[twodeko]

hey there... im going to start working on my PIMETA and have seen numerous posts about power supplies and battery's working in a amp and was curious where to begin with implementing something along those lines.

i have been browsing ELPAC looking at their external power supplies, but in all honesty i am not all too sure what i am looking for. i realize a 24V DC output voltage would be good enough but what numbers am i looking for with watts and amps. also, how would i go about connecting this to the PIMETA (would i need any additional circuitry) and if i wanted to use batterys, how could i switch between the two.

since this will be my second project, im also curious how 24V would fare with somewhat of an electrical newbie... i would rather save the money with not having to buy battery's but still be able to use it on planes and such. am i going in the right direction, help... comments, pictures... links?

A900's should be here soon as well, wheres the A900 smiley?

(((((

)))))

 

[tangent]

Quote:

was curious where to begin with implementing something along those lines.

There's some info on this in the Tweaks section of my CMoy tutorial, under where it talks about adding a DC power supply.

Quote:

i have been browsing ELPAC looking at their external power supplies, but in all honesty i am not all too sure what i am looking for

The most important thing you want to know isn't on their site, at all. That is whether the supply is isolated or not. I believe I talk about this in the PIMETA docs.

Of Elpac's single-voltage 24V offerings, the only one I know for certain is isolated is the WM080. Elpac has told me that the more expensive MW1224 is also isolated, but it's a switcher, so I've not been tempted to try it.

Quote:

i would rather save the money with not having to buy battery's but still be able to use it on planes and such.

The easiest way to handle this is with a closed-circuit DC power jack. This is covered in my panel components article. The downside of this is that the switch inside such a jack is prone to being damaged.

Another way to do this is with two diodes, one inline with each supply. Then you pick your wall supply to be significantly higher than the maximum battery voltage, which will make the wall supply run the amp when it is plugged in, and the batteries otherwise. The downside of this is that you get a small voltage loss from the batteries, which might be enough to shorten the run time of the amp.

 

[twodeko]

thanks for the reply tangent!

so i understand i am looking for an isolated jack (does this imply that a ground is not needed?)

i was on the ELPAC's site and saw the power supply but do they supply a jack along with that or do you have to find an isolated one that fits the terminating end? i have seen posts of people talking about getting an isolated DC jack and then having problems with the input output jacks... i was just curious how a DC jack affects the circuit as a whole.

i read through your articles but was still left with these questions, along with how i would step down a 24v source (which i assume is delivered into the +/- battery placeholder on the PCB) since the circuit normally takes a 9V power source.

i will look more into isolated jacks but would like to be sent moving in the right direction

 

[skyskraper]

depending on what your op amp maximum voltage ratings are, your pimeta should work nicely with 24v. ive found the more volts u give chips (up to their limits, but im yet to try the limit) the more you will get back out of them.

 

[tangent]

Quote:

i am looking for an isolated jack

You will need an isolated jack if you use a metal case, but that's not what I was talking about above. I was talking about an isolated power supply.

The former just means that none of the contacts is connected to the body of the jack, so it doesn't tie any voltages to the case. Typically such jacks have 100% plastic bodies.

The latter means that none of the input connections (i.e. AC hot, neutral, and ground, if present) connect directly to any of the outputs. If you don't have an isolated power supply with a PIMETA, virtual ground gets tied to V+/2 above real ground, so that when you plug the PIMETA into something that uses real ground for audio ground, you cause havoc with the virtual ground. With an isolated power supply, virtual ground can 'float' to the ground potential of the equipment you plug into it.

Quote:

do they supply a jack along with that

Of course not.

Quote:

do you have to find an isolated one that fits the terminating end?

Yes, but this is not difficult. I give one in the parts list.

Quote:

the circuit normally takes a 9V power source.

If it says 9V anywhere, that's just an example. The limits -- both high and low -- on voltage come from your capacitors and chips. Your headphones also play into this. Read this if you are thinking of using anything other than 24V.

 

[twodeko]

hey tangent... i was looking into this more and saw your impressions of the switching DC jacks but i think that might be my best bet. ill go ahead and grab one of those and then a regular one so that i can replace it if needed, but i was curious if this was what i needed for a 24V DC source.

DC Jack

the one that is in your cmoy guide is rated for 12V DC so i think this is what i will need. if i go ahead with that then i can still have my batteries in the case, or is that not a switching jack?

once the voltage reaches the PIMETA, i'll plug that into the +/- input but besides that, do i need to populate the voltage divider to give me a +/-12 V and then a 0V line for ground?

thanks again!

 

[twodeko]

bump for me plz