DYNACO Pre-Amp PAT-4...with an added Volume knob


I just purchased this pre-amp
It sounds good but someone added a volume knob in substitute of 
the input headphone jack.
I looked inside of unit , there is a volume pot installed instead of input jack.
Has anyone ever seen this modification before?...if so , what is it used for?
Thank you
rocky1313
So you have 2 volume pots, and NO headphone jack, or is there still a headphone jack there, inside or moved?

Second:  what is the volume pot hooked to? I'm thinking someone used it for a trim pot, on a line source input, like a Reel to Reel. Is it a pot or an analog, off/on switch of old.. 4-6" long with disk full of resistors/caps and a common shaft?

Does the unit work?

Regards
Not heard of that. You might hook it up and see what happens- does it control the main outputs? Does it control the recording outputs? That will give you a good idea if you need to do anything about it.
Post removed 
WOW that is a of of information. One heck of an upgrade too.

I have a PAT II all valve unit.. I bought the kits over 2 years ago.
(my interest in this thread)

Distortion reduced from .02 to .002 10X reduction.. lot of work!

Regards
Here is an UPDATE on Dynaco PAT-4 pre amp......
As you know from my previous post, I was asking about a volume control knob that someone installed in my pre-amp's input jack.
I now have found out  the knob was used to regulate the volume on Output 1 .
I hooked the unit to Output 1 . 
( there is an Output 1 and an Output 2 )
Output 1 regulates the volume.
Does anyone  know why this second volume control was added onto Input jack?
The music does sound better on Output 1.
Should I leave it hooked up that way ?
thank you