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Re: what tube are you using? [message #31655 is a reply to message #31650]

Tue, 20 December 2005 11:21

Damir
Messages: 1005
Registered: May 2009

Illuminati (2nd Degree)

High-gm pentodes (say, D3a, E280F, E810F, EF184, 12BY7...) can be usable for single stage 300B driver with relative small anode load, say 8,2k-15kOhms. A=Ra*gm, and with Ra=10k and say, gm=5mA/V (possible with unbypassed Rk), we have A=50. But, internal anode resistance rp of the pentode is high, much larger then Ra - then our Rout = Ra // rp, and Rout ~ Ra - or 10 kOhms in this example.
We can observe cascode like "quasy-pentode" without g2 current and less noise, but the same "problem" is present - large internal resistance. I tried 5687 tube here, see the "report" down low...

For long time I experimented with various drivers, and best subjective performance/sound would be finally soldered in a nice box... Didn`t decide yet...

P.S. Interesting comparison of various pentodes (and some triodes) can be found here:

http://www.pmillett.com/pentodes.htm

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[Message index]

		Received Grid-Chokes By: Damir on Fri, 16 December 2005 10:51
		sweet... By: PakProtector on Fri, 16 December 2005 15:52
		Re: sweet... By: Damir on Sat, 17 December 2005 08:33
		Re: sweet... By: PakProtector on Sat, 17 December 2005 08:51
		Re: sweet... By: Damir on Sat, 17 December 2005 09:47
		I love an elegant solution…John (nt) By: Forty2wo on Sun, 18 December 2005 17:41
		Re: sweet... By: MQracing on Mon, 19 December 2005 09:10
		Re: sweet... By: Damir on Mon, 19 December 2005 14:15
		Re: sweet... By: MQracing on Mon, 19 December 2005 18:05
		Received the response from AE By: Damir on Wed, 21 December 2005 05:25
		OEM bobbins for AMCC 8 core assembly By: MQracing on Tue, 20 December 2005 06:24
		Re: OEM bobbins for AMCC 8 core assembly By: Damir on Tue, 20 December 2005 07:33
		Re: OEM bobbins for AMCC 8 core assembly By: MQracing on Tue, 20 December 2005 07:53
		Re: sweet... By: MQracing on Mon, 19 December 2005 09:10
		Re: sweet... By: MQracing on Mon, 19 December 2005 09:10
		an alternative design By: MQracing on Tue, 20 December 2005 07:21
		Re: an alternative design By: Damir on Tue, 20 December 2005 07:48
		Re: an alternative design By: MQracing on Tue, 20 December 2005 07:59
		what tube are you using? By: MQracing on Tue, 20 December 2005 08:13
		if I may expand on a theme.... By: MQracing on Tue, 20 December 2005 08:53
		Re: what tube are you using? By: Damir on Tue, 20 December 2005 11:21
		correction of a typo.... By: MQracing on Tue, 20 December 2005 08:22
		Re: an alternative design By: PakProtector on Tue, 20 December 2005 17:43
		core geometries and materials By: MQracing on Wed, 21 December 2005 07:20
		Re: core geometries and materials By: PakProtector on Wed, 21 December 2005 14:32
		Re: core geometries and materials By: PakProtector on Sat, 24 December 2005 18:43
		mounting brackets for AMCC 8 core assembly By: MQracing on Tue, 20 December 2005 06:20

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