[Emon]

What's an appropriate voltage for a standard PIMETA (all the standard parts listed on tangent's site, nothing special) with AD843s biased into class A? I did some searching and I've seen people with around 16 or 24 volts. Two 9v batteries in series seems to be appropriate, so I would assume 18v is a pretty good ballpark. What happens if you go higher, like 24 or even 30 volts? I'm not looking at a power supply in that range, but at what point would most opamps and buffers start to fry (I'm assuming all caps are above this level, like 50v). Also, how much current does one need? From what I gather, 0.5 amps should be more than enough.

I'd appreciate some more info...I've been searching but unable to find anything that pertains to my exact situation, and I want to be sure before doing something stupid.

 

[BrokenEnglish]

tangent recommended in general 24v psus for his amps. 18v certainly are sufficient, but the additional 6v could help to get a better pronounced musical reproduction in some cases. 300-500mA current usually are enough. also with 24v you're usually on the safe side with the most common opamps. check the datasheet of your opamp if you want higher voltage. amb collected some values on his m³-page: http://www.amb.org/audio/mmm/psu.html

 

[Emon]

Ah, thanks. Hmm, not sure I want to buy a 24v regulated power supply. I think I'll modify my PC's power supply a little and run 24v out the back. I should get much more stable a voltage this way. I always use my cans at my PC anyway, except road trips.

Edit: Is 22 awg wire enough for the like, 12watts at most a PIMETA might use? I think it should be, but I don't have my gauge/resistance/length sheet lying around.

 

[BrokenEnglish]

Quote:

Originally Posted by Emon Ah, thanks. Hmm, not sure I want to buy a 24v regulated power supply. I think I'll modify my PC's power supply a little and run 24v out the back. I should get much more stable a voltage this way. I always use my cans at my PC anyway, except road trips.

don't use a pc's psu (those are switching psus)... take a look at tangent's site: http://www.tangentsoft.net/audio/opamp-ps.html

 

[Emon]

Why, because of the noise? How might I determine how much noise my PSU would be putting out?

 

[BrokenEnglish]

Quote:

Originally Posted by Emon Why, because of the noise?

exactly...
Quote:

Originally Posted by Emon How might I determine how much noise my PSU would be putting out?

that's difficult without appropriate equipment. most el cheapo dmms for example only measure down to a 1/10 volts ac. get some impressions here: http://tangentsoft.net/elec/psu-tests/

 

[Emon]

The electronics labs on campus have some of the highest end equipment around in them...I know I can get into one of the lower end EE tech ones since I took an EE tech class for kicks. I should have the tools to measure it, but it's probably not worth the bother since my PSU would probably have quite a bit of noise anyway.

In that case, are there any cheap AND good power supplies I can get? I didn't really want to blow $30 on a power supply. :/

 

[BrokenEnglish]

buy an unregulated ac-wallwart and build a psu on your own, for example inside the case of your pimeta. for parts you'll stay under $5, using a generic 7824-voltage regulator, 2 foil caps, ~2200µf elcap, 4 rectifying diodes and a breadboard. should be at least on par with the ubiquitarious elpac-psu.

 

[Emon]

Eh, not sure I want to mess around with yet another circuit. I'm already taking a bit of a jump by having my PIMETA be my first amp. I'm hoping that my moderate audio experience and moderate electronics experience are enough. I might just by a good power supply, I need to get a better job anyway.

Edit: I just added up the prices for all the parts I need, around 120 dollars after shipping. How the hell did that get so high? Bah. And another 30 for a power supply leaving me down $150. It sucks having to order stuff from four different places online, all of which screw you on shipping costs.

 

[BrokenEnglish]

you could buy the velleman kit K1823...

...there's all in it, that's necessary. still cheaper than most consumer regulated psus, most likely better in performance.

 

[Emon]

That's going to cost about $20 shipped, might as well buy a nice PSU by that point. If not because of the Imight****upandfrymyexpensiveamp factor.

 

[bg4533]

Quote:

Originally Posted by BrokenEnglish you could buy the velleman kit K1823... ...there's all in it, that's necessary. still cheaper than most consumer regulated psus, most likely better in performance.

By the time you tack on a transformer, IEC, and a few other parts the cost is about the same as the Elpac.

In my opinion the PSU is one of the most important parts of the amp and is not a place to completely skimp. Batteries will sound as good or better than most PSUs given enough voltage. Cheap power supplies will hurt the sound and cheap wallwarts might not even work.

Generally the more voltage to an opamp the better up until the opamps max. Most BB opamps will take 36V. AD opamps are a little more varied. The AD8620 will take ~26V. 24V is generally good for everything.

What 4 places are you ordering from? You should be able to get everything except the PSU from Tangent and Digikey.

 

[Emon]

Digi-Key, Mouser, Futurlec (for the AD843s and a few resistors and caps that save me a few cents compared to the other places), and All Electronics (some misc components, jacks and a few other things for other projects, not included in that cost though). I do need to do a bit more consolidating and maybe a little more searching...I really need to get the shipping cost down. Oh, and I'm buying PIMETA and crossfeed boards as well as that Alps RK079 or whatever the $3 pot is from tangent's shop, which is like 20 dollars shipped. I did manage to save $4 by getting my knobs from Mouser. I could cut that cost down to about 50 cents by getting black plastic knobs from AE...but those black anodized ones are far too sexy.

 

[BrokenEnglish]

Quote:

Originally Posted by bg4533 By the time you tack on a transformer, IEC, and a few other parts the cost is about the same as the Elpac.

i suggested the kit as case-internal regulator-unit for an external ac-wallwart.

 

[Edwood]

So the velleman kit K1823 would be wired inline between the DC input jack and the power input on the Amp board?

-Ed