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Topic: Standel S80 All tube with RFI problems |
Abe Levy
From:
California, USA
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Posted 8 Mar 2016 9:11 am |
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I recently acquired a Standel piggy back S 80 all tube amp - it sounds killer- but picks up radio signals to a ridiculous degree. Is there a simple solution to this problem? Thanks!
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Mostly Pre-1970 guitars.
Last edited by Abe Levy on 8 Mar 2016 1:16 pm; edited 1 time in total |
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Jonathan Lam
From:
Brooklyn, NY
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Abe Levy
From:
California, USA
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Posted 8 Mar 2016 10:57 am
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Haha!
_________________
Mostly Pre-1970 guitars. |
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Lane Gray
From:
Topeka, KS
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Posted 8 Mar 2016 11:04 am
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RFI (Radio Frequency Interference) is well known and almost common. This forum is full of amateur radio nerds and a professional radio broadcast tech. A subject line mentioning radradio interference should bring them right along.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects |
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Mike Neer
From:
NJ
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Posted 8 Mar 2016 11:26 am
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I've owned two of these amps. One was one of the best amps I've ever owned and the other was a dog.
Find out who is familiar with Standels in your area. However, I don't think the problem you are having is uncommon in vintage amps. Definitely take it to a top notch tech who has a history with vintage amps.
_________________
Links to streaming music, websites, YouTube: Links |
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Chris Bauer
From:
Nashville, TN USA
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Posted 8 Mar 2016 11:40 am
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| If you're in southern California, Tim Maag is your guy. If you're in northern Califonia, I'd think it would be tough to beat Skip Simmons. |
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Abe Levy
From:
California, USA
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Posted 8 Mar 2016 1:15 pm
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I'm actually in Toronto - spending a couple years here... Any body got any recommendations for Toronto Standel techs?
_________________
Mostly Pre-1970 guitars. |
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Chris Bauer
From:
Nashville, TN USA
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Posted 8 Mar 2016 2:47 pm
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Oh, northeast California!  Can't help you there, I'm afraid... |
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Brett Lanier
From:
Hermitage, TN
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Posted 8 Mar 2016 3:24 pm
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| Abe Levy wrote: |
| I'm actually in Toronto - spending a couple years here... Any body got any recommendations for Toronto Standel techs? |
Travis and Dallas Good (The Sadies) live in Toronto. Don't think they work on amps themselves but they tour with brown and blackface fenders and have been in the area forever so they'd probably know the best amp techs around.
Are the power tubes in your amp the kind with the plugs on top? I have an Imperial like that. |
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Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
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Posted 8 Mar 2016 4:10 pm
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Abe,
Some questions come to mind: Does your amp pick up the radio stations with no cord plugged into the input jack? Do the signals get louder when you increase the volume control? Are the signals related to the setting of the reverb control? It's almost certainly AM radio causing the interference and Toronto has some powerful stations. Once you determine where the signal is entering the amp, it should be an easy job to add bypass caps to eliminate the problem without affecting the amp's sound.
Craig
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"Make America Great Again". . . The Only Country With Dream After Its Name. |
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Georg Sørtun
From:
Mandal, Agder, Norway
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Posted 8 Mar 2016 4:23 pm
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| Follow up on Craig's response ... I often use ferrite beads to filter out RF and other high frequency noise in audio circuits. |
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Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
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Posted 8 Mar 2016 6:59 pm
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Georg,
Ferrite beads might do the trick. I just checked and Toronto has seven 50,000 watt stations. Abe must be fairly close somebody's transmitter in order to have his Standel detect the audio. I've only had that problem happen one time in Richmond, VA, but I was only a block from the tower. It will be interesting to follow Abe on this journey and see what it takes to filter out the interference. The cause may be something as simple as the high resistance of a cold solder joint, or two dis-similar metals acting like the detector in an old-fashioned crystal set. (if anybody here is old enough to remember them.)
Craig
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"Make America Great Again". . . The Only Country With Dream After Its Name. |
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Bruce Derr
From:
Lee, New Hampshire, USA
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Posted 8 Mar 2016 9:06 pm
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A tip about ferrite placement: A ferrite bead's peak impedance is fairly low compared to the high input impedance in a typical tube amp. For this reason it won't do much good at the input (grid) of a tube stage. Better to put it in the cathode circuit of the 1st preamp stage, which is a lower impedance circuit where the ferrite's impedance will have more of an effect.
A ferrite bead works best when the inside diameter is a close fit to the wire passing through it. The impedance can be doubled by passing the wire through twice or even three times, if it will fit. More loops than that, the inter-turn capacitance starts to be a problem.
Another thing you might try is to clean the preamp tube sockets. Oxidation can act like a diode junction and, along with stray capacitance, form a simple RF detector, as Craig mentioned. (Yes, Craig, I'm just old enough to remember crystal sets and cat whiskers.) |
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Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
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Posted 9 Mar 2016 5:19 am
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Bruce,
Thank you, I feel much better now. I had a cat's whisker until somebody "begged" it away from me a few years ago. Need to get one from Antique Electronics Supply so my office will be complete. I have some galena crystals, just no place to put them. Talk about hi fidelity, those were the days my friend.
Never used ferrite beads in a tube circuit, interesting to place them in the cathode lead. Thanks for the tip.
Craig
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"Make America Great Again". . . The Only Country With Dream After Its Name. |
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Mike Neer
From:
NJ
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Posted 9 Mar 2016 6:04 am
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| Abe Levy wrote: |
| I'm actually in Toronto - spending a couple years here... Any body got any recommendations for Toronto Standel techs? |
Call Chris Bennett at The Twelfth Fret (Chris owns my old S80 head). He should be able to suggest someone for you, he is well connected.
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Links to streaming music, websites, YouTube: Links |
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Abe Levy
From:
California, USA
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Posted 10 Mar 2016 7:48 am
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Thanks everybody! mike - I'll call him today. Thanks again!
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Mostly Pre-1970 guitars. |
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Chris Lucker
From:
Los Angeles, California USA
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Posted 10 Mar 2016 5:55 pm
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I have the same AM station problem with one of my 25L15s.
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Chris Lucker
Red Bellies, Bigsbys and a lot of other guitars. |
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