[Learnincurve]

Hi There!

   Googling, I stumbled on this http://www.audiocircle.com/index.php?topic=78737.0 thread.

I bought a HiFi360 HF-D1B recently as a combined stereo/5.1 decoder/dac/preamp.

http://www.hdcc.cn/up_files/image/product/2013/05/27/65947962.jpg
http://www.hdcc.cn/up_files/image/product/2013/05/27/65947963.jpg
http://www.hdcc.cn/up_files/image/product/2013/05/27/65947964.jpg
http://www.hdcc.cn/up_files/image/product/2013/05/27/659479610.jpg

It's alright as a combined product, but I'm pretty sure that it could be made a lot better with a few modifications.

I'm a novice. I can solder if I follow instructions and I've read up enough on electronics basics to know that there are a heck of a lot of mistakes that someone like me can make if I think I know anything.

There's no schematic available for the unit, so for starters I'll have to pull it apart and with help, try to understand what the bits of it do (I might buy another just for playiong about with as the first is in use).

So my question to the forum is if anyone would be interested enough to help me find out what's going on with it, what I might improve and how.

First thoughts are

• upgrading and stabilizing the power power sources
• upgrading the caps and bypassing where appropriate
• upgrading the resistors with low-noise alternatives
• rolling the op amps with proper
• rolling the op amps with proper power-rail decoupling (the wheeeee-POP I get when I cut the power to the original tells me that the stock NE5532s are oscillating )
• replacing the simple crystal oscillators with stable clock sources

There may be more and looking at wushuliu's excellent thread on upgrading 2 channel dac's I am sure that there is, but hey. I have to start somewhere.

Speaking of starting I still have a power-amp to build first, so won't be able to start on the preamp/decoder for a while. But if anyone is interested and can come up with some good ideas or practical help along the way (or want's to try it themselves) then here's the place. I'll be watching.

[Folsom]

The PSU caps are already very nice if they are what I think. You'd need Nichicon Gold's to upgrade. (they are more expensive, but we are talking like $900 for them)

What opamps does it have?

What do the blue caps say on them? Can you follow the tracings to see which caps are used for output?

Perhaps low noise diodes are an option. OS-con caps for supplies to the chips as well.

Really just need a schematic.

[Learnincurve]

Hi Salis Audio and many thanks for your reply.

The box is unfortunately in use at the moment so can't answer you in detail about the caps just yet.

Ops are "standard" NE5532's. There's a "De-luxe" variant of this, called the HLLY TMK-III with a toroidal transformer, ops in dip sockets and one or two other improvements. I would certainly want to add the sockets and try out different ops as part of any improvement - and try to get rid of any oscillation that the current setup is displaying.

I wish a schematic were available, but it's not. I've tried to ask the factory through several suppliers and all say no.  On the bright side, quit e a lot of these Chinese devices are built around the standard applications sheets provided by the chip manufacturers. They just string them together. So with a bit of time and effort it should be possible to piece together something and identify what the parts are doing.

[Russtafarian]

Let me start by saying I'm not trying to rain on your parade.  Just want to help you set realistic expectations for what you are attempting.

It looks like the unit is primarily a Dolby Digital/DTS decoder for TV/DVD sound.  If you are looking to play back high resolution multi-channel audio files like 5.1 24/96 PCM or even 5.1 DSD via USB, I don't see anything in the specs that indicate the unit will do that.  And given the lossy limitations of DD/DTS, I'm not sure modification will make a substantial difference in sound. 

If you want to mod it in order to learn and experiment, go for it!  A couple things you can do: install dip sockets to try different op amps, add bypass caps to the electrolytics for extra noise filtering, replace the rectifier diodes with hexfreds. 

Good luck.

Russ

[Learnincurve]

Hi Russtafarian


Thanks very much for your input. I was hoping to improve 2 channel audio as I don't really have any multi-channel sources apart from film.

Can you see anywhere whether I might expect to improve the 2 channel DAC performance?

Cheers!