6bl8/ecf80 for gain stages

black_labb · 11-23-2008, 10:28 AM

i got some 6bl8 triode/pentode tubes the other day. seem like great tubes to use when you want a pentode with a triode in there, which is something im pretty interested in. because they were designed originally for tv tuners, the datasheets dont give the details for using the triode or pentode for voltage gain.
i have found a schematic for an amp (playmaster 116, http://ozvalveamps.elands.com/playma...aymast_116.jpg ) that uses the triode as a split load PI, and the pentode section for voltage gain. im not sure if the pentode is wired for higher gain, or wether it is wired for less gain as not as much is neccesary due to its location in the circuit (just before the PI). it's circuit also incorperates the -ve feedback, which would effect the gain.

does anyone know of any other circuits using these tubes for audio? any ideas as to how suitable the values for the pentode section of the playmaster are for the first tube in a design? im thinking that i would assume the triode is a 12au7 triode, as it has similar gain and somewhat similar transconductance. i have little idea as to wether this is a good idea or not. any pentodes that would be pretty similar to the pentode section, or some tips on how to examine datasheets to find out how similar they are. would using a circuit similar to an ef86 be a good startingpoint for modifying?

i have 6 of the tubes, so im happy to do a bit of experementing at the expense of 1 or 2 of them if neccesary, but i think i need a bit of guidance as i've never done much experementing with amps other than coupling cap values and cathode resistors/bypass caps. have to start somewhere though.

edit: heres a datasheet http://www.pmillett.com/tubedata/HB-...art_1/6BL8.PDF

cleantimestream · 02-10-2009, 03:42 AM

Sansui used this tube in their front ends back in the 60's. Google Sansui 500A schematic and you will find a free download. Excellent tube.

black_labb · 02-10-2009, 05:54 AM

Quote:

Originally Posted by cleantimestream

Sansui used this tube in their front ends back in the 60's. Google Sansui 500A schematic and you will find a free download. Excellent tube.

finished the amp and am very happy with the 6bl8, but will deffinately check it out as i plan on using it for my next amp as well. thanks for the tip

11-23-2008, 10:28 AM	#1
black_labb Senior Member Join Date: Apr 2007 Location: sydney australia Posts: 777	6bl8/ecf80 for gain stages i got some 6bl8 triode/pentode tubes the other day. seem like great tubes to use when you want a pentode with a triode in there, which is something im pretty interested in. because they were designed originally for tv tuners, the datasheets dont give the details for using the triode or pentode for voltage gain. i have found a schematic for an amp (playmaster 116, http://ozvalveamps.elands.com/playma...aymast_116.jpg ) that uses the triode as a split load PI, and the pentode section for voltage gain. im not sure if the pentode is wired for higher gain, or wether it is wired for less gain as not as much is neccesary due to its location in the circuit (just before the PI). it's circuit also incorperates the -ve feedback, which would effect the gain. does anyone know of any other circuits using these tubes for audio? any ideas as to how suitable the values for the pentode section of the playmaster are for the first tube in a design? im thinking that i would assume the triode is a 12au7 triode, as it has similar gain and somewhat similar transconductance. i have little idea as to wether this is a good idea or not. any pentodes that would be pretty similar to the pentode section, or some tips on how to examine datasheets to find out how similar they are. would using a circuit similar to an ef86 be a good startingpoint for modifying? i have 6 of the tubes, so im happy to do a bit of experementing at the expense of 1 or 2 of them if neccesary, but i think i need a bit of guidance as i've never done much experementing with amps other than coupling cap values and cathode resistors/bypass caps. have to start somewhere though. edit: heres a datasheet http://www.pmillett.com/tubedata/HB-...art_1/6BL8.PDF

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02-10-2009, 03:42 AM	#2
cleantimestream Junior Member Join Date: Feb 2009 Posts: 2	Sansui used this tube in their front ends back in the 60's. Google Sansui 500A schematic and you will find a free download. Excellent tube.

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