Leach Amp Modification with Mosfet - 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 2nd November 2005, 05:08 PM   #1
diyAudio Member
 
Join Date: Jan 2005
Location: Hong Kong
Default Leach Amp Modification with Mosfet

Is it possible to use the Power Mosfet in Leach Amp ?

Thomas
  Reply With Quote
Old 3rd November 2005, 03:58 AM   #2
diyAudio Member
 
Join Date: Jun 2004
Location: Indore , India
You will have to change the output stage from current driven to voltage driven , you can also give higher voltage to the output mosfets than the rest of the circuit , I am attaching a diagram and I think this should work , only see that the drive voltage from the vas is at least 7volts .
Attached Images
File Type: jpg cnv0024.jpg (54.1 KB, 1324 views)
__________________
RL
  Reply With Quote
Old 4th November 2005, 06:59 AM   #3
Leolabs is offline Leolabs  Malaysia
diyAudio Member
 
Leolabs's Avatar
 
Join Date: Dec 2004
Location: Bukit Mertajam
Send a message via MSN to Leolabs
But does anyone try this before???
  Reply With Quote
Old 4th November 2005, 11:24 AM   #4
diyAudio Member
 
BobEllis's Avatar
 
Join Date: Sep 2003
Location: Upstate NY
Leach mentioned on his site that he tried it and did not like the sound.

If you want to try it, change the resistors in the Vbe multiplier to allow a bias adjustment range of 3-5 volts if you use vertical MOSFETs like the IRFP devices mentioned. You may be able to use lateral output devices without changing anything.

You'll lose some voltage swing due to the Vgs of the output devices. So, unless you run the front end and VAS at higher rails than the output stage you will lose some power compared to the original bipolar design on the same output rails.
  Reply With Quote
Old 4th November 2005, 11:45 AM   #5
diyAudio Member
 
Join Date: Jan 2005
Location: Hong Kong
Thanks you for your information !
How about adjust it into Class A Amp
with the orginal design ?

Thomas
  Reply With Quote
Old 4th November 2005, 12:07 PM   #6
diyAudio Member
 
BobEllis's Avatar
 
Join Date: Sep 2003
Location: Upstate NY
Ensure adequate heatsinking and turn the bias pot clockwise. you may want to add output device pairs.

Adequate can be quite large, depending on how high you want to go with class A bias. See the KSA50 thread for some ideas - although if you keep the rails around 60V, you'll want more than the KSA50 guys use. My modified A75s run 60 V output rails and have 40 fin 14"x10"x1.5" sinks per channel. This allows me to bias up to about 45 watts class A, with 200W dissipation and about 30C rise above ambient. You probably wouldn't be able to get that high on these sinks with only two pairs of output devices - watch junction temperatures.
  Reply With Quote
Old 4th November 2005, 01:22 PM   #7
diyAudio Member
 
Join Date: Jan 2005
Location: Hong Kong
Dear BobEllis & All,

Actually I am stand at the cross road to chose making Leach Amp with high bais, Krell 50 or Alpeh 2 !

Are any one has experience ?

Thomas
  Reply With Quote
Old 4th November 2005, 01:38 PM   #8
diyAudio Member
 
BobEllis's Avatar
 
Join Date: Sep 2003
Location: Upstate NY
I know at least one person has built a Leach, Krell and AX, perhaps Terry AKA Still4given can comment. His Leach amps are standard bias, though.

I have 4 channels of Leach (standard bias) and 4 of Pass/Thagard A75 (reduced bias to ~10W class A, but 60V rails). To my ears, the A75 is a little sweeter and more detailed sounding, with better bass control and power. The difference is not great (barely audible), and I am perfectly satisfied with my Leach amps in my bedroom system.
  Reply With Quote
Old 4th November 2005, 01:42 PM   #9
diyAudio Member
 
Join Date: Jan 2005
Location: Hong Kong
Would please intoduce Terry !
Please forwards my doubt to him !

Thanks !

Thomas
  Reply With Quote
Old 4th November 2005, 01:53 PM   #10
diyAudio Member
 
still4given's Avatar
 
Join Date: Oct 2004
Location: Victorville, CA
Hi Friend,

I have not quite finished my Aleph-X. As I was working on the case for it last night I got a chance to listen to quite a bit of music through the Leach and the Krell. The Leach is very detailed. It has really good bass and clear highs but the midrange may be a little too revealing. the Krell is just a joy to listen to. I'm hoping that the AX will be as good or better. The only draw back the Krell is the heat and fan noise. I don't have the Leach biased high. I used a Hafler Transformer in it so I probably can't go a lot higher. I may try bumping it up a bit more just to see if it will smooth out a little. I'd love to hear what someone thinks of a Class A biased Leach. If it works well I might consider replacing the trans in mine.

Blessings, Terry
__________________
X-BoSoZ, B1 Mezmerize, P101, Symasym, KSA 50, Aleph-X, Leach Low TIM, Leach Superamp, Dx MKIII, Super A, Honey Badger, JLH 1969, Gainclone. FetZilla, Peeceebee, VSSA PMI & jkuetemann, SKA GB150, Ovation nx & sx, AX&SX-14, TMG8, Slewmanster w/CFA-XH, Wolverine, Spooky, Symasui, Low TIM hybrid
  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
My Leach Amp Clone (LEACH 150) panson_hk Solid State 32 22nd May 2014 12:25 PM
High Current Leach/leach super amp bowdown Solid State 41 2nd March 2011 03:15 PM
BiCMOS Bipolar+MOSFET better than MOSFET lineup Solid State 5 8th December 2009 12:46 PM
Leach Superamp vs Leach 4.5 Samuel Jayaraj Solid State 4 26th October 2002 10:20 AM
Leach amp vs super Leach amp supernet Solid State 0 21st February 2002 11:16 PM


New To Site? Need Help?

All times are GMT. The time now is 11:42 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