SOAP MKIII (Simple OpAmp Pre) With onboard PSU - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 7th May 2008, 01:26 PM   #11
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Andrew, the circuit I posted was built as a pre between a Monica2 DAC and a Charlize amp. I did quite a lot of experimenting before I settled on the gain etc. And CarlosFM suggested the other tweaks.

As far as I know, it is still working fine for the guy I built it for and he was very happy with the sound quality (as was I). Neither OPA134 chip seemed to get hot.

Quote:
What is the minimum load impedance and maximum cable capacitance that the ClassA output stage can feed?
That I honestly can't tell you but perhaps I should add that it was running on +/-12 volt rails (SMPS).

(Full story here )
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 7th May 2008, 04:29 PM   #12
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Quote:
Originally posted by Nuuk
Here are some other tweaks that you may like to try too.

Click the image to open in full size.

Yes, it's the single version of the 2134 but the same applies.

I used 100uF/35v Panasonic for audio types on each power supply pin. The DC blocking was taken care of by caps in the DAC and the power amp.
Nuuk, this class A thing should be applied with care. Not every opamp will benefit from this and in your case seems 10 mA crazy. The opamp will run pretty hot and the gain is little.
__________________
/Per-Anders (my first name) or P-A as my friends call me
  Reply With Quote
Old 7th May 2008, 04:45 PM   #13
zei is offline zei  Sweden
diyAudio Member
 
Join Date: Feb 2005
Location: Gothenburg, Sweden
Quote:
yes C5 & C6 for decoupling. but do they need to be snubbed or electro//film or +ve to -ve or are ceramic OK?
I can,t see why ceramics should,nt work however i was thinking normal plastic types here. The 3D is showing the wrong kind..

On the prototype Micas are used...


/JZ
__________________
Tala är tiga, silver är guld
  Reply With Quote
Old 7th May 2008, 04:47 PM   #14
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Ceramics are very good if you do it right.
__________________
/Per-Anders (my first name) or P-A as my friends call me
  Reply With Quote
Old 7th May 2008, 04:52 PM   #15
zei is offline zei  Sweden
diyAudio Member
 
Join Date: Feb 2005
Location: Gothenburg, Sweden
All in all..

The SOAP sounds very good, is cheap and easy to build.

The onboard psu makes it very simple to put in a chassi etc..

I,m very pleased with the result.


I might even have a few boards "pro" made .


/JZ
__________________
Tala är tiga, silver är guld
  Reply With Quote
Old 7th May 2008, 06:30 PM   #16
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Andrew and Peranders,

I appreciate the concern and you guys are much more knowledgeable than I am.

I wouldn't use that set-up on any other opamp without consultation, but as I said already, it appears to have worked in the circuit shown without problem for a couple of years now without the OPA134's failing.

In fact, it sounded so good, if the opamps did need replacing each year, it would still be worth consideration IMHO.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 7th May 2008, 06:34 PM   #17
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
The temperature is probably not an issue but 10 mA + equally much at positive signals plus the load will result in 20 mA at least and this is rather much for the opamp if you want ultra low distortion. Try to do a blind test with and without this circuit. Can you pick the difference if you use a good opamp.
__________________
/Per-Anders (my first name) or P-A as my friends call me
  Reply With Quote
Old 7th May 2008, 06:54 PM   #18
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi Nuuk,
12V gives just 8mA of bias and that adds about 90mW of dissipation to a 134.
Survivable in the longer term.

But 15V and 2134 and suddenly the extra dissipation is up around 280mW. That gets the opamp into a completely different temperature regime.
__________________
regards Andrew T.
  Reply With Quote
Old 7th May 2008, 07:08 PM   #19
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Thanks Andrew,

I have now added a note attached to that circuit that it should not be used with a higher voltage supply.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 7th May 2008, 08:47 PM   #20
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
You can use a class A circuit at higher voltages but you'll have to choose the current with taste.
__________________
/Per-Anders (my first name) or P-A as my friends call me
  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
A Simple opamp question? Dxvideo Chip Amps 29 3rd April 2009 02:42 PM
SOAP - Simple OpAmp Pre zei Chip Amps 14 12th December 2007 03:15 AM
Looking for Simple 12V supply dual opamp for kid's project chipco3434 Chip Amps 26 16th March 2006 08:13 PM
Designing a simple tube opamp? bradd Tubes / Valves 1 26th October 2005 07:24 AM


New To Site? Need Help?

All times are GMT. The time now is 10:49 AM.


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