Sadowsky onboard Preamp output in Active vs Passive Mode

JFN · #1 06-22-2009, 01:18 PM

I just had a Sadowsky onboard preamp with the Vintage Tone Control installed in my Am Dlx P Bass last weekend. The wiring is not quite right since active mode is shorting out and sounds scratchy when the stack knob is jiggled. My tech will fix this for me of course, and I used it in passive mode at a gig Saturday with no problem.

However, the output level when switching to active mode gets VERY EXTREMELY load compared to passive mode, so much that I have to cut the gain in half or more on my Little Mark II when switching.

I realize this could be the result of the installation problem, but if this huge difference on output level is going to remain after the wiring is corrected, I think switching from active to passive in a live setting is going to be nearly impossible, and I think I might be better off just leaving the bass passive and returning the preamp.

Can anyone with a Sadowsky on board pre and VTC comment on the output levels when switching between active and passive modes. Thanks for your help.

John

mikezimmerman · #2 06-22-2009, 01:44 PM

In my experience, there was little or no difference in the output level between active and passive with the controls set flat. However, the Sadowsky preamp is boost-only, so to get a "flat" signal you have to have both the treble and bass controls turned all the way down (counter-clockwise).

The treble and bass controls can potentially give a LOT of boost, though. How do you have your controls set?

Mike

JFN · #3 06-22-2009, 01:53 PM

The stack knob Hi/Low set was turned down all the way and the difference in output was huge. However, my tech also wired the pick up pan knob backwards from where you would normally have the front vs back pickups. So maybe full off was actually full on for the active stack knob set.

He's a great guy has and has done good work for me before, I know he'll take care of it, but I was concerned about what to expect when it gets wired correctly.

John

mikezimmerman · #4 06-22-2009, 02:12 PM

On Sadowsky basses and the pre-wired Sadowsky preamp, the blend knob is wired backwards from most blend controls. That may not be relvent if your tech wired everything up, though.

The simple way to confirm whether or not your tech wired the treble and bass controls backwards would be to turn them the other way and see what the results are...

Mike

JFN · #5 06-22-2009, 03:51 PM

I just checked the wiring diagrams on the Sadowsky site and it looks like it is backwards from I would expect it to be (i.e. turning it full up, like volume pot going to 10, should give me the neck pickup; and the equivilant to off on a volume pot should give me the bidge pick up. It currently behaves the reverse of that.

If that's the "Sadowsky Way" fine, I'll just have my tech switch the connections when he fixes the active preamp wiring.

The more I think about it, I think the short in the wiring may have the caused the treble and bass to engage in a fully cranked state. I'll know for sure this weekend.

John

bassgod0dmw · #6 06-23-2009, 07:20 AM

Quote:

Originally Posted by JFN

I just checked the wiring diagrams on the Sadowsky site and it looks like it is backwards from I would expect it to be (i.e. turning it full up, like volume pot going to 10, should give me the neck pickup; and the equivilant to off on a volume pot should give me the bidge pick up. It currently behaves the reverse of that.

If that's the "Sadowsky Way" fine, I'll just have my tech switch the connections when he fixes the active preamp wiring.

Turning it clockwise (turning it full up like a volume pot going to 10) will give you the bridge pickup. Obviously, turning it counter clockwise (like turning a volume pot off) will give you the neck pickup. That would be the Sadowsky way...kinda backwards, but you get used to it.

As for your original question: In passive mode mine is slightly quieter, but it's not an extreme difference like you mention.

**KJung** · #7 06-23-2009, 08:12 AM

There is a minor output boost built into the Sadowsky preamp in active mode, even with the tone controls 'off'. Roger considers the passive mode a 'safety option' for his basses (i.e., they are voiced to always run active, with the bypass there only in case of battery failure).

Unfortunately, there is no volume trim pot with the Sadowsky preamp (that I'm aware of anyway) to set the preamp gain to unity with the passive output. If you have the bass boost engaged slightly like most who run these preamps, there will be a very noticable difference between the active and passive level.