Aric Audio Systems Unlimited Preamp

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

Aric, thanks for the explanation. Makes sense. I did a bit of a binge listening last night mostly familiar tracks and am now appreciating the change even more. The Omega single drivers can get a bit "too upfront" in the midrange particularly at louder volumes. With these (tube) changes the overall sound appears to be more even and balanced. The net impact is a more realistic soundstage without any negative affect on the texture or imaging, etc. Not sure how else to describe the affect. Very interesting. 

Ok,I am truely enjoying this new tube set up. Next question,what 12a_7 are you guys running,and what are your impressions?
   

In my experience, the "flavor" that different signal tubes add/subtract to/from the music and whether or not you ultimately prefer the sound, will depend on the gear upstream and downstream from the Unlimited, maybe even the cables. I have tried JJ, Tung Sol Gold Pin, Mullard new stock, vintage Mullard, and vintage Telefunken signal tubes.  When I had my SS DAC and Vincent hybrid amp driving Vandersteen 2Ci speakers, I thought the two vintage brands sounded slightly more musical. But now with a tube DAC and an SE tube amp and single driver speakers, same cables and same room, I have settled on the new stock Mullards and sometimes I swap in the new stock Tung Sol Gold Pins. I feel these tubes are a bit more neutral and better complement the rest of my system. The vintage tubes seem to add a tad too much emphasis on the midrange which I don't really need given the character of the speakers and the rest of the tubes in the signal chain. I am not talking night and day here and the experience could vary quite a bit by the type of music and the recording. The best bet is to just try different pairs and see which ones sound better to your ears in your system/room. Vintage tubes can get very pricey but new stock tubes are fairly reasonably priced and I honestly do not think the sound difference justifies the cost difference, at least in my experience. Hope this helped.