2. amps-preamps
  3. 1172525591

Tube upgrades for Jolida 502B?

I realize this is something that has come up before, though in searching the archives I didn't come away with a clear path forward. My amp is completely stock and came equipped with Sovtek 6550s. Using it to drive Totem Forest speakers. I contacted Jolida. They recommend KT88s. Their reply is a bit unclear but they might be suggesting Electro Harmonix. They also indicate reliability issues with Chinese KT88s. Response Audio (Jolida dealer and modder) recommends Shuguang KT88s (Chinese). The Tube Store recommended JJ Tesla KT88s on the strength of their great imaging and deep bass (more bass being something I was looking for). I was initially leaning towards SED Winged "C" 6550s. Now I am a bit more confused. I'm curious about KT88 vs 6550 sonics and reliability differences. Thanks in advance to any one willing to take the time to share their experience and preferences.
128x128ghosthouse

Showing 6 responses by tomtab

tomtab
97 posts
 
question about kt120 tubes. i spoke to walter from underwoodwall the other day and asked if i can use 120 tubes in my 502p amp. he said no. i dident ask why but i see other folks here using them. so, whats the story?? is it safe to use kt 120 in this amp. and if yes, do you still bias so the led,s go on??. i understand they use more current or something so wondering if the 502p power supply stiff enough for them. thanks
tomtab
97 posts
 
thanks wolf, i was hoping to hear from you about this. and what about biasing. just set it till the led light and thats it. couldent these tubes go for alittle more. i think these amps are set for 50 mg's what would happen if we crank it up alittle past the led setting til say the light goes off. would that be like going to 60 or 70.
tomtab
97 posts
 
thanks guys for the info. 120's will be going in. just one step closer to the promised audio land.
tomtab
97 posts
 
the 120's are not working as hard as 88's or 90's would be. and who said that this amp can be run in mono?? there is nothing in the manual about this. and if they can be run in mono, what is the speaker hookup. + to +, - to + ??
tomtab
97 posts
 
i did call jolida about it. heres what they said. you need a y cable to plug into both inputs. then short wires to tie the negative taps together and short wire to connect the 4 or 8 ohm taps together (just the ones you are using,not both or boom) then run speaker to one set of taps. basically running the left and right speaker outs in parallel conection. also said will not get 120 watts,more like 100 this is from michael allen of jolida
tomtab
97 posts
 
yes a mono switch on the back would be nice. then something similar to car amps for speaker connection. left channel negative and right channel positive. done!! i dont get the only 100 watt rating also. did you or anybody notice a power increase using the kt120 tubes. if you read the spec's for the 120's everybody has you believing they can make 120-150 watts a pair. im guessing thats if the amp was designed around the 120 tube to get the maximun out of them. im betting a 60 watt amp will maybe put out 70 with the 120's
More to discover