How do you put a CCS under a diff. pair of DHTs???

andyjevans · 22nd December 2005, 08:34 PM

For some reason I don't remember seeing any schematics for a diff pair of DHTs with a CCS. My balanced line stage already uses a diff pair of 1626 with a Morgan Jones type CCS (as in his book, p.134). So how do I deal with the filaments of a DHT? I've never used DHTs but I need to know so I can try out some 26s in the first instance, then one or two other DHTs. Can somebody talk me through this (schematics very welcome) for:
a) AC filaments
b) DC filaments - probably necessary with a 26

Thanks for your help here! I don't know if this is simple or difficult - never seen it done. Andy

dhaen · 22nd December 2005, 08:47 PM

AC:
Cross-connect the heaters in parallel to cancel hum. Connect CCS to centre tap of FLOATING heater transformer winding.

DC:
Parallel heaters, cross-connected is better to reduce effects of ripple. Connect CCS to negative of FLOATING DC heater supply.

Edit: Added FLOATING to AC case.

dhaen · 22nd December 2005, 08:56 PM

AC:

dhaen · 22nd December 2005, 09:02 PM

DC:

andyjevans · 22nd December 2005, 10:16 PM

Thanks, John, that's very helpful. With the aid of some D cells I might be able to get my 26s up and running to see what they sound like. Andy

Rocky · 24th December 2005, 02:21 AM

You probably know about Gary Pimm, if not google him up. He has some good info on implementing CCS's in various circuits, push-pull included, in his article "CCS's and signal current control".

22nd December 2005, 08:34 PM	#1
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	How do you put a CCS under a diff. pair of DHTs??? For some reason I don't remember seeing any schematics for a diff pair of DHTs with a CCS. My balanced line stage already uses a diff pair of 1626 with a Morgan Jones type CCS (as in his book, p.134). So how do I deal with the filaments of a DHT? I've never used DHTs but I need to know so I can try out some 26s in the first instance, then one or two other DHTs. Can somebody talk me through this (schematics very welcome) for: a) AC filaments b) DC filaments - probably necessary with a 26 Thanks for your help here! I don't know if this is simple or difficult - never seen it done. Andy

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22nd December 2005, 08:47 PM	#2
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	AC: Cross-connect the heaters in parallel to cancel hum. Connect CCS to centre tap of FLOATING heater transformer winding. DC: Parallel heaters, cross-connected is better to reduce effects of ripple. Connect CCS to negative of FLOATING DC heater supply. Edit: Added FLOATING to AC case.

22nd December 2005, 10:16 PM	#5
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	Thanks, John, that's very helpful. With the aid of some D cells I might be able to get my 26s up and running to see what they sound like. Andy

24th December 2005, 02:21 AM	#6
Rocky diyAudio Member Join Date: Apr 2004 Location: Kongsberg/Oslo	You probably know about Gary Pimm, if not google him up. He has some good info on implementing CCS's in various circuits, push-pull included, in his article "CCS's and signal current control".