[HD-5000]

Hey guys. I'm planning to build myself a Mint amplifier in a mint tin, but as this is going to be for portable use in a bag, i really cannot have the pot mounted at the side. I also want to mount the pot on the board.

So, the only simple way of pulling this off would be to use just one 9-volt battery, and orient the board so that the pot is sticking out the long end of the tin.

Which opamps work well with 9-V?

What other alternatives do i have?

Any suggestions would be mucho appreciated!

 

[bg4533]

The Mint will work fine with 9V. The OPA2227, OPA2132, AD8620 and others should all work fine.

What headphones will you use with it? Do they have a right angle plug? If so you could put the output on the side.

You might also be able to fit everything on the front if you really squeeze things in. Might look a little odd, but it could work depending on parts selections and cables.

Other alternatives would be to use a different case. Something slightly wider than a Mint tin.

 

[HD-5000]

Thanks!

Yes, it looks like I am going to have to stick to using right angle plugs on the long ends if I want to put the toggle switch beside the pot.

Your suggestion to use another case is noted, but at the moment I feel very very compelled to use a mint tin...

One more thing, if I use one 9-volt what battery life should I expect out of it, using disposable alkalines and AD8620 and OPA2227?

 

[bg4533]

An extra battery in series won't help much with battery life anyway.

Lets say the Mint draws ~20ma of current. That might be a reasonable guess with the buffers at normal bandwidth. With a 160mah 9V you would get 8 hours of battery life if the amp could completely drain the battery. Likely the amp will start clipping before this, so expect less battery life.

 

[llmobll]

if you put the battery in parrallel it will help with battery life.

 

[Emon]

For pot placement, you could always ditch the pot and use one of these or these and hook it up to a digital potentiometer. I think Dallas or NatSemi has (had?) a digipot with a + and a - for hooking to the actual circuit and then two more legs that would increase/decrease resistance every time they went to active high...I'm not sure if it stored resistance in any kind of permanant storage like EEPROM, but for a headphone amp that shouldn't matter too much.

These gadgets aren't quite practical, if they'd even fit...but how cool would it be!

 

[n_maher]

Call me biased

but this is my favorite MINT configuration.

The case is big enough to allow the use of [2] 9v's without have to "halve" the MINT board. It's my current portable rig so I run the 9's in parallel to get more run time before I have to open the case. While the tin cases look cool the simple fact is that they don't last very well. [edit] For what it's worth, I use true 9v NIMH rechargeable batteries for my power supply, but had no issues using 9v alkalines for a time either.

Hope that gives you a slightly different perspective.

Nate

 

[Syzygies]

One needs to distinguish between alkaline and NiMH. The former fades in voltage as it discharges, the latter stays fairly constant. 7*1.25=8.75V is lots if you can count on it throughout the discharge cycle.

Much information, and for that matter, design, assumes alkaline without saying so. The fancy circuitry on the Pimeta to keep constant current to the LED isn't necessary, if the voltage is dependable enough that a resistor is just as good. Pretty much everything one reads on the topic of portable power, one needs to ask "Are they talking about alkaline?".

 

[Pars]

Look thru the amp archives. It is possible to put the batteries in an "L" configuration with the MINT board running lengthwise in a mint tin (I think it was brschmid (sp?) that had some pics posted of one, probably others as well).

 

[individual6891]

Twas me, and the post is here:

http://www6.head-fi.org/forums/showthread.php?t=105435

 

[Pars]

Quote:

Originally Posted by individual6891 Twas me, and the post is here: http://www6.head-fi.org/forums/showthread.php?t=105435

Yeah, that one is cool, but I said in a mint tin, not the smallest hammond. Look at post #8 in the "Post pics of your build" thread at the top.

 

[individual6891]

Ahh, my apologies

 

[Shosta]

I made my mint with one 9v because I had two spares opa134 and was my first try. I think is working fine and a 170mA/h Nimh last more than 20 hours. In my opinion is enough for my PX100s.

 

[bhjazz]

So to run two 9v batteries in parallel (for long play time) I connect:
Battery 1:
V+ battery to V+, V- battery to V-

Battery 2:
V+ battery to M+, M- battery to M-.

Is that correct?

 

[Pars]

No, I think you would do it this way:

Battery 1:
Battery 2:
V+ each battery to V+, V- each battery to V-