Brain GT 3886 PS question - 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 4th April 2005, 09:24 PM   #1
lgreen is offline lgreen  United States
diyAudio Member
 
lgreen's Avatar
 
Join Date: May 2003
Location: San Diego, USA
Default Brain GT 3886 PS question

Sooo.... I'm trying to put together the Brian GT power supply for the snubber PS. I've got one transformer and 16 diodes to deal with. I'm about to connect it as shown-- using option #2 in the attached picture (taken from chipamp.com and annotated with what I suppose are the correct connection names). This means that I'm going to tie the center tap together and ground it, as well as ground the "ground" outputs, all to the star power ground. Is this correct?

(I've also changed the primary to reflect what I believe I have going on in #2)

I note that option #1 is what he shows on the web site, note that the transformer is shown floating, nothing on it is grounded. Seems odd to me. Anyway, just trying to do this without blowing something up like I normally do.

Comments on how to connect the xformer to the board with one xformer insteand of 2, and using all appropriate grounds?
Attached Images
File Type: jpg annotated.jpg (76.6 KB, 690 views)
  Reply With Quote
Old 4th April 2005, 11:01 PM   #2
chrish is offline chrish  Australia
diyAudio Member
 
chrish's Avatar
 
Join Date: Oct 2003
Location: Sydney
If you are doing a simple stereo amp, then just connect as Brian describes. If you are then getting problems with ground loops and hum, then start making changes. Not sure what you are saying about having one transformer and 16 diodes. You will only need 16 diodes if you have two transformers and two power supplies. With one transformer you connect to one power supply board, the board has provision to power two amps (2*V+, 2*PG+, 2*PG_, 2*V-).

Good luck with the project,

Chris
  Reply With Quote
Old 5th April 2005, 02:27 AM   #3
homer09 is offline homer09  Canada
diyAudio Member
 
homer09's Avatar
 
Join Date: Jan 2004
Location: Montreal
If you have 16 diodes, that means you have enough for two diode bridges (ie. two power supply boards). If you are only using one transfo, then you will have to split the leads of your transfo and connect to the two bridges.

in other words, connect two wires to each secondary lead from your transfo, and then take one set connect it to one bridge same way you would having a single tranfo/single bridge setup. and then do the same with the other set of leads and the other bridge.

in yet other words, connect your bridges in parallel to your transfo.

this is the approach i am taking also, although my transfo is not center tap.
__________________
Most people wouldn't know good music if it came up and bit them in the ***. - Frank Zappa
  Reply With Quote
Old 5th April 2005, 03:09 AM   #4
BrianGT is offline BrianGT  United States
diyAudio Moderator Emeritus
 
BrianGT's Avatar
 
Join Date: Jan 2002
Location: near Atlanta, GA
Send a message via AIM to BrianGT
Default Re: Brain GT 3886 PS question

Quote:
Originally posted by lgreen
Sooo.... I'm trying to put together the Brian GT power supply for the snubber PS. I've got one transformer and 16 diodes to deal with. I'm about to connect it as shown-- using option #2 in the attached picture (taken from chipamp.com and annotated with what I suppose are the correct connection names). This means that I'm going to tie the center tap together and ground it, as well as ground the "ground" outputs, all to the star power ground. Is this correct?

(I've also changed the primary to reflect what I believe I have going on in #2)

I note that option #1 is what he shows on the web site, note that the transformer is shown floating, nothing on it is grounded. Seems odd to me. Anyway, just trying to do this without blowing something up like I normally do.

Comments on how to connect the xformer to the board with one xformer insteand of 2, and using all appropriate grounds?
I labelled the AC secondary windings in the schematic:
http://www.chipamp.com/images/ps-rev3-sch.gif
(if picture is still the old picture, reload/clear your cache)

For wiring 2 boards to 1 transformer, the same wires are connected in both board (parallel configuration).

With regards to the ground, the grounding is done from the amp pcb, with the CHG (chassis ground) pads on the amp boards connecting to both the chassis and the AC gnd connection coming in from the IEC connector.

Let me know if you still have questions. If I don't reply to this thread, drop me an e-mail, as I might miss this reply since I don't have e-mail notification turned on.

--
Brian
  Reply With Quote
Old 5th April 2005, 12:52 PM   #5
diyAudio Member
 
Join Date: Feb 2004
Location: Mt. Pleasant SC
Brian,

I hate to show my ignorance but... are you saying that the center tap doesn't get connected to anything if you using the snubber? I'm in the process of building one of your LM4780's. Almost have the chassis done & will start on the boards this weekend. By the way I hope the 4780 sounds as good or hopefully even a little better than the GC I built with your very 1st boards.


Thx
  Reply With Quote
Old 5th April 2005, 03:01 PM   #6
BrianGT is offline BrianGT  United States
diyAudio Moderator Emeritus
 
BrianGT's Avatar
 
Join Date: Jan 2002
Location: near Atlanta, GA
Send a message via AIM to BrianGT
Quote:
Originally posted by kestrel200
Brian,

I hate to show my ignorance but... are you saying that the center tap doesn't get connected to anything if you using the snubber? I'm in the process of building one of your LM4780's. Almost have the chassis done & will start on the boards this weekend. By the way I hope the 4780 sounds as good or hopefully even a little better than the GC I built with your very 1st boards.

Thx
The transformer shown is not a center-tapped transformer, so there are no unwired connections. The transformer shown has dual secondary windings, which are each fed to the bridge rectifier seperately. The grounds are later referenced to each other on the amp board. (PGND+ and PGND-)

As for a center-tap transformer, you can follow the method shown in the LM3875 manual on the website, which should work for this board.

Often a center-tap transformer can be converted to dual secondaries, as the center-tap is often just 2 secondary windings with the middle wires tied to a common lead.

Let me know if there is still confusion.

--
Brian
  Reply With Quote
Old 5th April 2005, 03:51 PM   #7
diyAudio Member
 
mrlots2do's Avatar
 
Join Date: May 2004
Location: Philadelpia
Quote:
Originally posted by BrianGT

As for a center-tap transformer, you can follow the method shown in the LM3875 manual on the website, which should work for this board.
Hi Brian,
I understand this but have questions. Center tapped transformer with 3875 schematic showing use of 4 doides and jumpers on pcb.

1) Would there be an advantage to splitting center tap lead without splitting to dual coils and soldering to AC1H and AC2N using 8 diodes?

2) Why is it better to have dual rectifier bridges?

Phil
  Reply With Quote
Old 5th April 2005, 06:54 PM   #8
diyAudio Member
 
Join Date: Feb 2004
Location: Gainesville, FL
This should help.?!.?!
Attached Images
File Type: jpg wiring with ct transformer.jpg (30.1 KB, 415 views)
__________________
It's better to have loved & lost than to never have had a good pair of speakers at all.......
  Reply With Quote
Old 5th April 2005, 07:04 PM   #9
steenoe is offline steenoe  Denmark
diyAudio Member
 
steenoe's Avatar
 
Join Date: Mar 2004
Quote:
This should help.?!.?
I do not think that is possible. Take a look at that centertap and see if it possible to separate the centertap connection in two! Often enough it is You are gonna have trouble, if the grounding of AC1 and AC2 meets at some point later You would be better of using Brians suggestions in the manual, for a centertap!

Steen.
  Reply With Quote
Old 5th April 2005, 07:55 PM   #10
diyAudio Member
 
mrlots2do's Avatar
 
Join Date: May 2004
Location: Philadelpia
Chris
That was what I had in mind. This configuration appears to need 8 diodes.

Steenoe
What would happen if I wire it as Chris's pic shows?
What advantage would dual rectifier bridge be?
  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
Question on Ne5532 + 3886 amp on Ebay JackM11 Chip Amps 12 27th July 2010 02:34 PM
Dumb Question Brain is numb today! coldcathode Tubes / Valves 17 31st March 2009 09:47 PM
music, trance, and brain chemistry question faustian bargin Music 15 7th July 2006 06:07 PM
3886 Transformer wiring stupid question thermonuclear Chip Amps 2 16th September 2005 05:38 PM


New To Site? Need Help?

All times are GMT. The time now is 06:28 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