Hoekstra DC-Coupled 300B ... oooooh! - Page 2

Antonio Tucci · 21st July 2004, 05:45 AM

I think that the design by Bob Hoekstra represents one of the most (probably the most) interesting SE design developed in the last years.
My question regard it is the following: Is it possible realize a similar circuit utilizing only two stages (...EC99-300B) ?

serengetiplains · 21st July 2004, 03:33 PM

Hoekstra's direct coupling design can be configured, with a small loss of elegance, for two stages. One need only adjust values to properly bias the tubes, including adding bias circuitry for the ECC99/6L6. To gain a different perspective on this design, you might glance at the following, which is a circuit essentially the same as Hoekstra's except it uses resistor anode loading:

http://www.valvediy.com/simplexpg1.html

A two-stage design would retain the benefits of direct coupling between driver and output, and driver power supply noise cancellation through that coupling method.

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21st July 2004, 05:45 AM	#11
Antonio Tucci diyAudio Member Join Date: May 2002 Location: Lesina (FG) - Italy	I think that the design by Bob Hoekstra represents one of the most (probably the most) interesting SE design developed in the last years. My question regard it is the following: Is it possible realize a similar circuit utilizing only two stages (...EC99-300B) ?

21st July 2004, 03:33 PM	#12
serengetiplains diyAudio Member Join Date: Feb 2004 Location: Canada	Hoekstra's direct coupling design can be configured, with a small loss of elegance, for two stages. One need only adjust values to properly bias the tubes, including adding bias circuitry for the ECC99/6L6. To gain a different perspective on this design, you might glance at the following, which is a circuit essentially the same as Hoekstra's except it uses resistor anode loading: http://www.valvediy.com/simplexpg1.html A two-stage design would retain the benefits of direct coupling between driver and output, and driver power supply noise cancellation through that coupling method.