On the 250k vs 100k pot; It's a voltage divider, but the difference makes the circuit to have a increased load on the plate with a 100k pot.  With 250k you have beside the pot behaviour more volume due to the decreased load. I'll bet it feels and plays different.

Well if you want to know the inside, you beter learn some basic electronics. Otherwise it's impossible to explain what's happening in other amps.

OTS is very close to some original dumble. But the OTS is one design/tweak. Leaving the layout the same, there are much variations possible in picking the right cap/resistor value. It has a huge impact on the sound. Dumble did this to match the players input and guitar. That's why there are many variations in the originals.
If you're looking  for a brighter sound, try the EVM12L speaker; you'll love it...

For me personally: choke was 4H, changed to 10H, made my amp less hairy, and less compressing. Improved low end. It has a wider dynamic range due to that choke.
Also the LNFB can be tuned with the resistors and cap. that way you can make a knee in your frequency and this affects the compression.
Snubbers across v2; original is 330pF, I changed it to 250pF. More highs.
Resistor after coupling cap v2b was 180 k, now it is 150k more highs and punchier.
Bright cap across master 68pF more highs. and so on; there are countless options...
All is tuned for use with my dumblelator(or Clator if you're not familiar with the nomenclature).

FWIW my amps clean channel sounded almost the same as a Van Weelden when I used a cab with 2x12 EVM12L. The drive channel was diffrent, I liked mine better, but YMMV.

FWIW the specs of RF amp are worthless without a dumblelator.
I remember you(Emiel) played on my amp with your guitar; it was flabby. My guitar didnt sound flabby.
So you have to pick brighter pick-ups or mod your OTS to get a tighter bass and more highs. There are a lot of other things to try.
Fe. try EVM12L speakers. I think you will be pleased...

I modded several OTS and noticed that most users listen from a very different perspective.  Fe. too much lows can also mean too less highs. Translation is different for someone who is modding.
So; "1 fits all" mod doesnt seem to apply to the OTS because it is so sensitive to a your playing and the guitar you use.

150k vs 220k slope resistor has a big imapct on the sensitivity of the tonestack.

True; always double check the components. I've had several occasions where the value of a resistor or cap was out of its spec. Changing it to on spec made the amp more brown.

Hi Emiel,

Sm57 with overtone and g12-65 is a perfect couple to record, so far I haven't found anything better in this pricerange.

OTS with fuchs verberator; I'll bet that sounds awesome!

Patch cables have, like every cable, a capacitance. The "amount" of capacitance is expressed in pF(picofarad).
It's like having a capacitor between your signal wire and ground. If the capacitance is high, lots of high tones are send to ground. If the capacitance is low, their still is high freq send to ground but not as much as a high capacitance cable.

Due to the circuit, the fx send return on the ots is very sensitive to the capacitance of the patch cables. 

So yes; it is important.

To get things straight: The cathode follower in the dumblelator adds a little compression but is from a tonal perspective hifi.
The recovery triode has a larger impact on the frequency response; works a little bit like a compressor and has a high frequency roll off. Together with the cables from the send and return it even has a larger impact on the high frequency.

So in other words; the dumblelator is not a transperant loop. It adds compression, filters highs and to my ears makes the OD tones more pleasant.
I would advise to make the overall amp more brighter if you like to use a dumblelator/kleinulator/clator.

Hi Steven,

The internal mixer is controlled by a voltage regulated pot, the signal stays analog.

Lowering your bias will benefit the bass response; less flubby.

Cranking the presence control and at the same time lowering the treble also has a
good chance to control the flubby bass.

Picking the right speaker is also important; I prefer EVM12L; no flubby bass response at all.

Hywelg; I shouldn't get to keen on 25v mark on the electrolytics,
63v specs are not that bigger and have a longer lifespan.

http://www.verelec.com/catalog/product_info.php?cPath=33_39_142&products_id=1288 for those 25uF

I used some Cornell Dubilier in test builds of my dumblelators; I like them very much.

http://www.banzaimusic.com/Electronic-Parts/

Instead of Orange drop PS, you could use Cornell Dubilier DME series.

Or http://www.audiocap.co.uk/ps-series-polyester-600v-orange-drop-49-c.asp

Thank you Mr fabulous; glad that's sorted out.

I really can't believe you're a Electronic engineer; attached is the schematic where I draw a line in the section we're talking about.
BTW this isn't a cathode biased amp. Maybe there is where you go wrong.

Hi Hywelg, well explained.