Citrus MKII build report

[gkoerselman]

I build Nelson's Citrus a while back but always thought that the circuit lacks treble (ends up too bassy for me). My set-up (which works great for 'pre-amps' such as the ROG Thor and many others) is to plug from this (via my EQ-20) into the Poweramp input of my Fender Hot Rod Deluxe.

I recently had a chance to compared the Citrus to the Orange Peel by OLC and though they sound similar, the treble content and control of the Orange Peel is what I would expact of the Citrus. (In reverence to previous threads, I'm using the 68n caps and the 22n for the tonestack)

After looking into this I noticed an anomaly in the tonestack. Does anyone know why Nelson has the tonestack section starting 'after' the 100k instead of after the 68n cap? I referenced this with Orange schematics I could find (http://users.telenet.be/orangefg/OFG_SCHEM/OR120schem_72.gif, http://users.telenet.be/orangefg/OFG_SCHEM/OR120schem_74.gif, http://users.telenet.be/orangefg/OFG_SCHEM/OR120schem_post74.jpg) and all have the 100k resistor 'in' the tonestack section.

I'll either try to rewire the tonestack to include the 100k, or I'll try to mod the resistor from the bass pot to ground from 22k to 180k (the Tone stack calculator shows me that this should pump up the treble to similar levels to the bass).

Also, I did some math on the FAC sections and came up with the following:

   FAC -> Total cap. -> High pass at
   ---------------------------------------------
   68n - > 68n (FAC in bypass) -> 1.3 Hz
   4.7n -> 4.4n -> 200 Hz
   4.7n -> 2.2n -> 400 Hz
   2.2n -> 1.1n -> 800 Hz
   1n -> 500p -> 1.8 kHz
   330p -> 200p -> 4.4 kHz

   Please note that for the above FAC column all caps prior are in series to this one (so for the 2.2n setting, it's 1/68 + 1/4.7 + 1/4.7 + 1/2.2).

Could anyone tell me if the above calculations are correct? I've assumed that the 180k resistor after the FAC forms the high pass filter here.

[gkoerselman]

Over 80 views and no reply...?

I rewired the tonestack today like described bellow (connected the 1.5n cap in between the 68n and 100k instead of after the 100k) and suddenly have treble control from my tonestack. I can't exactly A/B this (at the moment) but I feel it must have been an honest mistake in the schematic from Nelson.

[nelson]

Over 80 views and no reply...?

I rewired the tonestack today like described bellow (connected the 1.5n cap in between the 68n and 100k instead of after the 100k) and suddenly have treble control from my tonestack. I can't exactly A/B this (at the moment) but I feel it must have been an honest mistake in the schematic from Nelson.

You're quite right. The 1.5n cap in the tonestack should be in parallel with the 100K resistor.

I have been meaning to update this project for a while. Thanks for pointing that out.