Hello Italy,
CLC is easier to make because the quality of the choke is less important.
With choke input you will need a transformer with higher voltage output and you need a better choke.
Choke or Capacitor Input?
There are several chokes you can use. I would go for something like the LL1673 15H 140 mA or LL2742 24H 175 mA . They both cost between 100 and 110 euro. I dont know if there is a dealer in Italy but there are in Germany. 5 H could do the job but then you will need a much higher current through the load resistor. 160/6=32 160/24=6,6 mA
I have been using choke inputs for 30 years now and for me it always works. A choke will never stop working. After twenty years it will do exactly the same as the first day.
I always combine choke input with a shunt supply. BUT an LCRC will also work perfect
Greetings, Eduard
CLC is easier to make because the quality of the choke is less important.
With choke input you will need a transformer with higher voltage output and you need a better choke.
Choke or Capacitor Input?
There are several chokes you can use. I would go for something like the LL1673 15H 140 mA or LL2742 24H 175 mA . They both cost between 100 and 110 euro. I dont know if there is a dealer in Italy but there are in Germany. 5 H could do the job but then you will need a much higher current through the load resistor. 160/6=32 160/24=6,6 mA
I have been using choke inputs for 30 years now and for me it always works. A choke will never stop working. After twenty years it will do exactly the same as the first day.
I always combine choke input with a shunt supply. BUT an LCRC will also work perfect
Greetings, Eduard
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Hello,
It is the DDDAC with choke input.
A few months back i made a change to a bigger input choke. In front of the chassis is the old one inside the new one.
Greetings, Eduard
It is the DDDAC with choke input.
A few months back i made a change to a bigger input choke. In front of the chassis is the old one inside the new one.
Greetings, Eduard
Hello country of tulips, thanks for informations. Hereabouts is a local vendor in Milano "Novarria" selling good transformers and chokes and not much expensive. I bought some from there. I try and see if the store may have some Lundahl too.
Maybe is a bare PC tower case that one where you set the components?
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Make sure the filter does not tend to oscillate, which will happen is L is too large or C is too small or R is not enough.
Hello Italy,
That one is not that big. The other one was much much bigger ( the one in the red box) .
As you can see in the heater supply of my VT25A tube where i also use choke input the transformer is smaller than the choke. And because Lundahl know sells a much bigger choke that can take the same current as the old one i am replacing the old ones.
What you can also see is that the diodes can be much smaller ( so you have a bigger choice!). Because when using a choke input will be at the same level all the time. SO the transformer and the diodes work much better! All the difficult work is done by the choke. So you need a good choke. The shop in Milan only has one input choke ( per ingresso induttivo) and i see the other chokes they have dont look like real good quality. But they are not expensive. BUT i would just buy a Lundahl LL2742 24 henry 175 mA . Because your preamp not uses a high voltage and not to much current i would choose a tube rectifier. Looks nice and sounds better. You can see in the 80 attachment a very nice tube rectifier. You see that the choke input gives a lower output voltage than the capacitor input but the output voltage doesnt change as much when the current changes.
Greetings, eduard
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Well, effectively I thought just to use a tube rectifier (or a hybrid one) and an "all-tube" set may have more sense. The problem is that in the transformer I'm using - quite big but well done, coming from an old dismantled tube amp - hasn't 5 VAC secondary for tube heaters but about a weird 7 VAC so I should lower the final voltage going to the tube rectifier. Full wave rectifier is what I already thought, but HV secondaries aren't center tapped, so a hybrid configuration wouldn't be better maybe?
PS: Lundahl's chokes are very nice, and now I can see how big they are!
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Hello,
The big one ( 5 kilo) is made for high current 1A the choke you need to buy is the same seize as the smaller Lundahl 1,3 kilo. You can see the dimensions in the attachment.
I have a 270-0-270 transformer but it is a bit small to deliver 100mA. That is a lot of current for a preamplifier!
I have some transformers for heater supply too that have 5V 3 or 4A . So there you need a resistor too. What voltages you need for heater supply signal tubes?
If '' high voltage'' is a bit to high you can always change the resistor in an LCRC filter.
Greetings, eduard
The big one ( 5 kilo) is made for high current 1A the choke you need to buy is the same seize as the smaller Lundahl 1,3 kilo. You can see the dimensions in the attachment.
I have a 270-0-270 transformer but it is a bit small to deliver 100mA. That is a lot of current for a preamplifier!
I have some transformers for heater supply too that have 5V 3 or 4A . So there you need a resistor too. What voltages you need for heater supply signal tubes?
If '' high voltage'' is a bit to high you can always change the resistor in an LCRC filter.
Greetings, eduard
Hello, it is not a preamp indeed...Simply I just meant to have a well filtered PSU.
Vc for input tube heaters is 6,3V.
Relating to the pdf of RCA-80, if I'd want to feed the tube rectifier with my other secondary maybe I could use a pair of dropping resistors like that
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Hello Italy,
Sometimes i use this '' technique '' to reduce the voltage like when i have a 5V 4A winding an a 5R4GYB that only takes 2A but bringing down 6,3 to 5 will put a lot of heat in these two resistors.
Usually i will use one switch for all the heaters and a second switch for the high voltage transformer.
In the VT25A single ended i am building now i use seperate transformers for the two Rod Coleman heater circuits( they MUST have seperate ones) one for the input tube ( E80cc/6085) and one for the 5R4GYB heater.
It ended up being heavy but i am not planning to move it around to much.lol
Greetings, Eduard
Sometimes i use this '' technique '' to reduce the voltage like when i have a 5V 4A winding an a 5R4GYB that only takes 2A but bringing down 6,3 to 5 will put a lot of heat in these two resistors.
Usually i will use one switch for all the heaters and a second switch for the high voltage transformer.
In the VT25A single ended i am building now i use seperate transformers for the two Rod Coleman heater circuits( they MUST have seperate ones) one for the input tube ( E80cc/6085) and one for the 5R4GYB heater.
It ended up being heavy but i am not planning to move it around to much.lol
Greetings, Eduard
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Yes, by employing such a voluminous irons all becomes heavy yet it seems a well-organized setup of this amp...Sure, DHT need a more complex filtering system than indirect heater ones.
BTW, since here Lundahl's vendors are scarce I found instead an Audionote choke, 10H/200mA sold by Audiokit.
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The correct formula is (Rs+Rl)/(6*pi*f), or in this case (Rs+Rl)/940 (actually 942). RDH pp1182&ff.