The (high-cap.) unregulated PSU for chipamps

[Nuuk]

Just make a small break a go see a Chelsea match, ok?

I wish that I could afford to Carlos! 😉 (And please look after our players a bit more carefully 🙄 )

But I have enough to keep me busy. Here is the pre amp/active crossover module (just completed)

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

Now to finish the speakers and make up some interconnects/speaker cables (oh yes, and that second GC!).

 

[Russ White]

Wow! Nice Nuuk! I like the wood.

I am also building a couple of preamps, one for my office and one for the GC I made for my nephew's birday. I hope they turn out half as nice as your looks. 🙂

I used TI RC4560s for the opamps on one and TI/BB OPA627s on the other both have BUF634s in the feedback loop. So far the only one working is the RC4560 version, and I have to say I love it, though I cannot say I have had a lot to compare it to. 😀

Anyway, thanks for you inspiration!!

 

[Nuuk]

Thanks Russ. I will post more details when the project is completed but in the Loudspeakers section as I don't want to hijack this interesting thread on snubbers. 😉

CFC won - nearly there CFM. 😎

 

[GregGC]

Another update regarding High Cap PS.

Just doubled the PS capacitance again. I have 1000uF/low ESR +3300uf + snubbers per rail/per channel. Wow, what a difference from 2000uf to 4300uf. GC sounds effortless and the sound stage became much larger. I get the feeling that the highs are better too. I purposely didn't use only low ESR caps after reading some articles on PS output impedance.
Manny times better than the classic GC with 1000uF.

Greg

 

[carlosfm]

Wow, what a difference from 2000uf to 4300uf.

I am using on my main system a snubberized PSU with 3x4,700uf per rail.
The diodes are MBR16100 (schottky), heatsinked.

 

[carlosfm]

But I have enough to keep me busy.

Take another one:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=54697

😀

 

[GregGC]

I am using on my main system a snubberized PSU with 3x4,700uf per rail.
The diodes are MBR16100 (schottky), heatsinked.

I may squeeze one more cap in.... 🙂

Next thing for me to try is the diodes. Same as the snubbers I'm not 100% convinced that it'll make a diff. in the sound. Hey, the snubbers were nice surprise! Looking forward to the next one.

Greg

 

[slackman]

Caps on GC Board

subjected to http://www.diyaudio.com/forums/showthread.php?postid=609113#post609113
in this thread (sorry...)

Am i right that i should remove the 1500uF Caps on the amp-boards and solder the snubbers and bypass Caps instead?😕
I'm using the lm4780 boards from Peter (parallel-mode, dual mono)

(Think the 1500 uF caps on the amp-boards wouldn't do any sense if there are some 10.000uF-caps in the power-supply...)

By the way: has anyone a good compromise between voltage and power consumption for lm4780-boards? I didn't ordered the toroids...
I would take two 330VA types, 2x30V.
(Speaker-Impedance falls to a minimum of 6 R )

Michael

 

[Nuuk]

Am i right that i should remove the 1500uF Caps on the amp-boards and solder the snubbers and bypass Caps instead?

Yes, but replace them with 100uF caps. The chip must have some capacitance right on the pins.

Also check out the revised snubbered PSU elsewhere in the Chipamp section of this forum.

I would suggest 25 VAC transformers, not 30 VAC!

 

[peranders]

I would suggest 25 VAC transformers, not 30 VAC!

2 x 28 VAC is max! 30 VAC is on the edge of what the poor LM's may withstand.

 

[GregGC]

I kept my 1000uF/low ESR caps untouched. I just added the snubbers to them. I added extra 3300uf/rail/amp close to the amp PCB. I'm sure depending on your configuration you may find different variations to work too.

Also, last night I tried L||R network in ser. with the output. The res is 10 ohms/1W and I put 8 turns of wire (24AWG from a network cable) on top of it. My GC is even more civilized now. So I do recommend using it. It protects from instability in the HF range much better that the 0.2 res no matter the type of speakers. Also it allows me to go higher with the FB resistors for better DC offset (I'm using 4.7k/100k) without ill effects.
I highly recommend using the L||R with high cap PSU together with the Zobel network.

Greg

 

[slackman]

Hi there,
following this thread i'm looking for a simple inrush current limitation for toroids. In the beginning of this thread there's a link:
http://www.tnt-audio.com/clinica/ssps1_e.html in which the psu is developed step by step...
I tried to scale the pictures - but no way... i can't read (encrypt is better) the values of the inrush current protection...

I've lots of special schematics but i want to make it simple (i.e. without relays).
On Carlos' pics (photos) there's always a tiny small solution: PLEEEAZE - could you drop a schematic and give a small comment?

Thanks so far...

BTW how high is the gain of your lineloop module, Carlos? Is 3.5 too much?

(Next days the rest of the preamp parts will arrive - sigh!🙂)

Michael

 

[carlosfm]

Hi there,
following this thread i'm looking for a simple inrush current limitation for toroids...

I've lots of special schematics but i want to make it simple (i.e. without relays).
On Carlos' pics (photos) there's always a tiny small solution: PLEEEAZE - could you drop a schematic and give a small comment?

One 4.7R / 5~10W resistor in series with each primary.
That means two resistors.

Thanks so far...

You're welcome.

BTW how high is the gain of your lineloop module, Carlos? Is 3.5 too much?

You mean the preamp?
I use 3x, and on the power amp(s) 21~22x.
This is enough for me, and quite "standard". And my speakers are not very sensitive.
You can use 3.5x, but in my oppinion that's a little high.
2.5~3x is the spot, for me.

 

[Upupa Epops]

To slackman : If you will have connected serial resistor permanently in series with primary winding, inrush current will be OK, but PS will be much more " soft " and total " die " dynamic of reproduction.

 

[jackinnj]

Hi there,
following this thread i'm looking for a simple inrush current limitation for toroids. In the beginning of this thread there's a link:
http://www.tnt-audio.com/clinica/ssps1_e.html in which the psu is developed step by step...
I tried to scale the pictures - but no way... i can't read (encrypt is better) the values of the inrush current protection...

I've lots of special schematics but i want to make it simple (i.e. without relays).

You can use a Thermometrics Inrush Current Limiter -- when the current heats the element the resistance goes down. The CL-30 has an initial resistance of 2.5 ohms, this drops to 0.09 ohms when the load is 6 amps. You should be able to find the PDF on the web. Digikey carries them.

The relay soft-start works very well (although you express a preference against this route) -- Sorensen uses them in their high voltage laboratory supplies -- the ESP Circuit does not allow for the MOSFET to be discharged, however.

ST Micro also makes a switchable diode -- OK if you like half-wave rectification, not so great for linear supplies.

 

[slackman]

Well,
i see that i have to implement the 'project39' inrush limiter with relays which bypass the powerresistors after powerup...

The schematic is very simple so that there's no need of making special pcbs and a small 9v trafo i still have...

First of all i'll finish the pre.

Michael

 

[chris ma]

4 different PSU

I hope this 4 unregulated supply for the 3875TF should all sound the same..
Top to bottom

1/ CRCLC
2/ CLC
3/ C choke C
4/ CRC

The first C is 400V 680uf
The last C is 2 X 4700uf

The Butcher😀

 

[chris ma]

closer look at the choke.

 

[chris ma]

The other CRCLC

 

[XELB]

CarlosFM, using the resistor R3/R4 and capacitor C7/C8 you will get high frequencys. Am I correct ?

2 x 28 VAC is max! 30 VAC is on the edge of what the poor LM's may withstand.

I have a friend that uses LM's with 2 x 30 VAC .
He uses nice heatsinks and the chip plays very well hot