diode bridge rectifier as a clipper?

Frequent question abouts LED and other types of diodes.
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HydrozeenElectronics
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Post by HydrozeenElectronics »

Yes that's it. I'm really excited to see how that would compare to the Rectifier.

Thanks

DrNomis wrote:
HydrozeenElectronics wrote:DrNomis,

could you do one more test? I'm interested in seeing what three GE diodes in series pared up shunted to ground would look like vs the rectifier set up. In the rectifier the signal travels through three diodes but it might be changing the signal a little. I would like to see the difference.

thanks

I'm assuming this is the circuit configuration you mean,I don't have any Ge diodes so I'll use some Ge Transistors instead,results should be the same... :)

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Post by DrNomis »

Okay,here's an Oscilloscope Screenshot for the Ge Diode Clipper Circuit,this is what I saw on the screen,signal level going into the circuit was 1kHz at approximately 14V Peak To Peak Level.... :)


Notice how one part of the waveform is more rounded than the other?.... :)
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Ge Diode Clipper Screenshot
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Post by Greg »

14V or 1.4V ?
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Post by DrNomis »

Greg_G wrote:14V or 1.4V ?


14V pp.... :)


I used my scope to measure the peak-to-peak level after I took the screenshot pic,the channel gain was set to 2 V per 1cm division,and I counted about 7x1cm vertical graticule divisions,which gave a reading of about 14V,so I had to drive the Ge diode clipper circuit pretty hard to get it to clip as shown in the screenshot,no op-amps were used in any of the screenshots... :)


What you see on the above screenshot is the pic I took before I measured the signal level,because of the clipping,the signal level is going to be lower,so to measure the signal level going into the clipper,i had to disconnect the Function Generator from the circuit,and feed the output straight into the scope.... :)



I could quite easily do all the clipping screenshots again with a basic op-amp amplifier circuit included if you want... :)
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Post by Greg »

A germanium diode has a Vf of about 0.3 volts, so wouldn't 3 in series limit the voltage swing to about 0.9 volts ?.
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Post by DrNomis »

Greg_G wrote:A germanium diode has a Vf of about 0.3 volts, so wouldn't 3 in series limit the voltage swing to about 0.9 volts ?.

Yes,that's true,however,the test signal level of 14V,which I quoted,is the signal level coming from the Function Generator before it gets clipped by the diodes,to measure this,I had to disconnect the signal from the circuit,and feed it unclipped straight into the input of the scope,if I had just kept it connected to the circuits,the signal clipping would have given me misleading results since the signal clipping would have reduced the signal level,what you see in the screenshot is the signal being clipped by the diodes,not what's actually coming out of the Function Generator,I know it's a bit confusing... :)


I think the actual signal levels aren't really that important,what is important is the clipping characteristics,as you see,the Ge diodes have a softer turn-on knee,I have found in practice that you actually need more signal level to get two back-to-back Ge diodes to clip because of the soft-knee turn-on characteristic,since it is a more gradual process... :)


See,because of the softer turn-on knee,it is harder to determine where the Diodes start clipping the signal,whereas with Si diodes,it's a different story,the signal remains unclipped before it gets to a certain level,then the Si diodes suddenly start conducting.... :)

Yeah,I know it's a bit wierd... :)


Well,that's best way I can explain it anyway,I may be totally wrong about that though.... :)
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Post by ansil »

bajaman wrote:I wonder what a similar configuration of LEDs would sound like :hmmm:
bajaman
didn't scope it but louder was the result on my h and k

they use this idea on most of their ss amps

i can get all their schemes if anyone wants to host them.

ed

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Post by HydrozeenElectronics »

Thank you so much this is really cool. The rectifier set up has a more smoother rounder waveform. The other has kind of a "peaky" looking wave form. Now I'm guessing that some of that is caused by some feedback that cancels that peak out on the rectifier set up. Does that seem logical. To my ears the rectifier sounds much smoother and better but I'm curious to know just exactly why?

thanks again for doing this for us. I think a lot of people are going to be helped by this.


DrNomis wrote:Okay,here's an Oscilloscope Screenshot for the Ge Diode Clipper Circuit,this is what I saw on the screen,signal level going into the circuit was 1kHz at approximately 14V Peak To Peak Level.... :)


Notice how one part of the waveform is more rounded than the other?.... :)

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Post by DrNomis »

HydrozeenElectronics wrote:Thank you so much this is really cool. The rectifier set up has a more smoother rounder waveform. The other has kind of a "peaky" looking wave form. Now I'm guessing that some of that is caused by some feedback that cancels that peak out on the rectifier set up. Does that seem logical. To my ears the rectifier sounds much smoother and better but I'm curious to know just exactly why?

thanks again for doing this for us. I think a lot of people are going to be helped by this.


DrNomis wrote:Okay,here's an Oscilloscope Screenshot for the Ge Diode Clipper Circuit,this is what I saw on the screen,signal level going into the circuit was 1kHz at approximately 14V Peak To Peak Level.... :)


Notice how one part of the waveform is more rounded than the other?.... :)

Probably,but I reckon that the rounding of the lower part of the waveform may be due to the fact that the diode characteristics might be slightly different for each Ge diode.... :)

Anyway,glad I was able to help out with this.... :)
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Post by Greg »

I guess the point I've been trying to make is that:
at 14 volts it gives a very nice trace, but it's not indicative of the effect you'd get in an effect pedal.
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Post by DrNomis »

Greg_G wrote:I guess the point I've been trying to make is that:
at 14 volts it gives a very nice trace, but it's not indicative of the effect you'd get in an effect pedal.

Yeah,I see your point,and you're right,I was only reporting what I was seeing on my scope screen,but,those results I got may just be valid only for the test circuits I constructed on my breadboard,and also the way I hooked my Hameg Function Generator and Scope up to the circuit,it's a good indication of what the signal clipping looks like anyway.... :)


The method I used to obtain the screenshots tends to be very subjective.... :)
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Post by Greg »

DrNomis wrote:
Greg_G wrote:I guess the point I've been trying to make is that:
at 14 volts it gives a very nice trace, but it's not indicative of the effect you'd get in an effect pedal.

Yeah,I see your point,and you're right,I was only reporting what I was seeing on my scope screen,but,those results I got may just be valid only for the test circuits I constructed on my breadboard,and also the way I hooked my Hameg Function Generator and Scope up to the circuit,it's a good indication of what the signal clipping looks like anyway.... :)


The method I used to obtain the screenshots tends to be very subjective.... :)
I understand.. and appreciate you doing them.
I think the tests would be more useful if you chose an input level similar to what you might find coming out of the first stage of an opamp clipper.. and also used the same input level to test germanium, silicon and LED, so you can see how each would behave in the same condition.
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Post by DrNomis »

Greg_G wrote:
DrNomis wrote:
Greg_G wrote:I guess the point I've been trying to make is that:
at 14 volts it gives a very nice trace, but it's not indicative of the effect you'd get in an effect pedal.

Yeah,I see your point,and you're right,I was only reporting what I was seeing on my scope screen,but,those results I got may just be valid only for the test circuits I constructed on my breadboard,and also the way I hooked my Hameg Function Generator and Scope up to the circuit,it's a good indication of what the signal clipping looks like anyway.... :)


The method I used to obtain the screenshots tends to be very subjective.... :)
I understand.. and appreciate you doing them.
I think the tests would be more useful if you chose an input level similar to what you might find coming out of the first stage of an opamp clipper.. and also used the same input level to test germanium, silicon and LED, so you can see how each would behave in the same condition.

Well,I was thinking of repeating the tests but making it more realistic by including a basic amplifier in the circuit,I'm not really doing much this weekend,and I could probably build each circuit in about 10 minutes or so,so I have heaps of time on my hands,okay I'll do a repeat and see what results we get this time,might be more interesting.... :)
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Post by Greg »

DrNomis wrote:Well,I was thinking of repeating the tests but making it more realistic by including a basic amplifier in the circuit,I'm not really doing much this weekend,and I could probably build each circuit in about 10 minutes or so,so I have heaps of time on my hands,okay I'll do a repeat and see what results we get this time,might be more interesting.... :)
Awesome.. :thumbsup
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Post by HydrozeenElectronics »

That would really be great. Thanks again. :D
DrNomis wrote:
Greg_G wrote:
DrNomis wrote:
Greg_G wrote:I guess the point I've been trying to make is that:
at 14 volts it gives a very nice trace, but it's not indicative of the effect you'd get in an effect pedal.

Yeah,I see your point,and you're right,I was only reporting what I was seeing on my scope screen,but,those results I got may just be valid only for the test circuits I constructed on my breadboard,and also the way I hooked my Hameg Function Generator and Scope up to the circuit,it's a good indication of what the signal clipping looks like anyway.... :)


The method I used to obtain the screenshots tends to be very subjective.... :)
I understand.. and appreciate you doing them.
I think the tests would be more useful if you chose an input level similar to what you might find coming out of the first stage of an opamp clipper.. and also used the same input level to test germanium, silicon and LED, so you can see how each would behave in the same condition.

Well,I was thinking of repeating the tests but making it more realistic by including a basic amplifier in the circuit,I'm not really doing much this weekend,and I could probably build each circuit in about 10 minutes or so,so I have heaps of time on my hands,okay I'll do a repeat and see what results we get this time,might be more interesting.... :)

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