Amplifier kit on eBay - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 6th January 2012, 07:13 PM   #1
diyAudio Member
Join Date: Mar 2001
Location: Brazil
Default Amplifier kit on eBay

I found this amplifier kit on eBay:

NJW0302G NJW0281 Stereo Power Amplifier Kit for diy Ref MA-9S2 MA-9 | eBay

Has someone built it?

I seem to recall that someone here did buy it and built it, but my search did not get me anywhere.
  Reply With Quote
Old 6th January 2012, 07:44 PM   #2
johnmik is offline johnmik  United States
diyAudio Member
Join Date: Jun 2006
Location: Wolcott, Connecticut
you're going to need a nice heat sink for mounting the outputs on. I've seen alot of these on Ebay out of China, never tried any yet.
just wanted to make a point about heat sinking on this kind of stuff. It's not included.

My .02
john M
Lots of Kenwood, Pioneer, and Infinity stuff.
  Reply With Quote
Old 6th January 2012, 08:51 PM   #3
diyAudio Member
Join Date: Mar 2001
Location: Brazil
Well, of course I will need a good heatsink for this amp or any power amps that pretends to output more than 30 watts. Cooling an amp heat is not something to be taken lightly, or parts will suffer, such as the output transistors or even the speakers.

These kits never include the large heatsinks, at least those from eBay. If they do they put it quite clearly.

In any case, a valid warning for anyone else who's reading this topic.
  Reply With Quote
Old 24th April 2013, 01:12 AM   #4
clm811 is offline clm811  United States
diyAudio Member
clm811's Avatar
Join Date: May 2002
Location: Northern California
I purchased and assembled the following(I double checked components and their placement):

Stereo Power Amplifier Kit for diy Ref MA-9S2 MA-9 Class AB/MA9-S2 clone 150W/150W@8ohm PowerAmp kit-high end MJL4281A+MJL4302A
through eBay.

MA9 S2 Clone 150W 150W 8ohm Poweramp Kit High End MJL4281A MJL4302A | eBay

I have questions about biasing and test voltages that are not given by seller.

Should the biasing pot(0-1kohms)adjustment (W1) be turned fully clockwise, counter-clockwise, or centered for initial power up/operating voltage testing?

I will be using an incandescent light bulb in series with the variac, then the transformer, rectifier, caps, then F1A fuses in series with the VCC and VSS rails; milliamp meters will be in series with each rail, and a voltmeter will probe across each 0.22 emitter resistor to determine the bias current(target is 50mA). Outputs and bias transistor are mounted on large heatsink.

I'm asking for your input before I power up(I'm wanting not to smoke the amp pcb nor the outputs).

Attached is the schematic given by the seller:

Attached Files
File Type: pdf M9 clone.pdf (92.1 KB, 379 views)

Last edited by clm811; 24th April 2013 at 01:17 AM.
  Reply With Quote
Old 24th April 2013, 01:20 AM   #5
diyAudio Member
Superstrand's Avatar
Join Date: Apr 2013
Location: Ohio
The Bennic cap looks nice, otherwise I am completely skeptical, will analyze the schematic and report back after a good night of sleep. Cheers.
  Reply With Quote
Old 24th April 2013, 03:55 AM   #6
diyAudio Member
Superstrand's Avatar
Join Date: Apr 2013
Location: Ohio
I looked it over because I can't sleep. This looks like a DIY-gene style eBay deal to me (just search former user 777 for a full commentary) If I am not mistaken (which, forgive me if I am) you are attempting to replicate a Marantz design. Why not build your own, or share in any of the wonderful designs made available by the kind Mr. Pass? I apologize, but I would find it difficult to contribute on this one, Best wishes.
  Reply With Quote
Old 4th June 2013, 12:25 AM   #7
diyAudio Member
Join Date: Jun 2013
I was just looking for this amp and stumbled on this site:

Pair 150W 1NJW0302G NJW0281 Stereo Amplifier AMP DIY Kit Ref Marantz MA-9S2

Is also refers: "This amplifier kit is reference to the circuit of MA-9S2, We also add feature on it, Direct current servo added to the circuit,That allow no neccessory to adjust the neutral point, Only several mV(less than 10mV) and can be ignored. We only need to adjust the static current, Just rotate the variable resistors to make the voltage on any one of 0.22Ohm resistor is between 10mV to 40mV, If you want to set it at Class A mode, Pls adjust the current larger than 100mV, But larger heatsink should be needed."

Maybe it helps if you haven't find anything better yet...
  Reply With Quote
Old 4th June 2013, 06:50 PM   #8
diyAudio Member
Join Date: Apr 2011
hi all, in the end someone mounted this kit?, he intended to buy one to see how quality has.
I want to put a preamp Denon Pra 1500 with this stage, believe that sound better than my current Denon amplifier PMA2000R?, greetings to all.
  Reply With Quote
Old 4th June 2013, 10:35 PM   #9
dangus is offline dangus  Canada
diyAudio Member
Join Date: May 2004
Location: Vancouver Island
If you have to pay new prices for a transformer and filter caps and case, it starts to add up to real money. Might be wiser to look for an off-the-shelf Chinese amp that can be upgraded, like the Behringer A500. Or a used, non-Chinese "studio amp" like the discontinued Yorkville SR300.
  Reply With Quote
Old 4th June 2013, 11:14 PM   #10
diyAudio Member
Join Date: May 2010
Location: Skokie Il
I have a whole power supply, case, heatsink, etc in an old power amp chassis. It even has LED VU meters. It was a Sony rated 135 watts RMS per channel into 8 ohms, so this kit might be a good deal for me, if I knew whether it was any good in the first place.
  Reply With Quote


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
DIAMOND DIFFERENTIAL INPUT POWER AMPLIFIER EBay kit janusz Solid State 156 20th January 2016 07:45 AM
LM3875 KIT from ebay vinodt1347 Audio Sector 8 1st December 2010 08:28 AM
Hi end DAC kit ebay Zero One Digital Line Level 132 15th May 2010 12:33 PM
Ebay Tube Preamp Kit bcrescen Tubes / Valves 10 2nd February 2008 12:33 PM

New To Site? Need Help?

All times are GMT. The time now is 12:27 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2