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Old 27th August 2003, 02:36 AM   #21
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You can't say something about the sound of an infinite cap because for one, it doesn't exist. Two, it *is* a wire in any practical sense, because no matter how many megamperes of DC you place across the thing, it'll still take infinite time to charge!

Tim
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Old 27th August 2003, 07:48 AM   #22
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Default Splitting hairs...

Tim,

1 I can say what I like about caps (Whether it's right or wrong is a matter of chance).

2 If it takes an infinite time to accept any charge, then it's indistinguishable from a piece of wire...

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Old 27th August 2003, 08:31 AM   #23
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Default ...Split ends???

If it can accept an infinite charge for an infinite amout of time (i.e. a capacitor of infinite capacitance) then it is certainly not a piece of wire! It would have to have zero impedance (or its temperture rises to infinty) and zero inductance too (ditto)

What it is I don't know... not even in theory other than something with infinite capacitance and no other property...

Pretty damm useless - so now the hairs must be fully split

ciao

James

p.s.

John.

I'll get your D3 email done this week - things have been frantic over the summer... easing up a bit now...
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Old 27th August 2003, 10:08 AM   #24
dhaen is offline dhaen  Europe
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Default Re: ...Split ends???

Quote:
Originally posted by James D.
I'll get your D3 email done this week - things have been frantic over the summer... easing up a bit now... [/B]
Aha, back from the pool?

Cheers

John
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Old 27th August 2003, 11:05 AM   #25
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Quote:
Aha, back from the pool?
Yeah... I kept tripping over the nubile beauties my son brought back from University for the summer
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Old 27th August 2003, 02:54 PM   #26
dhaen is offline dhaen  Europe
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Quote:
Originally posted by James D.


Yeah... I kept tripping over the nubile beauties my son brought back from University for the summer
It's a hard life..
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Old 28th August 2003, 08:25 PM   #27
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> The turn on surges can be lessened by using tube rectifiers and ...they're so much easier on components, aren't they?

I am probably going to be evicted for this opinion.....

Tube rectifiers suck.

They waste a LOT of power. They give off a lot of heat. They use a lot of space. They complicate the wiring. They can't (easily) be used in some rectifier configurations. They ruin regulation.

And they do not reduce turn-on surge. The direct-heat rectifiers turn-on in 2 seconds, your heater-cathode tubes need 10 seconds to turn-on, so there is still a long period when B+ is very high. Much higher than if you used sand-state rectifiers and adjusted transformer voltage to give the same final loaded B+, because the tubes need 50-150 volts extra transformer to cover losses under load and there is no load until the heater-cathode tubes warm up.

Yes, sand-state rectifiers smack the capacitors awful hard. But caps have improved SO much since 1938 that it isn't an issue.

> So, now you know why grandma's radio lasted forever...

Grandma's radio did NOT "last forever". Radio repair was big business, and most radios needed repair every year or two. My father made money in high school that way. Yes, there are 1930s radios still working fine, but many-many-many more were scrapped over the years because they were too much trouble to keep-up.

And don't get me started on Tube TVs. On one hand, they were good for the industry because the high parts-count forced improvements in all parts. Parts got much better through the 1950s. On the other hand, at their best they crapped-out every year or two. There were tube-testers in every drugstore, that's how big a problem it was.

> no excuse why your tube amp shouldn't last forever...

Correct. With modern parts and worst-case design, DIY tube gear should last a VERY long time. Your labor is worth more than the few bucks extra needed to use over-rated parts (2W instead of 1W, 600V instead of 400V).
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Old 28th August 2003, 09:26 PM   #28
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Hi,

Quote:
Tube rectifiers suck.
Economically, yes. Sonically I don't think so.

Quote:
And they do not reduce turn-on surge.
They could if we pick the right ones and 2 to 10 secs. is still easier on the tubes and caps than full blast at switch-on from silicon diodes.

Quote:
But caps have improved SO much since 1938 that it isn't an issue.
Only time will tell.

Quote:
Grandma's radio did NOT "last forever".
Not our experience in Europe, they only part that would almost certainly die was the filter cap unless it was a PIO....
Not common for radios I admit.

From experience, not just my own, most tubes tend to age extremely slow in radios.
They quite often test "as new" when pulled. Surprising but true.

Mind you I don't use any tube rectifier in my gear using Schottky diodes instead.

For as far as I'm concerned these to are getting better every year.
We just see the SiliconCarbide HT Schottkys hit the market now but for the current asking price you can pick up a lot of damper diodes that do come up slowly and are much more efficient than a regular tube rectifier.

Quote:
Correct. With modern parts and worst-case design, DIY tube gear should last a VERY long time.
Good to see we agree although this is definetely NOT the case of most high-end gear I came across...guess they to have to make a living doing repairs.

Repairs that are often SS related problems though, regs blowing, causing tubes to go south etc. Not pretty.

With a little careful design you can make most tube ams last a lifetime with nothing more than a set of output tubes to relace every two to three years.

Cheers,
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Old 28th August 2003, 10:58 PM   #29
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Quote:
Originally posted by fdegrove
Not our experience in Europe, they only part that would almost certainly die was the filter cap unless it was a PIO....
Not common for radios I admit.
My experience with paper caps is they always, ALWAYS go south and leaky in old radios. I doubt one large enough to filter a half wave would ever be used, it would be absolutely enormous and also cost several x $10 (and I mean in those days' money)!

I'm with PRR on this, they were very cost-driven in those days, and accordingly, repair was big business.

Tim
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Old 28th August 2003, 11:12 PM   #30
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Default TOO YOUNG TO DIE TOO OLD TO ROCK'N ROLL

Hi,

Quote:
My experience with paper caps is they always, ALWAYS go south and leaky in old radios.
Papercaps, yes...PIO caps are not the same.

I'm with PRR on this, they were very cost-driven in those days, and accordingly, repair was big business.

Not so in Europe where you'll find marvellous pieces of engineering just prior to WW2 and for 10 to 15 years after that.

Note that I don't want to start WW3 here, just note in your little book of history that in those days quality came first.

Cheers,
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