*** The DIY Audio Thread ***

[p4radox]

Just a small update. The current state of the Chinese DAC is:

Wire mod to enable 96kHz digital input and caps replaced with Os-Cons.

Output stage prototype.

Ghetto "coaxial" cable for testing.

 

[MikeHunt79]

Thanks for the advice, I think I may just try and keep it simple (for now). The idea is ave the DAC and pre-amp in the same box.

Right, I've just soldered up the connections and fired up the DAC for the first time and it works perfectly.

I was using my motherboards onboard DAC, and now I'm using the digital co-ax into the chinese DAC and it sounds a lot crisper and nicer. I just wish I done it sooner!

Right now my setup is:

PC (Volume set to 100%) > Chinese DAC (including op-amp output stage) > Dual gang Volume pot > AMP9

My plan is to have something like this:

PC (Volume set to 100%) > Chinese DAC (bypass opamp stage) > volume pot > homebrew output stage including 2-way crossover > AMP9

I'd also like some sort of switch which allows me to have a headphones mode which will use dual CMOY's and give me a balanced output for my HD-600's and an unbalanced for my HD-25's, bypassing all the crossover part... One step at a time tho...

I'm not really sure where to start really but I'm going to test out some crossover circuits on some stripboard first, and see how much power they use.

damian666 - It's never nice when something releases the magic smoke. Just put it down to experience and give it another bash.

EDIT: Paradox thanks for posting the pics, it makes things clearer. I also plan to mod the DAC with OS-cons and do the 96KHz mod, but I have yet to even order the caps as I also need to order some parts for a broken Cambridge A3i also.

Just a quick question: Are you powering your output stage from the PSU that powers the DAC? Any problems with this? I've found my PSU gives +12v and -15V but even so the DAC and op-amp works fine.

 

[p4radox]

I've had no problems with the DAC power supply, no. My rails are a pretty solid +/-12V

 

[MikeHunt79]

Hmm, I guess mine may have shown -15v as there was no load.

I'll test it with load and see what happens...

 

[adamau5]

I bet it still gives you -15.

I think damien666 had the same problem. He needed to change a regulator.

 

[MikeHunt79]

Just measured with music playing:

+11.87v
-11.95v

Awesome, that's good enough for me. I should have made a wager.

It's not uncommon for PSU's output voltage to be a bit high with no load.

 

[Katoom]

Here's my DAC and Amp6.

Sound great but i have a few Q's.
To bypass the op-amp stage, do i just remove the four caps and wire it to L- and R-?
Is it better to move the pot closer to the DAC or the amp? I would like to put it in the same enclosure as the amp.
How can i stop the "speaker hump" when powering on my amp.
I'm also getting a little background noise when the vol is down, i don't know where it's from.

Thanks guys, keep up the good work. I love this thread.

 

[adamau5]

looks good mate.

background noise may just be due to everything being uncased.

My amp6 can be a bit hissy when very close.

now the hard work - casing.

 

[adamau5]

on a different note your fuse looks too big for its holder.

theres a joke in there somewhere...

 

[p4radox]

Does anyone know where I can find a reasonably priced 4 pole 4 way (ie: 16 position) rotary switch? I reeeeeally need one and they all seem to be about £20!

 

[Katoom]

on a different note your fuse looks too big for its holder.

theres a joke in there somewhere...

I wired the big cap the wrong way around and blew the fuse. These were the only ones i could get. (min of 10) Robbing gits.
Made a couple of mistakes trying to rush it, like fitting the output caps before realizing there were 2 sizes Had to de-solder 3.
Chuffed when it finally worked though.

 

[MikeHunt79]

Does anyone know where I can find a reasonably priced 4 pole 4 way (ie: 16 position) rotary switch? I reeeeeally need one and they all seem to be about £20!

All I can suggest is the usual outlets really, maybe the bay, but also try asking on the "Electronics and Parts" section over at DIYaudio, I'm sure someone will know of one.

Sound great but i have a few Q's.
To bypass the op-amp stage, do i just remove the four caps and wire it to L- and R-?.

Yep, I think so anyway. You could use L+ and R+ instead, and I'd pull the op amp also as it would just sit there and draw power otherwise...

Is it better to move the pot closer to the DAC or the amp? I would like to put it in the same enclosure as the amp.

It shouldn't really make that much difference, just keep it away from power cables and you should be good.

How can i stop the "speaker hump" when powering on my amp.

The amp6 has a mute function. The best thing to do is have the amp muted for the first second or two after the amp is powered up. This will stop turn on thump. I'm guessing this is what you mean by "speaker hump"

I'm also getting a little background noise when the vol is down, i don't know where it's from.

Well, it could be one of many things. I use my speakers nearfield so I often hear background noise if there is any, I've used them with both the amp6 and amp9. What does the noise sound like? Does it sound like a low hum or is it more like white noise (sounds like an out of tune radio).

My amp6 with a crappy LCD screen 12v PSU gives off a nasty 50Hz hum thru the speakers, but when I power the amp6 from a battery pack there is no noise at all. This means my PSU is at fault. What PSU are you using?

My amp9 with 24V SMPS gives of no background noise at all. After hooking my DAC earlier, I'm getting 50Hz hum again! I have a feeling this it from the blue transformer than comes with the DAC, but it could also be a ground loop...

I've also just got it all hooked up on a desk also, once everything is in an earthed enclosure, and some shielding for the transformer, this hum should go. If it's still there I'll replace the transformer with a toroid type as these produce less RFI... We shall see.

Anyone else getting 50Hz hum from thier Chinese DAC?

 

[Katoom]

I'm using a Xbox Hd drive PSU, but didn't get any noise until i used the Pot and the DAC (i have the blue transformer too).
I will try the mute switch, thanks.

 

[adamau5]

earth the dacs ground. Without this it hummed with anything i plugged it into.

 

[Kanifee]

Nice to see these dacs getting some real daylight, they are a great proposition for a decent budget! I havnt sufferd any background noise but i did buy a separate trafo. P4radox, what kind of impact did you find the oscons made? still haven't got around to buying mine yet so im still running tants!

 

[p4radox]

There was definitely a difference. More "detail" is best way I could describe it. It wasn't a massive difference at all, but probably worth it.

I'm about to do the bypass mods on the rest of the SM caps, using the red Wima caps from the "Capcacitor games" page. I'll report back on the effect of those.

 

[Kanifee]

good good, how is the amp10 coming along?

 

[MikeHunt79]

earth the dacs ground. Without this it hummed with anything i plugged it into.

I'll give this a go, thanks.

EDIT: I notice the DAC has 2 grounds - digital and analogue, did you earth both of these?

 

[gurusan]

got my Chinese DAC up and running and installed in a case under my CMOY just for testing. Need to add some ventilation otherwise the voltage regulators will heat up too much.

Currently have it from my P5Q optical out and it sounds pretty good.
Next I'm going to swap in a LME49860NA opamp I have here, going to add a power LED, remove some caps and bypass the output stage to go straight to my CMOY.

I crammed the transformer in there (superglued it to the roof as far away from the DAC board as possible) along with the other audio components and can't detect any humming or EFI symptoms...but I will buy some copper tape for shielding and make some kind of shield just for peace of mind.

 

[adamau5]

be careful of the glue. Most glues do not stick to that shiney plastic and will eventually drop.

Also, i doubt you will need ventilation, those regs are dissipating much power to be honest.


What have you done to the poor opamp, it looks likes its dancing! tip for removing them, pliers to grip each end of the platic casing, and pull them out square,