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 Post subject: HMMM10/Stella Amp
PostPosted: Mon Sep 26, 2011 12:47 pm 
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I have a couple of questions about the Stella Amp build for HMMM10:

- Are the kits going to have pcb-mounted or separate pots? I would like to mount my amp in a piece of cherry or walnut.

- What is the best way to power these things? This page http://www.crazybutable.com/projects/stella/power makes my head hurt.


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 Post subject: Re: HMMM10/Stella Amp
PostPosted: Mon Sep 26, 2011 2:21 pm 
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they are pcb mount but you can remove them and add them anywhere by soldering on jumpers.

9V is the easiest.


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 Post subject: Re: HMMM10/Stella Amp
PostPosted: Mon Sep 26, 2011 3:54 pm 
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paulsobczak wrote:
9V is the easiest.

But not recommended:
Quote:
Using a 9 volt battery is not recommended if you are using the Stella amp as an amplifier. It will work but you'll only get about 20-40 minutes on a charge at loud volumes.... [T]he amp will keep getting quieter and quieter as the voltage draws down.

Shouldn't amps get LOUDER as the song goes on?


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 Post subject: Re: HMMM10/Stella Amp
PostPosted: Tue Sep 27, 2011 8:16 am 
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heuermh wrote:
paulsobczak wrote:
9V is the easiest.

But not recommended:
Quote:
Using a 9 volt battery is not recommended if you are using the Stella amp as an amplifier. It will work but you'll only get about 20-40 minutes on a charge at loud volumes.... [T]he amp will keep getting quieter and quieter as the voltage draws down.

Shouldn't amps get LOUDER as the song goes on?


if you are planning on using it for long periods batteries are not a good choice, if you need if for a few minutes then batteries are a great choice.

not sure what you mean by get louder as the song goes on, I don't think that would be beneficial.

There are some Lithium ion batteries (think cell phone batteries) that will have a longer amp life than a standard 9v, that might be worth looking into. Or you could use a car battery :)


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 Post subject: Re: HMMM10/Stella Amp
PostPosted: Tue Sep 27, 2011 2:48 pm 
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My tube amps get louder the longer they are on, as the tubes warm. So does my old Philco radio, so much so that I always have to turn down the Twins game by the seventh inning because it gets too loud.

I'm thinking this might not be the right amp kit for a newbie like me to try.

I still have a couple 9v amp kits in a box at home that I should build first (Minty Amps, http://www.mintyamps.com , although the site looks dead now).


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 Post subject: Re: HMMM10/Stella Amp
PostPosted: Tue Sep 27, 2011 4:28 pm 
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A 4- or 6-AA battery holder sounds like it should work well, they typically have 3-4 times the capacity of a 9-volt.

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 Post subject: Re: HMMM10/Stella Amp
PostPosted: Thu Sep 29, 2011 6:46 am 
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Answers to questions!

1. They will be panel mounted pots. The kit comes with wire for the pots, but not wire for anything else, so you need to have your own wire. (I'm working on finding the right wire to include with kits. Haven't found it yet.)
2. heuermh, thank you for your feedback about my power page. I just get so excited when I finally understand something that sometimes it all comes out at once instead of being neatly organized. Let me sum it up for you. Either use 4 AA batteries (or 4 C cells or 4 D cells, etc.), or use a 5 volt DC switching regulator wall plug. You'll know it's 5 volts DC because it says 5 volts DC on it. And you'll know it's a switching regulator because it will be very light weight instead of heavy like a transformer wall plug. (edit: make sure it can deliver at least 500ma.)

If you don't like either of those options then you can wade through the power page. Or ask me questions.

Ax-man has some good options for 4 or 6 cell battery holders, or at least they did last time I was there. :)


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 Post subject: Re: HMMM10/Stella Amp
PostPosted: Thu Sep 29, 2011 3:16 pm 
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Instead of worrying so much out about over voltage problems would you be able to use some voltage regulator that has a low drop out voltage?

E.g. A 12-volt regulator that outputs 12V for an input of 12V~30V (arbitrary number, but much higher than the op amp limit). If the input voltage is lower than 12V it outputs roughly the input voltage (perhaps a few mV less) Therefore, if you have 3.3V on the input of the regulator you get ~3.3V out but if you hook up an overcharged batter at 16V you get a safe, level 12V supply for the rest of the circuit.

I don't have time right now to look up specific parts, but I'm assuming something could be had for reasonable price to make the whole thing more robust.

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 Post subject: Re: HMMM10/Stella Amp
PostPosted: Thu Sep 29, 2011 8:06 pm 
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A zener diode or dc-dc converter would also work


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 Post subject: Re: HMMM10/Stella Amp
PostPosted: Sat Oct 01, 2011 7:21 am 
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4 double AAs. That's what I designed the amp to run on primarily. But I wanted to give the end user lots of flexibility in what power source they chose. So why design in a regulator if it's never going to be used? That was my thinking anyway. I'll look into low drop out regulators for version 2 when I redesign the PCB.


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