Which produce a bigger change? - both, but how much of a change depends on the specific tube. I don't have experience with the Modwright Oppo but I do with my Lampi Atlantic TRP. The best rectifier I have used so far is the Psvane ACME 274b. It added substantial weight and saturation to the sound. Signal tubes in my DAC tend to impact the soundstage (size and holographic quality) the most. The Lampi uses power tubes instead of small signal tubes so my DAC tube experience won't be relevant but I can say my favorite 6922 for my VAC linestage is 1959-1961 NOS Amperex Bugle Boy. Unfortunately this is a trial-and-error process but you can get some traction and eliminate some horrible fits by asking for this sort input. Enjoy!.
Which one produces a bigger change... changing a rectifier tube or tubes on my DAC?
Trying to see which tube upgrade to do first on my Modwright Oppo UDP205. Tubes on the DAC or rectifier tube? At the moment Im using Sylvania on DAC and a 5R4-GY on rectifier from Andy at Vintage Tube. Any recommendations would be great. Thanks.