RegisterRegister
Log in to check your private messagesLog in to check your private messages
Log inLog in
FAQ  -  SEARCH  -  MEMBERS  -  FAVORITES  -  PROFILE
coupling caps

 
Post new topic   Reply to topic   printer-friendly view    Tape Op Message Board Forum Index -> DIY Gear
View previous topic :: View next topic  
Author Message
I'm Painting Again
zen recordist


Joined: 07 May 2003
Posts: 6886
Location: New York, New York

PostPosted: Sat Apr 01, 2017 7:57 am    Post subject: coupling caps Reply with quote

is there an easy way to ID them on a schematic ?

this is in tangent to my racked audix 35102 channels thread if you need a reference on what problems I'm trying my hand at solving..

the circuit in question

http://www.twin-x.com/groupdiy/albums/userpics/35102.jpg

http://www.twin-x.com/groupdiy/albums/userpics/35102amps~0.jpg
Back to top
View user's profile Send private message Visit poster's website
Drone
buyin' gear


Joined: 18 Dec 2009
Posts: 595
Location: Uranus

PostPosted: Sat Apr 01, 2017 10:35 am    Post subject: Re: coupling caps Reply with quote

Coupling caps are the ones that join signal stages together. The signal passes through them.

De-coupling caps are the ones on the power line, or sometimes signal lines to ground, basically they couple the unwanted signal to death.

So in that diagram, things like C191 and C252 are coupling caps.
_________________
The previous statement is from a guy who records his own, and other projects for fun. No money is made.
Back to top
View user's profile Send private message
I'm Painting Again
zen recordist


Joined: 07 May 2003
Posts: 6886
Location: New York, New York

PostPosted: Sat Apr 01, 2017 2:56 pm    Post subject: Re: coupling caps Reply with quote

would they be anything outside of the blocks?

or only where two or more blocks are connected?

the problem is probably outside the EQ portion since it happens when the EQ is switched out

de-coupling ones filter the DC ?

what are examples of those in this diagram ?
Back to top
View user's profile Send private message Visit poster's website
The Scum
resurrected


Joined: 04 Jul 2003
Posts: 2399
Location: Denver, CO

PostPosted: Sun Apr 02, 2017 4:31 pm    Post subject: Re: coupling caps Reply with quote

So it's a little more subtle than it seems you're thinking.

C191 and C252 are actually elements of the high pass filter...see the little synopsis circuits at the bottom of those sections.

But technically, AC-coupling caps are high pass filters themselves. DC is considered to be a frequency of 0 Hz. To keep DC from passing between stages of a circuit, the stages get capacitors between them, forming a series of highpass filters...typically just outside of the audio band...some designs might target 20 Hz, better designs will target 2 Hz or even lower.

Cuircuits from the era of that Audix design use a single 24V power rail...so the audio signal needs to ride on a ~12V bias, and that bias needs to be added on as signal enters a stage, and stripped off as it leaves.

A bunch of the components in those amp stages are there to create the bias voltage, stabilize it, or remove it when it's done. More modern circuits use bipolar power supplies, and keep the signal centered around 0V, taking fewer components because the bias coupling & decoupling isn't required.

So the coupling caps are usually at the input or output nodes of the amps, but it can take some careful analysis to identify every cap in the circuit that could be clobbering the low end...for instance, C13 and C14 are possible culprits, though they're nested inside the amp stage.
_________________
"What fer?"
"Cat fur, to make kitten britches."
Back to top
View user's profile Send private message Visit poster's website
I'm Painting Again
zen recordist


Joined: 07 May 2003
Posts: 6886
Location: New York, New York

PostPosted: Mon Apr 03, 2017 12:36 pm    Post subject: Re: coupling caps Reply with quote

i kill u

fascinating and frustrating to be learning about this stuff

thanks for pitching in to help out y'all

much appreciated
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic   printer-friendly view    Tape Op Message Board Forum Index -> DIY Gear All times are GMT - 4 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum