ECC88, warm up time

peranders · 12:22 PM

I'm working on my ECC88 gainclone and there is one thing I wonder about (can't test it right now) and that is the warm up time for a ECC88? How long does it take for the tube to stabilize regarding the working point?

I'm designing a mute circuit for the LM3886. I plan to use a CMOS4541, any better non-exotic reproducable suggestions? I want the delay to be fairly reproduceble and stable over time and temperature with short reset time.

I plan also to have a slow start for the heating. What is a suitable time? 5 seconds?

(This is my very first tube project..... be gentle with me )

Zen Mod · 2nd November 2009, 12:31 PM

15 seconds is more appropriate .

and - because we aren't in any sort of hurry - make that 20

tubes are pretty grateful if you use CCS for heating , and elevate heater PSU potential at least 30V

peranders · 2nd November 2009, 01:25 PM

Do you mean 15 seconds for the tube to stabilize or for the filament current to be stable?

What do you mean 30 V potential? Do you mean that the heater should float 30 V over ground?

Zen Mod · 2nd November 2009, 01:33 PM

say that tube will be completely operational (heated) in 15 secs ;

yup - heater floating 30V over gnd .

peranders · 2nd November 2009, 01:38 PM

Why over ground?

Zen Mod · 2nd November 2009, 02:09 PM

there is sort of diode transfer function (for AC) between heater and cathode .

when you elevate heater above (or bellow ) cathode (which is usually at near gnd potential) you're approaching horizontal part of mentioned diode transfer characteristic .

in that area any possible fluctuation in heating voltage cannot be "rectified"/transfered to cathode

place resistive voltage divider between Ub and gnd , flowing ~1mA ; put good cap across lower resistor , route potential from divider junction to heater PSU .

Allen Wright · 2nd November 2009, 02:12 PM

Because it SOUNDS better - that's why!

Regards, Allen (Vacuum State)

peranders · 2nd November 2009, 02:23 PM

Sure, but I don't mind technical info also

Mr. Wright, do you use this technique also? I have never seen it before.

Zen Mod · 2nd November 2009, 02:26 PM

Quote:

Originally Posted by peranders

.....I have never seen it before.

well , let's say just that you didn't look for it

examples are numerous on net , but explanation is still pretty much buried in old books ( and probably in AW Preamp CookBook)

Allen Wright · 2nd November 2009, 04:40 PM

Per,
I have used this technique (heater lifted circa 30 V above gnd) since the mid 70's when I cloned a Lux C35 preamp - but missed this point. It didn't sound as good until the heater was lifted.

Regards, Allen (Vacuum State)

2nd November 2009, 12:17 PM	#1
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	ECC88, warm up time I'm working on my ECC88 gainclone and there is one thing I wonder about (can't test it right now) and that is the warm up time for a ECC88? How long does it take for the tube to stabilize regarding the working point? I'm designing a mute circuit for the LM3886. I plan to use a CMOS4541, any better non-exotic reproducable suggestions? I want the delay to be fairly reproduceble and stable over time and temperature with short reset time. I plan also to have a slow start for the heating. What is a suitable time? 5 seconds? (This is my very first tube project..... be gentle with me ) __________________ /Per-Anders (my first name) or P-A as my friends call me Last edited by peranders; 2nd November 2009 at 12:22 PM.

2nd November 2009, 12:31 PM	#2
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	15 seconds is more appropriate . and - because we aren't in any sort of hurry - make that 20 tubes are pretty grateful if you use CCS for heating , and elevate heater PSU potential at least 30V __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; BAF Forum & Gallery;I'm dumb

2nd November 2009, 01:25 PM	#3
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Do you mean 15 seconds for the tube to stabilize or for the filament current to be stable? What do you mean 30 V potential? Do you mean that the heater should float 30 V over ground? __________________ /Per-Anders (my first name) or P-A as my friends call me

2nd November 2009, 01:33 PM	#4
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	say that tube will be completely operational (heated) in 15 secs ; yup - heater floating 30V over gnd . __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; BAF Forum & Gallery;I'm dumb

2nd November 2009, 01:38 PM	#5
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Why over ground? __________________ /Per-Anders (my first name) or P-A as my friends call me

2nd November 2009, 02:09 PM	#6
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	there is sort of diode transfer function (for AC) between heater and cathode . when you elevate heater above (or bellow ) cathode (which is usually at near gnd potential) you're approaching horizontal part of mentioned diode transfer characteristic . in that area any possible fluctuation in heating voltage cannot be "rectified"/transfered to cathode place resistive voltage divider between Ub and gnd , flowing ~1mA ; put good cap across lower resistor , route potential from divider junction to heater PSU . __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; BAF Forum & Gallery;I'm dumb

2nd November 2009, 02:12 PM	#7
Allen Wright R.I.P. Join Date: Dec 2001 Location: Schaffhausen Switzerland	Because it SOUNDS better - that's why! Regards, Allen (Vacuum State)

2nd November 2009, 02:23 PM	#8
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Sure, but I don't mind technical info also Mr. Wright, do you use this technique also? I have never seen it before. __________________ /Per-Anders (my first name) or P-A as my friends call me

2nd November 2009, 04:40 PM	#10
Allen Wright R.I.P. Join Date: Dec 2001 Location: Schaffhausen Switzerland	Per, I have used this technique (heater lifted circa 30 V above gnd) since the mid 70's when I cloned a Lux C35 preamp - but missed this point. It didn't sound as good until the heater was lifted. Regards, Allen (Vacuum State)

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