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rdf 14th December 2004 06:00 AM

Mullard 3-3 Question
2 Attachment(s)
My chassis is done but before soldering in the components, does anyone know the history of the two Mullard 3-3 schematics available online? Version A appears to be from the original article and B from some unspecified later date. I've prototyped both and A measured significantly less distortion, and I recall it sounding better too. Anyone know the origins of the B version?

Version A

rdf 14th December 2004 06:02 AM

2 Attachment(s)
And Version B.

ray_moth 14th December 2004 07:19 AM

2 Attachment(s)
I have yet another schema, which I believe to be the same as in Mullard's publication:

rdf 14th December 2004 07:22 PM


Originally posted by ray_moth
I have yet another schema, which I believe to be the same as in Mullard's publication:
Thanks Ray, that's version B with tone controls. Is that from the 1959 'Mullard Tube Circuits for Audio Amplifiers'? Version A is from a Radio Constructors article dated roughly the early fifties. I'm trying to determine which is the newer and, if B, figure out why I found its performance inferior to A.

ray_moth 20th December 2004 01:36 AM


Is that from the 1959 'Mullard Tube Circuits for Audio Amplifiers'?
Yes, I built this in 1963 as a record-player amplifier, using Mullard's book. It worked OK but it had only a small eliptical speaker and was driven from a crystal pickup (ugh!), so I wasn't able to evaluate it properly.

rdf 21st December 2004 03:49 AM

Thanks again. Maybe the redesign was due to changes in tube parameters, field failures, or something else unrelated to raw performance. I think Version A's the one then. Some LTSpice results suggest a simple front end change can yield a big payback on A as well. Experiment time!

M Gregg 14th July 2013 07:52 AM

Hello rdf,

What was the outcome of your experiments?

Which circuit did you think was the best A or B and why?

Any thoughts on the level of gain between the two?

Thank's for your thoughts:)


M. Gregg

M Gregg 14th July 2013 02:25 PM


I have no connection to the link in the previous post, Its just for interest.

M. Gregg

M Gregg 18th July 2013 06:39 PM


There are two different circuits of the Mullard 3-3 amplifier in this thread.
Has any one built the early version or the late version?

There only seem to be a few changes the anode resistor on the EF86 and the cathode connection on the EL84. (1M and 0.1uf)+ the 1k across the OP Tx.

Please does someone have any ideas why this circuit was modified?
If not does anyone have ideas about circuit operation A verses B?

There must be a reason for the changes:confused:.

If not please have a guess..LOL

M. Gregg

M Gregg 20th July 2013 08:07 AM

Some interesting information,

And PDF files. Sterns etc.

Mullard 3-3 information required - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

M. Gregg

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