Ordered a Willsenton R300

Hi, Don Sachs here.   First, this is not an attempt at advertising in any way.  The amp whitestix refers to is now in the second prototype and there is no commercial product.   

If you see a 300b that uses a 6SN7 to drive the 300b it will sound ok, but you will never hear what a 300b can do because a 6SN7 tube cannot adequately drive a 300b.   Search the web for Lynn Olson's symmetric Reichert.   What we have done is to start with that sort of design and then completely update the driver section and the power supplies.  The driver is now a triode connected 6V6 for each 300b and it will be coupled with custom wound interstage transformers from Dave G at Cinemag.   I tried a version with CCS loading and it was the best amp I had ever heard.   I have tweaked that further with choke loading and it is better and the IT version will be the best.  There are lots of other tricks in there, and many little secrets, but it is basically 4 single ended 300b amps in one box.  Phase split is done up front with a super high quality input transformer.   The result is an amp that has all the transparency of the flea watt SETs and the drive of a push pull.  It is about 27 watts/ch in this form and sounds like 60 watts/ch.  I love the Kootenay amp, but it doesn't sound like this amp.....  to my ear it is the best amp I have ever heard.

@donsachs

but it is basically 4 single ended 300b amps in one box.

So is this a PSET rather than a push pull circuit?
My 300b SET uses the 6EM7 as the driver rather than the 6SN7 (For the reasons you mentioned). Also it utilizes an interstage transformer in place of coupling capacitors.

I have no doubt that your 300b amplifier will be a fantastic product. Best wishes to you. The 300b properly implemented is superb sounding.

Charles

@whitestix I'll give your Kootenay a good home if it ever comes up for adoption 🙂 do you use a Sachs preamp with it?

Hi

It is a push pull amp comprised of 4 individual SETs, 2 per channel.   Class A, zero feedback of any sort.   There are a couple of little tricks beside that, but that is the basic topology.  The OPTs combine the two out of phase halves of each channel.  Trust me it works beautifully.   I am not done tweaking.  The next iteration will have the custom ITs and be mono blocks because I can then fit more power supply tweaks in the boxes.  But the current one is the best amp I have heard to date anywhere.  Semi-retirement is fun:)

@donsachs

Thanks for the additional clarification. Push-pull topology, that explains the 27 watt power output from the 300b (4 of them). Zero negative feedback is a purist approach and I mean this in a very positive manner. Sounds like you and the esteemed Lynn Olson are developing something quite special.

Charles