DC blocking capacitors strange values!

[kkrafs]

I noticed that in several limiters such as 444, 436 M5136, etc there
is quite a variation on the value of the DC blocking capacitiors.

The first stage might have 100nF, wich pushes the HP corner up a
bit, then between second and third stage we find 25nF, wich put
the HP corner high! (capacitor coupled units)

Now, i find this a bit peculiar or have i missed something?

Another peculiar thing are that several designs uses 100nF
as DC blockers to the rectifying stage no wonder that tube
limiters has a special responce to signals!

Why these values?

For instance comparing this to mic tube preamps i found
eg Neuman uses often 500nF, a significat difference!

I asume that tubes have a quite flat frequency responce! :roll:
For equations to typical designs i use:
http://www.aikenamps.com/Equations.htm

In the case of UA175 i get by above a HP Cf of 419hz
(using mouse on PC calculator wich always hassles!! :twisted:

Wich i find a rather high HP cut point !

Reg
Kkrafs

 

[CJ]

I do not understand the post very well, but usually I can not hear a difference in bypass caps unless their difference is on the order or 10, that is, I might hear the diff between a 0.1 and a 0.01, but not always.

I think it is impedance related.

If the cap is in a place where it has an effect on attack and delay, then that's another story.

 

[gyraf]

Many vari-mu limiters were heavily bandwidth-limited towards their low-end to control DC breakthrough or "thumping". Look e.g. at the recently discussed Maxson CA1589 unit:

http://www.groupdiy.com/index.php?topic=7114

Jakob E.

 

[kkrafs]

[quote author="gyraf"]Many vari-mu limiters were heavily bandwidth-limited towards their low-end to control DC breakthrough or "thumping". Look e.g. at the recently discussed Maxson CA1589 unit:

http://www.groupdiy.com/index.php?topic=7114

Jakob E.[/quote]

Just after i posted i started to suspec that too (cv pumping).
Thanks for the link to previous discussion, i wonder how i could
missed it!!

Kkrafs