S11E12 TUBES

h00hbt · 27th February 2011, 12:02 PM

Hi

Anyone have any experience with these tubes? are they drop in replacements for original KT88? Sound?

Cheers

Jaap · 27th February 2011, 04:35 PM

I have tried them shortly in a breadboarded KT66/EL34 type PP amp. They sounded great. I first tried them with fixed bias but they did not like it (kept running away). I believe they need cathode bias because they were designed as pass tubes in regulated supplies.
They are like 12E1 I believe.

richwalters · 27th February 2011, 05:21 PM

Running away. I've always assumed that g1 gets too hot to cause this, effectively re-emitting to cathode, shunting neg volts hence tube is out of control. This doesn't make sense esp the data sheets quote max 100K grid leak for fixed bias and 1M for auto and that agrees well with modern day tubes of the same power. Have to read up on this.

richy

27th February 2011, 12:02 PM	#1
h00hbt diyAudio Member Join Date: Jun 2007	S11E12 TUBES Hi Anyone have any experience with these tubes? are they drop in replacements for original KT88? Sound? Cheers __________________ /H

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27th February 2011, 04:35 PM	#2
Jaap diyAudio Member Join Date: Dec 2002 Location: Netherlands	I have tried them shortly in a breadboarded KT66/EL34 type PP amp. They sounded great. I first tried them with fixed bias but they did not like it (kept running away). I believe they need cathode bias because they were designed as pass tubes in regulated supplies. They are like 12E1 I believe.

27th February 2011, 05:21 PM	#3
richwalters diyAudio Member Join Date: Sep 2003 Location: Alps:Tube amp designs over 150W, SMPS guru.	Running away. I've always assumed that g1 gets too hot to cause this, effectively re-emitting to cathode, shunting neg volts hence tube is out of control. This doesn't make sense esp the data sheets quote max 100K grid leak for fixed bias and 1M for auto and that agrees well with modern day tubes of the same power. Have to read up on this. richy