Switching from Passive to Active gives a loud "crack" through the amp

[Grangur]

Hi there,
I'm getting into playing my Harley Benton Deco Progressiv bass, (only the best quality gear is used here at Grangur Towers). The sound it good and the pre-amp gives a good variation in tone. The problem comes when I switch from passive to active. Each time, if it's not been switched for a while, there is a loud "click" that comes through the amp.

No question it would wake up the audience in a gig situation.

I know I need to fit a capacitor across somewhere to stop this. What I'm hoping someone can help with is:

Where do I fit the capacitor?
What size of capacitor should I get?

The switch is a push/pull on the volume control. Here, curtesy of another BCer, is a pic of the elects cavity.




Or should I really look into getting another pre-amp?

[yorks5stringer]

Leave it on Active, I do as the Passive sound is a bit "meh"?

[Billy Apple]

Do you think that this was why it was sold as deco only? If you're going to spend your time fiddling to try and fix it, you may as well bung a working one in.

[Woodinblack]

Why does something sell as decoration only with an active pre-amp?

Generally you get a thump in these things because it switches both the power to the preamp and the signal output at the same time. I fitted a stinger preamp to a ray and it does that, doesn't matter to me as I would never switch it off, and certainly not while I was playing, but it is just there as a backup. The preamp should have a power smoothing capacitor anyway, if it doesn't then whack a mediumish electrolytic over the power (sort of 10u / 16v, unless you are running 18v!) to take the power surge out, and maybe a capactor on the switch to prevent the surge, or you could ensure the preamp was powered all the time, which would use power even when you weren't using it while it was plugged in, but if there was some reason you wanted to switch when playing you could do that.

[Big_Stu]

[quote name='Grangur' timestamp='1440335030' post='2849867']
Hi there,
I'm getting into playing my Harley Benton Deco Progressiv bass, (only the best quality gear is used here at Grangur Towers). The sound it good and the pre-amp gives a good variation in tone. The problem comes when I switch from passive to active. Each time, if it's not been switched for a while, there is a loud "click" that comes through the amp.

No question it would wake up the audience in a gig situation.[/quote]

I know exactly what you mean, I also wondered whether that crack was damaging my speakers it was so sudden and intense.

Long story short (I hope) I had John Birch build me a custom EB3 about 16 years ago. I wanted it to have an active onboard overdrive like Jimmy Lea's from Slade. Sadly John died before doing that part. His business partner had a go at making the circuit which had the fault you have.
I was told this was down to the switch (iirc) not being self shorting, so that the connection was lost immediately prior to you making the switch passive>active. So the crack is the power surge hitting the circuit. If you had a switch that cuts before the switch over the "crack" is lost in that split second between the contacts. [i](I might have that the wrong way around - but that was the gist of it, it was a long time ago)[/i]

Another guitar tech had a go at it, with the correct switch and as you say a cap somewhere. This got rid of the crack BUT created a massive boost in static and was such a complicated switch system it drank the batteries (I'm talking a new Duracell 9v every gig).

Step in Mr John (JayDee) Diggins, actual builder of Jimmy Lea's bass who had worked for years with John Birch. JD volunteered to duplicate Jimmy's circuit exactly, but as others have said already (as did John) it's only going to work perfectly by going fully active. The circuit he made is tiny, it would fit on a postage stamp - but by God it works - very well - and batteries last for ages - as long as I remember to unjack it after use.

Gratuitous pic of my baby.

Edited September 9, 2015 by Big_Stu

[3below]

Simple low cost solution - pull jack plug partially out of amplifier input. Switch to active or passive. Push jack plug in. Works every time but not ideal if you are doing this mid tune.