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Op Amp Labs Transformers



 
 
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  #11  
Old March 10th 18, 09:38 PM posted to rec.audio.pro
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Posts: 331
Default Op Amp Labs Transformers

On Sunday, March 4, 2018 at 7:49:09 PM UTC-5, Phil Allison wrote:
> wrote:
>
> --------------------------
>
> >
> > >
> > > I'm particularly interested in how badly they ring. What causes an audio
> > > transformer to ring?

> >
> >
> > 60Hz transformers hum,
> >

>
> ** A lot of force comes from the 60Hz supply acting on anything magnetic with a bunch of wire wound around it. This is single, low frequency, forced vibration, not resonance.


You know, in AC solenoids a shorting ring is beneficial to keep 60 Hz buzzing to a minimum, as the shorting ring provides a CEMF!!!!


Jack

>
>
> > so at the right audio resonant frequency,
> > I guess the core could resonate and ring, physically!!

>
> ** The sort of ringing being referred to here happens at high audio and supersonic frequencies - needs test gear to see.
>
> Folk fuss about it cos it indicates non flat response.
>
>
> ..... Phil


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  #12  
Old March 11th 18, 02:30 AM posted to rec.audio.pro
Phil Allison[_4_]
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Posts: 329
Default Op Amp Labs Transformers

wrote:


--------------------------
> >
> >
> > > >
> > > > I'm particularly interested in how badly they ring.
> > > > What causes an audio
> > > > transformer to ring?
> > >
> > >
> > > 60Hz transformers hum,
> > >

> >
> > ** A lot of force comes from the 60Hz supply acting on anything
> > magnetic with a bunch of wire wound around it. This is single,
> > low frequency, forced vibration, not resonance.

>
>
> You know, in AC solenoids a shorting ring is beneficial to keep
> 60 Hz buzzing to a minimum, as the shorting ring provides a CEMF!!!!
>


** However, solenoids and relays have moving parts - transformers do not, so are normally bolted up tight and run silent.

Had a Chinese made guitar amp here that would suddenly made a loud hum if laid over on its back, standing upright it was OK.

The four bolts holding the power transformer laminations together were barely finger tight. Soon fixed.


..... Phil






  #13  
Old March 13th 18, 02:46 PM posted to rec.audio.pro
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Posts: 331
Default Op Amp Labs Transformers

On Saturday, March 10, 2018 at 9:30:43 PM UTC-5, Phil Allison wrote:
> wrote:
>
>
> --------------------------
> > >
> > >
> > > > >
> > > > > I'm particularly interested in how badly they ring.
> > > > > What causes an audio
> > > > > transformer to ring?
> > > >
> > > >
> > > > 60Hz transformers hum,
> > > >
> > >
> > > ** A lot of force comes from the 60Hz supply acting on anything
> > > magnetic with a bunch of wire wound around it. This is single,
> > > low frequency, forced vibration, not resonance.

> >
> >
> > You know, in AC solenoids a shorting ring is beneficial to keep
> > 60 Hz buzzing to a minimum, as the shorting ring provides a CEMF!!!!
> >

>
> ** However, solenoids and relays have moving parts - transformers do not, so are normally bolted up tight and run silent.
>
> Had a Chinese made guitar amp here that would suddenly made a loud hum if laid over on its back, standing upright it was OK.
>
> The four bolts holding the power transformer laminations together were barely finger tight. Soon fixed.


Good deal!

With scraplesss laminations, some xfmr cores aren't interleaved (laminations), but a butt (E & I) stack (Shell type), then the joint is welded.

Working with CVRs (Constant Voltage Regulators) where input can vary +/- 15% but output can only vary +/- 2% (generally used for large tube filaments), were a pain to adjust. Some got out the door out of spec, they were totally varnished. Typically, you remove lamination's from center leg to adjust output voltage, but no way to do it when totally varnished. I suggested to "drill" out the center leg on a drill press while testing!

Jack
>
>
> .... Phil


 




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