A forgotten Russian pentode
There’s not much information around the 6Ж49П-ДР or 6Z49P-DR / 6J49P-DR pentode. This pentode was designed for high-frequency operation and durability. It has relatively high transconductance and high mu when is triode connected. Hence, an interesting device for a phono stage given the low capacitances in place as well. The 6Z49P is close to his brothers 6Z51P and the famous 6Z52P albeit it has different characteristics.
I handpicked a sample from my stash which was close to the data sheet specs:
From the data sheet transfer curve above we can see that a test point can be chosen easily here:
- Ua=150V
- Ug2=150V
- Ug3=0V
- Ug1=-1V
- Ia = 22mA
- Is=4mA
- Gm=30mA/V
The device under test here measures very close to spec, however it has a lower transconductance, nearly 55% less. If you look at the data sheet, you will notice that the transconductance at this point flats out, so it may explain the difference due to saturation effect:
It is interesting to see that anode resistance is about 60-65kΩ at this point. This info is not available in the data sheet.
Now if we trace this valve in triode mode, here is what we get:
The triode curves look very linear at first glance. Also the mu is high (about 50) and the anode resistance is around 3.5kΩ. Below is the Spice model fit:
The Spice model can be found here: 6Z49P-DR triode model. The capacitances aren’t correct as I couldn’t measure them in triode mode given lack of time. The model is pretty accurate in my view.
Now, what about the pentode Spice model?
I had to remove some data sets above due to the saturation effects. However, the model is accurate within the area of normal operation. Here is the pentode Spice model: 6Z49P-DR-PENTODE-VS150V.cir.
I’m sure this is a nice candidate to play around. Keen to read your experience with this valve if you have listened to it. Please send me your feedback if you can.
Ale
Well, one more to the high mu pentodes strapped as triode :
E180F 50 Sound pretty
E280F 55 Sound pretty
EF184 50 so so
6e5p 30 the best, need preamp )-: no enough gain
6z51p 80 ( tube for me the sound is a little hard )
Hi Javier. Yes, I’ve tried them as well and used extensively the 6e5p/6e6p. Also traced curved so check out the blog. The E280F is also nice.
Haven’t heard the 6j51p/6z51p yet so can’t comment.
Thanks for sharing your views!
Ale
Hi Javier,
You forgot the most used (trioded) pentode, the D3a.
If I want more “rock”, I use D3a, else usually listen E280F sophisticated sound (in my trioded pentode, source follower, 300B SE).
The “german line” also strong: C3m, C3g.
I made -at request of my friend- 300B SE with gyrator loaded C3g with beautiful sound.
Don’t forget the most popular russian high gm pentode: 6S45P.
Oops, 6S45P is a real triode. 🙁
But I love it. 🙂
Hi Bela
You’re 100% right!. I love all of them: 6C45P, C3g and D3a. I don’t have a big stock of D3a unfortunately so I ended up procuring a big lot of 6Z52P which is close to it.
Cheers,
Ale
D3a maybe is one of the best but prices similar to gold 🙁 as reasonable price the E280F/E180F is real driver to 300b or 211tube, with CCS low Z have only a hundreds Ohm Ri ( gyrator for next time) but the Russian tubes are a very good alternative to expensive occidental NOS.