Bridge construction - Page 3 - 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 5th August 2003, 01:09 PM   #21
matth is offline matth  United Kingdom
diyAudio Member
 
matth's Avatar
 
Join Date: Jun 2003
Location: Bristol
Quote:
Originally posted by Nuuk


Me again Carlos, I have had my GC monoblocks running continuously for four hours as I am trying to break in my rebuilt Goodmans 201s. When I read your post I went straight over to see if they are hot but they are only very slightly warm and it is very hot here today.

My MUR860's are just glued to a piece of fibreglass.


Ahha, a hot day in Somerset, have a nice cool cider.
  Reply With Quote
Old 5th August 2003, 01:10 PM   #22
mikelm is offline mikelm  England
diyAudio Member
 
Join Date: May 2003
Location: England
Send a message via Yahoo to mikelm
Quote:
Originally posted by Nuuk
So could I ask if that is a cap between the two secondary rails or between a single secondary and the zero volts rail. And presumably, it comes before the rectifier bridge?

Yes for dual rail, a cap from each to earth. It may well be better to have a resistor in series with the cap but I have not tried that yet so I could not comment.

mike
  Reply With Quote
Old 5th August 2003, 01:20 PM   #23
mikelm is offline mikelm  England
diyAudio Member
 
Join Date: May 2003
Location: England
Send a message via Yahoo to mikelm
Quote:
Originally posted by ALW


I've certainly seen it, by triggering on the DC sawtooth and then viewing the sinusoid from the transformer on a 'scope.


As for a cap sounding better, that may be - the frequency will be lower and may be more readily filtered. Surely it'as better to eliminate it entirely though - using a simple RC isn't exactly difficult.

The C part isn't critical, it just has to have low Z at the resonant frequency
Looks like I have to refine my scope techniques.

I will definetly try it with the resistors aswell

in spice experiments the value of C is directly linked to the resonant frequency - the bigger the cap the lower frequency. ball park figures 5uf about 4khz

cheers

mike
  Reply With Quote
Old 5th August 2003, 01:28 PM   #24
ALW is offline ALW  United Kingdom
diyAudio Member
 
Join Date: Jun 2001
Location: UK
Quote:
about 4khz
On a large toroid I measured, the leakage inductance / inter-winding capacitance was such that it's self-resonance was several MHz.

That's probably why it's hard to see.

Andy.
  Reply With Quote
Old 5th August 2003, 01:36 PM   #25
UrSv is offline UrSv  Sweden
diyAudio Member
 
UrSv's Avatar
 
Join Date: Jan 2002
Location: Sweden
Default Re: Re: Re: If it has a hole, it's for a heatsink

Quote:
Originally posted by carlosfm



-- snip --
UrSv, you're talking of a power amp, not a transistor radio or a preamp.
To be certain, you need to test, not just come with theories.
What makes you think your IGC doesn't need current?
I see you're one of those guys who think the power op-amps (like the LM3875) don't even need a heatsink, just put it on the bottom of a thin case and that's it.
I was actually speaking from experience. I use my Proac Clones and have had them playing loud for at least 4 hours in a room 32+ degrees centigrade and the 3875's, attached to the bottom of my not too thick case, get slightly warm to the touch but nowhere near anything called hot. The diodes are close to room temperature. And that even in a place where the air is restricted. And I'm running 25 VAC transformers. And I am playing Fourplay, Lisa Nilsson and others with a fair amount of long bass notes.

However, if we are talking a bridge GC used with powers in the order of 200 W for extended low frequency content, like a sub, and a 4 Ohm load then obviosuly I would think about at least mounting them to something heat dissipating. And checking the BPA-200 and the heatsink used it should be pretty obvious that the heatsink needed is very modest.
__________________
UrSv
Those who say it can't be done should not stop those who are doing it.
  Reply With Quote
Old 5th August 2003, 02:17 PM   #26
Banned
 
Join Date: Mar 2003
Location: Lisbon, Portugal
Default Re: Re: Re: Re: If it has a hole, it's for a heatsink

Quote:
Originally posted by UrSv

I was actually speaking from experience. I use my Proac Clones and have had them playing loud for at least 4 hours in a room 32+ degrees centigrade and the 3875's, attached to the bottom of my not too thick case, get slightly warm to the touch but nowhere near anything called hot.
Ok, but don't judge it that way.
If you only tested with one pair of speakers...
Maby your speakers are an easy load.
My Epos speakers, although 8 ohms, are a tough load, very hard to drive.
And I tested my GC with several speakers.
With some of them it's a piece of cake and it only gets warm.
But with a pair of Allison 4 ohm speakers, for testing purposes listening very loud, I managed to "see" the thermal protection in action.
On the datasheet it says it kicks in at 150C!
What it does is to reduce the volume, then it cool a little and then up again.
The result is the volume up-down-up-down.
I don't need to tell you that when I put my hand on the bottom of the case I almost got without skin.
This was listening very loud, for testing only, as I don't listen to music that way.
But this serves to see that each case is a case and some people have some speakers, other people have other speakers and the results may vary.
With some speakers it will get hot even at "normal" volumes.
What I can tell you is that you can make it go very hot, in a question of a few minutes if you don't have a decent heatsink.
These days more and more speakers are 4 ohms, or have 4 ohm woofers.
The majority of american speakers nowadays are 4 ohms.
Nevermind, I usually prefer the british speakers.
Or the ones I made with Seas units.
  Reply With Quote
Old 6th August 2003, 07:50 PM   #27
diyAudio Member
 
Join Date: Oct 2002
Location: UK
Thumbs up Neat Bridge from Avondale

I like the look of this bridge from Avondale Audio in the UK.

http://www.users.zetnet.co.uk/avondale

http://www.users.zetnet.co.uk/avondale/Bridge.jpg

The bare pcb is 4.50 GBP.

Anyone used one of these?

I think it could do nicely - especially with some small anodised heatsinks on the board!

Cheers

Jon
  Reply With Quote
Old 6th August 2003, 08:29 PM   #28
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Quote:
Originally posted by ALW
I'd leave the caps off though, if it were me.

In my experience they almost always sound worse, and provide a better path for HF noise from mains supply / transformer to the PSU.

Try proper snubbers, instead, but put them at the transformer, where they belong.

http://www.hagtech.com/pdf/snubber.pdf

Peter seems to have totally misunderstood a snubber - electing to 'leave the resistor out'.

Without the resistor, it's not snubbing...

We won't touch on the star-point at the bridge instead of the caps - maybe that's history?

Andy.

Actually I didn't misunderstood anything. I just chose to do it that way because of space limitation and my thinking that even without resistor it is still better. Also, in one of the threads dealing with snubbers, the was opinion, that in certain setups, capacitor alone is enough. These days I'm not using the caps across diodes at all, as I think it sounds worse (I'm actually listen to parts and circuits now). The picture of the bridge is from the Aleph X (this may be also a reason why GC sounds better).

So, in GC there's no snubbers, just diodes. And on certain material and speakers the diodes get pretty hot, but still you'll be able to touch them. Same goes for the chip. Once I got my amp hot at at least 50 deg. C, where normally it's barely warm. Thge only extra caps I'm using now is a pair of 4.7 BG N right after bridges, on ea. rail to ground.
__________________
www.audiosector.com
Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it. - JC
  Reply With Quote
Old 6th August 2003, 08:49 PM   #29
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Quote:
Originally posted by ALW
There's an excellent articel here that tells you how to design the snubber properly, for a given PSU.

http://131.109.59.51/images/pdf/Calc...m_Snubbers.pdf

Andy
That's the link from the snubbers thread. On page 10 of the article we can read:

It is interesting to see what happens when only a capacitor is used as a snubber, as is
commonly recommended. A value of 0.01uF was added for C x and then simulated.
Figure 11 shows the results.
Figure 11. 0.01uF capacitor only snubber.
Ringing is still evident, no damping or snubbing has occurred, however the frequency is
much lower.

Obviously the improvement in sonic quality or reduction of noise occurs because the
ringing frequency is so much lower that the ability to couple to other circuits is reduced.
In fact, the larger the capacitor, the lower the frequency. All of this very much depends
on the quality of the components and the transformer involved. It should come as no
surprise that each power supply must be individually tuned for optimum performance.


So my understanding is that if someone doesn't want to go through all those snubber calculations, using a single high value cap across diodes, should still bring improvement (at least that's what' suggested in the article) and many manufacturers are practising that. But as I said before, I prefer to choose better sounding diodes and forget about all those snubber issues. I also suspect, that although snubbers may improve certain aspects of performance, they screw up sonics in some other way.
__________________
www.audiosector.com
Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it. - JC
  Reply With Quote
Old 6th August 2003, 09:14 PM   #30
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Just a thought but as some are finding diodes running hot and others not, could the snubber caps have any affect on the temperature that the diodes run at?
__________________
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Reopening an unfinished debate: Dual bridge vs. Single Bridge xiphmont Chip Amps 15 26th February 2008 08:22 PM
half-bridge VS. full-bridge gearheadgene Class D 3 25th May 2007 09:49 PM
The difference of Push-pull,Half-bridge,Full-bridge digi01 Chip Amps 0 8th September 2006 03:10 AM
Whats the difference between full bridge and half-bridge SMPS ? skaara Class D 6 3rd February 2005 08:23 PM


New To Site? Need Help?

All times are GMT. The time now is 05:50 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