[MD1032]

Hey, I'm getting an amp in the mail soon, which is of Meta42 design and built by tpg over on the Klipsch forums (he is ktpg here). It uses an OPA2132. I was wondering what the best battery to use on it is. I need something with very consistent voltage and long life. He reccommended trying the lithium ones, the Duracell Ultras (which I use the AA version of, and they're excellent), and the Energizer e^2's. I also saw a pic of the amp with a Duracell ProCell in it, which I assume he was using for testing and use.

Anyone got advice? NiMH is obviously out of the question.

 

[Jahn]

Quote:

Originally Posted by MD1032 Hey, I'm getting an amp in the mail soon, which is of Meta42 design and built by tpg over on the Klipsch forums (he is ktpg here). It uses an OPA2132. I was wondering what the best battery to use on it is. I need something with very consistent voltage and long life. He reccommended trying the lithium ones, the Duracell Ultras (which I use the AA version of, and they're excellent), and the Energizer e^2's. I also saw a pic of the amp with a Duracell ProCell in it, which I assume he was using for testing and use. Anyone got advice? NiMH is obviously out of the question.

What I do is use the plainviews till they die (has happened, oh, about 4 times in the past month, yeah I listen alot) and just swap in Duracell Ultras while the plainview recharge. Since plainviews take about 15 hours a pop to recharge, it's always nice to keep a spare batt handy and the Ultras are very serviceable in that respect - in fact I'm still going strong with my first pair.

But it will get cost prohibitive if you use the ultras for your main batt - i tried that before i started using plainviews and i blew through a pair in a week - that will get cost prohibitive on you quick. So buy two plainviews and a charger for 30 bucks (norm from headsave hooked me up) and grab one pair of ultras and you should be fine.

 

[MD1032]

Quote:

Originally Posted by Jahn What I do is use the plainviews till they die (has happened, oh, about 4 times in the past month, yeah I listen alot) and just swap in Duracell Ultras while the plainview recharge. Since plainviews take about 15 hours a pop to recharge, it's always nice to keep a spare batt handy and the Ultras are very serviceable in that respect - in fact I'm still going strong with my first pair. But it will get cost prohibitive if you use the ultras for your main batt - i tried that before i started using plainviews and i blew through a pair in a week - that will get cost prohibitive on you quick. So buy two plainviews and a charger for 30 bucks (norm from headsave hooked me up) and grab one pair of ultras and you should be fine.

What are Plainviews? I can't find anything about them online. I've searched hard and long using google, but there's nothing but occasional mentionings of them here. What are they? Perhaps I'll compare them to a Duracell Ultra to see if there's a difference, because it seems it does make a huge difference.

 

[Excalibur]

If you're looking for staying power, it's all about mAh rating. Lithiums have more than alkaline. You can find the mAh ratings in the datasheets of the battery manufacturers and compare.
Here is Eveready's:

http://data.energizer.com/

 

[MD1032]

Quote:

Originally Posted by Excalibur If you're looking for staying power, it's all about mAh rating. Lithiums have more than alkaline. You can find the mAh ratings in the datasheets of the battery manufacturers and compare. Here is Eveready's: http://data.energizer.com/

Well, the best 9v they make is the Lithium, but it's still only 1200 milliamp hours. Are they rechargeable?

edit: and where can I get those plainview batteries and a charger go them anyway? Are they consistent in voltage?

 

[Jahn]

Quote:

Originally Posted by MD1032 What are Plainviews? I can't find anything about them online. I've searched hard and long using google, but there's nothing but occasional mentionings of them here. What are they? Perhaps I'll compare them to a Duracell Ultra to see if there's a difference, because it seems it does make a huge difference.

Here you go! Norm's a great guy to deal with too.

http://www.headsave.com/cables.html

 

[MD1032]

Quote:

Originally Posted by Jahn Here you go! Norm's a great guy to deal with too. http://www.headsave.com/cables.html

OK, thanks! Jeez...they're expensive, though...

 

[tangent]

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long life

Define "long". Over 8 hours? Over 40? Over 100?

With suitable design, you can hit any of those targets. Define the target, and I can tell you what you need to hit it.

Add a case size constraint, and you narrow the choices further.

Quote:

they're expensive, though...

Not nearly as expensive as those nonrechargeable lithiums you're talking about. The NiMHs will be cheaper after only a handful of charge-recharge cycles.

 

[MD1032]

Quote:

Originally Posted by tangent Not nearly as expensive as those nonrechargeable lithiums you're talking about. The NiMHs will be cheaper after only a handful of charge-recharge cycles.

Believe me, I've already figured that out. Even those Procell ones that come in a box of 12 for $20 won't out-do the NiMH in the long run for sure.

OK, my goal is to get at least a week's use out of the amp. Let's name 3 hours a day, or heck, let's just call it 20 hours. tpg left the op-amp socketed, and said Quote:

... for uncannily long battery life... check out the AD648.

He said it only uses like 300 microamps or some insane number like that, and it sounds decent. So that should work.

I would definitely post a really nice scanned image of the top of the amp he gave me to show his work, but the file is too big...darn it! It's a Hammond case BTW. I would gladly post that, too, but the file is too big again... Ket's just say tpg is awesome at getting amps and batteries into small places (he put one in an eclipse mint tin once), and he said another 9v wouldn't fit, so I'm taking his word for it. Just give me an estimate on the battery life with the plainviews, the OPA2132, and the AD648. Also, he did NOT put a power cap on, since he said that would drastically reduce battery life, and if you use a good battery, it shouldn't be that inconsistent and require one anyway.

 

[CBMC]

My meta42 goes through 2 plainviews in parallel in about 3.5 hours. Any suggestions on what could be causing this problem or is this fairly standard for the course? I believe I am using the AD845 OPAMPS. Is this standard for the course for nimh? Or is my amp drawing way to much power? Any help is appreciated.

 

[tangent]

Quote:

let's just call it 20 hours

Okay, then with a 200mAh battery you can only draw 10mA, and you must fully use the battery. (No clipping allowed before the end of battery life.)

You've got 1.5mA in two buffers, and another 1mA in the LED. Add another 0.5mA for small things like the TLE2426 and resistors-to-ground. That leaves 2.75mA per amplifier for the op-amp. The 3mA/ch AD8620 isn't too far over that limit, so personally I'd relax that 20 hour number to get its sound quality. The AD823 is right at our limit, but I think it'll be a bit too aggressive with those Grados. The OPA2107 is under the limit, but it's not specified for low-voltage operation, and I haven't tested one for that myself.

You'll notice that this rules out stacking buffers, the EL2002, and class A bias. You'll also notice that I left the ground buffer out; put a jumper from pin 2 to 7.

Quote:

he did NOT put a power cap on, since he said that would drastically reduce battery life

Only if you turn the thing on and off again frequently. They do draw some power on startup, but beyond that they leak only tiny amounts of current.

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I am using the AD845 OPAMPS

Well there you go. 10mA per amplifier, and not exactly the lowest drop-out voltage of the chips I've used. That change plus adding the ground buffer in the amp above, and you'd be lucky to get 7 hours.

As for the rest, perhaps you're stacking buffers, or using the EL2002, or biasing the op-amp into class A, or running your LED a little hot, or simply not able to run the battery all the way down before you hit the clipping point.

 

[Prune]

The rechargeable NiMH 9 V are 200 mA. Terrible. However, RatShack has some Lithium 9 V which last very long; I've yet to use up mine (though I ony use my META42 for portable listening).
I think it's best to use a bunch of AA NiMH, of the 2300 mAh variety. They last a good deal longer than non-rechargeable batteries, can be charged 500-1000 times, and you can get a 1 hr charger for them cheap off eBay. By the time you can no longer recharge them, we'll probably have already switched to fuel cells

 

[MD1032]

Hmmmm...I did indeed notice the plainviews only get 200 mAh, but considering how I can simply charge one overnight for about 500 nights, times however many hours I get out of one, it's a better deal for sure. I already contacted Norm.

BTW, Tangent, how do the OPA2227 (probably going to obtain and try out) and OPA2132 (in use) fare against each other in terms of battery life?

 

[CBMC]

Quote:

Originally Posted by tangent As for the rest, perhaps you're stacking buffers.

I have 2 of the suggested buffers on each channel(excluding the ground). If I was to take off one of the buffers per channel how much extra life could I expect from my batteries?

 

[tangent]

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how do the OPA2227 and OPA2132 fare against each other in terms of battery life?

The 227 draws a bit less power and will run to slightly lower supply voltages. It won't be a dramatic improvement, but it should be a noticeable one.

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I have 2 of the suggested buffers on each channel

I don't have enough information to answer that. And anyway, why ask me? I've all but spelled the procedure out above. Things you need to find out:

- How much current is the amp currently drawing?

- What is the quiecent current of the buffers you are using. The EL2001 and EL2002 are both "suggested", and they have different Iqs. (1.5mA and 5mA, respectively.)

- Since you're probably clipping before you fully run the battery down, what is the battery voltage when you change it?

- Does the battery life halve when you go with just one battery? You're not supposed to run rechargeables in parallel. It may be that it does not halve!

If you're still up in the semi-linear part of the battery discharge curve (say, 9.6V +/- 0.5V for the Plainviews), I'd say the first thing to do is switch to a more efficient chip if battery life is your concern. You need to use something that doesn't poop out until the voltage is outside that curve, where 80% of the battery life lies.