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DCR requirments for Chokes
DCR requirments for Chokes
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Old 17th August 2019, 06:50 AM   #31
sumotan is offline sumotan  Indonesia
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Thanks again Guys, another question pls RCLCLC vs LCLCRC are there pros & cons? A tube guy once told me it's better to go RCLC then CLC, think he said something about more stable load for the tube rectifier.
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Old 17th August 2019, 07:43 AM   #32
Keit is offline Keit  Australia
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Only add resistors if you need to because of tube rectifier ratings.

Back in the tube era, you could not get large enough electrolytics to get the ripple low enough. That forced designers to use at least one choke and sometimes two. These days, you can get big electros, so you can just use a big electro and not have a choke at all. A tube rectifier will not cope with that, but you can use silicon diodes which will.

BUT, tbe current in a simple scheme of solid state diodes and a big electrolytic will have very high peak currents, and with the carrier storage in the diodes, may generate noise which gets into the signal path of the amp, and even other devices in you house.

A tube rectifier and a choke-based ripple filter is a very quiet system noise-wise. And it's good at blocking noise from other sources coming down your mains wiring. There are easy ways to fix this in a solid-state + cap power supply though.

Because a choke lets you avoid high peak currents, there is less volt drop in transformer windings. So regulation is better, and there's less thermal stress on the transformer, so it can be a little bit smaller.

All tube rectifiers are rated for the maximum size first filter cap they can tolerate, and the minimum plate-to-plate resistance (the transformer secondary resistance) they can tolerate. Go outside these ratings and the tube will arc over internally, with spectacular (and possibly expensive) results.

If, in a given application, you will go outside the tube ratings for min resistance and/or max filter capacitance, you can fix that by adding resistance. Only add resistance for that reason. You don't need it for anything else. Resistance worsens regulation and makes negligible effect on ripple suppression when a choke is used. (Different story of there is no choke)

Your friend who was taking about resistance giving more stable tube operation was probably referring to these factors without fully understanding or explaining them.

Last edited by Keit; 17th August 2019 at 07:51 AM.
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Old 17th August 2019, 08:23 AM   #33
sumotan is offline sumotan  Indonesia
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Thank you again Keit for the tutorial.

Cheers
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Old 17th August 2019, 05:08 PM   #34
GoatGuy is offline GoatGuy  United States
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Quote:
Originally Posted by Keit View Post
… you could not get large enough electrolytics to get the ripple low {requiring} at least one choke and sometimes two. {Now} we can get big electrolytics, and not have chokes at all. Tube rectifiers don't like that, but you can use silicon diodes which will



• noise
• stability
• peak power I² power loss
• needing silicon for big cans
• resistors to mitigate higher V

Yes. One thing often lost in these discussions is that the main goals of designing a power supply, like at the top of the list are:

• № 1 - quiet, ripple-free DC output
• № 2 - stiff variable-load regulation
• № 3 - reasonable line-variation independence
• № 4 - piped in A/C noise suppression
• № 5 - very high reliability
• № 6 - inexpensive implementation
• № 7 - possible slow-turn-on HV ramp
It is remarkable how readily some of these are achieved with pretty simple CRC, CLC, LCRC, CLCLC and other chain-of-low-pass filter implementations. № 1, easily. Nix on № 2, though, and № 3. But excellent on № 4, № 5 and № 7. Not necessarily achiving № 6. This would be for valve rectified CLC, with small C₁, modest L₁, and rather large C₂ (reflecting Keit's position on “electrolytics, big, are pretty cheap these days” paraphrased).

Thing is … there is “another way”, that is equally inexpensive, yet optimizes all 7 criteria. Requires some sand … but so silicon rectifiers be!

Using symbol S as 'series regulator', the optimum topology is basically:
C₁LC₂SC₃
The first (not very large) C₁ accumulates a bit more than the minimum full-wave-bridge peak-to-peak energy to turn 100% ripple into perhaps only 5% to 10%. Being small, it doesn't impose a harsh peak-charge-flow current spike on the transformer (or the rectifiers). You could use valve rectifiers, or silicon. Makes little difference …

Then L, again, modest value, because the C₁ is doing the “heavy lifting” of averaging out energy storage and release. L is there as an outstanding high harmonic buzz-of-rectification filter. A few henries is all that is needed. Keeps costs down.

Then C₂, the “medium size” (equal to C₃) reservoir. Gets ripple down to 1% or so. Sets up stable-enough DC for the series regulator.

Then S … a MOSFET-type high-voltage series “source follower” style regulator. Its GATE is driven by a Zener-clamped stack; having Zeners-in-series is cheap and effective at setting a fairly reliable (day-to-day, season-to-season) regulation reference voltage, but not necessarily a particularly precise one (since that “precision” doesn't matter).

Finally another C, C₃ … which is the reservoir that totally squashes whatever series impedance the S regulator has, and brings it down to mΩ. Same value as C₂.
________________________________________

I bring this up (again and again) because it is so easy to implement, so robust, so reliable, and delivers such remarkable ripple-and-noise free output. With all-sand components, nearly forever. Until the capacitors dry out and quit.

Finally — and this is an excellent exercise for those of us who like to compute such things — one can even achieve № 7 slow-turn-on HV ramp as well. When the Zener-clamped voltage reference stack is fed with a very high value resistor linked to another electrolytic capacitor, its charge-up rate can be remarkably slow. I use a series of dirt-cheap 4.7 MΩ resistors (5 of 'em) and a 4.7 µF, 450 V electrolytic (or two 10 µF's in series, each 350 V). The ramp up rate takes nearly 30 seconds to come up to the Zener clamp.

Anyway… that's the main idea.
I admit … its off-topic a bit … but I really believe the 7 points are THE point.

Just saying,
GoatGuy ✓
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Old 17th August 2019, 05:45 PM   #35
claudiomas is offline claudiomas  France
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Quote:
Originally Posted by GoatGuy View Post
Yes. One thing often lost in these discussions is that the main goals of designing a power supply, like at the top of the list are:
• № 1 - quiet, ripple-free DC output
• № 2 - stiff variable-load regulation
• № 3 - reasonable line-variation independence
• № 4 - piped in A/C noise suppression
• № 5 - very high reliability
• № 6 - inexpensive implementation
• № 7 - possible slow-turn-on HV ramp
Anyway… that's the main idea.
I admit … its off-topic a bit … but I really believe the 7 points are THE point.

Just saying,
GoatGuy ✓
here you should go:
https://www.diyaudio.com/forums/solid-state/
bye bye
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Old 17th August 2019, 06:25 PM   #36
GoatGuy is offline GoatGuy  United States
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Quote:
Originally Posted by claudiomas View Post
Nice “poke-in-the-eye”, fellow DIYer.

A bit heavy handed: one could easily use all-vacuum devices to achieve the same end. Cathode-follower with error-amplifier, glow-discharge voltage reference bottles, direct-heated valve rectification. To achieve exactly the same end… of points.

Perhaps you missed the main point of all, “№ 0 - design the amplifier around the desired topology, the power supply to best support it.

This, being the "Tubes" forum, lionizes valve circuits for most every purpose. Yet, in the end, № 0 remains key.

If you for example, or anyone else for that matter, wish to implement your power supply using hand-made selenium rectification stacks in conjunction with hydrogen-mercury vapor rectification, by all means. Go for it.

If you desire points № 1, 2, 3, 4 and 7, AND to use ALL vacuum components and series regulation by cathode-follower + error amplifier. You'll definitely achieve № 0

You'll get everything except economy ... and with entirely the same commentary as I posted above in general.

Anyway…
Nice poke.
I got it.

Just saying,
GoatGuy ✓
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Last edited by GoatGuy; 17th August 2019 at 06:55 PM.
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Old 17th August 2019, 06:32 PM   #37
6A3sUMMER is online now 6A3sUMMER  United States
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claudiomas,

Huh?

The original post was about chokes and tube rectifiers. Yes, the thread went off tracks several times and came back to the original tracks several times.

You posted a link that took us to "Solid State" 'Talk all about solid state amplification'.

I personally do not have a problem with using solid state devices in tube amps, but many do have a problem with that. But as such, we both agree to use this tube forum for tube amps. The title of the forum is not: "Tubes Only". We can all judge what is appropriate, even if I do not always do that myself, forgive me.

I think we can all agree that sometimes we will disagree.

I always say that if all you have in your toolbox is a hammer, you will respond to all problems as if they are nails.

And GoatGuy, you beat me to the point.

Last edited by 6A3sUMMER; 17th August 2019 at 06:39 PM.
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Old 17th August 2019, 07:03 PM   #38
GoatGuy is offline GoatGuy  United States
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Quote:
Originally Posted by 6A3sUMMER View Post
And GoatGuy, you beat me to the point.
LOL… You framed it substantially better than me. The "Tubes" forum isn't exclusively about tubes-for-everything, but rather it is amplifier-by-valve centric and less pedantic in censoring the supporting circuitry blocks.

After all … we regularly read posts of all sorts of biasing and anode-loading ideas using LEDs, Zeners, little semi-custom current regulator boards, and so forth. All very solid in their state of affairs. Even valve-MOSFET cascodes!

Thank you for the support, friend. Warmly welcomed. GoatGuy ✓
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Old 17th August 2019, 07:29 PM   #39
claudiomas is offline claudiomas  France
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wath to said, sorry , i push you to hell doors... i try wen possible to build valve choke psu and we took about that.... but, i said before, for heathers and sometime also HV 315V/420V smps you can also stack thems for more of 1200V ready made mainwell and Co are ready available cheap and no problem so sorry again Guy and 6A3 see you lather on buy buy
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Old 17th August 2019, 07:37 PM   #40
6A3sUMMER is online now 6A3sUMMER  United States
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claudiomas,

It is OK. See you later.
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