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Eliminating amp 'bump' on start-up?

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Just a quick one... I recently acquired a Hotone Nano Legacy Thunder Bass (5w class A micro amp).  I won't go into the detail here, but it's an extraordinary little thing - phenomenal preamp!  However, I notice that there's quite a loud (not mad but unusually noisy) 'bump' from the speakers as I turn it on.  I know this bump isn't unusual in general and I've had it from various TE, EBS and other SS amps.  Does anybody know of a way around it?  I've tried turning on the amp and then connecting the speaker cable to the cab - 'still get the bump.  Maybe there's some trick that I've missed?  Any advice would be very welcome 

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....if you don’t already do this.....I don’t know this amp you have but before switching the amp on, turn the amps output volume to zero..

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Ha ha. Just as I was reading the start of that I was thinking of Trace Elliot. My old V8 used to give a heck of a thump on start up. I always assumed it was the surge of electricity through the amp on turn on and it’s surprising that you still get it when connecting the active amplifier to the speaker. 

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2 minutes ago, mybass said:

....if you don’t already do this.....I don’t know this amp you have but before switching the amp on, turn the amps output volume to zero..

I maybe mistaken, but I don’t think it’s a volume or gain thing. I tried that method with my V8 and it didn’t work, but yes, worth a try.

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Thanks both - yes, I always have both gain and volume on zero before switch-on.  And yes, TE - wow, quite a serious bump from pretty much all the amps I've had - and that's a good few!

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I've always figured it's a factor of a given design. If there was a simple solution, it would have been designed out at the R&D stage.

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2 hours ago, John Cribbin said:

I've always figured it's a factor of a given design. If there was a simple solution, it would have been designed out at the R&D stage.

I don’t know for sure but suspect there’s something in this (and the Hotone is a very inexpensive unit). Just wonder if anybody has an easy workaround/fix?

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The 'thump' comes from the power supply turn on and power amp so turning the gain / vol down doesn't really affect that. But it will stop noises when plugging / unplugging bass of fx chain into the preamp input.

You will probably get a 'noise' if you plug the speaker jack (?) in as well as there is no existing 'Ground' connection and with a jack connection (as opposed to eg a Speakon) there is a sequence of connection as the plug is inserted.

HiFi amps often implement 'anti-thump' by waiting a few seconds after turn on (when the psu has stabilised) then switching the 'live' speaker signal via relay - the 'Ground/Black' signal is already connected.

Other circuit techniques are based around controlling the rise time of the voltage rails to avoid fast transients.

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1 minute ago, rmorris said:

The 'thump' comes from the power supply turn on and power amp so turning the gain / vol down doesn't really affect that. But it will stop noises when plugging / unplugging bass of fx chain into the preamp input.

You will probably get a 'noise' if you plug the speaker jack (?) in as well as there is no existing 'Ground' connection and with a jack connection (as opposed to eg a Speakon) there is a sequence of connection as the plug is inserted.

HiFi amps often implement 'anti-thump' by waiting a few seconds after turn on (when the psu has stabilised) then switching the 'live' speaker signal via relay - the 'Ground/Black' signal is already connected.

Other circuit techniques are based around controlling the rise time of the voltage rails to avoid fast transients.

I forgot about that delayed / anti thump' switch, my Markbass has this, it takes a few seconds before the volume actually kicks in.....More expensive amps maybe?

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My Bergantino comes with instruction to always switch on the mute button before switching off. A good simple idea - if you have a mute button. 

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4 minutes ago, Bobthedog said:

My Bergantino comes with instruction to always switch on the mute button before switching off. A good simple idea - if you have a mute button. 

I don’t think that amp does and I think Loz would have sussed that out if it did 😜.

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1 hour ago, Bobthedog said:

My Bergantino comes with instruction to always switch on the mute button before switching off. A good simple idea - if you have a mute button. 

Really good practice - I always do this with amps with a mute feature

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1 hour ago, hiram.k.hackenbacker said:

I don’t think that amp does and I think Loz would have sussed that out if it did 😜.

It really is a dead cheap little thing, so no mute, but it does sound wonderful

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2 hours ago, hiram.k.hackenbacker said:

I don’t think that amp does and I think Loz would have sussed that out if it did 😜.

I was more saying that is how Bergantino works it, not that Loz may have missed it on his kit.

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3 hours ago, mybass said:

I forgot about that delayed / anti thump' switch, my Markbass has this, it takes a few seconds before the volume actually kicks in.....More expensive amps maybe?

Well it adds a bit of cost all other things being equal. Not really much in component costs but when manufacturing and retail margins multiply that by whatever it can be a bit off a price differential.

Various degrees of sophistication. I guess we've all experienced the amp setup where there's a noticeable downward frequency sweep then a worrying noise when you turn the thing off ...🙄

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I put a twin delayed relay in my EBS Taurus 240 combo as it's been fully serviced by EBS and got new speakers too. I was fed up by this huge, totally normal, starting plop and singing capacitors when turning it off.

Now, it's almost dead silent at starting and "stopping" as the delaying relay is effective both ways (instant speakers cut when turning off and delay when turning on).

It's this and it runs on common AC power, plus, as it's stereo, it can cut the tweeter too :

https://www.audiophonics.fr/en/softstart-protection/amplifier-speaker-protection-module-220v-30a-p-13597.html

You can find it almost anywhere on the Internet.

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Thanks Morris and Helzero - some extremely useful detail and ideas here.  Given the size of the Hotone, fitting the card to the amp would be problematic, though what an excellent idea.  I hadn't seen the protection module previously but a great solution for standard-sized amps

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