AMB Laboratories DIY Audio

[nightanole]

http://nwavguy.blogspot.com/2011/05/amb ... e-amp.html

he posts under the diyforums as RocketScientist.

Some of his stuff doesnt add up, caps on the input on a dc design? plays into 15ohm at only 100mw (remember the youtube video of the guy powering his home sub from the mini3?)

[MisterX]

Looks like the ground channel op-amp in that sample has a problem, which is no surprise with no D4 (where did it go?).

Edit:
Who wants to bet the author didn't realize connecting the output ground from the amplifier to the "real ground" of his test gear borked the results?

[Anonanimal]

... no D4 (where did it go?).

Yeah...

I found myself wondering why he's not questioning/mentioning that fact that his board is, in fact, incomplete. Sure is a heavy wall of condescension on the design and I feel he could have checked into that board issue before carrying out all of the measurements...

[nightanole]

15db of gain into a 15ohm load

http://www.ybmaudio.com/products.html

here is the lucky guy that seems to make the full range of amb amplifiers...

[Beftus]

But the 60 hz hum spike surprised me given it was running from battery power. It’s nothing to worry about in this plot at –110 dB but where was it coming from? Batteries don’t have hum

I bet the 60Hz hum comes from his mains powered test rig.

Edit:

I really like this contradiction:

You can also buy an inexpensive Cmoy board/kit/amp using two 9 volt batteries on eBay and plug the same AD8397 op amp into it. Believe it or not, that combo will likely yield better performance than the Mini3

The AD8397 is a fast op amp and it demands very careful implementation.

What gives?

[particleman14]

oh its that fio guy. I remember he was hatin on the nuforce stuff as well. He sure has some strong opinions, wonder how he takes criticism? ;p

[amb]

There are definitely a number of questionable test bench methodology and issues that would grossly affect the results. As MisterX mentioned, active ground amps have to be treated with care when connecting to instruments or you'd short the output ground to the input ground. NwAVGuy made no mention of this. Many of the anomalies in his test results could be attributed to this. I could counter back on a bullet-for-bullet basis but frankly it's not worth my time. When he tested the amp and found problems, he should have either notified MisterX or myself to try to work them out before publishing it, but apparently he is too much of himself to do that. A lot of testing has been done during the Mini³ development phase, some of which are well documented in various forums. For him to insinuate that I had published dishonest specs is simply insulting.

[amb]

Btw, I got an anonymous email from someone telling me that the new Fiio E11 uses the AD8397, OPA690 and TLE2426 in a virtual ground, active ground configuration. I have not examined that amp, but if this is so, they must have "arrived at the same conclusion" as I did.

[Anonanimal]

Btw, I got an anonymous email from someone telling me that the new Fiio E11 uses the AD8397, OPA690 and TLE2426 in a virtual ground, active ground configuration. I have not examined that amp, but if this is so, they must have "arrived at the same conclusion" as I did.

That would be quite the pinnacle of irony...

Edit: There are mentions in FiiO's official E11 thread of the AD8397 in active ground configuration, as you described. I'd agree on your earlier point that this isn't really worth your time. Correct measurement > opinion.

[linux-works]

was he also testing with the volume pot not at full?

if so, then his crosstalk (at least) was not honest.