power supply wiring

[Richidoo]

How do I wire 1 transformer to otherwise dual mono power supply, with each channel having dual bridge rectifiers? Found plenty of monoblock PSUs with dual bridges, but no stereo PSUs. Do I just parallel the secondaries to each channel?

One more: PS grounds (from rectifiers) and mains earth both connect to chassis? Should they be together as star ground or doesn't matter?

Thanks a lot!
Rich

[01001101]

Hi,

maybe this will help you:
http://sound.westhost.com/project04.htm

The PSU ground to mains earth connection through a so-called loop-breaker is also discussed. It can also be connected directly but may cause ground loops. This is discussed in an article on the same page.

Of course mains earth must always be connected directly to chassis.

[AndrewT]

Hi,

Originally posted by Richidoo
Do I just parallel the secondaries to each channel?

yes, take a pair of AC wires from each winding to each rectifier. Keep the LOOP AREA small i.e. short and twisted.

PS grounds (from rectifiers) and mains earth both connect to chassis? Should they be together as star ground or doesn't matter?

no, not to chassis.
Take the PSU 0volt (connect the two 0v from each rectifier together with a twisted pair then a single connection) to
the audio ground where they meet
the PCB power ground,
the PCB signal ground,
the speaker return, and
the link ready for chassis connection.

The order of bolting together all these returns is important. Do not sandwich the signal gnd between two dirty returns. I use dirtiest to cleanest i.e. disconnecting network-PSU 0v-PCB power gnd-speaker return-signal gnd-optional RCA gnd.
The RCA gnd can go to PCB signal ground via the screen or direct to the audio ground via a separate wire (choose which is quieter with your sources). The RCAs (just like XLRs) must be isolated from chassis.

Each channel can have it's own audio ground and both audio grounds then connect to safety earth via their own disconnecting networks.
Or if the layout suits you can have one shared audio ground (keeping the dirty to clean order) with one disconnecting network. (this MAY have slightly degenerated crosstalk).

The disconnecting network can consist of the parallel connection of some or all of the following:
Power resistor,
Power diode Bridge connected in inverse parallel,
Power Thermistor,
high frequency capacitor.

Originally posted by 01001101
The PSU ground to mains earth connection through a so-called loop-breaker (disconnecting network) is also discussed. It can also be connected directly but WILL cause ground loops AND HUM.

Of course mains earth must always be connected directly to chassis.

yes, the mains safety earth MUST ALWAYS be connected PERMANENTLY to exposed conductive parts. Even DURING maintenance when power may be switched back on to test some modification/repair/etc.

[Richidoo]

Originally posted by 01001101
maybe this will help you:
http://sound.westhost.com/project04.htm

I saw that schema from Rod (thanks 01), but it shows only single rectifier per channel, I will use dual bridges per channel, like this monoblock PS: TNT Audio PSU. Can I just split the secondary outputs to go to each channel?

Andrew, thanks for another total overload. I learn a lot when I take the time to research and figure out what the hell you are talking about... Grounding, a whole science in itself.
Thanks
Rich

[AndrewT]

Hi Rich,
I have to read some papers two, three, even four times for some stuff to sink in.
Occassionally a remark with different phraseology suddenly allows the penny to drop.

[FastEddy]

here is what I did:

http://3dotaudio.com/ampics.html ... note two PSU boards, each has diode bridge & plenty of caps.

Note also that all boards are completely isolated from chassis ground, chassis ground (all shielding) being connected to the power cord, only. Audio ground(s) are connected at each amp board (at a single point) and that is connected to PSU ground(s) on power boards thru the power rail connector leads. Sounds just fine = 2 channels, 160 Watts >> 8 ohms, flat 10to 25k ... :>)

( PSU boards and amp modules from http://aussieamplifiers.com )