m250 - 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 17th June 2005, 06:55 PM   #1
ldanto is offline ldanto  United Kingdom
diyAudio Member
 
Join Date: Jun 2005
Location: somewhere.......
Send a message via MSN to ldanto
Arrow m250

ok, so i know there are loads of threads on Marcus's M250, but i'm doing this because i like the m250

His website is here
  Reply With Quote
Old 18th June 2005, 01:41 AM   #2
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
To answer your question about smoothing caps - no. For an amplifier like this you want at least 10,000uF capacitance PER RAIL, and they must be able to withstand the rail voltage so you'll need 63V capacitors.

Generally, the more capacitance you have, the smoother the voltage and the more energy reserve the amp has which leads to better bass. AS you can see Marcus uses 2x22,000uF per rail, this could be a bit expensive. Check prices on Farnell and you'll see that these sort of high capacity high voltage caps are expensive. As an example 10,000uF 63V capacitors from Panasonic (Farnell part code 652179) are 6.31 each. I would suggest looking on eBay for filter capacitors. I have sent you a private message with a link to an eBay auction you may be interested in.
  Reply With Quote
Old 19th June 2005, 11:32 AM   #3
ldanto is offline ldanto  United Kingdom
diyAudio Member
 
Join Date: Jun 2005
Location: somewhere.......
Send a message via MSN to ldanto
i think i've found the solution to the smoothing caps- an old computer monitor which has been sat in my garage roof for a couple of months. i'll stick a large rod into the ground and use some fairly thick wire to drain what little charge will be left in them now. of coure, i don't know the value and voltage, but i know that they are usually pretty large and that will give me a really smooth supply


would there be any problem with using these caps apart from the need to completely drain the caps before desoldering?
  Reply With Quote
Old 19th June 2005, 12:01 PM   #4
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
They will be only 1000uF (at the most), at 400V+, so not really enough capacitance. Also, if they've been in an old monitor they are likely worn due to the heat.
  Reply With Quote
Old 19th June 2005, 03:02 PM   #5
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
Quote:
Originally posted by ldanto
i think i've found the solution to the smoothing caps- an old computer monitor which has been sat in my garage roof for a couple of months. i'll stick a large rod into the ground and use some fairly thick wire to drain what little charge will be left in them now. of coure, i don't know the value and voltage, but i know that they are usually pretty large and that will give me a really smooth supply


would there be any problem with using these caps apart from the need to completely drain the caps before desoldering?

depends on what type of montor you have, most likely autovolt from90 vac to 240vac, in which case the filter caps inside can be a 150ufd to 470ufd 400wvdc, which is not of any use in our case! tube amps can use that kind of caps however......
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 19th June 2005, 10:26 PM   #6
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
The major cost with building an amp is:
* Case
* Heatsinks
* Capacitors for PSU
* Transformer
* Power Transistors (although if you're lucky you can take advantage of OnSemi's sample program).

A good idea might be to visit a junk electronics store, and see if they have an old amplifier/reciever in that's busted. Chances are the power supply components will be fine, and if you're lucky the casing can be reused.

The other major source for these parts on the cheap is eBay, you just have to keep watching.
  Reply With Quote
Old 20th June 2005, 04:26 PM   #7
ldanto is offline ldanto  United Kingdom
diyAudio Member
 
Join Date: Jun 2005
Location: somewhere.......
Send a message via MSN to ldanto
well the caps are sealed in a unit which needs to be cut open so i don't think i'll bother....
  Reply With Quote
Old 23rd June 2005, 02:32 PM   #8
diyAudio Member
 
Join Date: May 2005
Location: Bulgaria
hi guys, i'm going to build that M250 power amp but i'm just wondering has anyone used power transistors other than Motorola ones? I've found here in Bulgaria some MJ15024/25 pretty cheap (about $2 each) but they are not made by Motorola. However there are also Motorola ones for about $6 each which will be too expensive for me. thanks
  Reply With Quote
Old 23rd June 2005, 10:02 PM   #9
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
The non-motorola ones are probably fakes. Although, these transistors are now branded "ON" from On Semiconductor.

At $2 each you can bet they are 2955/3055 rebranded, ie fakes. They would just blow when you try and use them, as the Vceo is not good enough. Read http://sound.westhost.com/counterfeit.htm for more details

Maybe you should see if the On Semiconductor samples program on their website will deliver to your country.
  Reply With Quote
Old 24th June 2005, 05:24 AM   #10
diyAudio Member
 
Join Date: May 2005
Location: Bulgaria
Quote:
Originally posted by jaycee
The non-motorola ones are probably fakes. Although, these transistors are now branded "ON" from On Semiconductor.

At $2 each you can bet they are 2955/3055 rebranded, ie fakes. They would just blow when you try and use them, as the Vceo is not good enough. Read http://sound.westhost.com/counterfeit.htm for more details

Maybe you should see if the On Semiconductor samples program on their website will deliver to your country.
thank you, this info was very helpful. i'm gonna buy few of these cheap ones and i'll make some tests with them.
  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
M250 featherspeed Solid State 3 3rd August 2007 02:57 PM
p3a vs m250 john-china Solid State 0 23rd February 2006 06:17 AM
the m250 fity Solid State 0 24th January 2006 06:44 PM
Adjusting the M250 @fundum Solid State 2 8th July 2004 09:02 AM
M250 Cheese Solid State 1 13th November 2003 06:18 AM


New To Site? Need Help?

All times are GMT. The time now is 08:02 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