ecc88 arcing at shutdown problem... - Page 4

Arnulf · 2nd December 2009, 08:22 PM

If what you're saying about ECC81s is true then you will measure 7 mA with -20V on the grid and 375V on the anode. Not that there is anything wrong with that either, it's just odd that tubes would differ from specifications so much.

Lower Ra and Rk if that bothers you to much.

pauldune · 2nd December 2009, 08:32 PM

I'm keeping the ECC88 version, so I dont have that problem anymore. It sounds great, and it looks like the arcing problem is history too. Thanks to all of you guys!!!

pauldune · 3rd December 2009, 09:56 PM

I wanted to end this thread with the announcement that the arcing problem is definately gone. 1 little diode between grid and cathode did the trick! So if anybody feels an unstoppable urge to build a dc-coupled concertina with a ccs, this should do the trick.
I'm thinking about opening a new thread, with all the measurements including distortion and spectrumanalyzer shots in every stage of the amplifier, in a "ecc81" vs. "ecc88 ccs loaded" style.
But I dont know if anybody would be interested.... If anybody reads this, and is interested, leave a message here, and I will make the thread...

Gordy · 4th December 2009, 05:21 AM

I am pleased that you have a solution by way of the diode.

By all means start your new thread, as I am sure many people would be very interested.

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2nd December 2009, 08:22 PM	#31
Arnulf diyAudio Member Join Date: Feb 2009	If what you're saying about ECC81s is true then you will measure 7 mA with -20V on the grid and 375V on the anode. Not that there is anything wrong with that either, it's just odd that tubes would differ from specifications so much. Lower Ra and Rk if that bothers you to much.

2nd December 2009, 08:32 PM	#32
pauldune diyAudio Member Join Date: Oct 2009 Location: Netherlands	I'm keeping the ECC88 version, so I dont have that problem anymore. It sounds great, and it looks like the arcing problem is history too. Thanks to all of you guys!!!

3rd December 2009, 09:56 PM	#33
pauldune diyAudio Member Join Date: Oct 2009 Location: Netherlands	I wanted to end this thread with the announcement that the arcing problem is definately gone. 1 little diode between grid and cathode did the trick! So if anybody feels an unstoppable urge to build a dc-coupled concertina with a ccs, this should do the trick. I'm thinking about opening a new thread, with all the measurements including distortion and spectrumanalyzer shots in every stage of the amplifier, in a "ecc81" vs. "ecc88 ccs loaded" style. But I dont know if anybody would be interested.... If anybody reads this, and is interested, leave a message here, and I will make the thread...

4th December 2009, 05:21 AM	#34
Gordy diyAudio Member Join Date: Nov 2006	I am pleased that you have a solution by way of the diode. By all means start your new thread, as I am sure many people would be very interested.