AKSA power mains wiring

hifryer · « **on:** 26 Jan 2006, 06:36 am »

Any comment on whether it is better to wire up the two AKSA transformers in phase of out of phase to the AC mains supply?

Thanks

andyr · « **Reply #1 on:** 26 Jan 2006, 07:04 am »

Quote from: hifryer

Any comment on whether it is better to wire up the two AKSA transformers in-phase of out-of-phase with the AC mains supply?

Thanks

Hi, fryer

You should read this article:
www.boundforsound.com/tweak.htm

Which is better, really depends how your house is wired ... so what I do now is to use a DPDT 10a power switch, with the power transformer input leads connected to the central tags on the switch. One of the outer pairs of tags on the switch has the Active and Neutral mains wires (from the IEC socket); the other has these reversed.

So with the switch in the "down" position I get , if you like, "in-phase" and with the power switch "up", I get "out-of-phase".

You need to do the measurements according to the instructions in the article and then use the switch in either the "down" position or the "up" position from then on - depending which way gives you the lowest earth voltage difference.

It WILL sound better, one way around.

Regards,

Andy

Geoff-AU · « **Reply #2 on:** 26 Jan 2006, 07:53 am »

Quote

POINT 2. Power amplifiers are generally immune to the workings of outboard line conditioners, but respond very favorably to power cords.

LOL

Quote

You plug the Marigo into the wall, but you don’t have to plug anything into the Marigo. Once the Marigo is in the circuit, it acts like a grunge magnet that attracts AC line garbage and filters it out through the circuit.

LOL.

Quote

POINT 6. Power cords make a tremendous difference.

ahahahahahahahahahaha....

thanks, I needed a good chuckle

hifryer · « **Reply #3 on:** 26 Jan 2006, 12:46 pm »

Andyr

Sorry my question was a bit amgibuous.

I didnt mean phase in relation to mains active and neutral. I meant phase in relation to each other. I assume if everything is wired OK neutral is neutral. To reverse switch this could be quite dangerous as it could leave your amp live whilst apparently switched off!

Since a big cap re-charging time is usually only a small fraction of a cycle, I thought it might help to stagger the current pull from each channel a halfwave ( 10ms) apart.

Cheers

Greg Erskine · « **Reply #4 on:** 26 Jan 2006, 01:28 pm »

Quote from: hifryer

Since a big cap re-charging time is usually only a small fraction of a cycle, I thought it might help to stagger the current pull from each channel a halfwave ( 10ms) apart.

I think once the AC goes through the rectifier the signal is identical because you can't distinguish positive part from the inverted negative part. If you have access to 3 phase then you could use 2 phases and have the pulses out of phase.

regards
Greg

hifryer · « **Reply #5 on:** 26 Jan 2006, 08:03 pm »

Greg,

You are correct but aren't you pulling the current out of the mains at slightly different times? i.e. possibly better supply to the primary?

hifryer · « **Reply #6 on:** 26 Jan 2006, 08:07 pm »

Greg,

OK, find it hard to get my head round. But think you are right - full wave, both use both halves of all waves so no effect. Need different mains phase supply as you suggested.

andyr · « **Reply #7 on:** 26 Jan 2006, 09:05 pm »

Quote from: hifryer

... I assume if everything is wired OK neutral is neutral. To reverse switch this could be quite dangerous as it could leave your amp live whilst apparently switched off! ...Cheers

Yes, if you simply reverse the plug in the wall (which some US folk do) that's dangerous ... but NO neutral is not neutral! And that's not what you're doing if you use the "old DPDT trick" (with due reference to Maxwell Smart!

).

The IEC socket is correctly wired, the fuse is on the 'Active' side - as required for safety - but, after that, the transformer doesn't care which way round the mains is! However, flipping the input leads of the transformer DOES produce a difference - all will be explained in that BoundforSound article.

Because of this difference, I believe it's better for both transformers to be connected the same way.

Regards,

Andy

hifryer · « **Reply #8 on:** 27 Jan 2006, 01:13 am »

Andy,

I may try what you suggest with a 3 position, double pole, double throw, on/off switch, wired to disconnect both ( middle pos) and swap both ( top / bottom pos's) active and neutral.

Just as well I have a LED to indicate when amp is on!

Thanks for the idea. Will report back later - have open mind but currently skeptical ;-(

cheers

andyr · « **Reply #9 on:** 27 Jan 2006, 02:11 am »

Quote from: hifryer

Andy,

I may try what you suggest with a 3 position, double pole, double throw, on/off switch, wired to disconnect both ( middle pos) and swap both ( top / bottom pos's) active and neutral.

Just as well I have a LED to indicate when amp is on!

Thanks for the idea. Will report back later - have open mind but currently skeptical ;-(

cheers

Yes, I wuz skeptical too ... until I followed the procedure in the BoundforSound article and noticed the huge difference in chassis earth voltage one way and the other. All you're doing is aligning the primary of the power transformer either one way or the other with the AC mains (and yes, I know it's "AC"!!) but there's some weird electromagnetic effect going on here ... something to do with the "parasitic capacitance" of the power transformer, maybe ... or was it "parasitic impedance"?

I forget!

Remember, the "Neutral" line is in some way tied back to earth (at your switchboard, I think), so "Live" & "Neutral" are not completely the same.

Regards,

Andy

PS: Don't forget to post back when you've done it!

Geoff-AU · « **Reply #10 on:** 27 Jan 2006, 07:46 am »

Since the AKSA is configured as dual-mono the only difference wiring the tranformers out of phase would be that at a given instant in time one PSU is charging its positive filter bank and the other PSU is charging its negative filter bank.

IMO the only way this could effect the sound is in an amp with audible mains hum, because it would then be an out-of-phase hum (and out of phase signals sound weird as you move around the room).

Also, in a MEN (multiple earth neutral) system like Australia has the neutral is tied to earth at your meter box, and also at the power station and no doubt every transformer along the way. Therefore you can be reasonably guaranteed that neutral carries very little voltage and active carries 240VAC. However, licking your fingers and touching the neutral is still not a very smart idea.

hifryer · « **Reply #11 on:** 27 Jan 2006, 08:07 am »

Geoff-AU

Yes, in thinking it through, I came to same conclusion.

Thanks.

Greg Erskine · « **Reply #12 on:** 27 Jan 2006, 12:55 pm »

Quote from: Geoff-AU

Since the AKSA is configured as dual-mono the only difference wiring the tranformers out of phase would be that at a given instant in time one PSU is charging its positive filter bank and the other PSU is charging its negative filter bank.

Here's my understanding. Both banks are charging at the same time because a single bridge produces one waveform that is across both caps. I think if you forget about the centre tap and earth for a minute it becomes clear.

If you connect the toriods out of phase, the waveform will be 180 degrees out of phase but the waveform is still identical to each other because each pulse is 180 degrees. You can't tell which is the original positive pulse and which was the negative pulse (now inverted) and I guess the caps can't either.

If you use 2 bridges per toriod then each bridge will charge each cap. Hmmm...there seems to be more advantages of 2 bridges than I thought.

This seems clear to me at the moment but it is nearly midnight.

regards
Greg

hifryer · « **Reply #13 on:** 27 Jan 2006, 01:02 pm »

Yeah Greg,

It's the sorta thing ya gotta draw up and trace the flow to get ya head round!

cheers

Geoff-AU · « **Reply #14 on:** 27 Jan 2006, 01:15 pm »

yeah you're right Greg, I re-read my post just now and thought "hang on..."

so there's zero difference, rather than an insignificant difference. After the rectifier you can't tell the difference and that's straight across the secondary winding(s)...

About the only thing that could POSSIBLY make a difference is field cancellation between the toroids but again, big whoop. Toroids have low radiated field anyway.

Greg Erskine · « **Reply #15 on:** 27 Jan 2006, 01:17 pm »

Hi Bart,

Yeah, I did a few sketches, and I even looked up my "Understanding DC Power Supplies" text to check my sketches.

If you use a full wave or full wave bridge rectification the pulses are synchronised if not in phase. If you use half wave rectification then the phase of the toriods may make a difference, I think.

good night
Greg

Geoff-AU · « **Reply #16 on:** 28 Jan 2006, 12:06 am »

half wave could produce the out-of-phase hum i was talking about.. by charging each set of filter caps at different times. Dunno why you'd use half wave though, you'll double the ripple voltage because there's no charging during one half of the cycle.