Go Back   Home > Forums > >

Solid State Talk all about solid state amplification.

Class A Mosfet Amplifier and PS
Class A Mosfet Amplifier and PS
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
Old 12th November 2007, 05:34 AM   #1
Kinnja is offline Kinnja  United States
diyAudio Member
 
Join Date: Jan 2007
Default Class A Mosfet Amplifier and PS

Hello,

This is my first project built without a kit, and my fourth ever.

Here is the link: http://diyaudioprojects.com/Solid/ZCA/index.htm

I'll attach the amp schematic on this post, and the power supply schematic on the next one. The above web site has been unavailable at times the last few days.

I would be grateful for any answers or advice.

--One resistance is shown as 15R/40W, could I use four 60 Ohm, 10W resistors connected in parallel here?

--Where the wattages of the resistors are not specified, does it matter, or would a half or quarter watt be ok?

--What voltage should the capacitors be, or does it not matter?

--How important is it to match the exact capacitance on the schematic, is it ok to go a little higher or lower?

--Is it ok to connect smaller caps in parallel to get larger cap values?
Attached Images
File Type: png sch_zca.png (4.3 KB, 6785 views)
  Reply With Quote
Old 12th November 2007, 05:42 AM   #2
Kinnja is offline Kinnja  United States
diyAudio Member
 
Join Date: Jan 2007
Here is the Power Supply schematic.

--Same questions about the caps, would it be ok for example to replace the low ESR 450uF cap with a low ESR 470uF?

--And do the cap voltages matter?

--What specs to I look for in a transformer for this power supply?

Thanks
Attached Images
File Type: png zcaps.png (2.7 KB, 5705 views)
  Reply With Quote
Old 12th November 2007, 09:12 AM   #3
Luke is offline Luke
diyAudio Member
 
Join Date: Sep 2001
hi Kinnja

before you decide on this design, are you aware this thing outputs somewhere between 5-10 watts of power? That means you need really efficent speakers to get the best out this amp.


Quote:
"--One resistance is shown as 15R/40W, could I use four 60 Ohm, 10W resistors connected in parallel here?"
yes

Quote:
"--Where the wattages of the resistors are not specified, does it matter, or would a half or quarter watt be ok?"
The schematic says to use 0.5 watt reistors unless marked.

Quote:
"--What voltage should the capacitors be, or does it not matter?"
The rails are 24 volts, so if you use 35V or more all should be well.

Quote:
"--How important is it to match the exact capacitance on the schematic, is it ok to go a little higher or lower?"
yes can vary a bit and wont make much difference.

Quote:
"--Is it ok to connect smaller caps in parallel to get larger cap values?"
yes

Quote:
"--What specs to I look for in a transformer for this power supply?"
Typically you would use a transformer rated at minimum twice the power that a class A amp consumes, preferably 3 times. The author states the amp comsumes 60watts but i think its more like 40, so 120VA to 180va should work fine, even bigger is better.

good luck and hope it sounds good:-)
  Reply With Quote
Old 12th November 2007, 08:20 PM   #4
Tom2 is offline Tom2  United States
diyAudio Member
 
Join Date: Jun 2004
Location: Central CA
Kinnja,

I believe there is a mistake on the power amp schematic.
The polarity of 33uF tantalum cap is backwards.
The positive connection of the cap should connect to the 100k wiper.
You should email (Mark Houston) to confirm this.

Tom
  Reply With Quote
Old 12th November 2007, 09:14 PM   #5
Minion is offline Minion  Canada
diyAudio Member
 
Join Date: May 2006
Location: Cowican Bay , vancouver island
I think this amp actually only puts out 1w of power, at least that is what the Site says.....The Design is very simular to the Mosfet Headphone driver accept useing a Lateral Mosfet....
  Reply With Quote
Old 13th November 2007, 03:41 AM   #6
Kinnja is offline Kinnja  United States
diyAudio Member
 
Join Date: Jan 2007
Quote:
Originally posted by Luke
hi Kinnja

...before you decide on this design, are you aware this thing outputs somewhere between 5-10 watts of power?...

Typically you would use a transformer rated at minimum twice the power that a class A amp consumes, preferably 3 times. The author states the amp comsumes 60watts but i think its more like 40, so 120VA to 180va should work fine, even bigger is better....

Quote:
Originally posted by Tom2
Kinnja,

I believe there is a mistake on the power amp schematic.
The polarity of 33uF tantalum cap is backwards.
The positive connection of the cap should connect to the 100k wiper.
You should email (Mark Houston) to confirm this.

Tom

Quote:
Originally posted by Minion
I think this amp actually only puts out 1w of power, at least that is what the Site says.....The Design is very simular to the Mosfet Headphone driver accept useing a Lateral Mosfet....
All the info is very much appreciated. I'll send him an email about that cap. Its ok if the amp does only put out 1W, I want to hear a Class A amp, and I would like some high efficiency speakers anyway.
  Reply With Quote
Old 13th November 2007, 04:47 AM   #7
Luke is offline Luke
diyAudio Member
 
Join Date: Sep 2001
all that effort for 1 watt , hope its a good watt
  Reply With Quote
Old 15th November 2007, 05:40 AM   #8
Kinnja is offline Kinnja  United States
diyAudio Member
 
Join Date: Jan 2007
Quote:
Originally posted by Luke
all that effort for 1 watt , hope its a good watt

One watt isn't much is it? The actual number should be around 5W. On the web page he says he burns up over 60W to get 5W Class A.
  Reply With Quote
Old 15th November 2007, 05:49 AM   #9
Kinnja is offline Kinnja  United States
diyAudio Member
 
Join Date: Jan 2007
Quote:
Originally posted by Tom2
Kinnja,

I believe there is a mistake on the power amp schematic.
The polarity of 33uF tantalum cap is backwards.
The positive connection of the cap should connect to the 100k wiper.
You should email (Mark Houston) to confirm this.

Tom
I sent an email, I haven't heard back from him yet but its only been a couple days.

I also noticed that the positive terminal of the speaker is connected to ground. If I build it as is, I guess I can get a cheap speaker, and stand clear of that cap when I plug it in. Hopefully only the cap would get fried. On the web site, he has an article by someone who built the amp, and he didn't say anything about any mistakes on the schematic though.

http://diyaudioprojects.com/Solid/Cl...sfet/index.htm
  Reply With Quote
Old 15th November 2007, 08:04 AM   #10
Tom2 is offline Tom2  United States
diyAudio Member
 
Join Date: Jun 2004
Location: Central CA
Kinnja,

The schematic on the website looks correct now. (fixed?)
The positive of the 33uF now goes to the 100k wiper.

Tom
  Reply With Quote

Reply


Class A Mosfet Amplifier and PSHide this!Advertise here!
Thread Tools

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
mosfet class a/ab amp p robertson Solid State 30 9th February 2010 12:07 PM
NX400 - 400W RMS@4Ohms Lateral Mosfet Power Amplifier Module by Class-D for sale magnum_1 Swap Meet 16 13th June 2009 04:59 PM
Small Power D class MOSFET Amplifier Needed!! Kazus Class D 8 12th March 2009 03:58 PM
Class Mosfet power amplifier circuit Agus Widarto Pass Labs 16 18th February 2008 05:06 PM
JLH Class-A in a with MOSFET's tschrama Solid State 3 10th February 2002 04:23 PM


New To Site? Need Help?

All times are GMT. The time now is 11:45 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki