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L5 Preamp

Based On
Lab Series® L5
Effect Type
Preamp
Build Difficulty
Advanced
Project Summary
A pedal adaptation of the two-channel preamp of the Lab Series® L5 amplifier from the late 1970s, often considered to be the best solid-state amp ever designed.
L5 Preamp printed circuit board

Printed Circuit Board

What's included?
PCB only. Build instructions and parts list can be viewed or downloaded from this page.

$22.00

In stock

Complete Kit

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Kits are developed based on interest, so if you’d like to see one for this project, let us know.
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Lab Series® is a registered trademark of Gibson Brands. Use of the Lab Series® name is not endorsed by Gibson and is used for comparative purposes only.

Project overview

The L5 Preamp is a pedal conversion of the preamp of the Lab Series® L5 guitar amplifier, a Moog-designed solid-state amplifier from the late 1970s that is widely considered the best and most tube-like solid-state amplifier ever made. It has two channels which are both merged into a shared distortion/master volume circuit as well as a compressor/limiter.

The original amps had the preamp integrated with the power amp. By splitting out the preamp, we can use this either as a normal pedal in a chain (e.g. tuner → overdrive → L5 Preamp → modulation / delay → amp input) or as a true preamp by plugging its output straight into a power amp (either a dedicated power amp or just the “return” jack of an amp with an effects loop). The main difference will be the volume setting. It’s capable of enormous signal levels, far more than any stompbox—so if you’re using it like a pedal, it’s normal to keep the master volume down really low.

The updated L5 Preamp is a full redesign of our original project from 2016. The biggest difference is that this one is much easier to build, with greatly simplified wiring and a cleaner layout. It also now runs on standard 9V DC power instead of AC like our earlier one.

There are also a few circuit tweaks. The first is a new feature: making the Multifilter section switchable so that it can be applied to either channel. There’s still only one of them, but now people who prefer channel 1 can also experience the unique sounds of the multifilter.

The second tweak was to reconfigure the input op-amp stages as non-inverting, which cuts down on noise and is typically viewed as better design practice. We’ve done simulations and A/B tests to ensure the tone is unchanged.

The third change is to remove the hi/lo switches for each channel, which corresponded to the hi/lo inputs in the original amp, and hardwired it to “Lo” mode (i.e. the one intended for low-level signals, providing more gain boost at the input). The only function of the “Hi” input was to attenuate the input, but the attenuated input sounds dull and lifeless in nearly any normal use case. You’ll generally get better results just turning down the channel volume if the “Lo” input is too hot with your instrument.

We have also created an Interactive BOM tool for this project to help with the build process. Components are grouped by value, and you can click any component to see which other parts have the same value and where they’re located. (Chrome-based browsers only)

Circuit history

By all indications, the Lab Series® is one of the most meticulously designed consumer-grade guitar amplifiers ever made.

Development

moog_lab_series-number_one

“Number One”, the original prototype for the Lab Series amps.

Design began in 1976 in a barn behind Bob Moog’s house.[1] The original prototype unit, serial number one, is in the Moog Archives. The only photo we’ve seen is the one to the right, and it indicates that this first Moog design was missing the midrange frequency control and the compressor circuit. Otherwise, it appears to be at least functionally equal to the production L5. (This would have been developed before the Lab Series brand was created, so the cosmetics are very different and it carries the Moog logo on the grille cloth.) It’s unknown whether Bob Moog himself had anything to do with the design, but it’s probable, given that it was developed on his property, the multifilter is his own patent, and he did not leave the company until 1977.[2]

The initial Lab Series consisted of the L5, L7, L9 and L11 guitar amps, first released in 1977. The L2, L3 and L4 followed soon after. The engineers continued to refine the concepts and expand on certain ideas, and the L6 and K5 were released in 1979. However, by this time the brand was struggling, and Norlin cut many of the engineers in October of 1979 and stopped further research & development. The amplifiers continued to be manufactured through 1980 (the date of the last known speaker codes), and were likely still being sold into 1981, but the death sentence had already been handed down by that time.

Marketing

The Lab Series was developed during an era that was something of a dark period for music gear. The once-iconic Fender and Gibson had both been sold to companies who cut costs and cut corners to maximize profitability, and with a few notable exceptions, products that were released by both brands during these “conglomerate” years of the 1970s and early 1980s are not regarded favorably by today’s gear enthusiasts.

Nonetheless, the Lab Series stands out as one of these notable exceptions. They were meticulously designed, highly innovative, and built like a tank. No corners were cut. And Norlin, the parent company of Moog and Gibson who also owned Sennheiser, Maestro and the Lowrey Organ Company, supported them with a substantial marketing campaign. They took out single-page or multi-page ads in all the major guitar-related publications.

These advertisements are remarkably different than the type of advertisements you might see today. They focus on the build quality, the features, the sound, and the rigorous testing procedures. There is a notable lack of sensational or hyperbolic language, instead encouraging the reader to try one at their local music store and let the sound quality speak for itself. They also featured endorsements from BB King, Ronnie Montrose, and Allan Holdsworth, to name a few.

However, their sales figures did not meet the expectations of the parent company and Norlin discontinued their production in 1981 after four years on the market. By 1986, Norlin had sold off all of its brands and the Lab Series was never heard from again.

This failure can mostly be attributed to “wrong place, wrong time.” While the Lab Series marketing message of quality and reliability would have appealed to today’s musician, and perhaps those of the previous decade, it fell on deaf ears in the 1970s. The Lab Series line was also not particularly cheap and fell outside the budget of most working musicians during that period.

Despite their limited window of availability, they are not particularly rare today, the L5 especially. The L5 can still be found for very reasonable prices in the United States, approximately $350 to $500 depending on condition, on eBay or Craigslist.

Aside: The circuit boards contain the “Moog” logo etched into the copper, but the amplifier itself only said “Norlin Music Inc, Lincolnwood, Illinois” on the rear panel in very small text. While this line of amps is sometimes called the “Gibson Lab Series” or “Norlin Lab Series”, it’s more properly referred to as just the Lab Series, in the same way that the Maestro pedals are not called the “Norlin Maestro” or “Moog Maestro” though they were also designed by Moog and distributed by Norlin.

The Series

The Lab Series consisted of nine amplifiers:

  • L2 (Model 315): Bass head, 100W. Identical to the second channel of the L4. Similar to the second channel of the L5/7/9/11, but with changes to the frequency of the filters to better voice it for bass guitar.
  • L3 (Model 316): Guitar combo amp, 50W, 1×10. Completely different circuit from all other guitar amps in the series, but similar to the L6 and K5. Marketed as a practice or student amp.
  • L4 (Model 317): Bass head, 200W. Similar to the L5/7/9/11. Originally came with a cabinet.
  • L5 (Model 308): Guitar combo amp, 100W, 2×12. This is the flagship of the series with two channels, reverb, multifilter, and compressor/limiter.
  • L6 (Model 331): Bass combo amp, 100W, 1×15. Very rare, issued later than the others (ca. 1979) along with the K5 keyboard amplifier. The circuit is similar to the L3, but completely different circuit than the others, though the controls appear similar on the outside.
  • L7 (Model 309): Guitar combo amp, 100W, 4×10. Identical circuit to the L5 but with a different speaker configuration.
  • L9 (Model 312): Guitar combo amp, 100W, 1×15. Identical circuit to the L5 but with a different speaker configuration. Speaker is an Electro-Voice EVM-15L.
  • L11 (Model 313): Guitar head, 200W. Identical preamp circuit to the L5 but with a 200W power amp. Originally came with a 4×12 cabinet.
  • K5 (Model 332): Keyboard combo amp, 100W, 2×12. Very rare, issued later than the others (ca. 1979) along with the L6 bass combo amp. The circuit has resemblance to the L3 and L6, but also substantial differences in many areas.

The model numbers appear to be assigned sequentially based on when they were designed. Looking at the schematics, it’s not hard to tell that the L5 was designed first, then expanded into the 7, 9 and 11 by changing the chassis and speaker configuration.  After that, they designed the L2 and L4 bass amps which were largely the same as the L5 but with some instrument-specific tweaks. Then came the L3, which uses a CMOS inverter topology not found in any of the previous designs. The L6 and K5 were very similar to the L3 and appear to be derivative in the same way the L2/4 were derivative of the L5.

Suffixes

The “X” suffix (e.g. 308BX) indicates that it is an export model, manufactured in the United States but intended for the overseas market. The only difference is an alternate power supply designed for higher line voltages, and some of the power-handling components being raised from the circuit board to conform to foreign regulations.

It is unknown for certain what the “A” and “B” suffixes refer to. The service manual indicates that there is an “A” and “B” version for each model, and then separately mentions that the “X” refers to units manufactured for export. Some of the schematics indicate that they apply to (for example) “MODEL 308 A, AX, B, BX”. In other official schematics, though, the model variants are listed only as “A” for domestic and “BX” for export. This correlates with our real-world experience in looking at several dozen units. We have never seen either an “AX” suffix or a “B” without the “X”.

Moog SynAmp

Moog Syn Amp with Lab Series logo on cabinet

Moog Syn Amp advertisement with Lab Series logo on cabinet

The Moog SynAmp was released in 1978[3] and was discontinued in 1981, the same time as the Lab Series. The SynAmp was apparently marketed under the Lab Series line according to the advertisement to the right. While the unit itself carries the Moog logo and has no reference to the Lab Series, the speaker cabinet does carry the Lab Series logo based on the advertisement, although most SynAmps have been long separated from the matching cabinets (and may have been sold separately to begin with). The units are cosmetically unrelated except that the primary control plate text on the SynAmp uses the same typeface as the “Caution” text on the rear of the Lab Series amplifiers.

The model number (301A) indicates that it was developed around the same time as the Lab Series and was at least developmentally considered part of the Lab Series, even if the marketing was a little inconsistent as to whether it was a Lab Series product or not. Since it carries an earlier model number than any of the Lab Series line (the L5 is 308), it’s possible that the SynAmp was actually the first model to be developed and that its concepts were later adapted for guitar.

Cosmetics

The only cosmetic difference within a single model was that the faceplate was offered in two styles, black and copper. This was purely a cosmetic option and does not indicate year of manufacture, export vs. domestic versions, or anything else. Both styles were available for the entire Lab Series run.

Speakers

Speakers were run-of-the-mill OEM models from CTS which were very common in American-made amplifiers from the 1970s. The speakers are not considered to have any “mojo” with regard to the Lab Series tone, and in fact are considered by many to be the weak point of the amplifier. An aftermarket speaker upgrade is a worthwhile investment.

The amplifiers were designed with an 8-ohm load in mind, so in the case of the L5, it came equipped with two 16-ohm speakers wired in parallel. Most of these speakers had circular magnets, but some had square magnets. This does not appear to correlate with a particular time period, so it is likely that they just took whatever CTS sent them.

Ty Tabor / King’s X tone

One of the more legendary users of the Lab Series amps was Ty Tabor from King’s X. Guitarists still salivate over his tone on the band’s first four albums (Out of the Silent Planet, Gretchen Goes to Nebraska, Faith Hope Love, and King’s X), but he kept his recipe a secret until 1996, a few years after he had completely changed his rig for their fifth album Dogman (1994).

Ty spilled the beans in a Guitar Player interview in May ’96:

  • Fender Elite Stratocaster (circa 1983-1985; has an onboard preamp with mid boost, a precursor to the Eric Clapton Strat)
  • Lab Series L5 (second channel, compressor off, using the preamp output)
  • Post-preamp EQ to thicken up the low end
  • Alesis Midiverb II for stereo chorus (program 62, “Chorus B”)
  • Very slight delay in one channel (<100ms)
  • Stereo power amp, either a Mesa 2:Ninety or a Crown Micro-Tech 600
  • Two 4×12 Marshall cabinets (slant cabs for recording, bottom cabs for live)

Here are the settings he used on the L5:

  • Channel 2, “Lo” input
  • Bright: off
  • Volume: max
  • Bass: 1:00
  • Frequency: 3:00
  • Midrange: 3:00
  • Treble: max
  • Multifilter: 1:00
  • Compressor: off
  • Master volume to taste

Can you get Ty’s tone with the amp alone? Nope. It is certainly an indispensable piece of the puzzle, and it probably brings more to the table than any other ingredient, but there is something about the interplay of all the different parts. It’s a wonder that he ever stumbled across this combination.

Appendix: Pearce Amplification

Dan Pearce, a member of the original Lab Series design team at Moog, decided to design a new solid-state amplifier that expanded on some of the new ideas he had been developing for the Lab Series line when Norlin discontinued it. He spent five years developing it before formally beginning Pearce Amplification around 1985. The G-1 used many of the same ideas as the Lab Series, especially relating to the tube emulation, and it’s still considered to be a fantastic piece of equipment. They later released the G2x, G3, and a few related bass amps. But despite some venture capital investments, Pearce was also unable to turn much of a profit and had to liquidate in 1993. Dan Pearce went on to work for Applied Research & Technology (ART) during the 1990s, followed by Bose for 20 years, and is now an independent consultant as of 2020.

Appendix: Lab Series 2

While Pearce Amplification could be considered a true spiritual successor to the Lab Series, there is also an impostor which deserves a mention. The “Lab Series 2” was a very brief cash-grab by Norlin to squeeze a few more sales out of the Lab Series brand name as their ship was sinking. These amplifiers were manufactured by Garnet and labeled as Lab Series amps, but they had nothing to do with Moog or the original series from an engineering perspective. These Garnet-built amps were also relabeled as Gibson, Genesis, Hohner, and many more, over 30 relabeled brands in all, and are called “stencil” amps by Garnet fans.[4]

Notes & references

  1. This document by Dan Pearce, one of the original team members of the Lab Series amplifiers, has a little bit of inside information about the development process of the Lab Series. Some of the information in this section is sourced from here. It’s a good read.
  2. Bob Moog Timeline, moogmusic.com
  3. Based on the date on the service manual.
  4. Garnet Stencil Amps, garnetamps.com