Express 5/50 high pitch feedback

[donnyb]

Hi to All. I bought this combo amp new about 3 years back and just replaced the 2 x power tubes with JJ6L6GC's. Have not changed any of the original pre amp valves.

I only use the 5 watt setting, mic'd up with flat EQ to FOH via a Shure 57 and the desk. The amp is on a stand facing back up to me monitor -like, not facing the audience (band leader wants stage noise down as low as possible).

When I first plugged into it at home with the Strat (USA 60th Anniversary model), I noticed it had a harsher tone, not bad, but not what I was seeking for overdriven solos. But really nice in Clean mode. Anyway, gigged with it in a basketball stadium event earlier in the week, and it was ok , even perhaps better at cutting through the mix when needed. Hall had really bad acoustics.

Last night, gigged in a building with great acoustics, volume levels low, switched to "burn" for a solo (like I had done in the stadium), and nearly had my head blown off by high microphone - like feedback. Only happens on the Strat bridge PU and with the LP humbuckers.

I had to stand behind the amp when doing solos to stop it, which was not ideal !

Otherwise the amp sounds quite OK, but why would the 2 different gig venues so drastically affect the presence or absence of this feedback ? Is there hocus pocus co-incidences happening here? Like....have I frightened the 3 year old original pre amp tubes and fried one that was about to go anyway? I got the JJ6L6 tubes from Eurotube, and they were a matched pair to suit this amp. Good service BTW.

Any insights appreciated, as I cant live with it the way it is. Incidently, I was and still am seeking a more Santana-like tone for distortion solos. Thanks for any help,

Don in Australia.

 

[donnyb]

UPDATE !! The amp does not do it minus my Morley Wah/Volume pedal and Electro Harmonix small stone phaser in line to the amps input.

Just plugged it in, no pedals, turned the gain in the burn mode even more than normal.

Both gigs I used both pedals, in the same order viz., Morley wah/volume first, phaser second. Connected together by a solid double-ended jack. Both powered by 9v power supplies.

The only thing different could be the leads I used between the phaser and the Mesa's input and the guitar to the Morley Wah/Volume pedal AND the power supplies to these pedals may have been opposite for the 2 gigs.

Any tech heads out there that might recognise what combinations I had here that may have caused the un-playable with feedback?

Thanks, Don

 

[a2dconverter]

Hey donnyb,

By chance, are you using one of those Planet Waves guitar cables with one unshielded (guitar) end?

that cable should only be used between you guitar and wah/phase....

if you place that cable between your wah and amp, you can pickup and generate all kinds of strange noise.

If this is your problem, you'll need a cable that is shielded on both ends.

I hope this helps

seeya

Joe

 

[pusher]

Well,

It seems that you really have all the information you need to start trouble shooting the issue yourself. Replace the leads and power supplies one by one, or add them back in one by one, until you isolate the problem.

It's just a systematic approach is all you need at this point.

Cheers,

pusher

 

[donnyb]

Hi again - just back from a trip. Yes Mark 1 - I use those planet waves leads you mention - I have 2 of them. Thanks for that - it will give me a good starting place and save a lot of time if its the culprit. I have never heard of that before, so will follow this up with a post with the results in a couple of days.

 

[jazzin335]

I DO A PROBLEM WITH REVERB WILL DO THAT. HAVE YOU UNHOOKED?
I HAVE A MONSTER EXPRESS PROBLEM TOO.

 

[donnyb]

OK, yes, I do use reverb a bit, but never had any issues before I changed the power tubes. Will get the feedback going again and cut the reverb off with the footswitch and see what happens. What is your 'monster problem" ?