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 12th August 2003, 07:18 AM   #1
Raka is offline Raka  Europe
diyAudio Member
 
Raka's Avatar
 
Join Date: Aug 2002
Location: Close to Oistrakh
Default PG and SG

Hi,

Just a small question I have.

I'm building another GC, but now with panasonic FC and a IC buffer a la Nuuk and maybe a bigger supply. I'm using now solid wiring and trying to build it clean.

I finished yesterday the 1st channel (without the buffer) and the chip got very hot despite my care with the wiring. Could be that I didn't put the input cap and the resulting offset close to 250mV if I remember right heated the chip? I don't know, but this has easy solution.

But my concern is that oscillation is caused. As they were very close, I used the same point for both signal and power ground, and there comes my question from: Is there any technical reason to not to tie together SG and PS?
__________________
What is beyond the speaker?
  Reply With Quote
Old 12th August 2003, 07:29 AM   #2
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Sofia
Hi Raka

250mV offset is way too much and i suspect it is not offset but oscillation. No scope? Offset will certainly not cause the chip to heat up, especially without a load. The main reason for separating SG and PG is to avoid heavy PS currents producing voltage drops in the SG line and thus modulating the input voltage. Generally combining the two grounds may not be good for the sound but would hardly lead to oscillation. Got ps decoupling close to the chip?


cheers
peter
  Reply With Quote
Old 12th August 2003, 07:39 AM   #3
Raka is offline Raka  Europe
diyAudio Member
 
Raka's Avatar
 
Join Date: Aug 2002
Location: Close to Oistrakh
No scope.

The caps are soldered to the chip pins, like I did with my first GC which had no temperature rise.
After I fitted the cap I got 0.0mV, but I did this after half an hour of listening music at medium level.

I separate both grounds, and then linked then with a single wire, right? Well, what if instead a wire I joined both? The only difference would be the impedance of the link, right? but what impedance has a 2cm wire?
__________________
What is beyond the speaker?
  Reply With Quote
Old 12th August 2003, 07:46 AM   #4
diyAudio Member
 
Steve Eddy's Avatar
 
Join Date: Sep 2002
Location: Sacramento, CA
Default Re: PG and SG

Quote:
Originally posted by Raka
But my concern is that oscillation is caused. As they were very close, I used the same point for both signal and power ground, and there comes my question from: Is there any technical reason to not to tie together SG and PS?
Tying the signal and power supply grounds together at the same point is good practice. But more important in terms of oscillation is what's going on with the other power supply leads, i.e. your positive and negative rails.

To avoid oscillation, you want your voltage lines and your power supply ground line(s) as close together as possible to keep the inductance of the power supply leads as low as possible. The greater the separation between them, the greater their inductance and the more likely you are to develop oscillation problems as the signal effectively gets fed back by way of the power supply lead inductance and the amp's compensation capacitor.

So the solution may be as simple as dressing up your supply leads. As analog_sa mentioned, try some decoupling caps near the supply pins and see if that takes care of the problem. If it does, that will at least tell you where the source of the problem is.

se
  Reply With Quote
Old 12th August 2003, 08:18 AM   #5
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Quote:
So the solution may be as simple as dressing up your supply leads.
Steve, what exactly does 'dressing up' involve? And I am talking leads here
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 12th August 2003, 08:41 AM   #6
diyAudio Member
 
Steve Eddy's Avatar
 
Join Date: Sep 2002
Location: Sacramento, CA
Quote:
Originally posted by Nuuk
Steve, what exactly does 'dressing up' involve? And I am talking leads here
Well, argyle knit stockings are all the rage this year and would look just adoooooorrable on most any pair of leads.

You didn't really think I'd let your "I am talking leads here" get in the way of a smart-*** comment from me did you?

No, I just mean keeping the power supply leads in close proximity to keep power supply inductance low whether by twisting, braiding, what have you. Don't know just how Raka's got the leads running or if it may be in a more cobbled-together-just-to-see-if-it-doesn't-blow-up-and-then-I'll-do-it-all-up-neater-later stage or what so just threw that one out.

se
  Reply With Quote
Old 12th August 2003, 08:42 AM   #7
Raka is offline Raka  Europe
diyAudio Member
 
Raka's Avatar
 
Join Date: Aug 2002
Location: Close to Oistrakh
With "ps decoupling close to the chip" you mean the 1000uF caps, don't you?
__________________
What is beyond the speaker?
  Reply With Quote
Old 12th August 2003, 08:53 AM   #8
Raka is offline Raka  Europe
diyAudio Member
 
Raka's Avatar
 
Join Date: Aug 2002
Location: Close to Oistrakh
Quote:
Originally posted by Steve Eddy


Well, argyle knit stockings are all the rage this year and would look just adoooooorrable on most any pair of leads.

You didn't really think I'd let your "I am talking leads here" get in the way of a smart-*** comment from me did you?

No, I just mean keeping the power supply leads in close proximity to keep power supply inductance low whether by twisting, braiding, what have you. Don't know just how Raka's got the leads running or if it may be in a more cobbled-together-just-to-see-if-it-doesn't-blow-up-and-then-I'll-do-it-all-up-neater-later stage or what so just threw that one out.

se

I didn't understand the first two paragraphs, but suppose that are kind of ironic jokes

Then, if I simply twist a little bit the four power supply leads of the first channel I probably avoid this problem, right? I'll try asap.

Steve, I have a very good looking arrangement , not a rat nest like the first one (that worked cool, btw)
__________________
What is beyond the speaker?
  Reply With Quote
Old 12th August 2003, 09:03 AM   #9
diyAudio Member
 
Steve Eddy's Avatar
 
Join Date: Sep 2002
Location: Sacramento, CA
Quote:
Originally posted by Raka
I didn't understand the first two paragraphs, but suppose that are kind of ironic jokes
Ironic? Naaaah. Smart-***.

Just having some fun with some word play. Nuuk asked about "dressing" the leads so I came back acting like some gay audio fashion consultant.

Quote:
Then, if I simply twist a little bit the four power supply leads of the first channel I probably avoid this problem, right? I'll try asap.
Don't know about probably. Just offered it as one possibility to consider.

Quote:
Steve, I have a very good looking arrangement , not a rat nest like the first one (that worked cool, btw)
Hehehe. If that's the case, then it may well be something else. But knowing what it isn't gets you closer to what it is.

2:00 AM here so I'm off to bed for now.

Good luck!

se
  Reply With Quote
Old 12th August 2003, 11:38 AM   #10
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
I built some interconnects with the conductors insulated inside shoe laces. Does that count as lead dressing?
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  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



New To Site? Need Help?

All times are GMT. The time now is 07:50 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