12B4 & 1626 tubes - similarities

sweet & juicy SE amp for 1626 Darlings and the 6L6 family

12B4 & 1626 tubes - similarities

Postby Ludwig » Mon Apr 06, 2015 5:40 pm

I'm currently building both the budgie preamp and the clementine and noticed that the 12B4 and 1626 tubes are in fact quite similar.
The 12B4 would probably work instead of the 1626, and even give a bit more juice. Has anyone ever tried this - providing a suitable adapter was available of course?
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Re: 12B4 & 1626 tubes - similarities

Postby EWBrown » Tue Apr 07, 2015 6:15 pm

This Is a posting about this very subject, I made back in December 2013:


For what it is worth, 12B4As can be used in the Clementine / Darling circuit, with no resistor value changes.
12B4A is a noval 9 pin miniature, so it cannot just be plugged directly into an existing Clem.
With 250VDC B+ and 1K cathode resistor, it also draws 25 to 27 mA, with a 5K OPT, it delivers 1.5W rms.

It would not be difficult to wire up a pair of octal to 9 pin adapters, in order to make 12B4As work in the octal sockets.

One of my near-future projects will be to add the two 9 pin tube sockets to an existing Clementine,
or point to point Darling, and wire them up pin parallel with the 1626, and make it be convertible for either tube type.

/ed B

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The 1626s will produce about 750 mW per channel, the 12B4As, 1.5WPC.
Last edited by EWBrown on Mon Apr 13, 2015 11:59 am, edited 1 time in total.
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Re: 12B4 & 1626 tubes - similarities

Postby Ludwig » Tue Apr 07, 2015 8:07 pm

Brilliant!
I have 12AU7->6SN7 and 6DJ8->6SN7 adapters, but the pinouts of 12B4/1626 appear to be different....any ideas where we could find a commercially made adapter?
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Re: 12B4 & 1626 tubes - similarities

Postby EWBrown » Wed Apr 08, 2015 8:22 am

It is very unlikely that a specific 12B4A to 1626 adapter has ever been commercially produced, this would have to be a DIY project,
perhaps modifying an existing novar to octal base adapter.
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Re: 12B4 & 1626 tubes - similarities

Postby zippy1540 » Fri Apr 10, 2015 8:21 am

I have built an adapter to put 12B4 tubes into a clementine. It worked perfectly. As for the sound it was noticeably fuller in the low frequencies while still being detailed and clean. Great imaging and clarity. The 1626 really shined on the mid range. Both tubes had a great top end response. Compared to the 1626 it would come down to what's in the rest of your system. I tried switching back and forth on several systems and both tubes sounded incredible but had slight differences. Making adapters is easy enough and they are direct plugins so it's definitely worth trying out to see what matches your system and listening tastes.
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Re: 12B4 & 1626 tubes - similarities

Postby justinsweber » Fri Apr 10, 2015 11:43 am

Id love more info on these adamptor... can you share a bit more?


Thank you
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Re: 12B4 & 1626 tubes - similarities

Postby zippy1540 » Sat Apr 11, 2015 5:26 pm

I used some dead metal based octal tubes, removed the glass and guts, wired up some 9 pin ceramic sockets and pulled through the octal pins, resoldered, tested, then filled with 5 minute epoxy. made for pretty solid adapters. Just make sure you wire up the pins correctly. plate to plate, grid to grid, cathode to cathode and the heaters. if you are careful you can remove the metal ring and test before adding the epoxy. made for some really pro looking adapters for a few bucks.
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Re: 12B4 & 1626 tubes - similarities

Postby Ludwig » Sat Apr 11, 2015 5:38 pm

Makes me wonder whether we could try 1626 tubes on the Budgie preamp?!
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Re: 12B4 & 1626 tubes - similarities

Postby zippy1540 » Thu Apr 16, 2015 1:04 pm

Interesting thought, I have some spare 1626 tubes, i might give that a try. Shannon, any reason it wouldn't work other than providing 12V for the heater?
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Re: 12B4 & 1626 tubes - similarities

Postby Ludwig » Sun Jun 14, 2015 3:49 pm

Hi all - it seems there is a commercially made adapter on fleabay now;
http://www.ebay.com.au/itm/1x-1626-to-1 ... 4638b5811c
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Re: 12B4 & 1626 tubes - similarities

Postby zippy1540 » Sun Jun 14, 2015 8:16 pm

$36.50! Holy hell they are really proud of those, Easily made from an old octal tube and a 9 pin socket, cost me somewhere around $6 to make one including the tube of 5 min epoxy i used to fill the gap
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Re: 12B4 & 1626 tubes - similarities

Postby Ludwig » Tue Jul 07, 2015 6:33 pm

Whilst we're on the topic of similar tubes, how about the 12A4 as one which might in fact give a bit more gain than even the 12B4?

http://frank.pocnet.net/sheets/127/1/12A4.pdf
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Re: 12B4 & 1626 tubes - similarities

Postby EWBrown » Tue Jul 07, 2015 7:15 pm

The 12A4 would require a higher OPT impedance, in the range of 10 to12 K, and lower cathode resistor, probably around 500 to 600 ohms. Higher voltage gain,
but no higher output power. Probably quite similar to half of a 6BL7, or a 6S4A.

/edB
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Re: 12B4 & 1626 tubes - similarities

Postby Ludwig » Fri Jul 10, 2015 8:40 pm

EWBrown wrote:Probably quite similar to half of a 6BL7, or a 6S4A.
/edB


Funny you should mention the 6S4A, I bought some of those a few years ago on a whim without any idea as to what they'd be useful for, have you ever built an amplifier with them? What circuit did you use?

Mine are RCA, look to be NOS, nice little bottles!
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Re: 12B4 & 1626 tubes - similarities

Postby soundbrigade » Wed Nov 18, 2015 12:03 pm

A) I have to check the existence of 12B4A in my tubotek. As I appearantly haven't succeeeded with my first Darling (based on some original non-diytube schematics), I am tempted to try the diytube's schematic but using 12B4A.
However, I am also very tempted to see how dual triodes like 6AS7G or 5998A could fit this design.
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