Hammond T-522 Tone-wheel Organ.

Hammond made both great and crappy organs. The definitive turning point was the abandoning of tone wheels in the organs. Until then Hammond had made many changes to their organ designs. The T-series organs were all-transistorized organs, except for the tone-wheel and the mechanical scanner vibrato.

The very last tone-wheel organs was the T-500-series, which was a continuation of the T-100 to T-400 series. It is almost identical to the T-100 to T-400 organs, but as with any revision some of the circuitry had again been redesigned. The chorus/vibrato was now individually selectable for upper and lower manual. Definitely an improvement. Hammond also integrated the Rythm III unit directly into the lower manual/bas pedal signal line, so that lower manual and bass pedals came under rythm control. Not an improvement to my tastes. Finally they added an internal Leslie and Leslie 700-series socket. Definitely an improvement.

From a commercial perspective, there is no doubt that the inclusion of rythm accompainment was targeted at the home organ market, rather than the professional market. This was further emphasized by the cheesy looks and the inclusion of a cassette recorder! Hammond deliberately tried to kill the key click inherent in Hammond organs. This must have been yet another attempt to accomodate the home organ and church organ markets.

With the T-500, Hammond succeeded in totally suppressing the key click. Sadly, in this proces, most of the character of the tone wheel sound was killed too. Therefore T-500 series organs are among the least sought after Hammond organs on the market, with a value ranking only slightly above the japanese built LSI all-transistor Hammond wonders, and indeed mine cost me only the equivalent of 100 Euro!!!

This is totally unjustified, and here is the reason:

The T-500 organs are easily modifiable, at very little expense, using a soldering iron and a few extra components. In fact, recently it seems that the T-series is quickly becoming a favourite for amateur DIY Hammond modification, as may be witnessed over at http://www.organforum.com.

Being one of those amateurs, I followed the instructions found at http://www.keyboardpartner.de/hammond/t-modifications.htm, and despite me being an electronics amateur, it really wasn't very difficult to do. The components needed cost only another 20 Euro. Also, given the ridiculously low price tag of this organ, I decided that I could afford the experiment. So a few late night sessions later the organ had totally changed character.

The keyboardpartner modifications introduce a B-3-like frequency response in the preamps, the key click is revived from the dead, and the general equalisation of the drawbars is modified in favour of more low end. Finally the percussion modification brings a return to "single-trig", as on most Hammonds, and the percussion voices are changed to function like the L-100 percussion.

Add to this the important fact that the sound is still produced by true tone-wheels, and, not the least, the chorus is based on a true mechanical scanner-vibrato. Then you have an organ with a sound much more reckognizable as "the true Hammond sound", no matter if played through the internal speaker or through external Leslie. I spent some time modifying this organ, plus some time repairing a few things like a broken reverb and an inaudible bass pedal. I learned a lot in this proces, and I even made my own mod - an effects insert loop (see below). But it was worthwhile.
Compared to my stock Hammond L-100, I would say that the T-522 is closer to the B-3/A-100/M-100 category of sound than stock my L-100 is. Listen for yourself below.

There are many more modifications that can be made. On organforum.com members suggest more modifications to frequency response. One suggestion by Brendon Wright uses an inductor/capacitor pair to enhance key click further. Another mod suggested by Kon Zissis sets up pairs of zener diodes to add clipping distortion to the sound. Since most of the organ works with low voltage and discrete components, there really are few limitations to the mods that may be made.

Features:

Two keyboards of 3 1/2 octaves
9 upper drawbars; 16', 5' 1/3, 8', 4', 2' 2/3, 2' ,1' 3/5 ,1' 2/3,. 1',
Upper presets Drawbars, String 8', Full Tibias 16' and Theatre Brass 16' tabs.
Upper percussion (stock configuration): Chimes, Celesta, Guitar, Marimba, Xylophone, Banjo tabs.
(Quite frankly, I was happy to modify these into "correct" percussion settings)
Reiteration tab (repetitive trig of percussion)
Reiteration speed knob
Vibrato/Celeste, Vibrato Small, Vibrato/Chorus, Upper On/Off, Lower On/Off tabs
7 lower drawbars; 8', 4', 2' 2/3, 2', 1' 3/5, 1' 1/3, 1'
Lower presets Drawbars, Ensemble 8' tabs.
Bass pedal drawbar 16'/8'
Reverb I and II tabs
Brightness tab
Soft volume tab
All-transistor circuits
Built-in Leslie controller for 700-series Leslie
Pedal decay, pedal 16'/8', pedal mute, Leslie/internal amp, add internal amp, Leslie fast/slow switches.
Rythm III unit with numerous corny features and beats.

Audio samples of the vanilla T-522:

Admitted, I am not a great player, but the issue here is the sound and not me as a player, so don't listen for the playing, but listen for the organ sound.

InFocus	Example of vibrato on lower manual only
JimmyST500	Jazzy setting
KarnEvil	Brilliance and vibrato on upper manual only
KillerTone	Clean organ sound in Hugh Banton of Van der Graaf style
Kindness	Another clean organ sound in Kerry Minnear of Gentle Giant style
LeslieSpin	The sound of the internal Leslie at fast and slow speed
LetItTonewheel	The mighty sound of the mechanical scanner vibrato, set to the notes of a famous anthem.
Percussive	Different settings of the modified percussion section.
Reiterate	Example of the percussion reiterate setting.
SpittingImage	Hammond chops and key click highlighted.
ToneEdit	Organ played while tone is being modified.
ValentyneSplit	Clean lower manual and upper with chorus.
ValentyneSplitBrilliance	Same as above but with brilliance.

This is how the samples of the internal Leslie were recorded:

As you can see, just two microphones. One from the side and one from the front. So what you hear is the genuine sound of the organ itself with no extra effects. It would be really nice to hear the difference if a valve was added to the final amp stages. But more about that later... And as the next set of samples testify, it sounds even better through the Leslie 760 I have.

Audio samples of the T-522 through Leslie 760:

Here are some more samples that were recorded through the top rotating horn of a Leslie 760. Notice how the cross-over distortion is enough to give it a characteristic rough edge.
I recorded this to make a point about the sound: You don't necessarily need a B3 through a 147 to produce a good Hammond tone. An all-transistor amp T500-through-760-setup can be a viable and much cheaper alternative. With the Leslie the key-click becomes much more prominent.
(The playing is still embarassing, but I want the organ sound to be in focus.)

Chops	Typical rock Hammond setting. The distortion comes from the 760 itself.
GlassHouse	The big clean Hammond. Compare with the "Kindness" sound above to compare internal Leslie to the 760.
WakeEmRSon	A few classic 1970'ies Hammond figures from Wakeman and Emerson, played on T500 and Leslie 760.

My own effects insert into the T-522

Even though the organ at this point sounds good, I decided that I still missed that extra growl of a valve. The T-500 modification page mentioned above does have a page for adding a valve based recovery amp. But alas, it is based on an obscure russian valve, and a circuit that you have to buy from the guy. And then you discover that this circuit is not even available anymore. :-(
Therefore I decided to make an effects insert instead. I decided to put it at pin 3 of the recovery amp, as that is a 600mV P-P signal for the power amp. Pin 2 is ground. So it was easy to add two jack plugs and a true bypass switch.


Is this the built-in cassette player? Lids off!	No, it's an effects insert with a bypass switch!

I ripped out the guts of the cassette player (that didn't work anyway!). The holes left by the tape drive exactly fits the jack plugs and the switch I mounted. With the original cassette deck lid, the mod is concealed and the organ appears original. The mod is totally reversible, and no extra holes were drilled.

Insert valve overdrive in effects send

It is now possible to add any effect into the circuit. I went for a Vox Big Ben overdrive, which is based on a 12AU7 preamp valve. This pedal is very transparent with respect to frequency, meaning that the low end of the sound is preserved. The pedal gives all degrees of valve overdrive, and most settings sound good. Below is a couple of sound samples of the organ without and with the Vox inserted:

DrawbarPull	Pulling different drawbars through the overdrive to show the effect of each drawbar on the sound. Hmmm, I think I need to clean those drawbars!
NiceAndBig	Overdrive with a low gain setting gives more subtle results.
OffOn	Starts without overdrive and then adds overdrive. Notice how transparent the Vox appears to be.
RoughStart	Starts with medium overdrive gain and then lowers gain. Notice how the key click gets accentuated.
RockOrgan	Only medium gain used, but a drawbar setting with 8' on max makes the overdrive kick. Lower manual used for left hand, and the left hand key click also gets accentuated. Overdrive is switched off and on for comparison.
Echoes	Gain fairly high and 16' and 8' drawbar, combined with lower manual.

Insert compressor to enhance key-click

The key-click is badly missed on the T-522, but the modifications above will let some click pass through. Here is a trick that will enhance the key-click even more:

The effects insert is great with the Vox overdrive, but by inserting a compressor instead, it is possible to really emphasise the key-click. I have tried with several combinations of settings, some of which include a filter on the trigger signal. The results can be heard in sample 1-6 below. Judge for yourself below:

Key click sample 1	First a little figure played without the compressor, then a similar figure with the compressor. Both have the (modified) percussion tab on.
Key click sample 2	Running up and down the keyboard with a finger twice without the compressor, then twice again with the compressor.
Plain chords	played with the compressor on. There is no percussion applied here.
Key click sample 4	Now going to the extreme, with a compressor setting that virtually isolates the attack. This just goes to show how much you can actually enhance the key click.
Key click sample 5	808000003, playing With a Little Help From My Friends with the compressor on.
Key click sample 6	Some more noodling with a rock setting, persussion and the compressor on my favourite setting.

I eventually settled on a plain compressor setting with an attack of 2 ms, release of 0.05 ms, threshold of about -18 db, and a massive ratio of 1:infinity plus gain make up. This will make the key click pleasantly pronounced without destroying the sound. Combine this with a proper recording setup with two mics on the Leslie horn, an SM57 at the bottom, and now you have a very different sound from the initial samples at the top of this page. This can be heard in samples 8 to 10:

Key click sample 8	888000000, Walking in the Park.
Key click sample 9	008000001, With A Little Help From My Friends.
Key click sample 10	846050003, The Sleepwalkers.

Insert tape delay

If you are anything like me you have always listened in amazement to the magic of Richard Wright in the early Floyd. However, the type of sounds he made were made with simple technologies such as organs, distortions and delays. The following samples were made by inserting the Vox valve overdrive, followed by an old JMX tape delay machine to the effects send, and then recorded through the 760. The samples are very long, but I think the tonal magic is there too, so here's a timewarp back to the 60'ies:

Tape echo sample 1

Tape echo sample 2

Tape echo sample 3