AD1865 - single 5v supply.

lordearl

Member
2007-06-14 1:42 pm
I recently noticed on the AD1865 datasheet that it can be run from a single 5v supply – quite interesting as it opens up the possibility of using the onboard resistors to make a neat portable AD1865 based dac.

Does anyone recall seeing a schematic for the AD1865 that runs on a single rail?
 
Earl,

If you are refering to the below paragraph of the AD1865 datasheet, they mean that the +5V digital supply pin (+VL), and the +5V analog supply pin (+VS) can be powered from the same +5V supply rail. Ideally, to minimize supply induced noise coupling, those two pins would each be powered from it's own isolated or independent +5V supply. They do not mean that the AD1865 does not also require a -5V analog supply rail (-VS), if that is what you were thinking. Please do let me know, however, if you believe I'm missing something here.

"Though separate positive power supply pins are provided for the analog and digital portions of the AD1865, it is also possible to use the AD1865 in systems featuring a single +5 V power supply. In this case, both the +VS and +VL input pins should be connected to the single +5 V power supply. This feature allows reduction of the cost and complexity of the system power supply."
 
Last edited:

ThuyTN

Disabled Account
2009-12-29 12:07 am
Are you sure it's gonna work? I have been looking at that board for a while... I have vzs' board that also uses the AD1865 but with PCM input. It's meant to be used with Ian's PCM-I2S board. Seems to be a better solution to me. Still waiting for the finalized version though.
 
I haven't made my board public since it was just a quick-n-dirty solution to try Ian's I2S to PCM board - even though it's working well ever since: link . As you can see it is a bare board with few caps, that's it, no regulator, no I/V, no format converter.

I'm working on a similarly bare board that will house 2x AD1865 DACs configurable either for balanced or parallel mode + u-fl connectors + buffered inputs. Don't ask when will be ready... priority is low.
Opposed to Pavouk I have regulators and I2S to PCM external to the DAC board - a more modular approach - matter of taste.

Pavouk's schematics is very simplistic but will work... his board is poorly designed for highish speed digital however it's commendable he made a clean layout on one side.
Ask him (or do it yourself) to add a ground plane to the top and you'll be fine.
 
Last edited:

skouliki

Member
2010-08-11 9:59 pm
Athens
I've built pavouk's I out board and replaced the 78l05 regulators with low noise MIC5207 soldered on adaptors. Im really happy with the sound (best digital source i had so far) but it is also the first time i listen to a multibit dac so i dont have previous point of reference. Right now im trying to make a ground plane version of pavouk's design but i dont how this will turn out given the fact that i am new to this hobby and dont have any education on electronics
 

lordearl

Member
2007-06-14 1:42 pm
I finished the build of Pavouk's design last night - no changes at all, exactly built as per his site. I have two TDA1543 dacs, a CEC DX71 dac, and two other AD1865 dacs - this one beats them all in terms of bass clarity and non-fatigue. Nice compact pcb, too.

Skouliki - how are you going with the modified ground plane version? Also, where did you get adaptors for the MIC5207. I have one pcb left, so will try a passive i/v stage and a few other modifications (eg. using some different caps around the DAC chip).
 
Hi.On pavouk's board i used those soic8 to dip adapters sold on ebay becase i had those in hand
5pcs So MSOP TSSOP SOIC SOP8 to DIP8 SOIC8 to DIP8 Adapter PCB Convertor 2 54mm | eBay

I did the 24bit current out board with a ground plane doing passive I/V feeding a opa627 and buf634 gain stage.I am happy with its sound but i got the curiosity to try ad844 as I/V after reading the thread by georgehifi. Still havent etched the 192khz board yet but its going to be current out and not voltage out. Let me know if you want the board and toner transfer files
 

lordearl

Member
2007-06-14 1:42 pm
Thanks - not sure about the digital ground plane, I'm going to start with just the pavouk pcb and take the i-out directly to the rca jacks and put the i-v resistors from hot to ground there, it should still work fine. Main thing is to tidy up the PSU as much as possible.

OPA627/BUF634 should be great. You could try an AD825 in place of the OPA627, I think it is a bit more natural sounding.....
 
Possibly using a separate PCB of copper sheet, the problem is that with normal on board ground plane you have numerous connections down to the plane with vias, whereas having a secondary plane would only be joined in a few places.
It would probably improve things, there is an article by Henry Ott where he describes a similar thing done for EMC purposes mainly. I will try and find the article as it will provide more info. I also believe it is mentioned in his his book Electromagnetic Compatibility Engineering.