[JHouser]

Nice thinking to wire the pot up. Saves a ton of room! I opted to go for a longer case but 18V. I put the boards lenghwize.

 

[intlplby]

i got my completely stock mint in the tiniest hammond while stile keeping the potentiometer pcb-mounted.

i'll upload pics later

unfortunately the pot is bad on it and i need to get a new one...(it works fine until you hit around 85-90% volume and then the amp cuts out and gets staticy and you need to turn it off and back on to get it back to normal again.)

 

[Syzygies]

This definitely depends on the battery, the "standard" thickness doesn't fit:

If it doesn't fit I'll swap caps, add a battery, and move it to an Altoids tin; I've always wanted the volume control sticking out of my pocket, not sideways like the cut original.

Did I miss the thread where someone says you don't have to cut the MINT board for a 2x9V Altoids amp?

(I've been getting great PM counseling from fellow forum members on my unwillingness to cut a MINT board, what it might mean from my childhood, ...

)

 

[n_maher]

Quote:

Originally Posted by intlplby i got my completely stock mint in the tiniest hammond while stile keeping the potentiometer pcb-mounted. i'll upload pics later unfortunately the pot is bad on it and i need to get a new one...(it works fine until you hit around 85-90% volume and then the amp cuts out and gets staticy and you need to turn it off and back on to get it back to normal again.)

Sounds to me like the opamp is clipping not that you've got a problem with the pot. How in the heck are you needing to run the thing at 80-90% volume? I rarely get mine over maybe 20-30%.

What are you using for a source, headphones, amp gain setting, etc.?

Nate

 

[Syzygies]

I bought a few iPOWER "9V" 250 mAH INSTANT BURST NiMH Rechargeable Batteries, after research suggested they're on the thin side. I took off their shrink wrap, as suggested in the Lansing DN1 thread. They look much more appealing without the shrink wrap (one can see the individual cells through the plastic, and I'm tempted to keep going, and construct a larger battery from their parts).

This leaves plenty of room in a Hammond C8 case:

 

[individual6891]

Quote:

Originally Posted by Syzygies I bought a few iPOWER "9V" 250 mAH INSTANT BURST NiMH Rechargeable Batteries, after research suggested they're on the thin side. I took off their shrink wrap, as suggested in the Lansing DN1 thread. They look much more appealing without the shrink wrap (one can see the individual cells through the plastic, and I'm tempted to keep going, and construct a larger battery from their parts). This leaves plenty of room in a Hammond C8 case:

Looks promising

 

[Syzygies]

Ok, this happened by accident. One of the aforementioned batteries was toast, it only yielded 9V under slight pressure, clearly some kind of connection problem. Thomas Distributing offered instantly to send me a replacement, said to do what I wanted with the faulty battery.

Had to take it apart, futzed with it during a phone call, ended up with this:

Slides in like a dream. In retrospect, much easier than any of the other contortions people go through for this case.

So now I have room to stack on a second half-MINT, wired as a dual buffer ground channel. Anyone have any guesses what the quiescent current draw would be?

Also, these 9V snap connectors have to go, they take up way too much volume for their purpose. Anyone have direct experience with a subminiature alternative they can recommend, like one sees on phone batteries, etc?

 

[Syzygies]

Of course, something has to give, for these cases. If what gives is a standard battery, in favor of a custom battery pack like the above butchered 9V, then the solution is clear: Solder eight tabbed AAA cells into a custom battery pack to fit around the MINT board. There's room, even with a charging jack in back and a second half-MINT ground channel. This way, there'd also be the needed juice.

Edit, I see how to do this with 6 AAA cells, not 8. With NiMH, enough for the MINT.

 

[individual6891]

Use something like this for the connector.

That disassembly of a PP3 looks quite intriguiging, though I really can't afford to do it myself

... they cost £5 each!

I'm working on a second version of my mint with the board arranged slightly differently, *updates soon*

 

[Syzygies]

Quote:

Originally Posted by individual6891 Use something like this for the connector.

I used Molex for my J12 Pimeta, and took them out. First, they're meant for a board, not a mid-air connection. Even on a board, the matching wire terminator was practically the height of the J12, a huge, clumsy waste of space.

 

[individual6891]

Revision 2 - OPA2132

After Revision 1 based on the AD8620, I felt something was lacking. The AD8620 really is a very bright chip. I was missing my drums on The Prodigy, and bass guitars on Snowpatrol, and saxes and piano's sounded a bit too sparkly with Katie Melua.

So I decided to go for another revision..

Configuration:
OPA2132 dual opamp chip @ 2.0mA bias instead of 1.5mA bias with AD8620
2x BUF634 buffers
2x Panasonic FC 220uF capacitance
0.1uF Wima MK4 input caps instead of 0.22uF
8.4V NiMH (10.5V charged)

Instead of heatshrinking the mint, this time I wrapped it with glassfibre reinforced tape (used commonly in RC10 model race cars). This allowed the halved board section to have a LOT more room in the case. The tape has excellent insulation, and is insanely strong.

Another change is that the board is now the other way round (more easily explained using the pictures below). The resistor/IC side is now against the battery, instead of against the side of the case as in revision 1. Why? Allows the potentiometer links to be parallel with the actual potentiometer, and wiring is a lot easier. Plus the output leads are on the right side, and saves about 0.5mm space

Also added some squishy foam to allow the battery to be more secure in it's compartment.

So, most importantly, how does it sound? Absolutely bloody fantastic

... I have my bass back! Everything seems a lot more smooth. Jazz sounds better with it, but rock sounds slightly smudged with the opamp having a warm characteristic instead possessing AD8620-type bounciness. Still, this is a lot more preferable and easy to listen to than having the amp lack base. What about battery life? Well the OPA2132 documented to clip at a higher voltage, but with NiMH's this really doesn't matter, battery life is on par with the AD8620 MINT.

Pics:

Ill be making some proper front panels with FPD in the future, so watch this space

 

[individual6891]

Also, the Wima input caps are mounted at 45 instead of directly vertical to save a LOT of space, about 2-3mm maybe and it allows the battery to sit a lot better with a bit of room to breathe to spare.

 

[__redruM]

Here's my 95mm hammond mint layed out:

I just dropped a internal charger for a NiMh 9V Battery.

Basically I wanted to be able to charge and listen at the same time. See link for details:
http://www6.head-fi.org/forums/showthread.php?t=110663

 

[individual6891]

That's not a bad idea, cutting down a 120 to size..

Still, it's quite hard fitting a DC jack into the 80 case.. The problem isn't the LM317, that can fit, but the DC input jack takes up a lotta precious space..