I just got this idea.Istead of using a relay and all other stuff.Can I connect a simple spst switch on the speaker wires.I will first turn on the amp wait for some time say 10sec and then turn this spst switch on the speaker line.I think this is a simple solution.
Any drawbacks with this set up??I am sure it may add some series resistance on the speaker wires.But I think it may not matter much.
Any drawbacks with this set up??I am sure it may add some series resistance on the speaker wires.But I think it may not matter much.
really??
I am sure many pple would have already thought abt this .This idea just popped out of my head.There should be some drawbacks with this.Can anybody point out the draw backs please.
I am sure many pple would have already thought abt this .This idea just popped out of my head.There should be some drawbacks with this.Can anybody point out the draw backs please.
like any time anyone else has to use your system. or you upgraded and decided to sell it
you would be suprised how hard "turn on power switch, turn on speaker switch 10 sec later" could be.
a simple capacitor, resistor and relay, its still a contact that opens and closes, and just a couple of other components that are not in the signal path, not to mention relays tend to be a lot better made than a lot of switches on the market(depends what you use of course).
you would be suprised how hard "turn on power switch, turn on speaker switch 10 sec later" could be.
a simple capacitor, resistor and relay, its still a contact that opens and closes, and just a couple of other components that are not in the signal path, not to mention relays tend to be a lot better made than a lot of switches on the market(depends what you use of course).
One drawback: Lazyness
First you switch on the amp, then . . . wwwwwwaaaaaaaaiiiiiiiiiiitttttttttt fffffffoooooorrrrrrrr ttttttteeeeeennnnnnn . . . . (oh, you get it ;-) seconds and then switch on yet another switch. Yes, it is do-able, but for most people (i believe) it will become a nuisance. For you and any other hifi-nerd it is no trouble, but try and ask your spouse . . .
One thing: The switch must be one that can handle a lot of current.
First you switch on the amp, then . . . wwwwwwaaaaaaaaiiiiiiiiiiitttttttttt fffffffoooooorrrrrrrr ttttttteeeeeennnnnnn . . . . (oh, you get it ;-) seconds and then switch on yet another switch. Yes, it is do-able, but for most people (i believe) it will become a nuisance. For you and any other hifi-nerd it is no trouble, but try and ask your spouse . . .
One thing: The switch must be one that can handle a lot of current.
Hi rs1026,
actually there is a good advantage to use the switch rather than relay...
You can disconnect the speaker before you turn off the amp.
If you search around the forum, you will find that beside turning on thump, there is another speaker thump that may happened: when you turn of the amp.
LM3875 datasheet say that it has undervoltage voltage protection, but I wonder why speaker thump also happen during turning off the amp.
REgards,
---
David
actually there is a good advantage to use the switch rather than relay...
You can disconnect the speaker before you turn off the amp.
If you search around the forum, you will find that beside turning on thump, there is another speaker thump that may happened: when you turn of the amp.
LM3875 datasheet say that it has undervoltage voltage protection, but I wonder why speaker thump also happen during turning off the amp.
REgards,
---
David
I've had thump off problems since I built my first GC. I have considered some options and one was to use a relay in front of speakers. But I didn't want any unnecessary parts in signal path. The power of GC is in it's simplicity and we should leave it that way.
Anyway, one day I was making front plate for my chasis and have put a power on LED on it. I've had only those transparent (3mm) LED's in my drawer at the time. The one which lights red when turned on. I've basically put an resistor in front of LED without any calculation and it came out that LED lights pretty strong but I didn't have time to change this at the moment.
When I connected speakers I have noticed that thump off's are gone. Power LED is the only thing I have changed in whole amplifier, so my only explanation is that this LED consumes everything what's left ine elco's.
I have noninverted 3875 version with Pedja regulated PSU.
Tomislav.
Anyway, one day I was making front plate for my chasis and have put a power on LED on it. I've had only those transparent (3mm) LED's in my drawer at the time. The one which lights red when turned on. I've basically put an resistor in front of LED without any calculation and it came out that LED lights pretty strong but I didn't have time to change this at the moment.
When I connected speakers I have noticed that thump off's are gone. Power LED is the only thing I have changed in whole amplifier, so my only explanation is that this LED consumes everything what's left ine elco's.
I have noninverted 3875 version with Pedja regulated PSU.
Tomislav.
Find out if there is any cheap 'power-on delay' relay available in the local market. U will be fed up with the switch
gajanan phadte
gajanan phadte
hmm
If I use a power on delay relay then how to eliminate power off thump??That way using a switch may be better because it(I) can control both power on and power off thumps 😉
If I use a power on delay relay then how to eliminate power off thump??That way using a switch may be better because it(I) can control both power on and power off thumps 😉
Perfect!
I tried a spst switch just now.It works perfectly well!! No turn on thumps or no turn off thumps!!. The resistance of the switch is 1.5ohms so its like I have added 1.5 ohms in series with the speaker cables.I dont find any degradation in sonic qualities by adding this switch.
Initially capacitor was draining through the speakers when i switched of the amp.Now that problem is also solved.I am quite happy with this solution.
I tried a spst switch just now.It works perfectly well!! No turn on thumps or no turn off thumps!!. The resistance of the switch is 1.5ohms so its like I have added 1.5 ohms in series with the speaker cables.I dont find any degradation in sonic qualities by adding this switch.
Initially capacitor was draining through the speakers when i switched of the amp.Now that problem is also solved.I am quite happy with this solution.
dc offset
I forgot to mention in my previous post.I measured the DC at the output of the amp.Basically I connected a multimeter to the output.Each channel measured 0.5mV DC.
I forgot to mention in my previous post.I measured the DC at the output of the amp.Basically I connected a multimeter to the output.Each channel measured 0.5mV DC.
the LM3886 and LM4780 have mute functions which can be slow-started -- see the ongoing thread on "Soft Start LM3886" -- you can also soft-start if you use an inrush current limiter -- the cold resistance is such that the power supply starts with an "RC" calculated delay.
Don't use too high an "On Resistance" since power supply regulation will be adversely affected., and will motorboat will the undervoltage protection is cycling on and off.
Don't use too high an "On Resistance" since power supply regulation will be adversely affected., and will motorboat will the undervoltage protection is cycling on and off.
I've used the "delayed" relay in all the amps I made and all of them are silent at turn on and turn off.
turn off thumps are caused by the main supply caps draining and that lasts a few seconds at turn off. the relay opens in only a few msec so that's already too fast. if you get a thump right after turning off even if the caps haven't discharged, you're getting a pulse from the transformer primary (that happens if you don't use a snubber circuit across the primary winding).
the separate switch for the speakers and power may be fine today, I'll guess that by after a few weeks or months, you'll get tired of having to turn on two switches.
if you really want to disconnect the speaker after turning the amp off, use a programmable IC to control power and speaker switching.
turn off thumps are caused by the main supply caps draining and that lasts a few seconds at turn off. the relay opens in only a few msec so that's already too fast. if you get a thump right after turning off even if the caps haven't discharged, you're getting a pulse from the transformer primary (that happens if you don't use a snubber circuit across the primary winding).
the separate switch for the speakers and power may be fine today, I'll guess that by after a few weeks or months, you'll get tired of having to turn on two switches.
if you really want to disconnect the speaker after turning the amp off, use a programmable IC to control power and speaker switching.
djQUAN said:
the thump is also caused by the capacitors draining at different rates -- I was wondering whether it might not be better to switch some "R" in -- i.e. a DPDT relay
you need a rather beefy relay to do this.
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