Hi, Juma just finished assembling the post.67 chematic preamp V+/V- 33.5 vdc, Offset OK, added 220R resistor to R4-R5 now I kindly ask you how I can increase the gain (resistor value to be changed) since to hear the music at a decent level I have to turn the knob to about 1/2 volume
pot is Alps Black 50K.Best regards Sergio Italy
pot is Alps Black 50K.Best regards Sergio Italy
Lowering the R6 will increase the gain and the distortion too.
Increasing the R9 will increase the gain also but it it will increase the output impedance (Zout) too.
Zout is determined by value of R9 and it is already very high (6k8 paralleled with Zin of the next stage).
I don't know what is your next stage (amplifier? , pot?) and what is its Zin, but it's possible that you don't lack gain - it might be that your next stage "eats" the gain (low Zin) so you actually might need a buffer rather than more gain in the preamp.
Since you are hiding data about your exact configuration it's hard to help you.
Increasing the R9 will increase the gain also but it it will increase the output impedance (Zout) too.
Zout is determined by value of R9 and it is already very high (6k8 paralleled with Zin of the next stage).
I don't know what is your next stage (amplifier? , pot?) and what is its Zin, but it's possible that you don't lack gain - it might be that your next stage "eats" the gain (low Zin) so you actually might need a buffer rather than more gain in the preamp.
Since you are hiding data about your exact configuration it's hard to help you.
OK, in that case the circuit needs a bit of rearrangement:
Attachments
This one (2SK209 BL) will do nicely:
https://www.digikey.com/en/products...nductor-and-storage/2SK209-BL-TE85L-F/4305046
https://www.digikey.com/en/products...nductor-and-storage/2SK209-BL-TE85L-F/4305046