1 Watt Mullard amp: form Ger to Si - 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 15th March 2011, 11:05 AM   #1
tca is offline tca  Portugal
diyAudio Member
 
tca's Avatar
 
Join Date: Jan 2011
Location: Lisboa
Default 1 Watt Mullard amp: form Ger to Si

Hi,
I've just build a 1 watt Mullard amplifier from the Mullard book "Transistor Audio and Radio circuits" (1st Ed.) but replacing the germanium AC128 and AC127 transistors to silicon transistors TIP32 and TIP31.

The sound is ok, but can anyone suggest any modifications to optimize the use of the silicon transistors?

All the best.
  Reply With Quote
Old 15th March 2011, 12:20 PM   #2
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
You should replace the interbase resistors by two 1N400x diodes.
Anyway, the circuit is not very safe without emitter resistors, it could very easily go into thermal runaway.
  Reply With Quote
Old 15th March 2011, 01:07 PM   #3
diyAudio Member
 
Join Date: Nov 2010
Compare to the 10W amp on page 122 Fig.76, and you have the answers.
  Reply With Quote
Old 15th March 2011, 05:09 PM   #4
tca is offline tca  Portugal
diyAudio Member
 
tca's Avatar
 
Join Date: Jan 2011
Location: Lisboa
Actually on the first edition there is a 10W amp on page 39 (with AD162 ans AD162 also Germanium) and another 10W hi-fi amp on page 102 (fig. 71) with BD131 and BD132 which are Silicon.

The 1 Watt amp works in common-emitter configuration and the 10W that you refer is in common-collector configuration. Does the emitter resistors prevent the thermal runaway in both configurations?

I don't see how to adapt the circuit of the 1W amp, making it similar to the 10W, without changing all the circuit . This 1W amp has a relatively low part number, and that's the primary reason that led me into building it.

Cheers.
  Reply With Quote
Old 15th March 2011, 10:25 PM   #5
diyAudio Member
 
Join Date: Nov 2008
Why are you wasting your energy and money on a design that is 40+ years old. Better designs with similar or smaller parts count and superior performance are abound. E
  Reply With Quote
Old 15th March 2011, 10:34 PM   #6
tca is offline tca  Portugal
diyAudio Member
 
tca's Avatar
 
Join Date: Jan 2011
Location: Lisboa
I only have short answer to you question: for fun! My idea is to build a guitar amp from an old circuit, a transformer less amp, in the same spirit as the Deacy amp.

Could you point me some links to some "modern" 1watt amps with similar or smaller partsps? Thanks.
  Reply With Quote
Old 16th March 2011, 08:54 AM   #7
diyAudio Member
 
Join Date: Nov 2010
Hi TCA.
My Mullard book is the second edition so the page and fig numbers have shifted a bit, but the circuits discussed seem to be the same ones. The 1W amp using AC127/128 is clearly in common collector, the emitters are tied together and drive the speaker via capacitor C6.
The 'Deacy' amp you refer to is interesting. The name 'Deacy' is almost a certainly a simple corruption of D.C. as it's run off a battery, so as to distinguish it from the VOX AC30.
All I know 9of the circuit is what is implied from the text of the description.
It is a germanium design and uses one or two transformers.
There were a few similar circuits floating about in the early days of germanium which sort of mimiced valve designs. Some had a driver transformer and output transformer and some had just the driver with the output directly coupled usually via a capacitor.
The tonal (overdrive) characteristics derived from the use of the transformer(s) and germanuim transistors.
Replacing the germanium with silicon in a transformerless design is unlikely to give you the distortion characteristics you may be seeking, but thats no reasong to stop experimenting, keep going!
Regards
Henry
  Reply With Quote
Old 16th March 2011, 10:03 AM   #8
poynton is offline poynton  United Kingdom
diyAudio Member
 
poynton's Avatar
 
Join Date: Mar 2005
Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)
The crazy thing is that not many years ago, you could walk into any electronics shop and buy exactly what you want off the shelf.

I built several amps for schoolfriends with these ready-built modules.


Andy

.
__________________
If it ain't broke, break it !! Then fix it again. It's called DIY !
  Reply With Quote
Old 16th March 2011, 01:04 PM   #9
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
Quote:
Originally Posted by tca View Post
I only have short answer to you question: for fun! My idea is to build a guitar amp from an old circuit, a transformer less amp, in the same spirit as the Deacy amp.

Could you point me some links to some "modern" 1watt amps with similar or smaller partsps? Thanks.
Why not try something original for a change:

Here is an example based on a TL431 used as a supertransistor.
When built, it will look exactly like an ordinary discrete transistors amplifier, but with exceptional performances:
Attached Images
File Type: gif SmallAmp.GIF (50.6 KB, 400 views)
  Reply With Quote
Old 16th March 2011, 01:12 PM   #10
diyAudio Member
 
Join Date: Nov 2010
Ah, yes, the good old days.
They do say that nostalgia isn't what it used to be.......
  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 250 watt tube amp can be a 500 watt tube amp for less than 2 bucks plus tubes speakerfritz Tubes / Valves 17 24th October 2013 11:50 PM
180 watt Short Form MOSFET Amp Kit The Saint Aussie Amplifiers 5 26th October 2011 09:30 AM
chip amp as art form? JonGain Chip Amps 11 15th January 2011 05:06 PM
From Ger-many a few greetings awe-sum Introductions 0 30th June 2009 08:10 PM


New To Site? Need Help?

All times are GMT. The time now is 07:03 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