hi all,
here http://www.emissionlabs.com/Article...2-Circuit-Topology-for-Tube-Power-Supply.html
you can find the following statement :
" Circuit 5: This is how to connect a double coil Choke, such as the Lundahl LL1673 or similar products. Beware the polarity of the connections. (the dots in the circuit diagram here). The importance of this circuit is very high. We have complete inductive separation of the transformer from the amplifier. Definitely, the transformer capacitance from primary to secondary can not inject an AC hum current into the amplifier any more.
Design Quality of Circuit 5: Five Stars ***** "
in another word, this is the best possible connection with Lundahl chokes according to datasheet.
The question:
can I use this Circuit 5 connection not in CLC (capacitor input) mode but in LC (choke) mode?
as shown in the diagram below
here http://www.emissionlabs.com/Article...2-Circuit-Topology-for-Tube-Power-Supply.html
you can find the following statement :
" Circuit 5: This is how to connect a double coil Choke, such as the Lundahl LL1673 or similar products. Beware the polarity of the connections. (the dots in the circuit diagram here). The importance of this circuit is very high. We have complete inductive separation of the transformer from the amplifier. Definitely, the transformer capacitance from primary to secondary can not inject an AC hum current into the amplifier any more.
Design Quality of Circuit 5: Five Stars ***** "
in another word, this is the best possible connection with Lundahl chokes according to datasheet.
The question:
can I use this Circuit 5 connection not in CLC (capacitor input) mode but in LC (choke) mode?
as shown in the diagram below
I think it is according to Emission Labs:
http://www.emissionlabs.com/Article...2-Circuit-Topology-for-Tube-Power-Supply.html
If you read Lundahl datasheet, the LL1673 (for example 10H version, serial connection for improved CMR) saturating current is 290mA.
I'm afraid that in your schematic the charging pulses of first capacitor (even few hundred mA pulses if you use large capacitor!) + static 60mA load exceeds this.
In the "circuit 5." the current trough CMR choke equal the load, largely static. The charging pulses passes through the first capacitor.
I'm afraid that in your schematic the charging pulses of first capacitor (even few hundred mA pulses if you use large capacitor!) + static 60mA load exceeds this.
In the "circuit 5." the current trough CMR choke equal the load, largely static. The charging pulses passes through the first capacitor.
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in the schema above, you will not find the first capacitor. because this is choke load - LC, there is NO first capacitor.
RECTIFIER 274B - LUNDAHL CHOKE LL1673 - CAPACITOR
so question is
can I use this Circuit 5 connection with LC mode without the first capacitor?
Ok, please could you give any recommendation for the bleeding resistor in choke input mode?
because I know that ensuring sufficient current draw for a choke input supply is an issue.
The bleeding resistor only need for recharge the capacitor after shutdown (few hundred kOhm, depending on voltage and capacitance).
The load (mainly type A /pre/amplifier) current (steady part) requiring for proper working of choke input mode PSU.
If you haven't enough current, must to use "dummy" load (large dissipation may occurs!), but it's always depends of design of amplifier.
The load (mainly type A /pre/amplifier) current (steady part) requiring for proper working of choke input mode PSU.
If you haven't enough current, must to use "dummy" load (large dissipation may occurs!), but it's always depends of design of amplifier.
read a lot of different threads here the last couple of days and it looks like Lundahl's CMR connection scheme is not too popular, although no one says anything negative. everyone seems to be using Lundahl chokes the old-fashioned way, like all other chokes.
@euro21 @Rod Coleman @mogliaa @andyjevans
do you have any opinion or experience regarding the benefits of using Lundalh CMR for chokes (and choke input mode in particular)?
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Why don't you ask Raaf61 about his CMR experience?
https://www.diyaudio.com/community/threads/45-se-amp.334647/page-4
https://www.diyaudio.com/community/threads/45-se-amp.334647/page-4
You should ask Lundahl for the test AC voltage and DC current used to measure the inductance. A choke input circuit applies a much higher AC voltage (hundreds of volts) across the choke than when used in a CLC circuit (likely below 10V), and that changes the inductance a lot.
Your power transformer will have capacitance between the HT secondary winding and the core - that stray capacitance can allow hum/noise current to flow to chassis ground, and hence to the ground symbol in your schematic, and so will bypass the Lundahl choke's lower arm inductance, and so you may not achieve the hum/noise reduction that you anticipated. This was a known situation 90 years ago when chokes were sometimes placed in the negative leg of power supplies (to reduce the insulation requirement in the choke).
Your power transformer will have capacitance between the HT secondary winding and the core - that stray capacitance can allow hum/noise current to flow to chassis ground, and hence to the ground symbol in your schematic, and so will bypass the Lundahl choke's lower arm inductance, and so you may not achieve the hum/noise reduction that you anticipated. This was a known situation 90 years ago when chokes were sometimes placed in the negative leg of power supplies (to reduce the insulation requirement in the choke).
thanks so much!
According to the datasheet, it seems i have a good overhead, 300V AC at the secondary winding
and from the @euro21 link this schema works in much more drastic env
370V AC and more current
Regarding hum/noise
do you mean that the power transformer should have an interwinding screen?
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The max VAC is not the same as the voltage used to measure the inductance. The sad thing is that the Vac for inductance is not stated.
Regarding hum/noise - a screen between primary and secondary could be connected to the CT, as that should divert a fair percentage of secondary side capacitive current back to the CT, rather than reaching the core. However the choke then forces that screen to quite a high Vac with respect to gnd, so maybe not so straightforward.
Regarding hum/noise - a screen between primary and secondary could be connected to the CT, as that should divert a fair percentage of secondary side capacitive current back to the CT, rather than reaching the core. However the choke then forces that screen to quite a high Vac with respect to gnd, so maybe not so straightforward.