Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

Gainclone with transformer input question
Gainclone with transformer input question
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
Thread Tools Search this Thread
Old 26th July 2012, 01:17 AM   #1
AmadeusMozart is offline AmadeusMozart  New Zealand
diyAudio Member
Join Date: Oct 2009
Location: New Zealand
Default Gainclone with transformer input question

Honorable members, I've collected the parts for building the inverted gainclone with the LM1875; there was some cheap offering on eBay PCB and all parts. After the kit arrived I checked the layout and was not happy about one channel - some compromises in layout had been made and the output connection was running too close to the input connection for my liking. I decided to use only half of the board (with the proper layout) and get another board and use only that half of the board that has the proper layout part. This has the result that a) the layout is optimum and b) each has their own rectifier and DC smoothing resulting in less crossover issues.

This amplifier is going to be driven by a computer and I have had problems with another amplifier in the past with a groundloop which I never totally got rid off. I managed to score on eBay at an acceptable price (to me) some Beyerdynamic input transformers and want to use those to minimize hum and buzz.

I'll be using a low impedance output from the computer (many soundcards seem to use the headphone output as the line output but I am not to concerned about that - the iPod and the Cowan D2+ are doing the same) and the transformer has a 1:5 ratio, input 200 ohm, secondary 5K.

1) Since the inverted gainclone has a feedback loop of 10K/220K does this mean the input impedance of the gainclone is 10K?
2) Do I need to put some loading resistor accross the secondary (e.g. 10K) to ensure the load is the same as the 5K output impedance?
3) input voltage from e.g. a CD player will be too much and the input impedance will be very low: can I just put a resistor in series with the primary to use that as an attenuator or do I need to put a resistor accross the primary in addition to the series resistor when I do this?
4) In light of question 3: Can I just swap the transformer around and use the scondary (5K) as input and the primary as output (200 Ohm), does it matter?

Many thanks in advance

Last edited by AmadeusMozart; 26th July 2012 at 01:22 AM.
  Reply With Quote
Old 26th July 2012, 04:54 PM   #2
Arty is offline Arty
diyAudio Member
Join Date: Feb 2011
use a good opamp as buffer, then most probably whatever input impedance will suit You.
  Reply With Quote


Gainclone with transformer input questionHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
input transformer and impedance question milen007 Tubes / Valves 12 12th November 2014 12:50 PM
Input transformer topology question zigzagflux Tubes / Valves 13 6th December 2011 08:00 PM
Lundhal line input transformer question... sklimek Parts 9 11th January 2011 07:43 PM
Multiple Channel gainclone (transformer question) llmobll Chip Amps 4 4th September 2008 11:41 AM
First Gainclone. AX-730 Transformer Question. bezel6 Chip Amps 14 22nd January 2006 10:08 PM

New To Site? Need Help?

All times are GMT. The time now is 03:30 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio