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Re: SE 300B Project, Part 13 - The finished amp [message #31924 is a reply to message #31923]

Tue, 11 July 2006 10:08

Damir
Messages: 1005
Registered: May 2009

Illuminati (2nd Degree)

Hey, I tried various resistors "across" the grid choke, from 100k-1Meg. It can help a little to damp RCL resonance, and/or to "kill" RF oscillations problems... Sometimes I thought that I hear not much of the difference, but in the end my conclusion was that it somehow "kills" that 3D "sound" and sounds somehow "flatter" and 2D...huh, too much "audiophile" language...

But, I noticed that the grid choke can be a giant pick-up on the input grid, oscillations and unstable work/sound are possible... You must mount it very close to the 300B socket, at least 1-2cm from the chasis, it`s orientation in respect with other magnetic components (OPT) is important... and check for oscillations. Lower values of parallel resistor "defeat" any benefit of the grid choke, IMO ... your 10k in parallel with high impedance of the choke is 10k...but also in the parallel with unecessary choke winding capacitance. And not just that - this grid resistor of 10k is actually in parallel with triode`s load (anode resistor, or CCS when you use anode out), and this resultant driver load is too low.
In other words, your driver "sees" just the 10k as a load, parallel with Cw... not too good, IMO.
Large input capacitance of EC8010 means that you must be carefull not to use large series resistance (pot) before the tube - HF "roll-off".

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[Message index]

		SE 300B Project, Part 13 - The finished amp By: Damir on Mon, 26 June 2006 12:25
		Re: SE 300B Project, Part 13 - The finished amp By: Wayne Parham on Mon, 26 June 2006 16:03
		Re: SE 300B Project, Part 13 - The finished amp By: Forty2wo on Sun, 02 July 2006 14:57
		Re: SE 300B Project, Part 13 - The finished amp By: Damir on Mon, 03 July 2006 06:08
		Re: SE 300B Project, Part 13 - The finished amp By: Forty2wo on Mon, 03 July 2006 17:01
		Re: SE 300B Project, Part 13 - The finished amp By: duderduderini on Thu, 01 November 2007 07:12
		Re: SE 300B Project, Part 13 - The finished amp By: horny on Sun, 09 July 2006 13:26
		Re: SE 300B Project, Part 13 - The finished amp By: Damir on Mon, 10 July 2006 07:08
		Re: SE 300B Project, Part 13 - The finished amp By: horny on Tue, 11 July 2006 09:23
		Re: SE 300B Project, Part 13 - The finished amp By: Damir on Tue, 11 July 2006 10:08
		Re: SE 300B Project, Part 13 - The finished amp By: horny on Tue, 11 July 2006 10:37
		Re: SE 300B Project, Part 13 - The finished amp By: Damir on Tue, 11 July 2006 11:33
		Re: SE 300B Project, Part 13 - The finished amp By: horny on Fri, 21 July 2006 04:19
		Re: SE 300B Project, Part 13 - The finished amp By: Damir on Fri, 21 July 2006 07:46
		Re: SE 300B Project, Part 13 - The finished amp By: horny on Fri, 21 July 2006 08:38
		Re: SE 300B Project, Part 13 - The finished amp By: Wayne Parham on Fri, 21 July 2006 09:24
		Wow! :-) By: Damir on Fri, 21 July 2006 14:06
		Re: Wow! :-) By: horny on Sat, 22 July 2006 04:56
		Re: Wow! :-) By: Damir on Sun, 23 July 2006 07:14
		Re: Wow! :-) By: horny on Sat, 29 July 2006 03:59
		Re: SE 300B Project, Part 13 - The finished amp By: horny on Sun, 13 August 2006 04:04
		Re: SE 300B Project, Part 13 - The finished amp By: Damir on Sun, 13 August 2006 16:00
		Re: SE 300B Project, Part 13 - The finished amp By: horny on Wed, 16 August 2006 14:43
		Re: SE 300B Project, Part 13 - The finished amp By: Damir on Thu, 17 August 2006 07:45
		Re: SE 300B Project, Part 13 - The finished amp By: red on Wed, 01 August 2007 06:24

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