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Post subject: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Tue Apr 26, 2011 11:27 am
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I replaced my Bassman with a Bandmaster, hooked up with all the same pedals, while the sound is great clean, all of my Wah pedals are causing a super high pitch feedback when engaged and fully down. This happens on any of the channels, bright or not. I play pretty loud and pretty close to the cab which does not help but at about the same volume this would not happened with the Bassman. Anyone with similar experience?


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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Tue Apr 26, 2011 12:49 pm
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What tubes are you currently using in the V1, V2, and V4 positions?

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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Tue Apr 26, 2011 12:58 pm
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Good questions, I'll post this back when I get home later :)


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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Tue Apr 26, 2011 2:10 pm
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Ok, here it goes:

The tube chart should be left from right:

6L6 - 6L6 - 12AT7 - 12AX7 - 7025 - 7025

In my amp right now:

6L6GC Svetlana - 6L6GC Svetlana - JJ ECC81 - JJ ECC83S - JJ ECC83S - JJ ECC83S

So I guess, ECC81 is good substitute for 12AT7 and ECC83S is good for 12AX7 but not sure about substituting 7025 with ECC83S.

What you think?


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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Tue Apr 26, 2011 2:24 pm
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The 7025 is simply a 12AX7 developed for military/industrial use, with a better noise floor for improved S/N ratio.

Your tube array looks fine (great, actually). It is possible that those ECC83S's are just too hot for that particular amp, especially when driven into overdrive and saturation with outboard devices. You might try subbing a 12AT7 or ECC81 into the V1 and V2 positions to tame the front end a bit.

Arjay

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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Tue Apr 26, 2011 3:08 pm
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I may have some of these somewhere in the house already. I can try some swaps. Wonder if I'd have to adjust bias though?

By the way, this happens when volume is at 3-4 on amp and 10 on Strat. Tried a fuzz pedal on it too and I have same result with feedback, although I can tame that with the knobs on the pedal.


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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Tue Apr 26, 2011 3:16 pm
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A bias adjustment is only required when changing power tubes -- in the case of your Bandmaster, those would be V5 and V6.

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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Wed Apr 27, 2011 6:02 am
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Oh, I had the tube order backward, it all makes sense now. :)


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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Fri May 06, 2011 8:39 am
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on my 65 bandmaster, I really liked a JAN Philips 12AX7 for V2 and a Mullard CV4024 for the Phase inverter - the Mullard for the PI made a huge difference over the JJ's.

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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Sun May 08, 2011 12:13 pm
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Have you done any experimenting to be sure it isn't your guitar that is squealing? High-pitched microphonic pickup feedback is common with lots of gain and a wah in full treble position, and standing close to your amp is the best way to make that happen. Maybe the Bassman didn't have as much juice as the Bandmaster, and so it's more sensitive to this "proximity feedback". To see if the amp itself is generating the feedback, turn the guitar to zero and the amp to 10, and tap on the back of the chassis with something hard, like a screwdriver handle. If you get the feedback, or the tapping comes out of the speakers really loud, this could be an indication of a microphonic valve, which is a simple fix, and easy to track down. If it is a microphonic guitar pickup, that, too, is easy to fix by potting, but this will change the guitar tone a bit.

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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Sun May 08, 2011 3:51 pm
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Tried quite a few guitars on it, all similar result with hissy feedback, more so with a Tele. I think it's just the nature of the beast, I play loud in a small basement. I am slowly learning to work around it. Bassman was not as fussy with pedals, the Bandmaster whines about pedals, same with fuzz, very touchy now. Alos, I noticed my phaser now sucks up some of the volume when engaged. TS9s are working really well though.

I'll try to hit the chassis in the $@! as suggested though, could be a bad tube indeed.


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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Mon May 09, 2011 7:37 am
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Utter nonsense - the AB763 Bandmaster takes pedals very well - the whine is either from a bad tube or something else. This amp does clean exceptionally well and if there's an issue that swapping different tubes doesn't fix then take it to a competent amp tech.

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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Mon May 09, 2011 10:14 am
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nedorama wrote:
Utter nonsense - the AB763 Bandmaster takes pedals very well - the whine is either from a bad tube or something else. This amp does clean exceptionally well and if there's an issue that swapping different tubes doesn't fix then take it to a competent amp tech.


+1!

There's something amiss within the amp that requires attention.

Arjay

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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Mon May 09, 2011 10:46 am
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Yesterday I played with the guitar volume lower and amp between 4 and 5 and wah worked out fine. Maybe I need to stay further away from the cab, I'm literally about 7-8 feet from it, not facing the cab obviously also helps :)


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Post subject: Re: 64 Bandmaster - High Feedback with Wah Pedals
Posted: Mon May 09, 2011 1:22 pm
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A basement is noted to be a "bright" room due to concrete floors, walls and (occasionally) the ceiling. Could be that the resonant properties there are at least partly responsible for your situation. Carpeting and some wall tapestries might be of some help.

Arjay

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