Tweakers' Asylum

T I Shield on Transformer info needed

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benie

A

A little late to the party, but I am finally going to try some of this. I would like to use the T I shield on the EI core transformer on my Acoustat Servo Tube amps and hopefully it will kill a bit of hum coming from them.
Do I use a 1" strip or so and wrap it around the iron core or do I wrap it around the Bell covers?
Also, should I run a ground wire to it and then run the wire out to a plug and plug it into an AC outlet.

When I finish that then I'll add some to my DIY power strips.

Thanks for any help.

Follow Ups:

Hummmmmm - bartc 05:49:27 10/28/09 (3)
Listen, I'm not sure you're stating this fully. Hum is usually just native vibration of the transformer, which can be mechanically damped, but I don't know that it can be electrically damped. The TI is for electrical damping. Unless you combine the TI with some other mechanical damping compound (not a bad idea in most applications I know of), this probably won't affect that source of hum.

YOu also get hum if you have a ground loop. I don't believe that the TI has any effect on ground loop. That takes different solutions, and you're idea of running the ground wire to another plug might even exacerbate ground loop hum, if that's what you have.

Meantime, TI is very good used properly, and I have found that the earlier posters who recommended a 12 AWG ground wire were right, at least in my applications. But my applications are nothing like yours. I use the TI to shield parallel AC filters and speaker filters. On the latter the ground wire shouldn't contribute to any ground loop hum, nor does it in my applications on the former. And in both cases I DO use mechanical damping between the TI and the object it surrounds.
- RE: Hummmmmm - benie 14:23:18 10/28/09 (2)
  Thanks for posting bartc.
  It's not a ground loop as it seems to be mostly one amp (Mono Blocks)that hums (dedicated line). I plan to use some of Herbie's damping material (forget what it's called) as washers between the transformer and chassis as well.
  There are times when the hum is quieter than other times, so I think it may be interacting with something.
  I remember cdc (Chris) had a pic of a toroidal transformer that he wrapped T I shield around and that gave me the idea.
  
  I agree that Hum is usually just native vibration of the transformer, which can be mechanically damped, but because sometimes it is worse that other times, I believe there is more to it in my case.
  I am careful about how I place my wiring as I use 3 DIY power strips on dedicated lines and also use a few separate power supplies for a few pieces of gear.
  So I'm thinking shielding with the T I shield might help. I have read where using it on power transformers can be helpful.
  
  My Power strips are much like yours and was planing on using some of the T I shield in there afterwards.
  
  Thanks for your thoughts.
  - loopy - bartc 19:26:18 10/28/09 (1)
    You can get loopy dealing with a ground loop hum! And I've heard also, but cannot confirm, that DC interference on a line can cause trannies to hum as well. So who knows what you're dealing with.
    
    IME, Herbie's stuff is good vibe control. So is Microsorb, which I like a lot, but it's now been discontinued so hard to get. There are other substances. I know one inmate who uses cotton very effectively with TI for mechanical damping. You pick your poison, but one will certainly work for you with the TI.
    
    From CDC I got the info that at least on the speaker filters the guage of the ground wire DID make a difference. And I tested that minimally and found out that he was right. He recommended at least 12 AWG, and that's what I now use whenever I ground Ti-shield for this kind of filtering, even if it's not necessary for other AC filtering functions. Seems to work right, so why quibble.
    
    But if you're grounding the TI from the transformer, I'm somewhat concerned that you may introduce a groud loop or other inadvertent source of noise by using a separate plug. Why not find the place that your whole component is grounded on its chasis and run the ground wire to that? I may be wrong here, of course, and I'm not an EE...
    - RE: loopy - benie 16:52:52 10/29/09 (0)
      he, he your certainly right, some ground loops can make one loopy, takes time to sort out sometimes.
      I should have mentioned I am also using an Elgar 2.5Kv isolation transformer on the amps, so that would kill any DC on the line (DC can make things hum). It is a much lower noise floor with the Elgar isolation tranny in place and because of it's size, it has not hurt dynamics, but before and after the install of that Elgar,that one amp will act up.
      
      I think your right, grounding the transformer T I shield to the the wall AC might induce some noise. I think grounding it to the chassis ground is a better way to go, good call on that. I do remember some talk about the gauge of the ground wire, I have some 12 and 10 awg around to try.
      
      I do take my time on getting things done, but I do get there. Look forward to implementing some of the T I shield into my power strips later as well, you never know, this may help with the problem I'm trying to solve now.
      
      Thanks for your help.

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