Thanks John
Yes I've only just realised how wasteful I took my daughter to singapore for a week as she finished her degree and bought some tango opts and choke and some other components I had asked for a 5mH 250mH choke he only 300mH choke and just going over the spec sheet and realised its for LC filter,I dont speak chinese and his english wasn't that good so that could be a reasonable excuse. Could you please explain the fine tune I'm still on the steep learning curve.
Thanks Nigel
Yes I've only just realised how wasteful I took my daughter to singapore for a week as she finished her degree and bought some tango opts and choke and some other components I had asked for a 5mH 250mH choke he only 300mH choke and just going over the spec sheet and realised its for LC filter,I dont speak chinese and his english wasn't that good so that could be a reasonable excuse. Could you please explain the fine tune I'm still on the steep learning curve.
Thanks Nigel
Nigel,
Well an LC filter gives just over 0.9x the AC input voltage as DC out, and the CLC gives about 1.4x.
So no input cap gives 0.9 and a big cap gives 1.4.... You can choose a cap value to deliver any voltage in between. It really becomes a hybrid.
If you don't already have it, download PSUD2 free at:
Duncans amp pages
Set it up as a CLC filter and start reducing the input cap and see what happens....
The nice thing is that your choke will never buzz for any value of input C, unlike a choke designed for CLC
Well an LC filter gives just over 0.9x the AC input voltage as DC out, and the CLC gives about 1.4x.
So no input cap gives 0.9 and a big cap gives 1.4.... You can choose a cap value to deliver any voltage in between. It really becomes a hybrid.
If you don't already have it, download PSUD2 free at:
Duncans amp pages
Set it up as a CLC filter and start reducing the input cap and see what happens....
The nice thing is that your choke will never buzz for any value of input C, unlike a choke designed for CLC
Me too
but I run it in Virtual PC on my G4 and Parallels on my iMac and MacBook.If you have an IntelMac, you can download a free trial of Parallels Desktop for mac http://www.parallels.com/en/products/workstation/mac/
There is also Crossover Office for Mac from Codeweavers, who also offer a 60 day trial (beta) Th app's not listed but I might just try it....
Nigel,
I should mention that you will need an operating system to install in your Parallels Virtual Machine. PSUD2 works on all Windows, I think, but for simplicity of installation, one that boots from the installation CD is necessary. I believe that means no earlier than Win98 version B.
Of course I forgot about Apple's free Bootcamp
But you need XP....
Oh BTW I have checked PSUD2 running in Crossover Office Version 6.0b3a (6.0.0b3a) and there is a problem. It is not possible to tick the results boxes. So no-go.
I should mention that you will need an operating system to install in your Parallels Virtual Machine. PSUD2 works on all Windows, I think, but for simplicity of installation, one that boots from the installation CD is necessary. I believe that means no earlier than Win98 version B.
Of course I forgot about Apple's free Bootcamp
But you need XP....Oh BTW I have checked PSUD2 running in Crossover Office Version 6.0b3a (6.0.0b3a) and there is a problem. It is not possible to tick the results boxes. So no-go.
Hi all,
Can someone (maybe John) explain the basic difference between CLC & LC chockes ?
What's the way to identify a salvaged one ? Also is there a method to figure out current rating of a salvaged chocke ?
... and finally, can you explain why the LC chocke won't buzz in a CLC circuit ?
thanks again
Can someone (maybe John) explain the basic difference between CLC & LC chockes ?
What's the way to identify a salvaged one ? Also is there a method to figure out current rating of a salvaged chocke ?
... and finally, can you explain why the LC chocke won't buzz in a CLC circuit ?
thanks again
Ok, I'll try. I'm happy to hear corrections and additions...
Chokes for LC use have a gap similar to that of a Single-Ended output transformer to allow significant DC before saturation.
An added benefit is that the inductance changes with current and so it can be used to provide crude regulation over a small range of current demand.
More later... supper's ready....
I'll keep pedalling slowly... ...
To identify the type, look at the way the laminations are stacked. A CLC type will most likely have the laminations interleaved, ie EI then IE then EI etc. A choke for LC will have all the E's one side and all the I's the other. There will also be a thin piece of non-magnetic spacing material between the E stack and the I stack.
The current rating is not so easy, as a 10H 250mA choke will be similar in size to a 5H 500mA choke. If you can measure the inductance, then it is possible to arrange a DC current to see at which point the inductance drops.
By far the best way is to look at the equipment that the choke has been salvaged from. If it's an amplifier, check the output valve type and quantity. You can estimate the current drawn.
I have heard however, that some old chokes have deteriorated in performance. I don't know why.
Buzz:
Mechanical buzz often happens when you use a gapless (CLC) choke in an LC configuration. I'll leave it to you to run PSUD2 configured this way and plot the waveform of the current passing through the choke...
Oh, by the way, a CLC circuit with a very small first capacitor is almost the same as an LC circuit, from the choke's experience.
...To identify the type, look at the way the laminations are stacked. A CLC type will most likely have the laminations interleaved, ie EI then IE then EI etc. A choke for LC will have all the E's one side and all the I's the other. There will also be a thin piece of non-magnetic spacing material between the E stack and the I stack.
The current rating is not so easy, as a 10H 250mA choke will be similar in size to a 5H 500mA choke. If you can measure the inductance, then it is possible to arrange a DC current to see at which point the inductance drops.
By far the best way is to look at the equipment that the choke has been salvaged from. If it's an amplifier, check the output valve type and quantity. You can estimate the current drawn.
I have heard however, that some old chokes have deteriorated in performance. I don't know why.
Buzz:
Mechanical buzz often happens when you use a gapless (CLC) choke in an LC configuration. I'll leave it to you to run PSUD2 configured this way and plot the waveform of the current passing through the choke...
Oh, by the way, a CLC circuit with a very small first capacitor is almost the same as an LC circuit, from the choke's experience.
Thanks John, all this is very clear to me now, a few more words...
Do you think the diameter of the wire can be a accurate indicator of current rating ?
For your suggested method, I have a DMM that have a Lmeter function, But if I follow you well on the connection, I wonder then if the modern DMM generator will appreciate the DC offset (I think it's supposed to measure "offline" chockes) but I'm not sure, any idea about this?
For sure ! But unfortunately not allways possible, I have a few chockes hanging around here...
Do you think the diameter of the wire can be a accurate indicator of current rating ?
For your suggested method, I have a DMM that have a Lmeter function, But if I follow you well on the connection, I wonder then if the modern DMM generator will appreciate the DC offset (I think it's supposed to measure "offline" chockes) but I'm not sure, any idea about this?
Indeed the wire gauge would be a good indicator if you can see it. There are several members with winding experience who will be able to advise you.
Passing DC through a choke while connected to a multimeter:
Well, I've never done it myself! But, my old Marconi Universal bridge does allow this, which I have done! I believe it adds a very large capacitor in series with the choke to block the DC. There is a chance that the large energy stored in such a capacitor could damage your meter, so I can't recommend it.
A more direct way might be to bread-board a low voltage rectifier and load to test it.
OK I've run out of ideas
Watch the thread to see what I've missed
I'll post the schematic of my Marconi as soon as my wife gets off the other computer (it's on an un-mounted external drive). I'm relegated to the laptop....
Passing DC through a choke while connected to a multimeter:
Well, I've never done it myself! But, my old Marconi Universal bridge does allow this, which I have done! I believe it adds a very large capacitor in series with the choke to block the DC. There is a chance that the large energy stored in such a capacitor could damage your meter, so I can't recommend it.
A more direct way might be to bread-board a low voltage rectifier and load to test it.
OK I've run out of ideas
Watch the thread to see what I've missed
I'll post the schematic of my Marconi as soon as my wife gets off the other computer (it's on an un-mounted external drive). I'm relegated to the laptop....
Well, both types of chokes will have a gap, so they will both have all the E's on one side and all the I's on the other. Really, they're similar and there's no hard line to place between them. What makes a choke suitable for choke-input (LC) duty is that it is designed to handle a larger AC voltage across it. Generally speaking, if you have two chokes with the same inductance and current ratings, the bigger one will be less likely to saturate (and buzz) when used as an input choke.
An input choke (LC) will have an rms AC voltage across it about 1/2 the rms voltage of the transformer. Sometimes you see vintage chokes with a rating printed on them. Sometimes it's just a squiggly line followed by a number, for example: ~100VAC. Often, the rating is conservative if it's an old potted unit, so you might get away with quite a bit more than the rating.
Adding a small cap before the choke will sometimes quiet down a buzzing choke without increasing the output voltage much. Some people report that the amp sounds better that way anyhow...
-- Dave
An input choke (LC) will have an rms AC voltage across it about 1/2 the rms voltage of the transformer. Sometimes you see vintage chokes with a rating printed on them. Sometimes it's just a squiggly line followed by a number, for example: ~100VAC. Often, the rating is conservative if it's an old potted unit, so you might get away with quite a bit more than the rating.
Adding a small cap before the choke will sometimes quiet down a buzzing choke without increasing the output voltage much. Some people report that the amp sounds better that way anyhow...
-- Dave
At the risk of being ordered to get back in my box, I always thought the opposite of what dhaen said.
As I understand it, a choke designed for LC filter use is called a swinging choke. Its inductance gradually falls as the current increases. This is achieved by having a very small gap in the core, so that the onset of saturation and the consequent fall in inductance occur gradually. Because its gap is so tiny, the core of a swinging choke is smaller than a CLC filter choke for the same starting inductance, i.e. a 10Hy-2Hy swinging choke has a smaller core than a 10Hy CLC choke.
A choke intended for CLC filter use has a bigger gap, like an output transformer for SE. Its inductance over a range of current stays fairly constant, until saturation is reached, when it drops suddenly. The core must be bigger, for a given inductance, because of the gap.
Please correct me if I am wrong and I will galdly return to my box.
As I understand it, a choke designed for LC filter use is called a swinging choke. Its inductance gradually falls as the current increases. This is achieved by having a very small gap in the core, so that the onset of saturation and the consequent fall in inductance occur gradually. Because its gap is so tiny, the core of a swinging choke is smaller than a CLC filter choke for the same starting inductance, i.e. a 10Hy-2Hy swinging choke has a smaller core than a 10Hy CLC choke.
A choke intended for CLC filter use has a bigger gap, like an output transformer for SE. Its inductance over a range of current stays fairly constant, until saturation is reached, when it drops suddenly. The core must be bigger, for a given inductance, because of the gap.
Please correct me if I am wrong and I will galdly return to my box.
ray_moth said:
Not necessarily. One problem with an LC supply is that a minimum current must be drawn before it works properly and the correct output voltage is achieved. If too little current is drawn, the circuit reverts to pulse charging and the output voltage rises towards what would have been achieved using a capacitor-input supply. The lower the current drawn, the larger the inductance needed to ensure correct operation. If the supply feeds a load drawing a constant current, there isn't a problem, but Class B amplifiers draw a small idle current and a much larger full power current. One way to deal with this is to use a swinging choke that has a large inductance at low currents and lower inductance at higher currents as suggested by ray_moth.
For an LC supply feeding a constant current load, there's no advantage in using a swinging choke. What is needed is a choke that can withstand the maximum peak current demanded of it (the sum of the DC load current and the peak AC ripple current).
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