I'm all for adding these, is there a specific type you think would work best? I started looking at mouser/digikey, but was a bit overwhelmed at the choices. The shielded cable I am using is 3mm. Just clamp on a 3mm ferite on each signal cable? Also, would you place the ferrite bead on the entire shielded cable? just the signal portion of the cable? or over the inline resistor (is that possible???).
The right side of the jack in the photo (under the purple arrow to the right) is the output connection to the headphones. The left side purple arrow, is being used as a tie point. The left side is only active in the circuit when the headphone jack is NOT populated. Yes, the red wire (yellow arrow) is providing the ground for all three .01uF caps
Does my explanation of the pinout of the jack make more sense now. I have added the resistor in series and shunted all three output terminals to chassis via the .01uF caps.
I am going to try and draw this to better understand what you mean. Can you confirm I have the drawing as you described.
Thanks for the construction tips. This is only my second project, and the advice is taken to heart. I truly am learning as I go.
As for the length of the leads, I was worried about this, but that was the shortest path to the chassis ground. Not sure how to shorten these. Guess I may also need to tie the front and rear panels electrically to the top panel. (as of now, they are isolated). Then I could put another hole in the front panel next to the headphone jack?
Yea, in hindsight, I can see a lot of issue with how I constructed the chassis. Specifically, how I had it powder coated. I wanted the inside to look cool through the acrylic bottom window. At the very least, I should have assembled the chassis before it was coated.
Power input is plastic. Does threadlocker work on plastic? I've never tried. (Very good ideas!)
Last edited:
Yes. Your new drawing is it exactly! The 3rd capacitor (larger value - maybe 0,1uF) to the chassis may become less necessary once you move the 0,01 caps to after (as the incoming interference sees it) the series resistor, and shorten the capacitor's ground leads.
Probably better to not risk threadlocker on plastic -- was thinking of the grounding screws, especially if they have no other mechanical function (since if they come loose, operator may not notice).
The ferrite bead can go on either leg of the series resistor. As to type, I haven't bought any in quite a while -- the last time was probably at Radio Shack😉 They typically come in different frequency ranges; any ones that peak in the neighborhood of 75 to 125 MHz should give useful attenuation. The other deciding factors are usually mechanical -- length, hole diameter, etc.
For the power inlet, just strip the wire back the length of the bead. You can put one on each lead. Omit the series resistor, though.
I bet this thing sounds really great, too!
Probably better to not risk threadlocker on plastic -- was thinking of the grounding screws, especially if they have no other mechanical function (since if they come loose, operator may not notice).
The ferrite bead can go on either leg of the series resistor. As to type, I haven't bought any in quite a while -- the last time was probably at Radio Shack😉 They typically come in different frequency ranges; any ones that peak in the neighborhood of 75 to 125 MHz should give useful attenuation. The other deciding factors are usually mechanical -- length, hole diameter, etc.
For the power inlet, just strip the wire back the length of the bead. You can put one on each lead. Omit the series resistor, though.
I bet this thing sounds really great, too!
Boy, I see what you mean about head-spinning choices -- DigiKey at least. 9600 or some such .. and looks like most of those are surface-mount chips!
I'm still looking for a table of just the little cylinders that apparently aren't what we mean anymore when we say 'ferrite bead'. If the little 'tubes' are becoming hard to get, this may become a job for another little PCB like you're using on your volume pot.
Sure can't go to Radio Shack anymore. I'll keep looking.
I'm still looking for a table of just the little cylinders that apparently aren't what we mean anymore when we say 'ferrite bead'. If the little 'tubes' are becoming hard to get, this may become a job for another little PCB like you're using on your volume pot.
Sure can't go to Radio Shack anymore. I'll keep looking.
I wasn't really into electronics when they were around. Sad really, cause now I pay to ship something from digikey or the like every couple weeks.
I've been working my way through this material the last few days. Thanks for sharing, as I understand the reasoning behind the suggested remedies
Good tip.
It does sound great. I planned on leaving it on my desk at work. But now, since I've been using it at home on the weekends (,since I'm still tweaking), I may need build another one for my home.
O.K., sorry it took me a bit, but here are several suitable ferrite beads for FM broadcast EMI suppression. Four of them are 10 cents each (*1); all are Fair-Rite (I didn't explore the several other vendors), and stocked to 5 figures by both Mouser and DigiKey.
2643000301, 2643025601, 2643000101, 2661000101, and 2661000301
All all are 3.5mm diameter, various lengths, 2 materials -- the -61 has somewhat better performance at higher frequencies. If you had a troublesome 2 meter Ham or TV transmitter in the neighborhood it might be the better choice.
Good luck. Let us know how it turns out.
*1) But I'd go for the 'elbow' in the price break curve -- 25 or 100 quan. They're very useful for troubleshooting, especially new designs or builds. The extras should be easy to sell to other members.
2643000301, 2643025601, 2643000101, 2661000101, and 2661000301
All all are 3.5mm diameter, various lengths, 2 materials -- the -61 has somewhat better performance at higher frequencies. If you had a troublesome 2 meter Ham or TV transmitter in the neighborhood it might be the better choice.
Good luck. Let us know how it turns out.
*1) But I'd go for the 'elbow' in the price break curve -- 25 or 100 quan. They're very useful for troubleshooting, especially new designs or builds. The extras should be easy to sell to other members.
Last edited:
This was super nice of you to do. Truly, thank you. I picked a couple to the best of my ability from the little bit of information I have understood from the first half of the HAM book sgrossklass provided. But it's all still very fresh in my head. I trust these part numbers over my choice.
Will do.
Last night, I spent some time making sure all pieces of the chassis were electrically connected, so I could shorten up ground leads.This also allowed me to remove a couple runners from the input jacks and the volume pot shield, since they can now be electrically connected to the chassis.
I also moved the .01uF caps on the output to the other side of the resistors as suggested. The amp is nice and quiet at home. But that is no change. Hopefully my office doesn't close for COVID, as I need to go to the office to test this thing 🙂 . Stay safe all.
The capacitors on the output should be connected directly from the jack terminals to chassis ground
with short leads. This includes the capacitor from the jack common, which is still necessary.
I tried this, and it did not completely fix the problem (posts #35 and #38). It did lessen the RFI.
I am trying another suggestion from Rick (see post ~ #41). Are you saying I should have 5 capacitors at the output? 3 from the output eyelets to chassis ground, and 2 from before the signal side of the inline 10ohm resistors to ground??
Here is the current state of the output. I am following the drawing from post #41 as suggested by Rick in post #40.
@Rick PA Stadel,
I have a bunch of ferrite cores on the way, along with a few extra caps and resistors. (* took advantage of that price break :thumbsup: )
While practicing my social distancing, I added some ferrite beads to the output and the power input. (imgur gallery)
#43 material 60ohm
Also added #43 ferrite beads at 40ohm to the output.
and a quick test to check a 1kHz sine wave signal
Now I just need to wait for my office to open back up, so I can test the amp out in its intended home (next door to that kajillion watt radio antena)
#43 material 60ohm
Also added #43 ferrite beads at 40ohm to the output.
and a quick test to check a 1kHz sine wave signal
Now I just need to wait for my office to open back up, so I can test the amp out in its intended home (next door to that kajillion watt radio antena)
Nice work - lookin' good! Keeping my fingers crossed for that acid test at work.
Just one teensy little thing, if you still have enough Social Distancing time -- the Gnd leads of the two signal-shunt caps could be a little shorter -- maybe attach directly where the cable shields connect.
Stay healthy, too.
Regards
Just one teensy little thing, if you still have enough Social Distancing time -- the Gnd leads of the two signal-shunt caps could be a little shorter -- maybe attach directly where the cable shields connect.
Stay healthy, too.
Regards
Attachments
Last edited:
Thanks. I think I may take a ride down there later today. I need to pick up some personal items from my desk, now that the work from home directive is indefinite.
I took your suggestion. FIgured, I wasn't doing anything today anyways. ha
Leads shortened, and I changed the ground cap while I had the amp apart. Added some thread locker too.
THANK YOU! My Whammy always buzzed when I touched the volume knob. Did this and now it is DEAD quiet! 😀