Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Two Chassis Preamp -- Capacitor Question
Two Chassis Preamp -- Capacitor Question
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 9th March 2006, 12:18 PM   #1
SRMcGee is offline SRMcGee  United States
diyAudio Member
SRMcGee's Avatar
Join Date: May 2004
Location: Wynnewood, PA
Two Chassis Preamp -- Capacitor Question
Default Two Chassis Preamp -- Capacitor Question


Please go easy on me -- I'm pretty new at this and have what may turn out to be a fairly dumb question. I am building an Aikido preamp in 2 enclosures using Bas Horneman's PCBs. The power supply chassis includes the transformers and the power supply PCB and will be connected to the preamp chassis using an umbilical cable.

Here's the question: I understand that some kind of RC network may be useful in smoothing out the two B+ lines when they enter the preamp chassis. I have some 10 ohm 5 watt resistors and little 47uf 400V electrolytic caps on hand. If I run each B+ line through one of the 10 ohm resistors followed by one of the 47 uf caps (pos side to B+, neg side to ground), will that do the trick?

Or have I got this all wrong?

Thanks for the help!

  Reply With Quote
Old 9th March 2006, 01:58 PM   #2
sreten is offline sreten  United Kingdom
Join Date: Nov 2003
Location: Brighton UK

if your talking about modifying an existing
design you've probably got something wrong.

(C)RC smoothing is common, but note the voltage drop depends
on R and the load current, 47uf sounds too low (or R is not high
enough) to be effective.

However it is unlikely that you've thought of something the designer
of the preamp hasn't already considered and included or rejected.

Can't really say without more circuit details.

  Reply With Quote
Old 10th March 2006, 07:45 AM   #3
AndrewT is offline AndrewT  Scotland
Join Date: Jul 2004
Location: Scottish Borders
what is the voltage and current you are playing with? Talking about B+ sounds like valve (tube) type voltages.

The 10r and 47uF gives a low pass filter of about 3400Hz.

This will not filter out mains hum or it's buzz type harmonics
regards Andrew T.
  Reply With Quote
Old 10th March 2006, 05:55 PM   #4
AndrewT is offline AndrewT  Scotland
Join Date: Jul 2004
Location: Scottish Borders
Default oops!

the roll off of a low pass 10r + 47uF is 340Hz.

The substance of my reply stands although a small amount of high harmonic buzzing will be removed at this lower cut off.

You need at least ten capacitors or 100r to give 34Hz as a starting point.

Can you afford the volts drop using 100r?
regards Andrew T.
  Reply With Quote
Old 10th March 2006, 09:43 PM   #5
lndm is offline lndm  Australia
diyAudio Member
Join Date: Mar 2006
Location: nsw
Why do you need it?

If your ps has filtered the DC suitably for driving your amps, the only reasons you may want to do it again after the umbilical are to filter RF picked up by the umbilical or to compensate for the impedance of the umbilical.

Problem 1 can be dealt with by keeping the umbilical short or by shielding it. Problem 2 is less of an issue for valve equipment than high current low impedance solid state equipment, but if you wish, use heavy cable.

Be wary of adding an extra stage to your ps unless the last capacitor is large enough to supply current to the circuit down to a low frequency.
  Reply With Quote


Two Chassis Preamp -- Capacitor QuestionHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
New Chassis Fabrication Pics and Capacitor Question Vespasian Tubes / Valves 9 28th January 2007 03:45 AM
Chassis for preamp/ amp for sale lgreen Swap Meet 2 29th December 2006 01:29 AM
Capacitor above chassis andRookie Tubes / Valves 14 2nd November 2006 02:32 PM
Tube preamp question...also, chassis layout jim_vt Tubes / Valves 1 22nd January 2006 12:01 AM

New To Site? Need Help?

All times are GMT. The time now is 04:02 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio