F3 Builders Thread

[MRupp]

Hi thanh

Bateman's results are somewhat mixed, if you compare installment 5 (1uf caps tested at 1kHz) with that in installment 6 (100uF tested at 100 Hz). I think this varies a lot with frequency, package size, and individual brands. Generally the non-polar have less than half the distortion of the polar. The back-to-back polars may be better and could be worth a try, except that you need 4 times the capacitance and overall this looks somewhat “unelegant”.

Btw., another area affecting cap quality might be microphonics, and the Silmics should be very good in this respect, so overall the non-polar Silmic looks like a very attractive solution to me. Again, the question is how much of a difference does it make in the end.

P.S. I bought a local brand of non-polar caps (Frolyt) that I wanted to compare to the normal Silmics, but it might be some time before I get to do a test.

[Melon Head]

In case anyone would like the LTSpice schematic here it is.
The funny thing is I couldn't get the desired votage at the drain of the mosfet using the values from the service manual (I think it is meant to be 21V or 23V). I had to tweak some resistor values. It's not perfect but pretty close.

[Melon Head]

I did a frequecy response (LTSpice) using 1000uF instead of 15000uF. To me (don't trust a word I say) there doesn't seem to be an issue. There is a peak (small hump) at 1Hz which falls quickly, but other than that I can't see a problem using 1000uF instead of 15000uF.
Anyway have a look at the attachment

[flg]

thanh, I have found that "adjusting" the model Vth lower and Beta higher, more closely approximates the devices I have and the work published by Nelson.
I've been trying to find the time to actually measure a group of devices and "tweak" the model with the help of the "guru's" I work with. Just havent got there yet... ... ...

[Melon Head]

Thanks flg.
I will try adjusting the same parameters, and look at the effect.

[04dgmsilv]

I don't have any equipment to measure the output, but when I built my F3 with Peter's boards I used a BG N 1000/50 as my output cap (pricey, yes), but it sounds great with my Druids. The Druids are supposed to present a 12 ohm load and naturally roll off at 40-50 Hz, so my quick calc said this would be fine. Moral of the story, seeing as it's DIY, tailor it to your speakers as best you can.

[Melon Head]

Well I think that has confirmed it for me.
I will be using a 1000uF Elna Silmic in this location, unless someone else has a reason for not using 1000uF.

[Tea-Bag]

Originally posted by Peter Daniel
If I can suggest something for multidriver speakers, is to split the output caps between drivers and use whatever is needed only.

For instance, in my particular setup, I'm using 6.8uF Siemes MKV in tweeter network (1st order filter) and BG N 330/100 with the midrange driver (again first order filter only). No need for other big caps. If you have a woofer, then you can put 10,000uF cap there too, but it could be separated from mid/high output.

Peter,all
this sounds like an interesting concept if your talking about using both the 330uf and the 6.8uf out of the same amp.

I am not sure how your wiring it however if this is the case, if they are paralled as Nelson does it, then taking multi-taps off the + side of cap seems to make no difference.

If your using a different layout, I would like to know what it is.

I assume that C1 can only be one value, and that value determines the low filter frequency.

I would not mind some advice on how to calculate this. I am considering using it to run at 200 or 300hz on up..

Mike

[Tea-Bag]

I think I may have thought this through a little better. forgot first order xo is cap.

C1 area - would look something like this,

+woofer - +mid - +tweet-


-----(neg 10,000uf+)---(-)330uf(+)---(-)6.8uf (+)---100ohm R10)--
|
|
R9

Maybe? Do-able?

[Zen Mod]

Originally posted by Tea-Bag
I think.....