Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: JustMike on June 23, 2024, 04:22:10 pm
-
I was having a problem with a 5e3 build where the wire from the vol pot to pin 2 of V2 was microphonic when I chopsticked it. I tried the usuals, replaced the tube, retensioned and cleaned the socket pin thingies (receptacles?) to no avail.
So I searched "what causes microphonic wiring tube amp" and found a thread over on Amp Garage titled "Microphonic Wire?" and they say that Teflon wire can be microphonic. Sure enough I'm using teflon wire. Changed this one lead out to PVC and Voila! No more microphony. News to me anyway so I thought I'd share.
-
I wanna see the science on that one (20th century, there is no science so far this century:)
unsoldering n re-soldering, plus lay of wire before n after, now that I can accept changing symptoms
-
PVC and PTFE are pretty close on the triboelectric series, so I'd imagine the problem was something else.
-
close on the triboelectric series
Yes but you still have to actually rub them together to make triboelectricity tho LoL
-
Is the amp working/ playing normal ?
Many parts could be microphonic when you touch them and is is not an issue if amp play normal
A wire not running close to the chassis may act like antenna a do some noise
Did you run the new wire exactly like the teflon one ?
If not :
You do a better lead dress , It is not the wire, it is your work.
-
I ran the new wire exactly the same as the old one.
Only one way to find out. I'll resolder the old teflon wire back in and report.
-
I believe that was my thread at TAG. I never experienced this issue before nor after using that wire. I'm not saying it was the wire for sure, but I'm not chancing it. I've never had a piece of wire that, if I rubbed it with a chopstick, I would hear static from the speaker. Every single grid wire in the preamp did it (three stages). Of course, YMMV and all that. Not saying my words are the gospel on it. Maybe that particular circuit was sensitive (I believe it actually came from here - "Princeton Derivative" AA964 - tremolo + gain stage)? Honestly, my curiosity didn't get the better of me, so I put some weather stripping between the wire and the chassis, which seemed to stop the issue (the chassis was in a combo, and my suspicion is that the wire was rubbing the chassis with the vibration). That was pert near nine years ago, and the owner never sent it back. Either I fixed the problem, or he decided not to deal with it anymore. :dontknow:
-
Well, theres a clue. The wire is pretty long and it runs under the board lying on the chassis. And when loud or low notes are played, there is static. But that doesn't explain why the wire is microphonic.
-
Well, everyone has their own opinion on stuff like this, mostly driven by anecdotes. And that's fine. And that's part of the reason why this forum, and TAG, are both informative and fun.
Every airplane I've ever looked at has a lot PTFE (or a variant of) wiring. All of the MIL-Spec wiring I purchase has Teflon (or similar) insulation. I like it because of its heat resistance; have not had trouble with excess microphonic issues. I figure, if it's good enough for Lockheed Martin, or Northrop, or Sikorsky, it's good enough for me.
Personally, I don't think the Teflon insulation has anything to do with the microphonics. That particular wire may well have been microphonic. Why? Bad solder joint or a broken strand in the wire itself, or something peculiar to that length of wire, or something else, who knows . . .
-
Personally, I don't think the Teflon insulation has anything to do with the microphonics. That particular wire may well have been microphonic. Why? Bad solder joint or a broken strand in the wire itself, or something peculiar to that length of wire, or something else, who knows . . .
I'm going to stress: I'm not a *magic components* guy. As long as it meets requirements and is easy enough to work with, wire is wire to me. In my situation it was all three preamp grid wires that, if I slid a chopstick along the wire, I could hear a static-like crackle in the speaker. Again, it doesn't make sense to me. I'm as much a skeptic as anyone. Nine-years-later me wishes nine-years-ago me would have investigated further. It was most likely a coincidence that it showed up with my first use of teflon wire.
-
close on the triboelectric series
Yes but you still have to actually rub them together to make triboelectricity tho LoL
What I mean by this is both materials are similarly situated on the series with respect to the conductor, assumed to be copper. Tapping induces microscopic rubbing between insulator and conductor, as does vibration from sound waves. This creates the opportunity for the triboelectric effect--especially at the grids early in the preamp.
If either PTFE or PVC were drastically more negative with respect to copper, then I'd expect that material to make the wire more likely to be noise prone than the other when tapped. Since they are not I'm expecting something else to be the cause of the microphony/noise.
-
I get some triboelectric effect and resultant shocks in inside my house but have never encountered it inside an amplifier.
-
we get electric from nuke plants, our Police force is Tribo, Potawatomi I believe
-
I get it hopping out of my car when my lard ass jeans rub against the cheap upholstery and then I touch the door
-
I was having a problem with a 5e3 build where the wire from the vol pot to pin 2 of V2 was microphonic when I chopsticked it. ... found a thread over on Amp Garage titled "Microphonic Wire?" and they say that Teflon wire can be microphonic. Sure enough I'm using teflon wire. Changed this one lead out to PVC and Voila! No more microphony.
The Teflon wire itself is not microphonic, but many of them tend to be stiff.
Stiff wires transmit vibration/deflection/movement better than floppy wires.
Stiff wire transmits the movement to another component, that actually is microphonic when moved. Often, this is a capacitor or possibly a resistor.
Someone looking for "the microphonic component" would look to see where the wire connects, and tap the components found; typically these are found to be the true noise-source.
I offer this because I have multiple amps wired up with Teflon wire & no microphonic issues.
-
In my experiences running wires under the board can be an issue with noise, especially the secondary wires from the OT. I have chop sticked wires in a tight chassis, that produced noise and moving took it away. Lead dress is a very important task in building an amp.
-
This is a 5e3 build and it's the wire between the Vol pot output and V2 pin 2. So it runs either over or under the board. I had it under the board. I now believe the difference between the teflon and PVC wire is the insulation thickness because when I tap on the PVC wire, there's still some microphony but considerably less. I put the original orange teflon wire back in just to test the connections and it sounds like it did originally. I even tried a purple teflon wire but it sounded the same. I put the (brown) PVC wire back in across the top of the board and it's still microphonic. I guess I could try a shielded wire and see if that helps. But that seems like a band aid fix of the symptom and not the problem.
-
This is a 5e3 build and it's the wire between the Vol pot output and V2 pin 2.
Just use a shielded wire there, ground the shield at one place, near the vol pot, and run the wire wherever you want. Not a band-aid fix.
-
... it's the wire between the Vol pot output and V2 pin 2. ... when I tap on the PVC wire, there's still some microphony but considerably less. I put the original orange teflon wire back in just to test the connections and it sounds like it did originally. ...
The most likely culprit here is V2 itself: the tapped wire is shaking V2's grid pin. PVC wire is floppier, and doesn't transmit the "shake" to the pin as well as Teflon.
Tubes tend to be the most-microphonic item, then capacitors.
-
I'll say that this little adventure has shown me that teflon wire will make more noise in this scenario because it's typically thinner than PVC, it's harder than PVC, so it will resonate more than PVC. But the quietest wire of all is grounded coax. Problem solved.
-
Bad connections can be microphonic. Just saying.