F3 Builders Thread

[Melon Head]

Hi Nelson
So are you suggesting 15 x 1000uF Elna SIlmics is definitely worth the effort?
Or can we get away with a lower capacitance eg 5000uF instead of 15000uF.

[Melon Head]

While we are waiting for Nelson to get back to us about C1.
I think we can agree that all other electrolytics on the amp should be Elna Silmics.

[flg]

Originally posted by thanh1973
Can anyone supply a spice model for LU1014D?

thanh, Send me a PM

As far as Rs go, I've been using the Caddock MK132 in critical, low power (signal path mostly) spots. I'm of the opinion that resistor distorion may have a few significant factors effecting it. Some, like the actuall material, film, foil, whatever, may not even be advertised but are significant. An important factor you can deal with is the "thermal memory distortion". That is, when in operation, you don't want the signal to be varying the power disipation greatly. Basically that boils down to selecting a component with high enough power dissapation and actual size but, also very low temp coefficient. Most bulk metal foils are the best at around 5-10ppm. In other words, the resistor value does not change as power, or temperature, varies with signal.
Just my 2 cents

[flg]

Originally posted by thanh1973
Just to clear things up the purpose of these are dc blocking capacitors is that right?
If so won't the tweeter be more vulnerable to damage by doing it this way?

Yes, they are for DC blocking. And Peter is still using them in series with the speaker for that purpose. Someone correct me if I'm sounding off the wall or something. The way he is using them he is also combining any cross-over components with the output cap to arrive at one less cap in the system. In addition, since bass signals are not going through the tweeter cap, any possible distortion from the bass should have less effect on tweeter signal.

[MRupp]

Trust me - people obviously are missing a big bet on the Elnas.

Thank you very much for your recommendation

In the capacitor tests of Cyril Bateman non-polar electrolytic capacitors showed much lower distortion compared to normal polar electrolytcs, especially whith higher bias voltages across them, so a non-polar Silmic version might potentially be even better, if only one could get those.

To my surprise, when browsing through the Silmic datasheet I found the following statement: “For bipolar capacitors, consult with us.” So it looks that they would offer bipolars. Not sure though how they will react when I call them up for my 50 units

[Nelson Pass]

Originally posted by thanh1973
Hi Nelson
So are you suggesting 15 x 1000uF Elna SIlmics is definitely worth the effort?
Or can we get away with a lower capacitance eg 5000uF instead of 15000uF.

I haven't tried it, but this being the only capacitor in the signal path,
I think it's worth the effort. The F3 has a very sweet top end, and
anything you can do to improve it is worthwhile.

[Melon Head]

Hi Nelson
Is 15000uF absolutely necessary or can we get by with something less than this value for C1?

[Melon Head]

Hi flg,
I tried emailing you about the model, but it seems you have blocked emails for your account.
You can also PM me if you want.

[Melon Head]

Hi MRupp
If that was the same article I read, then he found he could achieve even better results than bipolars by putting two polarised electrolytcs back-back (ie creating a bipolar with two polarised caps)

[Nelson Pass]

Originally posted by thanh1973
Is 15000uF absolutely necessary or can we get by with something less than this value for C1?

Of course you can just get by (if you want to). Just compute the
rolloff frequency of choice.