DorkVader wrote:This is, in my opinion a good post. I'm not knowledgeable enough (yet) to know if it's right, but it's well worded, and easy to understand.
Thanks. I'm trying
Here's what I think: You should design a small, 2-battery, 2-channel "portable"-size amp like the one you describe.
I might, you never know But, honestly, I measure products like the FiiO E5 and E7 and think "why bother?". You can't buy the front panel of the Mini3 for the price of the FiiO E5. And I can't do anything about the price of low volume front panels. Yes, I could certainly design something that outperforms both of them, but would it sufficiently outperform the $120 E9? I don't know... It's easy to beat China Inc when they get it obviously wrong, but when they get it mostly right, it's very hard to beat them unless cost is relatively unimportant (and for most of us that's rarely true).
When you say you'd spend the money saved on having only 2 channels on a second battery, do you mean you'd have one for +, one for - and the virtual ground inbetween? Since the batteries will discharge separately, won't you end up with poor long term performance (if one battery is at, say, 9V and the other at 8V)
See my last post. With two batteries, it's not a "virtual ground" it's a REAL ground. No active distortion inducing, current limiting, battery munching, non-linear (the OPA690 is all these things) parts required.
As far as "what ground channel amp would you use" question, it's not meant to be a loaded question, but I do see your point. The "trick answer" is that you wouldn't use a 3-channel design. But let's say there's a huge market for these newfangled 3-channel amplifiers
I really haven't thought about it. It's like asking a Porsche owner which chrome exhaust tips he'd buy at Walmart for his new 911. He'd probably reply with something like "None because I'm not into fake chrome exhaust tips". He'd buy a real exhaust system. Real is generally best. Edit: I'm still waiting for someone to explain if there's some sort of benefit to 3 channel designs I've missed?
Hmm, if you leave the ground channel unpopulated (like what the balanced (2-board) mini^3 people do) would it perform better? I feel like that's easy to test.
Hmmm... I'd have to think about running the Mini3 bridged if that's what you're suggesting? You would need either a balanced source or modifications to invert the signal. Bridged amps, in some ways, suffer from some of the same problems as fake grounds. The load "sees" two amplifiers instead of one. That generally means more distortion, degraded specs, etc. It would roughly double the maximum output swing much like 2 batteries and you could get rid of the dreaded OPA690 and fake ground. But it's still not as clean of a solution as 2 batteries.