NAP-140 Clone Amp Kit on Ebay - Page 51 - 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 24th February 2010, 04:44 AM   #501
diyAudio Member
 
Join Date: Sep 2008
Hi Gaborbela, thanks for the answer. I read about the differential HFE. I have two issues though 1) I'm not sure how to measure hfe with a dmm. 2) I hate to mess around with the board, desoldering transistors since it actually works and sounds very nice. Is there anything else that can be done? (adding cap at the output?). Is 63-69mv abnormal and too much for the speaker drivers?
  Reply With Quote
Old 24th February 2010, 05:13 AM   #502
Ruwe is offline Ruwe  Europe
diyAudio Member
 
Join Date: Aug 2008
Location: Vancouver, Canada
Quote:
Originally Posted by marcel5996 View Post
Hi Gaborbela, thanks for the answer. I read about the differential HFE. I have two issues though 1) I'm not sure how to measure hfe with a dmm. 2) I hate to mess around with the board, desoldering transistors since it actually works and sounds very nice. Is there anything else that can be done? (adding cap at the output?). Is 63-69mv abnormal and too much for the speaker drivers?
Hi,

IMO, 65mV is not that much. If you like values closer to 0mV, the input transistors have to be hfe matched.
Avondale recommends T1 hfe to be 10% bigger than T2, which is beneficial for the balance with audio signals (less distortion), but will spoil a little bit the 0mV output. May be that's what happened when you replaced the transistors. I guess the first pair was better matched, even though unintentionally.
Also the input resistors combination must be equal (or very close) to the 27k that's in the feedback path. You can tweak the values slightly for better results. For example instead of 24k+2.7k you could use 24k+3k. It's easier to replace a resistor than a transistor.

Regards.
  Reply With Quote
Old 24th February 2010, 05:23 AM   #503
diyAudio Member
 
Join Date: Sep 2008
Thanks Ruwe, you always get to the point. That's exactly what I was looking for. Replacing a resistor worries me less than a three-lead transistor! When I feel courageous enough, will try the supplied BC550, to see if they're better matched
  Reply With Quote
Old 24th February 2010, 05:50 AM   #504
diyAudio Member
 
Join Date: Sep 2005
Default I'm not sure how to measure hfe with a dmm.

Quote:
Originally Posted by marcel5996 View Post
Hi Gaborbela, thanks for the answer. I read about the differential HFE. I have two issues though 1) I'm not sure how to measure hfe with a dmm. 2) I hate to mess around with the board, desoldering transistors since it actually works and sounds very nice. Is there anything else that can be done? (adding cap at the output?). Is 63-69mv abnormal and too much for the speaker drivers?
Hello
That is the problem !
You must match those two transistors as close as possible . Matching the LTP can improve the sound also (a little bit)
Do not use capacitors on the output !!
Actually if you like the sound you can leave it how is it . That offset is acceptable .
Just check the offset after the amplifier warm up . If the offset increase that would be a bigger problem .
On your DMM here is some small holes and marked PNP & NPN that is for measure the transistors hFE .
Some transistor PNP & some NPN , U have to use those holes which category the transistor belong . You can find the transistor info on the net .
For exam. BC546B Data , and you can get the information if is PNP or NPN .
Please do not be afraid , you can not damage the transistor while U measure the hFE .
I dont know what type of DMM you have .
Most DMM has access to measure transistor hFE .

Greets
Attached Images
File Type: jpg IMG_0001.JPG (50.1 KB, 1074 views)
File Type: jpg IMG_0002.JPG (106.9 KB, 1042 views)
  Reply With Quote
Old 24th February 2010, 01:19 PM   #505
juluska is offline juluska  Ukraine
diyAudio Member
 
Join Date: May 2008
photos of my amplifier just completed:
ignatius little projects
  Reply With Quote
Old 24th February 2010, 03:34 PM   #506
diyAudio Member
 
Join Date: Oct 2008
Default Nice NAP140

Hi,

I notice that the Q5 did not attach to heat sink. In summer, at loud volume, the power transistor could heat up very quick and destroy itself. It is called thermal-run-away.

Just my observation.

Lou

Quote:
Originally Posted by juluska View Post
photos of my amplifier just completed:
ignatius little projects
  Reply With Quote
Old 24th February 2010, 04:47 PM   #507
juluska is offline juluska  Ukraine
diyAudio Member
 
Join Date: May 2008
Quote:
Originally Posted by kclusa@yahoo.co View Post
Hi,

I notice that the Q5 did not attach to heat sink. In summer, at loud volume, the power transistor could heat up very quick and destroy itself. It is called thermal-run-away.

Just my observation.

Lou
I've tested it for hours at high volumes (high enough to go deaf) with DJ sessions without heating problems in q5. I appreciate the advise, this summer I will observe how it behaves.
Thanks
  Reply With Quote
Old 24th February 2010, 05:46 PM   #508
2Bak is offline 2Bak  Denmark
diyAudio Member
 
Join Date: Apr 2002
Good looking amp. Nice implementation of potentiometer and input selector at the rear.

How does it sound?

Quote:
Originally Posted by juluska View Post
photos of my amplifier just completed:
ignatius little projects

Last edited by 2Bak; 24th February 2010 at 06:11 PM.
  Reply With Quote
Old 24th February 2010, 05:55 PM   #509
diyAudio Member
 
Join Date: Oct 2008
Default Q5

Hi,

Sorry, I was not making it clear.

Q5 is responsible to bias 2sc5200 and TIP transistor and if heat sink temperature rise, Q5 will sense the heat, and Q5 Vce will drop and reduce the current of these 4 transistors.

Q5 will ensure thermal stability of these 4 transistors.

Q5 itself wil never over heat.

Lou

Quote:
Originally Posted by juluska View Post
I've tested it for hours at high volumes (high enough to go deaf) with DJ sessions without heating problems in q5. I appreciate the advise, this summer I will observe how it behaves.
Thanks
  Reply With Quote
Old 24th February 2010, 06:21 PM   #510
juluska is offline juluska  Ukraine
diyAudio Member
 
Join Date: May 2008
Quote:
Originally Posted by 2Bak View Post
Good looking amp. Nice implementation of potentiometer and input selector at the rear.

How does it sound?
It sounds very well, very correct amplifier.
  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
GB - F5 Clone suds Group Buys 3 23rd August 2010 01:03 PM
Tube Preamp 'Clone' PCB copys on ebay (Marantz, McIntosh, etc) powertriode Tubes / Valves 57 11th August 2007 07:59 PM
Question regarding ProAc 2.5 Clone and Tempo 2 Clone zoooh Multi-Way 5 11th March 2003 08:19 PM


New To Site? Need Help?

All times are GMT. The time now is 09:09 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