The Lectrolab R400 series seems to be a rare bird, even by Lectrolab standards.

Lectrolab model identification can be difficult because the model numbers are often not printed on the amps themselves.  In addition, each model has “updates” which append a letter at the end of the model number, such as a “B” or “C” (there is never an “A”).  Many of the “updates” are minor changes, but some are quite significant, so a R400, for example, is a very different amp than an R400C.  Almost every amp in the “R” series has at least one revision (designated as “B” at the end of the model number), and usually two, the second revision being designated “C”.

With so few amps in circulation, a minor omission in description can create real confusion.  For instance, the “R400” schematic below is the only one I can find.  However, look at it closely and you will see there are two volume pots, and one tone pot.  In the photo on the cover of the R400 Photofact manual (available on eBay, I don’t have one) there are only two knobs.  Although the internet-available schematic is labeled as R400, the title appears to have been added after-the-fact.  To make matters even more convoluted, a handwritten note on the schematic referenced a R400C, for which no documentation can be found.

With this wealth of information, or lack of it, I reach the following conclusions:

  • R400 – There was an R400, and the Photofact cover picture is probably correct.  It a single channel amp with one Volume and one Tone Control.  One seller listed this amp as being 16″ W X 19″ H X 10″ D with a 10″ or 12″ speaker.
  • R400B – The schematic below (also from Photofact, copyright 1957) titled”R400″ is actually an R400B, because it has TWO volume controls.  This amp schematic appears to be an upgrade of the Lectrolab R300, and no doubt it was an upgrade of the R400 as well.  Compared to the R300, another 6SN7 has been added to the preamp, its dual triodes providing an extra stage of amplification as well as a dedicated first stage for input number three, which was probably meant to be a mic or accordion input.  Inputs one and two share their own first stage.  Input three has a separate input stage.  Beyond the first stage, the R400B and R300 are almost identical.  There is no tremolo.  I do not know if there were changes in the transformers, speakers, or cabinet.
  • R400C – We finally have photos of this one below.  2-12AX7′s, a 6V4 rectifier, and a 6BQ5 (EL84) output tube. It has a 10″ speaker.  This amp is notable for the addition of TREMOLO to the 400 series.  And now (6/7/11) we have a schematic drawn and sent by Bob Walker.  Thank you, Bob!

R400 Schematic:

R400C Schematic:

Photofact Manual – Trapezoidal or Perspective Distortion?


8/17/2010 – An eBay auction ended 8/14/10 for this Lectrolab, which I believe is an R400B although no model number can be seen on the amp itself:

R400C reviews at Harmony Central: http://reviews.harmony-central.com/reviews/Guitar+Amp/product/Lectrolab/R400C/10/1

Here’s one (click to enlarge).  Everyone raves about these.  Wish I could find one…


Well, we found a R400C! (10-24-2010),  Reader Craig Olson sent these pics.  He also sent pics and schematics for the S400, which is another great contribution.  Thank you, Craig!  Craig writes:

“The R400C is ink-stamped Oct. 1965 inside the chassis.  The baffleboard, grillecloth, and speaker are not original but made a big improvement in volume and tone.  The original mushy pressboard baffleboard absorbs speaker energy and dampens the sound in my opinion.  The chassis [appears] untouched from 1965.”


Matt Olson (his comments below) provided these pictures of his super-fine R400B.  Thank you, Matt.  I guess R400B’s seek out Olsons!


13 Responses to R400

  1. Craig Olson says:

    I have two Lectrolab 400 models… The R400C is from the early/mid 60’s, in tweed, with rear controls. The amp uses two 12AX7’s, a 6V4 rectifier, and a 6BQ5 (EL84) output tube. It has a 10″ speaker, and does have tremolo. My mid-60’s model 400S has black tolex with the long aluminum fold-down handle, and the long block-letter logo. It uses a 6AV6 and a 6AU6 in the preamp, with a 6CA4 rectifier, and a 6BQ5 output tube. This amp also has tremolo. It has two 8″ speakers.
    I could probably send photos, and I think I have the schematics (on the inside of the back panels) which I could include also. Please let me know if this would be useful for your website.
    Both amps are mean and nasty, but the R400C is my favorite small amp ever…and I have several small old amps. I changed the “mushboard” baffleboard to vintage 5/16″ plywood, and I stuck in a Weber speaker, but it is otherwise unmodified. Oh, and I did retube it. These changes made the amp really sing… at least to my ears.
    Let me know if you want pics. Regards, Craig

  2. Craig Olson says:

    Hi. I am finally getting the photos of the amps to you. I will try to send the photos one at a time with a brief caption. Feel free to use them as you wish. Regards, Craig

  3. Matt Olson says:

    I have a Lectrolab R400b from the late 1950’s. 3 inputs 1×10. My favorite amp of all time, looks a bit different from the ones detailed above. I think the earlier models have the red stenciling for vs. the white on the mid to late 60’s models. Check out a few pictures here: Lectrolab R400b.

  4. Eric B says:

    Nice to see some info on these, finally. I own a R400C very similar to the one featured here, only all original. I picked it up years ago and have owned many amps since, but the Lectrolab remains a favorite for it’s natural, raw sound. With a Tele it really nails the early Page tone, enough to make me question the validity of the Supro story.

    • alexage1 says:

      Thanks for the comment, Eric. It seems to be the general concensus that a R400C (and others) can go head to head with almost any amp, and sound just fine. let’s be thankful that Lectrolab/Sound Projects has not yet been associated with any rock gods, else they wouldn’t be as affordable as they are!

  5. Charlie Barath says:

    Glad to see there are others interested in what I consider to be my best “back room” find of all time. I have a Lectrolab R400 that I stumbled upon in the back room of a local music store about 10 years ago; best $200 I ever spent. In case you’re wondering, I’m not a guitar player, but a harp player, and I couldn’t be happier with the way this little monster roars. It ain’t pretty lookin’ by any stretch; it’s got a hole in the grill cloth, my dog ate the front, right corner, and up until last year, it had a braided rawhide handle that I made to fill in for the original leather one that ripped in two. (dryrot) I had an amp tech replace the original power cord and he put a new, vintage style handle on as well. One of the coolest things about it is the mystery of it I’m always getting the questions: “What is it?” “Who makes it?” “Want to sell it?” (NO). This amp always delights and I use it for all of my gigs, small or large. I just mic it through the PA when need be. I have no idea what one of these is worth, but it would take a considerable amount to get me to part with mine. Oh yeah!

    • alexage1 says:

      Charlie – thanks for your comment. I love that the dog ate it. I’m curious about the exact model number of your amp – Is it a R400, R400B, or R400C? Also, it would be great to have some pics – can you send any in to lectrolab@gmail.com? Thanks!

      • Charlie Barath says:

        My amp is indeed a R400. Controls include just volume and tone. (lots and lots of tone) If I can get past my rudimentary computer skills, I’ll get you a couple pics. Please be patient with me.
        Speaking of this particular amp, do you think it would make sense to build a new cabinet out of some more substantial materials and have the guts transfered over? I’m a carpenter by trade and could make a dandy cab. I was wondering if such a change would improve the sound and/or performance, getting away from the somewhat mushy press-board.
        I’m also just a bit curious as to the possible value of it.
        Thanks, Charlie

      • alexage1 says:

        Hi Charlie – How exciting, I haven’t found even one picture of a R400 (not B, not C). Pictures would be great, especially if they include any schematic that may be pasted somewhere inside!
        Regarding a new cabinet, it’s really up to you. Some folks would think it’s terrible to violate the sanctity of a vintage amp of any sort. Others are all about tweaking. At the end of the day, it’s what you want that matters, right? If it was me, I’d leave it as is because:

        1.) You can’t buy, or make, something that looks like it, it’s unique;
        2.) It’s a low wattage amp like a Fender Champ, it will NEVER sound wall-shaking;
        3.) BUT, for some reason these little guys can sound like a wall of Marshalls when they are close-miked and recorded or fed to a PA. Mushy cab or not.
        4.) It’s easy to get a humdrum Champ-type amp with a solid cab, it’s harder to get a R400

        That said, you could always make a new cab and keep the old one as well, it’s easier to swap the chassis back and forth.

        If you do make a new cab you might consider putting a 12″ speaker in it, THAT will make a obvious sonic difference – Louder, a little cleaner.

        Value of an R400? Not well established, and depends on condition. Most likely between $100 and $200, maybe a little more if mint. Value of the fun they bring? PRICELESS!

  6. steve warner says:

    Alex and Charlie,
    The Harmony, Lectrolab, Valco mystery. I still hear people saying that Valco built all the Harmony’s. Your site tells it all by looking at the exact chassis shapes and circuits.
    **One thing about the picture above of the R400B that was on ebay in 8/2010….That’s not a 400B. It might be a 500B because I see 3 large tubes and the one on the right has the long plate = a Rectifier and the other 2 must be the 6V6’s.
    I too play Harp, Charlie.
    I own a killer 305A Harmony that I picked up on ebay for a WOPPING $162.50 in about 2003-4(?) IT was dead, but the OT wires had come off…easy fix. Went through it and replaced a few resistors and put in a new speaker (and I lost the ripped Jensen…DOH!) with a Weber 12A100, new PT, replaced the OT but still have the working original, changed coupling caps to .1 Sozo Mustards and a few other Mustards in the tone circuit and lowered the preamp plates to about 140. Due to the Cathodyne PI it doesn’t sound like much until I get er up to about 4 with a hot mic and then that thing just throws out the creamiest drive…move away from the amp and get it up to 6 and WOW!. And I just happen to love the cheap press board for a cabinet…I think it adds warmth and that allows more bright tweaking if necessary. I’ll never sell it so I don’t care about modding the guts. Really throws off the die hard Fender guys who paid 10 times more for their Deluxes and Harvards and mine sounds just as good. Shhhhhhhhh!

  7. Tim Dowden says:

    Hi Tim here, you problably have read some of my Harmonycentral reviews of my R400C, well as you all know it is worth ervery penny paid. It looks exactly like Craig’s but in black covering.

    Just one thing I want to share…I recently put a NOS Raytheon blackplate 12ax7 in the 1st valve spot and WOW, it really shines even better than before. It seemed to add some oomph and even more natural distortion, I will not swap out this tube anymore.

  8. Stumpy says:

    I bought a Philharmonic P44 for $100 this week, didn’t know much about it other than I thought it had great tone for my harp. With some research it seems to be a R400C. It looks to be all original. It’s not pretty, it looks like it had sat in an inch water, the bottom board of the cabinet is warped and needs a little repair, bottom of the grill cloth was loose and it is missing the back panel. Brought it to band practice and a gig, this little monster kicks ass. It has great crunch and tone. I will go through it and check the tubes, speaker and caps at a later time. My guitar player who is a “tone freak” tried it and loves it, and is trying to find another one. I won’t ever sell it.

    Does anyone know what Harmony model number that would be to match the R400C ?
    Does anyone know the original brand and model of speaker that came in the R440C ?

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