Mesa/Boogie Quad Preamp

Mesa/Boogie Quad preamp

serial#: Q2243
year: aprox 1991


2 channels, 4 modes (2 rhythm and 2 lead)
8x E83CC NOS Tesla preamp tubes (Telefunken production!)
2 custom made Accutronics spring reverbs
Tube driven reverb and stereo fxloop
2x 5 band graphic EQ
5 EQ shift functions per channel to change the sound
Hand made in the USA
8 on/off jacks for each function

For audio samples click here or check out

page updated: January 12 2003


A great guitar will sound not too bad through a mediocre amplifier,
while a mediocre guitar will sound good on a great amplifier.

Mesa/Boogie designer and president Randall Smith: "The Quad (plus the Simul 395 Stereo power amp) is intended primarily for the concert-touring pro. And the idea is to offer a real alternative to the usual assemblage of two or three (or more) separate amps -usually modified- plus a custom switching system."Quad premap

I've been searching for the right (pre)amp for a long time. I need(ed) an amp that can produce several good tube sounds, and never found this in an amp head (although Diezel makes a nice one). After trying (almost) every possible preamp I found only 4 that were suitable: Mesa/Boogie Triaxis and the Quad, The Rover by Ernst Fliek (simply amazing) and the Egnater IE4. The Quad was the only one I could really effort, because all the other ones are at least three times as expensive.

But man...... it sounds. I get compliments all the time about the sounds coming from this amp. Due to the tubes (the signal always passes at least 5 tubes in this preamp) and all the EQ possibilities there is an endless scale of (quality) sounds. From the best Fender Black Face Twin imaginable to the most brutal and massive sounding scooped metal sounds without loosing tone, punch, clarity, character or definition. I don't know what they do at Mesa/Boogie, but I LOVE a strong and tight low end (which I can't get out of most amps, like a Marshall), and this machine, in combination with the Mesa/Boogie 395 power amp, can create such a BIG low end, it's beyond comprehension.

No matter what settings you create, it always delivers Tone, Power and Definition. It's amazing that it keeps so much tone and punch in it's sound even with scooped mids and no matter how brutal you set it, you can always hear every single note you play. Now THAT's quality. But it does take time to get to your ultimate setting, don't expect to have your sound immediately, but the tweaking and time is well worth it.

Because one's you're there.... you never want to leave it. I used to play in two bands, one "metal" orientated and one guitar rock a la Afghan Wigs (stopped with this band) and with each style this amp gives me a powerful sound. Especially with a Les Paul the clean channel breaks up so beautiful with a nice tube compression, there is really nothing like it. I've hooked up a bassguitar several times to my rig and it sounds amazing too, so big and powerful. I wonder how my rig would sound when I connect it to an Ampeg 8x10" speaker cabinet and play with a Music Man Stingray...... :-P

For sound samples click here or check out


Channel ControlsThis preamp has 2 channels, each with clean and  dist. They all sound really different and the possibilities are endless. No matter what sound you dial in, they all sound very direct, full & rich of harmonics and dynamics. There are endless possibilities to get your sound. That's also the hard part with a lot of Mesa/Boogie gear, it takes a lot of time to get your tone, but once you've got it.... man you don't wanna leave.

The preamp is divided over two channels, the above one is modelled after a Mesa/Boogie Mark IIC and the lower channel is based on a Mark III. Each channel has a clean and high gain sound. Both clean and lead mode of each channel share the EQ section and the 5-band graphic EQ, which can be used for either or both clean and lead. Each channel features volume (pull bright), treble (pull shift), bass (pull shift), middle (pull deep), master, lead drive and lead master (pull bright). All the pull functions shift the tone spectrum of the control, giving you the ability to really find your tone. The tone pots control the sound prior to the distortion path, the 5 band graphics EQ is situated after the distortion path, enabling you to both change the character and the tone of the distortion. The preamp also has for each channel a tube driven Accutronic spring reverb. Each reverb is modelled especially for it's channel: one is shorter than the other.

Backside The backside the Quad has a lot of features too: Instrument input (all pro rack gear have it on the backside, there is no need for a front input), fx loop (mono send, stereo return + switch for low or line level), stereo recorded out (with speaker simulation), stereo output, 8 on/off jack outputs for all functions (a midi function switcher can be connected to control everything with midi), footcontroller input and of course the ground lift switch.

For each function (channel switching, eq, reverb) the Quad has there is a on/off jack output (8 in total). I've connected them with the Nobels MS-8 which is connected to the DigiTech GSP2101. That way I can control the Quad preamp with MIDI which prevents me from tap-dancing. No I press just one button to go from one sound to the other, without audio drops. So I can go from "a beautiful rich clean sound with the Accutronics reverb + chorus/detune/delay of the GSP2101" to "a screaming lead sound with complex EQ, detune and noise gate" in less then a 10th of second.


The preamp uses 8 NOS Tesla E83CC tubes. These were made in the 70's by Telefunken and are as good as it gets. The whole signalpath of the Quad uses tubes and no opamps like many other preamps such as the Triaxis and the JMP-1. So tubes have a huge influence on the tone of the preamp.

Before I switched to all Tesla E83CC tubes I used a variaty of tubes. This gave me great sounds, but the preamp has never sounded as good as it does now. The bass is stronger and deeper, dynamics are better and the overall tone is just really good.

The Rhythm 1's clean sound is really deep and warm, yet with bite in highs. Rhythm 2 has a great crunch sound, something which can be hard to find with the Quad. But the crunch is now deep and warm with lots of push. Lead 1, which is my medium gain sound, has an attack which is new to me with this channel. Although it can sound really brutal it still remains clear and crisp. It has a warm mid range which really makes you cut through the mix. Lead 2 is my high gain sound. Great sustain and clarity. It's in your face, big and bold. But without sounding harsh or noisy.

I found that taking your time in selecting each tube for each stage can greatly enhance the sound. It takes some time, several different tubes and good attention for what you notice and what you are looking for. But a lot things that you might dislike about an amp can be solved by changing the preamp tubes. I've noticed great improvements in many amps when changing the stock Chinese or Sovtek (EH) tubes with JJ's for example. In my opinion Chinese and Sovtek tubes have a harsh top end that can make a amp sound buzzy. JJ's are an easy solution to remove this, they are currently produced, widely available, not expensive and quite reliable. But it may sound too dark for some people. Still it amazes me that designers of nice amps like Bogner and Mesa/Boogie design their amps around Chinese tubes. But maybe they think if it sounds ok with this tube, it will sound great with any other tube. Check the Tubes section in the index to find more info on tubes.

The sound
How does it sound? Well... huge!. It really has a tone to die for. Very dynamic clean and great responsive leads, with clear projection and articulation. No matter how complex the notes you play, they cut through easily and clearly. It has so much tone that I need to play on a lower volume with the band, because it cuts through everything (even with all the mids scooped). No wonder, because it uses eight ECC83/12AX7 tubes and the signal passes a minimum of 5 tubes in the Quad preamp. My high gain sounds are very responsive and there is no need for a noise gate, cause it's just extremely quiet.

Besides the amazing quality of the preamp and the tubes used, lowering the gain to the minimum I need gives me more clarity, punch, less noise, etc. I just don't understand my people turn the gain all the way up, listen to the pro's and you'll notice that less is more. If I lower the volume on a high gain sound I get a beautiful clean sound without any hiss or trouble, just pure beauty. Now that's what I call quality.

What also makes a lot of difference with other amps is that the distortion is created by the tubes and not by op-amps (=transistor). This makes a lot of difference; for instance the Marshall JCM900, JMP-1 and the Valvestate series, use the tubes only to COLOR the distortion, NOT to create it, this is done by op-amps!. The Quad is not your ordinary (pre)amp, this is something different. It is the highest quality preamp Mesa/Boogie has ever built (together with their Triaxis). Randall Smith (the president of Mesa/Boogie) used to work as a mechanic on Mercedes' and English sports cars. He intended to put the quality of those cars in his amps. I don't know if you've ever driven a Mercedes, but then you would be able to understand how fine this preamp is. For the new price of the Quad preamp  you could easily buy a complete Marshall stack. But the tone..... simply amazing. :-D

For sound samples click here or check out

In action
I have made up a few basic sounds with which I can play anything I want. The great thing with the Quad is that you can combinate channels with each other. I use the Digitech GSP2101 to fine tune the sound if needed, and to add some fx. My main sounds are:
1. Clean - very fenderly, deep and rich (ch1 rhythm, Mark IIC)
2. Clean/Crunch - crunchy yet cleaner (ch1 rhythm + ch2 rhythm)
3. Crunch 1 - from clean to dirty depending on the picking (ch2 rhythm, Mark III)
4. Crunch 2 - brutal, big, raw, dynamic, pushing with attack and definition (ch1 lead, Mark IIC)
5. Crunch 3 - think Crunch 2 but even bigger (rhythm 2 + lead 1)
6. Lead 1 - tight high gain sound, tone, rich harmonics, dynamic, noiseless (ch2 lead, Mark III)
7. Lead 2 - combination of lead 1 plus crunch 2, you do the math.

With these 4 channels I can play anything I want. A good clean sound is very important and I'm glad the Quad delivers what one might expect from a good Fender. I set it up to be clean, but for a nice rock rhythm sound it can break up beautifully with a nice compression to it. The 2 crunches are totally different from each other, the first one (ch2 rhythm) is less pushing and goes fluidly into a distortion, the 2nd crunch (lead 1) is just amazing, it's maybe my favorite sound and by far my favorite channel - it can do anything. It's so direct, raw and pushing, I set it up in such a way that you need to do your best to get it really distorted, that way it sounds very powerful and dynamic. And when needed you just play softer and it you'll get a very thick clean/crunch sound with endless sustain. This sound in combination with my Ibanez Universe 7 and a set of very heavy strings (012-058) gets so big and brutal... I just can't stop playing.

Mesa/Boogie Quad - Graphic EQ By far the lead 1 is this the best channel of the Quad. I used it for a long time as my main lead sound, but found out that the lead sound of the 2nd channel could come close when it comes to high gain sounds. Although I scoop a lot of mids, it has still more mids then a JCM900 could ever produce. The lows are very tight and deep and the highs are clear and complex, without hurting your ears. I use as less gain as possible to preserve the attack, tone, clarity and subtle playing. And safe myself the use of a noise gate cause it keeps so quiet.

Thanx to it's open and clear sound the Quad is veyr unforgiven. Every little detail comes through, so you really have to be careful. But it really invites you to play as good as you can, because every little nuance comes through clearly. It's a joy to play through it.The way I've set the Quad preamp in combination with the heavy strings on my guitar, playing is hard working and every mistake comes through clearly. It always makes me laugh when people think that (with my) rack setup you're able to mask your mistakes, etc. I think they'll shiver as soon as they have to play on my heavy strung guitars and notice that every little details comes through clearly..... ;o)

Inside Quad Many people think that 19" rack gear is to covers up the lack of good guitarskills. Well in this setup it's the other way around. The preamp is really direct and honest. So everything you put into it is coming out twice as clear, so there is no way you can cover up your lack of playing. But it really invites you to play better, because everything you put into it cuts through clearly and with a lot of depth and definition. It is tone glory.

Before I had this one I used the DigiTech GSP2101 as my main preamp which sounded a little weak. The difference between the two is so huge. With the GSP2101 I had several EQ's running to get a great deep low end, but I was never able to get a tight low end with a good projection. Well, this preamp gives me so much tight and powerful low end with a clear projection that my system could easily pass as a bass amplifier.

I run my guitar through an Reactive Cable & Briljant Box, with next only the Teese RMC3 wah pedal, and then straight to the rack where the signal is split between the two preamps. The fx send of the Quad preamp goes to the DigiTech GSP2101, from which I use the preamp section (EQ and volume) for extra control over my sounds. The Climax S3 is connected to the fxreturn of the DigiTech, which takes care of the mixing of the two signals and fx. The output of the DigiTech is connected to the poweramp.

For sound samples of the Quad click here or check out

Internal signal flow
On the schematics page you can find the all the layouts of the Quad preamp and it's original control pedal.

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

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

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


Related subjects

Audio samples
Mesa/Boogie 395 Poweramp
DigiTech GSP2101
Nobels MS-8
19" Rack
Signal line

Mesa/Boogie Homepage


2003, Tubefreak