XLR frequency emulation

[23DEC2015 UPDATE : Frequency emulation components are as follows : R20, R21, R22, and C7.
*More information contained within post Ground Force One

In the El Diablo user manual, you'll find an entry that goes something like "...the balanced XLR output on your head is frequency compensated to emulate the sound coming out of your speaker cabinet."

I didn't think anything of this until I wanted to record silently with the head --the main out of any given tube head is essentially the set of cabinet jacks that follow the power tube compliment in the circuit.

With this in mind, and after research for days, I built a small "cabinet load simulator" or "power soak." This device emulates a speaker cab in that it accepts the current the speakers normally would and dissipates that current as heat with a simple resistor circuit.  (Potential post on that device, in the future.)

Many market-side speaker cabinet simulators feature a headphone jack to utilize the rig (Head and cabinet sim) as a headphone amp.  While I could have achieved this, I wanted to keep the resistor circuit simple, making potential future troubleshooting easier.  Also, that signal chain would have made me super nerves.  

Power soak in hand, the next step was signal chain.  TED has so many fucking outputs, it couldn't be difficult. 

Partial wrongs. 

What I sometimes settled on was using the Global FX Send as the output of the head; this is after trying both the balanced out and the GFXS before and after stomp and rack effects.  My reasoning for trying both and not swearing by the XLR is that THE XLR OUTPUT OF THE HEAD IS FREQUENCY COMPENSATED.

This means that, regardless of what you put in to the head, it is going to limit and color the signal in a way you cannot manipulate conveniently.  Or at all, unless you have some serious brain knows.  Or know an electrical engineer.

After my recent and successful battle with signal chain noise, I decided to endeavor toward the balanced XLR out of the head.  That, and the realization that if I'm taking the signal from just after the preamp, it isn't being processed by the power tubes. 

Taking it straight from the GFXS is the signal from everything up to the end of the preamp --gain then eq, then FX send.  

So, I says to myself, Self, I says, let's find that goddamn frequency compensation circuit and eliminate it.  

If you don't know by now, I intend to run the head in to a speaker cabinet emulator.  This way, I need the output to be as transparent as possible, i.e. not pretending it is doing any good boosting or limiting any of the signal in a static manner, after the power tubes, for 'aesthetics.'  Because if I need to eq the signal, I will.  

Don't force it up my ass.  

With all of that out of the way, here is the solution.

Capacitor and resistor compose the frequency compensation circuit, as you can see in the included pictures.  Note that I cut R20 before I took the picture because I get excited easily.

updates with tests on xlr and 1/4" unbalanced sans emulation to follow.