[drp]

I have a Headsave Tempo that I'm currently running with a 16-cell pack. Given the fact this amp will suck the batteries down past (way past) 1.05 volts per cell before shutting off, I surmise that the minimum voltage is actually quite low.

Is there much of a difference between running this amp from a 10- to 12-cell pack vs. a 16-cell pack, sonically speaking? Is it headroom that's gained with higher voltages? If it matters, it has the AD8620 and dual buffers.

More data: My computerized charger/conditioner has a 12 cell maximum, so for my Tempo, I have a pack that's split at 10 cells and 6 cells. Connected in series for powering the amp and charged separately. I use Sermos (Anderson Powerpole) connectors for the various connections. Very low loss connectors, and I can easily reverse the polarity for different devices or use each pack separately.

I asked a related D25 voltage requirements question in the Portable Audio section (look if you can help). It would be cool if, in a pinch, I could run the Tempo off of 10 cells and the D25 off of 6, and only have this one Frankenstein's battery pack to lug along. If interested in what this pack looks like, I've attached a pic. Just don't laugh at the tape job (it's temporary….)

TIA,

Dave

 

[Budgie]

Higher voltage supply = higher possible voltage output. The chips can only swing to a percentage of the rail voltage. More important if you have high impedance cans then low impedance cans. The max voltage you can run the amp at is the rated voltage of the lowest rated chip in the amp. I don't have the data sheet for the 8620, but I think it is a +/- 13 volt max. You can download the data sheet if you want to verify it. Hope that helps.

 

[tangent]

Quote:

It would be cool if, in a pinch, I could run the Tempo off of 10 cells

That would put your main running voltage at about 12V. (1.2V/cell) This is +/-6V as far as the op-amp is concerned. Page 2 of the datasheet says that the chip will swing within 1V of the rails with a +/-5V supply into a 1K load. Graph 10 in the datasheet suggests that the actual performance is more like 0.8V into the higher load that the buffer presents to the op-amp.

So, 12V minus twice 0.8V is 10.4V. Divide that by 2.828 to get RMS sine wave voltage from that value, and you get 3.6V. Trust me, that's plenty for almost any headphone. Most headphones require 1.5V or less.

Repeat the process with the minumum battery pack voltage. 1V/cell is a good minimum. It comes to 3V. Still plenty.

 

[drp]

That all helps a bunch, guys, thanks. I downloaded the datasheet to reference your comments.

I've tons to learn, and enjoying every second of it. I'm also at the moment enjoying Johnny Lang through a D25, Tempo, and E5s. Sweet!