|
DIY HiFi Forum Welcome! Need support, you got it. Or share your ideas and experiences. |
For Sale Ads |
Use this form to submit comments directly to the Asylum moderators for this forum. We're particularly interested in truly outstanding posts that might be added to our FAQs.You may also use this form to provide feedback or to call attention to messages that may be in violation of our content rules.
Original Message
RE: Hello 'T', off topic...
Posted by Thorsten on June 5, 2013 at 10:57:10:
Hi,
My "favourite" 300B is as follows:
TJ 300B Mesh Plate
350V/60mA Operating point (means around 1.2K cathode R for self bias)
5-6K Load impedance (mismatch the transformer - treat 4R output as 8R)
This overall reduces output power (you get around 7 Watt) and moves the sound into the direction of the 45.
Add a D3a as driver stage (Resistor Load 22K is ok, CCS or Choke more better; bias - choose your poison aim for 170V/10mA appx.)
Sadly consistency at TJ has been slipping, so only buy them local, tested and selected by the seller and with a decent warranty.
If you want traditional WE Style Sound keep the 350V/80mA/2.5...3K and get either WE Replicas or Svetlana's. Sadly my experiences with the Svetlana's in terms of longevity has not been great, so see above for sourcing.
There are a lot new "brands" and "models" of 300B out there, which to me look all like Shugang/Guagang/Sovtek/Svetlana fayre on the inside (or rebranded TJ), gussied up and sold at obscene markups. So I never tried them...
I did like the Vaic/EML tubes I tried, however there are issues with supply/consistency/warranty, so only buy local with solid warranty.
As an aside, if you can live with low power, I quite like the recently introduced Shugang/Guagang 2A3B (single Anode) which is one of the few 2A3 I actually like. Sticking them into a Billie suitably modified (I like the old DC coupled JC Morrison design from the Fi Primer with 6SL7 SRPP driver) makes a very nice and inexpensive Amp.