Russian 6BQ5 Equivalent or not really

[TomMcNally]

So I needed a set of EL84/6BQ5's for my DIYTube ST-35 ... I ordered a set of Sovteks ... while waiting, a friend mentions that a guy on eBay has quads for $ 18.95. They are bulk (non-boxed) Russian tubes. I get them today, and they are marked 6P18P (the P being the squarish n looking Russian character) My amp wont bias low enough - they want to run at 45 ma or so at the extreme end of the bias pots. Paralleling across the 470 ohm resistor in the bias network takes it the wrong way, so my question is ... what can I do to get these in range? Or should I just wait until the other tubes show up and keep these for something else? I did a search on here and don't see these 6P18P's mentioned, and 90% of the Google hits are people selling them on eBay. Anyone have any experiences ? The three JJ's and an RCA sounded pretty good. Yellow_Light_Colorz_PDT_16

[Shannon Parks]

Supposedly a EL82 clone:
http://www.akh.se/tubes/htm/el82.htm

[EWBrown]

The Russian equivalent of 6BQ5 / EL84 is 6P14P or 6P14P-EV, the latter being the heavy duty milspec version, otherwise the same. I've seen these (and bought them) from e-bay sellers in Ukraine (anthonywest) or Lithuania (kwtubes) for as low $40 for 16, including the shipping, a couple years ago. Out of a group of 16, I Can usually get one close match quad, a "near" quad and a couple of MPs. Once these get the Sovtek, EH or other "brand" name stamped on them, the price gues up by a factor or 2 or 3, at least.

These 6P18P/EL82/6DY5s appear to have lower voltage and power handling capability, so they're basically NG for the ST35, unless the B+ is dropped and the 470 ohm cathode resistors' values may have to be changed. I'd set them aside for a 10-12 WPC HB amp, keep the B+ around 250-275 max, treat them as if they were 6AQ5s, and they should be relatively happy.

Re the cathode resistor, to increase the current, reduce the resistor value, and to reduce the current, increase the resistor value. The net effect is to maintain the tube's ideal G1 to K voltage differential.

/ed B in NH

[TomMcNally]

Thanks for the info Shannon and Ed ... I normally don't buy the cheapest of anything - but I grabbed them on a tip from my friend who spots lots of good deals.

I will add them to the box of tubes awaiting projects, currently full of:

832A - 6GM5 - 1626 - 6AT10 - 6EM7 - 13EM7 Did I forget any ?

... tom

[TomMcNally]

Update ... I emailed the guy and he said he mixed them up,
he's sending the right ones out.

I got a set of Sovteks today and the amp biased up nicely and sounds better than ever !

[Ty_Bower]

Waking up an old thread... I bought a set of eight Russian tubes off eBay recently. The seller had a picture of what was very clearly eight 6P14P-EB tubes. What I received was a single standard grade 6P14P, plus seven 6P14P-K tubes.

Has anyone ever run across the -K flavor? According to a German web site, the -K variety is the designation for "special audio, vibration proof". I wonder if there is anything special about them.

[TerrySmith]

There's also the 6P15P- or SV83, these are great sounding tubes. The only problem is 200v max on the screens so UL or triode connected is not possible.

[paart]

There's also the 6P15P- or SV83, these are great sounding tubes. The only problem is 200v max on the screens so UL or triode connected is not possible.

This brings up an interesting point that I've been pondering for a long time. Whenever pentodes are configured for triode operation the screen is strapped to the plate, either directly or through a small supressor resistor. Does anyone know why this is? What would happen if the screen was simply left unconnected? I can't imagine that an uncharged screen grid would have any significant effect on the electron flow. Anyone ever try this?

[EWBrown]

I've run 6P15Ps in a Decware "Zen" clone, with about 360VDC on the plates, and each channel's SV83 is triode-connected with the G2 connected to the plate with a 1K, 2W resistor, and so far, no blow-ups. The two cathodes share a 150 ohm 5 watt resistor, and they are running a bit "hard" as compared to "normal" 35 mA biasing, these are closer to 50 mA each tube. Yeah, they do got HOT but I've not seen any no red glowing plates or evaporating grids, so far.

DW states that EL84s, 6BQ5s, 6P14Ps, etc can be used with no circuit changes.

The input VA tube is a 6N1P, nothing special, either. This combo gives a nice sounding 2WPC. No real "threat" to a good 2A3 or 6B4G amp, but then the parts are basically dirt cheap. Everything fits comfortably into and onto a hammond 6X10X2 chassis. The rectifier is a Sovtek 5Y3GT.

The DW OPTs are 9600 ohms primary, 6 ohms secondary (40:1 ratio) and are nothing special, just little open-frame "budget" OPTs. Anything in air-gapped SET from 5K to 12K should work just fine...

It turns out that my power trannie (Hammond 272FX) is higher voltage than the original power iron, they used 500VCT or 550 VCT and not the 600V CT that I used, so I am beating these tubes even harder than the original plan called for. I have not tried SV83s / 6P15Ps in UL mode, so that is unexplored territory for me...

Decware's approach was that SV83s are cheap and plentiful, so beating on them like little rented mules isn't such a bad thing after all...

So, while I'm not contesting their G2 voltage ratings, I would presume that the published ratings are VERY conservative, and quite a bit of "liberty" can be taken.

FWIW, the G3 suppressor grid is left "floating" in their design, as it is connected to a separate pin, which is not used in their design. So, in this case, it appears that two "wrongs" can make it "right"... Yellow_Light_Colorz_PDT_06

/ed B in NH