Aric Audio Systems Unlimited Preamp

rocray, thanks for the feedback. I think I'll try this combo as well just to see what difference it makes in my system. My Unlimited is paired with an older version of Aric's SE KT88 amplifier and upstream I have a LamizatOr Amber tube DAC. Lots of tubes to play with...all played through a pair of Omega Super Alnico Monitors. Glad to hear you're enjoying your "tweak".

I think you will be pleasantly surprised. I feel the tube change brought my system up a notch. Right now I'm running the Unlimited with a First Watt F5,Graham Chartwell LS3/5's,Bluesound Node 2,through a Topping D50. The Topping is my first foray into external DAC's. 

Just wanted to give a quick update with my experience switching to the 5U4GB/OC3/OD3 tube arrangement for those who might be interested. The first obvious change was the regulator tubes lit up much more quickly when compared to the stock 5AR4/OD3/OD3 set up. Not sure if its a "soft start" change or not but it used to take roughly 10 seconds or so for the regulator tubes to glow but now they light right up upon turn on. Didn't notice a change in the gain level but I agree with Aric's characterization that the soundstage is now a bit more "fleshed out" and the overall sound is more pleasant. A very well worth experiment, cheap and simple. Thanks rocray and Aric for all your input and guidance. This little preamp keeps getting better and better...

As far as the change in gain,I’m going to attribute that to human error. I had to pull my pre out of the rack to switch tubes. I could have very easily twisted the gain control unplugging connect wires. That seems more likely the more I think about it.

 kalali,great to hear you have had similar results! 

Hey guys, It's very cool to hear on the tube tweak upgrade! I will be letting others know about it as another option to tailor the musical presentation towards a slightly less "upfront" character (perhaps to help mellow an overly sibilant or bright amplifier?). @rocray - Thanks for posting your impressions! @kalali - Thank you as well, and on the quicker igniting of the regulators- this is due to the 5U4GB being a "directly heated" rectifier- meaning that it conducts as soon as it is powered up. Alternatively, the 5AR4 is an "indirectly heated" rectifier and it takes 10-11 seconds before its heater comes up to temp, which then allows the cathode to conduct. It's often used as a "turn-on delay" or soft-start, but is not needed in the Unlimited. Best regards, Aric