Inverting Version Of The NwAvGuy O2 Headphone Amplifier project prices for PC boards and parts

The Inverting O2 Headamp has all through-hole parts for easy soldering, with the exception of the 3 chips (two SOIC-8 and one SOIC-14), two 0805 resistors, and 11 0603 sized capacitors on the back of the board.

Please note: to have 100% through-hole soldering (no surface mount to deal with) you need to get the Inverting O2 Headamp board with the SMD parts pre-soldered, below.

The same comment as in the project above about no parts kits available, for the same reasons. But same as above, if you find a part out of stock at Mouser, I probably do have it (or can give you an alternate part number) and will sell it, just let me know.

PLEASE NOTE: V3.61! These boards are the latest V3.61 that I have posted out on the project Google Drive link. V3.61 just has a few minor cosmetic changes in the silk screen marking from V3.6.

TRIAD NO LONGER MAKES AC-AC TRANSFORMERS. This is a recent thing. Jameco Electronics ( in the US has a full line of AC-AC transformers. Their 16Vac 1A transformer is their part #2227612 for $11.95. The transformer for the Inverting O2 has to be 16Vac, no less or no more. On the top end the reason is the input voltage limit on the LT regualtor chips. If you are outside of the US you will probably have to box up a small torroidal transformer yourself that has 16Vac output (or 2x 8Vac in series).

Shipping is actual cost, which for US destinations (for all except the partially assembled board) is the USPS "first class parcel" rate of $2.60 ($2.45 from the post office + $0.15 for the padded envelope) and does include tracking. The post office says 3-5 business days on average to deliver "first class parcels" (goes by truck), but from my experience expect 5-10 business days.

For the partially assembled  board the shipping to US destinations is via the USPS "priority mail small flat rate box" service which they charge $6.80 for, and includes tracking and postal insurance. The priority mail also gets there pretty reliably in 2 or 3 days (goes by air). The rigid box protects the fully assembled board and the postal insurance covers it in case they loose the package.

For destinations outside the US our post office here unfortunately is rather pricey. Their lowest rate is "first class international", which they say typically takes 10-14 days, for $13.50 ($13.35 + $0.15 for the padded envelope). The customs form number will actually work as tracking, just enter it in at the website tracking page, but the tracking usually stops when the package leaves the US. The "first class international" rate is OK for bare boards, but for assembled amps that are thicker their next step up may be required, depending up the country, which is "priority mail international" for $22.50 up to a certain weight and size. That one does include tracking to some countries. Again these are actual cost, no markup, and should be listed out at Sorry but I have to declare the full value of the invoice on the customs form. Some countries charge (fairly large!) taxes on incoming shipments, so please check into your country's rules to avoid a surprise.

Payment via paypal, please email me for the paypal address. The paypal fee also has to be added to the order, 2.9% of the total + $0.50 for orders in the US, 3.9% + $0.60 for outside of the US. Please make sure you are having paypal transfer the money into US dollars. I only accept paypal, sorry no checks or other payment methods.

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