Voltage doubler to power op amp?

The usual way to start transformer design is to work from the VA rating and then compute dimension of the stack^4, not to start with stack. There are such things as 4VA transformers with 10% regulation-and readily available. This part is junk.

[snip drivel]

You're not going to tell me anything- have selected far more transformers than you ever will. We are talking about "rectifier" transformers, they are always overdesigned for high RMS crest factor typically at 60-90o conduction angles, and the iron must be derated for the higher frequency losses to meet the usual 40oC temperature rise at full VA loading. The design of these transformers goes well beyond wire resistance, window areas, and peak static flux. The stack size is a dependent variable- that means it depends on the performance specification and not the other way around.

Phil Allison wrote: [snip drivel]

Everyone appears to be a "bullshit artist" to the incapable non-performers...you just don't come close to being functional. Take your "bullshit" reply to that rinky-dink speedo trivia-"put a capacitor in there somewhere"- impressive. You lose all credibility when you're overtaxed by that kind of thing.

"Porky"

** Hope you are not using an inverting gain stage.

Hope the spring unit is not wired backwards with the low Z coil as output.

......... Phil

"Fred Bloggs"

** Bullshit.

A "4VA" transformer has typically 25 to 30 % regulation - provided the VA rating is based on the usual, safe, free air temp rise of circa 60 degress C. Almost all the voltage drop under load is due to winding resistance.

If you take an " 8 VA " transformer ( physically larger of course) and rate it at 4 VA, then the regulation % will be twice as good as when it is rated at 8VA - obviously.

Take the same 8 VA design as above, improve the insulation so it can run safely at 130 degrees C and then the VA rating can be doubled to 16 VA - but the regulation % will then be more twice the previous figure.

No magic - just ohms law in action.

......... Phil

"Fred Bloggs"

** Fuck you - bullshit artist.

** Not when you snip it all and disregard it - I can see that.

- have selected far more

** Had lots more hot dinners too, I suppose .......... ** Off with the faries for sure.

( snip inane drivel)

............ Phil

"Fred Bloggs"

** I wonder who this appalling man is talking to.

I know it isn't me and I hope it isn't you.

........ Phil

Only use a 5532 with lowish impedances. The input current ( and hence input noise current ) is quite large for an op-amp.

The topology of the gain stage is important too. An inverting stage will be noisier than a non-inverting one for example. Keep the feedback path impedance low ( resistance > thermal noise ).

Graham

Yes butt... that's how I have fun, build>Only use a 5532 with lowish impedances. The input current ( and hence

It seems a whole new design is needed for a quiet opamp-driven reverb. I have found a couple and like Roy Mallory's design, which uses a J-fet in conjunction with an op-amp, and it's not a 5532 either. No need to re-invent the wheel. Cheers.