[Dougigs]

Your system sounds fiendishly complicated. From what you're describing, you get on the train/plane with 1) your music source 2) whatever power/charging device you carry for your music source 3) your PIMETA 4) your special wallwart for charging your PIMETA 5) your computer and whatever power you carry for your computer

What I'm talking about is reducing this to:

1) Your music source
2) a pocket-sized or PIMETA-sized amp
3) your computer and whatever wallwart you carry for your computer


The computer wart provides the right voltage for charging both your amp and your music source (which probably charges from your USB cable, as most do nowadays). Also, in this scenario, you can charge your IPod (or whatever) off your amp. That's another huge benefit of li-poly technology -- it carries enough juice to charge an IPod a couple times during a typical listening day. (Thus saving us those 9V battery gizmos that top it up).

 

[Dougigs]

Also -- with regard to size, it *is* possible to do li-poly in a MINT case -- easily. You'd get 900mah, not 2400, but that's still almost 4 times the current capacity. I'm just working with a slighly larger case in order to explore the possibilities of 2400 MAH. Once we're past trying out chips, we can work on miniaturizing this. A permanently sealed MINT is a very good idea indeed (whether we're talking about a sturdy case the size of a mint tin, or an actual mint tine)

No, we're not only comparing this technology to 9V NIMH cells. I'm comparing it to any type of cells that can fit in a pocket-sized case. I would be very glad if you could contribute anything in a pocket-sized case that has self-charging functionality.

 

[setmenu]

My portable amp uses an 2/3 aaa 300ma 8cell nimh pack that is simply charged by plugging a suitable charger into a socket,I use an adjustable fast charger originally obtained for charging rc model cells.
It has a 5 level voltage meter built in that informs me of the charge state at the press of a button.
[I did consider lipol at the begining but the chosen pack proved the better fit]

http://www5.head-fi.org/forums/attac...achmentid=4556

There is little room for an inboard charger.

Something I would like to make in the future would be a tiny compact fast charger to plug into this as my current one is, errr ,somewhat bigger than the amp.
I neat little wall wart sized unit that could run on a variety of voltages would be just the ticket.
Perhaps something like this would would offer greatest flexibility as it could be used in conjunction with many amp sizes/types?



.

 

[Dougigs]

Very nice amp, setmenu. Moving the charger into the case could be done, of course, though you might have to lose a pair of electrolytics.

The goal of this discussion is to get a charger and discharge cut-off onto a .75-inch by 2-inch board... Not because any of us necessarily want a mint-tin LiPo, but because the smallest possible charger board should be useful in any number of different amps -- including the possibility of squeezing one into an amp like yours.

 

[mono]

Quote:

Originally Posted by Dougigs Your system sounds fiendishly complicated. From what you're describing, you get on the train/plane with 1) your music source 2) whatever power/charging device you carry for your music source 3) your PIMETA 4) your special wallwart for charging your PIMETA 5) your computer and whatever power you carry for your computer What I'm talking about is reducing this to: 1) Your music source 2) a pocket-sized or PIMETA-sized amp 3) your computer and whatever wallwart you carry for your computer

I am at a complete loss to understand what makes you think reducing the complexity of something is more difficult. You are describing carrying a computer. Fine. If I wanted to do "exactly" what you are trying to do, that would be possible too, but I'm not.

If you want to recharge your amp directly from your laptop or laptop power adapter, then why not just do so? Unlike with Li cells, all you need to do to get a useful charge is limit the current. 20 cent resistor would do it if you want the ultimate in simplicity and low cost. You could recharge your source that way too, "possibly", depending on exactly what it is.

Quote:

The computer wart provides the right voltage for charging both your amp and your music source (which probably charges from your USB cable, as most do nowadays).

I just love it when these crazy sweeping assumptions are made. No, mine doesn't recharge from USB and I have no inclination to buy a new one to gain that feature. Nor do many, it is a bit silly to overgeneralize in so many ways that the end conclusion could hardly be applied to anyone, let alone everyone.

Quote:

Also, in this scenario, you can charge your IPod (or whatever) off your amp. That's another huge benefit of li-poly technology -- it carries enough juice to charge an IPod a couple times during a typical listening day. (Thus saving us those 9V battery gizmos that top it up).

So you want to recharge your amp, then the ipod from that? It's just a further loss during the power transfer, it would seem you are making things as complicated, expensive and time consuming as possible... all so you can justify using Li cells that you may not really need.

You are carrying a notebook which alone, dwarfs any size difference or weight difference of the Li cells even if comparing same capacity. With all this complexity I have to wonder if you will really want to DO what you're describing once you have it all working. Your plan can work fine, but in the end it's not one I, personally, would find desirable.

I suppose we should just leave it at that, we dont' have to have the same power scheme for our gear so long as we're both happy with what we have.

 

[Dougigs]

Mono -- the question is, what do you carry with you on the road? My point was that your battery-powered rig requires more stuff. Battery headphone amps are used for travel by most people. Most people prefer to travel with fewer things.

I'm not meaning to make sweeping assumptions about you, just talking about the things that a typical user will have. Most of us have to have laptops with us. If you work for a living, or attend any kind of educational institution, or like to email or play games or whatnot, then you probably have a laptop in your bag when you travel. Why not take advantage of the resources available?

When I mentioned charging your IPod off your amp, I meant when you don't have your laptop with you. The laptop, in this scenario, is used for charging from AC when you're in your hotel or your room or whatever. But I would find it nice -- and I think a lot of others would -- to have a shirt-pocket sized amp that can also give an extra 6 hours' juice to your IPod, because those things run out of power at the darndest times. The fact is that an awful lot of us carry little boxes, from companies like Griffin, that contain a 9V battery and a Firewire plug, to provide an IPod boost. This would be another thing in your bag that could be eliminated with this project.

 

[Dougigs]

I'm going to start a new thread, titled The LiPo Project, devoted to the actual development of LiPo technology for headphone amps.

That's not to dismiss this thread -- I started it as a query into the value of these cells for our purposes, and it's developed into a healthy discussion that should continue. But we need another thread devoted srictly to the technology, for those who have decided it's worth the effort.

At this point we've narrowed down charger chips to two useful ones and identified some good low-power cutoff circuits. At this point it looks possible to fit both functions onto the smallest board, since neither circuit requires a lot of bulky external components.

Feel free to join that thread if you're interested in this.

 

[mono]

Quote:

Originally Posted by Dougigs Mono -- the question is, what do you carry with you on the road?

Depends on where I'm going?

Quote:

My point was that your battery-powered rig requires more stuff. Battery headphone amps are used for travel by most people. Most people prefer to travel with fewer things.

Yes that was your point but it isn't true. Being "able" to use a wall-wart, doesn't mean I "need" one. On the contrary it is simply a sign of how flexible your recharging options are if you dont' have to worry about firey explosions in your battery pack.

After giving your situation more thought, IF I were you, I would simply buy a 2nd laptop pack so I had the most versatility in powering both, then essentially an adapter or socket on the pack such that the amp and source ran off the 1st ( or 2nd, rotated if necessary) laptop battery. I might not put another battery in the amp at all, but then again only you now exactly how long you need these things to run and how small they must be, essential information before choosing ANY battery whether it be Li or NiMH or other. There seems to be no clear-cut scenario beyond your initial travel/transportation with *everything* nearby.

Quote:

...probably have a laptop in your bag when you travel. Why not take advantage of the resources available?

One of things I was considering was that initially you talk of space and capacity, yet neither are issues outside of the context of only a very small amp. When looked at as % of weight of all the gear you have, or size, the difference is trivial.

There's also the issue that you keep thinging Li cells somehow "enable" something. They don't, they make every possible scenerio the same or more complex and expensive.

I also wonder about using your USB port to recharge things, a laptop's battery is usually a precious resource as it is even before you start tapping power off of it. Hence another reason why I would probably just get a 2nd battery pack for it and use the two interchangeably per devices as needed.

Quote:

When I mentioned charging your IPod off your amp, I meant when you don't have your laptop with you. The laptop, in this scenario, is used for charging from AC when you're in your hotel or your room or whatever. But I would find it nice -- and I think a lot of others would -- to have a shirt-pocket sized amp that can also give an extra 6 hours' juice to your IPod, because those things run out of power at the darndest times. The fact is that an awful lot of us carry little boxes, from companies like Griffin, that contain a 9V battery and a Firewire plug, to provide an IPod boost. This would be another thing in your bag that could be eliminated with this project.

You have made no mention of how much runtime your iPod lacks, this is yet another issue that only you can weigh.

 

[Dougigs]

Mono -- yes, I think your advice is exactly right: I should get a second laptop computer battery. That way I can charge it using the computer's AC adapter and use it to power my pocket audio gear.

And while I'm at it, why don't I make sure the second laptop battery comes in the right form factor to fit inside a small headphone amp.

And, hey, my IBM laptop's battery just happens to be an 11.1-volt LiPo cell. Imagine if one of those could be stuck inside a headphone amp. Laptop-computer power in a headphone amp -- simplicity itself!

Well, as luck would have it, that's exactly what we're doing.

 

[mono]

Quote:

Originally Posted by Dougigs Mono -- yes, I think your advice is exactly right: I should get a second laptop computer battery. That way I can charge it using the computer's AC adapter and use it to power my pocket audio gear. And while I'm at it, why don't I make sure the second laptop battery comes in the right form factor to fit inside a small headphone amp. And, hey, my IBM laptop's battery just happens to be an 11.1-volt LiPo cell. Imagine if one of those could be stuck inside a headphone amp. Laptop-computer power in a headphone amp -- simplicity itself! Well, as luck would have it, that's exactly what we're doing.

No, I meant actually getting a 2nd battery for your laptop. The exact laptop battery that fits in it. Surely this was obvious?

If you can't see the difference, that the laptop and charger, and battery, together are tested and qualified to be used together, can't see that it's defintely NOT the same thing as grabbing some other battery then hooking up a different charge circuit, putting it in a different case, and for a different use, then you need to back up and rethink this whole project, because it's the DETAILS that count.

Instead of this whole "but I really want more capacity" line of thought, you ought to be thinking about how you'd test this thing. Doing a reference chip circuit and shoving a pack into a case is trivial... it's the SAFETY part that is the whole reason everyone else isn't using Li in every device out there. Certainly there isn't anyone who wouldn't like higher capacity if there weren't any penalties to get there.