The "SPEKTR-1" Wah-Fuzz-Vibrato
Last updated 6/16/24
By Paul Marossy
Here is another "very rare" Soviet-era oddity. While perusing ebay listings I saw this unusual device and I watched a couple of YouTube videos demonstrating its
various sounds. It sounded
pretty cool so I rounded up a schematic and that was also very interesting, enough so that I wanted to pick up one of these units to analyze and
have fun with. I ordered mine from Latvia, and it arrived surprisingly quick - only took nine days for it to arrive in my mail box. Unfortunately it
was a complete hack job inside and I had to do a lot of work to get it back to how it was supposed to be and to fix what wasn't working. In this process I was
able to verify that the schematic linked at the bottom of this page is correct, and that really saved the day. Some of the pictures below are not of my unit,
which was made in 1980, but I wanted to put together all of the details on this thing in one place. It was another interesting journey of discovery doing the research and detective work on this one.
I'm not 100% sure who manufactured it specifically, but I did come across a picture of what I believe to be the first version of the box it came in (see bottom of page), and part of the text on it translates as "Orlov UVM". One of the other box types also has the Orlov UVM logo on it, so I assume that is who manufactured these things. Orlov UVM was a manufacturer of radios, control computers and things along those lines. They eventually branched out to making various household devices per Resolution No. 1056/1976 of Central Council of USSR Communistic Party. Orlov UVM was officially in operation from 1967 to 1996, declaring bankruptcy in 1996. Many of their products were a Spectrum-something. For example, the "Spectrum-11" was a "color music set-top box", a strange looking contraption with colored things on it that looked like giant LEDs. I'm not sure what exactly it did. There was also a Spektr-2, Spektr-3 and a Spektr-4, all of which were also guitar effects. Additionally, I found a webpage that claims that the Spektr-1 was made in a factory at Novosibirsk, and that Spektr was the most expensive guitar effect pedal in the USSR. If this is accurate, it would have been the Novosibirsk Electromechanical Works, established in 1934. However, Orel, a city about 200 miles south of Moscow is where these appear to have actually been made. I say this because of text that can be found in the back of the owners manual that refers to Orel specifically.
In any case, these pedals were apparently sold for 58 Rubles ($35). They were produced from 1975 to about 1981. There were a lot of inconsistencies
between production runs. For example, some versions had a grey treadle lock and on others it was red. There's about six to seven different versions of the rubber on the top and bottom sides of the pedal - the patterns/texture are all different from each other (see bottom of page). The color of the wire inside varied - at least five different colors were used. There were two to three different versions of the nameplate on the side. There's at least four different versions of the box it came in (see bottom of page). Seems like a lot of variation for something that appears to have been manufactured for 4-5 years. Just some things I noticed in the information gathering stage. It was a real task
and I spent hours searching but I finally rounded up a copy of the original instruction manual, thanks to some friendly people at a Russian guitar related forum (as IN Russia). I swear that must be one of the rarest documents on earth!
One interesting aspect of the circuit is the way the gnarly sounding fuzz is produced - it utilizes a full wave rectifier-like arrangement with four zener diodes. The "boost" circuit is like a second kind of higher gain fuzz, which works better for chords and more than one note at a time. The "other fuzz" produces intermodulation distortion, so it
doesn't really sound very good for more than one note at a time.
The other part I found interesting was the wah section. It's a twin-T type circuit which has a distinctive sound, sort of like an autowah. Both the fuzz and wah circuits could be good sounding
stand-alone circuits, in my opinion. The LFO circuit (vibrato) is also interesting, haven't seen anything quite like it. Its speed is fixed at about 8 Hz (mine measured
7.81 Hz). The LFO section has its own dedicated 9V power supply and the rest of the circuitry operates on 6.8V via another zener diode. Most of the transistors are germanium
and a few of them are silicon types. With a total of twelve transistors, mostly germanium, I suspect the reason for using two 9V batteries was as much to lengthen battery life as it was for creating two isolated power supplies. According to the factory instruction manual, battery current draw is "no more than 5mA from each battery". If you want to learn more about the circuit specifics, check out my translated & verified schematic linked at the bottom of this page. It's not the original factory schematic but whoever drew it up did a pretty good job on it. One thing to note is that some versions omitted the 6.8V zener diode and 1.2K resistor on the 9V supply on the PCB, as can be seen HERE. I am unable to determine why some units have the zener diode and 1.2K resistor, and why some don't. It appears that around 1980 the zener diode was added to the circuit. I don't know if any other part values were changed when the zener diode was added.
Below is some more detailed information about this very unique guitar pedal.
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The design of this pedal is most unusual by today's standards. It's also pretty large - measures 10.5" tall by 4.625" wide by
2" high and it weighs 3 lbs 1 oz. The chrome treadle operates the wah section and has an unusual feature: a sliding mechanism which
locks the treadle in place, which effectively bypasses the wah for a straight clean sound. You can't exactly use this feature 100% hands free however (more
on that below).
The treadle spring is also quite stiff. |
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On the right side of the pedal there is the input, output and external power jacks, along with the push button power on/off switch. The jacks are the standard 5-pin DIN type found on Soviet pedals from this time period. |
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In this view you can see the slot in the treadle which the pin on the locking mechanism passes through. As soon as you step on the treadle the lock disengages. You can't lock it without using your hands, or at least I haven't figured out how to do it otherwise. Can't really do that with your foot because you have to push the treadle down lower than this slide mechanism, so because they're not flush with each other it kinda doesn't work. |
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This is the bottom. Most notable are the four holes which can be used for adjusting trim pots inside. From left to right: treble boost, fuzz output level, wah output level (which is also the overall loudness), and the wah sweep adjustment. The square battery cover is at the left. |
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With the battery cover removed, the dual 9V battery compartment is revealed. One battery is dedicated only to the LFO section ("vibrato") and the other one powers the rest of the circuitry. I have also seen versions with a blue battery holder. |
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With the bottom cover removed, you can see that it has a fairly large PCB inside and a neatly bundled wiring harness. There are a lot of wires inside this thing! Interestingly I've seen dark brown, white, red, green, yellow and blue wires used in different examples.The power and vibrato switches utilize the same weird 12-pin DPDT push-button switch that was used in the Univox Uniwah. |
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The typical Soviet germanium transistors can be seen here, along with the electrolytic capacitors, which have all been changed in this example. |
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At upper left is one of the unique aspects of this design, the wah pot and actuator. Just when I thought I've seen every possible method for rotating the shaft of a potentiometer, yet another method appears out of the wood work! |
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The wah pot is fastened to a bracket which in turn is fastened to the cast enclosure. Notice the wound up flat spring, kind of like what can be found in a wind-up mechanical clock. |
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The way that this works is there is something akin to a sewing machine bobbin, which some very heavy "fishing line" is wound around. The coiled flat spring is also attached to this bobbin arrangement. What the coil spring does is keep tension on the "fishing line" at all times. Kind of along the lines of the Ernie Ball volume pedals but executed differently. It's kind of clever but if you ever acquire one of these, hope and pray that you don't have to mess with it. It is infuriatingly difficult to work on and get adjusted. |
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This "fishing line" is connected to a tab stamped out of the top of the treadle, via a spring steel loop. Once again, very difficult to work on as there is limited space to get any tools in there, etc. but when it's working properly it does the job. |
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This is what the foil side of the PCB looks like, before I reinstalled two jumper wires that the previous owner removed for unknown reason(s). |
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A schematic was included in the instruction manual that came with it. See link below for a copy of the factory instruction manual (bottom of this page). |
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A section of the owner's manual states that it conforms with TU-2501-01-866-75, which I assume is something similar to our FCC regulations. It also says that the factory warrantied everything for one year, except the potentiometer, which was expected to last for 125,000 cycles. In the event of warranty work needing to be performed, it instructs the owner to contact an electronics repair shop, not the factory. See link below for the factory instruction manual (bottom of this page). |
If you decide to acquire one of these things, there are a few caveats. One is that it is just difficult to work on if anyone has done anything
inside of it before you got it. For example, in my unit, the previous owner had took apart the nice neat wiring harness and all the wires were loose inside like a bowl of
spaghetti. That was disappointing. Expect the original electrolytic caps to be dried out - 50% of them were bad in my unit. When you replace a part it is
almost impossible to not damage the very small copper tracks on the PCB, and they want to easily lift off the substrate. To add to the frustation, expect 50% of the 35 or so
wires inside to break off from where they are supposed to be when you are changing out the caps. But after I endured all that, I finally got my unit tidied up inside
and back to working condition except for the "vibrato" section which had me a bit baffled. Someone had obviously replaced the P416B transistor (V4) some time in the past.
I took it out to put a socket in its place so I could easily insert a replacement into it without worrying about screwing up more of the back side of the PCB, and while doing so I had a thought that perhaps the transistor was put in backwards. So I tried rotating it 180 degrees and then the tremolo came back to life! Hooray! Oh, did I mention the nightmare of dealing with the pot actuator system? When I recieved my unit, that was also completely hacked. Took me a while to understand how that actually worked, how to restore it back to the way I believe it came from the factory and to figure out exactly how to adjust it.
A few things to note about circuit operation:
1. The trimpots are interactive! R13, R19 and R43 all affect each other to some degree.
2. R19 sets the Fuzz output level. R43 (Wah Sweep) needs to be adjusted so that there is no oscillation when the wah function is used. If not properly adjusted, it will make a howling noise when the treadle is at certain positions.
3. R13 (Boost input resistance) must be adjusted so there is no oscillation when using the Wah function. If not set to an optimal position, it will make a sharp shrieking noise with the treadle in certain positions, and you will also get a weird but short, sharp sounding artifact whenever you mute the strings. It's hard to describe but you'll recognize that sound when you hear it.
4. If R43 (Wah Sweep) is not optimally adjusted, you may get howling noises when using the Fuzz or Boost functions (see 2 & 3 above).
5. If R13 is set incorrectly, the sound will momentarily cut out completely when you pluck the strings forcefully. Find the position where this does not occur, while also finding the place where no oscillation happens when using the Wah function.
6. If you find the tremolo to be way too choppy sounding, like I do, you can replace R21 with a 500K or 1 Megohm trimpot wired as a variable resistor. This will allow you to dial it in to something more reasonable. I wired mine in series with the existing 18K resistor.
Be patient, and you'll eventually get everything adjusted for optimal operation. It is kind of a process of trial and error. Yes, it is a pain in the rear to do and if I had a third arm it would have made it a lot easier! I spent a considerable amount of time fiddling with all these trimpots before I figured out all the things listed above. It would also be cool to be able to vary the speed of the tremolo but I need to consult some people more knowledgable than myself on that one. It doesn't appear to be very simple to achieve that.
I have to admit, these Soviet-era guitar effects are most interesting. They are just so unusual and most them appear to be unique designs as far as the
circuitry goes, and well, with pretty much everything else too. There does not appear to any copying of designs as I've seen in products that did not
originate in the Iron Curtain. I'm not really a fuzz guy but I am rather fond of how this one sounds.
SPEKTR-1 Factory Instruction Manual