What is the purpose of NE5534 in this amp - 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 10th April 2005, 04:29 PM   #1
Gasho is offline Gasho  Croatia
diyAudio Member
 
Gasho's Avatar
 
Join Date: Nov 2004
Location: Zagreb
Default What is the purpose of NE5534 in this amp

Here is shematic.
Attached Images
File Type: jpg azur640asch.jpg (88.8 KB, 712 views)
  Reply With Quote
Old 10th April 2005, 04:53 PM   #2
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
The NE5534 is a DC servo but the output isn't drawn correctly. The output isn't connected to any load.

I have a similar servo in my QRV-03 amp.
__________________
/Per-Anders (my first name) or P-A as my friends call me
  Reply With Quote
Old 10th April 2005, 04:55 PM   #3
boholm is offline boholm  Denmark
diyAudio Member
 
boholm's Avatar
 
Join Date: Apr 2004
Location: Copenhagen
It looks to me to be a DC servo.
__________________
Best regards
Bo
  Reply With Quote
Old 10th April 2005, 05:16 PM   #4
Gasho is offline Gasho  Croatia
diyAudio Member
 
Gasho's Avatar
 
Join Date: Nov 2004
Location: Zagreb
Hmmm, if it´s DC servo , why I must to put a trimpot i series with R2 (connecting input with ground) to trim the DC on output.

  Reply With Quote
Old 10th April 2005, 05:21 PM   #5
Netlist is offline Netlist  Belgium
diyAudio Moderator Emeritus
 
Netlist's Avatar
 
Join Date: Jan 2003
Hmm...the image reads "Redrawn".
Could someone have made a mistake?

/Hugo
  Reply With Quote
Old 10th April 2005, 05:22 PM   #6
moamps is offline moamps  Croatia
diyAudio Member
 
Join Date: Oct 2002
Location: Croatia
Default Re: What is the purpose of NE5534 in this amp

Quote:
Originally posted by Gasho
Here is shematic.
A kind of an unconnected overload detector (diff.amp).

Quote:
Originally posted by peranders
The NE5534 is a DC servo but the output isn't drawn correctly.
Where in your opinion should the output be connected?
Take a look at RC values.

Regards,
Milan
  Reply With Quote
Old 10th April 2005, 05:23 PM   #7
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Quote:
why I must to put a trimpot i series with R2
Because you can make life difficult or easy for an opamp.
__________________
The buck stops Here
  Reply With Quote
Old 10th April 2005, 05:34 PM   #8
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
I second Moamps. Opamp measures diff volts across LTP with a gain of about 50. But the output circuit is missing. A LED or relay?
__________________
regards Andrew T.
  Reply With Quote
Old 10th April 2005, 05:50 PM   #9
Gasho is offline Gasho  Croatia
diyAudio Member
 
Gasho's Avatar
 
Join Date: Nov 2004
Location: Zagreb
So if I rise value of feedback resistor R65 (from 33K to 50K) to make amplifier with smaller NFB , and put trimpot(20k) in series with R2 to correct output DC offset , will I change the overload protection point?
  Reply With Quote
Old 10th April 2005, 06:31 PM   #10
ilimzn is offline ilimzn  Croatia
diyAudio Member
 
Join Date: Feb 2005
Location: Zagreb
The schematic appears to have many errors, the unconnected output of the NE5534 is only one - the connection of the 'clip detect' and output transistors does not make much sense, for instance.

The 5534 seems to be a clip detector, but the output is drawn unconnected. The reason DC offset voltage changes when you change the resistor is that the combined bias current of the NE5534 (which is quite high, BTW) and the amp itself develops different voltages at the differential pair inputs, and you get this difference as an output offset. It remains a mystery why anyone would use a NE5534 in this application, but I guess if every chip in the amp is a NE5534, economy of scale applies - it may just have been the least expensive to use.

As for your proposal to reduce NFB - this also increases closed loop gain, from roughly 34 to 51, which also reduces bandwidth in proportion, and increases distortion. Why would you want to do this?
If you want to reduce NFB (which is not something to be done unless you know exactly what you are doing and why), you need to reduce open loop gain and keep closed loop gain the same. There are a number of ways you could do this on this amp, and the best ones have nothing to do with R65. If you are competent enough to arrive at the decision that NFB should be reduced, you should easily be competent enough to know what these methods are, and which one is the best to use.
  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
The NE5534....misunderstood? TimA Solid State 102 8th December 2010 03:23 AM
NE5534 with a new front end ...anybody? ashok Solid State 9 2nd June 2006 02:30 AM
NE5534 compensation ? AndrewT Solid State 22 12th February 2006 11:42 PM
Wtb Philip Ne5534 goto2003 Chip Amps 0 28th December 2005 04:37 PM
NE5534 questions Wolvatron Chip Amps 6 20th January 2004 02:32 PM


New To Site? Need Help?

All times are GMT. The time now is 03:03 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