Chip amp power supply- a beginners guide

[pirej]

Finally find probably one godd schematic for regulated power supply that will fit my trafo 32-0-32v / 5A to use for LM 3886 amps.

The transistors will be MJ2955/2N3055.

Any suggestion?

[AndrewT]

Originally posted by pirej
I'm trying to get 35v regulated as max. for stereo LM 3886.

The above schematic is OK with my trafo 32-0-32v?

depending on tolerances and actual mains supply voltages you may get a regulated +-35Vdc from a 32Vac.
But, you may suffer from occasional drop outs in the regulators when high current demand coincides with low supply voltage. This could be so rare that it effectively never happens during normal operational conditions.

If you find that drop outs are occurring then reducing the output voltage by a volt or two may cure the problem.

Where are the rectifiers?

[pirej]

THNX Andrew and all...

Sorry, but I was impressed with GC with my Canton CT 920DC. Previously I had a technics SU-V-670 and was trying to hear some parts of any music composition...

That was real reason to use two other trafos 32-0-32v to make another for my colleagues...

Rectifies were not drawn...Just the trafo..

Thnx...

[pinkfloyd4ever]

Hi Nuuk, a couple of questions...

1) For the ground loop breaker circuit, which of these bridge rectifiers should I use?
2) You say "Place a small Class X1 rated capacitor (around 0.1 uF /275 volts is fine) across the switch contacts. "... how does that not short the switch given that we're switching AC (which a cap does not block, correct?)
3) Is this switch ok for the light bulb tester?
4) I'm a little confused about the "zero volt line"..the diagram on your site shows it connected to an I/O jack. Is that the ground of the jack it's connected to? would that be the same thing as signal ground? And how would I do a loop breaker with a dual mono gainclone? (I plan to put both channels of the amp and PSU all in one case) Wouldn't connecting the zero volt line to both power supplies (and both channels' I/O jacks) defeat the purpose of dual mono? I know dual mono requires 2 transformers and 2 rectifier bridges, but will it also require 2 IEC sockets & power cords?

[AndrewT]

Hi,
you can't do dual mono in a single box.
You can fit two monoblocks in a single box, but the grounding has to be done to allow two channel working. This is usually a compromise for all multichannel amplifiers. However, it can be made to succeed, but don't ask me, because I have never been able to build a two channel amplifier as quiet as a monoblock, ever. Similarly, I have never been able to build a steel cased amplifier as quiet as an uncased amplifier.

Calculate the impedance of your 100nF capacitor at 50 & 60Hz.
Now, calculate the AC current that will flow through that impedance at your main's supply voltage. This is ~ the current that flows when the switch is open.
If you fit Y rated caps on the lines to ground, do the same calculation for 10nF. This will give the Earth Leakage current. In the UK this Earth Leakage current must not exceed 25% of the trigger rating of the RCCB protected circuit. i.e. the total Earth Leakage current of all the appliances on a 30mA RCCB circuit must not exceed 7.5mA. That's why I have 5 RCCBs supplying my house and why I do not have an RCCB feeding my listening lounge.

If you don't know how and where to fit a switch on your light Bulb Tester then don't fit one.
The Bulb Tester works perfectly without a switch.
on=amp wiring fault,
off=possibly OK and allows you to check/measure operating voltages.

[pinkfloyd4ever]

Originally posted by AndrewT
Hi,
you can't do dual mono in a single box.
You can fit two monoblocks in a single box, but the grounding has to be done to allow two channel working. This is usually a compromise for all multichannel amplifiers.

ahhh crap...looks like I'll be going with stereo for now then

Originally posted by AndrewT
Similarly, I have never been able to build a steel cased amplifier as quiet as an uncased amplifier.

hmm really? interesting

Originally posted by AndrewT
Calculate the impedance of your 100nF capacitor at 50 & 60Hz.

erm..how? I do know V=IR to find the current once I get the impedance though. Whatever that current is, I guess it means the amp will consume that when it's turned off, right?

Originally posted by AndrewT
If you fit Y rated caps on the lines to ground, do the same calculation for 10nF. This will give the Earth Leakage current. In the UK this Earth Leakage current must not exceed 25% of the trigger rating of the RCCB protected circuit. i.e. the total Earth Leakage current of all the appliances on a 30mA RCCB circuit must not exceed 7.5mA. That's why I have 5 RCCBs supplying my house and why I do not have an RCCB feeding my listening lounge.

huh? what's an RCCB?

Originally posted by AndrewT
If you don't know how and where to fit a switch on your light Bulb Tester then don't fit one.
The Bulb Tester works perfectly without a switch.
on=amp wiring fault,
off=possibly OK and allows you to check/measure operating voltages.

I know where the switch goes, I just wanted to know if the one I linked to is the right type & ratings

[Redshift187]

Originally posted by pinkfloyd4ever
what's an RCCB?

Residual current circuit breaker. AKA ground fault circuit interrupter (GFCI), ground fault interrupter (GFI) or an appliance leakage current interrupter (ALCI).

It detects if the current on the live is different than the current on the neutral (which happens when some is going to safety earth) and disconnects the power.

[pinkfloyd4ever]

Originally posted by Redshift187
Residual current circuit breaker. AKA ground fault circuit interrupter (GFCI), ground fault interrupter (GFI) or an appliance leakage current interrupter (ALCI).

It detects if the current on the live is different than the current on the neutral (which happens when some is going to safety earth) and disconnects the power.

Ahhhh ok, I know what a GFCI is...damn acronomical (<-even a word?) differences between countries

[AndrewT]

F=1 / 2 / Pi / C / R rearranged becomes
R=1 / 2 / Pi / C/ F.
For 60Hz and 100nF, R=26k5
Current when across 120Vac = 4.5mA.

That same 100nF across the UK voltage of 240Vac 50Hz passes 7.5mA and this is our limit for the total Earth Leakage of a 30mA RCCB circuit.

[pinkfloyd4ever]

ahhhhhh I get it all now...fortunately I don't have to worry about it since my circuit sure as hell isn't on a rccb/gfci. I live in an old house and we only have those in (some of) the bathrooms. And 4.5mA is nothing as far as 'wasting' unused elecrticity. Thanks Andrew


wait, I thought from the pic on Nuuk's site that it was a ceramic disc cap?? What type of a cap am I looking for? Mouser only had 4 different 0.1uF ceramic disc caps with high enough voltage ratings, and they didn't seem to be what Nuuk was describing... http://www.mouser.com/Search/Refine....572368+1323043

or one of these? http://www.mouser.com/Search/Refine....ltage+Rating|0