Express Clone With Howling Feedback - HELP!!!!

[geetarpicker]

If you could walk up to the cab with all it's knobs dimed and your guitar up without string feedback your amp wasn't right in the first place, not even close! However what the amp should not do is feedback on it's own with the guitar turned totally off. Perhaps the amp was actually not right prior to tweaking it (weak gain issue) and now it is actually working as designed.

[bluesky636]

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[bluesky636]

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[bluesky636]

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[geetarpicker]

Ok, if I was to set my original Express to your settings there is NO way it wouldn't induce the strings into howling feedback even from across the room with the guitar turned up and unmuted. Maybe with weak pickups it might take a few seconds to ramp up maybe, but with humbuckers it would probably be immediate.

Presence = 6
Bass = 4
Mid = 5 to 8
Treble = 4 to 6
Volume = 5

Sounds like your amp was unhealthy prior and is actually now working like it should. Just my $.02

It's all probably now up to muting, and working the guitar knobs to control it.

[romberg]

This then sounds completely normal. The whole thing is a big positive feedback loop. Strings -> pickups -> amp -> cabinet -> air -> strings.

It is going to feedback unless you break the air-> strings connection. There are many guitar players who actually try to make this connection stronger.

Of course the whole thing is also a mess of resonant circuits and different frequencies will be less damped and thus feedback more. My guess is that your recent changes in the amp (heck even where you sit) modified these damped frequencies. So, now it is more touchy than it was before.

Like Glen mentioned above, you just gotta get used to it or isolate the cabinet from the guitar.

Mike

[bluesky636]

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[ampgeek]

Forgive me if I missed this..but..can you currently stop the howling by muting the strings?

I concur that with your stated settings and un-muted strings you should get some singing feedback from ~10 ft away when facing the speaker. That is pretty normal from my experience with the Express and humbucker pick-ups.

However, you should not get it when you mute the strings.

Good luck,
Dave O.

[bluesky636]

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[bluesky636]

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[vibratoking]

Sigh...

Double sigh...

Stop that crap will ya?

Your ability to clearly communicate the situation along with your apparent lack of patience with everyone that responds to your thread is interesting. Do you really think that this many guys don't know what they are talking about? You have some GOOD guys trying to help you, yet you continue with your impatience and implication that everyone is somehow stupid.

Dood, clearly communicate what is happening and include the exact details of how and if you are muting and what howling and screaming really means. You could include things like, when I mute guitar the feedback occurs anyway and it is microphonic. Or when I finger a note the feedback builds and turns into a second harmonic. Or something of that nature

I think you should post a video.

[bluesky636]

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[bluesky636]

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[vibratoking]

...I have a degree in electrical engineering and have worked as a systems engineer for over 30 years on classified systems you couldn't even comprehend.

I am just trying to help you with your people skills. There are plenty of EEs here, of which I am one. I have TWO degrees and my dick is bigger than yours...blah blah blah Kinda funny you work on things I can't comprehend, yet you can't figure out what's wrong with your tube amp.

It basic human skills...if you want help, don't offend the people trying to help. Apologize and explain yourself cleary.

[Tillydog]

Thu Oct 10, 2013 11:17

Ya know what? Never mind. I'll figure this out on my one. Forget I even asked.

I think that will work for everyone.

By the way, I think you lost something:

Thu Oct 10, 2013 1:16 pm

Let me make it clear.

The component changes were done at least three weeks ago. The only components that were touched were the treble cap and the slope resistor. There is nothing wrong with the wiring routing or solder joints. The amp has been working perfectly under all conditions since it was built and the initial teething problems were solved. The amp has even been played (by the owner of a local shop that I took it to for a demo) with all controls dimed and sitting two feet away from the amp using a Gibson Les Paul Standard. Absolutely no feedback.

The amp is rock stable with all controls dimed.

I sit about 10 feet from the amp.

This all started the second day after swapping a 5751 into the PI. I have tried different tubes. The tubes are not microphonic. The feedback starts with the guitar just sitting in my lap holding it without even playing it.

Thu Oct 10, 2013 5:43 pm

I'm sorry. Did you not read where I said that the changes were made weeks ago and only involved changing two components without touching any wiring? Did I not make it clear that the amp has performed flawlessly since then? Also that Monday night after swapping PI tubes there were no issues? This all started last night. I can still dime all the controls and the amp is rock stable.

Thu Oct 10, 2013 5:48 pm

Glenn, this problem never existed before last night. I could walk up to the amp with the controls wide open, my hands off the guitar, and no feedback. Yes, it is happening with specific strings on four of my six guitars. The only change made to the amp in the last few weeks was to swap the PI with a 5751 for the 12AX7 on Monday night. On Monday night the same guitars that are now howling were dead quiet under identical conditions.

Thu Oct 10, 2013 7:06 pm

I never said that the amp does not hiss. It does and I expect it to. After I addressed all the lead dress and other issues months ago , the amp has never howled until last night. I repeat one last time: I can dime all the controls and the amp is rock stable and does not howl. That is not impossible to achieve.

Thu Oct 10, 2013 7:09 pm

Volume pot wiring issues were addressed months ago and is not a problem. Nothing has been changed in that area. In fact, all lead dress issues were addressed months ago and have not been changed.

Thu Oct 10, 2013 8:35 pm

Sockets are clean. I clean them every time I swap tubes.

I certainly intend to check the solder joints as soon as I can.

Thu Oct 10, 2013 8:41 pm

I can see the strings vibrating. When I touch them, they stop.

Believe it or not, before last night, I could walk up to my amp with the strings unmuted and not have the amp feed back. On a scale of 1 - 12, my normal amp settings are:

Presence = 6
Bass = 4
Mid = 5 to 8
Treble = 4 to 6
Volume = 5

This amp has been extremely stable. Hissy but stable. Cab is a Crate 4x12 with Celestion G12M Greenback Reissues.

Thu Oct 10, 2013 8:52 pm

geetarpicker wrote:
If you could walk up to the cab with all it's knobs dimed and your guitar up without string feedback your amp wasn't right in the first place, not even close!


I never said I could do that. The shop owner that demoed the amp had everything dimed. I could not swear that he muted the strings or turned the guitar volume down when he stopped playing, but he probably did. But with my controls set as described in the previous post, I NEVER had a feedback problem with the guitar volume full up and sitting 10 feet away. The amp has plenty of gain. In fact, this started AFTER I put a lower gain tube in the PI.

geetarpicker wrote:
However what the amp should not do is feedback on it's own with the guitar turned totally off. Perhaps the amp was actually not right prior to tweaking it (weak gain issue) and now it is actually working as designed.


I never said it does that either. In fact it absolutely does not.

Thu Oct 10, 2013 8:57 pm

Folks, I am not trying to be argumentative, but I have given an accurate and honest description of how this amp has performed in the past and how it is performing now. I bothers me that many seem to disbelieve or misinterpret my words. I have done all the obvious things to troubleshoot the amp until I can open it up tonight or tomorrow night, and when I do, I know the obvious things I need to do to troubleshoot the insides. What I am looking for are the not so obvious things that could cause this problem.

Thu Oct 10, 2013 10:20 pm

So let me get this straight.

1. I replaced the 12AX7 in the PI with a 5751 Monday night and when I played it, the amp performed as it always had in the past.

2. Suddenly, on Tuesday night the amp starts screaming like a banshee using the same guitars and sitting in the same spot I did Monday (and always have).

3. Monday night and previously the amp was not working right.

4. Tuesday night the amp is now working properly.

Does that about sum it up?

Thu Oct 10, 2013 10:52 pm

Hmmmm. I just plugged into my Weber 5F6A clone. One humbucker equipped guitar followed by one Fender SCN equipped guitar. It is behaving EXACTLY the same as my Weber Java/Express. That amp has not been opened in months and has NEVER exhibited that sort of behavior in over 2 years. The humbucker feeds back louder and faster than the SCN, just like with my Express clone.

'Splain that one please.

Thu Oct 10, 2013 10:54 pm

ampgeek wrote:
Forgive me if I missed this..but..can you currently stop the howling by muting the strings?

I concur that with your stated settings and un-muted strings you should get some singing feedback from ~10 ft away when facing the speaker. That is pretty normal from my experience with the Express and humbucker pick-ups.

However, you should not get it when you mute the strings.

Good luck,
Dave O.


Sigh.

Yes I can.

I don't consider this "some singing feedback" unless your idea of that is an increasingly loud scream/howl.

The amp has never behaved like this in the past.

Thu Oct 10, 2013 11:15 pm

And I think YOU should go back and read every single post I have made clearly explaining what is going on and tell me why I keep getting questions about things that I have already verified, like, oh, have I tried different cables, or does the feetback stop when I mute the strings. I have explained EVERYTHING I have done in great detail. I'm not stupid either. I have a degree in electrical engineering and have worked as a systems engineer for over 30 years on classified systems you couldn't even comprehend. I don't need people to tell me to do the obvious things that I have already done. I'm looking for the not so obvious things to check. Is that clear enough for you?

Thu Oct 10, 2013 11:17

Ya know what? Never mind. I'll figure this out on my one. Forget I even asked.

Oh, here it is!

[img:421:600]http://wset.images.worldnow.com/images/22173696_BG1.jpg[/img]