Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => The Newcomer's Forum => Topic started by: saturated on October 13, 2024, 05:44:33 AM

Title: I thought I would filter some frequency (but I don't think I did)
Post by: saturated on October 13, 2024, 05:44:33 AM
So I encountered a device that looked like a transformer or a choke.  I didn't see enough wires for a transformer so I immediately concluded that it was a choke.  For some reason I decided maybe I can start out simple and measure resistance (hey why not  :duh )
IMG_20241012_210510690.jpg

My ultimate plan was to run a sin wave thru it and start filtering like I read about in those books yay  8|
But then I ran into a problem
IMG_20241012_210523143_HDR~2.jpg

Dude...is this the same as a choke ?!?!!?!?
 :grr
(Btw looks like we have some cool upgraded emoticons  <3) )

Oh well on with the experiment....dialed up some sin wave and connected it paying attention to Vp-p and RMS etc

IMG_20241012_211253153_HDR.jpg

IMG_20241012_211421225_HDR.jpg

I then altered the frequency  :loco checking the scope for any changes....I did see a
reduction in amplitude but my generator only went up to 3 Mhz
IMG_20241012_211649158_HDR.jpg
At higher frequency I found this adjustment helpful  :lmao:
IMG_20241012_211612462.jpg

I also connected my multimeter across the DUT to monitor voltage drop wrt frequency and it did increase directly proportional to it but maybe my meter couldn't handle it when it got too high idk because it just got bigger then dropped to zero.

So at the end of the day perhaps I was seeing an attenuated (?) signal that was left over after the voltage drop (?)

At a certain frequency I did some maths and determined RMS from the scope and added it to my multimeter RMS but they didn't quite add up to what I had started with.

 :grr

The "results" were not what I expected I thought I would be able to vary frequency and there would be a range or ranges or a cutoff where no signal was getting through but I didnt see that at all.

Oh yeah btw if it helps....I did test it with this as well
IMG_20241012_210655489.jpg

IMG_20241012_210703834.jpg

 8|
Title: Re: I thought I would filter some frequency (but I don't think I did)
Post by: saturated on October 13, 2024, 07:05:08 AM
Btw I do know about the pi filters and stuff that use a capacitor as well and a certain frequency gets through because at the sweet spot frequency the reactances are equal and cancel out because of resonance, theta and Eli the Ice Man  :dbtu: because I worked a million of those problems  :'(

But I still thought a choke by itself would become restrictive at some point
Title: Re: I thought I would filter some frequency (but I don't think I did)
Post by: g1 on October 13, 2024, 02:13:10 PM
How about a schematic of the way you hooked it up?   :)
Title: Re: I thought I would filter some frequency (but I don't think I did)
Post by: saturated on October 13, 2024, 02:59:43 PM
Yes sir thanks

Before I post the picture I am aware that I have struggled mightily trying to remember that a scope probe and ground clip are different than two leads on a multimeter

But here you go

IMG_20241013_135130191.jpg

 :P
Title: Re: I thought I would filter some frequency (but I don't think I did)
Post by: saturated on October 13, 2024, 10:32:29 PM
After further review....
I think the signal generator needs to be connected like this

:loco

IMG_20241013_213042906.jpg

Will report back  :grr
Title: Re: I thought I would filter some frequency (but I don't think I did)
Post by: saturated on October 13, 2024, 11:28:43 PM
Alright well never mind  :loco

I'm pulling the plug on this one for now

:grr

There was one cool thing that happened though I hooked up a diode LED to try and get a half wave and I noticed the thing was flashing
At first I was like wow what is this must be a special flasher diode then I realized what the deal was and noticed I could change the rate of flash by varying frequency and vary the brightness with the voltage
IMG_20241013_221441740.jpg

IMG_20241013_221428404.jpg

 <3)


Title: Re: I thought I would filter some frequency (but I don't think I did)
Post by: Tassieviking on October 14, 2024, 11:38:29 AM
Keep learning grasshopper  :)
Title: Re: I thought I would filter some frequency (but I don't think I did)
Post by: saturated on October 14, 2024, 11:54:11 AM
Thanks my friend

Not to open a can of worms but I did learn a few more things

And this may be wrong yet still but going forward

THE OSCILLOSCOPE IS NOT 🚭🚫 PART OF YOUR CIRCUIT.  SET UP YOUR CIRCUIT WITH COMPONENTS AND COOL STUFF LIKE GROUND  :loco HAVE COOL STUFF LIKE CURRENT RUNNING THRU IT.  LEAVE THE SCOPE ALONE UNTIL YOU HAVE ESTABLISHED A FUNCTIONING ⭕ CIRCUIT.  :lmao: YOU ARE FURTHER PROHIBITED 🚭 FROM USING A SCOPE UNTIL YOU HAVE VERIFIED ANY AND EVERYTHING POSSIBLE WITH YOUR MULTIMETER  :dbtu:

Title: Re: I thought I would filter some frequency (but I don't think I did)
Post by: g1 on October 14, 2024, 03:21:47 PM
Yes, good points about setting up the circuit.
You essentially had the choke/ballast as the load for the generator.  That is not going to do much in the way of filtering.
Look up LC filters (inductor/capacitor) and set up some in series or parallel with the generator.
Even how you did it, but with a resistor in series with the choke should do something.
Title: Re: I thought I would filter some frequency (but I don't think I did)
Post by: saturated on October 16, 2024, 07:42:44 PM
Quote from: Tassieviking on October 14, 2024, 11:38:29 AMKeep learning grasshopper  :)

Thanks I actually did learn a couple things

When I was trying to get a rectified wave on my scope I would set up my circuit like below and wonder why I didn't have a half wave
IMG_20241016_183206444.jpg
It took me a while to figure out there is no half wave or any voltage at all because anything after the diode is at ground potential  :lmao:

So next step put something in between the diode and ground so there is some voltage left to look at
IMG_20241016_183302156.jpg

And it worked I was able to get a nice picture on that big diode
IMG_20241016_144156593.jpg

My bird's nest
IMG_20241016_144215451_HDR.jpg
It helped earlier having an LED to kinda see what was up and what was cool was doing a diode check on the LED with my multimeter seeing it light up  8|