[Lost81]

Hi gents,

My listening habit is such that I usually listen in 6 hour sessions every 48 hours.

Now, my question is, regarding the TLP Nirvana and the 4 AKSA 100W N: is it better to leave them perpetually turned on, or is it better for me to turn it off and on once every 42 hours?

How long does the tube last if the pre-amp is left on indefinitely?

I guess the GK-1 folks might want to know if the answer applies to them as well.


Many thanks,
-Lost81

[AKSA]

Benny,

I'd turn if off after a listening session;  six hours is a long time, it takes about half an hour for the tube to deliver its best, so it all seems reasonable.

A 6ES8 will last about 5 years switched on all the time.  If you turn it on for six hours out of every 48 you'd probably get about ten years out of it.  The issue revolves around plate/cathode versus filament life;  turning it off preserves the plate/cathode, but turning it on rips up the filament.  The best compromise is probably to turn it on and off on demand, and run the filament through a smallish resistor to reduce current inrush at cold switch on, which is normally around ten times hot current, and which causes considerable erosion of the filament.  A dropper resistor of say 5R for a 365mA filament like the 6ES8 will drop about 1.8 volts;  so you need an 8.1 Vac supply, but the reduction of inrush current to 1.2A rather than 3.6A is very beneficial to filament life.

cheers,

Hugh

[jules]

message retracted ... thanks for the complete reply Hugh

[Lost81]

Thanks, Hugh!

I am assuming this dropper resistor is for the heater filament (i.e. AC).


Cheers,
-Lost81

[kyrill]

may I ask as a total naive tube builder where on the schematic do I place this "dropper"resistor?

[AKSA]

Hi Kyrill,

The dropper resistor is placed in series with either one of the two wires leading to the filament.

However, to exploit the idea you need a 8.1Vac filament voltage on the transformer.  The GK1 does NOT have this voltage;  it uses 6.3VA, so it cannot be done with the GK1 unless a separate transformer of prescribed 8.1Vac winding is fitted.

Cheers,

Hugh

[kyrill]

So if not 8.1, Hugh you must have your good  reason to opt for 6.3V ?
And because 8.1 is obviously much more than 6.3 is the dropper R just as wishable in the case of 6.3 as for the 8.1 v? Or do I compare apples w. oranges?

Wrong questions. I suppose now that the 8.1 is necessary to compensate for the loss caused by the dropper.

[AKSA]

Hi Kyrill,

Since the dropper inevitably costs some voltage, you do need a higher voltage than the 6.3V standard AC voltage used.  I chose to use the standard voltage because it has worked for about 80 years of tube technology with few problems, AND I know that the dropper resistor dissipates a lot of heat which, from past experience, can sometimes melt the solder joints on the dropper resistor.

You basically need to use a minimum 3W resistor;  these are bulky, and room on the GK1 board was scarce, though it could be mounted on the transformer.  In the finish, after a lot of thought, I decided to run a stock 6.3Vac filament regime.

Looking back, it works well, and I have no regrets........

Cheers,

Hugh

[Lost81]

Hi Hugh,

Regarding those who own the TLP & AKSA or GK-1 & AKSA combinations, is it safe to leave the AKSAs on indefinitely and turn the TLP / GK-1 on and off (to maximize tube life)?

Let me rephrase the questions:

Is it safe to turn ON the pre-amplifier with the amplifiers already turned on?

Is it safe to turn OFF the pre-amplifier with the amplifiers already turned on?

(Since the amplifiers are going to be perpetually turned on, these operating scenarios will be expected).

The reason I'm asking these questions is because I have been taught to turn on my equipment in the following order (and turn them off in the proper reverse order):
1.) Source
2.) Pre-amplifier (wait 5 minutes for tube to warm up)
3.) Amplifiers

The practice described above clearly contravenes it.

Many thanks!


-Lost81

[AKSA]

Benny,

Yes, no problem, you can turn on the source or preamp while the amp is on without too much problem.  There is a small click, but it's not significant and not damaging in any way.

The output of the GK1 is capacitively coupled to the amplifier via a 1uF Auricap.  At switch on, the tube is cold, and no current is flowing through it.  Consequently, at the instant of switchon, the voltage across the Auricap is 0V;  as the filament warms, current flows from plate to cathode and through the cathode resistor, whose voltage then begins to rise to about 48V.  This voltage rise starts at about 6 seconds, and is finished by about 12 seconds, with most of the rise occuring in the last three seconds.  This rise of 16V per second is not so great that it causes problems for the power amplifier, so the answer to your question is that it's quite OK to leave the AKSA power amplifier on and switch the preamp on and off on demand.  You will hear a click, but it's not damaging, and very quiet.

Cheers,

Hugh

[Lost81]

That's great to hear!

Thanks, Hugh!


Cheers,
-Lost81