diy build PIMETA vs Mini3

If you want it to be portable to use with IPOD, I like the size of Mini3V2.

I have had a few Pimetas and one Mini³. Honestly, the difference between the 24V and 9V Pimeta was barely discernable to me (if at all). The Mini³ is a trickier build, but IMHO does have a better sound.

I would happily recommend any of the three.

I think the Pimeta sounds way better than the Mini3, especially with different buffers (it's not like you can easily find BUF634 anyway).

I think you should go with the Mini^3. Its design is a bit more specific. The PIMETA is meant for the Serpac H65, not as good as the Hammond 1455C8 in the Mini^3. Personally, I didn't like the H65 since it doesn't stack as nicely as the Hammond, and the screws stopped working after a short while. Plus, with the Mini, there's a trickle charger built into the board, onboard charging jack, overcharge prevention so you don't explode your battery and possibly ruin your board, and shielding from the metal case. These things can be worked out for the PIMETA, but it won't be as neat or elegant. Also, switchable gain and bass boost is possible on the Mini, but again, neither neat nor elegant. I prefer the Mini as a portable because it's more convenient than a portable PIMETA: charging is a snap with the Mini since it uses the same size jack as my laptop charger; it's easier to travel with; plus everything is already board mounted, so opening it and tweaking things is very easy (though I wonder what you might want to change).

Don't get me wrong, they're both excellent designs and they do what they were meant to do, but I just prefer the Mini^3 as a portable. I use the PIMETA as a home amp paired with a TREAD, and the high performance Mini^3 as a portable. They have their own sounds, so I can just choose one or the other (or my Millett MAX) depending on what I feel like listening to. My suggestion, get a Mini^3.

Hope that helps.

The trickle charger was removed when the design went to v2 (v1 was never released). Likewise, there is no overcharge protection. The onboard voltage regulator takes 15-24VDC with a minimum of 300ma and outputs 16ma to the battery. The battery should be fine if left charging overnight, but I wouldn't keep it in for multiple days. Also, a gain switch and/or bass boost would be very hard to fit in if using the recommended case.

Hm, I thought that was what a trickle charger was. Also, I seem to have misinterpreted the overvoltage protection stated on the AMB site with overcharge protection. About the bass boost and switchable gain, I was trying to imply that it would be very hard to do, but in DIY, we never say 'die,' right?

Thanks for the clarification. Don't know where I picked that information up. Must do more reading...

A trickle charger is when the amount going into the battery lowers, or trickles, as the battery fills up. Like stated earlier, the Mini3 charger outputs a constant 16ma.

Right you are

I think the Mini³, two reasons. 1 it is a clean design that uses a really nice case. 2 has a charger built in, which makes it easier for portable use. I have had them both on a a/b switch and had a tough time telling the difference. The overall sound and the feel takes me to the Mini³.

I'd do a Pimeta with discrete buffers. I haven't heard a Mini3, but have built 2 Pints (1 AD8397/LM6172 and 1 2xLM6172) which are a similar amp design. The Pimeta I built sounds better (OPA2107/OPA227 and Mono discrete buffers). It is in a Hammond case (1" x 3" x 5") and has one of Tomb's trickle charger boards in it as well, with 2 x 9V NiMH.

I think both these are good choices, but as you mention,the Pimeta is an easier build, but not as small as the mini3. But then, it is much more flexible too, so you can build it to suit your needs, changing opamps, different parts, different buffers, build in your bass boost etc. This would be much harder to do on the mini3, and probably not really recommended. The mini3 is designed in a particular way, and you really have only two options--a build optimised for battery life and another for sound.

I would skip the cmoy for practice, and practice on the pimeta. I think if you want portable and size is an issue, then the mini3 would be what you end up with. But until you are sure of what you want, experiment with the pimeta.

I'm going to get slapped for posting these pics again, but Pars mentioned my Trickle Chargers, so here they are:




The trickle charger (I thought trickle meant a trickle ) is nestled between the two 9V, 250mah batteries. It's a TO-92 version of a LM317 with a couple of diodes and a current-setting resistor. The trickle is set to 12ma, which ends up charging the two batteries in about 21 hours. So, it's very conservative and I've experienced no ill effects leaving them plugged in indefinitely.

That's good, because both are stacked double-BUF634's. They will run about 4 hours between charges if I'm lucky. At least they run perfectly with a linear-regulated 24VDC, 500ma walwart (from Jameco) and will continue charging while playing. (I was looking for maximum performance in a portable package.)

One of them has AD8620/AD8610. The other used to have the AD8066/8065, which sounded pretty lean. However, I've since changed it to OPA637/627 and wow - it sounds like a desktop amp. That's an expensive set of opamps, though, but they're worth it as long as they're buffered well. (2x9V is also recommended for best performance from the OPA637/627)

The Panasonic EVJ leaks volume in one channel at high gain, so I lowered the gain in both - one's about 3, I think, but the OPA637 has to have at least 5 (it's 7). Other than that, and the very low charged runtime, they've been great. So, lots of things you can do with a PIMETA - if you can get the parts these days.

Thanks as always to Tangent and to Head-Fi user _redruM who originally came up with the trickle charger schematic and the shoehorned PIMETA in the 1" tall Hammond case.

Thanks!

Even though they're portable, those are more or less "Cadillac" PIMETA's - double buffs, OPA637/627, etc. There's probably $150 in each one.

As to parts, the important ones were already noted in the above post. The rest are standard PIMETA parts with an eye toward a 20mm height restriction. (The entire Hammond case is only 1" high.) The only exception is the trickle chargers, which use a TO-92 version of the LM317, a couple of diodes and a 75 ohm resistor. I did a "How-To" thread on the trickle chargers that I think was already referenced in this thread. The DC jack in back is an "outie" instead of an "innie" so that there's room in the middle to nestle the trickle charger between the batteries. The Pot actually secures the board to the front plate, while the batteries and their connectors actually sit on top of the back of the board, butting up against the buffer sockets.

The case looks so nice.

Where did you get the case? and how much?