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I can DIY, but I lack the time these days...
I'm also interested to see this. Did some quick searching (here and Google) and couldn't really dig anything up.
I found RMAA pimeta-V2 measurements.
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What sucks here is that 1 person (who has a vested interest in the success of the amp in this thread) has measured his amp on equipment that is basically unobtainable to the casual user.
An additional level of suck comes from the fact that there is no generally followed standard of testing headphone amps. One guy does one thing, the other guys do another.
A quote from that one person.....
And just to be clear, I'm not selling anything myself, and I don't get a penny of revenue from this design. It's open source hardware licensed under a Creative Commons License.
So where is this "vested interest" ?
The measurements will be verified by people who own that same equipment once all the details are released and the amps can be finished.
I think the measurements taken are pretty exhaustive. Which measurements are missing?
It is the nature of all people to promote what they are passionate about. The fact that someone does not profit financially from something does not mean that he does not profit in other ways.
Many articles have been written promoting open source (software generally, but it extends equally well to other things) clearly illustrating that you cant pay someone enough to do quality work, but they will do quality work basically for free if they get some personal/emotional reward for it. Its interesting that people often do BETTER work without monetary compensation then they do at their "real" jobs. Anyways, this reward is why people do this, and open source designers often have a stronger interest in their designs then people who are only in it for the money.
Considering that the schematics have been out for a single week, is it surprising that only 1 person has measured this amp?
Could be a purely altruistic desire to design an affordable (even at $75) DIY design, could also be for his ego, celebrity on the net... Could be all of those, who knows?
What important is that the design is released and if you could prove his measurements false, then it was much ado for nothing. If his measurements (even using less rigorous methods), we have a DIY design that "certifiably" measures well into 99% of the loads that it can encounter.
Let's go back to the design and not its designer..
I actually agree with this doublespeak, but let me translate it to English for the rest of the class.
"The 3 people who are interested in DIY amplifiers that own the same expensive test equipment as the designer can test it."
Its a good tactic really, limiting who can test an amplifier to a VERY narrow group.
Anyone who can built it will be able to measure it, no one will be able to prevent those measures neither will anyone be able to prevent posting those measures for everyone to see.
Maybe I missed it, but what equipment was used to test, and what tests were done? I've got a grip of test equipment at work, maybe I'll build one and test it.
can't go wrong with 30 bucks.. if anyone running a pcb group buy, i'm in for one
The amp was originally measured on a Prism dScope III.
$75 would be more accurate if you want accessories such as an enclosure.
And others are free to do RMAA testing aswell. I don't see the problem.
Interesting development, this amp. However I feel that in trying to prove the Mini³ is an underperfoming piece he has cheated IMO. What he has created is considerably larger than the Mini³. The O2 doesn't score points for pocketability... I would like to see his design for a single 9 volt battery amp that outperforms the Mini³ and still fits the Hammond 1455c801 enclosure.
The $30 figure taken out of context is pretty misleading, but in the original wording it was quite clearly stated that it was just the approximate cost of the PCB + components. If you take a look at the BoM it should be quite clear what the costs are. Comparing to other products, including shipping and all the other components, something a bit under $100 is more realistic. However, you can get a full functioning amp for just the PCB + components + AC wall transformer ($5.55), so if you forgo the enclosure and batteries, it should be in the range of $50 which is hardly onerous. One of the points was just that it doesn't use lots of $10+ op amps.
PCB is relatively simple and apparently (we'll see) supposed to be around $10. Group buys are great, but given that cost, the incentive is maybe not that high.
In the comments to one of the articles, Tyll popped in and offered to test one, if that means anything. Not sure if that's going anywhere.
I'd always take testing by the designer with a grain of salt, but I'm not sure why it's offensive that it was done on gear that's not available to the average user? You'd rather have it measured with less accurate equipment and with RMAA? It's not like the noise measurements, THD measurements, and so on, are soooo bizarre. You don't need to replicate the exact same tests to figure out if the performance is similar (or not) to what is being claimed.
edit: I kind of agree about the size. It is definitely on the fringe of "portable" for me. It's not exactly gargantuan, but likewise I wonder how a single battery design (maybe with DC-DC conversion for the other rail) would do. How large might a version be that does not use all through-hole components?