6J5 substitute 6SN7 for 300B Audio Note Conqueror

[for_p1]

If replacing those caps with higher voltage rating then do I need 400VDC for both? Or only need 400VDC for the 100uf cap?
Also, do I need very good audio grade cap for those position of the two tubes?

Only 100uF. For other one you should be good with 25 volts rating.

If you decide to use resistors split in half, like was mentioned above - you need to double capacitance to keep the same frequency response.

 

[pochago]

Only 100uF. For other one you should be good with 25 volts rating.

If you decide to use resistors split in half, like was mentioned above - you need to double capacitance to keep the same frequency response.

Can you explain with more detail?
Mark was suggesting to split the 330ohm resistor into 2 x 150ohm or 2x 160ohm and connecting with the same 470uf cap in between. But you are suggesting to use double capacitance which is 940uf? If that's the case, then can I use 1000uf?
For resistor, does it matter if I use the cheapest no brand resistor that I can easily get from a local shop. Those probably cost only $1 for 10 and no shipping. I can also order some Vishay from Digikey for about $.5 each + shipping. The price is not really the issue. Just quick and easy buying from local if the brand name resistor won't make much different.

 

[for_p1]

Can you explain with more detail?
Mark was suggesting to split the 330ohm resistor into 2 x 150ohm or 2x 160ohm and connecting with the same 470uf cap in between. But you are suggesting to use double capacitance which is 940uf? If that's the case, then can I use 1000uf?
For resistor, does it matter if I use the cheapest no brand resistor that I can easily get from a local shop. Those probably cost only $1 for 10 and no shipping. I can also order some Vishay from Digikey for about $.5 each + shipping. The price is not really the issue. Just quick and easy buying from local if the brand name resistor won't make much different.

See attached picture. I suggest to use metal film resistors.

 

[pochago]

There is no harm running the amp with out the caps in it , in the long term four more resistors will be added to each channel ,two will added to each cathode of the 6sn7 , you need two 150 ohm half watt resistors , they will replace the 300 ohm resistor . the 470uf cap will go from the center point of the two 150 ohm resistors to ground , on the second half of the 6sn7 two 10k 1 watt resistors in series 20K to the cathode will replace the 39k resistors in parallel (18K) the 100uf will go to the center point of the two 10K resistors to ground .

That will decrease the gain of the 6SN7's .

A 6sn7 amplification factor in this case is 20 X 20 for a total of 400 , a 6SF5 has an amp factor of 100 . Parallel wired 6SL7 or 6SC7 have an amp factor of 70 . parallel wired 6SN7 has an amp factor of 20 .

Your amp only needs the front end to have an amp factor of 70 to 150 , but how it is wired it is close to 400 .

Here is an update about my modification to reduce the gain of my Audio Note Conqueror. Before I got the chance to do the modification, the amp developed a problem where the left channel has no sound. But thanks to the help from Mark, I narrowed down the faulty part and fixed it. I also replaced all the electrolytic capacitors since the unit is 15yrs old. After fixed the problem and renewed all the caps, I applied the mod as suggested by Mark. I used 2 x 160ohm resistor instead of the 150ohm suggested by Mark. However, I believe that it is not necessary to try keeping the value closer to the original since the purpose of this mod is to change the gain. The modification is a success. It reduced the gain which eliminated the hum/noise. The amp now sound very sweet with my high efficient full range open baffle.

 

[Lavane]

Glad to hear it all worked out. :thmbsp:

 

[battradio]

Glad it all worked out for and i was of some help .