Genz Benz guys - Neopak help please!

kesslari · #1 05-11-2010, 12:49 PM

My Neopak has been a great and trustworthy little workhorse for quite a while now.

I came home from a gig Sunday, set up (Monday), and noticed a LOT more distortion. I backed down the preamp gain - I'm now getting the same amount of grind at about half the gain (well before the preamp light comes on, whereas before I was set to have my highest transients flash the light).
If I go even a click or two higher than where I am now, a big attack will cause a nasty "farty" distortion, almost a pop.
I swapped out the tube to a new Sovtek - same issue at pretty much the same settings. If I dial the preamp way back, I can crank the power amp quite loud without any distortion artifacts (e.g., much louder overall volume, no bad distortion) so it's not a speaker issue - I can be loud and clean, just not with the preamp dialed up anywhere close to where it was before.

Any thoughts? I've got a gig Thursday, and though I've got a workaround (keep the preamp gain down) and a backup, I'd like to be able to fix this if I can.

fretno · #2 05-11-2010, 01:14 PM

hmm.. we'll my first guess was a tube but you tested that , next guess is a pot , could even be something in it , perhaps wiggle the pot and go full sweep , left to right and back to see if you get any pops or anything odd from the pot .

Rick Auricchio · #3 05-11-2010, 02:34 PM

Have you tested the rig with a different bass?

kesslari · #4 05-11-2010, 02:38 PM

Yes. 3 basses, same result.

hasbeen · #5 05-11-2010, 05:27 PM

have you tried cleaning that jacks...all of them....effects loops etc.?

62Jazzbass · #6 05-11-2010, 05:35 PM

No clue, but I'd like to see what comes of this, since I have the same amp. Subscribed.

agedhorse · #7 05-11-2010, 05:58 PM

By any chance are you using a 12AX7-LPS? I found a very wide variety of operating curves on new LPS's compared with say an -A, this is one symptom of a tube way out of range. Try swapping the tube to a known good -A if you were using an LPS.

Other things that can cause this is for the active/passive switch to hang up in between contacts (usually from shipping/handling), an intermittent effects return jack (internal) bypass switch, a bass with a failing battery, bad speaker cable, failing speaker etc.

If you need additional help troubleshooting, feel free to PM me. We'll get it sorted out.

62Jazzbass · #8 05-11-2010, 09:23 PM

Quote:

Originally Posted by agedhorse

the active/passive switch to hang up in between contacts

This had crossed my mind, but I figured I'd sit back and wait for you to chime in, all things considered.

BTW - Been really happy with my 3.5. I have had people complement me on my tone at several shows since switching to it. I have also found it very adaptable to a variety of rooms/situations. If I was more of a knob twiddler I am sure I could go nuts, as the EQ section is excellent. As it is, I know more or less what I want to be hearing, the amp delivers, and I tweak depending on the conditions.

kesslari · #9 05-11-2010, 11:57 PM

Thanks, all, and esp. the GB guys, for the suggestions. I got in late tonight, will shoot this tomorrow.
First steps - clear the jacks, and make sure the active/passive switch is doing its thing.

The current tube is the stock one. The other tube I have is a new Sovtek - not known good, but brand new. Both behaved the same way.
Battery in the bass is good, and behavior is the same with different basses.

I'll dig into it tomorrow and will report back.

chiplexic · #10 05-12-2010, 06:06 AM

This is exactly what my GK 400rb did . The send jack had lost its springy tension against the tab that returns the unused signal at the jack when not being used . It wasn't dirty, just not making solid contact. I don't know if the Neo-Pak has this design on the send/return, but symptoms are exact. Try running a patch cord from send to return.

kesslari · #11 05-12-2010, 12:50 PM

So here's an update - I'm not sure if this is "fixed" or not.

I plugged/replugged the send/receive FX loop jacks, and toggled the active/passive switch. I am still not up to my previous gain settings before the distortion gets "poppy" but I am closer, or at least I think I am, and I am getting the degree of grind that I want without the transient artifacts. I think it's gig-worthy, but I'll bring my Shuttle 6.0 as a backup.

old hoss, I'll PM you regarding tube sources - as I said, my Sovtek is new but I'm not sure what you mean by -A.

buffordbass · #12 05-12-2010, 12:56 PM

old hoss... I like that, LOL...

BassmanPaul · #13 05-12-2010, 02:25 PM

Quote:

Originally Posted by buffordbass

old hoss... I like that, LOL...

Yes but will the vintage equine like it is the question!

Paul

Rick Auricchio · #14 05-12-2010, 02:29 PM

Clear the jacks again, but this time spritz a little contact cleaner on the plug first. Don't spray into the jacks.

Do all the 1/4" jacks, even the input jack. Just in case there's some switching in the input jack too.

agedhorse · #15 05-12-2010, 11:22 PM

Quote:

Originally Posted by BassmanPaul

Yes but will the vintage equine like it is the question!

Paul

Oh Paul, I've been called a whole lot worse... in the last 24 hours even

chiplexic · #16 05-13-2010, 06:23 AM

What if you just leave the cable looped/plugged from the send -to-return and try playing with it like that.

If you plugged and unplugged a cable into them and saw a change maybe it's pointing to them as the culprit.

agedhorse · #17 05-13-2010, 09:21 PM

Quote:

Originally Posted by chiplexic

What if you just leave the cable looped/plugged from the send -to-return and try playing with it like that.

That would work fine. In fact dummy TRS insert plugs with T connected to R is not an uncommon cheat to the road to bypass inserts on mixers.

ErnieD · #18 05-14-2010, 12:11 AM

good answer Pony Boy....

Yeah I know your not fond of that lil user name either. Hey I coulda just posted my avatar pic, woulda been open season on ya.

But really guys, great replies here to help out the OP. kesslari, pls post back and let us know what the final fix was, sounds like you got close. You got some real good suggestions here, let us know if any of em worked.

I have 3 different 12AX7 pre-amp tubes I bought and been meaning to run em thru my Neopak, just to see whut-whups. I just dont want to open her up and maybe muck something up in the process. Its fine the way it is, so now I got 3 spare pre-tubes if I ever need em.

kesslari · #19 05-14-2010, 09:52 AM

Well, the gig last night went fine, NeoPak kicked booty, never had to plug in the Shuttle.
I had plenty of volume. I think that for now, the solution is to keep the pre down a little bit. That definitely did the trick, with no degradation of the sound whatsoever over the course of the night.

agedhorse · #20 05-14-2010, 03:28 PM

Quote:

Originally Posted by kesslari

Well, the gig last night went fine, NeoPak kicked booty, never had to plug in the Shuttle.
I had plenty of volume. I think that for now, the solution is to keep the pre down a little bit. That definitely did the trick, with no degradation of the sound whatsoever over the course of the night.

Cool.