The PPA is not a good choice for your first DIY amp project. You may
succeed without any problems, but if it doesn't work at first, you'll
be totally lost. The parts for a PPA are expensive enough that you'll
want to be reasonably confident that you can troubleshoot the amp if it
doesn't work when you turn it on for the first time.
The more you read, the more likely you'll build the amp correctly
the first time.
If you don't want to think about part values, just use the ones given
in the schematic. These values will work for most purposes, but they may
not be the best for your particular purpose. There is no substitute for
knowledge and experience.
There are many "optional" parts. How do I know if I need them?
These correspond to optional features. Some of these features are
just nice to have, and others provide functionality that you may or
may not need. If you leave out all of the optional parts, the circuit
should still function, but it won't work as well as the board design
allows. Read the documentation carefully to see why each feature exists
before you decide whether to leave it out or not.
What's the best way to save money on parts?
Use only one buffer per channel, moderately-priced op-amps, and a
cheap enclosure.
If that doesn't save enough money, leave out optional parts.
Beyond that, be careful about choosing cheaper parts than the ones
recommended in the documentation. If you can't get the cost of the amp
down far enough, it would probably be better to go with a different amp
design that's inherently less costly than to use inferior parts for
this high-end amp. Consider the PIMETA,
for instance, a simpler PPA-like amp.
Can I use parts not mentioned in your parts list?
There are so many parts that will work that the parts list couldn't
possibly list them all; it's really just a list of examples. If you're an
experienced amp builder, you can probably choose suitable parts without
even consulting the parts list.
If you're not so experienced, you may want to do some searching in
the DIY archives on Headwize and Head-Fi. Someone else may have used the
part you're looking at and reported on it, or there may be advice there
saying why a given part is a bad choice for a PPA. If you can't find any
information there, 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. I sell the hard-to-find parts along with the circuit
boards. You may be able to get away with just one order to one of the
major electronic parts distributors for the rest of the parts, but you
will often need to make a few separate orders to get the best balance
of parts. If for some reason you do not have access to a major parts
distributor, you may be able to ask for someone to send you some parts;
please don't ask me, though, because I'm already offering everything I
wish to on my ordering page.
Are there people who can 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.
Can I use the PPA as a preamp?
The PPA 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 PPA as a preamp, the cabling situation in
typical source-preamp-amp configurations shorts out the ground channel. At
best, this defeats it, making it a waste of parts. But worse, it can
actually make the ground channel unstable, which is never good.
If you really wanted to do this, you could do any of several
modifications to the circuit:
- You could leave out the TLE2426es and ground channel parts,
power the amp with a dual-voltage supply, and connect the ground
leg of the supply to IG and OG.
- Design your own PPA-like circuit with only one TLE2426
connected to the input of the ground channel, and with all ground
connections run to what is OG now. The result would be much like
the META42, but with a better power
supply arrangement.
- Use one of the simpler amps on this site. The
CMoy, MINT and
META42 will all work as preamps without
modification.
I have a question. Who do I ask?
First, look through this documentation. I update it frequently,
adding new information as I discover things that it doesn't cover which
it should, 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 PPA
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
Headwize and 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. 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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blank. :)