Just a quick power supply capacitance question

[markiemrboo]

It is...... and that page doesn't answer how it could work if the negative rails are joined?

[Nuuk]

I don't know either but what I was suggesting is that, that was the correct way to wire up a regulated supply.

[markiemrboo]

Oh right. Hm.

Well that's how I currently have it (like the second picture in the diagram from your site), and I think that would be equal what I tried to simulate (see screenshot). It doesn't really seem right, but I dunno. I was hoping someone here would be able to explain it to me.

I can't seem to find much on google regarding two "bipolar" regulated supplies running off of just one dual secondary transformer either!

[Nuuk]

It's not really two supplies. It's a single dual rail supply.

[markiemrboo]

Now I am confused. Are you sure you're following what I am talking about? That is, one regulated supply per channel, but with a single dual secondary transformer, and one bridge rectifier per secondary?

[Nuuk]

How are you doing the regulated supply then? With only one bridge you would need a positive and negative regulator!

[AndrewT]

Hi Markie,
If you had asked before you bought this hardware for your first project, I would have advised that you do not include a regulator/s for supplying a poweramp.

For a first, keep it simple.

Unfortunately the transformer without a regulator may supply too high a voltage into your chipamp.

What exactly do you have:-
transformer, chipamp, speaker impedance?

[Nordic]

About the size thing... i tried the prereg - regulator path to avoid a second transformer, after some headscratching, I remembered how easily a 9V battery drove similar circuits in headphone amps, so it doesn't use too much power... 1 hour later I had a small preamp with a its own PSU made out of a small PCB mount transformer... turned out much smaller than what I tried first to prevent the extra PSU...

[markiemrboo]

Originally posted by Nuuk
How are you doing the regulated supply then? With only one bridge you would need a positive and negative regulator!

Maybe you should update that diagram on your site, or add some text under it stating this



Talking about that one. There you have one transformer, one set of bridge rectifiers, and two regulated supplies. This is how I currently have it, and while it does work (apparently, too scared to turn my amp on now)..... it appears even you know that it is 'wrong' [for this particular regulator layout i.e two lm338's)?

Originally posted by AndrewT
Hi Markie,
If you had asked before you bought this hardware for your first project, I would have advised that you do not include a regulator/s for supplying a poweramp.

For a first, keep it simple.

Unfortunately the transformer without a regulator may supply too high a voltage into your chipamp.

What exactly do you have:-
transformer, chipamp, speaker impedance?

Well, it's not so much of a problem if I can't run two sets regulators. I'll just have to "downgrade" to a single regulator board for both channels This is still a bit of a shame, as I was planning on perhaps putting four channels in there, which would really probably need at least two sets of regulator PCB's eh?

Speaker impedance..... well, all I know is 8 ohm nominal. I opened them up (original Celestion 7's), but the drivers are unmarked so I don't have any graphs etc Shame really. Transformer is 25VAC dual secondary 500va. From what I remember this gives me about 37V DC.

I really can't afford to spend yet more money on it (hence just downgrading to a single regulator PCB for both channels). I've spent uh... way more than enough on it already!

Is there absolutely no possible way to have two regulated (with lm338's) bipolar supplies off of a single transformer? Rod Elliot has a schematic for two unregulated bipolar supplies off of a centre tapped transformer, but this isn't quite the same obviously

Originally posted by Nordic
About the size thing... i tried the prereg - regulator path to avoid a second transformer, after some headscratching, I remembered how easily a 9V battery drove similar circuits in headphone amps, so it doesn't use too much power... 1 hour later I had a small preamp with a its own PSU made out of a small PCB mount transformer... turned out much smaller than what I tried first to prevent the extra PSU...

Fair play I'll have to just use the littler transformer I have and somehow make it fit then.


Apologies for the delay. We've just had a power cut... that lasted....about 9 hours!

[Nuuk]

Maybe you should update that diagram on your site, or add some text under it stating this

Talking about that one. There you have one transformer, one set of bridge rectifiers, and two regulated supplies. This is how I currently have it, and while it does work (apparently, too scared to turn my amp on now)..... it appears even you know that it is 'wrong'?

Sorry, I'm getting old (after the hundreds of hours work putting that site together) and all I can see is options with two sets of four rectifier diodes - making two rectifier bridges.

Referring to the page on regulated Gainclones, isn't this diagram clear enough?



However, I do apologise for this shocking service! Would you like a refund?