Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on November 07, 2010, 06:10:30 am

Title: A new question about PT & OT - What happen using Ferrite Cores ?
Post by: kagliostro on November 07, 2010, 06:10:30 am

Yesterday I was to a Hamfest

at the flea market  I noticed some cores for transformers in ferrite

what will happen building PT and OT with this particular material ??

Very curious about

have you some news about ?

Thanks

Kagliostro

Title: Re: A new question about PT & OT - What happen using Ferrite Cores ?
Post by: FYL on November 07, 2010, 06:37:18 am

Ferrite cores are mainly used for high frequency applications (HF by audio standards, > 20 KHz).

Title: Re: A new question about PT & OT - What happen using Ferrite Cores ?
Post by: kagliostro on November 07, 2010, 07:48:46 am

Hi FYL

Thanks

Ok they are used mainly for High Frequency applications

But what can we aspect

in the use for PT at 50 / 60 Hz

or as OT in guitar amp ?

Assuming the use in an OT

this OT will have some "special features" 

as large frequency response ?

Kagliostro

Title: Re: A new question about PT & OT - What happen using Ferrite Cores ?
Post by: FYL on November 07, 2010, 08:00:50 am

Quote

But what can we aspect
in the use for PT at 50 / 60 Hz

NiZn ferrites show poor permeability, typically below 800, making them very poor candidates for 50/60 Hz ops. Good old steel lams are much better - and cheaper too.

Quote

Assuming the use in an OT

Ditto. Poor LF capabilities.

Title: Re: A new question about PT & OT - What happen using Ferrite Cores ?
Post by: kagliostro on November 07, 2010, 10:20:43 am

thanks again  :smiley:

Kagliostro

Title: Re: A new question about PT & OT - What happen using Ferrite Cores ?
Post by: PRR on November 08, 2010, 12:34:12 am

Thin iron has large losses at and above the top of the audio band.

Powdered iron has low losses into the radio bands, but 1/100th the inductance of thin iron, meaning a VERY large transformer.

Ferrites give more inductance than old powdered iron, but still not enough to be very practical at low audio frequencies.

Iron (sliced thin and cut with Silicon) gives the most energy storage per pound and per dollar. That makes it the best material for low frequencies.

Some newer stuff, not iron and not ferrite, amorphous, gives inductance and energy storage within sight of iron. Some very rich hi-fi hobbyists use it.

Title: Re: A new question about PT & OT - What happen using Ferrite Cores ?
Post by: kagliostro on November 08, 2010, 02:00:55 am

Hi PRR

Thanks also to you

your infos has furthermore clarified the matter  :smiley:

Kagliostro