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Primaluna's AC Offset Killer
Primaluna's AC Offset Killer
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Old 29th May 2018, 05:59 PM   #1
Alexandru is offline Alexandru  United States
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Default Primaluna's AC Offset Killer

Click the image to open in full size.

Is anybody familiar with this circuit?
What exactly does it do?

Last edited by Alexandru; 29th May 2018 at 06:07 PM.
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Old 29th May 2018, 11:04 PM   #2
MAAC0 is offline MAAC0  Portugal
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I would say it's a double bridge
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Old 29th May 2018, 11:05 PM   #3
TonyTecson is offline TonyTecson  Philippines
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Primaluna's AC Offset Killer
if EI traffos were used instead, snubbers can help...
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Old 1st June 2018, 07:38 AM   #4
basreflex is offline basreflex  Spain
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I think it is a set of antiparalell diodes in series with the transformer load, with a snubber cap to reduce the ringing.
the 0.7V threshold means that it can tolerate +/- 0.7V dc offset.
if more diodes are placed in series it can tolerate more offset. at the cost of some dissipation.
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Old 1st June 2018, 04:35 PM   #5
Alexandru is offline Alexandru  United States
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In the beginning, after reading this “Our engineers designed the AC Offset Killer to lower transformer noise to a place no other manufacturer dreams of going, regardless of how bad your electricity is. The result? Sense of space. Texture. The resonance of an acoustic guitar or violin string that seems to trail on forever. The AC Offset Killer will amaze you. “ I thought it’s just a marketing gimmick.

As far as I understand, the circuir was originally designed but the parent company Ah! Tube who manufactured a power outlet called Ah! AC Offset Killer “AC Conditioner which improves sound and "kills" mechanical transformer hum!”

If it’s such a simple and effective circuit why not everyone else is using it?
Can we build it and test its claims? It costs what? $5-10?

Last edited by Alexandru; 1st June 2018 at 04:38 PM.
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Old 1st June 2018, 04:41 PM   #6
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by Alexandru View Post
In the beginning, after reading this “Our engineers designed the AC Offset Killer to lower transformer noise to a place no other manufacturer dreams of going, regardless of how bad your electricity is. The result? Sense of space. Texture. The resonance of an acoustic guitar or violin string that seems to trail on forever. The AC Offset Killer will amaze you. “ I thought it’s just a marketing gimmick.
Good lord! That's some pretty high end marketing drivel there.

The circuit in the picture appears to be a DC block, and not a very well designed one at that. Here's what Rod Elliott recommends:
Primaluna's AC Offset Killer

You can read his writeup here: Mains DC and Transformers

DC on the mains can cause some mains transformers to hum from mechanical vibration. The DC blocker eliminates this hum. It doesn't impact the signal amplified by the amp in any way, it is purely to address any mechanical hum/buzzing of the transformer.

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Last edited by tomchr; 1st June 2018 at 04:44 PM.
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Old 1st June 2018, 05:09 PM   #7
Alexandru is offline Alexandru  United States
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Interesting, I wonder why they are claiming it improves sound?!
It looks like they put this circuit only in their premium products (over $3k).
If it's such a simple, cheap and effective circuit why don't they put in all their products?

If Tom & Rod are right then Primaluna is shameless.

Click the image to open in full size.

Last edited by Alexandru; 1st June 2018 at 05:27 PM.
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Old 1st June 2018, 05:56 PM   #8
basreflex is offline basreflex  Spain
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dc on the mains can cause small toroid mains transformers to fail, due to saturation.
for example an intermittent ac connection ( a half cycle or 2 missing) does the job. typical for above ground mains power lines with oxidised connections.
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Old 1st June 2018, 06:03 PM   #9
Alexandru is offline Alexandru  United States
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Ok, so the circuit costs aprox $20 in parts at Mouser.
I wish I had the tools to test their claims.
Are these DC blocks in series or in parallel?

Last edited by Alexandru; 1st June 2018 at 06:06 PM.
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Old 1st June 2018, 06:16 PM   #10
basreflex is offline basreflex  Spain
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ech line has 2 series 2 antiparell diodes, the rod elliot circuit in each line, except 0.1uf instead of 2200uF to save money.more a 10$ circuit
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