Can a grid choke be used with a high rp driver?

RE: Can a grid choke be used with a high rp driver?, posted on April 25, 2015 at 17:08:49
mqracing Manufacturer Posts: 4323 Joined: June 29, 2000	what size grid resistor would it be replacing. then do a quickie calculation of the inductive reactance. compare the two. The larger hurdle with the high impedance driver is getting the plate choke's L where you want it. That is, unless your using a CCS or a plate resistor. MSL Builder of MagneQuest & Peerless transformers since 1989

RE: Can a grid choke be used with a high rp driver?, posted on April 25, 2015 at 18:29:15
Tre' Industry Professional Posts: 17297 Location: So. Cal. Joined: February 9, 2002	Take a look at the winding capacitance as well. With a higher impedance driver stage the shunt capacitance might cause HF loss. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

RE: Can a grid choke be used with a high rp driver?, posted on April 25, 2015 at 19:14:22
Iczerman Audiophile Posts: 147 Joined: July 23, 2000	The grid resistor would be 270K coupling cap .1uf. The inductive reactance for that silk 6000H at 5HZ is 188k ohms. So..it's my assumption that that plate resistor would have to be around 188K also?

?, posted on April 25, 2015 at 20:03:43

Tre'
Industry Professional

Posts: 17297
Location: So. Cal.
Joined: February 9, 2002

Triodes normally want to see a load impedance at least three times their plate resistance to keep the gain up and the harmonic distortion down.

The value of the plate resistor in parallel with the reactance of the choke gives the load impedance the tube see at that frequency.

In the mid-band the reactance of the grid choke will be very high.

The value of the plate resistor is in parallel with the plate resistance to give the output impedance of the stage.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

Thanks!, posted on April 25, 2015 at 21:57:40
Iczerman Audiophile Posts: 147 Joined: July 23, 2000	Did the calculation at 100hz and the reactance was over 3 meg. No worries then! Thanks again!

RE: Can a grid choke be used with a high rp driver?, posted on April 27, 2015 at 03:04:29
Al Noakes	That grid choke will be in parallel with the miller and Cin of the 2A3 . You need to use a much lower Ra valve to get the best results Al

RE: Can a grid choke be used with a high rp driver?, posted on April 30, 2015 at 00:08:43
Cleantimestream Audiophile Posts: 7551 Location: Kentucky Joined: June 30, 2005	Correct... the 417A comes to mind.... wish One could find an Octal with those parameters. The Mind has No Firewall~ U.S. Army War College.

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