||4th December 2016 04:08 PM
ys preamp mods
Good afternoon from Greece!! I have the same preamplifier , i buy from ebay before 5 or 6 years. I have the the version with ss power supply and 6x4 tube. The machine came with shuguang 12ax7 tubes, with red letters and a JAN sylvania 6x4 tube.The sound it is not bad but i do not like it The first thing in my mind it is the tubes! I tested many tubes like EH,Mullard reissue,NOS Telefunken,and russian 6n2p-ev voskhod, I change the 6x4 tube with a hitachi tube from ebay! The sound improves drammatically but again i dont like it!! I have problem with the bass,to much compression especially in heavy bass program. The best sounding tubes from me,it is russian military tubes,and mullard reissue tubes,big surprise for me! The NOS Telefunken tubes has a very good sound but nothing special to me!!The problem with the compressed bass is the 6X4 tube. In heavy bass sound this tube drops too many volts,about 20-30v which is no good. I do not like this,and pulled out the tube,i jumper the anode and cathode of the base of the tube and the problem solved!! The sound is much better now,better sound stage and no more compressed sound! I like this preamplifier very much,no problems at all,i like the sound from the russian 6n2p-ev tubes it is clear and natural,more live with a huge stereo image. These tubes is very strong,and beefy,no problems at all after 5 years of hard use,no degradation in sound,no problem at all! If anyone like to use these russian tubes must change the filament wiring it is different,google it to find it, i don not remember now,no other changes,the hardware quality,is very good from me,no failures at all! It is a very good preamplifier,very good price.and excellent sound with simple circuit and easy mods!