Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

Re: Screen resistor tests

2/24/2004 10:44 AM
Chris ( CMW amps )
Re: Screen resistor tests
Hi Dan  
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
Greg Simon

Or what about adding a shared screen resistor ala Hiwatt? Would that help matters any?  
3/2/2004 7:54 PM
Ian Anderson

Selmer also used shared screen resistors - a big 1k5 wirewound thing in the 50w T&B heads  
... Ian :)
2/25/2004 5:44 PM
Jack Koochin
Re: Screen Resistors
Hi Chris,  
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 )

Hi Jack  
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

Hi guys  
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.  
<<First Page<Prev Page 3 of 3