Soliciting recomendations for DIY HP amp build.

What level of documentation are you really looking for? Step by step or just a very complete set of information?

Certainly, any of the AMB designs are well documented as are the Millet miniMax kits Beezar offers. The Cavalli designs are probably next in terms of documentation. Support, at least on this forum, is excellent for any of those choices.

I would start by looking at the level of documentation available on the AMB and Beezar products and decide if that is enough for you to feel confident you can complete the build.

 

+1 for AMB, Ti is very helpful and very active on these forums and the forums he hosts on his site for each project.

 

I started with about the same budget as you and my first project was the CK2III, which is collaboration between AMB and Cavalli.

 

http://www.amb.org/audio/

 

 

Actually i think they are all pretty active on these forums supporting their projects, so hard to go wrong.

 

 

Builds with a PCB and through hole components I think are pretty easy to put together.  You really just need to focus on orientation and drop in each part and away you go. 

 

For amps:

m3 is good in this range, but I thought it was $200+ with a power supply. 

 

I've had my eye on the EHHA for a second build... might be a little big for a bedside build (typical case is 12x12x3) and I haven't priced it out yet, so may be a budget buster as well.   The rev A version looks pretty straight forward and gets good reviews.   My wife can barely stand the little CK2III case I keep in the living room, so my first task is finding a place to put the EHHA without stirring up trouble...

 

The compact tube hybrid might be a good candidate for a bedside hybrid tube amp.  Its got a compact layout though, so may be a more difficult build as a result.

 

SOHA II I thought was in this price range, but I can't access the site from work to see if it is the one i am thinking of.

http://www.cavalliaudio.com/

 

Millet has a few options in the price range, though you might spend the extra to get the pre-cut case bumping you out of the price range.  http://www.diyforums.org/

 

Unless you are good at woodworking to make custom case parts or enjoy case work... whatever you pick I would recommend spending the extra on prefab case work if its available.   I think it took me longer to do the case work than to solder my amp.  Also consider spending a little extra on the nicer input/output connectors etc.  I went nice on the front and middle of the road on back and wish i had just done all nice ones ;)

I would recommend the CK2III, as noted.  It will be cheaper than you are budgeting, but it is a *very* nice amp.  Decent power for what it is.  It is enough for most headphones, at reasonable levels of listening levels.  Low Z headphones will not be a problem, but high Z may present an issue at higher ear splitting levels....in which case you can build it out to +- 24V and 60mA bias with real heatsinks, not the clip on ones.  There are some slight changes (and fabrication) to make for that, but it can be done.  I need to re-case mine and redo the power section to support this, when I have time.  It was my first DIY after a CMoy.

 

You can also build the Dynalo, another very solid and very good amp.  Build it with a really good PS (sigma22), a star grounding scheme, and you will effectively have a HeadAmp GS-1, not that that is a secret.  It won't be as nice, of course, without the backplane and the amp modules, but sonically should be very similar.  It will be voltage limited, however, like the CK2III....if it applies to you (most likely not).

I believe CK2III is a top of the line solid state amp on par with M3 and commercial amps.  The next step up in DIY is AMB's Beta22.  You can tweak the sound of the CK2III with different output transistors if that is your thing.   I took a chance on the pairing i selected (2SA1837/2SC4793).  I have nothing to reference it to, but its good to me ;)

 

CK2III is designed to be always on, so you are good there.  It makes some heat, but with heatsinks it can run in a sealed up case without issue.  Biasing is done by trimpots, so other than being tedious (adjust, seal, wait for heat to stabilize, test, adjust, etc) it is easy to get it dialed in to the range AMB recommends (instructions posted on the site). Really not much else to do to get it online.  Power regulation is right on the board so you don't need to make a seperate regulated power supply.   You can put the transformer in the case or in a wallwart/project box on its own.   The gallery on amb site has examples of both.  On my build i used svideo ports/cable as the umbilical to get the dual rails from the transformer in a project box back to the main unit.

 

Looks like you are in the US,  I built it all early this year and all the parts were still easy to source from Mouser and Digikey.

 

I did a pretty standard build and it seems to run my Beyerdynamic DT990 600ohm well enough.  I can't use most of the volume knob with the default gain, so in that regard it has plenty of power.   Didn't know there was a high voltage version/option, but if you also have high impedance cans that would be something to look into.   I built the amp then upgraditis hit to get the cans.  Now looking at trying a tube amp to see how they sound...

 

FWIW, I like EI core transformers for audio.  It is low bandwidth, so it filters out a bunch of mains stuff.  I know many people recommend toroidal transformers, but I go the other way whenever it is feasible to do.  In this case, a separate transformer box.

 

The only other thing to worry about is that you may need a Zobel network on the output.  I did, mine was oscillating on certain headphones.

Gain is not power. ;)  It's just how fast you hit your voltage and current limits.  There is a high voltage version, but it is strictly DIY (do it yourself) and not supported....as with any amp you build, you can do it yourself any way you want to do it and as much as you feel comfortable with.  Experimenting is part of the fun.  You need to cut traces or do other things to power the servo, and change out the regulators to 24V as well as a bigger xformer, and change some resistor values.  60mA bias is great, but needs a real heatsink, as it will get hot.  60mA bias gives you 120mA of class A, and the 48V voltage source should give something around 30-35Vpeak output.  I'm not sure, as I haven't implemented it yet...though sadly I also hardly use my CK2III or Dynalo anymore, as I've been on a hybrid thing.

 

It's a good circuit to tool around with, IMO, and even overkill it with a S22.