- Sorry guys, I should have been more specific. - thermionic addictions 12:02:34 07/03/09
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- In Reply to: RE: Hum pick-up posted by thermionic addictions on July 02, 2009 at 14:03:15
This is not a working amp but one that I am building. I am trying to orient the transformers as well as I can on the top plate before final
assembly.
How I am measuring this is by powering up the power TX then hooking the
primary of the OPT up to my FLUKE multimeter. Then I move the OPT around
to find the lowest reading. I get 37mV on the primary winding and just under 1mV on the secondary winding.
Which reading should I be more concerned with?
And ultimately, I guess what I am asking is how much of this will show up in a finished working amp?
Cal
- RE: Sorry guys, I should have been more specific. - danlaudionut 20:03:34 07/03/09
(1)
- In Reply to: RE: Sorry guys, I should have been more specific. posted by thermionic addictions on July 03, 2009 at 12:02:34
Cal
It's the secondary's ripple that gets to your speakers
so that is the one to be concerned with.
At under 1mV then it's a non-issue IMO.
DanL
- Thanks Dan (nt) - thermionic addictions 06:39:26 07/04/09
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- In Reply to: RE: Sorry guys, I should have been more specific. posted by danlaudionut on July 03, 2009 at 20:03:34
nt
- Thanks Dan (nt) - thermionic addictions 06:39:26 07/04/09
(0)
- RE: Sorry guys, I should have been more specific. - danlaudionut 20:03:34 07/03/09
(1)
- RE: Hum pick-up - maldar 04:55:08 07/03/09
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- In Reply to: RE: Hum pick-up posted by thermionic addictions on July 02, 2009 at 14:03:15
Hum is usually due to : incorrect grounding, component layout issues/routing of wires, or not enough capacitance in the PS, IME.
As long as all grounds go to a single point, I don't get hum issues even with AC filaments. I keep the RCA jacks isolated from the chassis to avoid ground loops.
With indirectly heated tubes, 1-2mVAC at the speaker terminal is the usual standard for my builds. Sometimes I have measured 0mVAC hum.
maldar
- RE: Hum pick-up - Allen Wright 00:48:29 07/03/09
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- In Reply to: RE: Hum pick-up posted by thermionic addictions on July 02, 2009 at 14:03:15
Forgetabout simulations, how much hum pickup do you actually get in real life?
I cannot believe a simulation can give you ANY hint of hum transference from power TX to OPT. What spice maker has ever modeled audio transformers with this in mind?
37mV would be a HUGE amount if that was appearing at the speaker terminals. A target of 1-2mV is more like a top amp.
Regards, Allen (Vacuum State)
- RE: Hum pick-up answer ( .05mv ok.... other sources are usually worse - -3db 22:38:20 07/02/09
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- In Reply to: RE: Hum pick-up posted by thermionic addictions on July 02, 2009 at 14:03:15
If you are measuring 37mv....something is seriously wrong...some grounding problem...or winding problems in one of the transformers etc.
usually actual radiated magnetic field...i.e. induction hum...is very small if you are at all careful about tranformer orientation and layout.
<.1mV almost always, or around there.... in the SE business there is a sensitivity to hum, so through really listening, and measuring various layouts, around .05mV is really possible.
ok..
Good Luck,
-3db
- RE: Hum pick-up - danlaudionut 22:27:12 07/02/09
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- In Reply to: RE: Hum pick-up posted by thermionic addictions on July 02, 2009 at 14:03:15
Cal
Are you sure it is from the power TX?
I have mine just a few inches away
and I have no hum problems.
I think Palustris might be right.
If you tried/have the OPT rotated
and more than a few inches away
then I would say it is a bad tranny
or at least a poorly designed one.
DanL
- RE: Hum pick-up - slownlo 18:15:35 07/02/09
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- In Reply to: RE: Hum pick-up posted by thermionic addictions on July 02, 2009 at 14:03:15
HI Cal,....
I measure about .07mv across the sec leads of the OPT of my latest build. Most of my others are around the same thing. Try putting some Mu metal/copper foil inside the bells of the PT to minimize it....
- OK, I was hoping for an actual answer to my question, but.... - thermionic addictions 17:11:02 07/02/09
(0)
- In Reply to: RE: Hum pick-up posted by thermionic addictions on July 02, 2009 at 14:03:15
nt
- RE: Hum pick-up - Palustris 16:01:13 07/02/09
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- In Reply to: RE: Hum pick-up posted by thermionic addictions on July 02, 2009 at 14:03:15
Some power transformers are more prone to radiating EMF. Try a different transformer.
- RE: Hum pick-up - casouza 15:32:54 07/02/09
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- In Reply to: RE: Hum pick-up posted by thermionic addictions on July 02, 2009 at 14:03:15
Have you tried mounting them at a right angle (90 degrees lamination-to-lamination) ?
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