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jea48 DC on the line to isolation transformer causing hum?

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Posted on January 30, 2017 at 03:49:16
dcuhl
Audiophile

Posts: 148
Location: Mid-Atlantic, USA
Joined: January 13, 2013
 jea48 and anyone else who'd like to chime in, As of late my wife's blow dryer is causing my Topaz 1.8Kv line noise suppressor transformer itself to hum loudly. From what I have read, DC is the most likely cause for these types of transformers to hum. Is there a DC blocking device/filter that I can put in-line, between the AC supplying the transformer and the transformer itself, to keep it from humming and without causing any ill effects to the sound quality of my system? If so, what specifically and from whom? Your take on the situation would be most appreciated.

 

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RE: jea48 DC on the line to isolation transformer causing hum?, posted on January 30, 2017 at 04:12:02
Ryelands
Audiophile

Posts: 1867
Location: Scotland
Joined: January 9, 2009
 See link for one possibility.

HTH

D

 

RE: jea48 DC on the line to isolation transformer causing hum?, posted on January 30, 2017 at 13:52:01
Duster
Manufacturer

Posts: 17117
Location: Pacific Northwest
Joined: August 25, 2002












I'm sure there would be a sonic impact if an inline DC blocker is inserted between an AC outlet and an isolation transformer. However, this issue may be dependent on how sophisticated your AC delivery system might be. Additionally, like other filters, sometimes a filter may do more harm than good as a sonic fix. If the interference is only problematic once in a great while, I suggest you consider how important the issue is.

Here's a finished DC blocker with various AC I/O connectivity options (see link below).

The NEMA AC outlet version looks questionable in terms of audiophile performance potential, while the version with I/O cable glands as strain relief might be the better sounding option if the power cord OD is 16mm (0.63 inch) or less. Another option the seller might be able to provide if asked is chassis-mount Neutrik powerCON High Current jacks, which is a very good sounding AC connector/jack interface for an inline AC delivery application that allows the use of a large OD power cord, IME. Otherwise, I look forward to seeing jea48's response.

 

Looks like Duster found a good looking DC Blocker. nt., posted on January 30, 2017 at 15:13:49
jea48
Audiophile

Posts: 6770
Joined: January 5, 2005
 nt.

 

RE: jea48 DC on the line to isolation transformer causing hum?, posted on January 30, 2017 at 15:17:49
jea48
Audiophile

Posts: 6770
Joined: January 5, 2005
 Duster,

Why couldn't the blocker be installed between the hair dryer and the mains wall receptacle? I think it would work the same and block the DC from the hair dryer from going back out on the AC mains.

 

RE: jea48 DC on the line to isolation transformer causing hum?, posted on January 30, 2017 at 15:30:35
Duster
Manufacturer

Posts: 17117
Location: Pacific Northwest
Joined: August 25, 2002
 That seems like a brilliant solution, jea48. The same notion as implementing any kind of AC power line filter effort firstly on the noisy appliance rather than only trying to block audible noise just before the sensitive component involved. Sometimes, audiophile filtering can be effective at both ends of the situation. I'm not an EE, so maybe Jon Risch could post his insights.

 

RE: jea48 DC on the line to isolation transformer causing hum?, posted on January 30, 2017 at 23:50:02
jhrlrd
Audiophile

Posts: 135
Joined: October 21, 2014
 I love the Hum dinger by AVA. Doesn't seem to harm sonics that I can tell. Without it my power conditioner hums like crazy.

 

I have ferrite clamps on my refrigerator AC cord.. several of them :) nt, posted on January 31, 2017 at 12:49:26
3+4=5
 .

 

RE: I have ferrite clamps on my refrigerator AC cord.. several of them :) nt, posted on February 1, 2017 at 04:43:33
dcuhl
Audiophile

Posts: 148
Location: Mid-Atlantic, USA
Joined: January 13, 2013
 Me too and one on the microwave as well, just for grins.

 

To clarify - The isolation transformer in use, is an IE, Not a toroidal. nt, posted on February 1, 2017 at 14:35:09
dcuhl
Audiophile

Posts: 148
Location: Mid-Atlantic, USA
Joined: January 13, 2013
 .

 

RE: To clarify - The isolation transformer in use, is an IE, Not a toroidal. nt, posted on February 1, 2017 at 16:35:14
jea48
Audiophile

Posts: 6770
Joined: January 5, 2005
 Usually EI transformers are not affected by DC on the mains.

What model number is the transformer?

Most importantly how cheap is the wife's Hair Dryer?
Is the circuit the hair dryer is being used on a separate circuit? 20 Amp?

 

Isolation transformer in use info, posted on February 2, 2017 at 15:22:46
dcuhl
Audiophile

Posts: 148
Location: Mid-Atlantic, USA
Joined: January 13, 2013
 Sorry EI type. Transformer is a Topaz Ultra-Isolator Model# 91018-32, 1.8KvA with a capacitance rating of .0005 pF, 120 volts in/120 volts out, 60 cycle.
The transformer is connected to a dedicated 20amp line whose configuration is as follows: 20 amp square d circuit breaker - 12/2 romex cable about 30 feet long into an aluminum housing exterior grade duplex outlet box - Oyaide R-O duplex outlet - ARC Preamp SP8MkII rev.7 into 1 outlet, Topaz into the other outlet. The Jolida 100 cd player is plugged into the isolation transformers Hubble 8300 duplex of which one of the duplex's outlet is covered by an Oyaide sendust plug cover.
The wife's blow dryer, can't tell ya, though its probably not cheap as she is a hair dresser by trade and wouldn't put up with junk. The inside components of the dryer maybe of questionable quality, don't know I haven't opened it, at least not yet.
Hope the background info helps. Many thanks.

 

RE: Isolation transformer in use info, posted on February 3, 2017 at 12:54:44
jea48
Audiophile

Posts: 6770
Joined: January 5, 2005
 Everything sounds fine to me. Why any DC offset on the mains would have any effect on the Topaz EI transformer beats me. You might check to make sure the end bells are securely tight on the transformer.

The only thing I can tell you is to either buy a DC blocker or build one yourself. If you build one make it big enough so you can try it on the Hair Dryer. Some of those dryers are 1500 watts. (1500 / 120V = 12.5 amps)

The only other thing I can think of is to buy a different brand/manufacture hair dryer for the wife.

One other thing that comes to mind you could try, check out, is to see if the topaz transformer and hair dryer receptacle are fed from the same Line, leg, in the electrical panel. If on the same Line, leg, try putting the hair dryer receptacle on the other Line, leg, or your dedicated 20 amp circuit for your audio on the other.

You never did say where the hair is used now and what the branch circuit size is, 15 or 20 amp. Is the circuit shared with other loads?



 

RE: EI transformer construction doesn't always mean air gap, posted on February 3, 2017 at 14:13:25
slider
Audiophile

Posts: 298
Joined: September 13, 2010
 Looks like there was some pruning done in this thread. I think if you are going for efficiency, there won't be an air gap, and the laminations supply a complete circuit. Of course, if the cores are designed to handle DC, there will need to be a gap to prevent saturation, same as with toroids that have a gap cut when used for choke applications.

 

RE: Isolation transformer in use info, posted on February 6, 2017 at 15:33:16
dcuhl
Audiophile

Posts: 148
Location: Mid-Atlantic, USA
Joined: January 13, 2013
 Sorry for the delay in responding, my 20 year old daughter is having some health issues. The isolation transformer consists of 3 major parts, the front and rear 3rd's are identical cast aluminum housings with different end plates, one with the AC cord the other with a single duplex outlet, no fuse and no power switch. the middle third is the transformer itself. 3 through bolts, two on top, one center bottom hold the 3rds together. So in reference to the bells perhaps being loose and possibly causing the hum, there really aren't any bells as one would think of them. The topaz uses the cast aluminum housings as the bells, the insides of which are empty or hollow with nothing to block the transformer radiated emi from reaching the incoming AC current or from it reaching the back side of the duplex and its AC connections. What to do in this space to shield, block or absorb the emi has been the subject my mind ponders, whenever it has a free moment.
The blow dryer could be in a 15 or 20 amp circuit as the most likely breakers are adjacent and it could logically be on one of three and the only real way to find out is to intentionally trip it to find the specific one rather than flipping breakers and having to reset or reprogram various kitchen devices, which I am unwilling to do. As to which leg, again I'd have to trip the breaker to know for certain. Perhaps the next time the power goes off and I have to reset the appliances anyway I'll take the 3 minutes to figure it out. To all whom responded, many thanks for your help and input, it is appreciated.

 

RE: Isolation transformer in use info, posted on February 8, 2017 at 14:58:27
jea48
Audiophile

Posts: 6770
Joined: January 5, 2005
 Sorry to hear about your daughter. I hope she is doing better.

.


3 through bolts, two on top, one center bottom hold the 3rds together.

Make sure the 3 through bolts are tight. It is possible the steel laminations of the EI transformer may not securely be tight against one another. Like I said in an earlier post it is unusual for an EI transformer to physically vibrate from DC on the AC mains.

//

The blow dryer could be in a 15 or 20 amp circuit as the most likely breakers are adjacent and it could logically be on one of three and the only real way to find out is to intentionally trip it to find the specific one rather than flipping breakers and having to reset or reprogram various kitchen devices, which I am unwilling to do.

Danger! Never intentionally attempt to trip a circuit breaker. IT may not trip open.
Believe it or not when UL tests a circuit breaker they only test the breaker twice to see if it trips open. Scary ain't it?

You can buy circuit checkers fairly cheap that will locate the breaker that feeds the branch circuit wiring. Below is a link for an example.

 

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