|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
71.75.10.155
Actually, I understand how the circuit works, but I'm curious about the coupling cap values.The coupling cap feeding the upper EL84 in each channel (C104 and 204) are .0015uF, whereas the cap feeding the lower EL84 (C106 and 206) are .047uF, more what I would expect.
Why the difference?
Edit: the schematic is a Magnavox 9302-00 from a console stereo.
Edits: 04/24/21Follow Ups:
I tried that type of phase inverter back in the 90's and did not care for it.
nt
Is it possible to have the component list to undertand the * on some value.
I have another idea around
Walter
You have only to become a DIY with simulations.
Omnes feriunt, ultima necat.
The upper (inverting) half of the paraphase is being used to contour the frequency response. The smallish coupling cap and the various caps to ground limit response at both ends of the spectrum. The lower half of the paraphase is simply a broadband stage that provides a matching 360 degree shifted (non-inverted) signal.
--------------------------
Buy Chinese. Bury freedom.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 04/24/21
...R113 and R114 form a voltage divider whose reduction ratio more-or-less matches the gain of the lower section of the 6EU7. Effective gain is a function of resistor values and tube gain. Divider values are chosen to produce an effective gain of approx -1. A true floating paraphase employs effectively nearly 100% inverse feedback for the lower section so the gain here is also approx -1.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
nt
.
Have Fun and Enjoy the Music
"Still Working the Problem"
The loads on the inverter plates (i.e. the EL84 grid resistors) are also different. It's not a symmetrical inverter, so there's no reason to expect symmetrical component values.
I see that the grid resistors are different.
I don't know how to calculate this, but it seems that .0015 into a 509K load would roll off higher then .047 into 220K?
Yes. 208Hz vs. 15Hz
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
The inverted (second) stage is in series with the first stage so it has both rolloffs; the second rolloff is much lower in frequency so it has minimal difference.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: