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Gents,
So I've read through the forum thus far, and it seems most resort to swapping in diodes to get slightly higher B+ when running 300b tubes.
Anyone decide to bump up the B+ via a different power tranny ? I'd be curious to see how the rest of the amp was delt with (eg - increasing R18 ?).

Thanks,
Steve

You start running into the limits of the single 6SL7 when trying to milk anything more out of the 300B. Google the Angela 300B, for instance. I think I need to make a new board specifically for max 300B performance. With a tweaked power supply and a driver with more swing, we can get around 12W.

Shannon

separks wrote:I think I need to make a new board specifically for max 300B performance.

Sounds good - let me know when the prototype is ready and I'll give it a shot

separks wrote:I think I need to make a new board specifically for max 300B performance.

Shannon

That would be my dream come true Shannon. Ive always wanted you do do a through and through 300B build, with the full output power that tube is capable of. 5U4G and a couple of 6SN7 drivers? Hm hm?

Bob

Hrmm...I think you should go for some sleepers....6EJ7s maybe ? When wired in triode they are pretty nice...Plus they looks cool

separks wrote:You start running into the limits of the single 6SL7 when trying to milk anything more out of the 300B. Google the Angela 300B, for instance. I think I need to make a new board specifically for max 300B performance.

Now that I'd love to see!! I've been dying to try a 300B build. Let us know when it's ready

Shannon; Was your comment on Feb 29th about needing a 300b specific board just a musing or is one in the design phase ? If the latter ,is there a ballpark time for availability ?
If a reality, may I humbly suggest NO 6sn7 and accommodation for choke input power supply.

pdgevas@gmail.com wrote:Shannon; Was your comment on Feb 29th about needing a 300b specific board just a musing or is one in the design phase ? If the latter ,is there a ballpark time for availability ?
If a reality, may I humbly suggest NO 6sn7 and accommodation for choke input power supply.

I really want to do it, but I have another small single ended amp that I'm starting work on and will probably build a new set of Ikes after that. So it's probably third in line.

I admit that I am currently smitten with the Clementine power supply. Is there a choke or topology you had in mind? I'd rather not commit to 10H chokes. I need 5mVrms or less at the B+.

If not the 6SN7, what would one use? The octal pentodes have too much distortion, and need to be adjusted for optimal performance. The 6SN7 can do voltage gain and also drive, and be a tube rollers dream. I can make it 9-pin compatible, I guess, like the Ike Rev B with a dual socket.

One disappointment might be the rectifier, as SS diodes greatly simplify the power supply as they permit using 450V rated caps. But I can stack them in series if I did go the tube rectifier route.

Shannon

separks wrote:...they permit using 450V rated caps. But I can stack them in series...

Just like the Rev A&B diytube ST35 boards. It takes up a fair bit more real estate, but 250V caps are so much easier to source than 500V parts. Or, you can even use stacks of 300V rated caps - good luck finding ones rated 600V. I still love my Rev B, and I think stacked caps are absolutely brilliant.

Thanks for the prompt reply.
I do not profess expertise in audio,and the last time I picked up a soldering iron was 60 years ago, putting kits from Heathkit, Eico ,Hafler and Acrosound together. I have only heard two drivers- the 5842 and the Russian 645p. Of the two I preferred the Raytheon although I understand they can be a pain to maintain. It seems that every " expert" I read looks down their collective noses at the 6sn7. Perhaps this represents snobbery.
As for the choke input , this comes from reading, not audition and I realize that there are price point and market targets that you must address. Plus the hybrid design I was considering ( cioffuli ) uses 10h units so would not apply. If the flexibility for off board options would exist ,that would be great. The same would apply to choke loading stages. As for a specific choke...I have not the faintest idea.
Thanks.

How about two different boards ? One for all the power supplies (B+. Heaters, etc), and another one for the signal. That would allow better mounting of stacked PSU caps, etc.

As far as choke selection goes, one Hammond 159P per channel would work. Its cheap enough.

To SteveH;

That might also allow cascading 159's. Depending on your speakers , I am convinced that the effect of power supply ripple is clearly audible and grossly underestimated. That would reduce it to virtually zero at the supply level. Of course, I do not know what that might do to production costs.

I just wanted to bump this thread and restate my interest in a 300B design

It's definitely on the short list along with a new set of Ikes (with Edcor iron) and a revised ST35. The nice thing with a true 300B amp is that it's pretty similar to the GSG, Clementine and Budgie SE projects which I've tested heavily. I want to start shipping the Budgie SE in August. It'll be a mini Clementine ULtra using a 12AX7 and EL84s.

Shannon

separks wrote:I want to start shipping the Budgie SE in August. It'll be a mini Clementine ULtra using a 12AX7 and EL84s.

This is the first I've heard of it? Do, tell more!