That is right about the chip current source/sink and the same sort of situation exists for the O2 booster board.  The 70mA figure is continuous - assuming the DIP8 package heat dissipation limits are not exceeded - while the 100mA is for short periods.  But that is how music works out anyway...

ZenocideZ:  For more of an apples-to-apples setup to the ODAC + O2 you would need the UD-H01 dac + HA-501 headamp, which goes for $650.  That brings the Teac stuff up to $900.   The headamp output on the UD-H01 wouldn't have the current drive capability of the O2 or the HA-501 from the way they...

  Along with double the otuput current, the no-thump headhone relay, and the indicator LEDs the other truely hard-and-fast benefit is the ability to run the O2 at +/-15Vdc for the rare 600 ohm low-sensitivity headphone where the O2's standard +/-12Vdc power supply won't produce enough volume. ...

  Yeah that is the problem.  With the O2's 7Vdc peak swing on batteries you would need 7v / 33R = 212mA per channel.  The O2 can only handle around 120mA per channel with the standard NJM4556A chips.   Headphones like that are one of the reasons why I designed the O2 booster board.  The...

  That one looks like a winner.    Like macandmar says just set it on 15Vac and away you go.   The 5mm x 2.1mm tip should fit the O2.   The wattage rating is a little odd.  The specs say 9.6 watts which they've rounded up to 10W in the title.  At 1 amp and a power factor of 1 that would give...

It is the sensitivity, which is the other thing along with impedance that figures into how hard a set of headphones is to drive.   The current AKG701's have a sensitivity of 105dB/V from AKG's specification sheet.  That means with 1V(rms) into the headphones you will get a sound pressure level...

Here is some potential good news for folks with the low battery problem.   The O2 booster board is a T shape, but the PC board fabrication house does 5cm by 10cm of area whether it is used or not.  Looks like I can fit a couple of those O2 latch circuit boards in the unused space around the...

  The problem is a bit of a design hiccup with the O2.  The batteries tend to rise up in voltage a little bit once the load is cut off (when the battery is low and the O2's mosfets turn off).   If they rise up too much in voltage the O2's power management circuit thinks the batteries are...

  Lol!  Hey I like how your panel turned out.    This thread had kind of died off it seems, so a kick in the pants probably hasn't hurt.  Since the last booster board from this run went out the door though I am going to essentially shut up in this thread and post any new stuff in the DIY forum...

  The bill of materials for the O2 booster boards adds up to around $56 at Mouser, including the LEDs, but minus shipping costs.  The at-cost price on the PCB was $8 on this last run ( I had 10 made and was charged $80 at Seeed Studio, including shipping).  I will probably do another board run...

  Good thoughts!  I've actually already had that discussion with John (JDS) in another forum regarding my version of an O2 Desktop Amplifier DIY project.  His position at that time was that he feels blocked in performing a test by the O2 designer's license terms of "no derivitives", which is...

I wanted to follow-up on what I posted earlier in the slew rate discussion about possibly being able to fit a LME49990 dual-SMD to DIP adaptor in place of the O2's NJM2068 gain chip to raise the end-to-end slew rate all the way up to 20V/uS.  Well turns out the adaptor does fit and work just...

  You might want to try actually going in the other direction and *adding* some series resistance and then see how that sounds.  I'm not entirely convinced that near-zero ohms output impedance yeilds the best results for some heapdhones, even though I know the O2's designer cited this paper...

  Hi Alex!  This is good news, since you know what they say about medical doctors - "first do no harm".    Alex and the other builders know I've stayed away from making any comments on how I think the booster board sounds or making any sound claims.  That is all your guy's jobs!    There are a...

  Hey good question!  I have not copyrighted the O2 booster board in the spirit of the O2 designer's goals with the O2 amp.  The Gerber files to make PC boards are posted at the Google Drive link in that DIY thread (use the V3.0 which includes the headphone relay).  Anybody can make boards...

You will be missed, Fred!   Your technical insights have been some of the best.

Hey thanks to all the builders for the O2 booster board listening reports!  

Yep, he managed to get himself banned. If you find it do a search for "slew" and "slew rate" in the topics around July and August of 2011.  There is more than one chunk of stuff.

The booster board will also increase the O2's slew rate.    I added some information about that to the build instructions at the Google Drive link yesterday after the good discussion in this thread made me realize that was another benefit of the board I had forgotten about.   The O2's orginal...

  Yep Alex is right, do send me a PM if interested.  I have two at-cost boards left from the current V3.0 fabrication run and parts kits.  Back when I started this thread the mods gave me an OK to sell individual boards to help out with that DIY fab minimum order cost issue, as long as...

  The O2 booster PC board that I cooked up may help with that if the headphones involved are especially current hungry (low impedance + low sensitivity).   I just posted a V3.0 update that also adds a headphone output relay to the O2 to help mitigate some of the O2's turn-on and turn-off...

Here is a follow-up to this "O2 booster board" project for the O2 headphone amplifier, two months later.   Where I last left it above I was going to try upside down DIP-8 sockets with the dual-pluggable connection pins that MisterX suggested, to connect the booster to the U3 and U4 sockets in...

Well I've had an idea.     It looks like I can mount a set of DIP8 sockets upside down, under the O2 output booster board's tab, to sit directly above the U3 and U4 sockets on the O2 headamp.  Best I can tell with the caliper that should leave pretty close to the 0.210" between the contacts of...

  Hey thank you for the pointer, MisterX!  I had completely missed that "342" series.  All the SIP headers I've found so far were the standard size pin that would be too large and damage the contacts on a DIP socket.  I also didn't know about that Digikey value add service!  I've done most of...

Hey thanks Alex!  I've had a lot of fun messing around with the O2 headamp via various mods and now these boards.    Kind of a small miracle that the LME49600 (DPAK package) just happens to fit between a PC board in that B2-080 case top slot and the case top.    It seemed like just everything...