Recent upgrade to Cronus Magnum

Hi, my 2 pennies worth . I have a Rogue pre . My close friend that lives nearby is a former Rogue Dealer . He has a Chronus Magnum II in his office . A Rogue Hera pre with M180’s in his main system. So I’m familiar with their sound. I am thinking that all your tubes are well used ? A new quad of power tubes is a must, as they will sound brittle and edgy when tired . New production Gold Lion KT 88’s or Tung Sol KT 120’s if the early Chronus  will support them . The Tung Sols make substantial bass and still have good mids and highs . I have tried EVERY driver tube mentioned in this thread . And I absolutely would choose NOS Telefunkens and am surprised they weren’t mentioned . On a budget nos Tesla and Tungsram sound similar. I run Telefunken G-73R’s in my pre. Rogue generally suggest trying a nos Mullard as they smooth things out . But it’s like putting a blanket over your speakers , or pushing the Dolby button on your tape player . The Rogue amps are all SS power supply ( no rectifier tube ) so you can’t drop the voltage and mellow the sound . But they do recommend under certain conditions lowering the bias voltage . Quality driver tubes make a huge difference. So now your at an expense crossroad . You could consider having the amp serviced and/or upgraded to current specs . But first I would get a quad of new power tubes. New nos driver tubes . Where I’m totally lost is how it pairs with your speakers , as I haven’t had those . And that’s a big deal . Now here’s a story . My friends M180’s were over powering his Speakers and he was advised by Rogue to lower the bias first . He wasn’t satisfied and was directed to replace the power tubes with new Gold Lion KT 77’s and play with the bias setting . I HIGHLY SUGGEST , that you read the driver tube sound descriptions on the Brent Jesse website. After spending $2K on various nos driver tubes , I can attest it’s SPOT ON ! I haven’t shopped there however, but hear good stuff . I’ve also been recommended to Andy at Vintage Tube Service by wholesale and manufacturers. I purchase new production power tubes from Tube Depot when they run a 20% off sale and ask for matching and 24 hour burn in . I have a Dennis Had amp ( Cary founder ) and Zu speakers . My system runs bright . I have Amperex , Seimens CCa , Tesla , Mullard ,RCA , Phillips amongst my stash and have found the Telefunkens to deliver a full sound without being overly bright . I run a Schiit Yiggy DAC and a modded Thorens TD 160 with a Grado cartridge. I’ve had to avoid any silver in my wires as it gets too bright also . I hope my rambling has provided some help . Happy Listening , Mike B. 

The cronus is known for being non tubey . Its recommended to not adjust bias often.

I had been traveling quite a bit in February so didn't get a chance to try out different tubes. Finally got around to ordering new tubes from Brent Jesse as per @avanti1960 's suggestions. Was advised to get the Amperex (1960) for the center/preamp as suggested on this forum. But Brent suggested that I go with Amperex for the AX7s as well. He also advised me to let them burn in for at least 48 hours before doing any critical listening.

So what's the verdict after changing 3 tubes? All I can say is, wow! The sonic improvements are not subtle by any means. I'm getting much more detail than before without any harshness, all in a very polished and smooth package. Better tonality, more separation and air between instruments. Much wider and deeper soundstage. Vocals sound more natural than before.

But the biggest improvement by far is the quality of bass. I never thought I could get the P3esr's to produce such satisfying base. It doesn't go much deep but whatever I'm getting is tight and very palpable. I was thinking of adding a subwoofer, but honestly at this point I'm not sure I need it. Everything sounds so balanced, don't want to ruin it.

Another improvement I noticed is that I'm getting more details and bass at low-to-moderate volume. Before, I had to crank it up to 11'o clock to get the details and bass. After the switch, everything sounds pretty good even at 9'o clock position on the dial.

Thanks everyone for the amazing advise. I'm pretty happy with the music this system is producing. I'll probably swap the remaining AU7s in a few months, and maybe get a copper-based speaker wire to see if I can eke out even more improvements.

How much did the Amperex (1960) Tubes cost?