Balanced "SEWA" on steroids - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 31st March 2008, 09:37 AM   #1
Fuling is offline Fuling  Sweden
diyAudio Member
 
Join Date: Aug 2001
Location: Sweden (Mora)
Default Balanced "SEWA" on steroids

Hi

Last weekend me and a friend visited a radio amateur fleamarket and brought home a serious amount of "junk".
Personally I got four big heatsinks (something like 15x3x100cm, new in good shape), 30 pcs 12R 25W power resistors (the alu housed type) and a stash of 1000uF 63V caps (HQ Philips) along with some tube related stuff.
The funny thing is that the night before we went there we sat with a couple of brews and discussed the possibility of using full length heatsinks to build two tower-like power amps that could be hidden behind the speakers. 12 hours later I got these four 1 meter sinks for peanuts

The plan goes as follows:
Each heatsink would hold 2x IRFP260 power mosfets and 6x 12R resistors wired in a series-parallell combo to make an 8R 150W resistor. These four units would then be bolted together in pairs (monoblocks) and connected as balanced followers with bipolar asymmetrical power supplies.
By using +14 and -28V the inputs (gates) could be kept at ground potential (no coupling caps), the outputs would then be a few volts negative (-4V)
This would put 18V across each Mosfet and 24V across the resistors, so Ohms Law sets the bias to 3A per "leg".
Quite elegant if I may say so myself...

Attached Images
File Type: jpg follower1.jpg (28.7 KB, 979 views)
  Reply With Quote
Old 31st March 2008, 02:17 PM   #2
diyAudio Member
 
HIPCHECK's Avatar
 
Join Date: Jun 2004
Location: ARKANSAS
This is funny, I have several projects in the works, I have a huge Son of Zen waiting for the money to buy a large transformer. I hooked up a source follower off the 8ohm lower legs with some irfp260 and tortore tested my heatsink/resistors to see if I could dissipate the heat I would require for a 20-30w SOZ. the final amp is running some irfp460 that I have sourced from pulled(dead) equipment.

I was thinking of how to graft a Jfet input pair (the new flavor around here) onto a source follower like this to make it a "complete" amp"? I have a small pile of Dale RH-50 7.5R left to make a mini follower style amp!

I enjoyed this source follower style as a a headphone amp for a few months!Click the image to open in full size.
Attached Images
File Type: gif zenfollo_thumb.gif (952 Bytes, 580 views)
__________________
If a inch of duct tape will fix it, 3 feet should fix it for life!!!!
  Reply With Quote
Old 31st March 2008, 03:04 PM   #3
Fuling is offline Fuling  Sweden
diyAudio Member
 
Join Date: Aug 2001
Location: Sweden (Mora)
I thought about building a Son of Zen for a while, but I already have a small(ish) XSOZ so I decided that I dont need another one.
The resistor loaded follower feels like a good idea as I got the heatsinks and the resistors almost for free. Various CCS-loaded designs, both followers and gain stages, has crossed my mind but nothing would beat the balanced follower when it comes to simplicity.
If i build the follower Ill probably use tubes for phase splitting and voltage gain.

Right now Im looking for a place to get M3 hex head bolts locally, the heatsinks has T-shaped slits along the edges that allows assembly with hidden screws = less holes to drill.
  Reply With Quote
Old 31st March 2008, 03:41 PM   #4
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
just a thought ...

why don't you use one CCS instead of resistors ?
certainly more elegant solution , you'll have all virtues of LTP and even less dissipation for same power ;

I presume that power isn't an issue
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 31st March 2008, 03:57 PM   #5
Fuling is offline Fuling  Sweden
diyAudio Member
 
Join Date: Aug 2001
Location: Sweden (Mora)
Constant current sources would certainly be more efficient, but resistors are...cooler
  Reply With Quote
Old 31st March 2008, 04:32 PM   #6
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Quote:
Originally posted by Fuling
Constant current sources would certainly be more efficient, but resistors are...cooler

__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 31st March 2008, 04:39 PM   #7
Fuling is offline Fuling  Sweden
diyAudio Member
 
Join Date: Aug 2001
Location: Sweden (Mora)
Of course; the fact that I bought a bag with 30 resistors for ~15 bucks has something to do with the choice of source load...
  Reply With Quote
Old 9th April 2008, 08:39 PM   #8
Fuling is offline Fuling  Sweden
diyAudio Member
 
Join Date: Aug 2001
Location: Sweden (Mora)
The biggest post in the budget for this project seems to be bolts, nuts and washers:
Attached Images
File Type: jpg follower1,3.jpg (94.2 KB, 665 views)
  Reply With Quote
Old 20th April 2008, 08:53 AM   #9
diyAudio Member
 
HIPCHECK's Avatar
 
Join Date: Jun 2004
Location: ARKANSAS
any progress?

I used small rivets on my resistors to make things easy.
__________________
If a inch of duct tape will fix it, 3 feet should fix it for life!!!!
  Reply With Quote
Old 20th April 2008, 02:53 PM   #10
Fuling is offline Fuling  Sweden
diyAudio Member
 
Join Date: Aug 2001
Location: Sweden (Mora)
No progress the last few weeks. The weather has been too nice to stay indoors
  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
Mr White's "Opus", designing a simple balanced DAC Russ White Twisted Pear 1954 8th May 2014 07:36 PM
600 ohm resistor between "+" and "-" of balanced inputs. skpb Analog Line Level 3 20th October 2006 12:38 PM


New To Site? Need Help?

All times are GMT. The time now is 11:54 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