R Core transformers and Chokes for my power supply.

[Ianmac]

Spent last week rebuilding my power supply for my CAPS streamer.
After much work with LT and LM series regulators I could not get the unwanted transients down to a level I wanted. (Hum& noise is better than -110dbv but transient across the spectrum are proving difficult to get rid of)

I have concluded that a redesign using a Choke input filter is the way I should go and am looking for Cokes and if possible an R transformer John Swensons design, case inards photo http://uptoneaudio.com/products/js-2-linear-power-supply gives an idea as where I want to go.
Getting Chokes that are reasonably sized for higher current applications seem difficult to come by, plenty out there for the Valve amp. power supply and some for a DC Heater supply.

Anyone any idea as to UK suppliers for R cores and Chokes

many thanks
Ianmac

[killie99]

Mouser usually have a good selection of chokes, that's where i got the one for the John Swenson power supply I built.

[Arkless Electronics]

You can get R cores cheaply on ebay from China. There is precisely ZERO advantage to using them though....

[Ianmac]

One source for R cores Ive come across
http://www.vt4c.com/shop/program/main.php?cat_id=55&group_id=7
So far nothing in the UK. Trying to avoid sending to China but it may be where I have to go.

Still researching Chokes, Sowter Transformers, have a limited range and will build to order at a price.
Found and old bolt frame transformer in my workshop which looks like its good for a rebuild to a choke.
Ill have a go at a rewind to let me continue with my PSU research
Im also looking at the issues associated with using an SMPS supply with a linear regulator output. The devil will be in getting rid of the fast risetime transients.
Ian

[Chris]

I bought my R-cores through Selectronic in France. I think they are made in India. No hassle at all. One in my Hagerman step up and the other in my heater circuit. Do the job fine.

[Ali Tait]

Have you tried here, they should wind to order I think-

http://livinginthepast-audioweb.co.uk/index.php?p=xfrmrchokes

[smithie]

hi
ive used that vt4c.com site afew times over the years,no problem with them and i found them fast and efficient and good to deal with,if that was a concern or worry,saying that ,i havent used them for afew years now:)
regards
smithie

[Ianmac]

Well Im finding out the hard way that using chokes for choke input filters on high current supplies is not such a bright idea. Size, availability and cost are issues.
There are a few sites warning one that a choke to be used as an input filter has a different specification to one used as part of a capacitive filter but none give you the precise details. I assume ripple current rating and DC resistance are issues.
I have emailed Hammond re this but no reply to date.
An alternative I'm looking at is to use an LT3080 as a regulator for the control circuitry of an LT3083. The 3083 only requires about 17ma or 1.7% of load current.Hoping it will be easier to get a cleaner low current supply. A low current(100ma) choke suitable for use an input filter is available from Sowter Transformer but £104. !!
I currently have my supply working with LM 338 regs wired in pairs with one as a floating pre reg.
Ill keep plodding on with this, awaiting some LT3083's.
Ian

[peter j]

Spent last week rebuilding my power supply for my CAPS streamer.
After much work with LT and LM series regulators I could not get the unwanted transients down to a level I wanted. (Hum& noise is better than -110dbv but transient across the spectrum are proving difficult to get rid of)

I have concluded that a redesign using a Choke input filter is the way I should go and am looking for Cokes and if possible an R transformer John Swensons design, case inards photo http://uptoneaudio.com/products/js-2-linear-power-supply gives an idea as where I want to go.
Getting Chokes that are reasonably sized for higher current applications seem difficult to come by, plenty out there for the Valve amp. power supply and some for a DC Heater supply.

Anyone any idea as to UK suppliers for R cores and Chokes

many thanks
Ianmac



5mH@ 15 amps. Any good to you?.

[Ianmac]

I got a reply today from Hammond which I can apply to their range of chokes available from Mouser as mentioned above by Killie.
Hammonds reply--

My understanding is , choke input applications have higher ripple current ( AC current ) than an output inductor. Our normal design theory is 100% DC current rated plus 10 % accounted for the ripple current passing through. Remember , the DC current is above the zero axis and the ac ride on that DC level but all in one direction. We gap the core to operate in than condition.

Choke input has more ripple % current due to its application.

My recommendation is specify and inductor at the higher end of the inductance range plus specify the current at 2 X or more of the actual current load.

This will minimize the ripple current and provide enough head room at peak currents to prevent saturation of the core.

Thanks Peter, I think I now have a solution using a Hammond choke about 2H @100Ma and a LT3080 and 3083.
Ian

[sq225917]

I run a pair of Hammond 158t in the paradise phonostages that I build, be aware that they are better placed between two large psu capacitors than on the end of a capacitor filter board where they can be induced to ring. Absolutely don't place them between traffo and diodes that's a recipe for ringing.

[Ianmac]

My intention is to use the choke as a choke input filter.
I am about to build a breadboard LT 3080 supplying the control voltage to an LT3083. The choke input filter being used on the 3080 which only needs to supply 50ma max .Ill report back as to how I get on. The application notes for the LT series regulators suggest using a dc/dc converter upstream of the regulators, an area I have never ventured into as yet.
This supply was intended for use on a phono pre project Im starting and I found this on the net https://linearaudio.nl/silentswitcher Initially attracted by the specification re noise and output impedance I noted the similarity between the DC/DC regs on the LT series application notes.
I hope to get hold of a silent switcher if they become available as Im sure I would have difficulty trying to get near that noise spec even with a Jung Reg.
Amazing how starting to look at R core to see if its better than a torroid re mains noise performance and Im now looking at what is essentially an smps supply !

One interesting point however I have two Benchmark DACS, both excellent specifications. The DAC 2 betters the DAC1, The DAC 2 has an SMPS supply
Has SMPS come of age for audio use while I have my head in the sand with big trafos and regulator dissipating lots of power.?