Hello,
For a true choke input you will need chokes from lundahl like the ll1694 or the ll2733. Because these chokes are measured with 50 volts ac you can use more current because with most Pass circuits ac across the chokey will be much lower. See the website from jacket music in Germany.
You will need a transformer which much higher sec voltages. With true choke input the dc voltage will be lower than the ac voltage from the transformer. 2 mH will not give you a choke input.
Read the post from the German on this thread.
Greetings, Edward
For a true choke input you will need chokes from lundahl like the ll1694 or the ll2733. Because these chokes are measured with 50 volts ac you can use more current because with most Pass circuits ac across the chokey will be much lower. See the website from jacket music in Germany.
You will need a transformer which much higher sec voltages. With true choke input the dc voltage will be lower than the ac voltage from the transformer. 2 mH will not give you a choke input.
Read the post from the German on this thread.
Greetings, Edward
Don`t want Toyota Hybrid solution with small C in CLC as mentioned here.
If building CLC, will build proper CLC.
What I want here is "Ford Mustang Fastback V8 petrol sucking LC Choke Input"
Zen: have played around with Duncans PSUD. Finding that from about 10mH choke the DC voltage don`t decrease to much when further increasing mH.
Also current through bridge look much the same when increasing with more mH.
So finding formula with 7,4mH minimum correct.
Hammond has 15mH chokes 159ZG that probably will do the job..?
eduard: thanks for reply!
2mH is much to small yes!
The Lundahl 1694 is rated 3A when in parallell.
Is this max or rated current?
I will probably increase Id to 1,5A on each side, so will go 3A through chokes.
Will then need two Lundahls, and the are very big as I see..
Best
oks
If building CLC, will build proper CLC.
What I want here is "Ford Mustang Fastback V8 petrol sucking LC Choke Input"
Zen: have played around with Duncans PSUD. Finding that from about 10mH choke the DC voltage don`t decrease to much when further increasing mH.
Also current through bridge look much the same when increasing with more mH.
So finding formula with 7,4mH minimum correct.
Hammond has 15mH chokes 159ZG that probably will do the job..?
eduard: thanks for reply!
2mH is much to small yes!
The Lundahl 1694 is rated 3A when in parallell.
Is this max or rated current?
I will probably increase Id to 1,5A on each side, so will go 3A through chokes.
Will then need two Lundahls, and the are very big as I see..
Best
oks
I found that you can use the primary of a big power supply transformer as a choke. At this point I know people will yell and scream that because it's not air gaped this won't work but testing this assumption to the test. I used 3 different power transformers and they all worked fine as chokes. In one case I used a 120v 500va transformer that in normal duty as a transformer would be limited to 4.17 A on the primary. When used in a choke input power supply and tested with an 8A load . My output voltage was only about 5% different than my rough calculation had predicted.
Hello,
All interested in choke input power supply take a look her:
Choke or Capacitor Input?
You will see that you need some current running all the time by adding a bleeder resistor. The bigger the number of mH your choke has the less current you need to bleed.
The LL1694 has a recommended current of 3 A. It can cope with 25 volts ac across the choke. With less voltage the admissabler current can be higher. See Jac Music website in Germany.
There is also the ll2733 it will be 100 mH in parallel, 3,4 A with 60 volts rms with 30 volts rms it will be 4,4 A. Like this it will be 0,85 ohm. The ll1694 is 0,45 ohm but inductance will be 40mH and not 100 mH
Of course there will be high peak at start up. I think when using the right value bleeder there will be none. If you use just 2 mH i think there will be no peak and the dc voltage will be close to without a choke but it will not be a real choke input. With real choke input the dc voltage will be lower than the ac voltage you put into the filter.
Greetings, Eduard
All interested in choke input power supply take a look her:
Choke or Capacitor Input?
You will see that you need some current running all the time by adding a bleeder resistor. The bigger the number of mH your choke has the less current you need to bleed.
The LL1694 has a recommended current of 3 A. It can cope with 25 volts ac across the choke. With less voltage the admissabler current can be higher. See Jac Music website in Germany.
There is also the ll2733 it will be 100 mH in parallel, 3,4 A with 60 volts rms with 30 volts rms it will be 4,4 A. Like this it will be 0,85 ohm. The ll1694 is 0,45 ohm but inductance will be 40mH and not 100 mH
Of course there will be high peak at start up. I think when using the right value bleeder there will be none. If you use just 2 mH i think there will be no peak and the dc voltage will be close to without a choke but it will not be a real choke input. With real choke input the dc voltage will be lower than the ac voltage you put into the filter.
Greetings, Eduard
Thanks for that link.
Here is a link to the Hammond page that clearly sets out the expected voltages and currents for various rectification schemes and input (C, L, R) types.
http://www.hammondmfg.com/pdf/5c007.pdf
Hello,
In the link about the dc filament supply the transformer doesnt have a high secundairy voltage. So if there is a peak during switch on the peak will not be that high so 35 volt dc caps will be safe.
BUT with the PASS amps ac voltages will be higher and the transistors in the circuit probably will not like the high voltage peaks which occur all the time.
If you can tame the peak by using a proper bleeder and thge right value choke you can use caps with higher capacity because you can get the ones with lower dc voltage.
So far only very few people use real choke input for their Pass amps. A pity they are to heavy to send on a big trip.
Greetings, Edward
P.s most of the useful info on choke input already has been published. At the time i did use chokes in my Hiraga there was only one usefull choke on the market. NOW there is Lundahl which i think are technically superior.
In the link about the dc filament supply the transformer doesnt have a high secundairy voltage. So if there is a peak during switch on the peak will not be that high so 35 volt dc caps will be safe.
BUT with the PASS amps ac voltages will be higher and the transistors in the circuit probably will not like the high voltage peaks which occur all the time.
If you can tame the peak by using a proper bleeder and thge right value choke you can use caps with higher capacity because you can get the ones with lower dc voltage.
So far only very few people use real choke input for their Pass amps. A pity they are to heavy to send on a big trip.
Greetings, Edward
P.s most of the useful info on choke input already has been published. At the time i did use chokes in my Hiraga there was only one usefull choke on the market. NOW there is Lundahl which i think are technically superior.
Hello,
The bleeder should give the power supply a steady load that will always be there. In a LCLC or LCRC i always did put it across the terminals of the first cap. Pay attention it could get pretty hot so better have an aluminium wire wound connected to the chassis or heatsink and dont let it heat up the cap!
Somewhere i did read about an optimum relationship between value of the bleeder current compared to the total current drawn( bleeder plus circuit). I must have it somewhere. If i remember well you should try to use a choke value that allows you to bleed a current that will keep the dc output voltage to a constant value that will not be changed a lot by adding the circuit.. Something like 10% load by bleeder 90% load by the circuit.
Let someone try a real choke first lol.
Greetings, Edward
The bleeder should give the power supply a steady load that will always be there. In a LCLC or LCRC i always did put it across the terminals of the first cap. Pay attention it could get pretty hot so better have an aluminium wire wound connected to the chassis or heatsink and dont let it heat up the cap!
Somewhere i did read about an optimum relationship between value of the bleeder current compared to the total current drawn( bleeder plus circuit). I must have it somewhere. If i remember well you should try to use a choke value that allows you to bleed a current that will keep the dc output voltage to a constant value that will not be changed a lot by adding the circuit.. Something like 10% load by bleeder 90% load by the circuit.
Let someone try a real choke first lol.
Greetings, Edward
Hello,
Adding resistor in series with a choke will reduce filtering.
You can always try to see what happens if you don't use a bleeder. Pass amps don't have to many parts. But if only one side of the power supply goes wrong you might get big dc voltage on your speakers.
When switching to a real choke input you will need a higher ac voltage anyway.
Good luck, edward
Adding resistor in series with a choke will reduce filtering.
You can always try to see what happens if you don't use a bleeder. Pass amps don't have to many parts. But if only one side of the power supply goes wrong you might get big dc voltage on your speakers.
When switching to a real choke input you will need a higher ac voltage anyway.
Good luck, edward
Hello,
No change in ripple voltage but according to me the power supply will lose some speed or not. The resistor will slow down the charging of the cap for sure or not?
With my Hiraga amp (CLC in stead of the standard CRC) i did use a 500VA EI core transformer 68.000 microfarad 200 mH choke 2*330.000 microfarad. All caps 25 volts nominal voltage but after a few years one of the 68.000 microfarad did start leaking through the safety vent. Probably the pressure did build up very slowly so there wasant a big BOOM.
This amp was on 24 hours every day. During switch on there was always a bit higher voltage for a few seconds? ( i forget how long because this is 35 years ago)
If i am right the biggest problem will occur during switch on but once switched there will be pulses too.
The big Telefunken chokes one of part suppliers have 2 windings of 32 mH .But they are big and heavy (3,5 kilogrammes) Wire diameter is2,2 millimeter. THe ones i have were 1,1 and 1,7 mm. Did test both with more than 2A. THe 8 A rated power transformer did get warmer than these chokes.
If you dont have the space one should go for the Lundahls.
If i ever build a Pass amp i will try both telefunken and Lundahls. And of course R core transformer no toriods for me lol.
Will take a break here for a few weeks untill someone has the guts to spend some money on a choke. I think the telefunken can handle a stereo amp and with the lundahl you will have to check the website of Jac music in Germany to see if you need to put the 2 coils in parallel.
Greetings, Edward
No change in ripple voltage but according to me the power supply will lose some speed or not. The resistor will slow down the charging of the cap for sure or not?
With my Hiraga amp (CLC in stead of the standard CRC) i did use a 500VA EI core transformer 68.000 microfarad 200 mH choke 2*330.000 microfarad. All caps 25 volts nominal voltage but after a few years one of the 68.000 microfarad did start leaking through the safety vent. Probably the pressure did build up very slowly so there wasant a big BOOM.
This amp was on 24 hours every day. During switch on there was always a bit higher voltage for a few seconds? ( i forget how long because this is 35 years ago)
If i am right the biggest problem will occur during switch on but once switched there will be pulses too.
The big Telefunken chokes one of part suppliers have 2 windings of 32 mH .But they are big and heavy (3,5 kilogrammes) Wire diameter is2,2 millimeter. THe ones i have were 1,1 and 1,7 mm. Did test both with more than 2A. THe 8 A rated power transformer did get warmer than these chokes.
If you dont have the space one should go for the Lundahls.
If i ever build a Pass amp i will try both telefunken and Lundahls. And of course R core transformer no toriods for me lol.
Will take a break here for a few weeks untill someone has the guts to spend some money on a choke. I think the telefunken can handle a stereo amp and with the lundahl you will have to check the website of Jac music in Germany to see if you need to put the 2 coils in parallel.
Greetings, Edward
Hello,
Copy and paste from Lundahl power transformer data sheet.
Output current from rectifier: 63% of above with cap. input rectifier, 95% of above with choke input rectifier.
Using choke input will give the transformer a much easier life. Difficult to explain in English for me. But with cap input there is a like a '' pulsating '' current flow that generates more heat than the steady current flow you will achieve with a choke input.
There is some information about this on the jac music website in Germany.
Copy and paste from Lundahl power transformer data sheet.
Output current from rectifier: 63% of above with cap. input rectifier, 95% of above with choke input rectifier.
Using choke input will give the transformer a much easier life. Difficult to explain in English for me. But with cap input there is a like a '' pulsating '' current flow that generates more heat than the steady current flow you will achieve with a choke input.
There is some information about this on the jac music website in Germany.
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