LM338 regulated snubberized PSU for audio amplifiers

[carlmart]

It can make 30ºC at night here.

You call that hot? That's what we have in Rio in Autumm and Spring! That's cool for us.



Carlos

 

[Cortez]

Don`t think my Epos needs paralell chips with a minimum impedance of 7,2 ohm

If i'am right, higher output current is needed not just because low
speaker impedances, but cause of reactive loading (eg crossover).

 

[Tor M]

Oh... that's not good.
Hope you get better soon.

That makes us two!! Actually a little better today

If i'am right, higher output current is needed not just because low
speaker impedances, but cause of reactive loading (eg crossover).

My Epos has a minimal crossover consisting of just a capasitor for the tweeter. Thats probably what makes them kind of hard to drive.
Thats also why I have high hopes for biamping this speaker!!

Tor Martin

 

[derekyu]

would someone offer this psu pcb for subscription?

 

[carlosfm]

would someone offer this psu pcb for subscription?

Subscription?
That's new...

 

[peranders]

Carlos, this man used the wrong word, I'll suspect. I think he ment "for sale". He want to buy your product.

 

[carlosfm]

Carlos, this man used the wrong word, I'll suspect. I think he ment "for sale". He want to buy your product.

I understood, just found it curious.
My schematics are shared for the diyer to use and to build freely.
Now it seems that everything has to go to 'goup buys' (which is sometimes a fancy way to call it), and that gets a little annoying.
Guys, pick on the tools, the parts and the soldering iron and build it yourselves, you will learn in the process.
There's kits flowing around, but THIS is pure diy.

A lesson that I learned long time ago: if you wanna do it your way, you have to do it yourself.

 

[derekyu]

carlos,
i am so sooory to annoy you.
But you know your pcb is so nice and like an art, so I asked whether i would make a collection for this great art.....

 

[mateo88]

So has anyone tried an lm1084 in place of the lm338? It looks to be much better (and cheaper) than the lm338, though I haven't seen any impedance graphs for it.

 

[jackinnj]

Do you mean LT1084 ? -- this is a low dropout adjustable regulator -- they are a bit finicky when it comes to output capacitor specification.

 

[Tor M]

Hi!

So I modified my speakers for biamping this evening.

Biamping seems to be a great improvement. Especially the treble seems to be much more dynamic and detailed. This increases the size and depth of the soundstage. There is also an improvement through all the midrange.
Can`t hear so much improvement in the bass region, where I actually expected to hear the most difference.

I have been a couple of beers tonight , so I have to confirm my listening impressions tomorrow. But so far this seems to be the best my system has ever sounded.

Hope you all have a nice weekend!

Tor Martin

 

[planet10]

o I modified my speakers for biamping this evening.

Passive or active bi-amp?

dave

 

[derekyu]

I cannot find the LM 388 in TO220 in the city but only in TO3.

Some suggust me LT1084 or LM 337.

Can they replace LM 388? many THANKS

 

[Tor M]

Passive or active bi-amp?

dave

Hi!

My speakers is the old Epos Es14. The only crossover in this speaker is a 2,2 uF cap for the tweeter.
So it`s passive bi-amping, but with no more passive parts than you would need for active bi-amping with a "normal" speaker.
This is kind of cool, since you don`t need all that extra electronics.

Tor Martin

 

[planet10]

The only crossover in this speaker is a 2,2 uF cap for the tweeter.
So it`s passive bi-amping, but with no more passive parts than you would need for active bi-amping with a "normal" speaker.

You might want to consider putting the cap on the input of the tweeter amp. You'd be working that amp less, and it would see a less reactive load.

Plus since a cap on the input is going to be much smaller you can get a really good one.

dave

 

[BWRX]

I cannot find the LM 388 in TO220 in the city but only in TO3.

Some suggust me LT1084 or LM 337.

Can they replace LM 388? many THANKS

You mean LM338. Yes, the LT1084 can be a drop-in replacement for the 338. I like the Linear Tech regulators better but often use the National ones because they're cheaper.

 

[jackinnj]

You mean LM338. Yes, the LT1084 can be a drop-in replacement for the 338. I like the Linear Tech regulators better but often use the National ones because they're cheaper.

Not quite, the output capacitor of a Low Dropout Regulator like the LT1084 is part of the compensation network -- pick the wrong capacitor and it will oscillate.

 

[Tor M]

You might want to consider putting the cap on the input of the tweeter amp. You'd be working that amp less, and it would see a less reactive load.

Plus since a cap on the input is going to be much smaller you can get a really good one.

dave

Yes, that would probably be a better solution. But I`m a little worried about having the tweeter unprotected against dc. As far as I know, you don`t get replacements parts for theese old Epos speakers anymore, so if something should happen with the elements I have to start searching for new pair of used speakers.
Thoose speakers are kind of rare in the second hand market...

Thanks for the advice.

Tor Martin

 

[BWRX]

Not quite, the output capacitor of a Low Dropout Regulator like the LT1084 is part of the compensation network -- pick the wrong capacitor and it will oscillate.

Yes that is very true. Thanks for pointing that out. I just assumed that he'd be using an adequate valued electrolytic on the output. The datasheet for the LT1084 suggests using a minimum of 22uF solid tant. or 150uF aluminum on the output to ensure stability under all operating conditions.

 

[tobias_svensk]

Did a layout for this PSU, what do you think?

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

Austerlitz KS35.4-51E: 9 °C/W @ 5 W , would that be enough hm..

Cheers