A friend of a friend had a powerball and complained about the sound. It lacked punch, clarity, definition, etc. He was really, really disapointed by the sound of this amp. This sunday, by surprise, he came by with his amp when we were rehearsing. It was his lucky day, cause I happen to have a collection of some nice NOS tubes with me. We connected the amp to the cab (Line6 4x12), turned some knobs and were able to find a nice sound. I noticed the amp had on channel 3 and 4 A LOT of gain. The most decent sounds were made with the gain on 2! Also the high frequencies were very present and we were unable to tame them in a good matter. After 15 minutes we had the "best" sound possible, but it indeed lacked everything in the region of clarity and definition. Chords were muddy, everything blended with each others, (higher) notes where hard to recognize and it sounded a bit lifeless. When you hit a chord it didn't sound punchy, a bit hold back. After taking a quick look at the preamp tubes I noticed it had 1 Sovtek (12AX7WB btw) in the first position and 3 Chinese preamp tubes in the remaining sockets. I took them out and placed the following NOS tubes from left to right: Philips ECC82 - low gain valve, Mullard production Philips ECC83 - Mullard production Philips ECC83 - Mullard production RFT Muehlhausen ECC81 - low gain superb quality. We powered the amp back up and gave the tubes some time to warm up and turned the amp on (channel 3). The gain was still at 2 and the amp produced a nice clean sound (lol). We turned the gain up 7 (and most other dials as well) and the amp breathed like never before, yet with far less noise. This was unheard. It had everything you would expect from a great amp. The sound was extremely punchy, almost JCM800 like, notes were clean and clear, top-end was very musical, mids and lows were clearly defined. It totally changed the amp around in sound quality! From an ok sounding amp it became a killer amp. This is how a distortion sound should be: articulate, punchy, clear and defined. It sounded almost like a clean channel, only with a dirtier sound, if you understand what I'm saying. Simply amazing!! So what did the trick? Well the original chinese tubes are just awful (fizzy and blurry) and the Sovtek WB's aren't that great either. The NOS tubes produce a far better sound. 2nd which might be a lot more important: gain. The amp has a absurd amount of gain, cascading overdriven sounds won't give you definition. It just compresses the hell out of your signal and blurs the whole sound. The easiest way to solve this is by using one or two low gain valves. This brings back the total level and really lets to tubes distort in a proper matter. I highly recommend this to anyone who has a modern high-gain-monster amp and who wants more clarity and punch. Current production JJ ECC81 and ECC82 are good tubes to start out with. Kind regards, Maarten van Helden -------------------------------------- Your amp already has those Ruby's in it. They're just relabeled by ENGL. The stock bias setting for the Powerball is around 26 to 28 mA. The plate voltage is 420. Basically, you want the power tubes making about 48 watts at idle. --------------------------------------- im selling my beloved engl powerball v1 in awesome condition, it's recently been retubed and biased to run a quad of tung sol 5881 in the power section(these things make this amp sound sooo much better), and in the preamp it's running a few jj ecc83s's(for a good raw aggressive sound) and a nos jan 5751(really opens up this amp). i cant tell you how amazing this head(or any engl for that matter) is you'll just have to play it for yourself. im selling only to help fund my upgrade to the almighty ENGL SE. asking $1450 + shipping and paypal fees. email me with any q's and or for pics. ---------------------- In mine I have: Tung Sol 12ax7 in V1 (adds clarity) JAN GE 5751 in V2 (lowers the gain a little, warms the amp up, makes it so it accepts boost pedals better) 9th gen Chinese 12ax 7 in V3 (best space filler tube IMO) Sovtek 12ax7LPS in V4 (The best PI tube I've tried and what Doug at dougstubes.com recommends for nearly any amp) I have SED =C= 6L6's in the power amp and I gave it a proper bias. Sounds much better than the stock tubes! Keep in mind I had about 20 preamp tubes laying around to try and these were the best I found for this amp!