300b driver revisited.

losacco · 21st July 2010, 05:59 PM

I have built the Walton 300b mono’s with good results. I’m now interested in changing the 300b driver from the 6sn7GB to something else with minimal circuit changes. I have researched past posts and understand this has been talked about a lot. I would need a schematic.

Any new ideas?

kstagger · 21st July 2010, 06:07 PM

pentode - one stage is all you need. C3m, 6BQ5,etc are alternatives to the classic 91A circuit. Look for the Thorsten Loesch 'Legacy' power amp.

transformer coupling

A nice mosfet follower after the 6SN7 would provide plenty of oomph. Tubelab's Powerdrive comes to mind.

kmtang · 21st July 2010, 09:19 PM

I use two stages of 6BX7 to drive the 300B. The plate load is with IXYS45M10 CCS and RC cathode bias. The 1st and 2nd stage is with 0.1uF coupling capacitor.

Johnny

andyjevans · 21st July 2010, 09:25 PM

I doubt whether you'd find a tube much better than a 6SN7 unless you go into directly heated tubes.

As said, the biggest improvement you'd make would be to get a pair of something like Lundahl LL1660/5mA transformers for driver to 300b, and direct couple the first half (input) of the 6SN7 to the second half (driver). That's what I'd do with minimal changes. If you have room you might use a grid choke and/or plate choke for the input stage.

Andy

Bigun · 21st July 2010, 10:31 PM

there seem to be very few dual triodes like the 6SN7, when I looked around for my project I considered separate tubes for each channel:

6DJ8 and 6N1P - higher mu and lower rp than 6SN7

Eli Duttman · 21st July 2010, 11:40 PM

While not necessarily simple, a 6SL7 β follower (see Morgan Jones) into TubeLab's PowerDrive should work out quite nicely. Greater power O/P is available, due to entering mild Class "A2" conditions. A PTFE dielectric cap. (for "maximized" transparency) between the voltage gain block and the MOSFET driver is practical, given the driver's very high I/P impedance.

tomchr · 22nd July 2010, 01:00 AM

I'm driving a 300B using an anode follower with two 6J5's in it. The anode follower is then followed by a source follower (Tubelab PowerDrive).

If you search for my user name and "anode follower" you should be able to find one of my earlier incarnations of that circuit. I'll get around to posting a current schematic eventually...

~Tom

CLS · 22nd July 2010, 01:18 AM

Mine is choke loaded 6S45 direct couple to 300B. Very simple and elegant circuit, but needs a separate (and stacked) power supply for the driver.

Compared to 6S45 spud amp, the sound is very similar, with a sense of - barely noticeable - tiny little bit of light fog.

21st July 2010, 05:59 PM	#1
losacco diyAudio Member Join Date: Dec 2008	300b driver revisited. I have built the Walton 300b mono’s with good results. I’m now interested in changing the 300b driver from the 6sn7GB to something else with minimal circuit changes. I have researched past posts and understand this has been talked about a lot. I would need a schematic. Any new ideas?

21st July 2010, 10:31 PM	#5
Bigun diyAudio Member Join Date: Jan 2009 Location: K-W Ontario Blog Entries: 2	there seem to be very few dual triodes like the 6SN7, when I looked around for my project I considered separate tubes for each channel: 6DJ8 and 6N1P - higher mu and lower rp than 6SN7 __________________ "The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

21st July 2010, 11:40 PM	#6
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	While not necessarily simple, a 6SL7 β follower (see Morgan Jones) into TubeLab's PowerDrive should work out quite nicely. Greater power O/P is available, due to entering mild Class "A2" conditions. A PTFE dielectric cap. (for "maximized" transparency) between the voltage gain block and the MOSFET driver is practical, given the driver's very high I/P impedance. __________________ Eli D.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Has anyone tried a 6S4A as a 300B driver tube?	MIKET	Tubes / Valves	29	11th May 2012 04:58 PM
pentode aikido driver for 300b	dave dove	Tubes / Valves	18	24th March 2012 08:37 PM
Looking for non-DRD 300B using D3a as driver	jmillerdoc	Tubes / Valves	39	14th January 2010 10:40 PM
Low voltage 845SE with 300B driver	Ziggy	Tubes / Valves	6	18th February 2009 05:16 AM
Using 6L6 for 300b driver	papparazzi	Tubes / Valves	6	2nd July 2006 08:03 PM

21st July 2010, 06:07 PM	#2
kstagger diyAudio Member Join Date: Dec 2003 Location: Grand Rapids	pentode - one stage is all you need. C3m, 6BQ5,etc are alternatives to the classic 91A circuit. Look for the Thorsten Loesch 'Legacy' power amp. transformer coupling A nice mosfet follower after the 6SN7 would provide plenty of oomph. Tubelab's Powerdrive comes to mind.

21st July 2010, 09:19 PM	#3
kmtang diyAudio Member Join Date: Nov 2004 Location: Vancouver	I use two stages of 6BX7 to drive the 300B. The plate load is with IXYS45M10 CCS and RC cathode bias. The 1st and 2nd stage is with 0.1uF coupling capacitor. Johnny

21st July 2010, 09:25 PM	#4
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	I doubt whether you'd find a tube much better than a 6SN7 unless you go into directly heated tubes. As said, the biggest improvement you'd make would be to get a pair of something like Lundahl LL1660/5mA transformers for driver to 300b, and direct couple the first half (input) of the 6SN7 to the second half (driver). That's what I'd do with minimal changes. If you have room you might use a grid choke and/or plate choke for the input stage. Andy

22nd July 2010, 01:00 AM	#7
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	I'm driving a 300B using an anode follower with two 6J5's in it. The anode follower is then followed by a source follower (Tubelab PowerDrive). If you search for my user name and "anode follower" you should be able to find one of my earlier incarnations of that circuit. I'll get around to posting a current schematic eventually... ~Tom

22nd July 2010, 01:18 AM	#8
CLS diyAudio Member Join Date: Jun 2005 Location: Taiwan	Mine is choke loaded 6S45 direct couple to 300B. Very simple and elegant circuit, but needs a separate (and stacked) power supply for the driver. Compared to 6S45 spud amp, the sound is very similar, with a sense of - barely noticeable - tiny little bit of light fog.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read