Peavy Amp feedback

Carter York · Post by **Carter York** » 8 Jul 2002 4:58 pm

Hey y'all, (can't edit the subject, but I do know how to spell Peavey!)

I've been reading some of y'all use the Peavey Classic 50 Twin (2 12's) and I use one as well, but am having a problem with feedback.

Using the normal input, normal mode (not 'lead') and volume, presence, treble,
mid, bass, and (output) volume all at 50%, I can start to play, and don't notice anything during play, but after I stop playing, the amp has a loud hum, that only fades away by turning the volume(s) down significantly. This is with a 6string Gibson SG, and with a 6string lap steel, both with their volumes around 80-90 %.

Is this simply a settings problem? Could it be something with the amp? Could it be anyone's equipment near me? It's been problematic as of late trying to play music with other folks.

Thanks in advance for any ideas,

Carter<FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Carter York on 08 July 2002 at 06:00 PM.]</p></FONT>

Donny Hinson · Post by **Donny Hinson** » 8 Jul 2002 5:13 pm

That sure sounds like a microphonic preamp tube, Carter. That amp has two 12AX7's. Try switching them, and see if the problem is still there. Generally, if you tap the tube with your finger, and you hear a loud "bong" in the speaker, the tube's microphonic, and should be replaced, but just swapping them may alleviate most of the problem.

If not, then you have to replace the bad one.

Mike Brown · Post by **Mike Brown** » 9 Jul 2002 6:08 am

Thanks for your help Donny. It sounds like a preamp tube(12AX7) problem. Try swapping the 12AX7's around and see if the problem moves to the other channel. This will tell you if its a tube or not. Make sure you know what tube is moved where.

Mike Brown
Peavey Electronics Corporation

Carter York · Post by **Carter York** » 9 Jul 2002 7:14 am

Thank you Donny and Mike for both of your replies, I'll see what happens when I swap the tubes out. Not having done that before, are there any tips or tricks that I might find helpful, or any pitfalls I might avoid?

Also, is it imperitive that I replace the bad tube (assuming one is bad) with the exact same type?

Thanks for the info.

Carter

Mike Brown · Post by **Mike Brown** » 9 Jul 2002 8:55 am

Yes, replace with the same 'model', but not necessarily the same brand. Also, make sure that the amp is unplugged when changing out tubes.

Carter York · Post by **Carter York** » 9 Jul 2002 9:31 am

Thanks again Mike,

I just did a quick search and found several dozen makes of the 12AX7, is there one that is recommended, or any that should be avoided? 7 bucks up to 120 is quite a range.

Thanks,
Carter

Jon Light (deceased) · Post by **Jon Light (deceased)** » 9 Jul 2002 10:38 am

Carter--doing a forum search ought to show you some tube preferences. Be aware that for every person that says that such and such brand sucks, there's someone else quite happy with it. You shouldn't need to spend more than the low end--$7-$10. The high end is NOS stuff--new old stock. That is money to be spent only when your ears tell you it's worth the money. Don't let someone else's ears spend your $$.
One thing that spending a bit more can get you, from a reputable dealer, is a tube that has been tested for microphonics. Some brands have very high reject rates and it can be worth dealing with someone who will cull out the losers. Hopefully someone else can give you good leads on dealers they've had good dealings with.