Point to Point Chipamps in Timber cases - 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 13th June 2011, 06:01 PM   #1
jemraid is offline jemraid  United Kingdom
diyAudio Member
 
Join Date: Aug 2004
Location: NE Derbyshire
Default Point to Point Chipamps in Timber cases

There is a similar thread to this aimed at one chip, it is also full of pics and some have complained about the sizes and the time it takes to open them all.

If you intend to submit to this thread please use the minimum amount of pics necessary so that members with slow connections may see them. There is a free application called Irfan View in which you can nominate the file sizes, I keep mine to less than 80k. Here is a link to the forums info page about posting images: http://www.diyaudio.com/forums/blogs...ges-forum.html


I made an LM3875 inverted gainclone to Thorstens circuit and have used it for about 7 years. I decided to make another amplifier to power my Frugel Horn Mk3's and tried and failed with a solid state circuit.

So I decided to make a 'posher' chipamp and I was able to obtain a pair of LM3876T on eBay and these formed the basis of my new non-inverted amplifier. I can work with timber and am useless at bending metal so that is my choice of material, in this case plywood from our local DIY shop.

Click the image to open in full size.

I mounted the heat sink on a piece of thick ply with a bit of MDF picture backing board for the pot. I've used 1/4 watt carbon resistors, as in the GainCard, matching them with my meter, the one metal film one that you can see is for the mute, this chip being similar to the LM3886. The caps are 100 uf and 0.1 uf and the FB resistor is 22k and the gain resistor Ri is 680R giving a gain of about 30.

Click the image to open in full size.

Starting at the back a 300VA 12-0-12 toroid I bought on eBay this was for my failed SS amp, the drive units in my FH3's are Mark Audio CHP-70's and are 4 Ohm so the 12v should be enough. next are 2 35 Amp bridges and then 2.2K resistors across the supply, 4,700 uf caps, 10,000 uf caps, 0.1 uf caps, and the snubber, 2.7R and 0.1uf. The power grounds come together at the front of the Veroboard. The cap sitting in the Blue Tak is for the mute. The amplifier assembly is mounted over a vent hole. The Vishay 10k pot is in place and the Zobel is screwed across the output, the pot shaft will be connected to some 6mm dowel and out through the front.

I powered it up in stages and checked power voltages each time, first with the bridges, then with the power supply, then with the amplifier but with no input, then with an old speaker and then finally when that was OK to one of my FH3's.

With the input connected to my paused CDP and turning the pot full up then placing my ear at headphone distance from the CHP-70's there is no sound whatsoever.

As for what it sounded like it's quite warm, what did surprise me was the detail certainly a bit better than my other GC. More on that later when I have finished it I will leave it on for a week quietly playing a tuner to itself. Ohh and yes the 12V is 17V at the power supply output and will easily drive the CHP-70's to painful levels.

I think that lots of 1st time DIYer's are reluctant to start an amplifier because like me they cannot work metal. I hope this thread will give some of them a start.

Jim
__________________
FH3 build using very simple tools and a point to point Gain Clone with largish power supply. http://www.jasread.com/fh3/index.html

Last edited by jemraid; 13th June 2011 at 06:07 PM.
  Reply With Quote
Old 13th June 2011, 09:57 PM   #2
diyAudio Member
 
tigersilver's Avatar
 
Join Date: Mar 2011
Blog Entries: 2
What do you think about the difference between the Toroidal transformer with IE transformer.
I usually use IE transformer.
Maybe next time use the Toroidal.

Last edited by tigersilver; 13th June 2011 at 10:00 PM.
  Reply With Quote
Old 13th June 2011, 10:20 PM   #3
jemraid is offline jemraid  United Kingdom
diyAudio Member
 
Join Date: Aug 2004
Location: NE Derbyshire
Dear Tiger,

Alas I wouldn't know I just buy as many bargains as I can find on eBay to keep the costs down. I'm a pensioner [waving my stick]

Though thinking about it doesn't Mr Sakura use a specially made EI tranformer in the GainCard now.

I think I read somewhere on here in 2004 when I made my first GC that toroids reacted faster but I'm probably wrong. I would imagine that the power supply caps would make up any shortcomings of a transformer providing of course that it was powerful enough for the use it's put to.

No doubt someone will provide enlightenment.

Regards - Jim

PS I like your wooden boxes, very well done indeed.
__________________
FH3 build using very simple tools and a point to point Gain Clone with largish power supply. http://www.jasread.com/fh3/index.html
  Reply With Quote
Old 15th June 2011, 08:12 PM   #4
Trebla is offline Trebla  United Kingdom
diyAudio Member
 
Join Date: Nov 2005
Location: North West
Nice one Jim.
That's reminiscent of my first GC build.
I built it on a piece of MDF with everything spaced out, because i expected all kinds of teething troubles. Thought it would be easier to work on.

As it happened the amp worked fine, and sounded so good that i wished i had made a better job of it.
So instead of rebuilding it, I put the whole thing in a large metal case.
Eventually it took the place of my MF A3 amp, because I preferred it.

Good luck.
  Reply With Quote
Old 16th June 2011, 09:20 AM   #5
jemraid is offline jemraid  United Kingdom
diyAudio Member
 
Join Date: Aug 2004
Location: NE Derbyshire
Hello Trebla,

I think building one spaced out a bit is a very good idea it does make it easier to change bits. In my first LM3875 build [link below] I changed the input caps several times.

Did you make yours point to point?

Jim
__________________
FH3 build using very simple tools and a point to point Gain Clone with largish power supply. http://www.jasread.com/fh3/index.html
  Reply With Quote
Old 17th June 2011, 07:23 AM   #6
Trebla is offline Trebla  United Kingdom
diyAudio Member
 
Join Date: Nov 2005
Location: North West
Quote:
Originally Posted by jemraid View Post
Hello Trebla,

I think building one spaced out a bit is a very good idea it does make it easier to change bits. In my first LM3875 build [link below] I changed the input caps several times.

Did you make yours point to point?

Jim
Yes it was Point to point and quite crudely done.
But it was successful.
Certain parts like input/output caps should be arranged so they're easy to swap.
Thats part of the fun isn't it.
  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
Point to point, from scatch build of the K-12G jmillerdoc Tubes / Valves 0 25th October 2009 01:40 AM
Wire Wrap connections for point to point mashaffer Tubes / Valves 10 7th July 2007 02:11 PM
Benifits of point to point wiring for digital circuit? MGH Digital Source 15 14th September 2006 11:17 PM
Anyone use magnet wire for point to point wiring projects? Hybrid fourdoor Parts 10 2nd February 2004 09:11 AM
Audio Note's Kit One done in point-to-point wiring Wram Tubes / Valves 18 29th April 2003 11:59 PM


New To Site? Need Help?

All times are GMT. The time now is 12:38 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