon.com/dp/B000KW2YEI/ http://nwavguy.blogspot.com/2011/02/behringer-uca202-review.html http://nwavguy.blogspot.com/2011/03/behringer-uca202-frankendac.html
SadCack
14
Nov 2, 2015
TigoleThe problem is that I need a preamp/dac with a volume control. I had a Scarlett 2i2 for a while, and that volume knob allowed me to get more than enough sound from the speakers. I returned it when I found out the headphone amp was garbage, but I would like something like that.
davidly
7
Nov 2, 2015
SadCack@SadCack,
Check out the Audio-gd NFB-15. Has everything that you're looking for. It has dual wolfson WM8741 chips, amp that will put out 1.8W at 50ohm, and amp with usb, coaxial, and optical inputs. It's pretty big dimension-wise, but I don't think you can get anything with that much features for under $300... Only thing is the Audio-gd team is based out of China and their communication isn't their strong point. They are responsive, but English isn't their strong point.
davidly
7
Nov 2, 2015
Tigole@Tigole
Thanks for the SoundSwitch suggestion! I should really try that out. I have another computer setup that has Audioengine A2+, which has a built-in DAC for its powered speakers, so I might just get this for as a dedicated headphone DAC/amp.. and not care too much about the switching function between headphones <-> speakers.
As a matter of fact, now that I think about it, I think i'm talking myself out of the need for the autoswitching feature that i've been so OCD about. The speaker setup is so much more dependent on external variables like room size, speaker placement, sound reflections, etc, that perhaps it won't benefit as much from a good DAC as headphones will. As long as the speakers have a good amp to drive the sound up, maybe that's all I'll need.
Tigole
464
Nov 6, 2015
davidlyFYI, I was just looking at the JDS Element and it appears to have what you want in terms of switching between speakers and headphones. You'll need the "Automatic DAC Line-Output" option. With that option, when the Element is off, the DAC's output is connected to the RCA jacks for your speakers. When it's on, the DAC is disconnected from the RCA jacks and output goes through the internal amp to the headphones.
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