| Author |
Topic: Odd overtones from my Twin |
Bobby Nelson
From:
North Carolina, USA
|
Posted 9 Dec 2018 4:50 am |
|
I have a '73 Twin Reverb with K120s in it, which I play a new MSA through. It doesn't seem to matter which pup I use, but I mainly use an Alumitone. the thing sounds really great - until I turn it up to stage volume (starting about 3). Then, I get these really strange, non-musical (almost percussive) overtones as I open the Hilton from about 75% to full volume. The overtones resemble something you might hear out of an Octavia or an envelope filter or something. I keep the master out of the chain by keeping it wide open. I tend to like a trebly tone so, it's heavy on the treble (but not wide open).
Anybody had this experience or have any ideas how to fix this?
I think the Twin circuit is similar to a powerful Super Reverb, and they tend to start sounding bad past about 5 & 1/2, but I'd like to be able to use that headroom if I need it. |
|
|
|
Mark Draycott
From:
Princeton, Ontario, Canada
|
Posted 9 Dec 2018 6:05 am Twin Reverb
|
|
I have repaired a few amps having this identical issue. Replacing the power supply filter capacitors solved it. If you know an amp tech, have him measure AC voltage on the caps and see how well they are working.
_________________
1976 Sho-Bud Pro II, 1976 Sho-Bud LDG, BF Fender Deluxe, Evans FET 500 LV, BF Princeton Reverb, '68 Vibrolux Reverb |
|
|
|
Bobby Nelson
From:
North Carolina, USA
|
Posted 9 Dec 2018 6:16 am
|
|
| Thanks Mark. that's the thing, he replaced the filter caps last year when I bought the amp and speakers. it also has been making some static sounding noise, like a dirty pot sound, but none of the pots seem to have a scratchy sound when I turn them. I was just wondering if it was maybe a pup adjustment or something. I'm going to be taking it back to my man to fix the scratchy sound soon, so I'll have him look at it. thanks again. |
|
|
|
Edward Rhea
From:
Medford Oklahoma, USA
|
Posted 9 Dec 2018 10:42 am
|
|
Bobby, I experienced something similar(I think?) on my Deluxe Reverb, a while back, and instead of loading up the amp and rushing it to my amp tech, I felt around the tubes and discovered that the rectifier and a couple preamp tubes were “wiggling around†back there? After re-seating them, the crackling and overtones disappeared. I often grab this amp for jams. All I can figure is that riding in a vehicle, to and from, caused the tubes to work out of their sockets ever so slightly, in turn they weren’t making good contact. I hope it’s that easy for ya!?
_________________
“TONESNOB†|
|
|
|
Bill Sinclair
From:
Waynesboro, PA, USA
|
Posted 9 Dec 2018 12:10 pm
|
|
Tube to socket connection, as Edward said, is the next place I'd look after the pots. I've also seen leaky coupling capacitors cause a crackling sound but I wouldn't go replacing any of those unless your tech narrows it down to that.
Your description of the overtones resembling an octavia makes me think of speaker "cone cry". In my experience this usually occurs within a one or two note range where the speaker cone produces a perfect fifth above the note being played. You might try a different speaker just to see what happens. Let us know what you find. |
|
|
|
Paul Sutherland
From:
Placerville, California
|
Posted 9 Dec 2018 1:14 pm
|
|
How old are your tubes? Have the power amp tubes been biased recently? Are the power amp tubes a matched set?
A failing preamp tube could cause some of what you've described. Try replacing one preamp tube at a time with a known good (as in new) tube. If you hear no difference, then put the old tube back in and move on to the next. You'll need one good (new) 12ax7 (or 7025) and one good (new) 12at7 to do such testing.
_________________
It don't mean a thing if it ain't got that swing. |
|
|
|
Bobby Nelson
From:
North Carolina, USA
|
Posted 10 Dec 2018 12:33 pm
|
|
Thanks fellas. I will try the tube seating and see. I don't believe a Twin has a rectifier tube. The power tubes are a fairly new matched set that came with the amp, and were checked to be fine and biased with maybe 40 hrs of relatively quiet use since - the preamp tubes, the same.
The "cone cry" might be a good idea except tat it is not just a note or two - it does it on all, especially high notes.
After I try to fiddle with the tube connections, I'm thinking that maybe the coupling capacitor (or perhaps a tube socket) may be the culprit. Looks like a trip to my amp guy is in the future.
Thanks again guys - I'll let you know about tube connections. |
|
|
|
Bobby Nelson
From:
North Carolina, USA
|
Posted 11 Dec 2018 3:02 pm
|
|
| Thanks again fellas - pushing the tubes in seems to have done the trick for the most part. I cranked it to 3 1/2 and very very little of the overtones were apparent. 3 1/2 is very very loud here in my room so, a little bit is expected at that volume I suppose - it would be inaudible on a stage with a band. |
|
|
|
Tony Prior
From:
Charlotte NC
|
Posted 12 Dec 2018 11:04 am
|
|
Twin Reverb should not have any overtones or scratchy sounds, no amp should actually ! TR's and other Fender amps, E-Caps, screen and grid resistors, re-set /clean the tube sockets etc, not just push the tubes in. A tech should do all of this with E Cap replacements. It's typical and normal maintenance. The heat on the chassis( from the 4x power tubes) takes out the resistors across the power tube sockets.
The description of overtones is typically related to PS and caps, it may even be a bad solder joint . Coupling caps are in the preamp and tone stack , they pass signal from one circuit to another, if they are bad ( extremely rare) they may cut off a frequency or not pass any signal. . Static noise can easily be a bad solder joint or a bad tube socket or a loose socket. Perhaps a bad POT as well. If a pot sits in the exact location for years, that one location can become worn and create a scratchy situation.
TR's should be dead quite and clean pretty much all the way up the dial. At 3- 1/2 it's not even on yet ! 
_________________
Emmons L-II , Fender Telecasters, B-Benders
Pro Tools 12 on WIN 7 !
jobless- but not homeless- now retired 9 years
CURRENT MUSIC TRACKS AT > https://tprior2241.wixsite.com/website |
|
|
|
Bobby Nelson
From:
North Carolina, USA
|
Posted 14 Dec 2018 5:27 am
|
|
[/quote] At 3- 1/2 it's not even on yet !
| Quote: |
That was exactly my thoughts on it Tony. When I brought it home, it was clean as could be, but developed the scratchiness over the last year. Combos have always had heat problem, and this being my first 4 pwr tube one, I suppose it more problematic - maybe the should have turned them over like a Marshall in a head unit. I'll get it back to the shop here when I can, and have Al go through it again. Thanks Tony |
|
|
|
|
Bobby Nelson
From:
North Carolina, USA
|
Posted 14 Dec 2018 5:29 am
|
|
| Well Tony, I think you get the jist of the last post even with the screwy quotations - My hand is making it difficult to get anything right with the keyboard haha! |
|
|
|
Josh Yenne
From:
Sonoma California
|
Posted 14 Dec 2018 10:42 pm
|
|
| Wow. You get your volume pedal all the way to the top? Really? Not related to your problems just asking. |
|
|
|
Bobby Nelson
From:
North Carolina, USA
|
Posted 17 Dec 2018 8:51 am
|
|
| That's how I'm approaching the vol pedal at this point Josh: I find my top volume at 75-80%, and use the rest of it['s travel for sustain. |
|
|
|
Tim Whitlock
From:
Colorado, USA
|
Posted 17 Dec 2018 9:01 am
|
|
| FWIW: My Twin Reverb was getting progressively noisier. While checking the tubes I thought it wouldn't hurt to spray the pins with some electrical cleaner. When I put the tubes back in the noise was gone. Now I pull the tubes once or twice a year and clean the pins. |
|
|
|
Tim Whitlock
From:
Colorado, USA
|
Posted 17 Dec 2018 9:02 am
|
|
| FWIW: My Twin Reverb was getting progressively noisier. While checking the tubes I thought it wouldn't hurt to spray the pins with some electrical cleaner. When I put the tubes back in the noise was gone. Now I pull the tubes once or twice a year and clean the pins. |
|
|
|
Bobby Nelson
From:
North Carolina, USA
|
Posted 18 Dec 2018 2:29 am
|
|
| Thanks Tim. |
|
|
|
John Goux
From:
California, USA
|
Posted 22 Dec 2018 12:08 am
|
|
I’ve got this on a vintage Pro Reverb.
The amp sounds magical, but in certain chords, you get this low difference tone.
A second similar amp does not do this.
I don’t know what causes it, but I’m afraid to take it to a tech who may fix the problem, but change the tone of the amp in the process.
John |
|
|
|
