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What I'm gathering from this mod is that we're bypassing the speaker cap and dropping the audio across D63/R228/R194 junction. What this looks like to me is a parallel negative limiter circuit with slight clamping action. By changing the resistance we change what negtive portion the limit will happen at? I hope I didn't confuse myself with my understanding here, Navy electronics training is vague when it comes to actual applications of circuit theory. Just for adding to discussion, I was working on a 148/2000 style of board and it had this device that was able to control your positive and negative peaks to over 200 and limit the 100 on the negative side. This device also allows you to play with tube emulation, carrier and a few other things, I will let your imagination tell you what this is. Anyways what it did was bypass the AF amp and drop the audio on to the regulator which was isolated from radio VCC. The regulator drove the final however the driver was volted and resembled a tube modulator/PA setup if you may. Back to this mod, adjusting the resistor value, to me seems to control the limit "compression" happens at ie. the negative peaks. I wonder if placing a potentiometer in place of R228 and adjusting for the right negative limit be an option? I did the OP mod with changing to a 1K and a .47uF Mica cap and was able to adjust for 180 to 200% positive peaks, however the negative never reached the reference line(100%). It was more like 85 to 90% and acting like it was in severe cutoff. The audio was muffled and I had to back the mic gain down alot to keep the positive peaks from flat topping. I theorize the value of the cap is not as important as the value of the resistor in this mod. The cap provides DC isolation and passes the Audio(AC signal) over to the regulator. The value of the cap should determine the frequency of audio being passed or coupled. My question is shouldn't we disconnect C174 so that it doesn't provide alternate audio from trying to also reach the regulator? Anyways, great discussion, I hope I added something positive to this post while limiting the negative peaks...LOL
Virtual Labs - Dayalbagh Educational Institute - Agra - Theory
The first link reminds me of this circuit, parallel negative limiter. The second link is what my waveform looked like after this mod.

<blockquote data-quote="711" data-source="post: 461484" data-attributes="member: 6623">What I&#039;m gathering from this mod is that we&#039;re bypassing the speaker cap and dropping the audio across D63/R228/R194 junction. What this looks like to me is a parallel negative limiter circuit with slight clamping action. By changing the resistance we change what negtive portion the limit will happen at? I hope I didn&#039;t confuse myself with my understanding here, Navy electronics training is vague when it comes to actual applications of circuit theory. Just for adding to discussion, I was working on a 148/2000 style of board and it had this device that was able to control your positive and negative peaks to over 200 and limit the 100 on the negative side. This device also allows you to play with tube emulation, carrier and a few other things, I will let your imagination tell you what this is. Anyways what it did was bypass the AF amp and drop the audio on to the regulator which was isolated from radio VCC. The regulator drove the final however the driver was volted and resembled a tube modulator/PA setup if you may. Back to this mod, adjusting the resistor value, to me seems to control the limit &quot;compression&quot; happens at ie. the negative peaks. I wonder if placing a potentiometer in place of R228 and adjusting for the right negative limit be an option? I did the OP mod with changing to a 1K and a .47uF Mica cap and was able to adjust for 180 to 200% positive peaks, however the negative never reached the reference line(100%). It was more like 85 to 90% and acting like it was in severe cutoff. The audio was muffled and I had to back the mic gain down alot to keep the positive peaks from flat topping. I theorize the value of the cap is not as important as the value of the resistor in this mod. The cap provides DC isolation and passes the Audio(AC signal) over to the regulator. The value of the cap should determine the frequency of audio being passed or coupled. My question is shouldn&#039;t we disconnect C174 so that it doesn&#039;t provide alternate audio from trying to also reach the regulator? Anyways, great discussion, I hope I added something positive to this post while limiting the negative peaks...LOL<a href="http://evalidate.freehostia.com/diode/Diode_Limiter/diodeLimiterTheory.html" target="_blank">Virtual Labs - Dayalbagh Educational Institute - Agra - Theory</a><a href="http://www.circuitstoday.com/wp-content/uploads/2009/10/Output-Waveform-Positive-Clipper-and-Negative-Clipper.jpg" target="_blank"><img src="http://www.circuitstoday.com/wp-content/uploads/2009/10/Output-Waveform-Positive-Clipper-and-Negative-Clipper.jpg" alt="" class="fr-fic fr-dii fr-draggable " data-size="" style="" /></a>The first link reminds me of this circuit, parallel negative limiter. The second link is what my waveform looked like after this mod.</blockquote>

[QUOTE="711, post: 461484, member: 6623"] What I'm gathering from this mod is that we're bypassing the speaker cap and dropping the audio across D63/R228/R194 junction. What this looks like to me is a parallel negative limiter circuit with slight clamping action. By changing the resistance we change what negtive portion the limit will happen at? I hope I didn't confuse myself with my understanding here, Navy electronics training is vague when it comes to actual applications of circuit theory. Just for adding to discussion, I was working on a 148/2000 style of board and it had this device that was able to control your positive and negative peaks to over 200 and limit the 100 on the negative side. This device also allows you to play with tube emulation, carrier and a few other things, I will let your imagination tell you what this is. Anyways what it did was bypass the AF amp and drop the audio on to the regulator which was isolated from radio VCC. The regulator drove the final however the driver was volted and resembled a tube modulator/PA setup if you may. Back to this mod, adjusting the resistor value, to me seems to control the limit "compression" happens at ie. the negative peaks. I wonder if placing a potentiometer in place of R228 and adjusting for the right negative limit be an option? I did the OP mod with changing to a 1K and a .47uF Mica cap and was able to adjust for 180 to 200% positive peaks, however the negative never reached the reference line(100%). It was more like 85 to 90% and acting like it was in severe cutoff. The audio was muffled and I had to back the mic gain down alot to keep the positive peaks from flat topping. I theorize the value of the cap is not as important as the value of the resistor in this mod. The cap provides DC isolation and passes the Audio(AC signal) over to the regulator. The value of the cap should determine the frequency of audio being passed or coupled. My question is shouldn't we disconnect C174 so that it doesn't provide alternate audio from trying to also reach the regulator? Anyways, great discussion, I hope I added something positive to this post while limiting the negative peaks...LOL [URL="http://evalidate.freehostia.com/diode/Diode_Limiter/diodeLimiterTheory.html"]Virtual Labs - Dayalbagh Educational Institute - Agra - Theory[/URL] [URL="http://www.circuitstoday.com/wp-content/uploads/2009/10/Output-Waveform-Positive-Clipper-and-Negative-Clipper.jpg"][IMG]http://www.circuitstoday.com/wp-content/uploads/2009/10/Output-Waveform-Positive-Clipper-and-Negative-Clipper.jpg[/IMG][/URL] The first link reminds me of this circuit, parallel negative limiter. The second link is what my waveform looked like after this mod. [/QUOTE]

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