Gainclone building thread based on BrianGT's boards - Page 2 - 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 24th March 2004, 03:40 PM   #11
speaker is offline speaker  United States
diyAudio Member
 
speaker's Avatar
 
Join Date: Mar 2004
Location: USA
Quote:
Originally posted by BrianGT


The resistor is the negative feedback resistor. In order to obtain the best performance from the LM3875, the feedback look must be as short as possible. This component has the most effect on the amplifier's performance.

This resistor can be soldered right in front of the lm3875, or on the bottom side of the pcb.

--
Brian

Ah, that makes complete sense now and is an elegant solution. It appeared that you wanted it to track thermally with the output device and I could not figure why.

speaker
  Reply With Quote
Old 24th March 2004, 04:40 PM   #12
speaker is offline speaker  United States
diyAudio Member
 
speaker's Avatar
 
Join Date: Mar 2004
Location: USA
Quote:
Originally posted by meat


There is more information on the top of this thread

Group order of non-inverted LM3875 pc boards? Anyone interested?
Thank you!

speaker
  Reply With Quote
Old 24th March 2004, 04:43 PM   #13
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 speaker



Ah, that makes complete sense now and is an elegant solution. It appeared that you wanted it to track thermally with the output device and I could not figure why.

speaker
I like the appearance with the resistor in the front the best.

Another option, if you are using the T package along with the thick thermal insulator, would be to place the resistor on the back side of the LM3875T, and you can probably even get it a bit closer to the actual leads. This is what I did on my prototype.

I do still like it best as pictured below.

--
Brian
Attached Images
File Type: jpg nfb.jpg (59.4 KB, 5410 views)
  Reply With Quote
Old 24th March 2004, 04:43 PM   #14
matjans is offline matjans  Netherlands
diyAudio Member
 
matjans's Avatar
 
Join Date: Aug 2003
Location: Utrecht, NL
Send a message via MSN to matjans
Default Re: Fuse

Quote:
Originally posted by vsr123
I think a 1.5A to 2A fuse should be enough. Not sure if you need a slow blow type though since the inrush current should be small. If you read other threads the general comment is to keep trying different fuses until they stop blowing! :-)

cheers
vsr

that's just what i did and i settled with an 1.5 amp sloblo fuse for use with a 225 VA toroid
  Reply With Quote
Old 24th March 2004, 04:46 PM   #15
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: Re: Fuse

Quote:
Originally posted by matjans

that's just what i did and i settled with an 1.5 amp sloblo fuse for use with a 225 VA toroid
I am currently using a 2A fuse in mine. I had a 3A fuse in my previous unit. Neither of them has ever blown (both slowblo), so 2A should be fine. I haven't tried lower than 2A.

I am curious to see what the 2 channel Bridgeclone that I am looking at building will require (12 boards total on a 1kVA transformer)..... I am hoping that the 1kVA is enough for both channels, as I am not buying another transformer.

--
Brian
  Reply With Quote
Old 24th March 2004, 04:58 PM   #16
Coulomb is offline Coulomb  England
diyAudio Member
 
Coulomb's Avatar
 
Join Date: Jul 2002
Location: Ancaster, Ontario
What's the secondary voltage required for a gainclone?

Anthony
  Reply With Quote
Old 24th March 2004, 05:02 PM   #17
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 Coulomb
What's the secondary voltage required for a gainclone?

Anthony
I am using 2x24vac and Peter is using 2x22vac.

The datasheet specifies |-V| + |+V| to be in the range of 20vdc to 84vdc.

(just realized that this is my 2000th post)

--
Brian
  Reply With Quote
Old 24th March 2004, 05:04 PM   #18
Coulomb is offline Coulomb  England
diyAudio Member
 
Coulomb's Avatar
 
Join Date: Jul 2002
Location: Ancaster, Ontario
I have a spare 750VA 2x30VAC Toroid, I could use that then? 42VDC Rails.

Anthony
  Reply With Quote
Old 24th March 2004, 05:10 PM   #19
diyAudio Member
 
Join Date: Dec 2003
Location: Atlanta, GA, US
Send a message via ICQ to tpenguin Send a message via AIM to tpenguin Send a message via Yahoo to tpenguin
Quote:
Originally posted by BrianGT


That is what I said about my Aleph projects... and the Cardas posts came in, and are still sitting on the shelf.

I also have piles of heatsinks scattered all over my apartment... (8+8+4+4=24 heatsinks waiting to be used)

...And yet he still won't sell me any of the nice ones. He must be must be saving them for another imaginary project .
  Reply With Quote
Old 24th March 2004, 05:16 PM   #20
diyAudio Member
 
Join Date: Dec 2003
Location: Atlanta, GA, US
Send a message via ICQ to tpenguin Send a message via AIM to tpenguin Send a message via Yahoo to tpenguin
Quote:
Originally posted by BrianGT


I am using 2x24vac and Peter is using 2x22vac.

The datasheet specifies |-V| + |+V| to be in the range of 20vdc to 84vdc.

(just realized that this is my 2000th post)

--
Brian
Well, then shouldn't I be able to use the ~30-0-30 transformer I pulled out of that old yamaha? It would certainly be a little close to the limits of the SOA, but I like living on the edge, hehe. In fact, I've run my computer's CPU at over two volts (>25% increase over normal) for overclocking and it survived. It's also a lot more expensive than an LM3875.

Oh yeah, and congratulations on the 2000th post.
  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 08:48 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