[lacro]

The DAC is an CDAC+, an optimized ODAC that's described here: http://www.head-fi.org/t/694411/cdac-modded-odac
I'm not sure of the output impedance for the CDAC+ but I've read the ODAC has an output impedance of over 400 ohms. Unlike the ODAC, the CDAC+ has an external 5V switched power supply.

The Sure itself is powered by an 18v smps that I salvaged from an old router. I'm using the MacBook's system volume to control the volume.

EDIT: I tried a different DAC (standard ODAC powered via USB) and a different power supply for the Sure amp (18V wall wart from an ancient laptop). The buzz persisted, but less loud. I then tried the ODAC again, but replaced the RCA connection to the amp with a TSR cable. Still an annoyingly audible hum/static, but far less loud than with the CDAC+ and the loud buzz.





Also, note that the Sure is not equipped with ferrite beads yet.

Did you try taking your DAC out of the picture, and just running the Motherboard DAC on the MacBook? I use a Schiit Modi USB DAC, and it's all dead quiet with the 3110 amp (with volume pot) on 2 different computers. Also, try a 12V battery to power the amp instead of the PS.

[mboxler]

Did you try taking your DAC out of the picture, and just running the Motherboard DAC on the MacBook? I use a Schiit Modi USB DAC, and it's all dead quiet with the 3110 amp (with volume pot) on 2 different computers. Also, try a 12V battery to power the amp instead of the PS.

The only way I could get my Modi to stop buzzing was to use the front USB 2.0 ports on my Windows 7 PC.  I had trouble with the 2.0 and 3.0 ports on the back. 

Unfortunately, I had to take the Modi out of the loop, due to constant static issues, most of which would mess up other USB devices, resulting in a reboot.

Too bad...the little Modi sounded great 

Mike

[rhing]

An easy next mod would be trying out different inductors. I and KJA at diyaudio were impressed with Bourns, but there are many options. Lots of fun to be had.

I've already assembled a BOM for parts to order from either Mouser or Digikey. I'm going to keep my stock board intact and order another amp for future modification.

I have more listening to do, but I think the Nichicon or Panasonic electrolytic caps would be better for this amp rather than the Elna Silmic II's on the power supply rails (i.e., two caps on either side of the TPA3116D2 chip). KJA at diyAudio advised me that he really likes the Nichicon ES Muse bipolar caps. This amp is already warm sounding and can benefit from more neutral-sounding power supply caps. I already have a pair of Nichicon KZ Muse 470uF / 25V caps that I never used in a previous project. Will I sacrifice any bass moving from 1,000uF / 25V to 470uF / 25V caps?

Both Digikey and Mouser carry the Bourns toroid inductors (Bourns PN 2100HT-100-V-RC) you and KJA really liked with the YJ red TPA3116D2 amp. With the confined space for each inductor, is it possible to bend the inductor legs to orient the inductors at a 45 degree angle rather than straight across the solder pads?

I'm also considering Wima MKP10 metallized Polypropylene film caps to replace the Epcos B32923 X2-class metallized Polypropylene film caps. I've used them before as signal coupling caps and they sound great after 20-30 hours of listening. For now, I still have more listening to do. This amp will require more burn-in time before I make any final judgment calls on mods and tweaks.

The only way I could get my Modi to stop buzzing was to use the front USB 2.0 ports on my Windows 7 PC.  I had trouble with the 2.0 and 3.0 ports on the back. 

Unfortunately, I had to take the Modi out of the loop, due to constant static issues, most of which would mess up other USB devices, resulting in a reboot.

Too bad...the little Modi sounded great 

Mike

Go analog. Vinyl rules!

[thaddeussmith]

Following over from Klipsch and AK forums since there seems to be more talk about this amp here. It's said the little yuanjing 6n3 + 6z4 rectifier pre-amp is a great match with the TPA3116. My DAC/Preamp has much more precise volume control (and a remote) - Is there any reason I can't just run the yuanjing pre wide open for the tube buffer benefits?

[HaroldHill]

Thanks, all, for your tips on my noise problem. I decided to take the path of least resistance and worked with my ODAC connected via TRS cable to the Sure (this setup had the least noise in my initial tests). It turns out the problem was with an external hard drive connected to my MacBook via a Thunderbolt adapt. I disconnected that one external drive and it's much quieter.  It's not dead silent now, but a slight hum is only audible between songs and during very quiet passages. BTW, unplugging the USB drives made no difference. And unplugging the power adapter from the MacBook actually made it noisier.

So far, very much enjoying this little stock amp with my Hifiman HE-6 headphones. Better than the tube amp I was using. Most appreciated difference: pianos sound like pianos. (Something about the attack and decay with the tube amp just didn't sound right.)

[Folsom]

Did you have both hd and mac adapter unplugged with more noise? This sounds like ground loop. If not a USB transformer might work.

[HaroldHill]

If the hard drive is connected to the thunderbolt/firewire adapter, I get a lot of noise. But if I unplug the hard drive but leave the adapter in place, it sounds just fine.

It's bugging me that connecting the DAC to the amp with RCA cables generates a lot of noise, but not with with a TRS cable. Should the hookup wire that connects the female RCAs to the amp board be shielded?

[Folsom]

Did you try disconnecting the laptop AND hard drive from the wall?

Again, it sounds like a ground loop.

The hard drive may be grounding through the amp, and so may be your laptop.

A friend of mine gets noise if his speakers (active monitors) are plugged into the same strip as computer charger. If one is plugged into a device with ground loop blocker no noise. Unpluggin the laptop charger also gets rid of noise. He uses USB device for playback (He makes music).

If both devices are plugged into power strip with ground blocker he gets noise.

[rhing]

If the hard drive is connected to the thunderbolt/firewire adapter, I get a lot of noise. But if I unplug the hard drive but leave the adapter in place, it sounds just fine.

It's bugging me that connecting the DAC to the amp with RCA cables generates a lot of noise, but not with with a TRS cable. Should the hookup wire that connects the female RCAs to the amp board be shielded?

I can tell you that using the Ferrite beads and shielded cables from the RCA connectors to the Panasonic volume pot on the TPA3110D2 reduced noise. I still hear a very faint hiss when I turn the volume up with no music playing. It can't hurt, but I suspect you will need trace your ground paths too.

With the Yuan Jing blue amp I received last week, I had this faint hum in the background that was bugging me. I added shielded cables, and it did reduce other noise, but not the faint hum. This faint hum seemed a bit stronger on the right channel. I looked at everything on the amp and around the amp including cabling. I noticed the the right channel input cap was oriented in an opposite direction compared to the left channel cap. I desoldered the right channel cap and oriented it identically to the left channel cap. In desoldering the right channel cap, I noticed a cold solder joint. I could practically pull out one lead of the cap without having to reflow the solder. So. I reoriented the right channel cap and touched up most of the thru-hole solder joints on the Yuan Jing blue amp board. I connected it to my preamp, and voila, no hum, hiss or any other noise. Who knows what the real root cause of the hum was, but it's gone now. Sounds even better with a dead silent background.

By the way, my left and right channel caps are now oriented such that when you read the writing on the side of the cap, the signal is flowing from right to left (i.e., opposite direction from normal reading direction of left to right).

[Wind Chaser]

I was considering one of these...

http://www.ebay.com/itm/FINISHED-Class-D-AMP-TPA3116-2-1-amplifier-2-50W-100-W-AQ-/400567805660?pt=US_Amplifier_Parts_Components&hash=item5d43b3a6dc

Working voltage: DC18V to DC24V -- Any recommendations for a power supply and where to buy?

[Folsom]

Those ones don't sound good with the 100w channel added. Sorry to say.

[HaroldHill]

For the moment, I can live with the slight hum. Even wearing headphones, it's only slightly louder than the ambient noise around here. The real annoyance is not knowing why connecting the DAC and amp with a TRS cable gives me just the slight hum while RCA cables spew out the noise. I know when I figure it out, it will be facepalm time, but until then....argh.

[Folsom]

TRS = 110-165ohm . It's make the voltage divide of the ground loop more toward the other devices.

Not trying to be rude but I think it's clear what's going on and either you are not believing or don't understand.

You still have yet to say if you tried fully battery powered playback except the amp.

What kind of solution would you like? Price?

[Wind Chaser]

Those ones don't sound good with the 100w channel added. Sorry to say.

Which are the better ones? Is it plug and play, as in it's not DIY, but mounted inside a chassis? And what is the preferred power supply?

[Poultrygeist]

If you buy the $5 RCA gray cable that snaps into the socket on the board it's plug and play. This one is playing from the PS1.

[HaroldHill]

My apologies (and embarrassment), Salis Audio, for my ignorance on matters electronic. I did, though, run everything but the amp from the laptop's battery.

...BTW, unplugging the USB drives made no difference. And unplugging the power adapter from the MacBook actually made it noisier....

Now, I offer cause for my further embarrassment. I retried everything again today. Except I cleared away cables from other electronic devices that were nearby and used a different pair of RCA cables. And the problem with using RCA cables has disappeared. The silence is pitch black (regardless of whether the laptop and DAC are powered by the laptop battery or laptop power adapter). Frankly, I think it's the cheap eBay RCA connectors I used on the amp. (But if I'm wrong on this, please educate me.)

Thanks again, all, for your help.

[Wind Chaser]

The above is cheap, but not very cheerful.
The image below is more tearful than cheerful.
I'd like something a little more on the cheerful side.

[matt_garman]

After soldering each wire in place, I slid a short segment of 14AWG Teflon tubing over each soldered joint to avoid possible shorts. It also serves as a strain relief.

Where do you get that Teflon tubing?  Basic google searching has only resulted in bulk quantities that are quite expensive.

As an alternative: how about coating the soldered pot leads with a big glob of hot glue?  Definitely cheap and easy, but is there any downside?

[Poultrygeist]

Naked board amps like many naked people look better with clothes on. A $5 decor box and a little imagination goes a long way.

The above is cheap, but not very cheerful.
The image below is more tearful than cheerful.
I'd like something a little more on the cheerful side.

[Wind Chaser]

Ordered two naked... http://www.yuan-jing.com/tpa3116-class-d-stereo-amplifier-board-50w-50w
One of these... http://www.yuan-jing.com/ac-dc-adapter-universal-switching-mode-power-supply-smps-24v-5a
And this... http://www.yuan-jing.com/Stereo-RCA-Interconnection-Board

Decided to buy two amps in case one goes down on me. Scary thought.