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!
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!