Feedback blew my phono stage?
Well, dear Henry, Americans lost the control of their domestic and foreign debts, their jobs, Irak and Avganistan,etc., while we all in the European Union hope that the Germans will liberate us from the Euro crisis. They are really in control and I am not sure who actually lost the II WW. The Britons who hope to earn some money with tourism ( their industrial capability you can see by the Linn LP-12) teach their kids : don't mention the war to any German tourist. Regards, |
It doesn't look that way from where I sit. National debt(s) and lack of jobs are problems everywhere in the so-called industrialized world these days, are they not? In southern Europe the problem is far worse than anywhere in the US. On topic, I agree with Dover, if Mr. Halcro in Adelaide will not at least give you a schematic, I would consider dumping the DM10 at this juncture. But you also own the amplifiers, as I recall. |
Today the Halcro designer writes:-I too can't imagine how the choke failures could have been caused by the turntable. The only semblance of an explanation I can think of is that the abrupt eruption of the very high level oscillation, caused by feedback, may have in turn caused a very large voltage transient to be generated across the chokes as a result of inductive kick (chokes are inductors). And perhaps that high voltage transient somehow coupled into whatever circuit the electrolytic capacitor is located in (perhaps it serves as a filter for some internal DC supply voltage), causing or hastening its demise. FYI, see page 6 of this document for an explanation of what a common mode choke is. Best regards, -- Al |
Hi Al, I mentioned to 'Mr Halcro' that I had the 'ground' cable of my Victor TT, attached to one of the DM58 monoblock amps and could THAT cause the problem? It is possible that the grounding on the power amp may cause a voltage difference that could burn out the chokes. I would also be interested to hear if the feedback problem went away as well.Is his reply. What do you think? Regards Henry |
He's obviously far more familiar than I am with the grounding schemes in the preamp and the amps, but FWIW I can't envision how that could have caused the problem. Especially given that the setup has been working well for a long time, with many different MM cartridges. And there have never been any symptoms when the stylus is elevated above the record. That said, have you tried grounding the TT to the preamp? (I realize it is a little further away). That is of course the more usual arrangement, and the symmetry it would provide between channels (given that the amps are monoblocks) would seem to make it the more logical approach, if in fact it makes any (sonic) difference at all. Best regards, -- Al |
