I started the circuit excatly like the application circuit in datasheet but it was lack of bass and has ringing on output when I increased the volume. The ringing problem was solved using zobel network at output but still lack of bass. I understand that this LM3875 has lower input impedance and does it mean that I need to add additional opamp stages to make it becomes high impedance?
Not in the datasheet
The feedback network is not in the datasheet.
Your circuit has a gain of 1 at DC and a gain of 20 or so beyond the pole frequency and I really haven't taken the trouble to figure out what it really does.
Since people have found the feedback loop of the gainclone is THE MOST IMPORTANT element required to accomplish great sound, you should first try what has been found to work well and then experiment afterwards. What works well is a good, precision resistor of 20k (for your design) soldered extremely closely between pins 3 and 8. No capacitors on pin 8 at all unless you have really bad DC offset and then you should seek advice first.
Read the huge history here or just follow what BrianGT has done. Copy as much of his schematic as you can.
-Robert
The feedback network is not in the datasheet.
Your circuit has a gain of 1 at DC and a gain of 20 or so beyond the pole frequency and I really haven't taken the trouble to figure out what it really does.
Since people have found the feedback loop of the gainclone is THE MOST IMPORTANT element required to accomplish great sound, you should first try what has been found to work well and then experiment afterwards. What works well is a good, precision resistor of 20k (for your design) soldered extremely closely between pins 3 and 8. No capacitors on pin 8 at all unless you have really bad DC offset and then you should seek advice first.
Read the huge history here or just follow what BrianGT has done. Copy as much of his schematic as you can.
-Robert
1) I am using 10,000uF caps for both rails but do not have the 100uF and 0.1uF caps at chip.
2) I started the circuit as shown in datasheet but later change to the circuit I posted here because of ringing problem. then I found that is the zobel network that solved the ringing problem and not the feedback loop. Anyway, both version of schematics did not give much bass at all.
3) Do I need to add in tone control to boost the bass? Or, this gc himself is capable to produce "ceiling-booming" bass?
4) I am using a tube preamp which use 5687 as driver tube. Will this caused problem on the bass?
Thanks.
2) I started the circuit as shown in datasheet but later change to the circuit I posted here because of ringing problem. then I found that is the zobel network that solved the ringing problem and not the feedback loop. Anyway, both version of schematics did not give much bass at all.
3) Do I need to add in tone control to boost the bass? Or, this gc himself is capable to produce "ceiling-booming" bass?
4) I am using a tube preamp which use 5687 as driver tube. Will this caused problem on the bass?
Thanks.
In response to your bass issue, IF youve setup the feedback/gain correctly so ITs freq range is say 20-20000 at -3db, than it should produce the correct level of bass from thos freqs. ... anything but would afaiak be classed as distortion, should replicate the input signal !
-ed i dont think i made my point quite clear there... I was trying to say you should not need any tone controls to achive correct bass, only to ytailor any fetish you have with 'extra' bass
-ed i dont think i made my point quite clear there... I was trying to say you should not need any tone controls to achive correct bass, only to ytailor any fetish you have with 'extra' bass
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