Help with Hum - Hum Help - Aikido - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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
Reply
 
Thread Tools Search this Thread
Old 16th February 2011, 11:34 PM   #1
JesseG is offline JesseG  Canada
diyAudio Member
 
JesseG's Avatar
 
Join Date: Jul 2005
Location: Mid coast of British Columbia
Default Help with Hum - Hum Help - Aikido

Not sure if this should be here on in Power Supplies, but here goes...

I am doing my best to fis up a friend's octal Aikido. The power supply needed some tlc, so I built a new one. It runs fine, but with an objectionable amount of 120Hz hum.

Put the scope on the power supply and I see a solid, waveform-perfect 2V sawtooth at the B+ point.

Here's the map - any ideas?
Attached Images
File Type: gif aikido ps.gif (9.0 KB, 123 views)
__________________
"If we crashed our cars as often as we crashed our computers, we'd all be dead!"

Last edited by JesseG; 16th February 2011 at 11:37 PM.
  Reply With Quote
Old 16th February 2011, 11:44 PM   #2
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
What does the sim in PSUDII predict? If it's much less than 2V, I would strongly suspect your grounding. Can you diagram how that was done?
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 16th February 2011, 11:52 PM   #3
JesseG is offline JesseG  Canada
diyAudio Member
 
JesseG's Avatar
 
Join Date: Jul 2005
Location: Mid coast of British Columbia
PSUDII predicts a 2V P-P sawtooth on the C following the choke (fancy that!)

The question is, how do I get rid of it from the Aikido's output?

Signal grounding is star at the input jacks. Power grounding is on the chassis.
__________________
"If we crashed our cars as often as we crashed our computers, we'd all be dead!"
  Reply With Quote
Old 17th February 2011, 12:07 AM   #4
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Well, you could put a regulator after the raw supply (that's what I did for the two Aikidos I built). You can also try nulling the noise- the voltage divider values for the nulling circuit that John suggests aren't exact and the adjustment to get a decent null is pretty sharp. So you can change one of them out for a resistor that's, say, 20% smaller than nominal in series with a trimmer that's, say, 40% of nominal, then have at it.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 17th February 2011, 04:43 AM   #5
fhs is offline fhs  Germany
diyAudio Member
 
fhs's Avatar
 
Join Date: Jan 2011
You clearly need smoothing capacitors on both sides of the choke.
  Reply With Quote
Old 17th February 2011, 07:50 AM   #6
diyAudio Member
 
Join Date: Dec 2008
Location: Victoria, BC
Quote:
Originally Posted by fhs View Post
You clearly need smoothing capacitors on both sides of the choke.
Well, something 'more' , I'd think. One choke and one cap (94uF) isn't much filtering, especially for a preamp. Even old table radios and guitar amps had more filtering than that.

Is there something special about the Aikido that lets it use noisy B+?
  Reply With Quote
Old 17th February 2011, 09:06 AM   #7
Hosam is offline Hosam  Syria
diyAudio Member
 
Join Date: Jan 2011
Location: Syria - Canada
I'm not so professional but I suppose coaxial cable from to the ground could help you to solve the problem if it come from AC noise. anyway you'll not loose anything if you try it even it simple.
  Reply With Quote
Old 17th February 2011, 10:07 AM   #8
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Excuse my ignorance, but what is supposed to be the purpose of the diode across the choke? This will bypass the choke on the downward swings of the AC, so destroying the whole point of a 'choke input' supply, by killing the choke current.
  Reply With Quote
Old 17th February 2011, 11:26 AM   #9
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by VictoriaGuy View Post

Is there something special about the Aikido that lets it use noisy B+?
Yes, it uses a noise-canceling tweak. That's its "claim to fame" and the origin of the "Aikido" moniker.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 17th February 2011, 12:09 PM   #10
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
If you short out the choke you will get a 300V supply with similar ripple. Then RC smoothing can drop and smooth it, but it would have high DC impedance.

If you remove the extra diode you will get a 200V supply with less ripple, and probably a lower output impedance. You could boost the voltage a little by adding a small capacitor before the choke.
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Aikido hum kacernator Tubes / Valves 29 29th December 2008 12:45 AM
tube hum in Aikido cbutterworth Tubes / Valves 3 8th March 2007 05:45 PM
Aikido hum has me stumped !!!! cbutterworth Tubes / Valves 21 17th January 2007 12:56 AM
Return to Aikido Hum issues cbutterworth Tubes / Valves 21 10th January 2007 12:59 AM
removing AC Hum on Aikido???? cbutterworth Tubes / Valves 6 24th December 2006 01:27 AM


New To Site? Need Help?

All times are GMT. The time now is 06:27 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2