Hi,
*Extended foil* polystyrenes, and the better non-magnetic leaded Sil micas, are both very good sonically. After many comparisons in a lot of different areas, I have found it hard to come to any overall conclusion.
Both seem to have their merits, and in some locations, one seems preferable to me, and in alternative locations, I marginally prefer the other.
Regards,
*Extended foil* polystyrenes, and the better non-magnetic leaded Sil micas, are both very good sonically. After many comparisons in a lot of different areas, I have found it hard to come to any overall conclusion.
Both seem to have their merits, and in some locations, one seems preferable to me, and in alternative locations, I marginally prefer the other.
Regards,
That's real DIY!!
One day I'll make my own resistors from old Belgium money.
But when we buy 10pF, we now it's +/- 10pF.
When we try to make it with wire wrap it's hard to measure.
Even with a good DMM as a Fluke and original Fluke leads the tolerance of the meter and leads vary too much to measure 10pF not to speak about 5pF.
Or is there a better way to perform a correct measure?
/Hugo - always has problems with meter tolerances...
One day I'll make my own resistors from old Belgium money.
But when we buy 10pF, we now it's +/- 10pF.
When we try to make it with wire wrap it's hard to measure.
Even with a good DMM as a Fluke and original Fluke leads the tolerance of the meter and leads vary too much to measure 10pF not to speak about 5pF.
Or is there a better way to perform a correct measure?
/Hugo - always has problems with meter tolerances...
Netlist said:That's real DIY!!
One day I'll make my own resistors from old Belgium money.
Well, I am not sure about resistors, but my father used to
make capacitors from the metal foil wrapped around chocolate.
But when we buy 10pF, we now it's +/- 10pF.
When we try to make it with wire wrap it's hard to measure.
Even with a good DMM as a Fluke and original Fluke leads the tolerance of the meter and leads vary too much to measure 10pF not to speak about 5pF.
Or is there a better way to perform a correct measure?
/Hugo - always has problems with meter tolerances...
I suppose you mean +/- 10%? I wouldn't like to buy a cap
that has +/- 100% tolerance.
Anyway, I think the best way is not to measure, but try to
calculate the required wire length. I don't remember the
formula for capacitance between wires, but it shouldn't be
too hard to find in some book, or on the net. You also need
to know the wire diameter, insulation thickness and the
dielectricity constant for the insulation, but I would guess that
you can get a pretty good accuracy this way.
Consider that what you are trying to do here is trim
the square wave of an Aleph by have 5 to 20 pF
in the feedback loop. Make the wire too long, say
2 inches, and cut it to trim the square wave.
Turn the amp off when you cut the wire, and dress the
ends slightly apart to avoid arcing.
pass/ - likes the teflon on the wire wrap wire.
the square wave of an Aleph by have 5 to 20 pF
in the feedback loop. Make the wire too long, say
2 inches, and cut it to trim the square wave.
Turn the amp off when you cut the wire, and dress the
ends slightly apart to avoid arcing.
pass/ - likes the teflon on the wire wrap wire.
A cap made by twisting 2 wires together that way is called a "gimmick capacitor". Trimming cap values that way has been around forever with RF stuff.
Later
BZ
Christer, you can calulate your self to death but it will be a lot faster to just twist the 2 wires together. The tighter you twist them the higher the C value will go, up to a point.
Later
BZ
Christer, you can calulate your self to death but it will be a lot faster to just twist the 2 wires together. The tighter you twist them the higher the C value will go, up to a point.
Micas and other choices
Small value capacitors such as 10pf are used to trim the very high-end frequency response, usually well above the normal hearing range. In many cases these small value capacitors are also used to improve, or control phase shift to prevent oscillation above the 1 Mhz point. Since these frequencies are mostly in the RF range (radio frequency) we should use capacitors that have very good characteristics at RF frequencies. Silver micas are one such capacitor.
RF gimmick capacitors, those made by twisting wires together, are at times useful to find initial values of the actual amount of capacitance required. As a personnel preference I would not leave them in a audio circuit permanently. A better choice would be to use a small value trimmer capacitor for this purpose. These can be left in place or replaced with the proper value fixed capacitor later if desired.
John Fassotte
Alaskan Audio
Small value capacitors such as 10pf are used to trim the very high-end frequency response, usually well above the normal hearing range. In many cases these small value capacitors are also used to improve, or control phase shift to prevent oscillation above the 1 Mhz point. Since these frequencies are mostly in the RF range (radio frequency) we should use capacitors that have very good characteristics at RF frequencies. Silver micas are one such capacitor.
RF gimmick capacitors, those made by twisting wires together, are at times useful to find initial values of the actual amount of capacitance required. As a personnel preference I would not leave them in a audio circuit permanently. A better choice would be to use a small value trimmer capacitor for this purpose. These can be left in place or replaced with the proper value fixed capacitor later if desired.
John Fassotte
Alaskan Audio
Nelson, what are you doing to me? "AAAH!"
All I wanted to try was to improve a built ACA a little, and now this.
It getting better and better, and I love it!
Thank you!
Nelson, what are you doing to me? "AAAH!"
All I wanted to try was to improve a built ACA a little, and now this.
It getting better and better, and I love it!
Thank you!
What kind of capacitor fetish is this.
Hahahahaha
This is how I did the PSU capacitors in my amp.
I call it the Beast with a Thousand Miles.
I was going to say you can get 10 pf teflon caps from Digikey, solder short non magnetic leads to them, but now their discontinued, i got a few and used them on my power amps.
You can still get LCL polystyrenes
RS Pro - 113207 - 10pF 10.0% 160 Vdc Axial Through Hole Polystyrene Film Capacitor FSC 4mm - Allied Electronics & Automation
You can still get LCL polystyrenes
RS Pro - 113207 - 10pF 10.0% 160 Vdc Axial Through Hole Polystyrene Film Capacitor FSC 4mm - Allied Electronics & Automation
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I tried the Gimmick in my very first amp for Cdom. I replaced it with a ‘real’ cap in the end because it was more compact instead of a twisted wire wafting around. But it did work, the amp was stable. I only compared Ag Mica with npo once and marginally preferred the ceramic as it was very slightly cleaner.
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