[stereodiver]

A friend made me an DIY tube preamplifier to substitute a ROGUE MAGNUM 66 Tube preamplifier. I obviously like my new one but then I also liked the old one. Wh

at kind of test can I submit them to in order to determine which one provides better transmission of the signal.

[FullRangeMan]

Welcome 
Congratulations for the new preamp.
The best transmission signal per se is not paramount important as a music player, what are really important is if it have a good sound to your personal taste, my own personal taste are:
1- Wide and deep soundstage
2- Silent background
3- Detailed and trasparent
5- Flat response, no need for tone controls or balance
6- All tube compliment, including tube retifiers
7- Double as headphone amp (XLR-4)

I like these parameters used by an reviewer site valid for most equips:
Tonality
Sub-bass (10Hz - 60Hz)
Mid-bass (80Hz - 200Hz)
Midrange (200Hz - 3,000Hz)
High Frequencies (3,000Hz On Up)
Attack
Decay
Inner Resolution
Soundscape Width Front
Soundscape Width Rear    
Soundscape Depth Behind Speakers    
Soundscape Extension Into Room
Imaging
Fit And Finish
Self Noise    
Value For The Money

[Phil A]

Welcome!  Always best to listen in your own system.

[dwmaggie]

I saw a post either here or A'gon for a test and burn in CD from Reference Recordings out of San Franciso.  XLO Reference Recordings, available on ebay for 39 and 54 dollars or direct like I did from RR for 19.95-the difference the ebay gold deposited CD?  FRM they cover most of your bodacious post.  What I like is the way they explain/demonstrate out of phase, then play an out of phase track.  The disc also explains what to listen for and then plays superb recording to demonstrate.  Bella Fleck and the Flecktones 'Flight of the Cosmic Hippo'.  Last CD Double Bass by Niels-Henning Orsted Pederson and Sam Jones.  Double Bass is also what they each play.  I use these when rolling components, whether an amp, pre, or speaker re-configuration.

[glynnw]

I am a simple person.  Listen to music you like.  Choose.

[JLM]

Wonder why someone would try to replace a given vintage class A single-ended triode tube preamp.  Do you not trust your friend's work?

Objectively the DIY preamp should be taken to a test bench to ensure it's performing well, but it's doubtful that will tell you much unless the shop just happens to have a refurbished Rogue 66 on hand to compare it against.  DIY design and build quality runs the gamut, but most can be expected to be quite poor.  The Rogue 66 was a quality value based product that used two 12AU7 tubes, but due to age some capacitors will be due for replacement and controls/pots will need a cleaning. 

Current asking price for private sale of a Rogue 66 in good working condition is about $600 USD, doubt if your DIY preamp could fetch that much.