[Afux]

I have a portable amp that was gifted to me back in '08 from a [H]ardForum user who I've forgotten (lost account info). I was deployed at the time (now as well) and it must have hit a soft spot as I didn't pay a dime. I was told its a MisterX amp, unfortunately I don't know much else about it. I've cracked it open and taken the attached photos for reference. It's been a faithful companion through multiple headsets and IEMs of varying quality.

Now for the help; I'd like to know what type of wall-wart to use as well as what type of 9v (NiCd, Alkaline, NiMH, ect) to pair it with for trickle charging. I have an AC adapter that fits the plug and is rated for 12v 3a DC output but I don't want to test it in case I let the magic smoke out. What can y'all smart folks tell me about my beat up loud-box?

 

[buke9]

This should be the wallwart needed.
https://www.jameco.com/webapp/wcs/s...01&catalogId=10001&pa=189982&productId=189982
I believe this is the new version of the ampqnd where I found the wallwart.
https://www.amb.org/audio/mini3/.
There was a old post here that said you have to have 15volts to charge for he battery.

 

[Afux]

Thanks for the wallwart info; what kind of battery is the charger circuit compatible with--the Mini3 says NiMh? I'll also have to reference the Mini3's spec sheet for European/Asian power as the Jameco wallwart is 120v.
Does the wallwart just charge the battery or can It power the amp as well? I know some circuits don't support pass-through. Currently deployed and getting batteries can be a pain.

My google-fu also turned up the Mini3 as well as the successor to my device but I wasn't sure. Can anyone confirm what type of amp I have and if it is a MisterX design? I see "CMOY" and "Pimeta" and "XP" thrown around on forums but I haven't dug into the research of what all that means yet.

 

[buke9]

Don’t know much about the amp so can’t say if it powers the amp or just charges the battery. The CMOY is another diy 9v battery powered headphone amp that uses a Altoids tin as the case for it.

 

[tomb]

No offense to buke9, because he is always very helpful. However, that is NOT a Mini3. I've built two Mini3 amplifiers and the only similarity with that one is the basic size. (Actually, the Mini3 is smaller.)

What you are looking at appears to be a buffered CMoy. The primary opamp is the AD823, while the buffers are the BUF634 (Burr-Brown buffers used in the PIMETA, Millett Hybrid, and many other earlier headphone designs).

CMoys are built to use either 9 or 18V (one 9V or two 9V batteries). However, if the power supply is a walwart, your limiting factor is the opamp and the capacitors. Looks like the AD823 can take 36V. Check the rating on the label of the electrolytic capacitors - that will tell you the voltage rating. (The camera angle doesn't show the capacitor ratings.). If those caps are rated at 35V or higher, a 24VDC walwart could be used. Ideally, you'd want to use a linear-regulated 24VDC walwart. You can find those at Jameco.

Better yet, visit AMB Labs or AMB's forum on the web. You will find MisterX contact info, there. You can send him a PM on Head-Fi, but I haven't seen him post here for many years.

Edit: I don't see any batteries. Perhaps more importantly, I don't see any charging circuit, either.

Edit2: Looks like a TO-92 device right behind the volume pot. That might be part of a simple charging circuit, but it may also be a TLE2426, which was often used to provide a split rail supply in more sophisticated CMoys. Best to talk to MisterX, if you can.