AMB Laboratories DIY Audio

[Yangorang]

So I'm trying to make a 15V linear regulated power supply for the Audinst HUD-MX1 audio amplifier that would be capable of driving fairly high powered headphones.
Does anyone have a ballpark estimate of how much current the Audinst would draw under load? How many va's would I need on my transformer?

I'm looking at the BV301D15027 from Zettler Magnetics which can drive 180mA and want to make sure that it would be enough for this application.

Thanks,

--Yang

[amb]

For what headphone amp? If you're referring to just the Audinst HUD-MX1 (USB DAC with headphone amp), its factory adapter is rated 15V 0.5A-1A, which means 15V * 1A = 15W. Giving yourself some headroom for transformer losses, I would recommend at least a 20VA transformer. The transformer you're looking at is only 2.7VA. Way too small.

[MisterX]

Insert an amp meter between the OEM PSU and the device.....What's the current draw of the device when it's "driving" your "fairly high powered headphones"?
It's actually a very easy "problem" to solve with a little DIY effort.

[Yangorang]

Insert an amp meter between the OEM PSU and the device.....What's the current draw of the device when it's "driving" your "fairly high powered headphones"?
It's actually a very easy "problem" to solve with a little DIY effort.

I actually don't really see any easy way of doing this besides cutting the + lead on the adapter cable and inserting my multi-meter there. I could solder it back together easily afterwards but I don't really want to cut it in the first place.
The other issue is that I don't really have the fairly high powered headphones that I want to be able to power as of yet - the idea is that I want to be futureproof - I guess I could ballpark it though with my current headphones.

For what headphone amp? If you're referring to just the Audinst HUD-MX1 (USB DAC with headphone amp), its factory adapter is rated 15V 0.5A-1A, which means 15V * 1A = 15W. Giving yourself some headroom for transformer losses, I would recommend at least a 20VA transformer. The transformer you're looking at is only 2.7VA. Way too small.

Yea figures I guess...EL30 transformers were only meant for low power applications anyway...
I'm leaning more along the lines of getting something like this now: https://system.netsuite.com/core/media/ ... 5&_xt=.pdf
Using a wall transformer like that I'd be able to locate it further from the actual power supply to minimize interference and save myself some space as well - the 1A rated wall transformers are quite gargantuan though really so I've been wondering if the Audinst HUD-MX1 can really possibly draw a whole amp at peak. If possible I'd like to get away with something smaller like their Triad Magnetics' 400mA rated product.
I've asked Audinst about this as well but haven't received a reply yet - hopefully they'll know something about the real-world power draw of their product.

Thanks for your responses guys.

[dsolodov]

Is 5VA 2x9VAC transformer sufficient to power the 3.2W load at 7.5VDC? I calculated the core load to consume 0.295A and another 0.95A in power losses on the voltage regulator. The numbers are without 'safety' buffer.

[amb]

What 3.2W load are we talking about? Does it have a high start-up peak current draw?

[dsolodov]

What 3.2W load are we talking about? Does it have a high start-up peak current draw?

The load has

• Atmel 328 Chip with 5V LDO
• low current LCD
• WM 8804 with two 3.3V LDOs (each LDO can deliver up to 150mA)
• 2 other supporting chips with ~20ma draw each.

So I assumed:

• LCD - 0.045A (as per datasheet)
• Arduino - 0.15A (it does not drive anything from pins, 50mA is typical arduino draw)
• WM8804 and other chips - 0.1A (datasheet shows 0.0167A at 3.3V for WM8804 plus some current for all other ICs)

The total adds to 0.295A or 2.2125W. Plus 0.95W dissipation on PSU's LDO for the total of 3.2W.

[amb]

If there are no other current consumers on the supply, then 5VA should be quite enough.