I'd like to thank all the people who have sent me good wishes the last year , its been very appreciated .
My lastest scans have shown the cancer is stable , and while I have mostly good days , its nice to hear from such nice people on the other days.
It's also been very humbling to hear how so many people are enjoying the Supratek products. I've had messages from across the globe, from New Zealand to Russia , from people who say the Suprateks have enriched their audio lives , and take great pride in owning a Supratek.
One recent conversation was with a chap who has owned his Supratek since 2007 and is just now replacing a set of tubes - that's pretty good going in 20 years.
He says he's tried many preamps costing many multiples the price and yet to find something as enjoyable.
That's a common theme- long term ownership that continues to deliver enjoyment from music.
You can tell I'm quite proud , but it's also been an honour to be able to do this for so long , and to meet so many good people along the way.
I've just started another preamp build , and while its a long process now , I hope I can make a few more people owners of Supratek preamps.
While I'm still enjoying the Lii Audio F-15/JBL2226/Raal 20-70XR ribbon OB speakers, I did have to spend a fair bit of time finding an amplifier to suit the Lii Audio F-15 driver.
This is what I finally decided on: a 6B4G Single Ended, with options to use the AVVT 302B tube.
The 6B4G tube is not the typical double plate usually used in SE amps, but the Sovtek single plate that was available back in 1990, or even earlier.
It's not a true 6B4G, it has a much bigger plate structure , possibly the 300B Sovtek plate.
It has a plate dissapation of 40 watts, much more then the double plate 15 watt maximum.
It can take a plate voltage of over 400 volts, and current of 100ma (not at the same time!)
It has a clear, slightly warm tone , but without the tubby , somewhat congested tone that 300B tubes can suffer from.
The driver tube is also Russian, the 6E6P , a high transconductance, high gain tube in triode connection.
I like the single driver configuration when using a preamp, just have to be sure the driver tube can swing enough voltage to get full power from the output tube.
I've also set up this amp so it can use a pair of veteran AVVT 302B tubes. These are "super" 300B tubes, capable of much higher voltage and current than normal 300B tubes
Also higher power, and a cleaner, more engaging sound than typical 300B tubes, which frankly I find quite boring. ( I sold a big stash of original WE300B tubes about 30 years ago - no regrets)
To use both 6B4G and 302B I had to install a switch to change filament voltage, and adjustable fixed bias supply to suit either tubes bias requirements.
The bias supply is regulated with octal gas regulators- 75 volt OA2 for the 6B4G and 105 volt OA3 for the 302B. A simple pull and insert , adjust bias and a different amplifier!
As the 6B4G is an octal tube and the 302B is a 4 pin, I had to make a 4 pin to octal adaptor to use the 6B4G in the amp.
The driver tube has its own shunt regulater , using 6L6 tubes.
I like regulated power supplies - they dont have the warm tubby sound of ancient tube designs you see everywhere these days , but a solid, detailed, yet natural tone that has significant depth and width .
The Lii Audio F-15 is a very fussy driver that needs a very good, very capable amp.
LATER:
After a couple of months of fine tuning and some minor design changes I settled on using the AVVT 302B tube exclusively in this amp.
The extra power is handy, producing about 1.5 times the power of a 300B , but it is better tube for the sound I want from the F-15. The 302B also lasts forever as it is just idling in this design.
