regulated 5V DC supply

[dhaen]

Is one side of a lightbulb filament dimmer than the other? Is one side of a resistor in series with a load less hot? Stick your finger on it and report back to us.

Joel,
The emission we are talking about is that of electrons. Those are the things we use to make it work!
If we apply a sufficiently negative grid voltage, the emission of electrons falls to zero.
Of course the temperature of the filament remains (relatively) constant along it's length, however it's powered.

 

[Joel]

If we apply a sufficiently negative grid voltage, the emission of electrons falls to zero.

Nope. The plate current falls to zero. The electrons might not get through to the plate, but they are still boiled off the cathode.

 

[dhaen]

The electrons might not get through to the plate, but they are still boiled off the cathode.

Where do they go then?
Is that why some old tubes rattle

When the tube is in cut-off, I was taught that the electrons leap out from the surface of the cathode, and straight back in. Hence no actual emission, and no mass loss.

 

[Joel]

Yes, that's why you shouldn't stare at a tube in cutoff either - too many lost electrons will bombard your eyeballs, which are at ground potential.

 

[dhaen]

too many lost electrons will bombard your eyeballs

Aha, something else we can blame our failing eyesight on

 

[Joel]

Seriously, if you applied a bias voltage to your head, would it repell the radiated electrons from televisions, and monitors???
A 9V batt in your mouth should do it...

 

[dhaen]

Electrons are not radiated. therefore I do not have a problem

If I were in a vacuum, and at a positive potential - I'd be worried

 

[Joel]

If I were in a vacuum, and at a positive potential - I'd be worried

I'd be worried about more than the electrons at that point. hehe

 

[dhaen]

So,
Are we agreed that when powered from DC, more electrons are lost from one end of the filament than the other?

 

[Joel]

So,
Are we agreed that when powered from DC, more electrons are lost from one end of the filament than the other?

I never agreed to that.

Are we agreed that, from a practical point of view - it doesn't make any difference in sound or longevity? If you never experience any problem, what's the point in arguing its causes?

 

[Tomatito]

Oomph. This has all been very educational, and I enjoyed reading it, but I'm just as confused as when I started this post. There seem to be an equal amount of pros and cons so I still don't know what to do and how to do it best.

 

[dhaen]

Are we agreed that, from a practical point of view - it doesn't make any difference in sound or longevity? If you never experience any problem, what's the point in arguing its causes?

Well, I can't hear the difference, but then, I can't hear any effect from pixie dust either.

As far as longevity is concerned, I have insufficient test data.
I've actually powered a pair of VV32's with DC, running at 1/3 of their maximum anode current - so they should last a long time, but I am concerned that it might affect their life. I'm thinking of adding a switch to reverse the polarity occasionaly.

The point of arguing? It gains knowledge, and it's fun

 

[Joel]

There seem to be an equal amount of pros and cons so I still don't know what to do and how to do it best.

I don't see what's so confusing. If you want to use DC, go for it. It's fairly cheap and easy to do, and easy to undo if you think you don't like it.
I use a bridge rectifier, 2 caps, and 2 small value resistors.

 

[dhaen]

Tomatito,

Just noticed your name as active...

Despite Joel's & my bickering, his last advice is good. You have to try the DC.
IMO too, it's best with a bridge rectifier (schottky if possible), 2 caps and 2 resistors (one in + side and one in - side). This arrangement will minimise common mode and differential mode noise.
You may need to re-bias.

Cheers,

 

[Bas Horneman]

Hi John,

Tomatito and I have both bought prints for a voltage reg and current reg.. so the plan was to use both these.... the current reg after the voltage reg...

Personally I was planning to use a common mode filter ...commonly foud as a mains filter... after that...

It seems on paper...one of the best things to do?

What do you think..

Cheers,
Bas

 

[Tomatito]

filter

Bas,

I happen to have two of those lying around, the Conrad mains filter kit. Would whey do ?

cheers

Martin

 

[Bas Horneman]

Hi..depends on how much current they can handle..

I have tried this before on my 6n1p..(600mA)..and so far so good. Don't know how much it really made a difference..because I have never tried it in that amp with out the filter..they were schaffner...

I tried some other one's but somehow they dropped the voltage...so I dropped them..

But definately go and try it.. you can always parallel them to give you a bigger current handling..

Regards,
Bas

 

[Tomatito]

They can handle 4A according to specs, so it should be allright..

 

[Bas Horneman]

Yup...should be great..

 

[dhaen]

Bas,

Tomatito and I have both bought prints for a voltage reg and current reg.. so the plan was to use both these.... the current reg after the voltage reg...

I am sceptical that any sonic improvement will happen. it could introduce more noise.

Personally I was planning to use a common mode filter ...commonly found as a mains filter... after that...

That'll probably get rid if the noise

Sorry to be a killjoy.

Warning: These are my own opinions, and might not conform with the current DIYaudio laws