Project FAQ

Here are some questions people often ask when first looking at building a PIMETA.

Are the PIMETA boards still available?

No, sorry, I’ve discontinued all of my project boards. The design files are here, if you want to make your own.

I’ve never built a headphone amp before. Can I build a PIMETA?

You will need to know basics like how to solder, how to read a schematic, how to wire a toggle switch. Some have made it their very first electronics project, but you might want to get some soldering practice in on something less expensive before you begin assembing a PIMETA. For example, a CMoy Pocket Amp.

If you’re completely new to DIY electronics, first read my article Getting Started in Audio DIY.

There’s an awful lot of stuff to read here. Do I have to read it all?

The more you read, the more likely you’ll build the amp correctly.

At minimum you’ll need to read through the Part Selection Guide. There are no parts kits available, so you need to read this page to learn how to choose the parts you’ll use to build the amplifier. There is no single “correct” set of parts, but there are infinite wrong choices you could make. This section will tell you what works and why. Please read all the details about a part before you ask a question about it; you may be surprised at how often the answer is in the documentation.

You may also find the Part Lists page handy. This page lists almost everything you need to build a working PIMETA. You still need to read through the Part Selection Guide to learn how to choose among the alternatives given on that page. Also, you need other parts that cannot be listed on that page because they depend too much on your particular situation so I cannot recommend anything specific.

Once you’ve chosen your parts, you probably need to read the Step-by-Step Assembly Guide and Assembly Tips pages to learn how to assemble those parts into a working amplifier. If you’re new to building amps, you may even wish to skim these sections first, because the Part Selection Guide will make more sense when you know how the parts will be used. If you are an experienced DIYer, you may be able to skip these sections entirely.

Once the amp is working, you may wish to read through the Tweaks page.

That’s pretty much all the documentation, so the short answer is, “yes.” :)

I’m confused by the number of choices I have in choosing parts. Help!

If you don’t want to think about part values, just use the ones given on the schematic. The schematic shows a working configuration, though arguably not the best configuration for any given purpose. There is no substitute for knowledge and experience.

There are many “optional” parts. How do I know if I need them?

Most of these parts are optional only in the sense that the amplifier will function without them. The only parts that are easy to justify leaving out are C4, ZNR/FET, R8 and R10/Q1/Q2. There are more that can be left out for specialized purposes, but knowing which and why takes experience.

What’s the best way to save money on parts?

The most effective way to hold down the cost is to use just one buffer per channel, moderately-priced op-amps, the RK097 volume control, and a cheap enclosure.

Leaving out all the parts listed in the previous answer will save a buck or two.

If that doesn’t save enough money, be careful about choosing cheaper parts than those recommended in the documentation. It would be better not to build the amp at all than to go too far down the quality scale.

Can I use parts not mentioned in your parts list?

Yes. The parts table is more a list of examples than anything.

But before buying a part not mentioned on these pages, do a search in the Head-Fi DIY forum archives; someone else may have used the part and reported on it, or there may be advice there saying why a given part is a bad choice for a PIMETA. If you can’t find any information there on the part and you aren’t savvy enough to be able to pick parts on your own, please ask on the forums about it. Often a part that looks like it will work, won’t.

I don’t want to chase down all these parts. Can I buy a kit?

Sorry, no one’s offering kits right now, and I have no plans to ever offer kits. You can get everything else you need with a single order to one of the major electronic parts distributors.

Is there someone who will build the amplifier for me?

If you’ve looked through the docs and have concluded that you’d really rather not build the amp yourself, you can look for a builder on the forums. There are several active builders. I am no longer one of them.

Can I use the PIMETA as a preamp?

The PIMETA was designed with headphones in mind. Headphones are completely passive, with no connection to the input side of the amplifier, so we are able to split the ground circuit into two parts, to good effect.

If you were to use a stock PIMETA as a preamp, the cabling situation in typical source-preamp-amp configurations shorts out the ground channel. At minimum, this will defeat the ground channel, making it a waste of good parts. More likely, it will cause the circuit to misbehave, potentially even to the point that it damages itself or something downstream.

It’s possible to modify the PIMETA so it will work correctly in a preamp role. The simplest way is to leave out the ground channel entirely, power the amp with a dual-voltage supply, and connect the ground leg of the supply to IG and OG. Alternately, you can use the current design as a starting point, creating your own circuit. See my article Virtual Ground Circuits for some circuit ideas. It’s possible to use a virtual ground ciruit in an active preamp, but it can’t be split into two parts, as in the PIMETA. Something more like the META42 would be more suitable.

I have a question. Who do I ask?

First, look through this documentation. It has been improved continuously since the introduction of the PIMETA, so the answer is often here if you look carefully enough.

Next, look through my articles list. I’ve written quite a few of these articles now, one of which may answer your question. Naturally I don’t wish to repeat myself here in the PIMETA documentation, and sometimes I don’t point to a suitable article when I should.

If you can’t find it here, do a search in the Head-Fi DIY forum archives. Asking a question that’s been answered before (sometimes many times before) is a waste of the other forum members’ time and yours. If the answer is in the archives, it’s quicker to search the archives than to post the question and wait for people to answer.

If the answer is not in the archives, go ahead and post the question to the forum. It’s better to post publically than ask people via email or private messaging because you get more answers by posting publically, and the answers are archived for future builders to find.

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