Has anyone changed these from 150K to 100K? Bob had recommended that on a previous post. I'm running KT88.
If needed, then what type and wattage? Dale
If needed, then what type and wattage? Dale
3 posters
R29 - 32 ST-120 driver board
Dale Stevens- Posts : 206
Join date : 2014-07-06
Age : 75
Location : Loris, SC
Bob Latino- Admin
- Posts : 3276
Join date : 2008-11-26
Location : Massachusetts
Dale Stevens wrote:Has anyone changed these from 150K to 100K? Bob had recommended that on a previous post. I'm running KT88.
If needed, then what type and wattage? Dale
Hi Dale,
It won't really make any difference in the amp if you switch from 150K to 100K as long as you can bias the amp properly. The VTA M-125's always had 100K in R30 and R32. On a recommendation from Roy the newer ST-120's changed to 100K for these 4 spots about 5 or 6 years ago. 100K will allow a little more current available to bias the four output tubes in the ST-120. In my own personal ST-120 from 2008 I still have the 150K resistors in there. My amp biases fine .. Never had a problem ..
Bob
Dale Stevens- Posts : 206
Join date : 2014-07-06
Age : 75
Location : Loris, SC
Thx, Mr. Bob. My bias is spot on; Variac @ 117vac. Amp is August, 2014. Great product. Dale
Roy Mottram- Admin
- Posts : 1838
Join date : 2008-11-30
certain modern brands of KT88s just don't want to hold a steady bias with 150K resistors, and 100K fixes that problem.
Similar to the fact that you need to use 50K resistors with KT120/150 tubes.
Similar to the fact that you need to use 50K resistors with KT120/150 tubes.