Login / Register
 
Capacitor Voltage from schematics
New Reply
Subscribe
xqtion
Thread Starter
#1
21st February 2012
Old 21st February 2012
  #1
Gear addict
 
Joined: Sep 2002
Location: Los Angeles , USA
Posts: 351

Thread Starter
xqtion is offline
Capacitor Voltage from schematics

Hi fellows,

Is there a way to find out the voltage of a capacitor by looking at the schematics ?

I'm specifically looking to find out what the voltage of C29 (470pF) is in the attached schematics of my tube mic.

Can anyone shed me some light here? Thank you so much!!!
Attached Thumbnails
Capacitor Voltage from schematics-micschem.jpg  
#2
21st February 2012
Old 21st February 2012
  #2
Lives for gear
 
Joined: Sep 2004
Location: UK
Posts: 6,770

Matt Syson is offline
Hi
Finding out the maximum available supply then add say 20 percent is a good start.
You could work it out from the schematic but I would sugest it needs to be in the order of 300 Volt DC at least and a 'high quality' (low leakage) type, not ceramic.
Matt S
__________________
Matt S
www.mseaudio.co.uk
xqtion
Thread Starter
#3
21st February 2012
Old 21st February 2012
  #3
Gear addict
 
Joined: Sep 2002
Location: Los Angeles , USA
Posts: 351

Thread Starter
xqtion is offline
I have a silver mica 470pF/500V and a 470pF/630V polystryrene cap.

Would it be ok to use either ?

Thanks!!
#4
21st February 2012
Old 21st February 2012
  #4
Lives for gear
 
Joined: Sep 2004
Location: UK
Posts: 6,770

Matt Syson is offline
Hi
Yes either would work fine.I think I would go for the polystyrene but if you have the patience you could try out both and see if you can notice any difference between the 2 types. Voltage rating is fine.
Make sure your soldering work is REALLY clean as the impedances around there are vety high and any flux or maybe even sweaty fingerprints may have some impact.
Matt S
xqtion
Thread Starter
#5
21st February 2012
Old 21st February 2012
  #5
Gear addict
 
Joined: Sep 2002
Location: Los Angeles , USA
Posts: 351

Thread Starter
xqtion is offline
Thank you so much Matt!!!
#6
21st February 2012
Old 21st February 2012
  #6
Lives for gear
 
Haz-Mat-Strat's Avatar
 
Joined: Aug 2006
Location: Glenwood MD
Posts: 770

Haz-Mat-Strat is offline
The B+ voltage looks to be 185v DC. The voltage divider, 560k and 270k will drop it to 60v DC. Measure the voltage at the junction of R36 and R37, it should be around 60v DC.

You can use any capacitor over 160v dc. I like Polystyrene in this spot. You may try several values from 470pf to 1500pf to see what you like best. Silver Mica is brighter.

The configuration of C16 and C21 could be improved. C21 being an electrolytic will not have the best sound or response. Changing that capacitor to a Polypropylene film capacitor will give the mic a better sound. Try the mic with and without C16 to see what you like better.





.
__________________
Best,
Jim Jacobsen
Founder
JJ Audio


Making Music sound better, one mic at a time



Available at:

Sales and customer support:
xqtion
Thread Starter
#7
22nd February 2012
Old 22nd February 2012
  #7
Gear addict
 
Joined: Sep 2002
Location: Los Angeles , USA
Posts: 351

Thread Starter
xqtion is offline
Thank you Jim for the great advice!

I've already replaced C21 with a Panasonic polypropyrene film cap. In fact I replaced C20 to the Panasonic pps too although that probably wouldn't affect the sound.

Now I was wondering... C16 already has a Wima MKP cap, do you think it needs to be replaced for better quality cap? If so any recommendations?

Also what can I expect from changing C29 (470pF) to a higher value as you recommended to try? For example, would it increase the output level, headroom or change the frequency response of the mic?

Thank you so much!!
#8
25th February 2012
Old 25th February 2012
  #8
Lives for gear
 
Analok's Avatar
 
Joined: Jan 2011
Posts: 683

Analok is offline
I think changing this cap to a higher value would make it sound darker or less articulate if you will. On a side: Examining the attachment, I can't figure out the purpose for the 2nd half of the 12AX7: cathode, grid and plate all hit ground. What's with that??
xqtion
Thread Starter
#9
26th February 2012
Old 26th February 2012
  #9
Gear addict
 
Joined: Sep 2002
Location: Los Angeles , USA
Posts: 351

Thread Starter
xqtion is offline
Quote:
Examining the attachment, I can't figure out the purpose for the 2nd half of the 12AX7: cathode, grid and plate all hit ground. What's with that??
Acoording to Dave Thomas of AA mics, the 2nd part of the tube isn't used at all in this design and he gave me some mod options.
#10
26th February 2012
Old 26th February 2012
  #10
Lives for gear
 
Joined: Sep 2004
Location: UK
Posts: 6,770

Matt Syson is offline
Hi
The second 'half' of that valve is not being used.
It could be employed in a couple of ways, giving different 'results' if you wished.
Matt S
#11
29th February 2012
Old 29th February 2012
  #11
Lives for gear
 
Analok's Avatar
 
Joined: Jan 2011
Posts: 683

Analok is offline
Okay, thanks!
New Reply Submit Thread to Facebook Facebook  Submit Thread to Twitter Twitter  Submit Thread to LinkedIn LinkedIn  Submit Thread to Google+ Google+ 
 
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Similar Threads
Thread
Thread Starter / Forum
Replies
Jay Pemberton / Geekslutz forum
3
85db / Geekslutz forum
8
TOR / Geekslutz forum
3
coolwhip / Geekslutz forum
1

Forum Jump

SEO by vBSEO ©2011, Crawlability, Inc.