arnoldc wrote:jojo, what confused me was your previous post to get the plate current, which was 50mA, and then you followed up with taking away the screen current from it.
i guess we agree on the same thing though
aprub!
arnoldc wrote:jojo, what confused me was your previous post to get the plate current, which was 50mA, and then you followed up with taking away the screen current from it.
i guess we agree on the same thing though
m_shoe_maker wrote:Naku po Nataranta na tong ST70 user.
Anyway, simple lang ang solution ko.........
Master Hyper, what reading from my volt meter will I bias my ST70
Simpleng tanong sa Tube God, and his answer will be my Gospel Truth.
hypertriode wrote:m_shoe_maker wrote:Naku po Nataranta na tong ST70 user.
Anyway, simple lang ang solution ko.........
Master Hyper, what reading from my volt meter will I bias my ST70
Simpleng tanong sa Tube God, and his answer will be my Gospel Truth.
just my opinion fritz: i agree with john that NOS EL-34's can take the punishment inflicted by high or bias settings while new production ones can't. also take into account the stock stereo 70 transformer's size - it gets really HOT; reason why i overrate my stereo 70's trannies by at least 50% more. having done that, for me the stereo 70 sounds it best at 1.56v bias voltage or 50 ma per tube; set the bias to 1.4v or lower you lose a lot of dynamics (and dynamic-sounding isn't one of the stereo 70's traits to start with). i'd rather listen to a quad of EL-34's on a stereo 70 for one year at it's optimum (50 ma/tube) than spend two years (scrimping on tube replacement cost) with so-so sound...but this is just me
arnoldc wrote:jojo, you're right. the current that you're getting off the cathode is actually the plate + screen current. The screen current, which we can assume that depending on the tube used, will be anywhere from 7mA (as you posted) to 8.8mA (as I posted). no big deal
so we can say that when biasing the ST-70 the screen current was never considered, but plays a factor.
Biasing will always be a problem since depletion of the power tubes will never be equall after they were plugged on the tube sockets. Modifying to independent biasing is a MUST.
vintage_dog wrote:.... my recollection of the st70 being biased "correctly" (below 45ma), is that it looses a bit of dynamics. will try that tonight.
vintage_dog wrote:vintage_dog wrote:.... my recollection of the st70 being biased "correctly" (below 45ma), is that it looses a bit of dynamics. will try that tonight.
i biased my st70 down to about 1.35, and blah, didn't quite like it - slow and lacks dynamics, so it's back to 1.56 as recommended by the designers. luckily, the power transformers have been upgraded but they still get very hot...
hypertriode wrote:m_shoe_maker wrote:Naku po Nataranta na tong ST70 user.
Anyway, simple lang ang solution ko.........
Master Hyper, what reading from my volt meter will I bias my ST70
Simpleng tanong sa Tube God, and his answer will be my Gospel Truth.
just my opinion fritz: i agree with john that NOS EL-34's can take the punishment inflicted by high or bias settings while new production ones can't. also take into account the stock stereo 70 transformer's size - it gets really HOT; reason why i overrate my stereo 70's trannies by at least 50% more. having done that, for me the stereo 70 sounds it best at 1.56v bias voltage or 50 ma per tube; set the bias to 1.4v or lower you lose a lot of dynamics (and dynamic-sounding isn't one of the stereo 70's traits to start with). i'd rather listen to a quad of EL-34's on a stereo 70 for one year at it's optimum (50 ma/tube) than spend two years (scrimping on tube replacement cost) with so-so sound...but this is just me
m_shoe_maker wrote:hypertriode wrote:m_shoe_maker wrote:Naku po Nataranta na tong ST70 user.
Anyway, simple lang ang solution ko.........
Master Hyper, what reading from my volt meter will I bias my ST70
Simpleng tanong sa Tube God, and his answer will be my Gospel Truth.
just my opinion fritz: i agree with john that NOS EL-34's can take the punishment inflicted by high or bias settings while new production ones can't. also take into account the stock stereo 70 transformer's size - it gets really HOT; reason why i overrate my stereo 70's trannies by at least 50% more. having done that, for me the stereo 70 sounds it best at 1.56v bias voltage or 50 ma per tube; set the bias to 1.4v or lower you lose a lot of dynamics (and dynamic-sounding isn't one of the stereo 70's traits to start with). i'd rather listen to a quad of EL-34's on a stereo 70 for one year at it's optimum (50 ma/tube) than spend two years (scrimping on tube replacement cost) with so-so sound...but this is just me
That's it The Master has spoken.
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