[Folsom]

How do you explain such negative feedback? Shinyata's iron cores are not in parallel, an hence an explanation.

Also a bunch of his claims wouldn't be true unless the inductor is being used to store energy. Otherwise he's claiming regular AC functions are his doing.

I guess being him would still be good if he's really sold so many, as you pointed out.

Here's a question. What have you tried?

[corndog71]

Hum is usually caused by a grounding or cable issue. Only the power amp should be grounded. I still like things plugged directly into the wall. No power conditioners in my house. I still contend that for power amps especially their added resistance is not favorable.

What about lightning strikes, brown outs, etc?

My amplifiers have serious filtration and RF protection and very few problems with ground loops.

Do you have any recommendations for the DIY amp builder for filtration and RF protection?

What about "dirty" AC?  I seem to have a problem with the AC in my apartment in that it can cause power transformers to hum/resonate.  It happens randomly with some of my amps/ receivers and I've even noticed my variac do it.  The ceiling fans in the apartment hum too.  (100 year old building with regular 3-phase wiring according to my landlord)  What's weird is that I have a couple of amps that don't seem affected by it and are always quiet.

[Folsom]

Try the Van Alstine Humdinger, sounds like you got DC going into your stuff... Not necessarily a power conditioner thing, but I can tell you there's probably a lot of noise on your lines given where you live. A lot could be as little as 4%. That's how little one reviewer of an Audience Adept unit had, but won't listen without a conditioner now (6moons article).

[corndog71]

Try the Van Alstine Humdinger, sounds like you got DC going into your stuff... Not necessarily a power conditioner thing, but I can tell you there's probably a lot of noise on your lines given where you live. A lot could be as little as 4%. That's how little one reviewer of an Audience Adept unit had, but won't listen without a conditioner now (6moons article).

I actually got one of those last year.  Had no effect on my tube amp but did help my sub amp.

[Folsom]

I actually got one of those last year.  Had no effect on my tube amp but did help my sub amp.

They are only for blocking DC, which causes a loud hum in transformers when it's bad.

Now if DC isn't your problem, look back to what Roger said, you probably got grounding issues. It's not easy to address, I know...

[corndog71]

They are only for blocking DC, which causes a loud hum in transformers when it's bad.

Now if DC isn't your problem, look back to what Roger said, you probably got grounding issues. It's not easy to address, I know...

With inputs shorted it's virtually dead quiet from the speakers.  But the power transformer hums roughly 5db measured 1" from the transformer.

[Roger A. Modjeski]

What about lightning strikes, brown outs, etc?

Do you have any recommendations for the DIY amp builder for filtration and RF protection?

What about "dirty" AC?  I seem to have a problem with the AC in my apartment in that it can cause power transformers to hum/resonate.  It happens randomly with some of my amps/ receivers and I've even noticed my variac do it.  The ceiling fans in the apartment hum too.  (100 year old building with regular 3-phase wiring according to my landlord)  What's weird is that I have a couple of amps that don't seem affected by it and are always quiet.

Sounds like you have some DC on the line. This is a big problem for torroids and transformers at high flux. Actually domestic power is called 2 phase 120/240V. Three phase is only found in industrial areas to run big motors. The phases are 120 degrees apart.  I doubt you have 3 phase, but this does not matter.

Your Variac is basically a torroid and sensitive to DC on the line.  To measure the DC on the line you have to remove the AC with a filter that  you can make. Take a film cap around 0.47  uF or larger and put that in parallel with the input of the Digital meter. Put a 100 K resistor in series with the hot lead. Connect the hot and negative across the line, preferably the negative to the neutral and the 100 K to the hot. The neutral is the wide slot.

Set the meter to DC volts. Note what the DC is for various noises from your transformers and fans. The noise they make should be louder when there is more DC.  Let us know what happens.

[Wayner]

With inputs shorted it's virtually dead quiet from the speakers.  But the power transformer hums roughly 5db measured 1" from the transformer.

Transformers can also produce a "mechanical" hum, from loose laminates vibrating at the 60hz frequency. Because this frequency is so low, and it mimics the usual "ground loop" hum, many people pursue the problem and fail, because they did not realize the problem was a mechanical hum. Using a DC blocker wont help here obviously.

[Speedskater]

Actually North American residential power is single phase with a center tap for Neutral. It's also known as split phase 120/240.

But corndog may live in a large building, serviced by 3 phase power.

[corndog71]

Actually North American residential power is single phase with a center tap for Neutral. It's also known as split phase 120/240.

But corndog may live in a large building, serviced by 3 phase power.

Yep, my building has over 25 units.  I could be wrong but I'm pretty sure she said 3-phase.  I know there are 240V outlets for in-unit washer/dryers.

[corndog71]

To measure the DC on the line you have to remove the AC with a filter that  you can make. Take a film cap around 0.47  uF or larger and put that in parallel with the input of the Digital meter. Put a 100 K resistor in series with the hot lead. Connect the hot and negative across the line, preferably the negative to the neutral and the 100 K to the hot. The neutral is the wide slot.

Set the meter to DC volts. Note what the DC is for various noises from your transformers and fans. The noise they make should be louder when there is more DC.  Let us know what happens.

Before I do anything I would just like to confirm that I understood what you wrote.  Does this look correct?

[jea48]

Before I do anything I would just like to confirm that I understood what you wrote.  Does this look correct?

Yes...

This guy recommends a 10uF non-polarised capacitor.

 you need a 100k resistor and a 10uF non-polarised capacitor, wired in series. Connect this circuit across the mains (power off!), and connect a DC voltmeter across the capacitor. This attenuates the AC enough to prevent the front-end of the meter from being overloaded, and the DC voltage is easy to measure. Expect to see the DC vary around the zero voltage, with a normal variation of +/-25mV or so (typical - residential areas). The alternative method is to measure the DC across the diode/capacitor network in the circuit of Figure 3. Do not connect or disconnect the meter with the circuit live, and use alligator clip leads to make the connections.

http://sound.westhost.com/articles/xfmr-dc.htm

[Roger A. Modjeski]

Before I do anything I would just like to confirm that I understood what you wrote.  Does this look correct?

Your drawing is correct. I don't think 10 Uf is necessary. I go find mine or go build one right now and let you know. I am curious about my home too.

[Roger A. Modjeski]

Your drawing is correct. I don't think 10 Uf is necessary. I go find mine or go build one right now and let you know. I am curious about my home too.

Yes that will work. I found mine  has a 1 uf capacitor and 560K 1/2 watt or greater series resistor. None of these parts are special or critical in value. When connected to the power line I measure 0.5 volts AC. That is low enough for the DC function to decipher the voltage on the line. The series resistor size will reduce the measurement by being a voltage divider to the meter. However the meter is usually 10 meg ohms (you should check the specs or with a known battery as the source). If the series resistor is 1 megohm the meter will read 10% low, 560 K will read 5% low. This is a simple voltage divider for the DC part. It is for the AC part if you calculate the reactance of the capacitor.

When you test the set-up see that your meter measures some small AC voltage. then turn it to DC and see what you get from time to time. My house has no DC, not even a few millivolts. To test I took a 100 watt light bulb and put a half wave rectifier in series with it. That combination put 0.22 DC volts on the line. It is always good to conduct an experiment to see that something reasonable happens when you load the system.

I was telling Ben that when I put 0.2 volts on the line all my neighbors on the same pole transformer got that too minus some losses from house to house, but I bet I could plug the lamp in my house and measure it in theirs.

[corndog71]

Ok, I measured 6.5VAC and -0.010 to -0.018VDC. 

By the way, I picked up a used Hitachi Oscilloscope.  Still figuring out how to use it.

[Roger A. Modjeski]

Ok, I measured 6.5VAC and -0.010 to -0.018VDC. 

By the way, I picked up a used Hitachi Oscilloscope.  Still figuring out how to use it.

OK, That's pretty small. Take another look when things start humming.  I think I have seen hitachi owners manuals online for free. Which model did you get? I have one that has been working a long time, though I had to fix it recently.

Scopes are very similar and there must be some tutorials on line. The knobs all have names.