Need help with buzzing amplifier - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 30th April 2012, 04:21 PM   #1
maurycy is offline maurycy  United States
diyAudio Member
 
Join Date: Dec 2005
Location: NJ
Default Need help with buzzing amplifier

I have built a guitar amplifier based on the Hitachi HA13118 chip. Unfortunately, it has a buzz. It is not hum but a clear buzz that gets louder with the volume. That's even without the guitar attached.

Here is a schematic:

guitar amp schematic

The power cord going to the trafo is two prong. Case is plastic and everything is basically attached as the schematic shows. The whole amplifier section is on a PCB so only in, out and power connections go to and from the board.
  Reply With Quote
Old 30th April 2012, 06:22 PM   #2
diyAudio Member
 
Join Date: Nov 2008
Location: Oakmont PA
Put a 22K resistor across C11. Any wattage any tolerance!
  Reply With Quote
Old 1st May 2012, 02:37 AM   #3
maurycy is offline maurycy  United States
diyAudio Member
 
Join Date: Dec 2005
Location: NJ
I guess there may be something wrong with the amp or the wiring as adding 22K resistor did not help at all. It looks like I will have to pull the board out and test it outside of the amp.

There is also big thump when I switch the power off.
  Reply With Quote
Old 1st May 2012, 03:46 AM   #4
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
Try running it from a battery,and see if the hum clears up. I'm wondering about your power supply layout and wiring. Got a pic of the amp?
  Reply With Quote
Old 1st May 2012, 10:56 AM   #5
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Have you downloaded the Hitachi datasheet?
__________________
regards Andrew T.
  Reply With Quote
Old 1st May 2012, 01:37 PM   #6
maurycy is offline maurycy  United States
diyAudio Member
 
Join Date: Dec 2005
Location: NJ
Here is a picture of the amplifier: picture. Not a great one and kinda hard to read what's inside. The PCB is a kit and only trafo, smoothing capacitors and diode bridge is outside of the amp board.

Andrew: Yes, I have downloaded the datasheet but with my limited knowledge, all the numbers and charts do not really tell me much. If I knew how to build a hum/buzz free amplifier, I wouldn't be buying a kit.
  Reply With Quote
Old 1st May 2012, 01:58 PM   #7
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Compare the schematic in post1 to the schematic in the datasheet.
I think they are probably different.
__________________
regards Andrew T.
  Reply With Quote
Old 1st May 2012, 02:19 PM   #8
maurycy is offline maurycy  United States
diyAudio Member
 
Join Date: Dec 2005
Location: NJ
Will do. The amp was built from the kit though. I wasn't expecting this amp to be hum/buzz free with 10% THD at full power but the current buzz is louder than my refrigerator.
  Reply With Quote
Old 2nd May 2012, 06:50 PM   #9
diyAudio Member
 
Join Date: Nov 2008
Location: Oakmont PA
Looking at your picture and the 22K resistor results, lets go a step farther. Dose this kit expect plus, minus and ground rails?

I see a full wave bridge rectifier and two sets of capacitors, which would imply a ground is needed. As the transformer is not center tapped, it looks like you have attached the wires between the filter capacitor as ground. If that is the case remove one of the transformer wires from the bridge rectifier and attach it to the ground between the capacitors.

Last edited by simon7000; 2nd May 2012 at 06:52 PM.
  Reply With Quote
Old 2nd May 2012, 06:55 PM   #10
maurycy is offline maurycy  United States
diyAudio Member
 
Join Date: Dec 2005
Location: NJ
Quote:
Originally Posted by simon7000 View Post
Looking at your picture and the 22K resistor results, lets go a step farther. Dose this kit expect plus, minus and ground rails?
From what I can tell only plus and minus DC. I was curious if there should be a ground but it is not on the schematic. The kit's description calls for a well filtered power supply to reduce hum but mine is loudly buzzing not humming.

I still have to pull the amp out and connect it to the 12V battery that I have to see if the buzz goes away.
  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
buzzing transformers.... rtate Solid State 38 7th April 2008 12:33 PM
Kenwood KA-9100 Amplifier Buzzing trustchild Solid State 6 4th December 2007 11:54 AM
Rotel amplifier buzzing, please help lt cdr data Solid State 10 14th November 2006 01:14 PM
My amplifier makes a buzzing noise Jimmy154 Solid State 7 25th October 2002 05:27 AM


New To Site? Need Help?

All times are GMT. The time now is 07:55 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