Delay on loudspeaker switch on.

[lykkedk]

I was hoping anyone outthere could help me with this.

I have recantly finished my Leach amp 4.5, but when I turn it on, my 10inch basse's make a little move in, and then out again.
When i turn off, it's the same, just not so much.
I'am sure it's because of the cap's im the PSU, but i would like to awoid this THUMB.
I was thinking on a circut with an ne555 or simmular, an two relay's, one for each channel for cutting the loudspeaker connection immidiatly when turn off, and delayed when turn on.
The cap's I'am using is 4x10000uF, but I'am planning to use 8x10000uF in the future.

[BrianGT]

Originally posted by lykkedk
I have recantly finished my Leach amp 4.5, but when I turn it on, my 10inch basse's make a little move in, and then out again.
When i turn off, it's the same, just not so much.
I'am sure it's because of the cap's im the PSU, but i would like to awoid this THUMB.

I had some thump from mine when I first built it, so I put bleeder resistors on my power supply caps, and I don't have problems now unless I turn it off, then immediately turn it back on. It didn't seem to effect the performance at all.

Here is a pic:

More pics at:
http://brian.darg.net/leachamp-2channel/

--
Brian

[lykkedk]

Yep I know about the bleeder resistors, but how do i calculate the size for 4x10000uF ?
And wattage to ?

Anyway I would like to make this circuit to just make sure, also because I'am building this Balanced Zen Line Stage, whitch has no protection for thumb's on turn on.

I was thinking of making one power-button, at this pre-amp, which also turn on the Leach amp (delayed), so i would be 100% sure -

Allready destroyed one 10inch bass some time ago, with another experiement

[fcel]

Jesper,

I guess the easiest way is to install Velleman KV-K4700U in your power amp. Here is what it looks like http://www.audioxpress.com/bksprods/kits/kv-k4700U.htm and it provide DC protection too. I install them in my BOSOZ and there is no more turn/off thump. I'm sure there are other better ways but I don't know how.

Another way is to wait for Brian/Jordan design Relay-based passive volume control project I'm hoping their design has capability to short the output relay to ground at turn on/off to avoid turn on/off thump.

[BrianGT]

Originally posted by fcel
Jesper,

I guess the easiest way is to install Velleman KV-K4700U in your power amp. Here is what it looks like http://www.audioxpress.com/bksprods/kits/kv-k4700U.htm and it provide DC protection too. I install them in my BOSOZ and there is no more turn/off thump. I'm sure there are other better ways but I don't know how.

As for the kit, it says:
Supply voltage: 220V AC

Did you have any problems with this?

As for the project that Jordan and I are working, it shouldn't be difficult to add the turnon mute.

--
Brian

[jleaman]

i have that problem, BUT solved now. im building a simple circuit for turn on thump. I'm using a murcury wetted relay in each of my mono blocks that i built witha simple timer ic 555 with a 10 second time delay that way there is time to let the amp settle down.

J'

I dunnno what im going to do about my aleph's i think i should do the same.

[fcel]

Brian ... even though it says 220v, it is 120v transformer when I got the kit.

[SkinnyBoy]

MY amp has a relay.. lol... and for some reason when I take out one of the poweramplfier modules (or when it stops working) the delay to connect the output to the speakers is longer.. :P lol

[RichardH]

JasonL - that circuit you mentioned for delay sounds perfect for me - can you post a few more details?
I'm running a computer straight into dedicated power amps in a home cinema system, and am getting a horrible noise through the speakers when the PC is powered on. I'd been thinking of running a relay based mute switch, with the relays powered by a 5v feed from the PC, (so the amps, if on, remain muted when the PC is off) but need that delay.

[daatkins]

I have a schematic for a speaker delay circuit on my website (go right to the bottom):
http://www.apcl43.dsl.pipex.com/proj_subamp.htm

It delays connecting the speakers when it detects the AC from the transformer secondary and disconnects the speakers immediately when the AC is switched off.

You can use almost any op-amp you like although I'd avoid using NE55532; to quote Doug Self:
"The inputs are connected together with back-to-back diodes for reverse-voltage protection; and should not be forcibly pulled to different voltages. The 5532 is intended for linear operation, and using it as a comparator is not recommended. "

Nice one,
David.