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Starting to put a parts list together for building the 91A amp and I am going to need 10H and 5H filter chokes for the power supply . First question is do I have to use the max mA that psduII shows for the choke rating or should I use the mean?
Then, what is your favorite brand of cost effective filter choke?
Follow Ups:
Hey Vinnie,
Thought I'd chime in late...
I have used the Hammond offering for well over a decade mainly because I've been able to achieve my goals using them after some experience.
I typically de-rate them 100% percent to ensure lower DCR. With this said, they have been used for my prototypes.
One day I'll pay for the multi-winding C-core or R-core animals and see if there is ROI. I'm a Lundahl fan for signal service, so I will probably get around to trying their PS chokes. You have loads of choices. Implemented with some thought, most manufacture offerings (with in reason) will do the job.
Stuben
Lots of good suggestions to check out. I appreciate it!
Vinnie
I like the One Electron chokes.
They are also plate chokes so
they perform better than most.
They also have dual windings
for more flexible use.
DanL
But I wouldn't spend the money for a WE 91A type amp. It's not really a hi-res design, generic parts would suffice.
My power supplies using inexpensive Hammond chokes are used in a CLC filters- no hum issues. A choke input may need a more heavy duty choke. See Al Noakes post.
Edits: 12/11/14
Lundahl: two coils on a C core gives you more options. Can be connected series for more inductance or parallel for more current. Also possible is a common mode connection that I use where one coil is in series with the positive leg on the bridge and one is in series with the negative leg. I experience blacker backgrounds with this type of choke input supply.
The Lundahls wired in common mode are my favorite.
It MUST be 20 Ohms DCR or less. You take it from there !!!In 2014, I've arrived, ( since 1982 when I first experimented with ALL of this ), at under ten Ohms, under 2.2 HY, and under 2.2 pounds in size.
'Also arrived at L1/C1/L2/C2 as the BEST topology to the finals.
Unbeatable, the best there ever is and was in my experience. YMMV.
Have fun learning !!
Jeff Medwin
Edits: 12/11/14
You are over-generalising but I agree regarding LCLC supplies . What you describe is not a 'one size fits all' . If you understand what a choke does in term of impedence , then you would realise that low DCR is a nice parameter to have but not a necessity . Besides , you use filamentary rectification which is where the majority of losses occur in your power supplies
Merry Christmas :)
Al
"It MUST be 20 Ohms DCR or less."
The filter cap *after* the choke is responsible for providing the low Z path to ground. The resistance of the choke must only be sufficiently low so as not to create voltage sag under varying loads. If the average load doesn't vary, as in the case of a Class A output stage, the choke can be thousands of ohms with no ill effect.
--------------------------
Buy Chinese. Bury freedom.
See OP
Hammond chokes are pretty much rated for cap input.
Look for examples of what other people have used. I know Hammond has a 5H in the 50 ohm range, but its tough to say weather or not it will buzz.
A small cap, up to about .68uf in front of the choke input will help alleviate buzz... once the voltage starts to climb though, you're running a cap input...
I asked Hammond (here in the great white north) and they said their chokes are good for either choke or cap input. They pointed out that their spec sheets show both options and they have been spec'd that way. I'll take them at their word as I've used them in both ways with no issue.
Hammond chokes (the clamp-mount ones) have the advantage of being cheap and readily available . The inductance tends to fall off as current increases . DCR also seems high and the cores are nothing special . The same applies to Triad . I have used both Hammond and Triad , both get the job done . You get what you pay for . I don't know what the more pricey Hammonds are like but the cores are still standard lams by the looks of things . I now get my chokes custom built in batches of at least 10 with M6 lams and over-rate by about 50% over modelled peak current . I would recommend inmates here doing the same and splitting a batch in a group buy .
Al
I've found Hammond chokes don't carry true to their spec'd current and core saturation occurs below their current rating.
I too have gone to custom wound chokes with M6 lams....you do get what you pay for.
Hammonds are more intended for standard capacitor input usage , purely as smoothing chokes . However , I have used their 660mH 750mA (159Y?) chokes as cathode loads in an SE OTL amp and got good results .
Al
Look at the total demand downstream of the choke to determine the minimum rating. If you have a 100mA going though your output tube, 20 through the drivers, a 5mA bleeder resistor and some winding losses in the output transformer, that channel would need a minimum of 130mA.
Now, running a choke rated for 130mA at 130mA is almost guarantee of hum from the choke itself. If the choke was feeding 2 channels, that is 260Ma minimum rating. I have found that 50% above minimum or more has the best shot at making the choke quiet.
See the link below to Henry Pasternack's post on chokes.
For me, if the choke has the inductance and is quiet, it will work. "Low DCR" chokes simply mean they are either non-critical (very low inductance) or massively overrated for current.
Maybe not what you need, but I am getting custom winds from a local guy - Lucas at Black Art Audio. Not cheap, but excellent quality 7Hy/10 Ohm or 1Hy/2 Ohm C-cores can't be... still, they are more cost-effective than purchasing Lundahl here down under.
I guess my suggestion is to check out custom winds; you might be able to get better than what you think for the $.
Good luck.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki
I spec the choke HY value and use the lowest DCR Hammond choke I can find in their product line and load it approximately 65-75% of rated capacity to ensure Lcit.
Hammonds chokes are inexpensive.
I like Lundahl , i use them and sell them. quality is second to non and price is very competitive.
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