This page is a general description and help to identify the different Dual Rectifier 2 channels.

This article deals with : Rev-* which meens the Revision of the motherboard.

Also, about S/N, Schumacher transformers and « Pre500 ».

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We find the Dual Rectifier since 1992. Different Revision of the motherboard has been released between 1992 and 93.

From 1993/1994 to 2000 nothing changed.

The First revisions A and B seems to be only protypes.

The first Dual Rectifier S/N: R0001 is now in Germany and it's a Rev-C.

The First 220/240 Dual Rectifier released are Rev-C.

Then Rev-D until S/N : 506* which is Rev-E and after 602* until 2500 is Rev-F.

After S/N : 2500 became all Rev-G until 2000 wich is the year of the 3 channel Dual Rectifier.

Note : the Trem-O-Verb Is Based upon the Rev-G

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What is Pre500 ?

Pre500 is the common name to include Rev-C and D which are the 506 first Dual Rectifier ever made.

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How to recognise these amps ?

The better way is to open the chassis and the revision is marked on the motherboard.

Another way is to recognize the physicals differences :

On the Front there is a small Mesa logo on Rev-C; D; E and F

Big logo is for Rev-G

On the rear :

From left to right :

Speakers Jacks are 8-16 / 8-16 / 4 / 4 for Rev-C; D; E and F.

Speakers Jacks are 16 / 8 / 4 / for Rev-G.

Serial Loop for Rev-C ; D ; E and F.

Parallel Loop for Rev-G.

Export items don’t have A-B ground switch.

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And what about the Schumacher transformers ?

The Rev-C ; D ; E and F have Schumacher transformers.

Some of the Rev-G have Shumacher too, but there is no rules about it. The Trem-O-Verb follow the same rules than Rev-G.

Schumacher Transformers can be recognized by the 3 numbers after EIA - * engraved on the transformers.

EIA-606* are Schumacher.

The Schumacher transformers were used on mesa MKIII 100W amps. For some people this is the reason why Pre500 sounds better than other 2 Channel Dual Rectifier.

In fact there is much more than the Pre500 who has Schumacher Tansformers, so this is not a reason.

Rev-C ; D ; E ; F and G have different voicing.

Rev-G is the darkest one and the less raw.

As C ;D ; E and F have a different voicing and it’s definitely tighter than Rev-G. Rev-G have more gain too.

* All S/N are subject to change because they are axpproximates

Thanks to Elpelotero from BBoard forum and David.

Anyone who have better infos please mail me at

the souls remain at wanadoo dot fr. (all attached)