• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

yaqin 100b with 2 different kt88 valves 2 are Genelex Gold Lion and 2 are Svetlena wi

Rodeodave gave the best answer. Watch those Gold Lion KT88's though. I have not used them myself but I have read many reports of premature failure but of course that could be caused by miss-use. You should bias the valves for 0.55V on the test points provided. The bias adjust controls work in reverse to what is expected, i.e. turning the control anti-clockwise INCREASES the current through the valve rather than decrease.
 

youngie

Member
2012-01-14 2:54 pm
ok thank you so much. so really i should get a little better sound from to different brands. i hope they are better than the stock valves i have cheers lee
This should work, yes, using one pair per channel should give the best results because tubes of the same manufacturer are more likely to have similar specs.

The correct bias settings should be indicated in the schematic.
 

youngie

Member
2012-01-14 2:54 pm
thank you for your reply so i should set both valves at 0.55v it just everywhere i read most people say run them higher because they like it the kt88 valves cheers lee
Rodeodave gave the best answer. Watch those Gold Lion KT88's though. I have not used them myself but I have read many reports of premature failure but of course that could be caused by miss-use. You should bias the valves for 0.55V on the test points provided. The bias adjust controls work in reverse to what is expected, i.e. turning the control anti-clockwise INCREASES the current through the valve rather than decrease.
 

youngie

Member
2012-01-14 2:54 pm
would a power amp be any good with the yaqin and xiaing sheng 728a pre amp to help the bass sound a bit smother.. and what valves would be good to replace in the xiang sheng 728a pre amp any idears are welcome kind regards lee
ok i have the new valves now. i am going bias them today on the amp witch is positive and negative red or black. and also what setting should i put my mulit reader on kind regards mr young