pros/cons of a 845 VS 211 - diyAudio
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Old 18th June 2007, 05:31 AM   #1
jarthel is offline jarthel  Australia
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Default pros/cons of a 845 VS 211

1 major pro of the 211 is price of NOS tubes vs NOS 845.

also has anyone tried both in the same circuit (I am assuming the circuit has variable bias to accomodate the tube change)? feedback please

Thank you.
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Old 18th June 2007, 07:07 AM   #2
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Overall the 845 is a better tube (my opinion) for several reasons.

1) Potentially more output power given similar parameters.

2) Will work well with a 6K - 10K output transformer, where as the 211 is marginal with a 10K load. The 211 works better with a 15-20K transformer.

3) 845 will give decent output with only 850-900 volts. The 211 likes to see 1100-1200 volts before it "comes alive".

BUT

The 845 needs tons of voltage from a (relatively) low impedence driver for it to do the above benefits.

The 211 is easy (relatively) to drive.

The Russian GM70 is somewhere in between the two, closer to the 845 though.

Personally, I think the 845 sounds better with the 211 sounding a "little thin".

Daniel

By the way, 211 and 845 were tested in the same amp when I used them. My driver put out enough voltage to drive both, but its impedence was a little high. I never got around to adding a cathode follower in between the two, but I know it would sound tons better.
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Old 18th June 2007, 12:57 PM   #3
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I have run both tubes in the same amp at 1100 volts using a 10K OPT. The amp uses a mosfet follower to provide all of the grid current that any output tube can swallow. The 845's are more dynamic and alive than the 211 can ever be. I have tried both new production Chinese and NOS RCA tubes. I never run 211's any more, and switch between NOS RCA's for detailed listening at 75mA and Shuguang when I want to turn up the current for loud rock. I wouldn't consider running NOS tubes at 1100 volts and 100+ mA but the Chinese ones don't seem to mind.

The 845 is a much harder tube to drive requiring several hundred volts of drive voltage. The 845 will run deep into A2 without distortion if your driver can deliver a bunch (100 mA) of grid current. With 1100 volts on the plate you can get 40 watts of power without abusing the specs in A2.
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