Transformer VA Rating vs. Current Rating

[JhonDoe]

Thanks for info Joan2!!
since raon(Manila) is 3 to 4 hours away from Angeles city I cant find time to go there. Is there any toroind trafo here in our country? by the way, were you in manila?

from angeles city? i see your interested in building gainclones now JohnDoe. Good luck.

Yes, i'd already finish 4 mono of them(2-OPA541 one inverted and one non-inverted)and(2-OPA549 one inverted and one non-inverted) last 2 months, only 2 of them are connected in my bench PS the 2 inverted(1-541 and 549 for the other)


What 'bout you JojoD818? were u from?

[Tony]

Originally posted by Jocko Homo
But larger transformers sound better..........as they operate further from saturation.

Jocko

runs cooler too!!

tony

[Tony]

Originally posted by JhonDoe
Thanks for info Joan2!!
since raon(Manila) is 3 to 4 hours away from Angeles city I cant find time to go there. Is there any toroind trafo here in our country? by the way, were you in manila?

i'm from pasig city....unfortunately i don't know any torroids in manila except those from discarded japanese amps, i am working on one...last time i made a torroid was in early 90's which i used for a leach amp....

believe me, you will miss nothing from not having a torroid except perhaps its small outline as compared to an ei of same va rating...

i have built lot's of amps using ei's that are stone quiet rvrn eith volume controls turned all the way up....

tony

[Matttcattt]

Originally posted by Easyamp


500ma into even an 8 ohm load is only 2 watts peak how can you run a sub with only 2 watts? I*R=V which is 4v V*I=P which 2 watts. Also 25v dual secondary gives a static (no load) voltage of 35v per rail. rms math, 25v*1.41 =35v

but if that's all you GC need's then 60va is plenty.

Well, thats how much it draws. It could be limited by my bench power supply I suppose...

[JojoD818]

Originally posted by JhonDoe


What 'bout you JojoD818? were u from?

I'm from Valenzuela City. Malinta exit from NLEX.

[Tony]

Originally posted by Matttcattt


Well, thats how much it draws. It could be limited by my bench power supply I suppose...

this just goes to show that our listening levels average in the 2watt or so levels....

[Matttcattt]

Originally posted by joan2



this just goes to show that our listening levels average in the 2watt or so levels....

Well, this was at full volume and my sub (Eminence Beta 15 (350W)) bottomed out with a 40Hz sine wave.

Not that that means much, but I was told the design would output 100W+ into eight ohms.

I dunno, its loud enough for my liking.

[Tony]

Well, this was at full volume and my sub (Eminence Beta 15 (350W)) bottomed out with a 40Hz sine wave.

if you mean you tested your woofer with a sine wave, then this is no surprise, energy content of sine waves is much more than music signals...

even if your woofer was rated at 350w it could still be damaged with a 2watt sine wave input...

[Easyamp]

I'm not sure what to say, either I'm missing something or you guys are pulling my leg.

Even giving that most dmm's measure rms and not peak of the sine you would still only gain 1.41 times 2 watts which is the peak of the sine wave.

If you pump a 2 watt 40hz sine wave into a speaker that is rated at 350w (rms or peak not real important here considering the safety margin) and the speaker bottomed then either the speaker is rated for less then 2 watts or something’s a miss in the measuring.

The before stated .5A peak current load was the rail current not the output current and if this is a standard class AB GC then this .5a figure doesn't translate to output directly. The output depends on the efficiency of the amp, which is not 100% so the output will be less then supply. I've seen figures for some class A amps efficiency of less then 10%(output level dependent), I'm not real sure about AB GC's.

I’m curious how you are measuring the current load of your amp this could be the misleading point.

You said before you are running a mixed bridge parallel configuration, are you measuring in front of one of the chips or right after the bridge and filter caps, or the ac going into the bridge/caps? If you are using a dmm check that it will measure other then 60hz ac current if measuring after trnsfo I've had this problem before.

I stick a low value power resistor in line with one of the rails (.22 ohm or something) and measure the voltage drop and use ohms law to find current if I'm curious about the current load.

Also I'm curious of the voltage drop across a .22 ohm in line with the speaker at full volume, should be around a few volts if bottoming a 350w speaker.

You can make a lot of power from mixed bridge parallel GC's setup and I wouldn't be surprised if you bottomed out a driver but not with 500ma.

Cheers

[JhonDoe]

Hey Jojod818!!

Bro. I saw u're Parallel/bridge set-up in your website, got some questions!, did u use .1% or 1% res or special component for that set-up? how did u manage to match the output?

I'm planing to use opa541 in inverted setup(parallel/bridge) do u think this will work? what will be the maximum output power for this set-up?

Money and time for me is to tigh, gathering an info and safty measures before building it is my fist concern.

one more thing, can i use 5% resistor? i cannot find .1% not even 1% resistor anywhere in angeles city.