effdub, Author at EffDub Audio

If you’ve searched ebay for EL84 / 6BQ5 vacuum tubes, you’re probably also seen listings for mysterious Russian-made tubes with the part number 6P14P (or the Cyrillic alphabet equivalent 6П14П) and wondered what the heck was going on with those. What is the difference, really, between 6P14P versus EL84?

6P14P versus EL84: The Simple Answer

The short/simple answer is: “Not much!” Mostly the differences come down to minor spec variations and that 6P14P tends to last quite a bit longer. A typical operating life for 6P14P is approximately 10,000 hours, whereas the average new-production EL84 tube has an expected life of 3,000 to 5,000 hours.

Another interesting difference is that the 6P14P has an astounding 10% variance in acceptable heater voltage requirements. An EL84, on the other hand, requires a very precise 6.3V heater voltage.

6P14P tubes (valves) are pin-compatible with EL84 / 6BQ5 tubes and will work just about anywhere you would normally use an EL84, including guitar amps, tube radios, and hi-fi stereo gear (like dual mono-block amplifiers). It’s possible there is an application where a 6P14P wouldn’t be up to the task, but I’ve not run across one yet.

6P14P History: Soviet Military

I’m not Soviet-era tube expert, but based on a plethora of Google research, it would seem that 6P14P tubes were made from the 1960s through at least the early 1990s. They were made specifically for Soviet military use and are very robust, being heavier and generally having a much longer service life than a comparable EL84. As far as I can tell, all 6P14P tubes were made at the Reflektor manufacturing plant in Saratov, Russia. This is the same factory that makes Sovtek tubes, as well as several other popular new-production and reissue tube brands, including: Electro-Harmonix, Tung Sol, and Mullard (and probably others, but note that the new Telefunken tubes are made by JJ Tubes in Slovakia).

6P14P Date Codes

Most tube manufacturers don’t include date codes on their tubes at all, and this includes the vintage brands of the past. However, 6P14P tubes do have a very simple date included on almost all the tubes I’ve seen. It’s right under the logo and part number and is a very simple four-digit code showing the month and then last two digits of the year. In the photo below, the tube shown has a date code of 07 82, signifying it was was made in July of 1982.

Also note that during some years, the month and date numbers will be reversed. I have one 6P14P, for example, with a date code of 91 05, meaning it was made in May of 1991.

Where to Buy 6P14P Tubes

These tubes are readily available on ebay and generally at very reasonable prices. However, almost all sellers are in former Soviet states (Ukraine and Belarus are popular), shipping costs can be high, and mostly what is available is pulled (used) old-stock tubes. Still, for the price and because 6P14P tubes tend to be very hardy, the risk is low as a US buyer.

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Effects Projects

February 23, 2023 effdub

Box of Hall – DIY Reverb

I came up with the Box of Hall reverb circuit way back in 2012. The Belton BTDR-2 bricks had just come out, and I wanted to have the first working circuit out on the DIY scene. A whole LOT of people copied this design and called it their own, but this one is the original (from your old pal culturejam).

To be blunt, this design is largely based on the Belton application note’s example circuit, but I added a high-pass filter tone control and changed up other filter cutoff curves as well. I also added an op amp buffer for the virtual ground (VREF) used to bias the other three op amps in the circuit. A subsequent version also added a wet feedback loop to allow for better control of decay time, as well as wacky ambient swell capabilities. I will post that version sometime in the future. But for now, this is a nice, simple reverb circuit that anyone can build and that will sound great.

There is a fair bit of modulation happening in all circuits using the BTDR-2 brick, and that’s something that’s just a part of the brick. You can’t dial it out (but apparently you can drill it out). But, it sounds pretty cool and adds a nice extra layer of complexity in the background. So if you like modulated reverb, you definitely want to build one of these.

Download the Box of Hall Reverb file pack, which contains schematic and layout images, as well as Eagle CAD files (suitable for editing or ordering PCBs directly).

Here’s a demo of the Box of Hall Reverb done by some other guy:

Effects Projects

February 23, 2023 effdub

SmallBazz – Germanium Bazz Fuss for DIY

I can promise that you haven’t seen this exact circuit configuration in some over-priced boutique pedal. What we have here is my wacko take on the classic Bazz Fuss, a mainstay DIY favorite owing to its low parts count and surprisingly amazing fuzz tone. The original uses a darlington integrated circuit in a transistor-sized package (MPSA13), so I thought I’d spice things up with a discrete darlington arrangement but with germanium transistors instead of silicon. More mojo, amirite? Germanium Bazz Fuss is the coolest.

And to add to the quirkiness of this particular circuit, I decided to go with an oddball transistor: the NPN Germanium 2N1101, which is readily available from Small Bear Electronics. Why this particular part number? Two main reasons: 1) it’s NPN and much easier to deal with in terms of biasing and power supply setup, and 2) I’ve never seen it used in any circuit, and that’s enough for me. Also, it’s cheap and easy to source (at least for now as of 2023). The drawback? It’s not at all a standard package, doesn’t readily fit any existing PCB layouts, and doesn’t exist as a part in any of the common PCB creation applications.

So I created my own part for the 2N1101 in Eagle CAD and set off to create a fun new version of the Bazz Fuss. I added a few extra features: a switch to toggle between two feedback clipping diodes, a gain control, and a bias trimmer to dial in those finicky Germanium transistors. Here’s the schematic:

Once more for the SEO: Germanium Bazz Fuss.

Author: effdub

6P14P versus EL84 Vacuum Tubes: What’s the Difference?