Lab Series L5 Preamp DIY PCB
Lab Series L5 Preamp PCB

L5 Preamp - L5 Preamp Guitar Pedal PCB

$25.00

Available

A faithful recreation of the preamp section of the Lab Series® L5 amplifier designed by Moog and marketed from 1978-1981.

Not sure where to start? Check our Resources section for more information on building your own guitar pedals.

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Disclaimer

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.

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Project overview

L5 Preamp PCBThis is a pedal conversion of the preamp of the Lab Series® L5, 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 fed 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 the “return” jack of an amp with an effects loop). The main difference will be the volume you run it at. This thing is capable of enormous volume, far more than any stompbox, so if you are using it like a pedal, don’t feel like you are doing something wrong by keeping the master volume down really low!

Along with the main PCB, two footswitch PCBs are included to make the wiring easy. One of them handles the master bypass and the other handles the channel switching.

Parts list

I’ve made a spreadsheet of the parts so you can very easily order most of what you need from Mouser. The remaining items can be obtained from Small Bear or Mammoth Electronics in the United States or any of the major European part stores. There are no “unobtainium” or mojo NOS parts to hunt down. (For international buyers, although Mouser doesn’t get talked about very much, they actually have very good prices compared to other international stores and shipping is usually free.)

Instructions:

  1. Open the spreadsheet.
  2. If there are any parts you do not want to order, download the spreadsheet using FileDownload as and delete those parts. (Or you can just remove them from your cart once they are added.)
  3. Browse to Mouser’s part list importer.
  4. Copy the Mouser Part Number and Quantity 1 columns from the spreadsheet and paste them into the “Step 1” box.
  5. Click Import. The items will be added to your cart.
  6. Do an in-page text search for the word “backorder” to see if any parts are out of stock. There will likely be at least one or two at any given time, and you will need to find a substitute on your own. The easiest way to do this is to go to the product page and use the “Show Similar” feature. The important parameters are the value, voltage rating, and physical dimensions (width, length, height). The brand and series are not important and should be left out of the comparison.

Not all of the parts are available from Mouser. You’ll need to get the pots from someplace else as well as the two CA3080 ICs and the 2N5457 FET. I recommend Small Bear Electronics since they carry nearly everything else you’ll need, although as of this project’s release, they don’t carry a 2k or 2.5k audio taper potentiometer, so you’ll need to get that from someplace else. The spreadsheet has links to other stores for each of the parts that are not available from Mouser. Also, depending on where you order, the pots may not all be PCB-mount, so you should either run wires from these pots to the board or solder a section of solid-core wire to the lugs to make your own PCB-mount equivalent.

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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 I’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 since 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 given 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 a shining exception. 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 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, Allan Holdsworth, and Joe Bonamassa, to name a few.

However, their sales figures did not meet the expectations of the parent company and Norlin discontinued their production after four years on the market. The last amplifiers were manufactured in 1981. 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, 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. 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 amps in the series. 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. 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. Completely different circuit than the others, though it bears some resemblance to the L6.

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 refactored into the 7, 9 and 11. After that, they designed the L2 and L4 bass amps along with the L3, which uses CMOS technology not found in any of the previous designs. Then the L6 and K5 were the last two to be designed.

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 my real-world experience in looking at several dozen units. I 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 likely 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.

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Ty Tabor / King’s X tone

One of the more legendary users of the Lab Series amps was Ty Tabor from King’s X. His tone on the first four albums (Out of the Silent Planet, Gretchen Goes to Nebraska, Faith Hope Love, and King’s X) was drooled over by many a guitarist starting in the early 1990s, but he kept his recipe a secret until 1996, a few years after he had completely changed his rig for their album Dogman (1994).

Ty spilled the beans in a Guitar Player interview:

  • 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. It’s without a doubt the most obscure gear recipe for any well-regarded tone that I am aware of.

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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 and now works at Bose.

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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 a technical standpoint. 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]

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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