Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hesamadman on August 19, 2013, 06:51:14 pm
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Well All, here are some photos. Im going to get around to making a video but first I need to tweak the amp and get rid of this feedback. Its odd that my humbucker does not do this. Its only my single coil. But I get an incredible squeal like feedback out of my tele. Im not sure its normal because its unbearable and sometimes it does it even while I am playing. Ive tried 2 cabs and 2 cables. Still the same. I even re did the ground on my high gain input. Is there anything I can do or is it just "is what it is"
One thing I did that is probably a no no. My common wire from my PT is twisted around my heater wires. I was looking at another build when I did this. But turns out their build did not have the common on the heaters.... it was twist with the mains AC voltage. Is this an issue. Surprisingly other than that.... the amp is quiet. Not much hum at all.
Once again. Thanks everyone. I will continue to get my builds to look cleaner and cleaner!
Oh....and the random toggle switch on the back is my standby. I lost the other rocker switch. I ordered a rocker.
(http://i89.photobucket.com/albums/k205/fratbasher/photo52.jpg) (http://s89.photobucket.com/user/fratbasher/media/photo52.jpg.html)
(http://i89.photobucket.com/albums/k205/fratbasher/photo43.jpg) (http://s89.photobucket.com/user/fratbasher/media/photo43.jpg.html)
(http://i89.photobucket.com/albums/k205/fratbasher/photo33-1.jpg) (http://s89.photobucket.com/user/fratbasher/media/photo33-1.jpg.html)
(http://i89.photobucket.com/albums/k205/fratbasher/photo24.jpg) (http://s89.photobucket.com/user/fratbasher/media/photo24.jpg.html)
(http://i89.photobucket.com/albums/k205/fratbasher/photo14.jpg) (http://s89.photobucket.com/user/fratbasher/media/photo14.jpg.html)
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can you get another single coil guitar to test with?maybe a wiring issue in your guitar.
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can you get another single coil guitar to test with?maybe a wiring issue in your guitar.
Yea. I'll try that this week. :)
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That's a great suggestion, before you drive yourself nuts.
Very nice looking turret board!
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Very nice looking turret board!
Yes and the whole re-build looks much better.
Brad :icon_biggrin:
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Do you know if the pickups in your telecaster are wax potted? My high gain amps squeal like a stuck pig with unpotted pickups. Even humbuckers.
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First, being near an open chassis with your guitar at the very least you will hear hum. I have a 59 tele with the original bridge pup. The guitar will squeal if I am withing 7 to 8 foot facing an open amp. I have to shield my amps really good. Try this, take a gator clip with a wire running from it. Strip the wire long enough to wrap around your little finger. Clip the clip to one of your strings behind the bridge or if you cannot, find a place on the bridge. You will become the shield. See if this knocks down the feedback and or noise.
Old studio trick. If this the case, you will probably be fine when you complete assembly. I do not use tape for shielding. I use copper sheets and place in on the area where the open side of the amp sits. The screws hold it in place and the copper maker better overall contact with the chassis. You can get copper sheets from woodshop suppliers.
I would not wax pot the pup, but it still has quite a bit of potting now. It is simply the nature of a real single coil and to me, it needs to be that way. Not a fan of "noisless" single coils which I consider an oxymoron. It is really a staked pup.
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Do you know if the pickups in your telecaster are wax potted? My high gain amps squeal like a stuck pig with unpotted pickups. Even humbuckers.
Well.....I just had some work done to it and they installed a new (used) pickup. It is a split single coil. I don't remember if he has it wired to use only on half of the single coil or if its both. But either way its suppose to be temporary until I find a new one that I like. My old one took a poo and I just needed one in it so I could keep rockin. Ill find out more info on it.
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Should I turn the amp on and let it run all day? Perhaps play an ipod through one of my cabs. :think1: HOw about my 3x15? ha ha
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Should I turn the amp on and let it run all day? Perhaps play an ipod through one of my cabs. :think1: HOw about my 3x15? ha ha
Why?
That won't stop any squeals if their coming from a PUP. Guys do that to soften new speakers so their not so harsh sounding.
Brad :icon_biggrin:
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Well.....I just had some work done to it and they installed a new (used) pickup. It is a split single coil. I don't remember if he has it wired to use only on half of the single coil or if its both. But either way its suppose to be temporary until I find a new one that I like. My old one took a poo and I just needed one in it so I could keep rockin. Ill find out more info on it.
If it's only a temporary pickup I wouldn't get too concerned about it. Ed's suggestion to button the amp up in a cabinet as it will be when you play it is very good advice. Take any behavior about hums and noise with a grain of salt while the amp is on the bench. You might try playing with a long cord that will allow you to move away from the chassis while you play. That might tell you a little more. Trying another single coil guitar is a good idea, too. Always test the simple stuff first.
Now that I think of it my cabinet for my 2204 doesn't have a shield across the open part of the chassis (inside top of the cabinet). I'll have to investigate that one day. It's not terribly noisy as it is and with a Boss Noise Suppressor in front of it I get silence when I am not playing.
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Should I turn the amp on and let it run all day? Perhaps play an ipod through one of my cabs. :think1: HOw about my 3x15? ha ha
Why?
That won't stop any squeals if their coming from a PUP. Guys do that to soften new speakers so their not so harsh sounding.
Brad :icon_biggrin:
I was just talking about to test the amp thoroughly. Ive heard of people doing that.
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Yep. It's called a soak test. Needs to be done in a safety managed environment (fire, electrical etc). A D.I.Y first project should not be left running unattended in the average household environment. :blob8:
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... But I get an incredible squeal like feedback out of my tele. Im not sure its normal because its unbearable and sometimes it does it even while I am playing. ...
Try unsoldering your feedback wire from the impedance selector switch (or from the resistor on the board). Did that stop the squeal? 90% chance that if it does, you need to swap the wires on your output tube plates, because your negative feedback is positive feedback.
Normally, the chance would be 100%... so why is it different in your case?
I think I see 2 resistors added to an otherwise typical long-tail phase inverter layout to allow for a post-phase inverter master volume. Those resistors are fine, but they had me confused because I think you omitted a different resistor.
I don't know what your amp is, but let's pretend it is a Deluxe Reverb. From your speaker jack, you have a feedback wire running back to the board. In the Deluxe, that wire attaches to a 820Ω resistor, which then attaches to the 0.1uF cap and the tail resistor of the long-tail. But it would also connect to a 47Ω resistor running to ground.
Now if you built some other model, the 820Ω and 47Ω resistors may be different values, but they will both exist. And without the 47Ω resistor (or whatever is the correct value for your amp), you have much more feedback than you should. Maybe enough to make the amp unstable even with the correct plate wire orientation.
So add the missing resistor and ground point, and check again. At least make sure the missing part is in there before swapping plate leads. See pictures below for what is missing in you amp.