Hello,
Of course if you use the Rod Coleman with a standard '' pre regulation '' it will not be noisy. This does not mean it cannot be improved. In the USA Dave Slagle designed a choke input to be used with the Rod Coleman supply.
BUT i have used different chokes with a normal LM350 k supply, with Rod Coleman in my line preamplifier and in my power amplifier.
I am using choke input in the power supply of my DDDAC, in the high voltage supplies of my phono preamp, my line preamp and my power amp. ALL of them use a shunt power supply.
I have used normal price chokes, i have used the MC series from Tango ( designed for choke input) and i have used different values of Lundahl.
So everyone can decide themselves if they wanna try a choke input.
Bye bye, eduard
I would disagree here. I use choke input on my 26 filaments before Rod's regs. I use whatever Hammond can take 1 amp, in my case 159ZC, 60mH at 2A. Plus I have some bigger chokes from a job lot. Better sound quality. I can well imagine that a choke-less supply is noiseless, but that's not the whole story when it comes to quality of sound. Each improvement, whatever it is, is worth it to me.
Hello,
As you can see in the attachment i am using choke input all over!
In the attachment you can see the seize of my old transformer and the little Lundahl ( 544mH) used for choke input for my DDDAC. NOW it has been replaced with a 3000mH and a much smaller transformer. I have tried going for bigger chokes and usually it is a big improvement. The bigger the choke the smaller the transformer. A bigger choke will not be double the price with a transformer prices go up much quicker.
As said before you must take care of using the right value. If you have a choke input with a 20 volt ac transformer the dc output should alwaqys be under 20 volts dc. If it is higher it is not a 100% choke input.
Greetings, Eduard
Attachments
Hello,
For my vt25a heater supply i use the Rod Coleman with an LCRC input. Choke is 544 mH. This is a power amp and i guess with a preamplifier difference could be bigger. There was no room for a bigger one.
What i like about the lundah is their design. They filter a lot better because their anode chokes are exactly made the same way. They radiate less because of the two coils construction. I have tried the 544 mH 1,25A with current higher than 1,6 A and they still wouldnt buzz.
Greetings, Eduard
Andy,
General chokes (Hammonds and most of Lundahls too) not designed for (large current) choke input job.
The choke loaded filament raw supply first capacitor charging pulses overstressed he average choke, so "thumb rule" choice (choose three times bigger current capacitance than DC current) is only appearance solution.
Even the low current #26 Rod Coleman heater supply generates 0.5A more pulses in choke than 1A DC filament current.
Chokes designed for (for example 2-5A) choke input operation are heavy (2-5kg), robust, thick wire monsters, which are expensive too.
Lundahl made some filament choke (LL1694, 2733) -Thomas Mayer loves its- but these are at larger current than recommended also tend to saturate.
Some years ago I tried choke loaded filament (á la Vinylsavor) for my 801a PSE -without R.C-.
I have two -made in Japan- 40mH 5A chokes (2mm output wires), but these -for christ's sake- large as a half brick and 4kg each!
I stayed with my ordinary solution: C-CMC-C-L (or R)-C and R.Coleman.
General chokes (Hammonds and most of Lundahls too) not designed for (large current) choke input job.
The choke loaded filament raw supply first capacitor charging pulses overstressed he average choke, so "thumb rule" choice (choose three times bigger current capacitance than DC current) is only appearance solution.
Even the low current #26 Rod Coleman heater supply generates 0.5A more pulses in choke than 1A DC filament current.
Chokes designed for (for example 2-5A) choke input operation are heavy (2-5kg), robust, thick wire monsters, which are expensive too.
Lundahl made some filament choke (LL1694, 2733) -Thomas Mayer loves its- but these are at larger current than recommended also tend to saturate.
Some years ago I tried choke loaded filament (á la Vinylsavor) for my 801a PSE -without R.C-.
I have two -made in Japan- 40mH 5A chokes (2mm output wires), but these -for christ's sake- large as a half brick and 4kg each!
I stayed with my ordinary solution: C-CMC-C-L (or R)-C and R.Coleman.
Hello,
NEVER had any problem like buzzing with Ll2771, LL2733 or LL1694 used for choke input even if used with 10 20% more current then their indicated value.
That is all i type two fingers.
Felipe i can send you a pair of vintage 100mH 1,1 A for 15 euro each can be used for choke input dont know if they are better than the Lundahl but i am sure they are professional made by Bourdereau. FRENCH EMT GOOGLE FOR BOURDEREAU PLATINE. greetings, Eduard
NEVER had any problem like buzzing with Ll2771, LL2733 or LL1694 used for choke input even if used with 10 20% more current then their indicated value.
That is all i type two fingers.
Felipe i can send you a pair of vintage 100mH 1,1 A for 15 euro each can be used for choke input dont know if they are better than the Lundahl but i am sure they are professional made by Bourdereau. FRENCH EMT GOOGLE FOR BOURDEREAU PLATINE. greetings, Eduard
YES, and they even indicate the maximum voltage across the chokes.
The Bourdereau i have are 100mH, 1,3A and 1,3 ohm. 1,3 A so you can have a little bleeder .Sending a pair to Catalonia would be 12 euro
@ Felipe send me a private message so you can tell me if you need a choke for the high voltage too? I have a lot but i need to know the current rating and if it will be choke input or not.
Greetings, Eduard
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It's a good thing if you don't have problem, but the saturating does not cause absolutely buzzing.
It's may producing distortions, so operating choke at the border you lose that advantage cause choke input PSU: larger suppression from mains and from rectifier.
Basic engineering approach: if there is no disturbance, it does not need to be filtered.
If the device in the PSU filtering stage itself generates "noise", deteriorating filtering efficiency.
For example because of this use Dave Slagle not choke input, but differential mode dual choke, where the forward and returning current in differential mode -not so- overstressed the choke' flux:
intact audio
Vinylsavor also use Lundahl filament chokes as smoothing choke and not "classical" input choke:
VinylSavor: November 2012
Choke input PSU is good thing, but it requires very careful planning if you use at large current.
"Classical" choke input PSUs are in tube HV sections, where current is more limited and chokes nominal current is enough large.
Felipe is novice in this area, so give him an exact plan.
I few days tried the 26 with Ale Moglia Gyrator as headphone amp, I guessed the output impedance can be enough for my Sennheiser HD600 without measurements connected directly the phone to the 6.8uF output cap, sounds tonality was very good but lacks of dynamics like you are listen to long from the sound.
So measured the output impedance giving a value of 867,2354 ohms & a damping factor of 1,38 so measurements confirmed me the need of a second stage to use as headhone amp.
So measured the output impedance giving a value of 867,2354 ohms & a damping factor of 1,38 so measurements confirmed me the need of a second stage to use as headhone amp.
I'm curious, how can the output impedance be that high, the gyrators output is very low.