Most of the points where these two organs differ can be customized to make the L sound closer to a B. The L in it stock state without a Leslie and played through the internal speakers is a real dull sounding instrument compared to a roaring B with its key click and the way it bites. An L is a mere whisper in this shape. Add a Leslie and things get better. But still.

Here is a list of where they differ in sound and in part why. I will try to give you suggestions on how to improve it.

I can and will not take any responsibility for any damages that may result from any of these modifications. It up to each individual to check that you donut violate any National or international laws regarding electrical safety when you modify your Hammond. It is also uncertain weather some of these mods are acceptable in regards to The various CE directives here in europe. This definitely applies to any circuitry that you build yourself and then install into your Organ. The Ce directives roughly states that you may change the handle on and the head of a broom 100 times and it is considered to be the same broom. But if you put on a modified shaft it is considered to be a new broom and should undergo CE marking and testing. The problem really arises when you sell a or put an modified instrument on the market ( this actually includes theft. If the instrument is stolen it is considered to be on the market)

You should also be certain to use products that have the correct Voltage ratings since there are very High Voltages in your instrument.

If you are in any way uncertain about the safety of certain modification donut do it.

And if you are in any doubt regarding your technical skills have a tech do it for you. This makes him liable. And remember if you are dead you will have not be able to enjoy you Hammond any more.

High Voltage Kills you very effectively.

Always disconnect from mains and drain your filtering condensers with a resistor (47k 5 W ).

• Keycklick
• TG- Recallibration
• Percussion
•  Vibrato
•  Swell pedal
• Octavider for the lower manual
• Input Transformer
•  Foldback
• The fixed settings of the TABS
•  Back home



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Keyklick

The electrical click which everybody loves on a B was regarded as a serious fault by the Hammond factory. They where competing with church organs and a pipe organ does not have an audible click at the beginning of the note. I guess they put a lot of effort into reducing it as much as they could. And with the L´s they really succeeded. To the dismay of us jazz freaks the L has very little click in the tone. How did they do this?

They raised the output of the higher notes in the tone generator (TG). To counter this increase they cut the treble response in several of the amp stages. The idea was to increase the "Click" to tone ratio compared to the B. And they succeeded. The M has a similar cut in the frequency response of the amp but I haven't tested it as thoroughly as on the L.

The remedy for all of this is to restore a flat response in the amps and to recallibrate the TG.

One difference that will reside after having changed the amps and the TG is how the actual click sounds. I suspect that (although i haven't confirmed it yet) that the hey contacts differ somewhat. When I used a storage scope and look at the click. The B´s contacts seemed to bounce a few times more than the L´s. The length of the click sound on my L is about 2,5 - 5 ms with about 5 - 8 clearly visible bounces. I a remember it the B had a little tighter and higher number.

The scanner plays a part in the click sound to . When you turn on the vibrato on a B with the chorus on ( C 1 - 3 ) you get a in increase in the high frequency response. The scanner also acts a a short delay. Which further increases the perceived click. The cabinet set up will of course affect how much key click is being heard.
 

What to do.

The very first step is to change the frequency response of the first amplifier stage. In stock state the curve of this amp falls and falls and...... .
To correct this you can do a number of things.

Remove C 203 all together.
This will give you loads of keycklick but the organ will become a little (Or very depending on Amplification) shrill in the 4´ and 5 1/3´ drawbars. On the other hand the organ will punch through any rock band like a knife :-)

Put a 1.8 meg resistor in series with the C 203.
This will roll of the treble and some of the middle and it will flatten out. This increases the keycklick substantially but it doesn't make the organ as shrill sounding as the first example.



Put a 1.8 meg resistor in series with the C 203 and change R 203 to 10 meg.
This will make your organ sound a little "Fatter" than the example above. Its really a matter
of taste.



Remove C 310.
Increases the treble somewhat.

Removing C 314
This condenser limits the frequency response of the power amp. With it installed the response falls off rapidly from 6000 hz. And adverse effect of leaving it in place is that since the response of the rest of the chain is flattened out by the mods above it means that R 355 tries to short out all the treble we are feeding the amp from the earlier stages. I have tried to find a combination of values that will limit the amp say from 25000 hz but most other combinations sent the amp into solid HF oscillation. If any of you guys out there know of a workable value combination for C 314 and R 355 that works form 25000 Hz mail me and Ill include it here.
The downside of this mod is that it may make the amp go into oscillation but I have not noticed it yet. This does not mean that it doesn't happen.
 

In addition to the above there are a few points where you may increase the treble response of the amp by bypassing some resistors with condensers.

Resistors to bypass with condensers.
R 304 470p
R 319 220k
180pF - 1nf  (my organ has 470p)
R 323 47000
820pf-2,2nF
 R 307
180pf - 1nF (my organ has 330p)
 




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Tone Generator recallibration

Since the output of the TG is raised with increasing note number as compared to the B-3 this is an area for improvement. Lowering the treble side of the TG also means that level of the keyklick is brought closer to the surface. It is to be noted that the tech's at Hammond considered the keyclick to be an inherent fault in the Organ and not the lovely effect we see it as. So what they did was to raise the level of the treble notes. This increased the signal to click ratio. They then lowered the level of the treble notes by rolling ot the treble in the amps and this way the organ had a flat tonal response. The end result. Less keyclick but in our world it made the organs boring. In the examples above i show how to restore the frequency response. The next step is to lower the TG´s top notes (ca: 38 and upwards) to a level that restores the tonal response of your organ. There are two main options to choose from.
The simplest involves putting in a lot of trim pots and resistors. The harder route is to move the magnets. Unless you are skilled at doing this I donut really recommend it. You should have access to a good mV meter to do this so you can see where you are going. There is also the danger of damaging your tone wheels in the process.
The other route to go is to install trim pots to shunt some of the signal to ground. This option is safe and also spares you of having to remove the TG from the Organ. Since the problem in the L-100 is one of to much signal this is the best way according to my opinion. It also means that you quite easily can change your settings with relative ease.
I have not made this mod in the way I describe here. On my organ i have used a series trim pot.
This has the drawback of raising the impedance of the circuit which affects the output.
The way i describe should work better since it lowers or keep the impedance the same.
It is being tested at the moment by a friend of mine (Pontus) and as soon as he reports in i will report the outcome.

Here is how it is done.

You put one resistor (On some notes this is not needed) in series with the coil. The trimmer pot is then connected to earth to shunt away an appropriate amount of signal. If done with a little care and thought this will not affect the impedance of the circuit very much.

You will need the following material
 

• 60 or so trim potentiometers. The lowest value you can find. The value depends on where you start. The first notes affected will have very little reduction to make it the organ sound even. These notes can take a higher value for the pot and no series resistor
• One series resistor for each one of the above to restore the impedance of the circuit.
• A piece off stiff 0.75 mm2 - 1.5 mm2 wire
If done 100 % correct each coil should be tested for its impedance. When you have trimmed the level you should could insert a resistor of an appropriate value to restore the impedance and then recallibrate. I'm not 100% certain that the series resistor is needed. I will have to test this myself before making a positive statement about it.
 
• Desolder the lead leading from the TG (Black cable)
• Solder in the pot and tie the middle leg to on of the end legs
• Solder the leg that is not tied together with the middle leg to lug of the TG where the black cable was.
• Solder the other side of the pot to the ground wire
• Solder the ground wire to the ground lug in the middle of the TG
• Then comes the task of adjusting the tones. This is really a matter of personal taste.
• If needed insert a series resistor between the black lead and the lug on the TG where the top end of the trimmer pot is situated.
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Percussion

There are a lot of differences in the percussion amp systems of the two organs. The B uses a a push-pull tube amp with an output transformer. It also has an input transformer. The main audible difference is of course the length of the percussion. The L has a longer duration. The short decay of the L is almost as long as the long one on the B. The solution for this is to modify the percussion amp to set the decays to match those of a B. Here is an example from my L.

I also suspect that some of the difference is due to how the amps distort when they cut the signal out. I haven't confirmed it but the percussion on a B sounds a little dirtier that L. Perhaps running the percussion signal through a distorsion stage might help.

What to do:

Length of the decay

Change C210 from .33 mF to 68n
Parallel R 409 2.2m with 1.8m
Put a resistor in series with R219 3.9 meg. Suggested value 2.2m

I´m pointing at the condenser that controls the percussion length.

Treble response

Change C 208 to a lover value (680 p).
Or remove it altogether. You could also put in a trimmer pot in series with the original condenser to make the treble adjustable.


 

Transformer input.
On my organ i have added an transformer on the input. I used an transformer that was intended to be used as an output transformer for small transistor amps. I think the ratio was 3:1. I turned it around and feed it from the secondary (Low impedance side). I removed r 207. This gave me more percussion. If you do this it is important to take the ground to the input side from the central ground lug by the drawbars. Use quit thick wires for this. Otherwise you will get hum problems.

Added gain.
On my organ i have disconnected the vibrato amp since i use the Boss RCE10 for this purpose. I have rebuilt on of the 12au7´s to a standard amp configuration. I feed the percussion from from the top side of  R223   to  this amp and then attenuate it with a pot and send it back to to R222 which is freed from R223. This way i get as much or as little percussion as i want.

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Vibrato - Chorus

The vibrato and chorus is a real weak point of the L. The vibrato is either to much or to little and the chorus effect is a joke when compared to the richness of the B.

On day when tinkering with my L i saw a Boss RCE 10 chorus unit sitting on a shelf. I had bought it for my bass but it had been left unused when i switched to using a programmable unit for my bass. I looked at it and wondered how i would sound. First I tried using the A output. The slow chorus was ok but any attempts to copy the fast effect of a B sounded strange. So I tried the B output. And there it was.

This how the chorus sounds.

How to set it up

 Use the B output and set i roughly like this. (The A output will sound awful) . The numbers referee to the the clock.
• Find a spot on the predelay that doesn't filter the bass to much. Around 9.
•  Ratio. Ca: 3 a´clock . But the important thing is to time it with the Leslie. Not absolutely the same but close.
•  Depth. Ca: 9 a´clock.
•  EQ Depending on your setup with amps and Leslie. 12 a´clock - max.

Other units

Pontus has tried both the RCE10 and a unit from TC electronics. TC made a pedal chorus that is a legend almost these days. His opinion is that the TC in chorus mode sounds better than the RCE10. Other units may of course work equally well or better than these to suggested by us.




Where to put it

There are some options here. One problem is that signal level is so high inside the organ.
the "correct" place to insert it instead of the old unit. If you do you will have problems with distortion. On Mr. Tibells organ we solved this by reducing the level to the TG with a Voltage divider network. Use a pot of at least 250 k. And we then used one of the 12au7 tubes to boost the gain back again. Back to index

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The Volume / Swell pedal

This is one of the greater obstacles to overcome. The B uses a variable condenser where the center set of plates varies from on side with a filter that cuts the midrange much more than the bass and treble. And the other side which is full blast. This design is pure genius.
• Its fool proof. Nothing that can Wear out. No contacts and no pot that will become scratchy with age.
• The filter effect when you step on it acts like a variable parametric eq. It flattens the response at the same time as it increases the volume.
•  It is a whaw wah pedal in a way.
Now the L on the other hand uses a Light sensitive resistor. It is as fool proof and quiet as the B (with the exemption that the bulb blows once every 50 years or so) but it comes no way near in terms of swell effect. Also the volume range is not as great.

I have redesigned my pedal using 2 Light sensitive resistors and a frequency shaping network. It is a great improvement but the best thing would be to go all the way and build a replica of an B Swell pedal.

What I´ve done is as follows.
Take out the original LDR.(Light dependent resistor)
Replace it with two smaller ones that will fit inside. They should have quite high impendance in the cut off state. 1 meg or should do the trick. I also removed to opaque disk on my organ to get the right feel. Here you have to experiment depending on the LDR´s you use.
Then build a network as follows. It is inserted in the same place as the old one.
You will need to boost the signal ca 20 times. In my organ this is this has been solved by using one of the left over vibrato 12au7´s. This will boost the signal enough to compensate for the increased attenuation. You will have to use both sides of the tube. The first will amplify and the second half will be a kathode follower.
 






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Octavider for the lower manual

I was greatly dissapointed when i discovered that I could not play bass on the lower manual of my L. Being a bass player this was a major drawback. The good side in the beginning was that I ws forced to learn how to play walking lines on the pedals. But I wanted to be able to play bass with my left hand. One day when I was playing my eyes landed on a boss Oc2 octavider that was sitting on a shelf. Could I use this. After quite a lot of experimenting I had it working and it sounded great. (At least I think so :-))

Materials:

• Octavider. I have used the OC2 by Boss. There are other that probably would work equally well or better. As you test other units report it to me so I can make the information available here
• An LM 386 or similar IC to drive the low impedance of the drawbar input.
• On the L-100 p you also will need a relay or two for switching the octavider in and out. You will have to switch 7 lines.
 On a Standard L you can use the TAB for the lower manual to switch the Octavider in and out. Or you can use relays.
What you do is to reroute the the 8´ drawbar to the input of the octavider. It might be a good idea to insert a good microphone preamp here to improve the S/N in the octavider. I haven't tried this yet but it makes good sense i think. If you have a microphone transformer laying about you could use that to boos your signal 5:1. Since the input impedance of most pedals is in the 100k - 1Meg range you could use a higher ratio than 5:1 if you can find it. If you can find a transformer with a high enough ratio you could skip the pre amp altogether.

On the output side of the Octavider you will need to either transform down 10k - 4 ohms or to use an low power ic capable of driving a 4 ohm load. Supplied here will be a drawing for using the LM 386. The drawback to this IC is that it is a little noisy but there are others around. I used it since I happened to have one in my toolbox at the time I made this mod.
 

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Input transformer and drawbars

The input design of the B & L differ as follows.
• The B uses taps on the transformer. There are 8 taps. The intermediate volume steps are accomplished with and 1 ohm resistor on the Drawbar itself.
• The L uses a resistor ladder and the drawbars connects to different taps on this ladder.
One drawback with L system is that the input transformer sees a closed circuit with the input leads forming a loop. This is why you can hear all the tones hum in the background. On my L I have solved it by opening the transformer and rewinding it to B3 standard. I can't really say if it improved the actual sound of the organ but it made it quiet when no note is being played. But I had a feeling that the organ sounded better but it is so easy to fool yourself.
 

Warning: Unless you are 100% sure that you want to try this and that you are aware that it is basically a no return mod don't do it.

There are two stages to this mod.

Mods on the drawbar side

1. Remove the printed circuit board at the end of the drawbarbox. (The right side) When you do this you will probably destroy it so this one reason why this is a one way street operation.
2. Remove the bent part of the buss bars so that an equal amount protrudes
3. There are 17 buss bars all in all
4. Add a 1 Ohm resistor between the second buss bar (The one that is in contact with the drawbar when it is fully pushed home i.e position 0) and the third
5. The next 1 ohm goes between no 4 and 5
6. The next 1 ohm goes between no 6 and 7
7. The next 1 ohm goes between no 8 and 9
8. The next 1 ohm goes between no 10 and 11
9. The next 1 ohm goes between no 12 and 13
10. The next 1 ohm goes between no 14 and 15
11. The next 1 ohm goes between no 16 and 17
12. Solder 9 leads as follows Use at least 1 mm diameter wire (Core). They should be long enough to reach to the preamp box.
13. Black to bar no 1
14. Brown to bar no 3
15. Red to bar no 5
16. Orange to bar no 7
17. Yellow to bar no 9
18. Green to bar no 11
19. Blue to bar no 13
20. Violett to bar no 15
21. Grey to bar no 17




Showing the Drawbar assy after the printed circuit board has been removed and the resistors have been added.

Mods on the input transformer

1. Mark the leads to the transformer so you know which one goes where.
2. Unsolder the leads and then remove the transformer.
3. If you decide to try this mod you will have to carefully unsolder (Big 175 W Iron) the copper shield around the Input transformer.
4. The next step is unwrap the waxed paper surrounding the transformer.
5. Make notes of the direction of the windings and how it is wound.
6. Measure and obtain the same gauge lacquered wire.
7. now start the rewinding process.

The idea behind the original drawbar and input transformer is that the bussbar in the manuals are connected to different taps on the input transformer with the aid of the drawbars. If you have your drawbar pushed all the way in the signal is grounded.
If you have the drawbar in the first position you route the signal through the 1 ohm resistor to the first tap on the transformer which is about one turn. The next position gives direct routing to the first tap and so forth.

When you wind the transformer keep the windings tight and neat. At the point where you are going to connect a lead you make a little "Hoop". It´s not a full loop.
Then you take a small file and file of the lacquer. Fully wind  and prepare the transformer and the solder the leads from the drawbars to their Hoops.
If you are really ambitious you will make a new metal cover to case and screen the transformer. On my organs I haven't done so and it seems to work.
The taps on the transformer are as follow
 

8. Ground side to bar no 1 = Volume step 0
9. 1 turn later  bar nr 3 = Volume step 1
10. 1 turn later bar nr 5 = Volume step 2
11. 2 turns later bar no 7 = Volume step 3
12. 3 turns later bar no 9 = Volume step 4
13. 5 turns later bar no 11 = Volume step 5
14. 8 turns later bar no 13 = Volume step 6
15. 8 turns later bar no 15 = Volume step 7
16. 11 turns later wick is the end of the winding, bar no 17 = Volume step 8




Pointing at the 8 wires that comes from the taps on the input transformer.

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