Hammond XB-2 - Tech Tips


How to fix loose keys on the XB-2's manual?
How to adjust the internal pots on the XB-2?
How to EQ the XB-2.
Hammond-Suzuki XB2 ROM Upgrade.

Mark Longo has submitted a few postings on modifications and adjustments for the Hammond-Suzuki XB-2. Those commonly asked for are included here.

How to fix loose keys on the XB-2 manual.

This is a very typical problem, and fortunately, it's very easy to fix if you're even a little mechanically inclined. Each key in the XB-2 has a small guide under the part of the key that is closest to you. That guide has a little rubber-like 1/4' long tube (jacket) that slips over it. When that little jacket wears out (which it eventually will) the key's lateral positioning gets sloppy. When you grip the front of the key between your thumb and forefinger and wiggle it very gently from side-to-side if the key easily slides up against the adjacent keys, the little rubber tube has either worn thin or has completely worn out and fallen off. You'll need to replace the tube. You can get the replacement jackets from Hammond and do it yourself, or pay your dealer/shop to do it. It's better if you can do it yourself as this will keep happening periodically. Replacement jackets can been obtained direct from Hammond Suzuki USA via mail.

Here's how to replace the jackets:

  1. Take the top off your XB2 by loosening the 5 phillips head screws underneath the organ (be sure to unplug the AC power first!).
  2. Remove the loose key (be careful you don't break it, it's only plastic!). Each key attaches to the organ at the end farthest from you as you face the keyboard. This end of the key latches through a little metal housing. Gently press the tip of the key that goes through the metal housing downward and slightly forward and the key will pop out. It may take a bit of force to do this but be careful you don't break the key. Use your fingers or a piece of hard rubber or something else that's firm but not rigid.
  3. Replace the little jacket. In the space underneath the front of the key you just took out, there is a little metal tongue about 1/4" wide that's pointing toward the ceiling. Remove the old jacket (if it's still in place at all) from the tongue. Each jacket has a little ridge on each side. When you slide the new jacket on, the ridges should point toward the front and rear of the organ. If in doubt, take off another key to see what a properly installed jacket looks like. Slide the new jacket on. The jacket will stretch a bit going on as it's a tight fit, but it will go on.
  4. Replace the key. You do this by carefully fitting the far end of the key back into the metal housing. The underside of the key has some plastic nubs and such that must fit into the keyguide just in front of the metal housing. Watch out that you don't break the key by just jamming it into the housing. This is actually pretty simple, just be careful.
  5. Repeat for each loose key, then replace the top.

How to adjust the internal pots on the XB-2

Mark Longo (longo@swanky.zk3.dec.com)

Posted to the Hammond Mailing List on 22 March 95

Things have been quiet on the list, so here's something for the XB2 owners among us to chew on.

I finally got around to experimenting with the XB2's internal trim pots. You can use these pots to adjust the XB2's overall output level, overdrive level and extent, and to modify the vibrato/chorus depth slightly. There aren't any internal adjustments that let you alter the XB2's basic tone, though boosting the XB2's output signal to your amplifier may yield a somewhat fatter tone due to natural harmonic distortion realized in the amplifier's pre-amp section.

Below I describe what I discovered by experimenting with different pot settings on my XB2. I should mention that my XB2 was made in the first year of manufacture. It's possible that if you look inside your XB2 you'll see something different than what I describe below, or that adjustments to your own XB2 pots will have slightly different results. Obviously I accept no responsibility for the accuracy of my below comments as applied to an XB2 other than my own. Please use caution and common sense.

If you're the sort of person who likes to tinker with electronics and you're not afraid of tweaking with your XB2 a bit, you'll probably find that these adjustments allow you to tailor the performance of your XB2 a little and you'll have fun monkeying with it in the bargain. On the other hand, if you're the sort of person that heeds warnings like:

Refer repair work to qualified personel.

...then you may be better off leaving your XB2 alone. After all, they sound pretty cool as they come from the factory and since you have to make the below adjustments while the XB2's power is turned on, there IS some danger of electric shock. Also, if you drop something on the circuit board(s) that conducts electricity (like, say, a screw driver), you might short something out resulting in a costly repair bill and your doing without your XB2 for a while.


BEFORE ADJUSTING ANYTHING: Write down the factory-set position of ALL the trim pots! Be forwarned, Hammond-Suzuki will not take kindly to your call asking what the factory settings are since you forgot how yours were originally set yours and screwed them all up. If you get lost, send me e-mail and I'll send you my default settings, but they may be different for you if your circuit board is of a different revision than mine. Therefore, take a few seconds to write your settings down and avoid feeling stupid later.

Making Adjustments:

The XB2 has several small potentiometers (pots) on the upper circuit board on the right side of the organ, visible when you remove the cover. My XB2 pots have a white plastic phillips type adjustment screw head about 1/4 inch in diameter. The name of each pot adjustment is screened onto the circuit board in English somwhere near its mounting point. I noticed an unlabeled pot on the lower circuit board near the AC power recepatacle on the left side of the organ. This may be an AC line level adjustment (high voltage) SO DON'T MESS WITH IT.

Some of the pots increase their assigned effect when turned clockwise, others counter-clockwise. One presumes this is because some effects increase with impedance while others decrease. Just monkey around with the pots and you'll see which way to turn them. I tried turning each pot to its full deflection in both the clockwise and counter-clockwise directions and nothing terrible happenned (my XB-2 didn't blow up!). I did adjust the pots one at a time so at no time were they all max'd at once, though I personally doubt that max'ing everything would harm the electronics.

You use the XB2's left output jack only when plugging into a mono amplifier or mixer. This means that when nothing is plugged into the right output, a summation of the right and left channels goes to the left output. Many of the pots in the XB2 control left and right channels separately. When listening to mono output (left output only), tweaking a RIGHT channel adjustment affects the summed output as much as tweaking a LEFT channel adjustment.

These pots control the "clean" output of the organ, that is, the output of tone generation exclusive of the overdrive circuit. You can boost the output to the point that you can badly overdrive a mixer's line input resulting in some very ugly distortion. At first I thought this was distortion in the output section of the XB2, but I max'd these pots and fed the signal to my Leslie and heard far less distortion than with a line mixer, though some distortion is still present.
Note that it may be possisble to dramatically increase the amplified volume of your XB2 by adjusting these pots and thereby feeding your amplifier a MUCH hotter signal. I have found this to be very useful since my Leslie needs a little help to output enough volume in some live settings. Be careful though, excessive output may cause your amplifier to distort in ways that neither you nor your amplifier like. I believe that the XB2's come from the factory with the gain pots set to a fairly low output value.
These pots determine the amount of distortion added to the output signal by the overdrive unit. OD MIN sets the amount of distortion applied to the output signal when the distortion wheel (modulation wheel on the organ control panel) is at its full backward deflection. OD MAX sets the amount distortion applied when the wheel is at its full forward deflection. In theory, setting OD MIN to its lowest value and OD MAX to its highest would supply the widest range of distortion available.
These pots appear to control the overall boost that can be applied to the output signal by the overdrive circuit. These pots can be used to boost the level of the overdrive circuit's output, making the organ's output signal hotter (and possibly overdriving the amp/mixer/tape you're connected to). Acting in concert with the OD MIN / OD MAX adjustments, these pots can be used to tailor the effects of the overdrive circuit.
Use caution and judgement, it's theoretically possible to damage the input circuit of some types of gear by feeding it too hot a signal from your organ. If you hear lots of distortion with the OD wheel at the minimum position, you've probably overdone it.

NOTE: I haven't messed much with the OD pots. It would seem possible that by setting a modest value on the OD GAIN pots you'd be able to add distortion with the mod wheel but NOT volume. Many people have complained that increasing the XB2 overdrive level using the mod wheel adds way too much volume to the output signal.

If anyone tries this, please let us know what you find.

The settings of these pots control the effect of the full backward and forward deflections of the Hammond expression pedal. The EXP MIN pot can be set so that full backward pedal deflection still allows a healthy output level. Conversely, the EXP MAX pot can be used to limit organ output when the pedal is at it's full forward deflection. Note that the EXP MIN pot can NOT be set to silence the organ at full backward pedal deflection.
Apparently the expression pedal is a simple voltage regulator. A control voltage is sent to the pedal, the pedal returns a voltage level that is the same or lower depending on whether the pedal is deflected forward or backward. This is distinct from guitar-type volume pedals which modulate the amplitude of an audio signal. The EXP MIN and EXP MAX pots appear to set the lower and upper limits on the voltage returned from the expression pedal.
There have been many complaints voiced on the Hammond mailing list that the vibrato and chorus on the XB2 are weak when compared against the same effects on a B3. The VIB2 and VIB3 pots can be used improve this slightly, but basically, you just have to live with the XB2 vibrato sound.
These two pots adjust the depth of V2 and V3 and C1 and C2 respectively. Apparently there is no way to adjust the depth of V1 or C3. Max'ing the VIB3 pot will cause C2 to have the same depth as C3, but with a very tiny bit more low frequency content. You have to listen hard in a quiet setting to hear the difference.
This adjustment supposedly effects the sound of the XB2's built in Leslie simulation, though personally I can't hear that it does much of anything. It seems to change the "beating" in the highs coming through the Leslie effect a little, but the change is VERY subtle and you have to listen carefully in a quiet setting to hear any difference. In any case, I don't find it useful for audible adjustment.

  Mark Longo 					Digital Equipment Corp.	
  longo@zk3.dec.com				Nashua, NH
  87 8300 020

How to EQ the XB-2.

Mark Longo (longo@swanky.zk3.dec.com)

Posted to the Hammond Mailing List on 05/30/95

Hi folks,

Having just finished three gigs this weekend using my XB-2 through an equalizer and into my Leslie 302, I can tell you that for me, EQ'ing the XB-2 is a BIG plus. Using the EQ I'm able to remove most all of the XB-2's shrillness and substantially fatten up the low end and low mids, which gets me much closer to my favorite B3 tone. The details follow.


If you have a few bucks to spend on a decent graphic EQ, do it. You'll be surprised at how much you can change the sound of your XB-2. If you're one of us folks who thinks the XB-2 tone could be improved, you'll be surprised at just how good you can make it sound and you'll have lots of fun doing it.

A 15-band unit is sufficient, though a 31-band unit is a little more fun and has advantages for the very finicky ear. A constant-Q unit is highly recommended, and a 120Hz filter is a big plus. Also, 15db boost/cut unit is more versatile than a 12db unit, but isn't necessarily needed.

The Equalizer

I bought a high quality pre-owned EQ through the Internet ($200 US). It is a dbx 1531X, which is switchable for 31 bands mono (1/3 octave/band), or two 15-band ranges (2/3 octave/band) for stereo. This EQ has constant-Q circuitry, which means that the band width effected by each slider is constant whether the slider is at full boost, full cut, or anywhere in between. Some cheaper EQ's don't have constant-Q, so when you move a slider the effected band width becomes greater as the slider moves closer to extremes, thereby effecting neighboring frequencies more and more as the slider approaches full boost/cut. This makes it difficult or impossible to boost/cut a narrow frequency range (such as the top part of the last octave on the keyboard, for example) without effecting many neighboring frequencies. I strongly recommend getting a constant-Q EQ. Constant-Q is not always mentioned in advertisements so when considering an EQ, call the manufacturer or look at the manual to be sure it has constant-Q circuitry. I believe all the Rane EQs are constant-Q, as are most good grade units.

I wanted to get a 1/3 octave unit (31 bands) so I could cut most highs without cutting the key click and to do that I needed a slider somewhere near 7KHz. The 2/3 octave units (15 bands) don't have a slider near 7Khz as each slider on those units covers a wider frequency range. BUT, it turns out that the XB-2 is capable of delivering a loud enough click (especially with V2.0 OS) that I found I could deeply cut the high frequency overtones and still have plenty of click coming through. With this in mind it would should be sufficient to use a good 15 band unit, which is a somewhat cheaper than the 31-band units, though nearly not by half.

The dbx 1531X has boost or cut maximums switchable between 7.5db and 15db. The 7.5db range could be useful when making subtle changes to a mix or vocal tones, but for the XB-2 the 7.5db wasn't enough, so I use only 15db. A side note, many EQs offer 12db cut/boost, but I suggest trying to find one with 15db. I found that 15db of boost causes a bit of audible distortion with my performance rig. I like this because it lets me control which frequencies growl and which ones are clean. On my rig I set the EQ sliders so that the lows in the 500Hz region have a little more growl than the high, which I like clean. Your mileage may vary since you likely have different equipment, but in MY case, I don't get distortion till I move the sliders PAST the +12db point, so I'm glad to have the versatility of 15db.

Signal Path

I positioned the EQ after the XB-2 in the signal path, using the 1/4" line out jack from the XB-2 (left output for mono) and then into the EQ, then out from the EQ into my Leslie 302's 1/4" input. I could not use the 11-pin Leslie cable from my XB-2 because that cable won't plug into the EQ (obviously) and my Leslie 302 has no effects loop. Al Goff does not recommend using the XB-2 effects loop for EQ because more tone shaping takes place in the XB-2 internal signal path downstream from the effects loop.

Because I'm forced to use the 1/4" XB-2 output, I can not control Leslie speed using the XB-2 Leslie tab switch or a foot switch plugged into the XB-2, as is possible when using the 11-pin cable with my Leslie 302. Also, since devices in the XB-2 effects loop DO NOT EFFECT the XB-2's 1/4" outputs, I can't use the XB-2 effects loop when using the 1/4" output to the EQ. You could place an external device such as a chorus stomp box downstream from the XB-2, but these devices are designed to accept the low voltage levels generated by guitar pickups and will likely be badly overdriven by the XB-2's hotter output levels.

120 Hz Filtering

My EQ has a 120hz filter which for me is a BIG help. The XB-2 has a 120Hz buzz (at least mine does) which you only hear when you depress a key. It's not normally very noticable (unless you use headphones) but my EQ boost of the lows made it jump out. But the dbx 1531X has a button to take out the 120Hz frequency only, which removes the buzz almost completely (mmm-mmm good). There is also a slider at 120Hz, and I found that cutting the 120Hz range with the slider removes the buzz, but it also reduces the bass response of the organ noticably. Using the 120Hz cut button removes the buzz but doesn't effect the organ's tone.


Many of us have complained lots about the XB-2 chorus sounding whimpy. Using the EQ can improve the chorus sound surprisingly. Don't get me wrong, it still doesn't sound like that crunchy B-3 chorus so many of us like, but it is definitely improved. I'm not sure, but I suspect that cutting highs (ie: above 6Khz) is responsible for the improvement.

Tone Settings

I find that the EQ is effective in dramatically altering the XB-2 tone in a very wide variety of ways. The tonal changes you make are obviously a matter of your own taste. I use the EQ to try to more closely emulate a real B-3.

The EQ settings I use to do this are specific to my own perfomance rig, the room I'm playing in, my own personal taste, how many drinks I've had, etc., etc., etc. Your settings would (and probably should!) vary, maybe a lot. That said, it's a little silly to mention specific settings, but I'll tell ya how I set my EQ up this past weekend anyway. I like Jimmy Smith's tone on his recent albums, which I'd describe as sweet and a bit churchy, yet beefy in the lows and especially in the lower mid-range. The EQ lets me get this tone surprisingly easily. I use full cut (-15db) in all frequencies above 6KHz, with about half cut between 4KHz and 6KHz. I set 1KHz to 4Khz somewhere near flat, with gradually increasing boost from 1KHz down through the bass/treble rotor cut off point (800Hz). As I get into the bass rotor range I increase the boost even more. And I've been adding a little growl by boosting to nearly full throw (+15db) in the 400-600Hz neighborhood.

If you try this, let me know what you find.

Have fun, Mark

  Mark Longo                                    Digital Equipment Corp. 
  longo@zk3.dec.com                             Nashua, NH
  87 8300 020

Hammond-Suzuki XB2 ROM Upgrade.

Hammond-Suzuki has released an ROM for the XB-2 which upgrades the old OS from version 1.x to version 2. Following is a review of the upgrade with before/after type comparisons describing the changes the new ROM brings to the XB-2. After the Review is a list of features found in the version 2 ROM.


I installed the ROM upgrade 2 and was pleasantly surprised to find some unexpected benefits. It turns out that in addition to significantly extending the XB-2's functionality (ex: extended MIDI, better split options, # of presets, etc), V2 actually improves the sound in some important ways, which I didn't expect. The sound engine itself is not modified by the OS upgrade, but the new OS takes advantage of the sound engine's software controlability in some important new ways, resulting in a fatter, more B-3 like sound. It's amazing how much of the available software control WASN'T used in v1.x of the OS.

There are lots of new features extending the XB-2's programmability (a list follows this review), but to my ear, the most important are:

percussion level programmable to 16 levels
key tracking for percussion level taper as pitch rises
percussion level can be controlled by key velocity
key click level programmable to four levels
vibrato/chorus rate programmable to 5 levels
1' drawbar can be disabled by percussion tabs

I feel that the biggest deal here is the enhancements to percussion. The percussion in the old XB-2 was very shrill in the upper octaves, especially in the last octave. This made the XB-2 sound piercing and a bit nasal in the top octave. In an attempt to compensate for that I always used the percussion with the 'Soft' setting enabled, trading some of the classic Hammond attack transients for tone and high end playability. A problem with that is that 'Soft' percussion robs registrations like '888000000' of their punch, leaving you with a choice of shrill highs or muddy lows.

This problem is solved with V2. Selecting percussion 'key tracking' reduces the percussion level in the high end, making it possible to use louder percussion settings without inducing harshness in the high end. Further, since percussion can be programmed to any of 16 levels (plus Soft on/off), it is possible to set the percussion to satisfy any taste. This has the effect of making the XB-2 a fatter, more playable and versatile organ with improved tone and attack across all registers, making it tonally much more similar to a B-3.

Previously, key click level could be set to off, soft, and normal. The normal setting was the loudest available, yet still softer than some examples of real B3 key click I've heard. V2 adds a 'MAX keyclick' setting, which closes the gap. Oddly enough, MAX Keyclick seems to give the attack transient a noticeably beefier low end, so using 3rd Percussion at level 16 with MAX Keyclick will give you all the attack snap you'll ever want (and probably a lot more than you'd want). You might not use MAX Keyclick in all presets, but it's mighty nice to have this option.

The velocity control of percussion level is subtle, but introduces some interesting possibilities for expressive playing, especially when used in ballads or slow blues. When using velocity triggering for percussion I find that the percussion is pretty soft unless you really lean on the velocity. This can be compensated for by programming presets with velocity triggering to have slightly higher percussion levels. Since this feature isn't found on the B-3, purists probably might not use it and I myself find it of limited value, but some folks might consider it to be an important feature.

The percussion on a B-3 is single triggered, meaning that you only hear the percussion on the first note played after an all-notes-off state. This requires B-3 players to play non-legato if they want percussion to trigger on each note played. When playing fast licks, this can be a challenge. The XB-2 also plays this way, but in V2 you also have the option of having percussion trigger on ALL key strikes, not just the non-legato ones. So if your non-legato technique sucks, V2 gives you the option of cheating by triggering percussion on all key strikes, rather than just the non-legato ones.

Presets can be programmed so that the 1' Drawbar will be disabled when percussion is turned on, like a B-3.


In my opinion, the version 2 software provides major improvements to the sound, playability, and versatility of the XB-2. I consider the upgrade to be worth it's cost and much more. Any XB-2 player who is at all serious about getting a better traditional Hammond sound should consider this upgrade a must-have.

Version Checking

If an XB-2 has had version 2 installed, when you turn on the power the version number is displayed in the XB-2 LCD display. If you do not see the version number you are running an earlier version.

Doing The Upgrade

The upgrade includes two new ROM chips, a new and improved owners manual, and instructions on how to do the upgrade.

The XB-2 ROM upgrade is easily installed. The installation requires that you take the top of your XB-2, unplug two ROM chips from the sockets, and plug the two new ROM chips into the now empty sockets. You need to be careful that you don't bend the ROM chip legs when unplugging the old chips and plugging in the new one's or otherwise damage the chips, but anyone of even moderate mechanical skill should be able to manage this.

Various dealers are charging various prices for the upgrade hardware and installation labor. Some of the prices I've heard are unfairly high, especially outside the US, so beware. If you can install the upgrade yourself you can get it via mail order for $149 US plus the return of your old ROM chips. Ask on the Hammond mailing list as to where it's currently available via mail.

Version 2 Feature List

Following is a list of features in the version 2 upgrade with a note as to whether this is an enhancement over previous versions or a new feature. Thanks to John Pittas for getting this list together.

PRESETS BANKS -- New Feature

4 banks per preset for a total of 32 presets

VIBRATO - SPEED -- Enhancement

5 choices: slow, mid, normal, midfast & fast


Independent ON/OFF for upper and lower manuals in split mode


+/- 12 half steps, bender length independently selectable

PERCUSSION - TOUCH -- Enhancement

Touch & velocity independently selectable


16 volume levels for percussion


        8th harmonic drawbar silenced when percussion is active.  
        Selectable ON or OFF.


        Volume of percussion tapers off slightly at top end of keyboard.
        Selectable ON or OFF.


        Total of 9 functions: Leslie S/F, UM SUS, LM SUS, preset forward,
        MIDI start/stop, UM damper, LM damper, UL damper.

ATTACK MENU - (drawbar attack, keyclick) -- Enhancement

        Menu has been moved from the EFFECT Menu to the Drawbar Menu.  
        5 choices: slow attack, no click, soft, normal, max.

DRAWBAR - FOLDBACK -- Enhancement

Foldback points can be set by direct key input or scrolling.


        Drawbar volume changes can be sent to a connected sequencer 
        or other MIDI device via MIDI OUT.

LESLIE SPEED -- New Feature

        The slow & fast speed, rise and fall times of the internal 
        leslie effect can be adjusted.

MIDI - VELOCITY -- Enhancement

Increased to a total of 6 velocity curves

MIDI - IN SPLIT GATE -- New Feature

Incoming MIDI data can be set to not recognize keyboard split.


        Channel assignments from 1-16 for upper and lower manuals 
        and MIDI zones 1 & 2.  Also selectable ON & OFF for each for 
        UM, LM & zones.

MIDI - KEYMAPPING -- Enhancement

        High & low limits for upper and lower manual (split) and 
        MIDI zones 1 & 2.  Key assignment can be done by direct key 
        input and scrolling.


+/- 4 octaves from MIDI zones 1 & 2.


        Select the MIDI variation number for each zone.  Allows 
        XB-2 to work with Hammond GM-1000 sound module.


Set the volume level for each MIDI zone.


        Assignable control numbers for: foot switch, mod wheel, 
        expression pedal and leslie fast touch tab.


        Sends the current Cancel Mode setting to a sequencer in 
        preparation for playing back a sequence.

DATA DUMP -- Enhancement

        Total of 5 memory dump options for saving data 


        "Plus" or "Minus" polarity and alternate/momentary 
        mode selection.

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