~1964 Lectrolab R500-C Cream

Offered for sale:

Vintage c1964 Lectrolab R500-C combo amplifier.

This amp is in very good condition, fully functional, the speaker is non-original Fender Eminence, and the power supply has been replaced. Cosmetically the amp has been recovered and the covering is showing playing wear, numerous marks and the usual patina."

Since the data on these amps is rare and quite specialized, we are quoting published writings regarding this amp and it evolutionary line.

Lectrolab amp breaks all the rules

Quoted from Robbie and Laura Reynolds 08-18-2006.

“I had the pleasure of looking inside a Lectrolab R500-C and drawing a schematic of it. If you’re not familiar with this amp, it is one of the greatest super-blues-tone amps you can ever get. It has the deepest, thickest sound of any amp I’ve ever heard. Not only that, but it is also fairly loud before feedback.

The strange thing about this amp is that it breaks several of the “rules” that you hear about good harp amps. The preamp consists of two 12AX7s. It sounds great this way, so there is no need to switch to lower gain tubes. Our buddy Gerald Weber states authoritatively that cathode biased power tubes are the way to go for a harp amp, but the Lectrolab uses a very strange -15-volt bias supply taken straight off of one of the high-power leads at the rectifier.

Another thing is the coupling caps. Everybody seems to agree that .1 uF capacitors let more bass through, but the Lectrolab uses .01 uF. Regardless of what anybody says about .01 uF caps, this is a very deep-sounding amp. Another rule that it breaks is the one about ground loops caused by using the chassis as a ground path. Things are grounded willy-nilly all over the place, and the filament leads aren’t twisted together. This is supposed to cause a hum nightmare, but the amp is almost silent.”

Lectrolab additional model background info:

R500

R500: 2-12AY7; 2-6V6; 1-5Y3GT

R500B: 2-12AX7; 2-6V6; 1-5Y3GT

R500C: 2-12AX7; 2-6BQ5 (EL84); 1-6CA4 (EZ81)

Speaker: 1-12″

The Lectrolab R200, R300 and R400 are all firmly ensconced in the “student” amplifier category. They were single-ended designs with one 6V6 output tube, or similar. They were similar to a Fender Champ in this regard.

Lectrolab upped the ante with the R500, which sports a 12″ speaker. Like theR400B it has individual first stage channels for instrument and mic. Each of these use half of a 12AY7, and have their own volume control. The signal from the first stages are mixed and then sent through an inverter (another 12AY7). The inverter output drives a push-pull pair of 6V6 output tubes, with a shared tone control along the way.

The Lectrolab R500B replaced the paraphase inverter with a concertina, or inverter, perhaps in a quest for improved fidelity. It also added a fourth input, which did not provide any further functionality, it still had two individual channel first stages, one for inputs one and two, the other for inputs three and four. The control panel remained the same, two Volume and one Tone control

The Harmony H305A is the same amp as the Lectrolab R500B. Sound Projects Company must have produced these for Harmony.

The Lectrolab R500C adds another Tone control, so there is one for each channel. The tube compliment has changed. The Lectrolab 500C has 9-pin tubes throughout, which means the 5y3 rectifier has been replaced with a probable 6CA4/EZ81, and the 6V6 output tubes with 6BQ5, 7189, or EL84. In addition, the R500C is reputed to have fixed bias output tubes. All this makes it a very different amp than the R500 and R500B, although there is little cosmetic change.

If a tweed Fender Deluxe is your kind of thing, you are probably going to like theR500. Quite a step up from the R300 and R400.

Imperial Guitar states:

“We test every used amp and pedal when we buy it and bring it up to our standards before we offer it for sale. Then we burn it in for an hour or so before we ship so that there are no surprises.”

*Please note: we do our best giving descriptions of used pieces. We have found it impossible to describe every mark on an instrument or amp that is not in the "mint" category. Also, what's important to you may not be important to someone else. For example, you may say, "I don't care what it looks like as long as it plays or sounds well." Another person may say, "Body cosmetics are very important to me so tell me about every scratch, nick and blemish." So, please ask the questions that are most important to you. If you ask they will be answered. They are free and there's no limit. Additional photos can also be made available.

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