John Curl's Blowtorch preamplifier part II

[PMA]

Jacco, he was afraid of quality of a cap used in a feedthrough, so I suggested to make own with a good cap

[anatech]

Hi Pavel,
Given the values you are looking at with a feedthrough capacitor, any low K ceramic material should be fine. Talking about power supply feeds and amplifier outputs, they are low impedance circuits, so even a high K ceramic shouldn't represent any problems. Input circuits should be easy to deal with as well. Wouldn't a length of shielded RF wire act as a feedthrough capacitor the shield was grounded at the point of entry through the casing?

I have used these off and on, usually when dealing with higher frequency circuits. RF amplifiers and switching power supplies certainly rate here.

Hi stoolpigeon, Demian,
A new thread for this would be the best. It would be a shame to confuse two designers and their ideas, and Demian deserves a thread of his own to discuss his ideas, if desired.

-Chris

[bear]

Originally posted by Magura


It's actually not all that to shield an inductor. With some help from Dimitri, I made a 5mH shielded inductor for a power amp PSU, some time ago.

It's a mix of ferritic stainless steel and copper shield.

Magura

Whoa! High "sex" value to those slick lookin' shields!!

by "ferritic" do you mean non-magnetic?

_-_-bear


Edit: oh, where are we on internal PS vs. external PS, especially WRT that choke shielding issue? Do we want only DC sent through the embilical connecting cord, and what about ground if we go external??

[PMA]

Chris, I use professional HF feedthroughs, they are also a part of my current preamp design, to clean DC PSU output wires thru an Al wall.

[Magura]

Originally posted by 1audio


Did you characterize the effect on the inductor of shielding it? You would see the inductance change and it would have a saturation point as well. When saturated the shield effectively vanishes so you need to be sure you stay below that limit. Also it will affect the HF performance but the coil pictured will not have the best HF performance anyway.

The inductance stayed the same, due to the mix of copper and ferrittic stainless steel.

I have not had a need to push it past 10A, till that point no saturation occurred.

Magura

[Magura]

Originally posted by bear


Whoa! High "sex" value to those slick lookin' shields!!

by "ferritic" do you mean non-magnetic?

_-_-bear

Thanks Bear.

Ferrittic stainless steel is the type that is magnetic. It's rather rarely used, but for this it made sense.


Magura

[bear]

Originally posted by nicoch46
yes ,I find no other explanation: whay if I swap on borbely design caps or diode the sound change a lot ?

ok cooking parts is not like a design....shunt can be audio psu

This is an interesting question, but this is the Blowtorch thread, not the Borbely thread. Erno has some interesting design ideas, and it deserves its own thread, imho. You might want to start a thread on Borbely designs, post the schematic you are referring to, along with a jpeg of your implementation and a block diagram of your wiring/ground scheme??

_-_-bear

[PMA]

You will have almost nothing to discuss here, then, maybe cars and wines.

[bear]

Originally posted by Magura


Thanks Bear.

Ferrittic stainless steel is the type that is magnetic. It's rather rarely used, but for this it made sense.


Magura

Wondering if the alloy is one of the ones with a high hardness - making it difficult to machine??

_-_-bear

[jacco vermeulen]

Epcos B85321, metallized polyprop foil capacitors.
Manufactured in values up to 4.7uF, and subsequent 6''x2'' sizes.

(= what i use to go through 10mm Alu walls)