View Full Version : Thump on power up
Rare Bird
12-11-2009, 13:52
I'm getting a thump through the speaker on amp power up (yes volume is off), seem the transformer has a large inrush current or something..Maybe a soft start kit which is a current limiting resistor that slowly releases itself..Any ideas?
StanleyB
15-11-2009, 15:10
Which amp is it?
The majority of amps have a relay in the speaker output, which keeps the speakers disconnected from the amp for anything up to 10 seconds. By that time the power supply inside the amp has been charged up, and it is then OK for the relay circuit to connect amp and speaker together without a thump.
In your case, the above process is failing. If you got an amp with a speaker relay, then there is a fault in that section of your amp.
Rare Bird
16-11-2009, 12:06
Which amp is it?
The majority of amps have a relay in the speaker output, which keeps the speakers disconnected from the amp for anything up to 10 seconds. By that time the power supply inside the amp has been charged up, and it is then OK for the relay circuit to connect amp and speaker together without a thump.
In your case, the above process is failing. If you got an amp with a speaker relay, then there is a fault in that section of your amp.
Hi Stan ONIX 'OA21' No relays in the output just fused..
Disaster struck this morning, i switched on the amp & blew my left tweeter :steam: I've measured the amp output on power up i got a wopping 80mV+ reading that settled below 40mV, even less on the other channel.
I'm fuming.
Hi Stan ONIX 'OA21' No relays in the output just fused..
Disaster struck this morning, i switched on the amp & blew my left tweeter :steam: I've measured the amp output on power up i got a wopping 80mV+ reading that settled below 40mV, even less on the other channel.
I'm fuming.
:( sh$t
StanleyB
17-11-2009, 06:10
If it has no relays, but uses fuses instead, it wouldn't find a place in my system. Not even if you gave it to me for free.
Fuses are very non-linear in their performance. One tiny bit of strand of less than 0.5mm in diameter is no match for a speaker cable of far greater diameter.
The thump cannot be eliminated. It is all part of the way that the split rail power supply capacitors charge up.
Maybe time for you to get a properly designed amp:).
Rare Bird
17-11-2009, 13:08
It is a proply designed amplifier.Not jap shit.
:steam:
Tweeter sorted today, seems it wast the amp that caused it, was a faulty connection. However in powering down the amp today i heard a small click a few seconds after, this is the sound of a relay, but why can't i hear one on power up!!! I had the hood off yesterday but couldnt see no relays but it was deffo the sound of one.
StanleyB
17-11-2009, 13:14
It is a proply designed amplifier.Not jap shit.
With fuses in the speaker output?:D
Rare Bird
17-11-2009, 13:32
Well well well look what i've found hiding under the phonostage board, a row of relays, i thought i could here one on power down, one of the others must be dud, as theres no click on powering up, but i don't know the specs for these!
http://i12.photobucket.com/albums/a222/LIVING-SIN/Onix2.jpg
Rare Bird
17-11-2009, 13:38
With fuses in the speaker output?:D
apparently not..:ner:
StanleyB
17-11-2009, 14:15
As long as you are happy with all the performance you are missing:). Mains fuses are optimized for 50 to 60Hz;).
Today/yesterday are Andre's days : Not only he has to replace his tweeter, but also to cope with various (humorous) statements about his system's performance... :unfair:
Rare Bird
17-11-2009, 14:43
No worries Demitri at least i don't waste money on tripe to get good sound..Thought this place was different but it just the same as elsewhere
Rare Bird
17-11-2009, 14:44
As long as you are happy with all the performance you are missing:). Mains fuses are optimized for 50 to 60Hz;).
Stan the man you wana take a step back
No worries Demitri at least i don't waste money on tripe to get good sound..Thought this place was different but it just the same as elsewhere
Swings and roundabouts, mate. 'Shit happens' everywhere! ;)
Now stop being a big girl and get back with the programme :lolsign:
Marco.
Rare Bird
18-11-2009, 13:27
:(
Btw Andre, have you replaced the tweeter already ?
Rare Bird
18-11-2009, 14:32
Yes new tweeters in, ok now...Set of relays just popped thru the letter box aswell..Job for the weekend.
Cool Andre. I would have hated to have my Scan Speaks broken. Moreover, the SFs are "paired"... :(
Btw, what is your speakers' model ?
Rare Bird
18-11-2009, 16:57
'R652' For the time being..
Rare Bird
21-11-2009, 18:05
Well well well look what i've found hiding under the phonostage board, a row of relays, i thought i could here one on power down, one of the others must be dud, as theres no click on powering up, but i don't know the specs for these!
http://i12.photobucket.com/albums/a222/LIVING-SIN/Onix2.jpg
Well new Relays fitted & i can hear them working now on both power up & down. Set the CD player playing, switched the amp on ''thud'' no music, after 10 seconds elay clicks & music appears..A sucess, the thump now sounds like a heavy click. This has to now be down to a shit power switch..I have the perfect replacement in mind...
http://i12.photobucket.com/albums/a222/LIVING-SIN/New.jpg
Primalsea
22-11-2009, 17:58
Hi Andre,
You could try cleaning the power switch and have a look for a resistor and a capacitor in series across the power switch, these might need changing. Its helpful if you have a scope to check your power rails but if not try to check them with a DMM to see if they are +&- the same voltage. You might have some flaky power supply caps.
Rare Bird
22-11-2009, 23:49
Hi Andre,
You could try cleaning the power switch and have a look for a resistor and a capacitor in series across the power switch, these might need changing. Its helpful if you have a scope to check your power rails but if not try to check them with a DMM to see if they are +&- the same voltage. You might have some flaky power supply caps.
Hi Paul
I intended fiting this (in the link below) they are good.Does away with the AC fuse & some wiring & extra switch contacts no needed, but the transformers bang infront of the power switch & i don't wanna go drilling holes in the back of the amp..I did talk to a friend about strapping a capacitor across this old switch, but to be honest the switch is very poor quality & needs replacing
http://www.e-t-a.be/uploads/prodb/D_1110_e_240909.pdf
sburrell
03-12-2009, 19:42
Sorry to go slightly OT, just wanted to say that my new (to me) Creek 4040 gives quite a bass thump on powerup. Could this be a similar issue to Andre's or just a trait of older technology?
hifi_dave
03-12-2009, 19:49
4040's did that, it's harmless.
sburrell
03-12-2009, 19:55
Thanks hifi_dave! :)
Rare Bird
03-12-2009, 20:29
4040's did that, it's harmless. DC offset measured is pretty safe but i'm not into it..Next week i'm hoping i've managed to drop the thump.
My new second-hand Aura does the same, so I'm guessing it is old technology generally? :scratch:
hifi_dave
03-12-2009, 23:11
It's not 'old technology', as many modern amps do it. Some designers add in circuitry to mute the 'thump' and some don't as it isn't dangerous or damaging, just mildly irritating to some people.
Thanks Dave - reassuring.
Ali Tait
04-12-2009, 15:15
It's not 'old technology', as many modern amps do it. Some designers add in circuitry to mute the 'thump' and some don't as it isn't dangerous or damaging, just mildly irritating to some people.
That and the fact that it could affect sound quality,so many leave it out.
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