Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Jonas on March 14, 2022, 02:34:13 pm

Title: Enclosed VS Open Frame choke
Post by: Jonas on March 14, 2022, 02:34:13 pm
I have a question regarding choke construction; open frame vs enclosed.  (open frame Hammond 153-159 series and enclosed choke Hammond 193 series)

I heard years ago that using an enclosed choke is a bad idea, but I cannot remember why or if even true?  Your thoughts?
Title: Re: Enclosed VS Open Frame choke
Post by: sluckey on March 14, 2022, 03:12:27 pm
Not true.
Title: Re: Enclosed VS Open Frame choke
Post by: AmberB on March 14, 2022, 08:45:57 pm
Does it make any functional difference if the choke is open or enclosed?
Title: Re: Enclosed VS Open Frame choke
Post by: tubeswell on March 14, 2022, 10:34:32 pm
Quote from: AmberB on March 14, 2022, 08:45:57 pm
Does it make any functional difference if the choke is open or enclosed?


Depends whether you're a 'function' or 'form' person LoL. One type has bell covers, the other type doesn't.
Title: Re: Enclosed VS Open Frame choke
Post by: Jonas on March 15, 2022, 08:53:00 am
thanks everyone!
Title: Re: Enclosed VS Open Frame choke
Post by: valvetones on March 16, 2022, 07:48:12 pm
The chokes with endbells are fully shielded yes?
The type with no end bells would then possibly mess with the magnetic field of the power and output transformer perhaps? Just guessing here.

Thinking maybe it would couple the power supply fields with the output transformer fields if all three pieces of iron are in close proximity.

Yes ? No? Maybe so?
Title: Re: Enclosed VS Open Frame choke
Post by: tubeswell on March 16, 2022, 09:18:06 pm
Quote from: valvetones on March 16, 2022, 07:48:12 pm
The chokes with endbells are fully shielded yes?
The type with no end bells would then possibly mess with the magnetic field of the power and output transformer perhaps? Just guessing here.

Thinking maybe it would couple the power supply fields with the output transformer fields if all three pieces of iron are in close proximity.

Yes ? No? Maybe so?


No difference in EM fields - the end-bells are purely for looks. The EM-flux density extends out into the space outside the laminations, and this happens whether or not you have end bells.