[6BQ5]

I've read various places that the Russion 6P15P-EV tube is an acceptable substitute for an EL84. Frankly, I never thought to bother rolling with other tubes with my RM10. The RM10, as with all of RMs products, is thought-out and optimized to the Nth degree.

However, I came across this article today, which desribes a new way to use the Russian tube in a circuit by Steve Deckert of Decware.

Quite intriguing - particularly in regards to the supposed performance improvement in using it this way. Curious if anyone who knows their tubes (yes, that obviously includes RM) as to what do they think of what is being suggested here:

http://www.decware.com/newsite/paper145.htm

Would this also apply to EL84s?

[JakeJ]

Hi 6BQ5,

Having looked up a couple of tube data sheets for the EL84 the diagram shows that Grid 3 (Suppressor) is internally connected to the cathode (pin 3) so it's not quite the same application of either the 6P15P-EV or the EL34.  However the 6P15 is internally connected to the cathode and thus very similar to the EL84.  All voltages and current ratings are also very similar.

So then the question remains if the 6P15P-EV can be used in the RM-10 if it is connected in the manner Steve Deckert outlines in his white paper?  I think that's a question only Roger can answer.

Well if that doesn't help, it's sure to confuse. 

BR,
JakeJ

[doug s.]

it's the 6p14p that is the el84 equivalent.  (actually, it is the 7189 equivalent - higher woltage rating than the el84.)  from what i understand, the 6p14p-er is the best iteration - rated at +10,000 hours.  there is a standard 6p14p iteration, and a 6p14p-eb/ev, rated at +5k hours.  i was gonna try some, but i found four nos tung-sol 7189's for $50, so i got those instead.  but, everyone i have ever heard from on the web says the 6p14p's are fantastic tubes, w/some saying they riwal the best 7189/el84 around; and they are cheap - you can typically find the +10k iterations on ebay for ~$60-$65 shipped for eight tubes.

http://shop.ebay.com/i.html?_nkw=6p14p&_sacat=0&_trksid=p3286.m270.l1313&_dmpt=Vintage_Electronics_R2&_odkw=6p14p-eb&_osacat=0

i may still try some yet - these are cheap tubes.  and, my amp that uses these typically is on 120 hours/week...  so, 7189's and other tubes rated at +10k hours are right up my alley...

doug s.

[6BQ5]

I've seen references to the 14P being a closer equivalent, but the 15P also working in EL84/6BQ5 circuits.

However, I'm still curious as to whether the manner of hook-up described by Steve Deckert (above link) would work on an EL84/6BQ5.

[rwdrey]

The 6p14pev is a drop in replacement for the EL84/7189, the 6p15pev is not(but close). I own a Decware SE84C & prefer the 6p15pev. The 6p14pev is a great sounding affordable tube, the 6p15pev is a better sounding(in the SE84C) and cheaper tube. Don't know the RM10(sorry!), ask the manufacturer if you can use the 6p15ev. If the RM10  runs the output tubes as pentodes it might be a possibility. You will love this tube.

[doug s.]

I've seen references to the 14P being a closer equivalent, but the 15P also working in EL84/6BQ5 circuits.

However, I'm still curious as to whether the manner of hook-up described by Steve Deckert (above link) would work on an EL84/6BQ5.

it seems this mod would be the same for the 14p as for the 15p, as they both have pin 3 connecting g3 suppressor grid and cathode.  but, what i don't get is if the g3 suppressor grid and the cathode are connected internally within the tube , how do you disable this connection, and replace it w/a cap?   

doug s.

[doug s.]

The 6p14pev is a drop in replacement for the EL84/7189, the 6p15pev is not(but close). I own a Decware SE84C & prefer the 6p15pev. The 6p14pev is a great sounding affordable tube, the 6p15pev is a better sounding(in the SE84C) and cheaper tube. Don't know the RM10(sorry!), ask the manufacturer if you can use the 6p15ev. If the RM10  runs the output tubes as pentodes it might be a possibility. You will love this tube.

from what i can determine, the 6p14 & the 6p15 have identical pin-outs, but slightly different ratings.  the main difference being:

"The SV83 (6p15) can get only 200V on the G2 with 1.5W max dissipation, not 300V/2W as the standard EL84"

this info was further clarified with this:

"A 6P15P can take up to 330V on G2 but 1.5W screen grid dissipation still holds.
If you want to stay within 1.5W G2 dissipation you must not use more than 200V.
In fact there are no curves for Vg2 higher than 200V, exactly for the above reason."

from: http://www.diyaudio.com/forums/archive/index.php/t-137330.html

in this link, they reference another thread about these two tubes:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=94949

doug s.

[6BQ5]

ask the manufacturer if you can use the 6p15ev.

    Ritchie ... This is the Music Reference forum where Roger Modjeski who designed the RM-10 amp hangs out ... he would know.

Anyways, I'm wondering if an EL84/6BQ5 can be hooked up this way Steve Deckert is suggesting and would there indeed be an improvement. The EL84/6BQ5 are (by my understanding) used in a rather unique way in the RM10.

dougs ... thanks for the links. While reading through, came across the specs here:
http://www.klausmobile.narod.ru/testerfiles/6p15p.htm

Indeed, quite an interesting tube and still relatively cheap. Those NOS Mullards and Amperex EL84s have gotten scarce and expensive, not that I have tried them though, I use the stock RAM Labs tubes provided with my amp (which I think are re-labeled Sovtek's).

[seavan]

Trying to revive the thread. It seems that its original question has not been resolved.

I am very curious if anybody tried the Steve Deckert's mod with RM-10, or if it's possible to use 6p15p-ev in RM-10, assuming that the supressor grid is taken care of.

Thank you!

[Ericus Rex]

You should call Roger.  And ask the question about the tube before you ask the question about the modification.   

[ZENTISH]

The mod that you are referencing only works on the EL34 and 6p15p-ev (sv83), it will do nothing for a 6p14p-ev or El84/6BQ5.
Tish

[seavan]

ZENTISH, yes, it only works on 6p15p-ev and EL34 and I am wondering if I can try it with RM-10. I really hope that Roger or someone else can help with that.

[Roger A. Modjeski]

I've read various places that the Russion 6P15P-EV tube is an acceptable substitute for an EL84. Frankly, I never thought to bother rolling with other tubes with my RM10. The RM10, as with all of RMs products, is thought-out and optimized to the Nth degree.

However, I came across this article today, which desribes a new way to use the Russian tube in a circuit by Steve Deckert of Decware.

Quite intriguing - particularly in regards to the supposed performance improvement in using it this way. Curious if anyone who knows their tubes (yes, that obviously includes RM) as to what do they think of what is being suggested here:

http://www.decware.com/newsite/paper145.htm

Would this also apply to EL84s?

In a quick view of my Russian Data Book I find that the 6P15 is not at all close to a EL84/6BQ5 though the 6P14 appears to be (at first glace). The 6P15 is a high gm, high mu video amplifier not an audio output tube and will not bias up the same in any EL84 circuit I can imagine.  Let me know if you find out otherwise.

The Decware mod concerns tieing the suppressor grid to ground via a capacitor and letting it float DC. He gives some data on the voltages which are so small that I hardly think anything audible will be heard. I don't like floating the grid as its DC voltage will be undetermined and thus its ability to do its job. The suppressor grid collects electrons that bounce off the plate and it needs a path to ground to deposit them. The Decware mod provides no such path.

As to using the  6P14 as a substitute for the EL-84 it seems ok as long as you can properly bias it. However keep in mind the RM-10 runs the plates close to 700 volts in a unique application. I have not tried this tube and therefore cannot say if it is a safe in my application.

[Roger A. Modjeski]

    Ritchie ... This is the Music Reference forum where Roger Modjeski who designed the RM-10 amp hangs out ... he would know.

Anyways, I'm wondering if an EL84/6BQ5 can be hooked up this way Steve Deckert is suggesting and would there indeed be an improvement. The EL84/6BQ5 are (by my understanding) used in a rather unique way in the RM10.

dougs ... thanks for the links. While reading through, came across the specs here:
http://www.klausmobile.narod.ru/testerfiles/6p15p.htm

Indeed, quite an interesting tube and still relatively cheap. Those NOS Mullards and Amperex EL84s have gotten scarce and expensive, not that I have tried them though, I use the stock RAM Labs tubes provided with my amp (which I think are re-labeled Sovtek's).

I looked at the klausmobile link above and several things disturb me. First all his pentode curves are taken at very low screen voltages, the highest being 75 volts. In the RM-10 and most applications the screen grid is operated around 300 volts.

My Russian data book shows the 6P14 and 6P15 being for very different applications and I doubt they would make the tubes so similar in design. Video output tubes can be used for audio output, the 6CL6 being a good example. However, the voltages are quite different.

Looking at the last graph at http://www.klausmobile.narod.ru/testerfiles/6p15p.htm where he superimposes the 6P15 curves on the EL34 curves I think he has made a mistake. The 6P15 is so different that I cannot believe this. The Russian data book states the 6P15 mu is 25 as a triode and the 6P14 (from my measurements) always comes out around 16. This means the screen grids are quite different and a large adjustment in either bias or screen voltage will be needed. Also the gm of the tubes is different the 6P15 rated at 15 mA/V and the 6P14 at 11 mA/V. One has to be careful with these numbers as they are dependent on operating point. I still think these tubes are quite different.

Is there any better information out there? Seems to be a topic of interest from the number of replies. I'm too busy with the OTL amps right now to get into it too much.