Orange TH30: weird component choices ?

[maestun]

Hi,
Since there were no schematics available, I've traced most of my Orange TH30 amp (preamp, loop driver, PI, power stage).
For reminder, it's a 2-channel preamp with a quad-EL84 power stage.

I can post my crappy drawings here if anyone's interested, however this amp looks like an EL84-driven Rockerverb 50 MK1 (its schematics can be found online):
- Clean channel: almost identical to RV50
- Dirty Channel: identical to RV50 (except one cathode bias resistor)
- Dirty Shape Control: identical to Dark Terror
- Loop Driver: identical to OR15
- Phase Inverter: identical to OR15

However, I noticed 2 weird things:
- The bass pot (in the Clean Channel tone stack) is a linear 250k pot, whereas it's a logarithmic pot in all the Orange tone stacks I've seen yet
>>> could that be an error made at the plant ? I already noticed that the bass control was not very "responsive"...

- For each EL84 valve, there's a 2k2 input resistor coming from the Phase Inverter into the valve grid (pin 2)... except for one valve, where this input resistor is only 1k !
>>> here, I'm kind of lost, why change this on only one of the 4 valves ? Crappy biasing for bad factory valves ?

Any advice would be very appreciated, thanks

[J0K3RX]

I would definitly swap out the bass pot with the expected audio pot! Can't really see any reason for that other than human error..? Not really sure about the 1k grid stopper but, if the bass pot was a blooper then odds are you may find more bloopers in the same amp... Assembly worker probably grabbed the wrong resistor/s and put them in the wrong places.. If you have compared to the other similar Orange schematics and none of them have these odd vales then you probably have one that slipped through QA and out the door to consumer ville..

[maestun]

Yep, I swapped back to expected values, the bass response on the clean channel is much better now.
Also modded R21 (1k5 to 2k2) for the dirty preamp to match the Rockerverb's