AMB Laboratories DIY Audio Forums

[goliraja]

Greetings, Everyone!

Presenting β22 - Double Decker (sports bar edition). Before getting into any further details, first of all hats off to Ti for such an excellent design!!! I've not come across such a great headphone amp till date. I won't be able to do justice by describing all features/qualities, would recommend that if you get chance, do listen to this superb amp.

Build details:

• 3-channel active-ground β22 (quiescent current set to 140mA)
• ε22 backplane board (bought during last group buy)
• σ22 regulated power supply (±30VDC output)
• Toroidy SUPREME AUDIO grade transformer TSAS100VA https://sklep.toroidy.pl/en_US/p/TTSAS0100-SUPREME-AUDIO-grade-transformer-TSAS100VA-voltage-to-50V/391
• ALPS Slide Potentiometers Dual Unit (10KΩ) https://www.mouser.com/ProductDetail/688-RSA0K12A1013
• Schurter DD12 IEC with Filter https://www.mouser.com/ProductDetail/693-3-109-957
• Neutrik jack and RCA connectors
• Aavid-Thermalloy heatsink (530002B02500 onboard, 2.5" tall, pin-mount)
• HUTTEN - custom enclosure (another IKEA hack) https://www.ikea.com/us/en/catalog/products/70032451/
• Custom Panel (front, back, side and top) - Acrylic - Tap Plastics https://www.tapplastics.com/

Issues:

• Fluctuating quiescent current. Issue similar to following:
  https://www.amb.org/forum/preliminary-initial-setup-t1552.html
  https://www.amb.org/forum/quiescent-current-fluctuating-t1403.html

Issue was resolved by replacing Q1-Q4 as advised by Ti in above thread. Not sure about the root cause but off board test didn't show any problem with Q1-Q4.

Final build:

DSC_4619.jpg

DSC_4618.jpg

Note: It's advised not to place bottles directly on the top shelf as it blocks the vent, instead use stackable racks (see build log).

More pictures/build log to follow.

Thanks!

[amb]

That is very cool!

[goliraja]

Thanks, Ti!

Additional pictures from the project:

Contents from original packing. Most of the IKEA products use pine wood.

IMG_4331.jpg

You can purchase spray paints (Rust-Oleum) from your local hardware store.

DSC_4522.jpg

The paint will dry in an hour or so. For second coat of paint, it's better to assemble the rack. It's easier to paint as well as see the final outcome.

DSC_4525.jpg

[goliraja]

More pics...

Got L-bracket from Jameco https://www.jameco.com/z/720-00011-Parallax-Mount-Bracket-L-Shaped-Versatile-Slots_2111530.html. You will really need this in order to align slider properly, else there will be issues while mounting front panel acrylic cover. These are mounted under the top rack.

DSC_4529.jpg

While mounting the slider ensure the screws do not touch the front panel. Adjust the L-bracket position before attaching slider.

DSC_4533.jpg

Slider has to be parallel and aligned correctly with respect to rack, else it might touch the corners of the front panel cut-out (see pictures in later posts).

DSC_4561.jpg

[goliraja]

More pics...

Instead of going with multiple cut-outs on a single acrylic sheet, I decided to go with multiple acrylic stripes - it's easier to adjust/align with heatsink position.

DSC_4588.jpg

These additional stripes will keep other three sheets in position.

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Note the placement of cable tie mount and screws for the handle (https://www.ikea.com/us/en/catalog/products/50348786/).

DSC_4592.jpg

Note: All of the above images are from under top rack.

[goliraja]

More pics...

FIXA (https://www.ikea.com/us/en/catalog/products/24155600/) protectors serves multiple purpose - prevents scratch to the base acrylic sheet as well as creates gap(vent) for air flow between acrylic and the rack.

DSC_4535.jpg

Don't over tighten the base plates. Also make sure corners are aligned with the rack.

DSC_4538.jpg

Used Toroidy mounting bracket for the x'former.

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[goliraja]

More pics...

Few snaps of assembled σ22 and β22:

Used all standard components - Panasonic caps, 2.5 in heatsinks.

DSC_4500.jpg

All three boards assembled, ready for initial configuration.

DSC_4499.jpg

Used 18 AWG for power supply and output. To insert the wire easily, trick is not to twist the wire.

DSC_4504.jpg

[goliraja]

More pics...

Attach modules to ε22 and configure them to desired settings.

DSC_4495.jpg

Don't forget to short inputs (jumper) and use parrot clips for multimeter.

DSC_4508.jpg

All modules attached the backplane. It really helps to service the individual boards and cut down the wiring.

DSC_4514.jpg

[goliraja]

More pics...

Select the correct size of standoff (5mm) and heatsink (2 vs. 2.5 inch). If the standoff is too long and you're using 2.5 inch heatsink, there will be very low clearance between the heatsink and the top rack.

DSC_4519.jpg

DSC_4510.jpg

Attach the backplane to the base acrylic plate. For the power supply wire, drill small hole in the acrylic to route the wires to lower rack.

DSC_4544.jpg

[goliraja]

More pics...

Power supply cable routed to backplane board.

DSC_4545.jpg

Attach the top rack.

DSC_4546.jpg

All three racks assembled. Top view.

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