The Heathkit MA-12 - A Mullard 5-10 In Disguise - Page 9 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 30th April 2012, 12:17 AM   #81
kevinkr is offline kevinkr  United States
diyAudio Moderator
kevinkr's Avatar
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Widerangesound, those amps look great, and having worked on various Leak Amps I expect they sound similar and just as good!
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
  Reply With Quote
Old 20th June 2012, 02:39 PM   #82
diyAudio Member
Join Date: Jun 2012
Hi Guys!
First time post, not an expert but know a little bit about this amp.
I had a pair and wish I had kept them - they were superb. I replaced all the caps with new (an easy job - it's all hard wired) and the resistors with equivalent 2W types to keep thermal noise down. I found a great improvement in the sound quality by removing the feedback resistor bypass capacitor - these things really sang! I didn't experience and problems with oscillation as a result but that was just my experience and I am no expert. I sold them to a friend to bring him into the valve community and he has enjoyed them ever since!
Very Best to All,
Graham (aka That Radio Thing)
  Reply With Quote
Old 20th October 2012, 06:46 PM   #83
diyAudio Member
The Space Egg Corp's Avatar
Join Date: Sep 2010
Location: London & Miami
Blog Entries: 13
Hi Graham

Nice tip on removing the feedback cap, thanks.
Is it the MA-12's you had ?

I just caught up on the thread, having started to look at mine again.
Issues with the chassis' resolved...
...simply need a bigger chassis / s.

Has anyone tried dropping in a few motor-run caps, here & there ?

Any good tips from peoples, on any aspect of refurbing MA-12's / Mullards, most welcome...
...the refurb. cometh !!!



Nice builds Wide Range Sound...
...coooool !

Leaks are great Kevin...
...especialy with gravy !

  Reply With Quote
Old 20th October 2012, 08:07 PM   #84
diyAudio Member
The Space Egg Corp's Avatar
Join Date: Sep 2010
Location: London & Miami
Blog Entries: 13
Talking MA-12 Schematic...again...+ PICS !!!!

Hi Vacuum heads !

( there's no air, in there ! )

Just thought I'd bung the schematic up again, as it was a few pages back.

4mm test-points near the valves...?



Slightly concerned that if I add regulated heater supplies, the transformer might be a bit pushed.
When they were last 'fired-up' it did get rather warm.
Maybe a small extra transformer for the 'teeny-toob' driver heaters could be good ?


  Reply With Quote
Old 8th October 2014, 12:56 PM   #85
diyAudio Member
Join Date: Oct 2014
Location: Yorkshire
*ahem* Noob here!

I have a full MA12 instruction manual (including a full sheet schematic I think)

I'll need to scan it - only if there is enough interest!

However, I'm looking for a replacement output transformers for my MA12 pair (and TBH the mains tx too) Any ideas if there is an "off the shelf" - the OP tx is marked as as a RADFORD and not a mullard.

Now, back to reading...

  Reply With Quote


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
Heathkit Oscilloscope O-12 Pure_Brew Equipment & Tools 25 14th September 2010 06:22 AM
Looking for Heathkit O-12 manual/schematic Pure_Brew Equipment & Tools 1 27th July 2010 03:13 AM
Mullard 5-10 for guitar use? gottlieb Instruments and Amps 1 6th January 2010 09:44 PM
For Sale - 10 Mullard EL84 andyjevans Swap Meet 1 3rd January 2010 04:12 PM
ceramic filter SFA 10.7 MA schnullimaus Parts 0 12th August 2007 03:08 PM

New To Site? Need Help?

All times are GMT. The time now is 01:20 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2