Express Clone With Howling Feedback - HELP!!!!

[mauiboy81]

Love those little guys. For some reason they were all I could ever catch when I went fishing.... Probably has something to do with the fact that I'm a lousy fisherman. Other guys would be pulling in ulua and I'd be throwing back humuhumunukunukuapua'a all day long.

[Tillydog]

Still waiting for updates here....

http://forums.fender.com/viewtopic.php? ... &start=257

[Blackburn]

HIS NAME IS BILL....

Why is he so calm and composed on the Fender forum? Maybe he feels like the smart guy in the room?

That can't be it. He thought he was the smart guy over here, too. Medication? I think I'll join the Fender forum...

[M Fowler]

I liked page 16 his feed back report from local Virginia guitar store owner:

Had an interesting time this afternoon with the Wrecking Ball.

I gathered the amp up and took it over to Action Music, a small independent guitar dealer in Falls Church, VA. They specialize in vintage equipment (electric and acoustic guitars and amps) a select new equipment.

http://www.actionguitar.com/

I introduced myself to the owner and explained to him what I have been doing and asked if someone in the shop would be willing to test drive the amp. He said that he would be glad to do it after another customer who was auditioning a couple of amps was finished.

After about 15 minutes, he plugged my amp into an Orange 4x12 cab loaded with Celestion G12Hs and then plugged a late vintage Gibson Les Paul Standard (I was too nervous to ask what the guitar exactly was ). I told him a little about the amp and what the design was. He then set all the controls to 12 noon except for the volume control which he set to max! He then let loose.

I was thrilled that the amp did not collapse into screaming/squealing oscillation (I had briefly tested it with all controls dimed and was confident it would hold together) and was amazed at how loud it was. He then twisted all the controls from high to low as he played (volume still maxed out) to get a feel for how the amp responded. Then he turned it down to about 5 and did the same thing. He played the amp like this for about 20 minutes as several customers and employees watched and listened (and didn't run for cover). When he finished, I noticed smiles on everyone's faces (which I took as a good sign) as he apologized for blowing everyone's head off in the small shop.

His verdict?

"It's a really good sounding amp".

His comments/criticisms?

1. The tone controls need more range to them. They are good at levels below about 6, but when the volume is dimed, they lose their effectiveness.

2. The bright switch was a little to heavy handed.

2. The amp has too much gain in the front end.

3. The amp is too loud for today's market.

We then talked for another 30 minutes about different approaches to alleviate his concerns.

I'm going to reexamine the tone stack design. I evaluated several different designs while building and testing the amp ranging from a Fender Blackface type stack to a 59 Bassman stack (what is in the amp now), and a Trainwreck Express type stack (similar to the Blackface, but not quite). I'll take a look at these again to see how they respond at different volume settings.

The current bright switch uses a DPDT switch with center = off, up = a 100 pF cap, and down = a 250 pF cap. I personally don't like the 250 pF cap as although it gives a nice midrange boost, it brings the noise floor up too much. I had tried a 50-off-100 configuration earlier but I was still having noise problems then and abandoned the bright switch entirely. After I solved the noise issues I settled on the 100-off-250 set up. I think I'll look at the earlier version again.

Reducing the gain can be done a number of ways. The Action Music owner suggested just adding a low gain input. Early on, I built a switchable bypass cap for V1. I didn't like it as it caused a hum when the cap was switched out. I could also just try a lower gain tube in V1 or V2. Several good choices.

As for the volume, I don't like master volumes. A PPIMV would be a good choice for this amp, but it reduces the effectiveness of the negative feedback and presence control. I may take a look at the Hall Variable Voltage Regulator (VVR) which is popular with this type amp.

http://www.hallamplification.com/main.html?src=%2F#2,2

Stay tuned for more high gain fun.

Note: I was very nervous going to Action Music with the amp today, but am really glad I did. The owner was very nice to take the time to try out the amp. He had some really good suggestions and was very supportive of what I was doing. Even though we didn't open up the amp, it thought the build quality was really good and that the amp was very professional looking. I'll definitely go back after I am able to come up with some solutions to his suggestions.

_________________
Bill

[geetarpicker]

Amazing! The guy still doesn't realize that when his amp is in the mood to have enough gain to get natural feedback off the guitar strings (with amp on 6 @ 10' away) that it is PERFECTLY NORMAL for these amps!

Now he will proceed to reduce it's gain with mods and such to truly fix it.

IMHO many amp builders start off building amps like tweed Deluxes, Champs, and maybe even tweed Bassmans. Then they decide to build a boutique clone and build an Express, and then don't know what the heck to do with it's potential. An Express isn't much of a stretch if you grew up on say old Marshall 50s or 100s DIMED, but if your idea of gain is a cranked Fender Deluxe I guess you would think your new Express build was wonky if it sang like a dimed Marshall stack. Hmmm...

[gktamps]

You can't help some people, though you tried.

[JoeCon]

Glen

You got that right!
The reason to build an Express is to get the dimed Marshall experience. That natural feedback is what I want!! I remember playing with TWO 100 watters and two angled 4x12 cabs ("we were children once playing with toys") and finding that spot where it all came together. Just an amazing experience to feel/hear that. But if you don't have that point of reference when your guitar starts wailing you think something must be wrong!! LOL...

[lpd]

Don't want feedback don't build a Wreck. That feedback is what I built the amp for.

[Firestorm]

I'd like to see some more discussion on power scaling these beasts. A lot of guys scale the whole thing, which is different, but scaling just the PA makes sense, except it requires some kind of post-PI master, which screws up the NFB.

[vibratoking]

Too bad the OP reached nirvana and didn't even know it. That's an angry tragedy.

As Miles once told, put a blanket or two or three over it. I think he even recommended the brand and how to sew it...to bad I can't sew. That's power scaling. I VVR'd the whole thing...I actually use it occasionally, but I sure do like it the way KF intended. Loud...I like it.

[M Fowler]

Now he is reporting he is watching us watch him and throwing out insults to us on page 18, what a fool.

[Firestorm]

Now he is reporting he is watching us watch him and throwing out insults to us on page 18, what a fool.

I don't see that. Where? (Maybe I just couldn't read through it all again). Seems like he's being civil over there.

[Reeltarded]

Too bad the OP reached nirvana and didn't even know it. That's an angry tragedy.

As Miles once told, put a blanket or two or three over it. I think he even recommended the brand and how to sew it...to bad I can't sew. That's power scaling. I VVR'd the whole thing...I actually use it occasionally, but I sure do like it the way KF intended. Loud...I like it.

Surplus army blankets. You rivet them together in pairs. 3 pads for each 100w cab, 2 for 50s. I finish it off by throwing a saddle blanket over it for looks. Dinner music that people can feel.

And as far as dirk mceffstick over there goes watching us watching him watching us watching him.. whatever, dolt. You are so crude to be human. Your intelligence is crustal based or something. Maybe a slipped gene or a misplaced neuron.

I like marbles.

[JoeCon]

Miles

I tried that with my Rocket head but it was still loud and now I can't reach the knobs!!??

Oh speaker cab...Doh!!

[HeeBGB]

Now he is reporting he is watching us watch him and throwing out insults to us on page 18, what a fool.

I am reasonably sure he has two accounts here. His main was de-activated at his request but I have another account that has an IP address in the very same neighborhood as his main account.