Schematics

* Custom A/B Signal Relay Switcher
*
Cable buffer
*
Thordendals (Meshuggah) Stereo Breathcontroller
* Mesa/Boogie Quad Preamp
* Mesa/Boogie Triaxis Preamp
* Mesa/Boogie Studio Preamp
*
Mesa/Boogie V-Twin pedal
* Mesa/Boogie 2:90 Poweramp
*
Mesa/Boogie 50/50 poweramp
*
Mesa/Boogie Strategy 400 poweramp NEW
*
Mesa/Boogie Mark I
*
Mesa/Boogie Mark II
*
Mesa/Boogie Mark III
*
Mesa/Boogie Mark IV
*
Mesa/Boogie Dual Rectifier Solo Head
*
Mesa/Boogie Tremoverb
*
Mesa/Boogie Heartbreaker
* Mesa/Boogie Maverick
* Mesa/Boogie Blue Angel
* Mesa/Boogie Subway Blues
*
Mesa/Boogie Subway Rocket
* Mesa/Boogie Caliber 50
*
Mesa/Boogie Son Of Boogie
*
Mesa/Boogie Bass 400
* Mesa/Boogie Speaker Simulations
* Watkins Copy Cat
* Pickup and cable wiring info
* BPM / Delay time conversion matrix

updatedOctober 31st 2002

 

 

Here are some schematics that are hard to find on the web, plus a nice self-designed a/b signal switcher. The quality is in most cases as good as the originals that I have. I've gathered these schematics over the years. As far as I know, all the Mesa/Boogie schematics came from people who got the originals from Mesa/Boogie themselves.

With the following schematics you should be able to understand the equipment a lot better, can work out how the signal flow goes, which tube does exactly what/where and it's easier to do some mods. Keep in mind that changes may have occured, these schematics may not give an accurate view of the amp.

All files are either .JPG or .GIF unless stated otherwise. I've done my best to keep their size as low as possible, yet retain detail. I don't post schematics of Marshall, Fender, Bogner, Matchless, 5150, etc. These can "easily" be found at www.schematicheaven.com, http://www.mif.pg.gda.pl/homepages/tom/schematics.htm and many other webpages. I've tried to collect as many Mesa/Boogie schematics as I could and posted all of them. Some can be found at the previous mentioned pages as well.

The designers of these amps have worked years and years to fine-tune it.
By no means use it to try to built a replica, it won't work.
These schematics are only here for information & repair.
Trying to replicate it is useless.

ps I'm still looking for schematics of the Strategy 500 or the Simul 395 Stereo poweramps, please let me know if you have them. Other Mesa/Boogie schematics are welcome as well!

 

recent updates: Thortendals Breathcontroller,Triaxis mods, new Mark I's, new Mark II's and lower kb files of the Quad preamp.


Custom A/B Signal Relay Switcher
Sometimes you need an a/b switch that can be activated with a footswitch, so you don't have to run those miles of cable. This is a design to built your own a/b switch with one input and two outputs (or the other way around), but needs a latching footswitch to change the signal routing and some DC to activate the relay. This is a quality design that should give you noiseless switching. It's being used by me as a mute switch for my preamp and the latching footswitch connection allows me to control it with a
Midi Controller. So this is real handy for all you 19" rack freaks. If you use some quality components and good cable then this a/b box shouldn't alter your sound. There is even a mod that prevents groundloophum!.
Schematic and explanation (30k)

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Cable Buffer
I run 12 metres (aprox 36 feet) of cable between my guitar and rack with only a true bypass wah connected. For a long time I noticed signal degration (loss of highs) even with low capacitance cables. This is the easiest and most cost affective solution. It's a simple FET desgined buffer that converts the guitar signal from high impedance to low impedance and runs on 9 Volts. It only requires juice, one fet, one capacitor and one resistor. No dificult schematics, no gadgets, just pure (restored) tone. It works flawless and brings the brilliance back to your signal. More info on this can be found at the
Reactive Cable page and the Briljant Box page.

The BF245 fet's pin layout is as follow:
pin1: drain, pin2: source, pin3: gate. With the flat side of the fet on the table and the pins towards you: the left pin is the voltage, in the middle the output and on the right the input. Changing the value of the cap will increase or decrease the low end in the sound. 10 uF is nice, 47 uF is great for bass and thin sounding guitars.
Schematic (3k)
Schematic (3k) with pinlayout as you will see them

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Fredrik Thordendals Stereo Breathcontroller
This is the famous stereo breathcontroller that Johan Haake designed for the guitar player of Meshuggah. Fredrik Thordendal uses it to get those weird solo sounds.
Layout (19kb)
Powersupply (15kb)
Simple version (32kb)

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Mesa/Boogie Quad preamp and FU-2 footswitch
Quad main layout #1 (30kb)
Quad main layout #2 (36kb)
Quad layout - additional text (24kb)
Quad lead and graphic EQ circuit (36kb)
Switching system of the Quad (22kb)
Tube layout and functions of the Quad (17kb)
FU-2 footswitch for Quad preamp (40kb)

The tube/signal flow is as follow:  
            CH1------V21-----V23-----V12b-----
input---[                                                  ]-----V24-----V14-----fx loop-----V22
            CH2 ------V11-----V13-----V12a-----

V11=input CH2
V12=CH1 + CH2
V13=lead CH2
V14=Graphic EQ + Reverb mixer

V21=input CH1
V22=FX return + output
V23=lead CH1
V24=reverb

For additional info check the Quad Preamp page.

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Mesa/Boogie Triaxis preamp
First stages with additional info (89kb)
First stages (66kb)
Dynamic Voice + loop (33kb)
Outputs (33kb)
Mode switching (86kb)
CPU/Memory (42kb)
Port decoder (25kb)
System clock/reset/display/midi (40kb)
Mod notes1 (21kb)
Mod notes2 (32kb)
Presence mod notes (28kb)
Regulator mod notes (18kb)


For additional info on which tube does what and to prevent internal overload,
please take a look at the
Triaxis Information page.

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Mesa/Boogie Studio preamp
This schematic is really large. That's why I've cut the schematic up in 6 pieces as well.
Studio (full version) (125kb)
Studio cut 1 (29kb)
Studio cut 2 (20kb)
Studio cut 3 (28kb)
Studio cut 4 (35kb)
Studio cut 5 (21kb)
Studio cut 6 (34kb)

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Mesa/Boogie V-Twin pedal
Complete - large! (132kb)

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Mesa/Boogie 2:90 poweramp
Version 1(43kb)
Version 2 (31kb)
Powersupply(43kb)

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Mesa/Boogie 50/50 poweramp
50/50 1 (13kb)
50/50 2 (12kb)

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Mesa/Boogie Strategy 400 poweramp
str400 (30kb)

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Mesa/Boogie Mark I
Preamp (11kb)
Poweramp (16kb)
Mark IA (90kb)
Mark IB (52kb)
Mark I Reissue preamp (40kb)
Mark I Reissue poweramp (43kb)

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Mesa/Boogie Mark II
MKII Complete (55kb)
Preamp stage MkIIC+ (23kb)
Preamp stage MkIIC+ original (84kb)
Poweramp MkII (19kb)
Poweramp MkIIB (19kb)
Poweramp MkIIC+ (79kb)

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Mesa/Boogie Mark III
Preamp (38kb)
Poweramp (43kb)

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Mesa/Boogie Mark IV
Preamp section 1 (39kb)
Preamp lead + reverb (31kb)
Poweramp (22kb)
Graphic EQ (41kb)
FX loop (26kb)

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Mesa/Boogie Dual Recto Solo Head
Preamp version 1(21kb)
Preamp version 2 (21kb)
Preamp original drawing (30kb)
Poweramp original drawing (24kb)
Poweramp (14kb)
complete (172kb) ZIP-file, contains everything incl fx loop and switching matrix

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Mesa/Boogie Tremoverb
Powersupply (37kb)
Preampstage (43kb)
FX loop + reverb (28kb)
Poweramp (28kb)
Switching matrix (32kb)
Tech bullitin (7kb)

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Mesa/Boogie Heartbreaker
Block diagram (11kb)
Channel 1 (18kb)
Channel 2 (14kb)
Powersupply (19kb)
Poweramp (15kb)
Reverb + FX loop (13kb)
Switching Matrix (14kb)

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Mesa/Boogie Maverick
Preamp part 1 (40kb)
Poweramp (30kb)
Preamp part 2 (27kb)
Power supplies (26kb)

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Mesa/Boogie Blue Angel
Preamp (17kb)
Powersupply (15kb)
Poweramp (18kb)

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Mesa/Boogie Subway Blues
Block diagram (9kb)
Preamp (16kb)
Powersupply (10kb)
Poweramp + rec out + reverb (16kb)

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Mesa/Boogie Subway Rocket
Switching matrix (11kb)
Preamp (13kb)
EQ + FX loop (12kb)
Powersupply (16kb)
Poweramp + rec out (16kb)
Block diagram (12kb)

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Mesa/Boogie Caliber 50
Preamp (49kb)
Poweramp (49kb)

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Mesa/Boogie Son Of Boogie
Layout (47kb)

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Mesa/Boogie Bass 400
Main stages (61kb)
Power + graphic EQ (59kb)

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Mesa/Boogie Speaker Simulations
Triaxis (10kb)
V-Twin pedal (13kb)
Check the other schematics for more speaker sims

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WEM - Watkins- Copycat Echo Unit
Original schematic (28kb)

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PICKUP AND CABLE WIRING INFO
Check the dedicated page.

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BPM / DELAY TIME CONVERSION MATRIX
Overview of usefull delay times between 85 and 150 BPM including triplets and 5over4 counts!

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Related subjects

Quad preamp
Triaxis information page
links

INDEX

 

2002, MvH