I bought the 513 variant of these last week and have it mostly set up now. I bought it after getting fed up with trying out an old Sony HCT 550 to listen to music streamed from a NAS to a tablet in the bedroom using a 35 buck bluetooth dongle.
I have a decent pair of speakers that weren't in use elsewhere, and was wondering about buying an Audioengine or similar higher quality bluetooth receiver when I ran across the 513. It ticked a lot of boxes for me - enough power to run the speakers, both BT and line in audio, small, relatively inexpensive at around $150.
The first discovery was just how bad Bluetooth can be compared to the headphone out jack on a tablet. Much of this is ROM dependent; I have two tabs, neither has aptx support, and one of the two plays over BT either terribly or so badly it's hard to believe, depending on which ROM is running. The obvious errors (loss of high frequencies, and in the worst case shifted pitch) weren't present using the wired jack.
However, there was another issue with the wired jack - when connected to a tablet, there was pink noise present at around 30 db below program level, and also a ticking sound audible once a minute.
I retired a WD TV Live Plus a bit back, so I tried plugging it back in and running analog out from the WD to the aux in on the Grace unit. The difference was night and day, and Grace probably ought to look at the design to see why there's so much noise present on the analog line when a device that's not plugged into the mains is feeding it.
Ultimately, in a configuration that's not what 95% of customers will use or be set up to use, the unit can sound OK, although I haven't sat with it and tried to do any serious listening yet. This is a bedroom system, of course, so there are constraints on speaker placement and the like - the system's a big convenience rather than intended to sound as good what's out in the living room.
I can't blame Grace for the poor quality of BT audio - I have one device that is OK with it, and another which is good or bad depending on what software is in use.
The design of the analog in, though, is really too bad since I don't know how many folks will be able to deal with the issues it presents.
That said, once I got it set up, I have a listenable way to get BT audio when I choose to use it, and in combination with the WD gear a DLNA/UpNP renderer that sounds OK.
Is it worth $150? Probably not for most people, given the issues with the aux input. Although, it seems that's an issue with a lot of this style of amps - that folks are hearing a lot of noise on the aux input. Not sure how many of those with the noise reports are using a free-floating signal and how many have the source connected to house power.
While looking into the aux in noise, I didn't see any glaring problems in the internal assembly.
the key components seem to be:
- Wolfson 8731s codec
- TPA 3116 A284 under the heat sink and thermal paste
- NEC c4556 op amp (?) - the chip is labeled C4556 and that's apparently a NEC op amp
- TI CD4052B mux and a
- PT2313E (volume and tone control?)
