tkkara Posted August 6, 2014 Posted August 6, 2014 Hi all, I'm a bit of a newbie here and was hoping to get some input on an issue I have with my tube amp. I have noticed an intermittent crackling noise, every 2-3 minutes or so (and only lasts around 2-3 seconds). I tried the amp in a different part of the house and didn't get this issue, so I suspect it has to do with the power point I'm using. I'm wondering whether using a fancy shielded power cable might removed this noise. I also get some light hissing sounds out of the speakers - the silences are silent, if you know what I mean. Hoping that a cable might be able to help with this also. I'm using a standard PC power cable at the moment. I would appreciate your thoughts on this.
LogicprObe Posted August 6, 2014 Posted August 6, 2014 (edited) Did you try another cable? edit - also, have you got an electrical mate who could change the power outlet as well? Edited August 6, 2014 by LogicprObe
LogicprObe Posted August 6, 2014 Posted August 6, 2014 You could try this as well.http://www.jaycar.com.au/productResults.asp?keywords=deoxit&keyform=KEYWORD&SUBMIT.x=6&SUBMIT.y=9
tkkara Posted August 6, 2014 Author Posted August 6, 2014 Yeah, I've tried other cables and they all produced similar results though I had one slightly thicker cable which seemed to have a quieter crackle but that could be in my head. All the cables I tried were cheap PC cables. So you think it could just be a case of having to clean the prongs on the power cable? Or clean something else I don't have any electrician friends to get in to replace the point. I suspect the power point I'm using is too far away from the distributor and might be affect by stuff along the line. It's st the back of the house.
everyones_shadow Posted August 24, 2014 Posted August 24, 2014 Have you tried reseating your tubes and cleaning their contacts? If a pin is slightly out it could be (for instance) breaking connection to earth when it vibrates. Cheers ES (who really must clean his own cords and tube pins)
elcamry Posted August 29, 2014 Posted August 29, 2014 It could also be the power point switch , may be worth changing the whole power point to eliminate that possibility . 1
Monkeyboi Posted August 30, 2014 Posted August 30, 2014 I agree with elcamry. It all points to a potentially faulty power outlet. Switches in most power points eventually carbon up which leads to noise, localised heating across the switch contacts and eventual failure. It could also be that one of the wires isn't screwed down to the connector terminal correctly. Either way it's got to be fixed. To cure the problem and avert a possible electrical fire I sincerely suggest you get an electrician to take a look at it. More than likely it will need to be replaced. This isn't an expensive job as the wiring to the power point is most likely unaffected. Cheers, Alan 1
LogicprObe Posted August 30, 2014 Posted August 30, 2014 I've seen them carbon up so much that they explode from the arc!
Krispy Audio Posted August 31, 2014 Posted August 31, 2014 I had a similar issue (although didn't try it in a different room) and found the driver tubes to be the culprit. My power point is unswitched and cables were all new-ish, not sure if it was the vacuum tubes themselves or the terminals which had a clean when I replaced them. Worth doing anyway to test it out. Also when I had it, it was intermittent. Like I could go for a few days with no crackles, then in one listening session I'd get the 2-sec thing every couple of minutes.
awty Posted August 31, 2014 Posted August 31, 2014 Is the power point on the same circuit as the fridge or other motored devices. Try switching them off and see if the problem goes away.
Guest Muon Posted August 31, 2014 Posted August 31, 2014 I had this sort of thing the other day, and it was the valve pin/socket contacts. But this thing is to do with the outlet as pointed out. Will be iteresting to know the issue with that outlet..
tkkara Posted September 2, 2014 Author Posted September 2, 2014 Thanks for the tips. I will check out the contact and get an electrician out to look at the power point (and all the rest of the power points while he's at it). I'll post an update if/when I resolve this. Thanks again!
LogicprObe Posted September 2, 2014 Posted September 2, 2014 New outlets are cheap and if you are calling someone in, he might as well do something!
valvedude Posted September 29, 2014 Posted September 29, 2014 (edited) you might want to take all you tubes out grab some 000 steel wool and gently glean all the pins with protect and wipe off with isopropyl alcohol apart from that what kind of amp do you have is all your hi fi component running from the same power out let to avoid earth loop Edited September 29, 2014 by valvedude
valvedude Posted September 29, 2014 Posted September 29, 2014 how may hours have you valve done most valve have so many hours mainly what i have found when tube amps pop crackles is A power supply B bias is gone wonky C one of the tubes is shorting on and off intramurally this can be detrimental output tranny can be come damaged etc i would check and make sure your phase inverter tube is clean and not dirty if the amp has one you can tell if the valve sockets are dirty by powering up the amp and gently moving valves watch the outputs and rectifier they can get mega hot hope this helps sorry if it long winded 1
Equaliser Posted September 29, 2014 Posted September 29, 2014 (edited) Is the crackling noise from initial powerup or poweroff? Bias gone wonky is definitely one of the more common intermittent crackling issues I've had especially in an unregulated power supply design if mains is high, B+ throughout, plate and heater all going to be running 5-10% higher then spec'ed values. Seems small numbers but not good for the transformer, tubes and output transducers if something shorts and there is no relay or protection circuit. Observe the tubes while amp is in use, when you hear the crackling effects, see if your tubes are arcing (blue lightening strikes inside vacuum glass). If so, power off immediately and rectify the cause of issue. Edited September 29, 2014 by DefQon 1
valvedude Posted September 29, 2014 Posted September 29, 2014 Is the crackling noise from initial powerup or poweroff? Bias gone wonky is definitely one of the more common intermittent crackling issues I've had especially in an unregulated power supply design if mains is high, B+ throughout, plate and heater all going to be running 5-10% higher then spec'ed values. Seems small numbers but not good for the transformer, tubes and output transducers if something shorts and there is no relay or protection circuit. Observe the tubes while amp is in use, when you hear the crackling effects, see if your tubes are arcing (blue lightening strikes inside vacuum glass). If so, power off immediately and rectify the cause of issue. yes some times blue sparks could mean cathode screen and grid are shorting i have seen a lot of chines made amp the 240 tranny is 200 volts ac so the EHT is so hi i am old school when i build valve gear i adopt the KISS method 1
Equaliser Posted September 30, 2014 Posted September 30, 2014 (edited) i have seen a lot of chines made amp the 240 tranny is 200 volts ac so the EHT is so hi Indeed, Never seen or measured 200vac on the mains for the power trafo but I know alot grey imports and stuff on ebay etc etc that says 230/240v in 90% of cases you're getting a 220vac (standard rating in China). Since the ac lines here in Vic at least is so damn dirty, polluted and not even at 230vac (measured multiple points almost at 245vac), that really reduces the lives on an unregulated power supply of a tube amp especially those with no ac-dc regulated circuit for heater and cathode specs of the tube. I'm not old enough to know what the KISS method is. Edited September 30, 2014 by DefQon
valvedude Posted September 30, 2014 Posted September 30, 2014 keep it stupid simple yar voltage here bad too
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