Center tap wiring

[tom wesley]

Hi folks this is my first post so please bear with me. Im going round in circles with the ct wiring. I know that everything is working as ive got 22vdc on the boards v+ / v- connecting the ct to PG just for testing rectifier. Below is a pic of my rectifier board (not all outputs soldered yet) to help with any answers.
As you can see the board has 3 jumpers (one solid bad to see) and both caps in place does this mean:

1 i should connect CT to the rectifier, Or AMP board at OP gnd.

2 If connecting to amp board do i split CT to both boards?

3 Could i take it directly to Chassis and take wires to each CH GND on amps (this seems right)

4 Due to using 3 jumpers as pg15 of audiosector guide suggests on rectifier and both caps do i have to join all PG- / PG+ to amps



I know theres alot of threads on this but it would be great if some one could draw or simply explain the options as just when i think eureka i see another way on here or elsewhere. Im getting conflicting views and think im over complicating things possibly. Thankyou in advance Tom

 

[Redshift187]

I switched to a centre-tap because I had one lying around of a higher voltage and wanted to try it. I have the same PSU board. My amp is in a separate enclosure from my PSU. My star ground in the PSU is where the safety earth is attached to the chassis. So I have the CT connected to the star ground, and the PG connected to the star ground too. Since you have the jumpers, you are correct in that PG- and PG+ are already connected to each other and you only need to run one ground wire to the amp boards.

I don't know what the Peter Daniels amp boards are wired like, make sure PG- and PG+ are connected on the amp or add the appropriate jumpers.

 

[bob91343]

The important thing is the current path for the ripple, through the filter capacitors. In other words, the center tap needs to go straight to the capacitor; otherwise, ripple currents will flow in circuit traces and inject hum into the system. All other connections should go to the capacitor, which should be the common point.

 

[Sangram]

We only ever use CT transformers here. As bob ^^^ says, the CT is the power ground for the power supply and should be connected to the midpoint of the caps directly so the supply caps can bleed ripple directly back to the power transformer. It is a good idea to directly connect the loudspeaker return here (not the board's output ground) as well, and use a short length of wire to run to signal ground (not using the exact same point as the speaker return), this separates the currents in the low-power and high-power circuits in the amplifier.

For chassis ground, run a separate wire from the CT/capacitor junction.

IINM the power capacitors in the Audiosector kit is directly on the amp PCB. In this case, join the amp board's PG+ and PG- placeholders with a thick wire (16AWG) and solder the CT right there. Also the little caps on the rectifier board will not work without a ground connection, so you may route a wire back to the rectifier board. Remember the highest currents flow through the power supply reservoir caps and the speaker return lead, so it is essential to keep those ground connections away from the low-level signal leads. The Audiosector LM4780 PCB which I use already has this arrangement by default, though for that specific amp I used to have a regular transformer with split secondaries.

Good Luck