For the DIY headphone enthusiast we have made our Zen Head available as a kit (less the fancy machined chassis) at a substantial savings!!!



https://www.decware.com/newsite/diy.html

Steve,

The link is no working.

John,

How did the kit turn out?  I just ordered one the other day.

Did you ever try the Li ion batteries?  I don't know how well suited to audio Li ion batteries are as I've never tried them.  Thinking SLA and a good regulator myself.

Anybody know what the mAH rating of a typical 9v battery is?  I've got a couple of new 1.3 AH SLAs here that I'd like to put to use.  Obviously this will not be a pocket amp .

-- Jim

Pictures soon, charging camera.  

With the board completed over the weekend, I scrounged the house for a 9V battery.  No luck.  I briefly considered raiding my DVM, but resigned myself to walking to the store in the snowstorm for a battery.  

I had checked the build every step of the way.   I double checked the polarity of all caps, and checked that the little IC insects wre installed facing the right way.  The board in marked, but I checked the image of Steve's build as well.  I also had to look to see which jack was input.  I decided to add a dab of hot glue under the big cap to keep it from moving, and also where the battery wires attach to the board as strain relief.

I bought 2 cheap mini jacks, and soldered up a patch cord using some cat5 wire I braided.  I plugged everything together and clicked it on.  With the source off, the slightest background noise at full volume.  

I lowered the gain, and hit play.  Whew, it works!   I lowered the source, and turned the gain up on the board, trying to find a sweetspot.  I quickly decided my headphones sounded better with the impedance set to 32K.  Gain set to normal.  I have the crossfeed on now for the novelty of it, still haven't decided if I like it better on or off.    Still trying to decide what the 'compatability' switch does, but it sounds more open in position B.  

As far as how it sounds, its quite suprising.  Its a transformation.   It reminds me of listening on my big rig.  The amp brings forth a level of detail that I thought my portable was incapable of.  I have the source(Google G1 phone) down, and the amp up.  Bass has a tighter more natural balance than before.  The highs are neither rolled off, or in your face.  There is enough power now that I can't turn it all the way up.  

I'm still drawing up my chassis, but I'm tempted to tape 2 sheets of cardboard over it so I can field test it on tomorrows commute.

The completed board.



Amp, G1 source, solder station, Koss Portapro, and Senn woodies.  

John C.  

Hello Steve,

I now use my Senn HD600's for 99% of my listening. I used to use my SE84 amp ( to great effect except for the hum issue I had, see my post in the ERR section for details on that ), and I'm now using my NAD 3020A since the SET is in pieces. But it's a little too bright for me.

So I decided I need a dedicated headphone amp, and everything I've read about your little gem convinced me that I need it. I've just got to decide whether I want the full kit or just the circuit board. I'll figure that out in a couple of weeks and give Devon a call to order. Which brings my inquisitive mind to the following.

This will not be a portable unit, so I am not constrained to the single 9v battery PS. I still think Iwant to use a battery supply, but I have two questions regarding the implementation.

IF I have to use 9v, I plan on stacking six 1.5v D cells in series to get the required 9v, and obviously tying the ground between batteries 3/4 to get the +- 4.5 volts you use. Is there any benefit to keeping the cap banks after the battery, or should I cut the circuit board traces and apply the +- 4.5 v directly from the batteries w/o caps ?

Second, since I'm not going portable w/ this, I'm not tied to the +- 4.5v supply. I'm not at all familiar w/ opamp circuits, and yours in particular, so unless you tell me I'll blow something up, I'd like to go up to a +- 12v supply and listen. Hopefully there's no technical reason that would not work. It would be fun to play around and listen.

Third, is a battery PS the cat's meow for circuits like this, or would a  diode based highly regulated +- PS be the ticket ?

Thanks for all of your help, and of course for putting this in kit form so nuts like me can play around.

Cheers,              Crazy Bill

Hello Bill,
You may want to consider one of these 9V battery eliminators. It was actually suggested to me by Steve, durring one of our conversations about the Zen Head power options if not going to be portable; but still have the portable option available if ever desired in the future ...  Regards, ddemy

http://www.qcavionix.com/be-9ac.php?cat=20504