300b driver revisited.

[losacco]

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]

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]

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]

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]

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]

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]

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]

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.

 

[ashok]

I have a couple of questions about the driver for the 300B.
The tubelab SE uses a 2SK2700 follower as a driver.
Maybe a silly question , but does this sound as good as a regular tube driver stage ? Like say :
http://www.diyaudio.com/forums/attachment.php?postid=1815592&stamp=1241062742
If the 2Sk2700 is not available can a 2SK2611 be used instead. It has almost three times as much capacitance both at input and output. As a follower I think it should not , but is that a correct assumption ?

Does a SRPP stage at the input have any benefit regarding sound quality ? I'm asking just in case some one has actually tried that.
Thanks.

 

[andyjevans]

Wow - this is an old thread. I can see that in 2010 I would have been using 6SN7s.

Right now I would be using two stages as follows:
Stage 1: Ale Moglia's 01A preamp Gen 2.
01a Preamp (Gen2) | Bartola Valves

Stage 2: 4P1L with Lundahl interstage e.g. LL1671/30mA from K&K Audio
RE: The 4P1L line stage - KevinC - K&K Audio / Lundahl Transformers

I can't think of anything better than this right now. These are complex circuits but the results are pretty stunning.