6e5p WCF headphone amp with no cap! - Page 5

mogliaa · 26th May 2012, 08:57 AM

I wish I had an AVO!. After so much work managed to get my curve tracer working well. It's a challenge though to trace high gm valves, as the bias point tend to drift a bit so need to readjust just before taking the picture with the camera.
Will do some tests with the 6e5p when I get the time
thanks for the help

revintage · 09:06 AM

The risk of getting gridcurrent in a CF is extremely small wrt to the present signalvoltages.
About high Gm tubes you have to let them stabilize for at least 0,5-1 hour. I have an old AVOIII, it works great even with hi-Gm tubes like 6C45 etc.

mogliaa · 27th May 2012, 08:39 AM

Hi Lars,
Indeed, the valve stabilised after 20-30min. I managed to get a model very close to Dmitry's.

http://www.bartola.co.uk/valves/wp-c...iode-model.png

I may have recorded incorrectly the tracer settings as it seems like the grid start voltage was -2V and not 0V....

Here is the model

http://www.bartola.co.uk/valves/wp-c...pice-model.txt

Cheers,
Ale

costis_n · 27th May 2012, 08:51 AM

I was looking at the datasheet of that valve and the lifetime is stated 500 hours ?!?!?!
In that case, maybe the Pa (max) is optimistic. Just a thought.

mogliaa · 27th May 2012, 09:38 AM

Quote:

Originally Posted by costis_n

I was looking at the datasheet of that valve and the lifetime is stated 500 hours ?!?!?!
In that case, maybe the Pa (max) is optimistic. Just a thought.

Indeed. However can't comment on that as haven't used it yet.
Interesting to see that there is a close brother of this valve, the 6e6pe. Longer life one with similar characteristics. It's a bit price though, but may be worth looking at this one as well....

revintage · 29th May 2012, 10:53 AM

Go for 2*E182CC(4*triodes) instead!

TheGimp · 29th May 2012, 04:04 PM

Another thing to remember is that if you are using cathode bias, grid current does not start when the input signal peak is equal to the bias voltage in magnitude.

This is because of the feedback from the cathode resistor. In simple terms, when the input voltage is 1.3V peak and the bias is 1.3V, you induce an additional voltage drop in the cathode resistor of (24mA/V*1.3V)*32) = 0.998V !

Of course this becomes a cat-chasing-its-tail situation since the increased voltage drop reduces the differential due to the input voltage.

DF96 · 29th May 2012, 05:18 PM

The arithmetic in your second sentence is wrong, but your third sentence suggests that you know this.

hoktuna · 29th May 2012, 05:40 PM

I have a stash(20) of 6E5P and i also got Lars old AVO

I guess it it is a good tube,they are all pretty cloes match.
Iwe got at least three quarters of 25 pice.

mogliaa · 29th May 2012, 06:43 PM

Quote:

Originally Posted by revintage

Go for 2*E182CC(4*triodes) instead!

I have 6N6P which are close equivalent to the E182CC I believe? gm is around 15mA/V as well per triode...

26th May 2012, 08:57 AM	#41
mogliaa diyAudio Member Join Date: Dec 2009 Location: London	I wish I had an AVO!. After so much work managed to get my curve tracer working well. It's a challenge though to trace high gm valves, as the bias point tend to drift a bit so need to readjust just before taking the picture with the camera. Will do some tests with the 6e5p when I get the time thanks for the help __________________ "A mistake is always forgivable, rarely excusable and always unacceptable. " (Robert Fripp) http://www.bartola.co.uk/valves/

26th May 2012, 09:01 AM	#42
revintage diyAudio Member Join Date: May 2007	The risk of getting gridcurrent in a CF is extremely small wrt to the present signalvoltages. About high Gm tubes you have to let them stabilize for at least 0,5-1 hour. I have an old AVOIII, it works great even with hi-Gm tubes like 6C45 etc. Last edited by revintage; 26th May 2012 at 09:06 AM.

27th May 2012, 08:39 AM	#43
mogliaa diyAudio Member Join Date: Dec 2009 Location: London	Hi Lars, Indeed, the valve stabilised after 20-30min. I managed to get a model very close to Dmitry's. http://www.bartola.co.uk/valves/wp-c...iode-model.png I may have recorded incorrectly the tracer settings as it seems like the grid start voltage was -2V and not 0V.... Here is the model http://www.bartola.co.uk/valves/wp-c...pice-model.txt Cheers, Ale __________________ "A mistake is always forgivable, rarely excusable and always unacceptable. " (Robert Fripp) http://www.bartola.co.uk/valves/

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27th May 2012, 08:51 AM	#44
costis_n diyAudio Member Join Date: Aug 2008	I was looking at the datasheet of that valve and the lifetime is stated 500 hours ?!?!?! In that case, maybe the Pa (max) is optimistic. Just a thought.

29th May 2012, 10:53 AM	#46
revintage diyAudio Member Join Date: May 2007	Go for 2E182CC(4triodes) instead!

29th May 2012, 04:04 PM	#47
TheGimp diyAudio Member Join Date: Aug 2009 Location: Johnson City, TN	Another thing to remember is that if you are using cathode bias, grid current does not start when the input signal peak is equal to the bias voltage in magnitude. This is because of the feedback from the cathode resistor. In simple terms, when the input voltage is 1.3V peak and the bias is 1.3V, you induce an additional voltage drop in the cathode resistor of (24mA/V1.3V)32) = 0.998V ! Of course this becomes a cat-chasing-its-tail situation since the increased voltage drop reduces the differential due to the input voltage.

29th May 2012, 05:18 PM	#48
DF96 diyAudio Member Join Date: May 2007	The arithmetic in your second sentence is wrong, but your third sentence suggests that you know this.

29th May 2012, 05:40 PM	#49
hoktuna diyAudio Member Join Date: Sep 2004 Location: Eskilstuna	I have a stash(20) of 6E5P and i also got Lars old AVO I guess it it is a good tube,they are all pretty cloes match. Iwe got at least three quarters of 25 pice.

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