Class A amp - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 December 2004, 07:28 AM   #1
kro5998 is offline kro5998  Netherlands
diyAudio Member
 
Join Date: Dec 2004
Location: Tilburg
Question Class A amp

Hi, has anyone build or has expierience with the class A amps designed by Knutt Nygaard?
I was considdering building the current feedback design.Any comments would be welcome.
  Reply With Quote
Old 5th December 2004, 03:52 PM   #2
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Hé Mènneke,

at 25 watt it is laid out for Tj= 80 C.

The powersupply and heatsink cost a bundle: add two more 1216/2922 and the bias can go a lot higher with heatsink temperature at 55 C instead of 45 C., Tj =75 C.

4 times 2SA1216 or 2SC2922 go for 17 Euro at Schuro.
With a few alterations the PCB layout of the elektor LMA50 can be used for 4 output transistors.

Replace the wirewound by MPC71, at Schuro for 0.62 Euro or at Speaker en Co.
__________________
The buck stops Here
  Reply With Quote
Old 6th December 2004, 07:49 AM   #3
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
tell us more about MPC71. Advantages? Is Schuro the make or supplier?
regards Andrew T.
  Reply With Quote
Old 6th December 2004, 09:15 AM   #4
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Hi Andrew.

MPC71 is the name of the white block emitter resistor you see in japanese amplifiers for decades.

It is a metalband resistor with low self inductance, unlike wirewound resistors.
Not completely inductance free, resistors that are supposed to be are 10 times the price.
MPC71 has a 5watt rating, MPC72 is 10 watt, made by Motorola.
There is also a dual version, the MPC725, if space is limited.

Like ring emitter transistors, MPC's are easilly available nowadays for $ 0.50 a piece, a DIY bloke like me had to travel half of Europe to buy them for five times as much in my early college days.
I used to scavange broken japanese amps for these parts.
(still do actually, the MPC725 i call Double Dutch )

Nygaard also uses ceramic caps in his designs.
The ceramic caps i swapped for low cost styroflex capacitors.
(i cherish my precious Siemens styroflex's )
I havent got a clue why some still use ceramic caps, other than that they are cheap caps in the pF range.
Steve Bench did tests on capacitors, check out the curve for ceramic's.
Attached Images
File Type: jpg ceramic caps.jpg (10.8 KB, 261 views)
__________________
The buck stops Here
  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
1500W RMS Class D PCB - which Class D Driver Chip is it ? mosfetsound Class D 11 1st April 2011 11:17 AM
Can a Class AB PP amp be said to be operating in Class A at low signal levels? ray_moth Tubes / Valves 19 23rd January 2009 07:52 PM
How about a round-up of Class A kit power amps, or collectable vintage class A? Brisso57 Solid State 4 14th February 2007 10:30 AM


New To Site? Need Help?

All times are GMT. The time now is 04:07 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