Double Bass Help diagnosing AI Contra 310 B distortion problem

[Basschair]

My AI has started to distort at modest volumes, whether pizz or arco. If I bear down slightly, it will at the least sound like it's clipping and at the most completely distort to the point where it sounds like the speaker is flapping (a signal that a cone is busted?).

I am going to call AI tomorrow to get some help with it as well, but am impatient...so I'm hoping to get a few suggestions here as to what it might be. As of last month, loud volumes were no problem with my Realist pickup, either pizz or arco. I had a couple shows where I needed to crank it a bit, but nothing heavy...maybe gain and master at 1:00 on the dial. Over the winter break I got a Schertler Stat-B and started messing with the sound, though again nothing loud. I also ran both the Realist and the Stat simultaneously into the low and hi ins of the AI...something the literature says you can do with no problem.

This past week I started getting the sounds mentioned above in the first paragraph. I thought maybe the Schertler Stat Pre was overloading the AI (as mentioned in previous threads), so dropped the pre's volume down and then upped the AI volume a bit to compensate. Same results. This is with the Stat-B by itself, not with the blending Realist as well. I thought maybe it's just the Stat-B itself not working so well with the AI, so I went over to the Realist...same results.

Again, here's what I'm getting: with either pickup in the "low" input at low volume, if I give strong plucks (not popping of rockabilly, just strong pizz), I get something soundin like a clipping. If I up the volume, it will end up getting a bit worse. If plugged in to the "high" input with the low/high button in either position, the signal distorts at any volume to the point where it almost sounds like the speaker is flapping.

So, AI preamp gone bad? Speaker gone bad? My playing gone bad ?


Another question: any chance the Schertler Stat-B could have caused this?

 

[Bofee]

If you are using a preamp with a battery, this has all the hallmarks of a battery going flat.

 

[presforlife]

I've had distortion problems with Realist from time to time and have found cables need (1/4 in. jacks)need to be wiped off,easy to do and has cured distortion 100% of time.

 

[Basschair]

If you are using a preamp with a battery, this has all the hallmarks of a battery going flat.

You know, I should have thought of that. I did check the battery last week for different reasons, and it's definitely good.

I've had distortion problems with Realist from time to time and have found cables need (1/4 in. jacks)need to be wiped off,easy to do and has cured distortion 100% of time.

I'll give it a shot. Just a good rub with lint-free cloth, or would it need something like isopropyl alcohol in the cloth?

 

[Mark Perna]

I blew the driver in my series II AI Contra once and it sounded a bit like what you're describing. AI was great. At no charge, they sent me a new speaker that I received within a couple of days. It took about 15 minutes to pull the old one out and put the new one in. I was good to go again.

mark

 

[bolo]

I'll give it a shot. Just a good rub with lint-free cloth, or would it need something like isopropyl alcohol in the cloth?

I think the top-of-the-line type choice for a cleaner for cable plugs and pots would be something like what Rob describes below. I've been using a similar DeOx product from Caig, but I trust Rob's advice below is probably an even better choice.

I believe this is the same stuff as Caig DeoxIT D100S, which is what you want to use to clean pots anyway. Make sure you get the 100% solution spray, which is Caig part number D100S-2 or alternatively Caig p/n D100L-25C with a precision needle dispenser. Use this stuff sparingly and very carefully and don't let it get all over the circuit boards and elsewhere in the amp. The same product can also be used to carefully clean the 1/4-inch jacks.

 

[Basschair]

I think the top-of-the-line type choice for a cleaner for cable plugs and pots would be something like what Rob describes below. I've been using a similar DeOx product from Caig, but I trust Rob's advice below is probably an even better choice.

Thanks Bolo (Steve),

I tried a few different cables (all newer/new and gold plated), with the same results. I spoke to a guy at AI this morning (Rick?) and he suggested some things to try to isolate the problem area. It looks like it may either be the preamp or power amp, so I just removed both to ship them back to AI. We shall see...