Simple SE choke

[ChrisR1983]

Hi

Does anyone know what part code to use if I want to put wire in a Hammond choke into an sse?

Thanks

Chris

 

[rknize]

Do you want the Hammond part number? 193J is what I've used. 193H may also be suitable.

 

[ChrisR1983]

Perfect, thanks

 

[ChrisR1983]

Anyone used 159q? Will that work?

 

[Ty_Bower]

Anyone used 159q?

I did. Here's my parts list:
http://www.diyaudio.com/forums/tubelab/125439-another-simple-se-builder.html#post1591160

I've been pleased with the way it turned out.

 

[rknize]

Going with a bigger choke won't hurt, as long as your chassis and budget allows. Because it has such a high current capability, it has a fairly low DCR (53 ohms). Not a bad thing, but it will raise your B+ voltage some. That's a big choke.

 

[zman01]

Newbie question on VDC rating

I recall a post by George stating a choke rated for 5-10 Henry, 150mA and 100 Ohms would work. This is a Transcendar unit I found:

Inductors - Transcendar Audio Transformers
Part Number: TT-010-CH
10 Henry, 200 mA, DC Resistance: 100 ohms

However do not see any VDC rating - is this value important?

Thanks,
Zia

 

[Davec113]

I recall a post by George stating a choke rated for 5-10 Henry, 150mA and 100 Ohms would work. This is a Transcendar unit I found:

Inductors - Transcendar Audio Transformers
Part Number: TT-010-CH
10 Henry, 200 mA, DC Resistance: 100 ohms

However do not see any VDC rating - is this value important?

Thanks,
Zia

If you have 150 mA and 100R, you get 15V across the choke from Ohm's law, so I don't think it's going to matter much....

 

[Ty_Bower]

For power supply filtering chokes, the voltage rating is important. You aren't concerned so much about the voltage dropped across the choke itself, but rather the potential between the winding and the chassis.

Your amplifier's chassis MUST be at zero potential (ground), otherwise you're gonna get zapped every time you touch it. The choke's winding may see peaks of 530 volts, assuming you are using a popular 750VCT power transformer on your amp. It is critical that the insulation rating of the magnet wire used for the winding can withstand this potential! I believe it is common practice to hi-pot test the chokes at values of 1500VDC (typical 3x safety factor), though I have seen many chokes that only claim a 500V rating.

I would expect that if Gery is selling these as filter chokes, he is using the same quality magnet wire as what goes into his power and output transformers. Perhaps it would be prudent to contact him directly via email and inquire.

 

[zman01]

Ty_Bower,

I came across one from Edcor:

EDCOR - CXC100-7H-150mA

I am considering Edcor as they are on my shortlist for a power transformer also. Again no VDC rating given. I wrote to Edcor and they responded saying current rating is for 2A and 1000 VRMS.

 

[zman01]

Working voltage vs VDC

Using Google I came across a couple of links where it says that insulation test voltage is 2 x working voltage + 1000 volts - one of these from diyAudio:

Post #7 on this diyAudio thread: http://www.diyaudio.com/forums/tubes-valves/200699-813-amp-old-choke.html

I am not sure if this is case for all chokes. A couple of other documents indiciated that VDC should be 1.4 times VRMS. Again, the Edcor choke on my shortlist is rated for working voltage of 1000 VRMS according to an e-mail from Edcor.

The Edcor power transformer I have in mind is this one: EDCOR - XPWR002-240, which is 720V rated (360-0-360).

 

[acceler8]

I asked Transcendar this very question about the TT-010-CH. Here is their response:

"Hello,

I don't normally rate inductors for a voltage.
They are rated for current and inductance.
However, I do test the insulation of each inductor to withstand 3000 volts DC.

Thanks,
Gery"

I purchased this unit, and have it in place on my 300B Tubelab SE.

 

[zman01]

Good info acceler8, thank you.

I have asked Edcor the same question.

Does Transcendar make power transformers?

 

[zman01]

Edcor reply on choke

Edcor has got back - the transformer has a maximum DC current rating of 200mA and the insulation testing is 1000 volts DC to frame or end bell.

1000 VDC is lower than the Transcendar unit, but should be ok I guess, as lot of Hammond chokes being used are rated for less.