|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
63.246.183.22
In Reply to: RE: Purpose of these Caps? posted by coffee-phil on August 28, 2016 at 00:05:50
Using the caps to extend higher frequencies seems plausible. However, the caps are polarized, possibly electrolytics, and that implies a largish value. The Cary schematic posted above by Chip647 seems to use the same arrangement, and that transformer is bridged with approximately 2uF. Doesn't 2uF seem like a lot of capacitance just to extend the highs? The transformer is only driving a 220K load (plus the grid). Too bad the Fisher schematic doesn't include values.
--------------------------
Buy Chinese. Bury freedom.
Follow Ups:
I didn't rebuild these yet but you can see a 20uf at 150v is the value of the cap and it's polarzed.
"
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
In the Fisher 50A, that uses that same driver circuit, the caps are 20uf.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/28/16
20uF means the caps aren't being used only to pass high frequencies. Large caps will shunt all signal across the transformer, effectively placing the primary and secondary in parallel. I don't know what the inductance of the windings is, but this looks awful in SPICE. A huge upward and downward spike are created in the response on either side of resonance.
--------------------------
Buy Chinese. Bury freedom.
I think your choice of a coupling factor of 0.9 isn't very realistic and if you go for the ideal factor of 1 that issue goes away. You also need to include the coil resistances and adding 200 ohms to each coil in addition to making the coupling factor 0.99 has things appearing much better. The sim now behaves much more closely to what happens in the real world.
dave
I never use 1.0 coupling, but you're correct about the coil resistance. I was in a hurry and forgot. Even only 200 ohms in each winding is sufficient to smooth it out, and raising the source R to 600 ohms further flattens the plot. My mistake, thanks for the correction. My earlier plot and comments directly above should be totally ignored.
--------------------------
Buy Chinese. Bury freedom.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: