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 Post subject: 6N28B-V data?
PostPosted: Fri Apr 01, 2011 4:03 am 
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Joined: Fri Mar 19, 2010 8:59 am
Posts: 21
Hi,

I've found mixed data about this subminiature tube. Mine are Novosibirsk (new logo, date stamped 8907)

From what I was able to gather it looks like a good candidate for low anode voltages; are the 50V the "design center" or recommended value, or will it work at higher voltages? I've seen 50V on some places and 150V on others...

I got these with the thought on using these tubes to experiment with low voltage projects like mic/preamp, mini guitar monitor, etc and maybe modifying some commercial DAC I got, from passive I/V stage to active based w/ tube output, either as anode follower or SRPP. Does it looks worth for that from the data? any starting or recommended values?

Which are the maximum ratings/values? (again I found contradictory figures)

Any light or experience shed on this tube will be very appreciated Smile to my noob eyes the (contradictory) specs it looked like a not so usual tube worth looking at.

I've scanned the datasheet that came with the tubes:

Image
Image
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This is what gstube has about them:

Image

More info from Russian tubes


 
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 Post subject: Re: 6N28B-V data?
PostPosted: Fri Apr 01, 2011 9:22 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
6N28B AFAIR is 6N16B redesigned for higher accelerations and vibrations.
6N16B is a miniature version of 6N1P, so maximal power and voltage ratings were reduced due to smaller sizes.
All maximal voltages (anode-cathode, grid-cathode, cathode - heater) are specified 150V, except anode - cathode when the tube is cut off by negative voltage on the 1'st grid that can be 300V.That means, your SRPP can be powered from 300V. I would personally use 200-250V.

Each anode not allowed to dissipate more than 0.9W of power.

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 Post subject: Re: 6N28B-V data?
PostPosted: Mon Apr 04, 2011 1:16 am 
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Joined: Fri Mar 19, 2010 8:59 am
Posts: 21
Smile thats exactly the kind of info I wanted to know.

I also found, googling for 6N28B another forum (gearslutz) thread where you mention it!

I'll try with 200-250V using old transformers cannibalized from 3,7V nokia chargers (ACP-7U) back to back, getting heaters voltage from the two secondaries connected and B+ from the second transformer "inverted" primary.

(I have kind of Diogenes symdrome when it comes to transformers, working as IT head in my company I have saved all cell and other dead equipment chargers and adapters)

These transformers worked fine with 6N1P's giving about 6,4V, though current draw in such case was about 600 mA. Do you think there will be any benefit/drawback from running the 6N28B heaters with DC? given the small heaters current, using DC for heaters won't complicate things too much and would be equally cheap. These transformers are tiny so space won't be a problem either.

Any advised regulation scheme? will a simple 7806 series regulator do or will 6V fall short for heating? Maybe a shunt scheme using a zener?

BTW, some ideas for the GS Wavebourn Mic amp project (I couldn't register): dunno if will be suitable for phantom power as almost all are SMPS type (though not all, but with the advent of VoIP telephony and PoE enabled Switches to reduce clutter, there are tons of Power Over Ethernet adapters intended for VoIP phones for sale.

A rather popular and easily available choke, used mostly in guitar amps (about 4-5 Henries, up to 100mA, about 65 DC Ohms resistance) is the "fender" 125C1A/022699 or 125C3A or 022707 (50mA), available for about $12-$15.


 
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 Post subject: Re: 6N28B-V data?
PostPosted: Mon Apr 04, 2011 7:12 am 
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Joined: Mon Mar 22, 2010 1:10 am
Posts: 238
For the filament supply, 7806 should be enough, but watch the 1Amp limit on these chip regulators. Alternatively you could actually use a 7805 but reference the middle pin to ground via 2x1N4007. (This will give 6.2+/- volts as the voltage across each 4007 will be around 0.6V). doubt if 0.2 volts would make much difference although there may be a drop in emissions at a lower filament temp. I get my 12.6V supply via 7812 with a diode reference as well but I parallel 2x7812 as I need much more than 1Amp for my filaments (4x6N6P)

Hope this helps.


 
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 Post subject: Re: 6N28B-V data?
PostPosted: Mon Apr 04, 2011 4:02 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
Oops... I found datasheets in the network for 6N16B and 6N28B, they show quite different curves. I always assumed that they are electrically equal, but looks like they are not exactly equal.

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 Post subject: Re: 6N28B-V data?
PostPosted: Mon Apr 04, 2011 11:09 pm 
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Joined: Fri Mar 19, 2010 8:59 am
Posts: 21
quickie22, thanks for those great tips!

Anatoliy, do you see similarities with another tube? Do your previous B+/bias points still apply?


 
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 Post subject: Re: 6N28B-V data?
PostPosted: Tue Apr 05, 2011 10:36 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
No, as you may see from curves, they are slightly different. 6Н28Б for 7 mA / 100V needs 3.5V bias, 6Н16Б needs about 2V. 6Н1П needs something like 1.6V.

By the way, I like your idea about 48V supply! Very Happy

I advice you to offer this idea for Gearlutz.

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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