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| Introduction (the Part number below, is the same as in the pricelist | |||||
Part 1 |
Tube Power Supply Chokes) | Part14..20 |
Tube Output | ||
 |
Filament Chokes / High Current Chokes | Part 21 |
Tube Mains transformers with DC cancellation | ||
Part 3 |
Plate (anode) Chokes | Part 22 |
Mains Cleaning transformers with DC cancellation | ||
Part 4 |
Grid Choke | Part 23 |
Various transformers, not mentioned here | ||
Part 5 |
Interstage | ||||
Part 6 |
Signal Input | ||||
Part 7 |
Signal Output | ||||
Part 9 |
Moving Coil | ||||
Part 10 |
Guitar Input | ||||
Part 11 |
Tech Info |
Product Storage | |||
Part 12 |
For Digital Audio. Finest Quality. | Tech Info |
Amorph Cores | ||
Part 13 |
Interconnect Solutions | Tech Info |
DATASHEET DOWNLOAD | ||
Filament chokes or High Current chokes
Introduction
When we build a passive power supply stabilization with a choke, the remaining AC noise is in same range as with an series regulator. This is of course provided you use a good quality choke. What we do not have of course, is the electronic regulation, but as long as we know that the load is not changing very much, the correct output voltage will be achieved still. However, with a choke we solve some of the severe disadvantages a non-choke circuit has.
Here are some audiophile reasons to use a choke in the power supply
If you want to have some fun, post on audioasylum a question about what to do when your tube amplilfier makes a noice, best described as hummmm....
1 |
Transformer Size |
A mains transformer is always specified for a resistive load. if you load it purely with a very big capacitor as first element , you must reduce the output capacity of the transformer with 1/3. This is completely normal for all transformers, and of course also for the Lundahls. Reasons is, the charge impulses into the capacitor will saturate the transformer core. Above a certain limit, mechanical hum will occur. So to avoid this, the mains transformer is advised to choose larger as you need. With a choke stabilized power supply, you can (and you should) make the first capacitors lower, and in that way keep the mechanical hum low. |
2 |
The transformer output wave shape. |
The AC signal of the mains transformer gets quite distorted when it is loaded with many rectifier circuits, using a big capacitor. Take a scope, and you will see it. This bad wave shape is nothing but strong harmonics on the mains voltage. So that means frequencies of 100Hz and 150Hz, 200Hz, etc. of high amplitude. To make it worce, any transformer allways works in two directions, and will couple this contamonation back into the mains. These frequency elements are unpleasant to hear, and some small remains of 50Hz hum will sound louder than expected, if contaminated with higher frequency elements. So 1mV hum on the speakers can be inaudible if 50Hz, but is audible if 100Hz and 150Hz, 200Hz are added. The noise becomes somewhat rattling character, perhaps you know this kind of noise. |
3 |
Efficiency |
Electronically generated heat is expensive. Experienced designers calculate with a few Euro per Watt. So if you heat 10 Watt into a series regulator, you can have 50 Euro additional costs. The mains transformer must be 10 Watt larger, the power supply capacitors are 20% higher value. You need to buy the series regular too, the cooling plate, the isolation mica, and some other components. Chokes produce some heat too, but not when they have windings technique like Lundahl. |
4 |
Reliability |
Free wiring introduces inductance which can cause small or larger oscillations in the RF range. Reason is, series regulator IC's by default are instable devices. They can do high current, and have very high gain inside. An partial oscillation will be unnoticed often, specially for filament supplies. The result is, the RMS output voltage is higher than indicated in (any normal) voltmeter since they can not measure RF voltage. So you can have 5V on a voltmeter, and 6Volt RMS without being aware. You would not be the first one damaging expensive tubes this way. Furthermore the RF signal will generate audible noise when it gets into amplifier circuits. Everybody thinks that will only happen to others, until you connect a scope to the series regulator, and get the surprise of your life. Specially the Low Drop regulators are very sensitive for that, since these have even higher gain inside. Another issue with those is, you can get a short oscillation when connecting long voltmeter wires to the IC connections. This really IS a potential problem, and with a choke solution, this is eliminated. |
5 |
Complexity |
A lower complexity for the same solution, is something good. Less solid state inside |
6 |
Forgotten reasons |
Let me know if there are any. Probably yes. |
Designing with the LL1694
This choke has two windings, that you can either use in parallel or series. (Connect them the right way, or you will create a resistor only).
The chokes are specified to have their inductance and DC current, with a certain AC Voltage over the choke. Without going into theory, let's just say that if that AC voltage is lower as maximum, the DC current can he higher as maximum. This means you can inmost cases get more DC current out of the choke as you think. To avoid formulas, I just put in it a table here:
Both coils in Series |
Both coils in parallel |
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AC Voltage over the choke |
Maximum DC Current |
AC Voltage over the choke |
Maximum DC Current |
|
LL1693-1.5A |
25V~ |
1,5A |
12,5V~ |
3.0A |
LL1693-1.5A |
20V~ |
1,7A |
10V~ |
3,4A |
LL1693-1.5A |
15V~ |
1,9A |
7,5V~ |
3,7A |
LL1693-1.5A |
10V~ |
2,0A |
5V~ |
4,1A |
LL1693-1.5A |
5V~ |
2.2A |
2,5V~ |
4,4A |
LL1693-1.5A |
0V~ |
2,4A |
0V~ |
4,8A |
LL1693-2A |
25V~ |
2,0A |
12,5V~ |
4,0A |
LL1693-2A |
20V~ |
2,2A |
10V~ |
4,0A |
LL1693-2A |
15V~ |
2,5A |
7,5V~ |
5,0A |
LL1693-2A |
10V~ |
2.7A |
5V~ |
5,4A |
LL1693-2A |
5V~ |
3,0A |
2,5V~ |
5,9A |
LL1693-2A |
0V~ |
3,2A |
0V~ |
6,4A |
