I get a small thump from one or the other speaker when there is no signal going to them and the Amplifier is turned off? I have recently re-capped the crossovers with polypropylene caps in place of electrolytics. Would this be leakage from the poly caps and nothing to worry about? I'm not really worried I'm just curious to what's happening here?
That does not come from the crossover.
Does your amp actually switch off the mains? Or is it just a 'soft' off (trigger button), per remote, per small button or got it 'off' to standby? If that's the case, it could 'wake up' if a switching noise is comming from the mains or a short interruption of the mains could be the reason.
Does your amp actually switch off the mains? Or is it just a 'soft' off (trigger button), per remote, per small button or got it 'off' to standby? If that's the case, it could 'wake up' if a switching noise is comming from the mains or a short interruption of the mains could be the reason.
The amplifier is a Sansui AU-11000 I've had it for years, its never done this before and this sound has only started in the last month or so since I've re-capped the crossovers. I used polypropylene motor run capacitors for the woofers and mids. The low thump-crackle sound only happens on one speaker at a time and only every now and then? I only hear it when everything is quiet and I'm doing something on my computer about 10 feet from the speakers. I haven't secured the motor run caps properly in the photo because I was testing them to see if they would work OK? They do! I can only think its capacitor leakage?
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That's a very nice amplifier, I like the Sansui AU-11000 very much. It got no standby or similar, I pretty much doubt it's coming from the amp unless the protection relay hangs. Does it click after switching on? You should also check it for DC offset.
When I said it can't be the crossover I was assuming you've replaced all caps. The photo shows something I don't like: The can-type high voltage electrolyte capacitor. You should replace it, that will very likely improve the sound. Hard to say how old it is but it surely does not look new. These often leak or heat up if they get old. If it cools down, it may create a mechanical noise or the charge changes and they actually can discharge at seemingly random times. These caps are the only thing that comes to my mind, if that's not it, I don't know either.
When I said it can't be the crossover I was assuming you've replaced all caps. The photo shows something I don't like: The can-type high voltage electrolyte capacitor. You should replace it, that will very likely improve the sound. Hard to say how old it is but it surely does not look new. These often leak or heat up if they get old. If it cools down, it may create a mechanical noise or the charge changes and they actually can discharge at seemingly random times. These caps are the only thing that comes to my mind, if that's not it, I don't know either.
Those old electrolyte cans are actually new motor run polypropylene caps, they have made these 1974 Quasar QS1 speakers spring to life, not at first though? I was disappointed with the performance at first but the sound got better the more I used the speakers and now I can honestly say they are the best speakers I've ever owned. A well produced live recording sounds live with this set-up.
I'll be sure to let you know if that happens. lol, Maybe these speakers have minds of their own and they are just talking to one another?
I get a small thump from one or the other speaker when there is no signal going to them and the Amplifier is turned off? I have recently re-capped the crossovers with polypropylene caps in place of electrolytics. Would this be leakage from the poly caps and nothing to worry about? I'm not really worried I'm just curious to what's happening here?
I understand it happens in both channels. Does it happen in both channels at the same time?
Jan
I was thinking the same.
According to the Sansui AU-11000 service manual, the power-switch has a 0.1uf 150v C.C. across, and by that, in series with the transformer even when the switch is turned off.
It lists the same 150v part for both 110 and 220v models. Also, the schematic lists 0.01uf but in the parts list its 0.1uf.
Anyway, an old disc ceramic with 150v rating seems insufficient , and certainly if also used in 220v models.
I would remove this cap, and replace it with a snubber. AFAIK this practice has replaced the single capacitor as a sensible arc supression.
Reminds me of my first attempt at an irs2092 class d amp.
Being clever I put big smoothing caps on the amp.
I shut off the amp and then a siren noise started and about 5 seconds later there was massive thump through the speaker.
Apparently, the 2092 doesn't like slowly dying power supply voltages and needs a reset circuit if using large smoothing caps.
I came up with a small PIC micro with a2d and an opto-coupler to hold the amp in reset if Vcc was less than 12 volts. Worked a treat.
I also designed a speaker protect system.
There was a 5 second power up delay on the relay but during that time you could hear the music very low.
I had put a 100nf across the relay to quench arcing of the contacts.
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