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|2/24/2004 10:44 AM|
|Chris ( CMW amps )
||Re: Screen resistor tests|
I think it's a good idea , also in general to hear and feel what part-changes do .
but ( ha ha ) I think there's a difference between ( lower voltage ) SE amps and ( higher ) voltage PP amps .
no offense ! , kindest regards ,
|2/25/2004 3:51 AM|
OK, on this subject, here is a question: if you decrease the screen resistance, and are running (for example) a fixed-adjustable bias push-pull 6V6 amp, such as I use, would you want to lower the plate idle dissapation a tad over where would normally be deemed acceptable (about 70%, in my case). And, having brought this up, would you want to use a smaller filter cap value on the screens so that their voltage will sag quickly if drawn upon (heavy distortion at high volume levels)?
|2/25/2004 5:38 PM|
Or what about adding a shared screen resistor ala Hiwatt? Would that help matters any?
|3/2/2004 7:54 PM|
Selmer also used shared screen resistors - a big 1k5 wirewound thing in the 50w T&B heads
|2/25/2004 5:44 PM|
||Re: Screen Resistors|
Just curious..... did you use a wirewound 1K screen R for your 6L6 test on the Bandmaster? Have you tried a non-inductive type, like metal oxide, for example...?
|2/25/2004 6:07 PM|
|Chris ( CMW amps )
I only do use wirewound ones for the G2 duties , never tried non inductive ones ..... another option to test
|3/2/2004 2:45 PM|
As Kevin O'Connor points out in TUT3 if you go with higher value screen resistors you have to make some adjustments in the pre-amp to accomodate the change, its not as simple as just changing the screen resistor values.
I have gone for 2k2 in my amps because I run 6V6, 6l6, el34 all at 420v B+ so I felt I needed some better protection for the 6v6's, to make up for the higher value screen resistors I decreased the size of the cathode bypass caps in the pre amp and got the sparkle back. Whilst I may try 1K in the future I have to say I haven't found the 2k2 value too sterile.
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