Yeah. I bought one a few years ago when the OPA1622 first came out and immediately saw it as an excellent DIY platform. I hope Mouser/TI can keep up with demand for the eval boards. 
Also, with the small form factor, I bet there's a small Hammond aluminum chassis that'll fit. I'll draw up a drill template for folks to use for the front panel.
Tom
Also, with the small form factor, I bet there's a small Hammond aluminum chassis that'll fit. I'll draw up a drill template for folks to use for the front panel.
Tom
If there are suitable areas you could drill holes. I was also thinking about butchering a Hammond box with PC board card adaptors and mount this inside another chassis. The volume pot, headphone socket and RCA connectors could be wired instead of on board.
ABS Plastic Multipurpose Enclosures w/ Card Guides (1591 Series) - Hammond Mfg.
ABS Plastic Multipurpose Enclosures w/ Card Guides (1591 Series) - Hammond Mfg.
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It should be able to do more anyways. The linear audio website (The SilentSwitcher | Linear Audio NL under "supplying the supply") says the following:
Edit: Sorry Tom for the off-topic in your vensor's thread.
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If you chose FedEx or UPS for the shipping method and you live in the US or Canada, it'll most likely arrive before Christmas. If you chose Canada Post, delivery will likely be in the new year (probably mid-January).
If you need to upgrade your chosen shipping method, contact me by email and I'll get you going. FedEx/UPS shipping shouldn't set you back more than ~$20 (Canada), ~$25 (US), ~$30 (EU).
I won't have the boards on hand until the 21st (assuming UPS delivers overnight as they're supposed to). Unfortunately, I can't ship until I have the boards.
The board is 2.15 inches wide. I doubt it fits anything, but you may get lucky. My intent was for you to mount the board by the volume pot. To minimize the stresses associated with plugging/unplugging the headphones, I'd use some contact cement to glue the rubber feet of the OPA1622EVM to the bottom of the chassis.
Tom
Yep. That should work. You may have to put the power supply and the HP-22 side-by-side, which would push the volume control off-centre, but there is enough room in the box for everything as far as I can tell.
One option for those who won't need or want the 3.5 mm output is to cut off the part of the connector that extends past the edge of the EVM. This would allow you to mount the HP-22 by the nut on the volume pot. Then solder wires to the EVM output for the off-board output connector.
I may buy one of those boxes and provide drill templates for it. That'd be neat.
Tom
Can it accept AC power or just DC?
I see Mouser has an AC-AC power brick for around 10 dollars which can make powering it with a split supply easily.
Is there any modifications that can be done to run off a single DC power supply without hindering performance too much?
Awesome work as always,
Kaden
I see Mouser has an AC-AC power brick for around 10 dollars which can make powering it with a split supply easily.
Is there any modifications that can be done to run off a single DC power supply without hindering performance too much?
Awesome work as always,
Kaden
Attachments
It needs a split/bipolar (+/-) DC supply. I recommend ±7 – ±15 V. ±12 V seems to be a good spot if you're using an external supply.
Yeah. That plus a voltage doubler would get you there. Maybe add a pair of LM317/337 or LM7812/LM7912 for regulation.
You'd have to hack both the TI EVM and the HP-22 board to make it run on a single supply. I'd rather not go there. You also get a significant pop in the headphones on startup with a single supply. That output cap has to charge somehow...
Tom
Hello Members
I am new to this forum. I just bought the HP-22 from Tom.
For the start I plan to use 2 x 3 18650 batteries to power this and Tom confirmed already that will work fine.
Maybe I will replace this later with a power supply. Tom writes on his HP-22 website "The HP-22 is intended for use with the Neurochrome Preamp Power Supply, but can be powered by any power supply in the range of ±7 – ±17 V. It can even be powered by a pair of 9 V batteries in a portable headphone amp."
The recommended Neurochrome Preamp Power Supply cost 159 USD which is obviously a lot for a headphone amp with parts for 50USD.
Now I am wondering how good a such a power supply has to be. Will any ripple on the power supply be audible in the headphones? Is there a circuit on the HP-22 board to smooth the input voltage? Does the power supply has to be "perfect" to be sure the sound of the HP-22 is as good as it can be? How to select one?
Thanks
Edgar
I am new to this forum. I just bought the HP-22 from Tom.
For the start I plan to use 2 x 3 18650 batteries to power this and Tom confirmed already that will work fine.
Maybe I will replace this later with a power supply. Tom writes on his HP-22 website "The HP-22 is intended for use with the Neurochrome Preamp Power Supply, but can be powered by any power supply in the range of ±7 – ±17 V. It can even be powered by a pair of 9 V batteries in a portable headphone amp."
The recommended Neurochrome Preamp Power Supply cost 159 USD which is obviously a lot for a headphone amp with parts for 50USD.
Now I am wondering how good a such a power supply has to be. Will any ripple on the power supply be audible in the headphones? Is there a circuit on the HP-22 board to smooth the input voltage? Does the power supply has to be "perfect" to be sure the sound of the HP-22 is as good as it can be? How to select one?
Thanks
Edgar
Your batteries will be fine.
The HP-22 does not contain any regulator on the power supply, so the supply does need to be reasonably quiet. But the power supply rejection of the OPA1622 and LME49720 is substantial, so you do have quite a bit of wiggle room there.
Maybe I need to go through the wording on my website. The Preamp Power Supply was designed for use with preamps and headphone amps, such as the HP-22. The Preamp Power Supply is a good match for the HP-22, but other supplies will work well as well, including your batteries.
Tom
The HP-22 does not contain any regulator on the power supply, so the supply does need to be reasonably quiet. But the power supply rejection of the OPA1622 and LME49720 is substantial, so you do have quite a bit of wiggle room there.
Maybe I need to go through the wording on my website. The Preamp Power Supply was designed for use with preamps and headphone amps, such as the HP-22. The Preamp Power Supply is a good match for the HP-22, but other supplies will work well as well, including your batteries.
Tom