HIFIDIY.net PCM1798 USB DAC with Tube Buffer - diyAudio
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Old 4th January 2008, 01:12 PM   #1
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Default HIFIDIY.net PCM1798 USB DAC with Tube Buffer

Has anyone come across or bought one of these yet?

hifidiy.net USB Tube DAC

Specs are as follows:

DAC: PCM1798
USB Receiver: PCM2707
3PPM master clock
with an option of adding a tube buffer to the output stage.

They do a lower spec version of the kit, which has lower spec discrete components and a more jittery clock. That version is listed on the US site at $90

I think it all came to around 70 and I had to order it through their US agent (which meant the price went up a bit). It should hopefully be turning up soon and I was wondering if anyone else had done one, if I get stuck?

Annoyingly the kit does not feature any sort of S/PDIF in, there are only S/PDIF outputs. I plan to surgically implant a CS8416 to feed into the I2S bus from the existing USB receiver. Also if I can get it to work, an upsampling CS8421 ASRC (I can't seem to get this part to do anything with my TDA1543 as a prototype yet though).
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Old 4th January 2008, 01:47 PM   #2
dzkh63 is offline dzkh63  Hong Kong
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you can go to this : hifidiynet@yahoo.com. hurry up they are take another group buy for this DAC. they can mail to over sea. I bought one kit, but not yet finish. (I am from Hong Kong)
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Old 5th January 2008, 06:46 PM   #3
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....Anyone bought or going to buy one of these?

I feel like a bit of a guinea pig as the only forums etc on it are in Chinese.
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Old 5th January 2008, 07:03 PM   #4
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Why did they use PCM1798, not PCM1794?
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Old 5th January 2008, 07:22 PM   #5
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Because it's about 4 times cheaper, but S/N is 123db compared to 132db with the PCM1794. I'm happy with that compromise and it shouldn't be much work to replace it down the line if needs be. In fact, according to the datasheet they are pin compatible.
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Old 7th January 2008, 12:07 AM   #6
Ipanema is offline Ipanema  Malaysia
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Do you know why they have different pricing for their english site and chinese site?

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Old 7th January 2008, 06:51 AM   #7
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I was told that they are unable to accept Paypal in China, so that is why they set up a US agent. I'm assuming that the price difference is simply because they can and because you are ordering through a reseller, but in any case it's still very cheap for what you are getting. If you are lucky to have a friend in China who you can order through, you would be much better off!

I previously ordered the mini-TDA1543 kit from them and it's a lovely little DAC. After adding a further 3 TDA1543 chips on top of the existing one and tweaking the I/V it performs admirably.
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Old 17th January 2008, 10:44 AM   #8
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I'm glad to report that I assembled the DAC last night and it started up fine first time!

Unfortunately the kit doesn't come with any English instructions and it's not really possible to make any sense of the Chinese ones that came with it. Basically I had to rely on looking at photos dotted around the web on Chinese forums and the partial schematics to do the assembly. Generally speaking it wasn't that hard though and managed it in a night.

The kit itself consists of the main PCB, with the USB receiver and DAC ICs taped to it. All of the other components just come in a bag which meant a couple of bent pins on the opamps, but nothing drastic. The PCBs are very good quality and thick, with gold plated double thickness copper tracks.

The instructions consist of a page of Chinese and a partial schematic. A daughter board is provided for the optional tube buffer stage, but you need to get a dual triode valve which they will supply for about $5. I would also recommend buying their matching R-Core transformer (~$20), especially if you intend using the tube buffer as it needs a 60V supply and that transformer does all the voltages.

My first impressions of the sound are that it is very very good. This DAC sounds very detailed, clear and warm with my Tripath TA2024 amplifier. I hate to say it, but it generally sounds a lot better than my 4 x TDA1543 DAC. At times it can sound more predictable, but there is a much much better noise floor and it doesn't suffer from the annoying quantization cockups that the TDA1543 produces at low amplitudes. It's also a massive improvement on the sound that comes out of a standard Squeezebox 3, although that's not surprising really. I certainly don't feel a need to upgrade the DAC chip to a PCM1794 at the moment, the PCM1798 sounds great!

The next task is to give this little beauty a S/PDIF input, as currently it's USB input only with S/DIF outputs. I plan to piggyback a CS8416 to inject I2S and possibly make use of the existing low PPM onboard clock.

If anyone needs a hand with building this DAC, I'd be glad to help where I can.
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Old 17th January 2008, 01:38 PM   #9
xaudiox is offline xaudiox  Philippines
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Thanks for sharring bongoman! this is very interesting dac... i may consider buying one..
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Old 9th February 2008, 01:42 AM   #10
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Any more news about this HIFIDIY USB Tube DAC kit?

Still on the sidelines but would really like to try it out if there is some more info or review on it.

From what I can tell all one needs to add is a tin case, tube and a power supply to get the thing running. Is this correct?

Any pics or links of it built other than manufacturers website?

I would like to try a battery power suppy with it.


.Click the image to open in full size.

PS. As I've read in a couple of previous post's; it's becoming very hard to find out which one sounds better than the other as there is a slew of new usb dac's becoming available on the market but no real evaluation performed between them. All I hear a lot is "it sounds very good" comments but compared to what?

How would a would a Scott Nixon DAC, DAC707 Super Pro, Fubar, HeadRoom Micro DAC or Bel Canto compare? I am aware some of them cost more. Thanks
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