The Pittbull Ultra-Lead is a powerful, yet extremely versatile amplifier well suited for players of any style who are unafraid to own center stage. Uncompromising personality has made this amplifier the top choice of world class players from all genres of music. The Ultra-Lead's KT88 power section provides stunning clarity and definition whether playing clean or at maximum gain. The low and medium gain sounds are balanced and spacious, while the clean tones can be pristine, chunky, crisp or edgy. The wide range of sounds is limited only by your imagination.
"The VHT Pittbulls... deliver all the features you expect from a modern rock amp. Super high gain, an intelligent effects loop, bullet-proof construction and super clean tones --- something the others seem happy to ignore." - Guitar Player Magazine
The PITTBULL ULTRA-LEAD, paired with the FatBottom Straight 412 cabinet, delivers ground shaking thump and blow-your-hair-back low end projection. This is a seriously expressive combination, specifically designed for players who seek unbridled dedication to guitar mastery.
Pittbull Ultra Lead w/ EQ
Front panel: Input HI/LO, Edge, Lead Gain, Lead Switch, Hi Gain Switch, Lead Volume, Rhythm Boost, Rhythm Gain, Rhythm Switch, Hi Gain Switch, Rhythm Volume, Edge, Treble, Shift, Middle, Bass, Clean Volume, Boost, Treble, Bright, Middle, Shift, Bass, EQ, Master Volume, Standby, Power.
Rear panel: Ground Switch, AC Input, Mains Fuse, DC Fuse, Power Amp Mute Switch, Impedance Selector, Dual Parallel Speaker Output Jacks, Line Out Level, Line out, Footswitch Jack, EQ Switch, Loop Switch, Loop Return Jack, Series Parallel Switch, Loop Level Switch, Loop Send Jack, Loop Level/Mix, Presence, Depth.
Features : Three channels: LEAD, RHYTHM & CLEAN. Gain Stacking™, Six-Band Graphic EQ, Series/Parallel Effects Loop, Power Amp Mute, Half Power Mode, Variable Line Out, Presence, Depth. Power output: 120 Watts RMS.
Impedance: 4, 8 or 16 ohms. Two parallel output jacks.
I hate to see you worrying about these superfine differences in plate current readings considering that you will typically see a significant line voltage variation in the half hour to hour you spend ultra-tweaking the bias, not to mention the transformer voltage variations that occur as the transformer heats up and cools down.
Regarding plate voltage, if you are correctly measuring this at the plate of each tube, you will have the same voltage for all four, give or take a very small difference between the right and left pair, say 2 volts tops. There's no way you're legitimately getting a 30 volt difference in plate voltage readings between 2 of four tubes no matter what position they are in unless you have a seriously off spec tube in one or the other pair. Even then, that will pull down the whole supply, not just one side of the primary voltage drop.
Keep in mind the best you're going to accomplish with these kinds of biasing tools is an approximation, not really too far removed from leaving the adjustment at the factory setting unless you are using a radically different tube. Any better accuracy requires a scope, signal generator, variac and a very accurate dummy load. Without that, trying to get less than an 8 to 10mA difference between pairs is unrealistic and largely unnecessary.
My recommendation: Put the tubes in, let the amp idle for an hour, set the bias for 65% PD +/- 5% AVERAGED OVER THE NUMBER OF POWER TUBES, plug in your guitar and go peel some paint of the walls.
P.S., Example: With the UL at idle plate voltage of 450V, a combined idle current of 232mA for all 4 tubes yields 65% PD. That's 58mA/tube AVERAGE. In other words if you have a pair in which one tube is drawing 60 and the other is drawing 56, you're within +/- 5%. No sweat. Therefore Ralphs 53 to 56.6 range averages out to 54.7 - essensitally 55mA, or 62% PD. Another 3mA/tube AVERAGE gives you 65%. Keep in mind this is just an example. Your plate voltage reading may be different. That's OK. Adjust the other variables accordingly.
Q: Can you recommend A brand of KT88's and do you sell tubes direct or recommend a supplier?
Thank you for contacting FRYETTE AMPLIFICATION support. We use and recommend Sovtek KT88s for this amplifier.
We can supply you with replacement tubes directly or you can order them online from suppliers such as tubestore.com and tubedepot.com.
Please let us know if we can be of further assistance.