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

Solid State Talk all about solid state amplification.

DIY- and Holton's Lateral-amp problem
DIY- and Holton's Lateral-amp problem
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 15th October 2004, 12:30 AM   #1
Pelle is offline Pelle  Sweden
diyAudio Member
Join Date: May 2003
Location: Luleň
Default DIY- and Holton's Lateral-amp problem


A while ago I made a N-channel amplifier that was intended for use with +-35V. Now I have made a similar amp for +-70V and I have some problem. With no input the amp is stable and no sign of oscillation at the output at any rail voltage up to +-70V. But when I connect an input I get some random 'noise' at the output at about half a volt or so. The 'noise' is not constant in frequency but I would guess less than 100kHz by looking at the oscilloscope. This is clearly audible and it sounds like the speakers have a broken voice coil. The problem appears whether I have a speaker connected or not. I had similar problems with Holton's lateral amplifier when using IRF610 as VAS as he suggested. When changing back to MJE340 all problems disappeared. I'm currently using IRF610 as VAS and i'm wondering if substitute to MJE340 would help. I have also made it possible to add resistors to my amp, R17 and R20, that are currently being bridged.
Does anyone know what causes this phenomen?

Here are the two amplifiers, first mine and than Holton's lateral.

Click the image to open in full size.

Click the image to open in full size.

  Reply With Quote
Old 15th October 2004, 05:15 AM   #2
JensRasmussen is offline JensRasmussen  Denmark
diyAudio Member
JensRasmussen's Avatar
Join Date: Jul 2002
Location: Denmark - Jutland
Send a message via ICQ to JensRasmussen Send a message via MSN to JensRasmussen

Should C9 not go across the 22k top feedback resistor?

  Reply With Quote
Old 15th October 2004, 09:18 AM   #3
AndrewT is offline AndrewT  Scotland
Join Date: Jul 2004
Location: Scottish Borders
C9 across two stages (LTP & VAS) avoids the Miller cap problems. A nice solution chosen by many designers who claim this sounds better.
Try adding a pot in series with C9 & see if adjusting eliminates the spurious noise. try also adding a cap in parallel to this CR. how about a CR in parallel with M1 gate to -ve Vrail. Could the problem be noise input back into the NFB from the output leads? Adding the remainder of the zobel circuit would stop this.
  Reply With Quote
Old 15th October 2004, 09:38 AM   #4
peranders is offline peranders  Sweden
Electrons are yellow and more is better!
diyAudio Member
peranders's Avatar
Join Date: Apr 2002
Location: G÷teborg, Sweden
DIY- and Holton's Lateral-amp problem
Have you checked how your problem looks like with an oscilloscope? May I ask why you have chosen a MOSFET?

Can it be that you load the input stage too much with mosfet? Parasitic oscillations of the mosfet?
/Per-Anders (my first name) or P-A as my friends call me
Group buy: DCT03 DC trap for big toroidal transformers. Sign up for interest HERE. 35 pcb's in interest.
  Reply With Quote


DIY- and Holton's Lateral-amp problemHide 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
Bias control problem with n-channel amplifier (Anthony E. Holton) Hielke02 Solid State 4 1st May 2011 06:54 PM
hy mr holton retrosong Solid State 10 12th July 2007 07:17 PM
Holton Lateral Amp (Pic post) matth Solid State 12 7th September 2003 11:41 PM

New To Site? Need Help?

All times are GMT. The time now is 07:38 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio