Battery-powered supplies

[karma]

hmm how small is small? and what are you running?

[Nuuk]

.

hmm how small is small?

Well as small as you like if they only have to power something for an hour. What about the batteries used for power tools for example, or even a set of regular torch batteries. Anything in fact that can be recharged often.

[karma]

i would say it would work for somthing low powered sure.
like a preamp. but if its for say a amp you would have to string
alllot together for it to work and it will cost you as much as a single sealed 12v cell i say try it

thay may run hot

[mac]

Greetings,

I recently built a buffered "passive preamp" that is powered by SLA batteries. The sonic results are stunning.

I used Shallco stepped attenuators with Resista resistors and OPA627 opamps as buffers. The batteries are rated at 7AH.

<center><img src="http://207.115.74.87/vcm/WH/images/DCP_2316.JPG"></center>

[karma]

nice work

[Peter Daniel]

Originally posted by mac
I recently built a buffered &quot;passive preamp&quot; that is powered by SLA batteries. The sonic results are stunning.

Nicely done.

What did you use for charger? I'm thinking about similar preamp.

[Nuuk]

I recently built a buffered "passive preamp" that is powered by SLA batteries. The sonic results are stunning.

And the visual results too - congratulations.

Is that two stepped attenuators that you have used instead of one stereo?

And before anyone asks, where did you get those knobs?

[mac]

<center><img src="http://207.115.74.87/vcm/WH/images/DCP_2305.JPG"></center>

What did you use for charger? I'm thinking about similar preamp.

I used two Velleman SLA charger kits. Initially I was going to build a charger from scratch or buy two of the circuits that Chris Brady uses for the Teres. The Velleman works very nicely since it automatically switches from deep to trickle mode and can remain connected to the batteries 24/7. In addition, I have a switch on the front panel of the preamp to take the charger out of the circuit while listening.

Is that two stepped attenuators that you have used instead of one stereo?

Yes. I struggled with this for some time. I really wanted a single control but didn't want to add an additional balance pot to the signal path. The Shallco switched can be ganged together but they already require mucho effort to rotate.

And before anyone asks, where did you get those knobs?

I had a local machinist spin them for me. They are 2.25" in diameter and 1" high. The cost was very reasonable.

[Nuuk]

Yes. I struggled with this for some time. I really wanted a single control but didn't want to add an additional balance pot to the signal path.

Hi Mac, I have never had a problem with channel balance when using a stepped attenuator! You must have very fine steps on your attenuators, or quite a big imbalance! Do you know what is causing the imbalance?

The Shallco switched can be ganged together but they already require mucho effort to rotate.

Yes, this is nearly always a problem with lightweight equipment like hi-fi. I once built a 'two-switch' stepped attenuator using two 12 position rotary switches and ganged them together but the feel was just not right.

I like the feel of Bloore Edwards switches that I use now, but only after replacing the springs with something 'lighter'.

I had a local machinist spin them for me. They are 2.25" in diameter and 1" high. The cost was very reasonable.

I'm surprised that 'decent' knobs aren't more widely available! It's very difficult to find any good looking knobs 'off-the-shelf'.

[Steve Eddy]

Originally posted by Nuuk
I'm surprised that 'decent' knobs aren't more widely available! It's very difficult to find any good looking knobs 'off-the-shelf'.

I think <a href="http://www.kilointernational.com/">Kilo's</a> ML series knobs are quite nice for an off-the-shelf:

<center>
<img src="http://www.kilointernational.com/new/Knobs/ML_Series/mlknobs.jpg">
</center>

The two rings are like rubber O-rings. Come in diameters from .5 to .95 inches, for .125 inch, .25 inch and 6mm shafts and available in black and clear with gloss or matte options.

se