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In Reply to: Re: Actually, it's just a bunch of hooey posted by dave slagle on April 20, 2007 at 10:20:40:
Dave,Seems like Messers. mikeyb and Triode Kingdom are not reading too well, in their rush to ctriticise me.
AND..... notice, we have STILL not gotten Triode Kingdom to post his audio credentials to critique me, up on this Forum.
Here is what I posted :
" The first thing I did.... I added a neat 37 mHY choke as a choke input filter so I have a ( not meeting critical inductance at 60 HZ ) L input filter in my HF-81 to strip RF and control the twin EZ81 tube diodes !! "
I think thats pretty clealy worded, don't you?
It sounded better as L - input IMHO, slightly better, but not at all as effective like the heavy high quality wire for B+ distribution to under 1 mA tube stages.
One other mod I did Dave, the tubes in the stock unit are getting disturbed by being physically too close to the irons' fields, both the HF81 power transformer and the output transformers. I've made metal shields to go around the power trannie and outputs, so as to shield them from fields adversely acting upon the four EL84s and two EZ81s. I also shielded the amps front end tubes from the EZ81 twin rectifiers interference. That was cool and the improvement couldn't be gotten any other way on the stock chassis !!
All else, audio parts wise, was left stock, just to show how important the power supply changes I did elect to change was - to ANY piece's overall audio performance. Cheers Dave.
Jeff Medwin
Follow Ups:
Was the sheilding made from mu metal? T Willman
Nope. But ANY metal is better than letting the iron's field freely RADIATE into the tube while it is operationg too close to the iron Tom. Right ??!! Regards .
It was used extensively in the early days of electronic design. How ever Crutchfeilds sells mu metal foil at a resonable price. Mu metal does a great job of sheilding low frequency emf. If you look around at swap meets and in vintage surplus electronics you can also find the thicker far more effective variety. That is if you want the killer stuff! T Willman
than the low DCR crapola being continually regurgitated onto this forum. The possibility that a strong magnetic field from an OPT might influence a nearby tube seems entirely plausible. It is, however, the sort of thing that should be measurable. In the absence of discernible mutual conductance or other tangible evidence, this concept should similarly be shucked in the nearest rotary bin. Building shielding when no such anomaly has been adequately demonstrated is self-delusional.
that the out put or the power tranny can emit rf. There for I would think that low frequency emf might be a problem in the right situation and proximity. My experience with mumetal was to sheild my power transformer from my output transformer. This ultimatly was only needed to lower hum during turn on while there was no curent flowing through the output transformer. I consider it wasted money because it was not needed after warm up. T Willman
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