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In Reply to: RE: 211 optimum bias point... posted by 2395 on July 30, 2015 at 07:41:26
Verify my sim but distortion seems high for 16watts out
Running 211 at 75ma
Follow Ups:
thanks...you simulation is fantastic...please....based upon your sims what would you set the bias at [if your amps] to get the best for general listening........best low distortion against usable power ....
Yes the schematic is drawn by me [from a bad photo of the original schematic] and from the actual [my] amps, I can email you a better graphic if you would like...the amps are based upon an original Kondo san design.
can I respectfully [and appreciating your time] request a copy of the sims for the following
60ma
64ma
68ma
70ma
again...very much appreciated
These are the numbers but let your ears do the testing in the end.
You have a pot to quickly dial it in but be careful not to blow your OPT.
You might want to think about protecting your tube and OPT with this bias scheme.
... very much appreciated….
if these were your amps [I enjoy hi res audio] what would you set the bias at and why………
again…your opinion is very much appreciated….
If these are my amps, I would listened to other people's advise and try listening to them at varying bias point.
I would start from 40mA and listened the amp carefully at varying loudness levels. And I would increase 5mA and repeat the listening session till the bias reaches to 65-70mA. I would never bias the 211 hotter than 70mA or colder than 40mA.
Why would I spend time listening to the amp other than just set a bias point that other people said it's the lowest distortion level for them? It's because the amps we used are different, the circuits are different, the tubes are different and most of all, the OPT and the speakers we use are different. It is no joke when people said there is a real good synergy going between the OPT, the OPT tubes and the speakers in the SET amps.
Not only the bias point is important, you should also listened to your 211 amps with the speakers connected to the different output impedance tabs (4 / 8 /16 ohms) if available.
It depends on your speakers, volume and general listening habits.
I think 70-75ma would be a good starting point but at the end of the day, let your ears make the decision.
I'm not well versed yet with this topology so maybe someone else can chime in and I'll change the sim for you. Seems the second tube may be operating above the ratings of this tube.
Is this your schematic?
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