How to reduce treble hiss in a pre-amp?

[Shockwave]

Hey guys.

I am having big problems reducing treble hiss in bass internal Pre-amps. I can get zero hiss when the treble control is set between -15 and 0, But anything above the middle position causes a huge amount of hiss, This hiss stops when i touch the strings. The hiss also stops when i switch to passive mode.

Ideas?

Cheers. Rob.

Edited August 1, 2008 by Shockwave

[Mr. Foxen]

solder a length of wire to a spoon, and a crocodile clip to the other end of the wire, clip the wire to your bridge and put the spoon in your waistband. That way you are always touching the bridge.

[thepurpleblob]

[quote name='Shockwave' post='252978' date='Aug 1 2008, 08:49 PM']Hey guys.

I am having big problems reducing treble hiss in bass internal Pre-amps. I can get zero hiss when the treble control is set between -15 and 0, But anything above the middle position causes a huge amount of hiss, This hiss stops when i touch the strings. The hiss also stops when i switch to passive mode.

Ideas?

Cheers. Rob.[/quote]

Buy another bass.... Which bass is this? I have seen this on a number of older active basses. No amount of checking earths and resoldering joints makes any difference. This leads me to suspect that some (particularly older) preamp designs are just inherently noisy. I notice you have a 'Ray on your gear list. Mine, for example, is deadly silent but a 1990-ish Yamaha TRB4p I used to have was almost unuseably hissy.

[peted]

The fact that it goes away when you touch the strings does point to a grounding issue. Time to check the soldering joints on the electrics. I've also seen some basses which have a wire inside the body going from the bridge to to control cavity for grounding, make sure that this is still attached.

[thepurpleblob]

[quote name='peted' post='254138' date='Aug 4 2008, 09:38 AM']The fact that it goes away when you touch the strings does point to a grounding issue. Time to check the soldering joints on the electrics. I've also seen some basses which have a wire inside the body going from the bridge to to control cavity for grounding, make sure that this is still attached.[/quote]

I've never seen one that doesn't have the bridge earthed (and hence the strings). I think you would know about it if that wasn't there :-) Thinking about it, I guess a bass outlasts most other "domestic" electronics. Twenty year old electronics could easily have dried out capacitors and the like. Depending on what it is, a replacement pre-amp could well be the most cost effective fix if simple checks fail. I suspect somebody's time to investigate could easily exceed that cost.

[warwickhunt]

I've had similar problems in the past (not a Warwick ) and I was driven mad with one particular bass. I coated cavities in copper foil after painting them with screening paint, I earthed and re-earthed everything that could conceivably cause the hiss, I even tried different amps and cabs but I had to just accept that particular bass (a Jazz clone) was never going to be buzz free. I'm not saying that is the case here but be prepared that 'worst case' you may either have to live with it or get rid of the preamp.

BTW have you ensured you aren't in a room with strip-lights or dimmer switches... they can exacerbate the problem.

[peted]

[quote name='thepurpleblob' post='254153' date='Aug 4 2008, 09:46 AM']I've never seen one that doesn't have the bridge earthed (and hence the strings).[/quote]
I did originally type 'all basses should have an earth wire going through the body to the bridge', then I considered that I have only really pulled apart one bass and considered that this might be a sweeping generalisation based on my limited experience. Thank you for clearing this up for me

[The Burpster]

It could just be as simple as hot pick ups and a pre amp.....

Some pups just produce lots of noise when the treble end is boosted. You could try contacting Wizard and see if they could re wind a set for you to get rid of this, OR change teh pre-amp and re-shield as described above which will reduce teh prob as much as you can without changing teh pups.