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XP Series

Introduction

A Rockman rig based on a series of Rockmodules is a very complex set-up: you rapidly have several tenth of sliders, switches and footswitches to operate before getting the sound you want.

The microprocessors that were available in the eighties were not powerful enough to perform digital signal processing, but they could easily handle the control parameters of analog devices.

The Rockman XP Series was based on this concept: keep the analog circuits of the classical Rockman units, and make them programmable.

Objective and history

The XPR was not the first product based on this principle: there were digital controlled analog preamps and effects before.

But the XPR was certainly the first all-in-one unit: as a matter of fact, when you own an XPR, you don't need anything else to deliver the sounds you want, and you can store 100 different programmable sounds in it! That was quite innovative in 1989.

The first item of the XP Series was the XPR, the first 19' rack unit made by SR&D. It was replaced in 1991 by an updated low-noise version, the XPRa:

The basis of the XPR is just... the X100 headphone amp! In other terms, the XPR is a sort of big, programmable X100, with of course several additions that make it totally flexible:

There is a first 3-bands EQ at the input level, that allows shaping the distortion at will (refer to Rockman - The concept for the pre-distortion EQ principle).
The preamp and distortion stage have a cool feature that allows mixing a clean sound and a distortion sound
A 5-bands post-EQ is placed right after the distortion stage: the combination of pre and post-EQ gives the XPR a total flexibility in terms of sound
The stereo chorus has a programmable sweep speed (but no Long-Chorus mode)
The reverb section can be used as a short stereo delay

All the parameters of these modules (compressor, pre-EQ, preamp, post-EQ, chorus and echo/reverb) are entirely programmable, and can be stored in 100 presets.

The temptation was of course to build a guitar amp that would have an XPR as a preamp section. The guitar amp would of course be stereo, and stereo called of course for separable cabs for a wider image. That was the XP100 Programmable Stereo Amp: the XPR with a 2x50W stereo amp, housed in a double enclosure with compact 6 inches Pyle speakers:

The weakness of the XP100 is clearly its small speakers: the amp in itself is excellent and loud, but these small car-audio speakers cannot handle this power the way it deserves. The other amp based on the XPR was the XP212: a 2x50W stereo combo with two 12 inches guitar speakers. This version is extremely rare: probably a dozen of XP212 only were made.

The ad for the XP212 shows discretely another XP Series product, without even naming it! This is the more-than-rare Rockman Superhead: it is in fact the electronics of an XP100, presented in a head format. I have myself transformed an XP100 into a Superhead Replica, certainly because I will never cross a real one: Boston owns one of them, and a second Superhead was sold on eBay in January 2006: that's all we know about it! Having no speaker, the Superhead must of course be connected to a pair of full-range cabs: it is loud, it sounds good, and it is in my opinion the best configuration for a XPR based Rockman amp.

Usage, samples and limitations

The XPR is a contradictory product. It is programmable, and that makes it a fantastic unit, of course. The preamp and EQ's section is really great, and sounds really awesome.

The chorus and reverb sections are of course weaker: they don't have the complex circuits of the Rockmodules, and are fairly limited and noisy. For example, the reverb section is based on the same MN3011 chip as in the headphone amps, and was pushed to its limits in order to obtain a 220ms (340 in the XPRa) delay. It is noisy, and far from the plain and clean 500ms of the Stereo Echo.

All and all a good unit, the XPR delivers a wide panel of sound and atmosphere in a very compact and handy format. Had it been a preamp only, with the Autoclean and a built-in Smart Gate, it would have been almost perfect. But like every all-in-one device, it has some minor defaults.

The younger units were delivered with a series of 24 factory presets. I have chained them into a long sample that will give you a good idea of what the XPR can do.

Collectibility and conclusion

The XP products are quite rare: less than 3000 were built, most of them being basic XPR's or XP100's. The XPRa, XP100a, XP212 and Superhead are so rare that you must not plan to buy one: just catch it if you can when you see one!

The XP products are very contradictory units, with fantastic qualities but also some weaknesses: some people will find them great, while others will be disappointed and prefer the classic Rockmodules.