Ghost notes.

[57goldtop]

I've just noticed a problem with my build that I have never noticed before until I wore my earplugs this afternoon during a jam, I guess I could not hear it previously because the earplugs were cutting out most of the high end.

The amp sounds fine with a clean setting or with the volume on the guitar down but when the amp is overdriven a second note or dissonant tone can be heard especially on the G,B and E strings and is more noticeable further up the neck say around the 12 fret and beyond, They are not as loud as the notes that I am playing but they are there and it's quite annoying... It's also flabbier in the low end and I find that I have to back off the bass control considerably when the amp is pushed hard.

What would be the process to follow in order to track down the problem ?

Thanks.
57GT

[fishy]

Before touching the amp I would probably make sure its not the guitar or speaker. Pickup height can cause ghosting and speakers interact.
If the amp is on top of the speaker cab, try it away from it.

Probably swap tubes around after that. After that I think you are inside the amp looking at groundng and power supply filtering..

[guitarsnguns04]

I agree 100% sounds like a guitar/speaker issue...then maybe filtering.

[57goldtop]

Thanks for the replies.

I tried moving the amp away from the speaker box and I it didn't make a difference.

I'm wondering if there is a good method to use in order to find the bad speaker(s) ? Sometimes I hear a scratchy noise ( like when you connect the terminals of a 9v battery to a small speaker ) after I hit one of the higher notes. I tried several guitars, so it's not the guitars.

I'm going to visit my friend now and test the amp with his box to see if I can reproduce it there.

In the mean time a pair of GT-EL34M's are on the way, I hear these are great for this amp.

Regards,
57GT

[rfgordon]

If it's a high pitched ghost note, it may be cone cry. Once you hear it, it haunts you till you either learn how to modulate your finger pressure or change speakers.

As I understand it, only 12" speakers cry, except hempcones--they never do. Got no idea why that is so, but it is.

Celestion V30s and Greenbacks are notorious for cone cry.

[rfgordon]

One more thing--to the scratchy noise--make sure the speaker leads are either soldered to the tabs or are super tight. I had a loose spade connector that, I swear to you this is true, was making sparks when big chords or heavy notes were hit. If I hadn't seen the blue flashes, I wouldn't have believed it! Makes icky noises in the speaker.

[57goldtop]

Hi rfgordon.

The speakers are Peavey Sheffield 1200's, these were designed to sound like worn out Greenbacks, that's what EVH wanted. So perhaps these speakers will exhibit cone cry as well.

57GT

[57goldtop]

I've just tested the express in another box loaded with Celestions and it is still happening.

Just to describe the problem once again, it is more pronounced high on the neck especially when neck pickup is on. In my case the subharmonic tone is is pretty close to the actual note but the further up the neck I go, the tone is more unrelated.

One more thing--to the scratchy noise--make sure the speaker leads are either soldered to the tabs or are super tight. I had a loose spade connector that, I swear to you this is true, was making sparks when big chords or heavy notes were hit. If I hadn't seen the blue flashes, I wouldn't have believed it! Makes icky noises in the speaker.

I opened the back up this afternoon and tightened up the connections, the scratchiness isn't as bad now. I will solder the wires to the tabs this weekend.

I did some research and found that the term that describes the problem is called edge yowl

"Edge yowl is the term used to describe sounds that occur when the surround resonates, imparts energy back into the cone, and generates tones and notes that may or may not be harmonically related to the intended note."

I'll try the new valves first, if it doesn't help then it's time to get new speakers.

[rfgordon]

If you can find a cab with 10" speakers, try it as a diagnostic. For whatever reason, 10s don't cry/yowl.

[rooster]

Sheffields shouldn't be a problem with cone cry. You would be the first, in other words.

This sound you describe is probably a grounding issue but you didn't say whether you had used any sheilded wire on V1, pin 2 and 6. You could have a parasitic of some kind. Did you follow proper lead dress? Man, I hate tracking down these kind of noises but they can happen, been there. Off hand, I say check the grounds on pin 1 & 8 of the power tube, and all of the grounds on the large power caps.

As you say, putting a load on the amp will point these things out. Take you time and post your findings please? I for one want to hear what you found.

[57goldtop]

About the Sheffields, there are not that many people who use them, so it's more difficult to get a lot of information about those speakers. I wish I still had that 5150 head to test through my cab.

One thing to note from the pictures is that the wire I used on the speaker jacks isn't shielded. The cable I use to connect from the speaker out to the 5150 box is rather thin, the shielding is not very thick either compared to other cables I've seen.

It's late now, so I can't go cranking the amp until tommorrow. I'll see what I can find.


Cheers.

[tubedogsmith]

The sound your describing doesn't sound like cone cry, it sounds like a problem with the power supply in your amp. Maybe a bad cap or bad connection somewhere. Maybe go over your wiring there and make sure everything is hooked up right. An underfiltered supply will make the noies you describe and a stock TW supply is not underfiltered.

[fishy]

I agree with tubedog at this point in the game. You have looked at the possibilities of the speaker and guitar and I think its probably worth looking elsewhere now. You looked at microphonics which can play tricks.

There are some connections in the amp which have a fair amount of solder on them which can prove problematic. The connection needs to be made mechanically and then secured with the solder. It is hard to tell if that is the case when there is a lot of solder. It might be worth looking at some of those closely and reviewing the grounding in the amp.
You might want to check the resistance of the ground from various points in the amp and see if one stands out. Sometimes the ground lugs can have a coating on them that makes them slightly resistive.

[Tube_S_Cream]

Ghost notes at the 12th fret and up... perhaps... there is another thing that may be described like that... Lots of Strat-players know it as "stratitis". It is caused by a strong magnetic influence from the pickups, worst on the g -string around the 12th to the 16th fret.
Adjust the neck pup away from the strings and listen to the results.

Greetz

Stefan

[57goldtop]

I just redone several connections that I thought had too much solder or looked suspicious, could not find any unusual readings on the multimeter and all grounds are fine.

After listening to the amp closely today, I'm wondering whether or not these are just even order overtones produced by the valves... The second tone is always an octave apart and almost the same note. It seems to add some richness/fullness... it's difficult to describe. I don't hear that in other peoples recordings...

I've never had the need to crank an amplifier before, so I may have missed it...

Now I'm confused.