header_graphic


THE PEAVEY MAX BASS PREAMP
(originally written Aug 2023)

My fascination, and subsequent nostalgia, for certain pieces of USA-made gear inspire me to create pages like this. After three years of missed oppurtunites, I finally acquired a Peavey MAX Bass Preamp and it lived up to the hype.

MAX History
Portions of Peavey's serial number records were corrupted/lost during a database transfer in 2008, so it's hard to lock down exact production years. Examining the Revision A schematic drawings, the USA-made Peavey MAX Bass Preamp appears to have been released in 1996. My MAX has a serial number of 11291995, which led me to roughly place it somewhere between 2000 and 2002. Unfortunately, Peavey potentiometers do not have dates hidden in their codes and there are no indicative inspector markings on my board. However, there are three Omron relays on the main board with two different date codes: "1180" and "0790" - these place their manufacture in August (8) and September (9) of 2000 (0). This leads me to believe that my MAX was likely assembled in late 2000.

Omron Lot Decoding

From forum posts, it would seem that the MAX had an MSRP of $419 in 2002, but could be picked up new for $330 if a buyer shopped around. At that time, they could be bought for about $150 on the used market. Since my search began in 2020, prices have generally ranged between $200-300, with an occasional deal of $150 still popping up. I would roughly estimate maybe ten to twenty units pass through the web each year. So when they get posted, they are bought within hours. I found mine listed on a small bass guitar store's website, two states away during August 2023 for $250 plus $25 shipping. The condition was excellent, with only a few scratches on the bottom and top panels from being moved in and out of a rack.

Comparing the schematics, I have a hunch the Peavey T-MAX head was released a year prior to the MAX, in 1995. The T-MAX supposedly shares a lot of the preamp circuitry of the MAX. However, the T-MAX notably lacks a blend knob, does not have the Punch or Bright switches for the tube channel, and both channels share the same graphic EQ. In 2023, the T-MAX was commonly going for $300+ on the used market.

The Peavey MAX Bass Preamp is highly regarded on the forums by bass players of all genres. But it does seem to garner most of that veneration from fans of Type O Negative's Peter Steele. Peter used the Peavey Bassist at least as far back as 1994 before switching to the MAX around 2000. He performed with the MAX until 2008, at which point he began using the Peavey Tour 700 head until his death a couple of years later.

Be aware that there are older and newer lines of Peavey products with the "MAX" designation that are not similar to the Peavey MAX Bass Preamp or the T-MAX. Most notably, none of them contain tubes.

The Preamp Circuit
The MAX has two channels that can operate independently, or can be combined and blended to a desired ratio. One channel is powered by a single 12AX7 - from what little I've read, this may have been a Chinese tube from the factory, but my used unit came with a Sovtek 12AX7LPS. The tube channel uses a 3-band parametric EQ, plus has a Punch switch and a Bright switch to +8db boost to the bass or treble. The second channel is solid state, and utilizes the 7-band graphic EQ along with two shelving-type controls allowing 15db of boost or cut for bass and treble. When the tube and solid state channels are combined, the Blend knob controls how much of each signal is mixed for the outputs.

The unit includes an effects loop and has several output options. There is the standard 1/4" output jack, but there is also a Crossover Balance for blending separate High and Low outputs (ex: a 410 cab and a 118 cab). There are also two DI Outputs providing a cabinet-voiced signal. A three-button footswitch will allow the user to select a channel, combine the channels, and punch the effects loop in and out. I currently route my MAX signal through the power amp section of my Peavey Tour 450.

Does the tube channel breakup? Yes-ish. Coming from a guitar background and having owned a Peavey Ultra and an Ampeg VL-502, I naively expected something more aggressive. If both gain knobs are cranked, the MAX's single tube will produce what I would describe as a pleasant rumble. To me, it is muddy - to others, it might be what they're looking for. Whatever it is, it is subtle.

Footswitch
The original footswitch is a three-button model with a seven-pin DIN plug, part number possibly 00078470. However, I have never even seen a photo of one. The T-MAX footswitch is a component match and I was able to pick up a leftover from Peavey's eBay store for $45 shipped. I had expected to do some re-wiring, but it functions exactly as it should with my MAX (in this order: channel; combine; effects on/off). The part number may be 00339550, though I have been unable to verify this. I have noted others contacting Peavey to ask if this footswitch is compatible, but they were told no ...seemingly only because the labeling for the middle button is different? So there may be other functional switches out there.

Resources
MAX Manual
MAX Schematics

I've also added T-MAX resources. The manual and the original schematics are here, along with an alternate drawing of the footswitch circuit. The original footswitch drawing can be found within the Patch Board page of the original schematics.
T-MAX Manual
T-MAX Schematics
T-MAX Footswitch

Modifications
One mod bypasses a cathode resistor which allows for increased tube gain from the single 12AX7. It will also benefit the installation of a 5751 tube, which allows the gain knob to be turned up further before breakup. This doesn't necessarily change the headroom, but can allow for a more-gradual knob sweep along with smoother cleans and smoother overdrive tones. This mod with the original 12AX7 will allow it to breakup sooner and nastier. The mod is accomplished by adding a 22MFD @ 25WV capacitor in parallel with part R224 (which is a 1.5K resistor). The physical location of R224 is on the tube's breakout board.

The second mod will remove the cabinet voicing from the DI Output. This voicing apparently attenuates the highs. With the top panel removed from the unit, locate the row of seven small parts soldered directly behind the three main output jacks. The two adjacent bright-yellow "beads" are small capacitors. These need to be removed, or at least one leg unsoldered and lifted clear of the circuit board. These are parts C517 and C521 on the main board.

I have not done either of these mods.

Replacement Knobs
Not sure why, but exact replacements for the MAX's "tear drop accent" knobs seem impossible to find. The 1U (single rack space) preamps that came out in the 1990s, with the "Miami Vice" aesthetic, all share this style of knob. These include the Bassist, the T.B. Raxx, the T.G. Raxx, the Rock Master, and the Alpha. The MAX is unique in that it uses two different colors: the solid state portion uses four knobs with a light grey accent, while the rest of the knobs and the EQ sliders all have bright white accents. Someone replaced a white one on mine with a blue one, though I have never seen a blue one anywhere. The T-MAX does not use the same knobs and the earlier "airport tram" aesthetic Peavey electronics used knobs with a grey accent that was squared-off. The sliders do seem fairly common, plus there should be some aftermarket sets that will work.

 

(end)

 


 

CrankyGypsy (established 2001)