6SL7 and Crossovers

denny9167 · 8th January 2010, 08:58 PM

I have several 6SL7's and was needing an active crossover,I put togther the curcuit below,any suggestions?

SY · 8th January 2010, 09:04 PM

Why use a 6SL7? That's not a good choice for a cathode follower- what you want there is high transconductance and reasonably high current. ECC88, D3a, ECC99, that sort of thing. There are some topological issues, too, but let's get the tube right first.

Geek · 8th January 2010, 10:42 PM

Your "HF" and "LF" labels are reversed.

Cheers!

denny9167 · 9th January 2010, 03:03 AM

Quote:

Originally Posted by Geek

Your "HF" and "LF" labels are reversed.

Cheers!

Your right, thanks for the correction.

ErikdeBest · 9th January 2010, 07:59 AM

The 6SL7 is indeed not appropriate, as the low transconductance implies in 'high' output impedance and... well, read this post that explains it all. Actually the whole thread should be of interest for you!

Allen Wright · 9th January 2010, 10:14 AM

SY is correct about the 6SL7 not being the best tube for the job - but you have a MAJOR mistake in the low pass circuit.

You will only have the grid/cathode V (maybe 2V) across the 40k cathode follower R = microamps of current.

To make it work, even with 6SL7's - you will need to either elevate the grid like you have done in the hipass, or provide a negative supply to feed that 40k.

Regards, Allen

SY · 9th January 2010, 10:17 AM

Those are some of the topological issues. So is the dependence of the filter transfer characteristics on the source impedance.

I'll hold my tongue about using Sallen-Key.

8th January 2010, 09:04 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Why use a 6SL7? That's not a good choice for a cathode follower- what you want there is high transconductance and reasonably high current. ECC88, D3a, ECC99, that sort of thing. There are some topological issues, too, but let's get the tube right first. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

9th January 2010, 07:59 AM	#5
ErikdeBest diyAudio Member Join Date: Mar 2003 Location: Itoculo	The 6SL7 is indeed not appropriate, as the low transconductance implies in 'high' output impedance and... well, read this post that explains it all. Actually the whole thread should be of interest for you! __________________ my surname is indeed 'de Best': neither misspelling nor snobbism! Ask SY!

9th January 2010, 10:17 AM	#7
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Those are some of the topological issues. So is the dependence of the filter transfer characteristics on the source impedance. I'll hold my tongue about using Sallen-Key. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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8th January 2010, 10:42 PM	#3
Geek diyAudio Member Join Date: Sep 2004	Your "HF" and "LF" labels are reversed. Cheers!

9th January 2010, 10:14 AM	#6
Allen Wright R.I.P. Join Date: Dec 2001 Location: Schaffhausen Switzerland	SY is correct about the 6SL7 not being the best tube for the job - but you have a MAJOR mistake in the low pass circuit. You will only have the grid/cathode V (maybe 2V) across the 40k cathode follower R = microamps of current. To make it work, even with 6SL7's - you will need to either elevate the grid like you have done in the hipass, or provide a negative supply to feed that 40k. Regards, Allen

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