HiFi Audio DAC - Page 1
Forum section: electronics / projects

author: VingTor
author_rank: Contributor
timestamp: May 18, 2014, 06:23:16 pm
content: Hi allI guess you all are familiar with this situation, you start a project, then get side tracked into other projects, work and other hobbies. Several years passes, and you figure it is time to finish the project. This is at least my story, so here we go.During my years at the university I got a bit interested in HiFi Audio, and discovered that good audio quality (all though subjective) actually plays a difference when listening to music. So I invested in speakers, an integrated amp (tubes) and DVD/CD player with decent audio outputs (analog).The tube amp was a kit, and it only has two analog inputs, no remote. This is a bit annoying. So I decided to build a DAC with multiple SPDIF inputs, multiple analog inputs on a separate board, and an analog output board with volume control. So the entire system is made from multiple boards. Most of the schematics is based on application notes and recommendations from datasheets and is, lets say, straight forward.So, my question, power supplies, multiple of them. Datasheets does not say much about this, and I'm not sure what the best approach will be. The DAC board need multiple supplies, +3.3V and for the SPDIF receiver digital circuit and separate +3.3V for the PLL. +3.3V for the digital part of the DAC chip, and +5.0V for the analog part. I also need -15V and +15V for the analog circuitry after the DAC (IV-stage and filter). I was planing to make a separate board for the power supplies. Mains filter, transformer(s), bridge rectifiers, filter caps, and linear regulators. I guess one transformer for the +-15V supplies, and one transformer for the other supplies. The +-15V regulators will be on the power supply board, and I will star route power to the other boards from the power supply. There will then be some ground loops between DAC board, output board, and power supply (going through signal ground). I dont see how I can avoid this. Hopefully it will not be an issue.Then there is the other supplies for the DAC board. Will it be OK to go for the same approach, having regulators on power supply board and connecting with wires to DAC board, or should I use local regulators on the DAC board? I'm mostly conserned about the +3.3V for the PLL as the PLL clock is important for the overall system performance, and the +5.0V analog supply for the DAC.So, is this a good approach for the power supplies? Any recommendations or link to tutorials on similar topics?In the attached image you can see some inital layout of the circuit.

author: nctnico
author_rank: Super Contributor
timestamp: May 18, 2014, 07:15:10 pm
content: For the same voltages just use 1 regulator but use ferrite beads and capacitors to create clean power rails for the various sections.

author: retrolefty
author_rank: Super Contributor
timestamp: May 18, 2014, 08:07:31 pm
content: And then you go and ruin the whole system with a tube amp?

author: VingTor
author_rank: Contributor
timestamp: May 18, 2014, 08:39:13 pm
content: Quote from: retrolefty on May 18, 2014, 08:07:31 pmHehe, yes I am.The tube amp is quite nice actually. No bad hum/noise from the speakers so I think the SNR of mine is quite good, but I dont have any equipment to measure it in a good way. I like it at that is all I care about. The amp is named Ella and was bought from diyhifisupply. Seems to be a copy of Consonance M100 amplifier or based on it.

author: mariush
author_rank: Super Contributor
timestamp: May 18, 2014, 09:30:26 pm
content: Tom's Hardware recently had a nice article about high quality audio on pc... they tested several DACs with high end headphones (that get close to $1k at price):http://www.tomshardware.com/reviews/high-end-pc-audio,3733.htmlThey could notice a difference between the Realtek onboard sound card DAC and the others but they couldn't really say with high certainty that a particular DAC was better than other.. a $2k dac, a $300 dac, a $200 sound card, they all sounded almost the same in blind tests. One of the guys had $70k worth of equipment at home... no dice, they all sounded the same.Read the article, it's well worth the time.If you want to, just go and buy one of those $300 DACs and use a classic ac transformer with a bridge rectifier and some big caps to power it... that way you'll have the cleanest sound, to ruin with your tube amp.

author: dannyf
author_rank: Super Contributor
timestamp: May 19, 2014, 12:38:52 am
content: QuoteYou wouldn't be able to tell the difference either way, assuming decent decoupling.

author: theatrus
author_rank: Frequent Contributor
timestamp: May 19, 2014, 02:22:29 am
content: Don't sweat it too much. My preference would be a regulator pair per PCB, but the rest is just good decoupling practice.

author: miguelvp
author_rank: Super Contributor
timestamp: June 02, 2014, 02:46:47 am
content: A friend of mine bought one of this recently so far he is happy with it:up to 384KHz 32bit USBhttp://www.ebay.com/itm/XMOS-headphone-USB-DAC-384K-32bit-4layer-PCB-coxial-PCM5102-assembled-board-/251480960638diyaudio forum link:http://www.diyaudio.com/forums/digital-source/241156-new-async-xmos-384k-32bit-pcm5102-dac-ebay.htmlAnother source for that thread:http://www.hifiwow.com/dac-da-converter/xmos-pcm5102-32bit-384k-finished-dac-board-w-headphone-amp-197.htmlEdit: power supply regulator for the DAC talked about on that thread (seems to be out of stock):http://www.diyinhk.com/shop/home/34-17uv-ultralow-noise-dac-power-supply-regulator-33v55v-1ax4.html

author: theatrus
author_rank: Frequent Contributor
timestamp: June 02, 2014, 02:54:42 am
content: The gold-colored oscillators seal the deal :-/

author: miguelvp
author_rank: Super Contributor
timestamp: June 02, 2014, 02:58:40 am
content: Quote from: theatrus on June 02, 2014, 02:54:42 amMeh, to me 32KHz or 48KHz dacs are plenty, I live in Chicago (city) so anything over even 16KHz would be wastedEdit: but the parts look the part imho and for under $60 you are not going to find a commercial hi def DAC at that price point. Most of the commercial stuff is 96KHz and maybe 24 bits.