I try to get the input filter to below 2Hz. RC=~90mS at the input demands that the PSU ~+-20mF for 8ohm speaker. Choices.
Hi AndrewT,
Thanks for the input, but it seems that i lack the theory background to fully understand what you are saying...🙁
I will put an input cap now, it must be an non-polarity electrolytic or MKP?I guess voltage rating don't need to be high (16v would do)?
Thanks for the input, but it seems that i lack the theory background to fully understand what you are saying...🙁
I will put an input cap now, it must be an non-polarity electrolytic or MKP?I guess voltage rating don't need to be high (16v would do)?
With a 1uF NPN (i only have 1uF and 2.2uF), bass is better, DC is down to ~5mV!!!
With a 1uF MKP 630v M-cap instead, DC is the same but it sounds
a bit better.
With a 1uF MKP 630v M-cap instead, DC is the same but it sounds
a bit better.
Hi,
for what I call acceptable bass, I would use 4u7F at the input of a Zin=20k power amplifier. or 2u2//2u2F for Zin=22k.
But, that requires the other RCs to be reselected.
Adjusting the 22k will get the 5mV offset even lower. Then you can monitor what it does cold and warm and hot and decide where you want it to settle for your operating conditions.
Once you have this information you can calculate the cold, warm and hot input offset currents for that chipamp (and pre-measure all your other chipamps). Now you have the information you need to let you start designing a DC coupled amplifier with it's protection systems that are required to save your speakers.
for what I call acceptable bass, I would use 4u7F at the input of a Zin=20k power amplifier. or 2u2//2u2F for Zin=22k.
But, that requires the other RCs to be reselected.
Adjusting the 22k will get the 5mV offset even lower. Then you can monitor what it does cold and warm and hot and decide where you want it to settle for your operating conditions.
Once you have this information you can calculate the cold, warm and hot input offset currents for that chipamp (and pre-measure all your other chipamps). Now you have the information you need to let you start designing a DC coupled amplifier with it's protection systems that are required to save your speakers.
AndrewT thanks for the help,
i'm far from designing an amp, but with your guys help i'm getting better🙂
I 'm using my PC sound card and WMP for testing now, and the primitive way of testing the input caps is the following:
i'm changing the equalizer's first 2 bars (31Hz and 61Hz) setting from max to min and hear the bass on the speaker.Changing the 61Hz bar always makes a difference.
when using 2,2uF input cap (MKP), changing the 31Hz bar does nothing.
using 1uF cap , i get more bass when bar is max
Using 0,47uF cap even better.
I know it's a dumb way to test, but that's the best i can do
i'm far from designing an amp, but with your guys help i'm getting better🙂
I 'm using my PC sound card and WMP for testing now, and the primitive way of testing the input caps is the following:
i'm changing the equalizer's first 2 bars (31Hz and 61Hz) setting from max to min and hear the bass on the speaker.Changing the 61Hz bar always makes a difference.
when using 2,2uF input cap (MKP), changing the 31Hz bar does nothing.
using 1uF cap , i get more bass when bar is max
Using 0,47uF cap even better.
I know it's a dumb way to test, but that's the best i can do
Since you like the MKP, do you have a second pair of 470nF MKP?
Add them in parallel to the single MKP to give 0.94uF on each channel.
This extends the bass response one octave down. This should be audible on some music tracks and very audible on some sound effects tracks/videos.
Add them in parallel to the single MKP to give 0.94uF on each channel.
This extends the bass response one octave down. This should be audible on some music tracks and very audible on some sound effects tracks/videos.
Thanks AndrewT, i'll try that when i get the caps.
Another thing: i use an Alps 50K log pot, the front side is metal (back is plastic). When i touch the "wheel" of the pot to turn it, i get a noise to the speaker that depends to where the pot is set.
Starting from 48,8K (volume min) , almost no noise until 48,4 that noise starts build up, peaks at about 28K, then starts dropping until 44 Ohms that it's gone (all the way up to max volume, 0R).
Will this be fixed when i put the amp in a case and ground it properly? I'm worried because that metal side of the pot will make contact with the case chassis when i assemble the case.
Another thing: i use an Alps 50K log pot, the front side is metal (back is plastic). When i touch the "wheel" of the pot to turn it, i get a noise to the speaker that depends to where the pot is set.
Starting from 48,8K (volume min) , almost no noise until 48,4 that noise starts build up, peaks at about 28K, then starts dropping until 44 Ohms that it's gone (all the way up to max volume, 0R).
Will this be fixed when i put the amp in a case and ground it properly? I'm worried because that metal side of the pot will make contact with the case chassis when i assemble the case.
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The metal parts of the potentiometer should be grounded. Some models come with solderable pins for that. Your model seems to rely on grounding through the screws to the chassis. If you get hum, isolate it from the chassis with plastic film and using plastic screws. then ground it with a separate wire to the signal ground star-point.
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