Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, 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 28th September 2012, 10:33 PM   #1
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Default Star grounds are just as important with low level signals.

I always though that star grounds were only important in power amplifiers.

I quickly threw together a 6 channel pre-amp onto a pcb and got it made.
When I got it back I powered it up only to get a lot of hum.
I tried wiring up the ground tracks to reduce impedance and this only helped slightly. I found just shorting out between some traces helped more than others.
In the end I split off thew power supply onto a seperate peice of veroboard and the hum just went away.

So I started on my next revision of pcb, this time using star grounds for the power supply and the audio IC's. When I got the pcb back it worked like a dream. I wasted a batch of pcb's because of my ignorance of grounding. I had thought just good decoupling was needed but this clearly wasnt enough.

A valuable lesson in electronics.
__________________
http://www.murtonpikesystems.co.uk PCBCAD50 pcb design software.
  Reply With Quote
Old 29th September 2012, 06:55 PM   #2
diyAudio Member
 
indianajo's Avatar
 
Join Date: Jan 2010
Location: Jeffersonville, Indiana USA
I second the title. I knocked some hum out of my RA88a disco mixer by floating the RCA rings (analog ground) from the steel case (safety ground and turntable arm shell). I used o-rings. The PWB is still a jumble, but it is close enough in sound to the legendary PAS2 to furlough the 120 watt tube icon to the attic.
Amazing how the production engineers can mess up a design. They had the 120 vAC power switch right next to the magnetic phono (50x gain) op amps. Eliminating the 17 VAC center tap power transformer from the steel case and buying a wall transformer helped a lot, too.
__________________
Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300

Last edited by indianajo; 29th September 2012 at 07:08 PM.
  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
Are piezo elements line-level or instrument-level signals? JGAN Instruments and Amps 27 17th April 2012 01:38 PM
Best Miniature Toggle switch for low level signals stellavox Parts 1 3rd September 2011 05:26 PM
Newbie question regarding star grounds... nukegoat Chip Amps 8 5th November 2007 07:58 PM
Muting line level signals Positron Tubes / Valves 8 25th July 2007 09:16 PM
Whopee/Thanks Nuuk/Star grounds @#$%^& chipco3434 Chip Amps 1 13th December 2004 08:38 AM


New To Site? Need Help?

All times are GMT. The time now is 08:35 PM.


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