Balanced shunt pot in front of a differential receiver - 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 9th September 2008, 09:33 AM   #1
00940 is offline 00940  Belgium
diyAudio Member
 
Join Date: Sep 2003
Location: Paris
Default Balanced shunt pot in front of a differential receiver

I don't really know in what forum to ask...

Can I put a simple shunt volume control in front of differential line receiver ? Just as attached, but without the two opamps buffering the inputs of the receiver. Any problems I might run into ?

It's to sum the outputs of a pcm1794 (after I/V conversion).
Attached Images
File Type: jpg balanced volume control.jpg (56.9 KB, 144 views)
__________________
Ben.
  Reply With Quote
Old 9th September 2008, 10:20 AM   #2
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
You would have to use low value resistors and a pot infront of the existing diff stage (inc resistors). This may mean that when the volume is attenuated a lot you place too much load on the driving stage.

Think of it as the same impednace problem with any passive pre-amp.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 9th September 2008, 11:43 AM   #3
00940 is offline 00940  Belgium
diyAudio Member
 
Join Date: Sep 2003
Location: Paris
What I had in mind:

4.7K resistors for the fixed resistors of the shunt and also 4.7K for the input resistor of the receiver. 22k resistors for the feedback around the opamp. A 10k stepped attenuator as shunt.

I can tailor the values of the attenuator to get true logarithmic attenuation. I'm not overly concerned by the current drawn by the shunt as the I/V stage is buffered by class A buffers iddling at 20ma. The whole thing is of course in the same box, no cables involved here.
__________________
Ben.
  Reply With Quote
Old 9th September 2008, 12:09 PM   #4
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
Doesn't sound too bad. There may be some funny curve characteristic due to interaction between the shunt and input resistors, but other than that OK I think.

Is there a reason you can't just use one side of the converter with a conventional unbalanced level control? As you seem to be ending up with an unbalanced output anyway.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  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
Balanced Driver / Receiver arigy Solid State 11 14th June 2010 09:26 AM
Marantz SR7200 receiver - problem with front 2 channels willick Solid State 1 28th July 2008 03:20 AM
Balanced interconnect to differential amp - how would you do it? zigzagflux Tubes / Valves 11 5th February 2008 02:36 AM
What front end for PP - triode, pentode, mu-stage or differential triodes? ray_moth Tubes / Valves 13 29th May 2007 08:02 PM
Balanced / Differential Input Question thylantyr Solid State 2 28th March 2003 09:27 PM


New To Site? Need Help?

All times are GMT. The time now is 11:07 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