High-End Regulated Buffered Inverted GC

[carlosfm]

Originally posted by moving_electron
Not aware of one but I wonder since generally I don't see both.

Generally I don't see correctly bypassed op-amps.

[ErikdeBest]

Originally posted by tbla
carlos - try the lt1083...with 470uF on the output and 0,1uF on the 3886.........

There´s a guy at www.marktplaats.nl selling 10 units of lt1083.

Go to "elektra/tv´s/witgoed", than "electronische onderdelen". Title is "linear technology 7,5A..." posted 15-06 (yesterday).

Erik

[azamkita]

Dear friends

I have a non inverted GC with 380 VA. The transformer has 3 wires at the output which is 18,0,18 ac respectively.

I hope GC master, expert and gurus to help me with some of my questions.

A- How to use Pedja’s circuit with my transformer ?. I mean, how to use LM338 with this kind of transformer ?.
B- If no other method, I have to use LM317/337 chips for the regulation, what is the maximum voltage out can I achieve ?. ( Assume I use 18acX1.414=25Vdc)
C- Has any one measure the current at the +ve or –ve of this LM3875 when it perform low bass or complex music ?.

Thanks and have a nice day

[Nuuk]

To use your transformer, you must do what Carlos did. That is to open up the transformer, locate the ends of the two windings and separate the ends that are joined to the centre-tap and then add a fourth wire so that you have four leads.

Otherwise, you must get a new transformer with separate secondary windings!

[Andypairo]

Originally posted by Nuuk

Otherwise, you must get a new transformer with separate secondary windings!

And since you are at it take a slightly higher voltage secondary, say 25 to 30V (since regulating makes you lose some supply volts)

Cheers

Andrea

[carlmart]

Originally posted by azamkita
Dear friends

I have a non inverted GC with 380 VA. The transformer has 3 wires at the output which is 18,0,18 ac respectively.

I hope GC master, expert and gurus to help me with some of my questions.

A- How to use Pedja’s circuit with my transformer ?. I mean, how to use LM338 with this kind of transformer ?.
B- If no other method, I have to use LM317/337 chips for the regulation, what is the maximum voltage out can I achieve ?. ( Assume I use 18acX1.414=25Vdc)
C- Has any one measure the current at the +ve or –ve of this LM3875 when it perform low bass or complex music ?.

What Nuuk suggests and I would too, opening the transformer, may not be possible. In that case, what you can do is build the discrete regulator suggested at Pedja's site, which he seems to like more.

The problem with the 317/337 is not the voltage, but the current. It can only handle up to about 1A. To handle you have to add an external transistor. But several advantages of those chips, like low impedance, will be gone.

As far as I know no one has taken the trouble of measuring those current demands.


Carlos

[azamkita]

Thanks to Nuuk,Andy,Carlos for your answer,

I'll take note - thanks

BTW, any possibilities if I parallel 7818/1918 or I parallel LM317/337 to increase the current let say to 5 amp or 7 amp ?.

Come back to transformer part, should I reduce the secondary or increase the primary ?

Give me some lite plzzz.

thanks and have a nice day.

[tbla]

why not just use the lm1084 or lt1084 or lm338 or (the best) lt1083.........?

[carlosfm]

Originally posted by azamkita
Thanks to Nuuk,Andy,Carlos for your answer,
I'll take note - thanks
BTW, any possibilities if I parallel 7818/1918 or I parallel LM317/337 to increase the current let say to 5 amp or 7 amp ?.
Come back to transformer part, should I reduce the secondary or increase the primary ?
Give me some lite plzzz.
thanks and have a nice day.

Don't fiddle with those regulators, it won't work properly.
A CT trafo like yours has two wires joined on the secondary, you just have to separate them.
To do that, cut a little of the tape isolation where the wires of the secondary leave the trafo.
You'll see that the center wire is soldered to two solid core wires of the trafo.
Separate them, solder two wires and isolate them with tape.
That's it, independent secondaries.
With your trafo you'll be able to regulate at around 22~23 volts, not that bad.

[arniel]

You can increase the output of an LM317/LM337 by paralleling regulators etc. There are some examples in the data sheet.
I am looking at the same idea as I have a whole bunch of LM317s to use up...

Arnie