Aguilar DB359 Tube Rolling My goal is for my amps to be capable of producing clear/tight lows, articulate mids, soft/smooth high mids, and slightly glassy highs with relatively neutral EQ settings. Speakers are Electro Voice TL405 cabinets that are ported around 27 hz. Bass is a Series 1 Yamaha TRB6P. The following is IMHO based upon my experiences with this particular amp and the tubes I have on hand. I bought this amp off Ebay a few years ago. It was pretty much mint, showing almost no signs of use. It had an Aguilar labeled 12AX7 in V1, a JJ 5751 in V2, and a JJ ECC82 in V3. The outputs were Aguilar labeled Svetlana 6550Cs (the good ones). Unfortunately the amp didn’t sound great; instead, it excelled at getting a good scooped bedroom tone with lots of deep bass and an overly bright top end. Basically, it had the type of tone that would be next to unusable live because it would tend to disappear into the mix. The sound seemed more scooped, solid state, and clean than warm and tubey. The amp was putting out a reasonable amount of volume but it totally lacked punch and the low end was a bit uneven and wooly. Additionally, the amp seemed a bit noisy and increasing the gain to a level that produced any amount of drive was just nasty. I rolled some old (used) tubes into the DB359. I tried all possible combinations of 12AX7 and 5751 in V1 and V2 and found I preferred 12AX7s in both positions. The 12AX7s seemed to have a touch more harmonic character/color and better feel. None of the tubes made much of a difference to the basic tone of the amp. The biggest difference seemed to be slight changes in gain. I eventually settled on a Mesa 12AX7, a Marshall 12AX7, and a JJ ECC802 that seemed to tighten the sound a bit, improve the tonal balance ever so slightly, and slightly reduce the amp’s susceptibility to noise. The improvement was marginal at best and I was pretty frustrated. The Aguilar 12AX7 that came in V1, was actually a really good sounding tube with lots of gain, but it had a lot of highs and lows, so it didn’t seem to work very well in the DB359. I rolled the tube into one of my other amps and was very pleased with the results. Recently I bought a bunch of new preamp tubes. I rolled six or seven 12AX7 tube types through V1 and three or four 12AX7 tube types through V2. I limited the tube rolling in V2 mostly to tubes that I know can tolerate elevated cathode voltage. I don’t know the voltages applied in the circuit, but didn’t want to risk putting a tube with a low cathode to heater rating in this position if I didn’t have to. Even with new 12AX7s, individual tube swaps seemed to produce barely perceptible changes to the amp’s sonic signature. The tubes that seemed to produce the best and most noticeable changes were the Mullard ECC83 in V1 and a JJ ECC803S in V2. Together, these tubes seemed to produce a bit of synergy. I wasn’t sure the Mullard’s big bottom was going to work in the DB359. Fortunately its full low end reaches well into the mid bass providing a nice counter to the DB359’s scoop in this region. Additionally, the Mullard’s soft high mids effectively evened out the DB359’s treble response. So far the Mullard ECC83 has proven to be a great V1 choice in every bass amp I have tried it in. I really like the high end contour and what it does to thicken and tighten up the low end verges on amazing. The JJ ECC803S seems quite good whenever you need a relatively strong tube with an even response and a tight and muscular feel. With few exceptions I have selected this tube for all positions that could have elevated cathode voltage. The amp is no longer a scooped sounding bedroom queen with excessive highs and deep wooly lows. The lows are full, round and much tighter, and the amp now actually has some punch and definition. The highs are more even and natural, and the hum and hiss level is lower. The tone controls work a bit better, so a good tonal balance is now achieved with the settings closer to 12 o’clock. The amp definitely sounds articulate and powerful, and you can get a touch of musical drive as long as you don’t go crazy with the gain. Sounds like a really good tube amp now.