I've built this USB DAC kit http://www.audioworkshop.com.hk/report/d3/d3.html and found the board & parts to be very good (all dale resistors, Elna Silmic & cerafine caps & Wima caps). Board options are excellent - jumper for internal DAC or switch to onboard TDA1543 I2S in non-os with own PSU.
I have listened to it in stock form USB powered, standard crystal & the sound from the PCM2706 internal DAC is stunning - the hackneyed phrase springs to mind - "I'm hearing things I never heard before" - Pink Floyd Wish you were here intro of ststic radio with a short conversation between a male & female is now crystal clear & you can actually follow the conversation. As well as the detail the presentation is v good top to bottom - this is all on my test speakers & not my mains.
With this good a sound in stock form I am keen to push it further (although I have heard that the internal DAC is better than non-os TDA1543) - the board has a jumper which can switch to I2S.
I haven't yet been able to get I2S working - looked over schematic & circuit board & soldering & can't see any problems - maybe someone here can help (schematic attached).
I'm also keen to set it up for self power - I will probably start with just disconnecting USB power pin 1 from USB plug & connect to regulated 5V supply - I have heard that if this power is turned on before D+ it can burn chip - how have other people applied self power?
My next step would be full self power - regulated 3.3V & 5V to appropriate PCM2706 pins - how have people implemented this? - I have some nice 3.3V boards salvaged from Dell computers which should work nicely here.
Any help greatly appreciated
John
I have listened to it in stock form USB powered, standard crystal & the sound from the PCM2706 internal DAC is stunning - the hackneyed phrase springs to mind - "I'm hearing things I never heard before" - Pink Floyd Wish you were here intro of ststic radio with a short conversation between a male & female is now crystal clear & you can actually follow the conversation. As well as the detail the presentation is v good top to bottom - this is all on my test speakers & not my mains.
With this good a sound in stock form I am keen to push it further (although I have heard that the internal DAC is better than non-os TDA1543) - the board has a jumper which can switch to I2S.
I haven't yet been able to get I2S working - looked over schematic & circuit board & soldering & can't see any problems - maybe someone here can help (schematic attached).
I'm also keen to set it up for self power - I will probably start with just disconnecting USB power pin 1 from USB plug & connect to regulated 5V supply - I have heard that if this power is turned on before D+ it can burn chip - how have other people applied self power?
My next step would be full self power - regulated 3.3V & 5V to appropriate PCM2706 pins - how have people implemented this? - I have some nice 3.3V boards salvaged from Dell computers which should work nicely here.
Any help greatly appreciated
John
Attachments
You can buy it here http://www.audioworkshop.com.hk/index_en.htm and for $60 it's a real steal with quality parts as I said.
HP section is the headphone/Line output - this is what I have connected into t-amp and it makes a fabulous portable unit.
I have no afilliation with this company.
On the Pink Floyd track I mentioned "Wish you wre here" apart from the conversation over the static radio noise being crystal clear I noticed a sound there is also the clear sound of someone (Gilmour?) clearing his throat on one channel.
Further playing with Nora Jones, Diana Krall, Aslan have revealed much more atmosphere in the recordings and voices & singing that are now more characterful (more like their live voices).
John
HP section is the headphone/Line output - this is what I have connected into t-amp and it makes a fabulous portable unit.
I have no afilliation with this company.
On the Pink Floyd track I mentioned "Wish you wre here" apart from the conversation over the static radio noise being crystal clear I noticed a sound there is also the clear sound of someone (Gilmour?) clearing his throat on one channel.
Further playing with Nora Jones, Diana Krall, Aslan have revealed much more atmosphere in the recordings and voices & singing that are now more characterful (more like their live voices).
John
Delivery is quick about 10 days to Ireland from Hong Kong but I had to go on a waiting list as it is heavily over ordered.
Yes it does I2S, / SPDIF, Optical & Headphone output. This is selected by a jumper on board - I haven'y got I2S SPDIF or Optical working yet - trying to sort it out but headphone output is great.
John
Yes it does I2S, / SPDIF, Optical & Headphone output. This is selected by a jumper on board - I haven'y got I2S SPDIF or Optical working yet - trying to sort it out but headphone output is great.
John
The how to build it page gives lots of details. Far as I can tell, there's a jumper to let you switch between the Burr Brown or the non os 1543. A few posters on their forum have problems with the 1543 not working.
However, jkenys' report on the BB dac makes that worth the price of the kit imo so if I get it and the 1543 also works, that'll be a bonus.
However, jkenys' report on the BB dac makes that worth the price of the kit imo so if I get it and the 1543 also works, that'll be a bonus.
I like it a lot(see first post) & if I get I2S working & TDA1543 filterless non-os I will consider it excellent (even if I prefer the internal DAC in PCM2706 - I still will have heard non-os DAC sound)
The PCM2706 is a USB receiver with a built in DAC which can be used for SPDIF/optical out & headphone out....... or with an on board jumper you can switch to I2S output & listen to external DAC which is also on board TDA1543
Anyway I'm not finished with it yet - there are mods to bring it up another level - power PCM2706 from external regulated supply rather than from USB bus.
John
The PCM2706 is a USB receiver with a built in DAC which can be used for SPDIF/optical out & headphone out....... or with an on board jumper you can switch to I2S output & listen to external DAC which is also on board TDA1543
Anyway I'm not finished with it yet - there are mods to bring it up another level - power PCM2706 from external regulated supply rather than from USB bus.
John
Nice to see that at least one person is pleased with the pcm's internal dac
It seems that the audiophile view is that pcm sucks / tda rocks
I for one did not have a chance to hear the tda, only a self-made pcm2702 so all I can say is that it performed on par with a Vincent cdplayer (the only not-quite-cheap unit I had access to). Maybe one day I'll take a try on the tda.
It seems that the audiophile view is that pcm sucks / tda rocks
I for one did not have a chance to hear the tda, only a self-made pcm2702 so all I can say is that it performed on par with a Vincent cdplayer (the only not-quite-cheap unit I had access to). Maybe one day I'll take a try on the tda.
My AW-D3 kit arrived this morning, looks good. Going to practice soldering for a few days before starting on it as I've done nothing serious with an iron for 20 years.
Lots of mods to try once built as well. I'm a bit worried about the potential to blow the chip with an external 3.3v supply. Am I right in thinking this is only a danger if you don't use the internal 3.3v reg of the 2706?
iow, if I cut the 5v supply from the usb cable and instead use an external 5v to the same pin there is no danger to the 2706?
Lots of mods to try once built as well. I'm a bit worried about the potential to blow the chip with an external 3.3v supply. Am I right in thinking this is only a danger if you don't use the internal 3.3v reg of the 2706?
iow, if I cut the 5v supply from the usb cable and instead use an external 5v to the same pin there is no danger to the 2706?
danb1974 said:
well, if this is based on pre-occupation, you are right. I have built also (details here .... an USB - TDA1543 DAC based on the PCM2707 and must say, that although the sound from the PCM2707 is not bad (level good CD player) it is no where in comparison with the output from the attached TDA1543 DAC ..... It is the way it is, which is relative. Which means hat you can be please for 100% with the 2707 built in DAC. But in absolute terms it can't hold up against some serious DAC approach (not even need to be a 1543...)
Indeed, you can switch around if you want internal DAC (then data gives SPDIF out) or I2S (DAC silent and data is I2S) see details in my ciruits.
These ciruits also provide a solution for the (read the datasheet) the requirement to avoid back voltage when an external supply is being used.
Just my thoughts .....
doede
Johnthedoctor,
Hmm - my AW-D3 kit never worked for I2S or SPDIF output only analogue headphone output. General consesus on other threads is that PCM chip is sensitive to ESD & can easily be damaged - be careful in handling it.
I have finally convinced Audioworkshop ( after many weeks of emailing) to provide a bare board as replacement since it was damaged from when I received it.
One other area of warning - when supplying external 3.3V to chip ensure USB D+, D- are connected first (as per datasheet) i.e USB cable is plugged into PC before self power is turned on - otherwise this can apparently damage the chip - although there are users who have reported many hundereds of plugging in & out in any order without damage to chip?
Finally, USB Vbus should connect to PCM HOST pin when in self power mode - this senses when USB is attached/detached. Don't know exactly what effect this has but the datasheet specifies this.
John
Hmm - my AW-D3 kit never worked for I2S or SPDIF output only analogue headphone output. General consesus on other threads is that PCM chip is sensitive to ESD & can easily be damaged - be careful in handling it.
I have finally convinced Audioworkshop ( after many weeks of emailing) to provide a bare board as replacement since it was damaged from when I received it.
One other area of warning - when supplying external 3.3V to chip ensure USB D+, D- are connected first (as per datasheet) i.e USB cable is plugged into PC before self power is turned on - otherwise this can apparently damage the chip - although there are users who have reported many hundereds of plugging in & out in any order without damage to chip?
Finally, USB Vbus should connect to PCM HOST pin when in self power mode - this senses when USB is attached/detached. Don't know exactly what effect this has but the datasheet specifies this.
John
I've read over the 2706 datasheet and the schematics from dddac a number of times, gradually getting the gist of what the chip does. (I hope.) I take it applying 5v from the usb to Host activates a relay of sorts inside the chip so that the 3.3v supply isn't used until it's safe to do so. Or have I got that wrong?
dddac, I see inputs from the usb and the 3.3v supply to the 74HC08 and the output goes to the usb D+ line. I'm guessing it's to make sure the usb is connected but can't figure the actual operation of it.
Reading the Audio Workshop circuit, I see they have the external 3.3v line going to Host, sort of defeats the object of making sure the usb cable is connected to the PC doesn't it?
I'm at that stage where I'm realising just how much I don't know. Don't want to solder any part of the kit until I understand more about it, ie. what gives me the best chance of having the 1543 working.
dddac, I see inputs from the usb and the 3.3v supply to the 74HC08 and the output goes to the usb D+ line. I'm guessing it's to make sure the usb is connected but can't figure the actual operation of it.
Reading the Audio Workshop circuit, I see they have the external 3.3v line going to Host, sort of defeats the object of making sure the usb cable is connected to the PC doesn't it?
I'm at that stage where I'm realising just how much I don't know. Don't want to solder any part of the kit until I understand more about it, ie. what gives me the best chance of having the 1543 working.
The AND gate only apply pull up to D+ when Vbus of the USB port and external power supply +3.3V both are "high".johnthedoctor said:
The reason why you must not apply pull up to D+ when Vbus of the USB port is not active (but still pluged) is to prevent back voltage going from D+ to the USB port's Vbus through the PCM, wich could damage it.
It is fine to connect/disconnect the USB plug while the PCM is externaly powered and D+ pulled up.
What you can't do safely is apply pull up to D+ while the DAC is plugged to a PC totally powered off. Note that if the PC is shutted down but plugged to the mains, Vbus of the USB port is still active.
akira
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