Tone Generator Capacitor Replacement

The wax-and-paper caps used in the filter networks on the older ToneGenerators degrade with time (see CapacitorReplacement). In general, the capacitance of the wax-and-paper caps increases with age.

Undoubtedly, this strongly affects the tone of the organ.

Replacing TG caps will, correspondingly, drastically alter the sound of your organ.

Whether and how to replace the ToneGenerator capacitors is a hotly debated subject.

   Note: Around 1965 (I think) Hammond switched from wax-and-paper to mylar capacitors on their ToneGenerators.
   The mylar caps are much more stable.
   If your organ has mylar caps, you can probably safely bow out from this debate (and disregard the remainder of this page.

The Argument

Many people prefer (or have gotten used to) the mellower sound of aged capacitors. There are stories of tone generators which were "ruined" by capacitor replacement (the organs being saved only by the transplant of another tone generator (with original capacitors)). On the other hand, many swear by the brighter tone of a recapped tone generator. They argue that recapping restores the tone that was intended at the factory, and that, in any case, one can recover the mellow tone of the aged capacitors by pushing in the upper drawbars a bit.

Some claim that, should you decide to replace your tone generator capacitors, you really should individually match the value of each filter capacitor to it's filter coil (e.g. by using a capacitor substitution box and a spectrum analyzer to _peak_ the output of the tone generator.) They argue that this was what was done at the factory, and that to do otherwise will damage the balance between the levels of the various tones.

Others maintain that merely replacing the caps with caps of the correct nominal value will work fine.

What Kind of Capacitors?

There has been discussion on the lists about the type of capacitor used for recapping the TG. In addition, there have been claims that certain caps, chosen for their audio qualities should be used. Here is a link to a web page called The Sound of Capacitors - Capacitor Linearity. In it, experimental data is presented that provides a better clue of what to look for in a capacitor used for audio purposes.

FWIW, polypropylene "Orange Drops" have been recommended by one source who should know to be suitable replacements for TG filter caps.

User Stories

JohnMihevic has contributed this article on his (positive) experience with the Goff capacitor kit.

StefanVorkoetter has written a comprehensive article describing the why and how of tone generator capacitor replacement and subsequent recalibration: Hammond Organ Tonewheel Generator Capacitor Replacement and Calibration.

More on Replacement Capacitors for vibrato line and tone generator using vintage new old stock paper and oil

It all depends on your ear. I have a 1963 Hammond M-102 that sounds so good with its original paper and wax capacitors on the tone generator and vibrato box that I wouldn't dream of changing them. Have they gained in capacitance over the years? Yes, I'm sure, but there is alot of definition in the drawbars and all vibrato and chorus settings. So, I will leave it alone for now.

However, I purchased a 1957 Hammond C-3 a couple of years ago and it sounded absolutely terrible. Very little drawbar definition (very muddy with entirely too much bass). The vibrato and chorus settings were so dull and muddy sounding that you couldn't tell the differences between each setting (V1,2,3,C1,2,3 all sounded the same). It of course, had the original paper and wax capacitors and had degraded the true sound something fierce. (I can see why some people don't like the sound of these particular organs that do not have the later red mylar caps (polystyrene) (Mylar red capacitors were used starting around 1965, they should not be replaced because their values do not change over time).

I first replaced the capacitors in both line box and generator with the ceramics from Goff professional. This improved the definition greatly but they did sound very harsh, especially higher up on the keyboard.

After reading the article on capacitor linearity, I decided to purchase vintage new old stock paper and oil capacitors from Nebraska surplus sales and replace the ceramics from Goff professional. I replaced the vibrato line box with polystyrene (these sound very close to paper and oil) because I couldn't find the correct value in paper and oil. I used Gudeman paper and oil for the tone generator and the sound was improved immensely compared to ceramics or even the polypropylene capacitors they produce today. There is clear definition yet with smooth creamy sound throughout the entire range of tones. It is not muddy on the low end or harsh on the high end. I also replaced the paper and wax capacitors in the AO-28 with Sprague vitamin q's with the same value and voltages.

There are articles on the internet where "experts" tell you not to use vintage capacitors stating they are unreliable, poor tolerance, etc. I have found that the capacitors I purchased are very high quality well made pieces made in a by gone era (many are unused military surplus). Their tolerances were within a few percent if not exactly the value printed on them (much closer than the ten percent they are rated).

You do not need perfectly matching capacitors for the tone generator, you will not be able to hear the difference. However, because the organ was calibrated with the old paper and wax the tolerances will not be the same and some tones may be louder than others. I do not recommend recalibrating the entire tone generator (you could do more damage than its worth) only the few tones that may be significantly too loud/soft. If you decide to recalibrate the entire generator, at least, take voltage measurements before making adjustments, that way you can go back to them if your new settings are unsatisfactory. I found that the original calibration works perfectly fine with the replacement pio's (only one tone is a little louder than the rest and its not worth the bother of loosening the magnet and pulling it back). It is possible these capacitors will degrade in sound like the paper and wax sometime in the future, but I will probably be dead by then.

        * Note** Newly manufactured paper and wax and paper and oil made for high end stereo such as Ampohm, Jensen, Jupiter, etc. should not be used in any of these circuits. I tried them in the AO-28 before and I could hear generator noise because these types of caps are very detailed and are not designed for filter circuits. When I realized the mistake I made I put in the vintage vitamin q's and solved the problem. The manufacturer's actually tell you this in their spec sheets but I ignored their warning and wasted $100 bucks on four capacitors.

My Leslie 122A also received paper and oil caps replacing the polypropylene it came with (I did wait till the warranty expired, not that that really matters) and this improved the sound of the Leslie.

You will never be able to rebuild a Hammond that have paper and wax capacitors to sound exactly like it did factory new (just because these capacitors are no longer available). The vintage paper and wax that are sometimes available on ebay will probably be way out of spec. I believe you will be closest to the original creamy tone that you hear on old Jimmy Smith albums using vintage paper and oil.

Vintage paper and oil can not be beat for vintage type sound whether in a Hammond organ (pre mylar red capacitor)or Leslie.

-- Jason St. James

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