The (high-cap.) unregulated PSU for chipamps

[moamps]

Originally posted by SheldonD
....If you consider these 30 volt rails are feeding a 60 watt
amplifier then 1 Amp is on both rails.
This would require 1 watt= 1 ampx1ampx 1R...

Hi,
You are wrong, sorry.

If P=60W
and Z=8ohms
then
I= 2,74A
P(R3)=R3*I*I=7,5W!!!!!

With 3W resistors, the PS is limited to 1.7A continous
which translates into 23W at 8 ohms and 12W at 4 ohms from amp(s), under ideal conditions.


Peranders,
LM3875 isn't rated at 23W/8ohms average.

CarlosFM,
The number and overall capacitance of elcos in your PS doesn't change power consumption from the mains. Otherwise, you would have perpetuum mobile.

Regards,
Milan

[homer09]

some times people have too much blind faith in calculations...

isnt the purpose of a formula and calculation to predict/explain/understand/model an observed phennomenon? if carlos says that when he uses his amp with 3W res it doesnt get hot, then it doesnt get hot, period. no matter what your calculations tell you, they cannot be MORE true than REAL life now can they?

you would of course be perfectly right if we lived on paper...

[carlosfm]

Originally posted by moamps
CarlosFM,
The number and overall capacitance of elcos in your PS doesn't change power consumption from the mains. Otherwise, you would have perpetuum mobile.

Regards,
Milan

I know, I didn't say that.

Although it works fine and runs cool, is it really necessary to change the schematic for 10W resistors?
Ok, I'll do it, just for peace of mind, and this way one PSU can feed more chips.
I'll also put 1W resistors for the snubbers, as it's what I've been using lately.
Hold on...

[carlosfm]

Here it is.
I hope everyone is happy now.

[regal]

Still don't understand the T1 & T2. Is this really a single transformer with dual secondaries?

[carlosfm]

Originally posted by regal
Still don't understand the T1 & T2. Is this really a single transformer with dual secondaries?

Yes.
Because the software didn't have the symbol, I had to put two trafos.
For the purpose, it's the same.
You can use two trafos, or one with dual independent secondaries.
You can even use a CT trafo with this PSU, with 4 diodes or a single diode bridge.

[MikeLewis]

Carlos,
Just curious, pertaining to my post on the LM338 regulated thread about a multi-amped system, you reccomended a unregged PSU. Having read this thread (and feeling the wrath of 50 pages of information overload), I was wondering how component values would scale as the traffo's VA was increased. I think I have a few ideas, but I'm very very new to the scene and would really like to hear your opinions about it. As far as I can see, you would only need to increase the supply caps (and possibly power dissipation in resistors), but I don't feel I have a solid grasp on what would be their actual values.
Sorry for the Qs, but I don't really have spare parts to work with, so I'd like to get a design well-laid out before I start ordering and demolish my next paycheck. Thanks.

[peranders]

Originally posted by carlosfm
Here it is.
I hope everyone is happy now.

Carlos, if your design goal is continuous output power at max, you should also use appropiate resistor values and if those are chosen for music then lower values are OK.

Carlos , if you want people to really understand your ideas I think some explanations are needed along with your schematics

[peranders]

Originally posted by carlosfm
Because the software didn't have the symbol, I had to put two trafos.

Can't you edit your cad symbols How do you do when you want some part you don't have?

[carlosfm]

Originally posted by MikeLewis
Carlos,
Just curious, pertaining to my post on the LM338 regulated thread about a multi-amped system, you reccomended a unregged PSU. Having read this thread (and feeling the wrath of 50 pages of information overload), I was wondering how component values would scale as the traffo's VA was increased. I think I have a few ideas, but I'm very very new to the scene and would really like to hear your opinions about it. As far as I can see, you would only need to increase the supply caps (and possibly power dissipation in resistors), but I don't feel I have a solid grasp on what would be their actual values.
Sorry for the Qs, but I don't really have spare parts to work with, so I'd like to get a design well-laid out before I start ordering and demolish my next paycheck. Thanks.

This PSU can cope with 3 chips, as I suggested you.
30,000~40,000uf capacitance after the series resistors is what I would use.
For the trafos, 400VA is fine.