Experience with this DIY DAC ? - Page 112 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Line Level

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 26th August 2009, 01:10 PM   #1111
RIP
 
Join Date: Oct 2005
Location: Central Florida
Quote:
Originally Posted by johnm View Post
Hi Bill.

I'll try those suggestions and get back to you.

Incidently even though the 15v-0v-15V are disconnected as not being used, should I still have connected the CT of this winding to the circuit board?

- J
Nope. That would turn the ground plane of the board into a transmitter antenna for any RF trash in the trafo.
  Reply With Quote
Old 26th August 2009, 01:16 PM   #1112
johnm is offline johnm  United Kingdom
diyAudio Member
 
johnm's Avatar
 
Join Date: Sep 2003
Location: Hampshire
OK disconnected the power to the DAC and I only get hum when the volume control is 3/4 of the way around.

With power connected the hum is quite audible from around the 12 0' clock position. Using a piece of cardboard and moving the wires around and/or the A20s does not seem to affect the hum level.

- John
  Reply With Quote
Old 26th August 2009, 01:56 PM   #1113
RIP
 
Join Date: Oct 2005
Location: Central Florida
Quote:
Originally Posted by johnm View Post
OK disconnected the power to the DAC and I only get hum when the volume control is 3/4 of the way around.

With power connected the hum is quite audible from around the 12 0' clock position. Using a piece of cardboard and moving the wires around and/or the A20s does not seem to affect the hum level.

- John
I have to go soon, but I'm not clear on whether the power trafo is energized or not. Still, I think you should concentrate on getting the chassis buttoned up and earth grounded. I've had problems like this on the bench that mysteriously disappeared once the project was completed.
  Reply With Quote
Old 26th August 2009, 02:10 PM   #1114
johnm is offline johnm  United Kingdom
diyAudio Member
 
johnm's Avatar
 
Join Date: Sep 2003
Location: Hampshire
I tried with and without the DAC plugged in. But I'll also try disconnecting the transformer from the DAC board also.

Agreed about buttoning it all up and then trying again. Once the chassis is earthed properly and I have some proper high quality RCAs installed and the mains cable is neatly routed away etc I'll see where I stand then.

Thanks,

- John
  Reply With Quote
Old 26th August 2009, 02:14 PM   #1115
johnm is offline johnm  United Kingdom
diyAudio Member
 
johnm's Avatar
 
Join Date: Sep 2003
Location: Hampshire
Quote:
Originally Posted by legarem View Post
Many peoples shipped me their dacs because there is this hum

You have to use a wire from the ground plane of the dac board that goes to the outer ring of RCA output jacks that are now connected to the transformers. No more hum.
Thanks for this suggestion I'll try it later today

I assume the connections from RCA shield to each A20 stay connected, but in addition a wire is run from each RCA shield to the ground plane of the DAC board? I'll use the ground hole for the original RCA outputs which I removed.

Thanks,

- John
  Reply With Quote
Old 26th August 2009, 03:22 PM   #1116
diyAudio Member
 
Join Date: Jun 2009
Quote:
Originally Posted by johnm View Post
You'd have to change the switch I'm afraid.

However you could add some toggle switches to the front panel of your chassis, and run leads to where the original switches used to be on the DAC board. Would at least be easier to select sampling rate then.

I plan to do this too once I've got it all working properly and hum free.
Not to beat this to death, but I had a similar question. I'd like to try some high rez recordings from Reference Recordings. They are recorded at 24/176.4 and are typically replayed using a computer/DAC setup. (I have my DAC connected to a Mac Mini via USB.) Currently, I have the DAC's toggles set for 0 and 1 (up to 24-bit) and 1 and 0 (double speed 50 to 100 kHz). If I understand the previous post correctly, I would need to manually change to quad speed (100 to 200 kHz) whenever I want to listen to hiz rez.

I'm curious about this because I can play back a couple of sample tracks without any manual switching. Is the DAC automatically stepping down the music for playback?

Also, I'd be curious to see how the toggle switches should be added if/when someone gets around to it.

Finally, just for laughs, I'll mention that the DAC Reference Recordings recommends for replay lists for $5,000 (US).

Thanks in advance to everyone in this thread for humoring my noob questions.

Steve
  Reply With Quote
Old 26th August 2009, 03:43 PM   #1117
johnm is offline johnm  United Kingdom
diyAudio Member
 
johnm's Avatar
 
Join Date: Sep 2003
Location: Hampshire
I'd bet the DAC is downsampling the file you're playing. Simple to throw a couple of switches though and listen again using quad speed (the correct setting).

Regarding the toggle switches, you'd merely desolder the switches from the DAC board (VERY carefully so you don't damage the DAC with heat, and not to dislodge the tiny SMD resistors on the underside of the board), then run wires from the holes to toggle switches on the front panel. All you're doing is just adding some wire/distance between the switches and the DAC so not changing anything per se. Just make sure you get the switches the right way around so as not to muck up any sampling rate settings etc

EDIT: I seem to remember reading that with this DAC's USB input the max. sample rate was 48khz? Definately need some clarification on this. Generally I don't think you can get 192khz sample rate with bog standard USB (unless you pay for a big bucks converter)... For what it's worth I also bought a Mac mini recently, and am VERY happy using the optical output straight into the DAC. The Mac mini can output up to 24/96 using the optical connection (you have to select 24/96 from the Midi settings screen) and it sounds amazing through this DAC. I truly believe optical isn't as inferior as SPDIF as many would have us believe, at least from my listening tests and a decent optical cable from www.lifatec.com.

Last edited by johnm; 26th August 2009 at 03:52 PM.
  Reply With Quote
Old 26th August 2009, 04:37 PM   #1118
diyAudio Member
 
Join Date: Jun 2009
Quote:
Originally Posted by johnm View Post
I'd bet the DAC is downsampling the file you're playing. Simple to throw a couple of switches though and listen again using quad speed (the correct setting).

Regarding the toggle switches, you'd merely desolder the switches from the DAC board (VERY carefully so you don't damage the DAC with heat, and not to dislodge the tiny SMD resistors on the underside of the board), then run wires from the holes to toggle switches on the front panel. All you're doing is just adding some wire/distance between the switches and the DAC so not changing anything per se. Just make sure you get the switches the right way around so as not to muck up any sampling rate settings etc

EDIT: I seem to remember reading that with this DAC's USB input the max. sample rate was 48khz? Definately need some clarification on this. Generally I don't think you can get 192khz sample rate with bog standard USB (unless you pay for a big bucks converter)... For what it's worth I also bought a Mac mini recently, and am VERY happy using the optical output straight into the DAC. The Mac mini can output up to 24/96 using the optical connection (you have to select 24/96 from the Midi settings screen) and it sounds amazing through this DAC. I truly believe optical isn't as inferior as SPDIF as many would have us believe, at least from my listening tests and a decent optical cable from www.lifatec.com.
This is strange. I switched from double speed to quad speed and replayed the two high rez samples. Couldn't really hear any difference in sound quality (although these are great recordings). I then tried using iTunes, and my stored music played just fine (even though the DAC was still set for quad speed). Does this mean that the DAC is upsampling the 44.1 quality music in iTunes. (Again, I can't "hear" any difference in the sound from double speed.)

I seem to remember some discussion of owners preferring single speed with de-emphasis for playback.

The high rez samples download to Quicktime. I wonder if that has anything to do with the sound quality.

On the optical connection, I have a first generation Mini, which does not include the built-in toslink connection. I think USB is my best bet for outputting music.

Sorry for the Mac talk. I didn't mean to drag the discussion too far off topic.
  Reply With Quote
Old 26th August 2009, 04:58 PM   #1119
johnm is offline johnm  United Kingdom
diyAudio Member
 
johnm's Avatar
 
Join Date: Sep 2003
Location: Hampshire
You need to find the number of the chip that provides the usb-digital conversion s we can see exactly what is happening here, otherwise you're probably just getting upsampled audio I'd imagine.

As for playback for 99.8% of CDs out there you'd use the setting without de-emphasis.

For those using 16-bit what settings are you using? I have mine set to '0,1' (I2S up to 24-bit data) which I assume is the correct setting for both the optical and SPDIF inputs on this DAC???
  Reply With Quote
Old 26th August 2009, 05:11 PM   #1120
diyAudio Member
 
Join Date: Jun 2009
Quote:
Originally Posted by johnm View Post
You need to find the number of the chip that provides the usb-digital conversion s we can see exactly what is happening here, otherwise you're probably just getting upsampled audio I'd imagine.

As for playback for 99.8% of CDs out there you'd use the setting without de-emphasis.

For those using 16-bit what settings are you using? I have mine set to '0,1' (I2S up to 24-bit data) which I assume is the correct setting for both the optical and SPDIF inputs on this DAC???
I think its a pcm2902. So that means a max of 44.1 kHz, correct?
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
A.O.S - Any experience? Keltern Multi-Way 16 27th April 2012 12:15 AM
my t-amp experience Eggzy Chip Amps 35 17th December 2005 07:29 PM


New To Site? Need Help?

All times are GMT. The time now is 07:56 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2