A small question... maybe not - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 17th June 2003, 12:15 AM   #1
diyAudio Member
 
Join Date: Oct 2002
Location: Israel
Question A small question... maybe not

Hi all,

I'm aiming at a fully balanced amp which can receive both SE and balanced signals (if it's possible at all).

Hence,I was wondering - what happens if you feed an SE signal into a fully balanced amplifier? Do you need to add an input relay/switch that will short the negative pole of the XLR input to ground?

OR

If i feed a balanced amp an SE signal then since the portion of the diff. amp that was supposed to recieve the inverted signal (- of the XLR) see's 0V of input then the diff. amp will amplify the incoming SE signal as the difference between the SE signal arriving and the 0V on the negative pole?

OR

none of the above?

I hope you understand what i mean - i'm finding it difficult to put it more clearly for some reason

Cheers,
Guy.
  Reply With Quote
Old 17th June 2003, 12:40 AM   #2
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
It depends on the topology of the balanced amp. Some will take care of it for you, others will have distortion problems. The easiest way around that conundrum is to build a simple (one chip or two transistors) unbalanced to balanced converter. Or for more $$$ and less bandwidth (may or may not be a good thing), use an input transformer.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 17th June 2003, 08:01 AM   #3
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Default Unbalanced source to balanced amp

Your balanced amp will probably have a transformer or differential (LTP) input.
In that case it's fine to connect an unblanced signal to the + input and unbalanced gnd to the - input (or vice versa).
Of course you loose the balancing benefits.
Sometimes it helps to add a decoupling cap between the unbalanced gnd (shield) and the amp signal gnd. I have used 100n previously. This improved the overall s/n.
Example from
http://www.dhaen.org.uk/vdocs/845.gif
Attached Images
File Type: gif ltp.gif (3.2 KB, 125 views)
  Reply With Quote
Old 18th June 2003, 02:42 PM   #4
diyAudio Member
 
Join Date: Oct 2002
Location: Israel
Hi,

Thanks for both your replies - is there some a priori way to see if it can work (without an input traffo)?

Cheers,
Guy.
  Reply With Quote
Old 18th June 2003, 02:49 PM   #5
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Yes, just try it. If you've got a scope and a generator, you can see directly whether or not it will work. If not, use music and listen- the distortion will be obvious. There's little to no danger of breaking anything by trying this.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  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
hello! :) and a small question theblackknight Solid State 14 1st September 2007 02:18 PM
I want to start small, have a question about a toroid beerman Chip Amps 6 28th February 2007 09:38 AM
Small question about boats and rivers Netlist The Lounge 2 16th May 2006 12:56 AM
Small value resistor question Thomas001 Multi-Way 4 14th January 2005 02:15 AM
newbie question theil small psychosteve Multi-Way 9 1st October 2004 03:18 PM


New To Site? Need Help?

All times are GMT. The time now is 12:11 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