Bias circuit.what.s the clue?

[catalin gramada]

Maybe bypass it with a quality large polyprop cap but that.s another story...anyhow better decoupling with quality cap may help...

[big_teee]

Found this on the valve wizard site.
http://www.valvewizard.co.uk/bias_supply2.jpg

[R.G.]

Found this on the valve wizard site.

Yeah. Either way works. The resistors are adjusted to keep the control range the same for the output bias voltage. The FW has much less ripple for the same caps, as expected.

Interestingly, you can mess with the circuit a bit and use a capacitor as the series element to drop the raw HT voltage. A 47nF cap in series with the wire to the HT supply and a second diode for DC restoration makes the HW circuit work with that 10uF cap. Capacitive dividers often work well for non-dissipative high voltage dropping.

[jmaf]

If you're competing with China, then using half wave means big savings in millions of units.

But if you're building amplifiers as a hobby, a few units a year, paying U$ 2 more for a full wave rectifier doesn't hurt and gives you twice the power and half the ripple, even if you don't need the power at all it's still a superior bias supply.

[Enzo]

They were half wave rectifying bias supplies long before China became a factor. Ripple just isn't a problem on a bias supply. The current draw is minuscule, the only thing drawing current from a bias supply is its voltage divider itself. We can analyze that FW is "better", but how much better? How much better than zero ripple can we get? Half of zero is still zero.

[jmaf]

They were half wave rectifying bias supplies long before China became a factor. Ripple just isn't a problem on a bias supply. The current draw is minuscule, the only thing drawing current from a bias supply is its voltage divider itself. We can analyze that FW is "better", but how much better? How much better than zero ripple can we get? Half of zero is still zero.

Pedantic much, Enzo?

Before China, Korea was a factor. Before Korea, Japan was a factor.

Where you getting at? Full wave is better than half wave, if you have the U$ 2 use it.

[big_teee]

My PT only has one 50v bias supply tap, used with the CT.
How do you get FW from that?
To get FW, you're back to dropping down the HV taps?
If that is the case, I'll just stick to the HW bias.
http://www.classictone.net/40-18016.pdf
T

[jmaf]

My PT only has one 50v bias supply tap, used with the CT.
How do you get FW from that?
To get FW, you're back to dropping down the HV taps?
If that is the case, I'll just stick to the HW bias.
http://www.classictone.net/40-18016.pdf
T

To rectify a full wave, you need a full wave to begin with

You can't have a full wave with just one tap out of a CT-ground configuration.

That configuration keeps half the transformer unusable in every half cycle, it's a wasteful system carried on from when we didn't have rectifiers priced in pennies.

[big_teee]

So like I said you are back to using the 330v, or using a separate Transformer?
HW bias, is how the existing amp world is fixed?
So much for a two dollar FW Bias!

[jmaf]

So like I said you are back to using the 330v, or using a separate Transformer?
HW bias, is how the existing amp world is fixed?
So much for a two dollar FW Bias!

OP, who started this thread, asked about full wave rectification for bias supplies. My reply is you have a full wave, then it's an additional pennies to a dollar to have 2 more diodes.

If you don't already have a full wave you can rectify, you can't have a full-wave supply. I don't know what else you're going on about, you seem to be jumping on Enzo's train taking issue with sex-of-the-angels.

[big_teee]

Sorry, I was trying to apply this to my own build in progress with practical application, using what I already have.
HW, in my case will have to do.
I will use the HW 50v CT Bias supply.
I will use bigger filter caps.
Don't know where the sex of the angels comment has anything to do with nothing, i thought that was absurd!
I'm done, carry on!
T

[jmaf]

Sorry, I was trying to apply this to my own build in progress with practical application, using what I already have.
HW, in my case will have to do.
Put me down in the camp where HW is good enough.
I will use bigger filter caps.
Don't know where the sex of the angels comment has anything to do with nothing, i thought that was absurd!
I'm done, carry on!
T

You were hijacking a thread to support Enzo's direct reply to my suggestion and previous comment.

Nothing absurd about my reply if you know what "discussing sex of the angels" means. It's about arguing over peanuts, meaningless discussions that miss the main point, losing sight of the forest discussing the trees. Get it? Got it. Carry on.

[big_teee]

My replies had nothing to do with Enzo.
My questions, and comments only had to do with my own build, I stated that.
If you have disagreements with Enzo, take them up with him, not me.
We're done.
Later,
T

[jmaf]

My replies had nothing to do with Enzo.
My questions, and comments only had to do with my own build, I stated that.
If you have disagreements with Enzo, take them up with him, not me.
We're done.
Later,
T

You said this

HW bias, is how the existing amp world is fixed?
So much for a two dollar FW Bias!

So maybe I misunderstood what you were going on about, or maybe not. Either way, it's still a 2 dollar issue I could care less about.

[robrob]

jmaf, you're acting like a d*^k. Ease off on the caffeine.