Sound difference between active and passiv

bassomane · #1 06-19-2007, 04:26 AM

I´ve got a new Tribute L-2500 and I am wondering if there is a sound difference between the active and passive position using a short cable. I cannot hear any sound difference.

Active w/treble boost works well, and is low impedance as it works well on the laptop input. In passiv and active mode I get no sound out of the PC, which is strange. The active mode should be an impedance transformer making the output sigal low impedance. Swapping out the battery makes the bass sounding the same in aktiv and passive mode. The treble boost mode does not work (that´s ok).

Is my bass defect or is that normal?

tornadobass · #2 06-19-2007, 08:21 AM

Something doesn't sound right. The passive mode should sound warmer and a bit diffused. Active should sound tighter and more focused, and a bit brighter. Treble boost is the same, but brighter yet. No reason why you should have no sound in your computer for some settings.

Also, the active is not a transformer but a buffer preamp.

bassomane · #3 06-19-2007, 08:31 AM

I think there must be a problem with the passiv/activ/activ w treble switch. Position 1 & 2 are passive, 3 is activ. Maybe a defectiv switch or wrong wireing.

lug · #4 06-19-2007, 09:04 AM

Active mode is just an IC line driver that boosts the signal power. Passive totally bypasses the active electronics and takes the output from the passive tone controls to the output jack. Does this just happen with the PC or also with an amp? (this would be increadably wierd) If you get no output at any time from passive, it's definately a wiring problem. There are schematics on G&L's page under Support.

bassomane · #5 06-19-2007, 09:19 AM

With the amp everything sounds ok. Only the sounds are passive/passive/active with treble.

Quote:

Active mode is just an IC line driver that boosts the signal power

This is was I wanted to know. The active signal should be hotter brighter and tighter, is it right? The test on the PC told me that position 1&2 are passive.

I have already contacted the distributor. Tomorrow the tech will call me.

PSPookie · #6 06-19-2007, 09:55 AM

Depnding on your settings, the passive & active modes can sound quite similar. Active w/ treble boost is a more noticeable difference.

Try playing it through your amp a bit more and see if you can discern a difference. To my ears there is more of a tonal difference between passive & active when the bass is in parallel mode.

bassomane · #7 06-19-2007, 10:06 AM

So now I am a little confused. You say there is only very little difference betwenn active and passive. Lug said active boosts the signal.

Can anyone take the battery out of the bass and tell me what he is hearing? Do passive and active sound the same (no buffering) or do you get no signal from the active one?

sunbeast · #8 06-19-2007, 10:21 AM

Active gives a HUGE boost in signal...through my computer I can set the input volume for passive and if I switch it active the sound becomes indescernible fuzz (overloading the input). I accidentally did it at a show one time (I don't know how I managed!), and I pretty much drowned out the guitars! It sounds like a simple wiring problem- it does happen with G&Ls sometimes, my US L2500 was wired wrong when I bought it new. You could likely fix it yourself in a couple minutes...

Karl

spideyjg · #9 06-19-2007, 10:28 AM

Take out the battery, now only one position of the rear switch will get you output. That position is the passive one.

Put the battery back in and try the other 2 positions of that switch, the middle position should be active, and the one opposite passive should be active with treble boost.

Active should be very similar to passive just louder. There are some subtlties but overall pretty similar. Active w/ treble boost should be quite a bit brighter.

Jim

bassomane · #10 06-19-2007, 10:41 AM

I took out the battery and got the similar sound on passive and on active. On active with treble boost I´ve got no sound. Seems like a wireing problem..?

spideyjg · #11 06-19-2007, 10:49 AM

Quote:

Originally Posted by bassomane

I took out the battery and got the similar sound on passive and on active. On active with treble boost I´ve got no sound. Seems like a wireing problem..?

Sounds like it. With no battery only one position of that rear switch should give you sound. More than one works with no battery, something is hosed up.

Jim

bassomane · #12 06-20-2007, 06:44 AM

Hallo guys! I have solved the problem. The yellow (preamp output) and the brown (passiv output) cable have been mixed up.

Two days search for the wiring diagram and 5 Minutes work for the solution. But it worked and so thanks to all TalkBass Members providing support.

sunbeast · #13 06-20-2007, 02:02 PM

Oh yeah- shoulda posted the link to the wiring diagram! oops!

bassomane · #14 06-21-2007, 12:04 AM

Sorry here is the link:

http://www.kbconsulting.org/images/l...ng_diagram.pdf

sunbeast · #15 06-21-2007, 02:32 AM

Quote:

Originally Posted by bassomane

Sorry here is the link:

http://www.kbconsulting.org/images/l...ng_diagram.pdf

Oh no- I meant that I didn't think to post it when you originally described the problem. Someone did it for me when my wiring was off- the least I could have done was pass it on!

Thanks for posting it again for folks though- it is a useful resource!

Karl

tornadobass · #16 06-21-2007, 08:00 AM

What's interesting about the schematic is that the treble boost, like the other tone controls, is also passive. Also, I'm having trouble following the signal chain from pickups to preamp...is that part drawn correctly?

bassomane · #17 06-22-2007, 01:06 AM

No, the treble boost is activ. You switch it on with the yellow wire to SW on the preamp. The treble boost is located on the preamp. The schematic for the preamp you´ll find here:

http://www.glguitars.com/frameset.htm

tornadobass · #18 06-22-2007, 09:20 AM

The way I'm reading both the G&L schematic and the one that was linked earlier in this thread, it looks like the treble boost circuit just involves switching a resistor. The yellow wire is tied to the middle and left terminal in the second diagram. In the G&L diagram, the circuit is shown off to the side, adding in (or subtracting) a 10 meg resistor to the 10k resistor.

Can somebody help out here who's better at reading schematics than I am?

DavePlaysBass · #19 07-14-2007, 10:46 AM

In treble boost mode, a resistor is switched into the feedback network of the preamp. This gives the preamp more treble and it peaks at a higher frequency than normal active.

The confusion is that point "3" on the Treble Boost Switch Network should be labeled as point "5" on the above schematic. If you look at the generation 1 schematic on the G&L site it shows you how the three way preamp switch works. The schematic you reference has been wrong for years but has not been corrected.

Dave

tornadobass · #20 07-14-2007, 06:08 PM

Thanks for the explanation, Dave!