2-channel parallel 100W GC using LM3886

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Thanks a lot for the reply guys!

OK, I do realise that putting a regulator is probably the best idea.
Yet still, do you think that the regulated supply compared to an unregulated supply with enough caps (so that the amp can pull as much as it needs ) has a realistic advantage? (not to mention the additional price of the regulator)

Unfortunately, I haven't found any regulators in my recent dumpster dives :D
 
SheldonD said:
was waiting for someone else to respond, so here goes:
if you regulate use much smaller caps on the chips, say 100ufd or less with .1 bypass poly. The large caps will muddy the treble and mids. whether BG are worth it in this position is unclear.

This has been gone over many times, read Carlosfm threads
on regulated supply.

The larger caps immediately adjacent to the LM3886, 3875, 4780 provide a storage facility for the amplifier unburdened by the R*I^2 losses of PCB traces or connections to the power supply. They and the other caps which Nat Semi specifies are also important for dealing with the thermal protection which can oscillate under certain conditions.

I think that the entire idea of minimal capping has been debunked by this point.
 
regulated or not..........

hi,
you loose a bit of instantaneous dynamic range using a regulated p.s. you will have
to pump out about 7Amp peak for 100W per channel @ 4 ohms load so 2ch is 14Amp peak current, but if the humming noise is a problem may be this can be a solution.
scone, where did you get the enclosure for the amp, it looks nice.
best regards
Williams
 
So, if I got this right, you are saying that the dynamic range is a bit bigger with a standard PSU because the amp can drain more current from the caps than from the regulator?

What is the advantage of using regulators over standard supplies in these amps anyway?
 
Hi,
Some amps may need regulated supplies.National says , that LMs doesn't.Some claim that it sounds better with regulated PSUs.I have had no chance to compare.
Most of hums and other problems with IC amps come from incorrect grounding , not supply regulation.If wired correctly , LM3866 must be totally quet without any regulation.

Regards,
Lukas.
 
regulated or not

hi 'lead',
i think the explanation didn't hit the right target, a regulated p.s.
can't deliver big amounts of current instantaneously, that is why
dynamic range will be lower, a good unregulated p.s. will do it!
depended on the size of trafo, rectifier diodes and size of output capa.
if no problems with hums noise build unregulated for pwr amps just keep all wires as short could be; specially the gnd and +-vcc.
best regards
Williams
 
Thanks a lot for the response!

I just read my post again and realized that I messed up the sentence a bit :( I meant the same thing you wrote, I just wrote it the wrong way... Well, the important thing is that I understand what you are saying...

Anyway, how big should the caps be?

Thanks a lot guys,
Lead
 
Lead said:
So, if I got this right, you are saying that the dynamic range is a bit bigger with a standard PSU because the amp can drain more current from the caps than from the regulator?

What is the advantage of using regulators over standard supplies in these amps anyway?

Look at it this way, a linearly regulated power supply burns off the peaks of the ripple so that energy is dissipated as heat.

A switching power supply adjusts the duty cycle (on time %) for changes in current or voltage --

Both linear and switching regulated supplies have a control loop that feeds an error signal into regulating chip -- the design of the control loop gets a bit tricky -- if it is overdamped the supply won't oscillate (bad) , but neither will it quickly respond in changes at the output. If the loop is incorrectly compensated the regulator will break into oscillation.

Some of the Pass Designs needed regulated power supplies
 
The regulator does not need to quickly respond to changes in output. It merely needs to be fast enough that the downstream caps aren't drained beyond an acceptable level. That much it can do. Dynamic range is BETTER with a regulator than without. Without, the voltage fluctuates (drops) by at least a couple volts, more than with the regulator. That doesn't necessarily mean anyone will like the resultant sound more one way or the other.

The key is to ignore those who suggest a GC only needs 100uF on the chipamp board.
 
I hate to bring back old threads out of the blue like this, but I really want to build alexw88's PA100 x2 as found on his site.

I figured I would ask here about a few things.
1) I am wondering if it is possible to get the pcb files for both the power supply and the amp. I know I have the schematics for both, and can probably make it up myself on Eagle, but I figured the boards that are already in use would be better than something I calc'd myself. (or let eagle figure out...)

2)I am new to amplifier diy and have no clue what transformer I need. I can see it in the pictures but I don't know where to buy one. Could I get some assistance with that? The schematic shows 220VAC to 25VAC. I was also wondering if I could get 120 to 25, as I am currently not able to easily get 220. If it is just completly necessary to have 220VAC though, I can cope.

3) Where can I get a case like the one in the pictures? The polished metal look is really nice, and I would like to get that for mine.

Sorry if I seem real needy, but I really like the looks and quality data I saw on the website. I also enjoyed the "reviews" posted on these forums about alexw88's work.


Regards,
Jared
 
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