inductor shopping

[jhaible]

Allright then, I've made measurements on the circuit I had proposed (with OEP transformer and TOKO inductors), and it does *not* work.

The impedance transformation sort of works, i.e. I get the right resonance frequency and the right impedance. But I also get unwanted low impedance at the low end (where the transformer's own inductance isn't enough) and at the high end (where the transformer's capacitance creates a bypass path).

Bottom line is: transformation of a series resonance circuit doesn't work (unless you have a really good trafo maybe). The only way to use low inductance values would be transforming the whole signal down (trafo with resistive load), then do the filtering low-impedance (a la pultec etc), and then buffer it and amplify of transform it up again.

Too bad that the shortcut of just transforming the resonator is not - would have been too good to be true!

JH.

 

[jhaible]

Oh and I guess the low end problem could possibly be solved by putting the capacitors to the high impedance side (basically just connecting L and R to the low impedance side), but with the high frequency problem remaining, it's not really worth a try.

JH.

 

[Guest]

Thanks for looking at this idea. It is important to examin ideas just to see what works. Too bad this one didn't but lots of yours sure have.

 

[Samuel Groner]

The trick is to not get greedy and try to order too many samples;

What's "not too many"? Five or twenty?

Is the Wilco ITS-VM a good choice? Looks lovely with the shielding...
Samuel

 

[jhaible]

[quote author="thomasholley"]Thanks for looking at this idea. It is important to examin ideas just to see what works. Too bad this one didn't but lots of yours sure have.[/quote]

No problem. The failure came just in time to give me an excuse to lay that Neve channel aside: UTC interstage tramsformer from ebay arrived, so I can finally start my UA175 variable mu experiments.

I may pick up that Neve stuff later, and either buy the Sowter inductor together with the single ended output transformer that I need anyway. Or I may try winding inductors myself. Maybe.

Just curious: For winding my own inductors, are the Ferrites with high AL, like T38 or N30 any good for audio?

(For instance www.rs-components.de Number 212-6110 or 212-6176)

I have the impression that laminated iron (or all kinds of alloys) are generally prefered for audio. Is this so, and then why?

JH.

 

[Guest]

I know several people used ferite cores for winding their own inductors for various EQ circuits. All I have read indicate success, especially with toroid cores. I got some inexpensive toroids and wound inductors for a Pultec type EQ but have not had the chance to put that project on the bench yet. They test well though as long as you keep the windings tight against the core.

 

[NewYorkDave]

God bless you for spelling "toroid" correctly.

I thought I was gonna scream if I saw "torroid" one more time.

:guinness:

 

[Marik]

[quote author="NewYorkDave"]God bless you for spelling "toroid" correctly.

I thought I was gonna scream if I saw "torroid" one more time.
:guinness: [/quote]

Thank you NYDave for pointing it out. I was not sure myself the spelling, so here it is...

From Oxford English Dictionary:

Toroi`dal, a. Geom. [f. L. Tor-us+ -oidal.] Resembling or pertaining to a torus.

Torus....

4. Geom. A surface or solid generated by the revolution of a circle or other conic about any axis; e.g. a solid ring of circular or elliptic section.

:thumb: :thumb: :thumb:

 

[CJ]

so is it hemrroid or hemroid?
what do you call a male roid?
a him-roid!
:razz:

 

[peter purpose]

In London we call em 'Farmer Giles'.. :green:

 

[CJ]

Ah, now I remember! Cockney for "Piles"
So is that what the Moody's are talking about?
Face piles of trials with smiles, it riles them to believe, that you percieve,
the web they weave, and keep on thinking free..
Maybe not.
Mike Pinder lives right down the street. well, maybe a little further, Grass Valley,CA.