Re: For Kurt or ? input tube bias?

Posted by Paul Joppa on March 28, 2001 at 23:13:47

In Reply to: Re: For Kurt or ? input tube bias? posted by stevebrown on March 27, 2001 at 19:18:43:

You are running the 6N1P very low and hot, which limits the output voltage it can produce, especially if you have a resistor load. To get more out of it, first raise the plate voltage to 250v, the rated maximum. Then reduce the current, as low as 5mA is reasonable. Then the bias will be nearly 5v (i.e. a 1k cathode resistor) and you will have plenty of output available, like +/-140v peak with a 28k plate load resistor and a 395v B+. For a further increase in available output voltage, use a choke or current source load on the driver; you should get about +/-170v peak.

All the above numbers were derived from the published curves by drawing plate load lines. In spite of the specs, the curves indicate a plate resistance of 10k ohms at 5mA current, and an "operating impedance" (plate voltage/current) of 5 times plate resistance is common for power amplifier stages. Lower ratios are often used for small signal RF amplifiers to maximize transconductance and hence minimize noise, but those considerations are not really important here. The other reason to run low and hot is low distortion, but I can argue that is a red herring if the tube is reasonably linear as the 6N1P is. The argument is long so I won't post it here...

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Follow Ups Full Thread

Topic - For Kurt or ? input tube bias? - SteveBrown 11:30:17 03/27/01 (14)

Re: For Kurt or ? input tube bias? - SteveBrown 18:19:34 03/27/01 (10)

Re: For Kurt or ? input tube bias? - Sacreficialanode 08:12:53 03/28/01 (0)

Re: For Kurt or ? input tube bias? - Kurt Strain 19:12:12 03/27/01 (8)

Re: For Kurt or ? input tube bias? - stevebrown 19:18:43 03/27/01 (7)

Re: For Kurt or ? input tube bias? - Paul Joppa 03/28/0123:13:47 03/28/01 (3)

Re: For Kurt or ? input tube bias? - SteveBrown 11:13:43 03/29/01 (2)

Re: For Kurt or ? input tube bias? - Roscoe Primrose 13:46:24 03/29/01 (1)

Re: For Kurt or ? input tube bias? - SteveBrown 15:17:50 03/29/01 (0)

Re: For Kurt or ? input tube bias? - Kurt Strain 21:30:18 03/27/01 (1)

Re: For Kurt or ? input tube bias? - Kurt Strain 21:32:09 03/27/01 (0)

With two stages (nt) - Roscoe Primrose 20:56:35 03/27/01 (0)

Re: For Kurt or ? input tube bias? - Kurt Strain 14:16:01 03/27/01 (2)

Re: For Kurt or ? input tube bias? - dave slagle 16:33:30 03/27/01 (1)

That's true. Good point. nt - Kurt Strain 19:14:53 03/27/01 (0)

Follow Ups

Re: For Kurt or ? input tube bias? - Paul Joppa 03/28/0123:13:47 03/28/01 (3)

Re: For Kurt or ? input tube bias? - SteveBrown 11:13:43 03/29/01 (2)

Re: For Kurt or ? input tube bias? - Roscoe Primrose 13:46:24 03/29/01 (1)

Re: For Kurt or ? input tube bias? - SteveBrown 15:17:50 03/29/01 (0)

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