T500 Skill 2 Carsten Myer Vs Kon

[Pablo E. GarcÃa Palacios]

Hi there, Hammond Geeks!
There are 2 different versions for the "bass improvement" Skill 2. Carsten / Kon( kziss ).
The DRAWBAR BUS AMP BASS ROLL modification is supposed to have a GREAT impact in the sound, but after following Kon´s instructions, I have noticed no change in the sound of my T500.
Versions:

• Carsten (Keyboardpartner): REPLACE C240, C236, C232... (brown/orange mylar caps) by electrolytics 10uF/40V. REPLACE all electrolytics in row C237, C233, C229...by 47uF/25V. (post)
• Kon: KEEP the original capacitors C240, C236, C232... (input) , and solder 10uf bipolar capacitors on the underside of the circuit board in parallel. KEEP the original capacitors C237, C233, C229...(output) and solder 1 uf bipolar capacitors in parallel. (post)

As I said, I did Kon´s version, with the values stated in the instructions, but using electrolytics instead of bipolars. No change at all (at least, that I can notice...).
I haven´t removed the
Any thoughts about this?
These are pretty common mods that have been used a lot, so I suppose that there will be a lot of you with this mod already done... ( Brendon Wright , RatRod ...)
Thanks in advance!!

[RatRod]

Hey Pablo, how's it going?

For the Bass roll-off mod, I used Kon's technique. Antique electronic supplies had bipolar caps in axial can packages, but the 10uF's were sold out. I read up on the downsides of MLCC caps (they are non electrolytic ceramic for higher values in smaller space, using multi layers) and I went ahead and tried them, as they really had no proximity issues in this application.

The results for me were subtle but evident. Really pronounced in the lows and mids of the manuals. I could hear a punchy attack and the ambient leakage of the adjacent pick-ups. Not the tones themselves, mind you, but the soft rumble. On the upper manual, the percussion "pip" of the short-decay presets "celeste, marimba" had more tonal content, I believe because the effect is accumulated by the parallel resistors in the r-packs.

Now with your specific application...
In the attached pic, you can observe that polarization will matter when piggyback soldering C-237, etc. (it should match the original cap) as the input side does couple a small signal from some distance away. C-240, being non polarized, will be passive to DC and high-pass to AC. Your piggyback cap should be (+) towards the top (DC blocking the transistor output). The values in Carsten's mod work out to be slightly higher letting more bass through, but I was pleased with the results, using Kon's mod. In either case, we are listening for a change that is part physical and mechanical, part purely frequency and tone.



Not sure which way Brenden went on this, probably a combination?
Take care
RatRod

[Pablo E. GarcÃa Palacios]

Hi RatRod! Thx for your comment.
I get what you say, but there's a big difference between the two methods: kon's mod applies the new capacitors in parallel with the originals. As the originals have different uF values you are adding a fixed uF value and the result is that every input/output has a different value. But Carsten's is about replacing the originals capacitors with fixed values, so you will have the same uF in each i/o of the manual...
That's the part that I don't get...
(I placed the new caps with the anode pointing up, to the transistors, matching the og).
Could the cause be that I didn't use bipolares?
regards

[RatRod]

You should be fine with polarized EL caps, because they are working in the correct direction. Kon's mod is the later iteration of the bass roll-off mods, where Carsten's simply "opened up the floodgates" with the larger 47uF on the intake, Kon experimented with the "just low enough" value to incorporate the bass-specific part of each busbar's range. On the output end, that 10uF value should look pretty familiar to you, just like the dozens of other stage coupling caps throughout the circuitry. Carsten's mod let's all of the audio content through except the lowest lows, while Kon's has a higher roll-off for each next higher busbar. He does mention trying to match same frequency level on different busbars in the post. If you wanted to compare the effectiveness of both mods, you could do Carsten's on the 8' lower bus amp and Kon's on the 8' upper then isolate those two drawbars full out. But play the entire manual range before you choose a preference. Use some good headphones on your pre-amp to listen for the TG ambience, and attack on keying.

Question: In your original post, were you saying you have not removed the original caps (which I presumed), or that you haven't done the "miller cap" filter mod yet?

Hope this helps
RatRod

[Pablo E. GarcÃa Palacios]

In your original post, were you saying you have not removed the original caps (which I presumed), or that you haven't done the "miller cap" filter mod yet?

I did the Skill 1 for the key clic, so i removed the first 4 caps (from the right), but I did not remove the 3 caps on the left side, because Carsten states to modify the recovery if you remove those, and for now I don´t want to do the "Skill 2-Filter issues". Trying to do it one step at a time so I can see the changes...
So in my original post I was refering to the caps in the bottom of the board (skill 2), Kon keeps them, Carsten remove them....
My lower and upper don´t sound the same. I like that because is like having 2 organs in one ;-) . But that means I can´t compare side by side, although maybe is a good idea.
Sould I go for the recovery´s mod??

[RatRod]

Hi again Pablo,
I am curious about how different the upper/lower manual final sounds are? With the auto-chord PCB removed and jumpered across 4 to 6, as you have done, is there a difference in tone or just level? You should be able to isolate one bus bar on each (8' covers the whole manuals) and find the tones close enough to compare.

For the non-vibrato recovery PCB, the filter mod will affect both upper/lower equally. The price for a wider-richer curve here is a little bit more click ("bip, bip") on the lowest 8 to 10 keys.
If your upper/lower difference is still drastic, or if either manual sounds "thin or nasal" you might want to replace the two electrolytics (6.8uF/25V) C-851 & C-854 in the recovery buffer amps. They are on separate signal paths, and have likely taken a beating and drifted over the years, from tab switches and bass pedals.

In my case, both the recovery boards were hanging inside the organ by the wires and the vibrato was completely disabled, lots of repairs, so I did that first and performed the filter-curve mod then, as well as new caps, transistors and pin connectors. Both manuals did work, though, and I was able to hear the difference that the mod made.

Feel free to PM me if you need more details/pics.
Take care Pablo
RatRod

[Pablo E. GarcÃa Palacios]

Late reply... sorry, a lot going on lately...
The difference in sound is not so huge actually, maybe the bright of the mid frecuencies are lower, something I can sense, but not a big deal. I like it.
I have not changed C-851 & C-854 from the recovery, so that´s my next step, I think this could improve the sound for sure, thx for the tip. Then later I can do the complete filter-curve recovery mod... Anyway I think I will just remove the original capacitors from the upper manual as stated in board Carsten M. because I could not notice anything adding the caps in parallel. Let´s see if that makes the difference...
Maybe more click is too much. I just bought a Leslie (760 tube modified) and the click is so great now!!!!!!!! Amazing how the leslie can define/change/improve the organ sound...