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How to make an adapter to use double triode tubes with Little Dot MK II

post #1 of 5
Thread Starter 

This is going to be instructions how to make "THE PRO BOX" adapter to use 6.3v and 12.6v heated double triode tubes with your Little Dot headphone amplifier. This shows how to make adapter to Little Dot MK II. With MK III and MK IV this is not going to as easy.

 

Do not try to do anything like this, if you don't know what you are doing!

 

To do box like this, you need:

Suitable electric box, like Hammond manufacturing 1591MSBK

9pin ON-ON or ON-OFF-ON switch 3PDT

B9A socket

2 B7G tube pin protector/straightener, ebay-seller yitry have these

1mm or 18gauge thick copper wire as pins

Epoxy and gel super glue

 

Tools you need at least:

Drill

Knife

Soldering iron and something to solder with

Multimeter

Cutters

 

Here is how the pins are going to be connected:

 

Left B7G          Box B9A        Right B7G

     5         -         1                

     1         -         2

     2         -         3

     3 via switch to 4

     4 via switch to 5

                          6         -        5

                          7         -        1

                          8         -        2

                          9 comes from the switch

 

Here is the same drawn. And you see how the switch is connected.

1000

 

 

700

Here are the most of things you need to make it. 1mm (18gauge) thick copperwire for the pins what i used was covered with lacquer, so it needed to be removed first by grinding.

 

700

Here are the parts for the pins. B7G socket is just to keep pins more straight when gel super glueing pins through the pin protector/straightener. I grinded wire heads more round.

 

700

Here is the assembly waiting for drying.

 

700

I made holes to bottom of the box. Paper is there protecting little dot from getting any epoxy. You just push pins through the paper. I glued parts together with epoxy. If you do not do this like this way, it is hard to get pins go to you little dot sockets.

 

 

700

This shows the extra wires that are needed with the switch.

 

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And how the switch is connected to the B9A socket. B9A socket is already glued to top of the box.

 

 

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Soldered all the rest wires. Cutted those additional copper wires shorter after taking photo. Make sure all connections are ok with multimeter after closing the box.

 

 

700

And here is the box in use. There needs to be at least 1cm or 3/8in space between box and powertubes.

 

Most of the compatible tubes won't care if the switch is in wrong position, but there is couple 6.3v tubes that could be used in 3.15v heater voltage system with pin9 connected as "ground". So you need to be careful to not burn heaters broken.

 

Adapter like this should work with LD models MK I+, MK II (newest model), MK III and MK IV (+SE).

 

Edit 1: Added shield wiring to diagram for 6DJ8 and 6922 tubes. At least those tubes are going to hum without this connection. You can add ON-OFF switch between this connection too.

 

Edit 2: With MK III or MK IV this not as easy as this.


Edited by Artsi - 11/9/13 at 2:41am
post #2 of 5
Thread Starter 

Here is little list of tubes and variants, that should work now with boxed little dot. List is with heater currents and amplification factors.

 

6V tube types
 
ECC88 6DJ8 6N23P CV5358 M3624        0.35A 33x
E88CC 6922 CCa CV2492 CV2493 9622  0.30A 33x
E188CC 7308 CV4108                         0.35A 33x
E288CC 8223                                    0.47A 25X
ECC85 6AQ8 B719 6L12                      0.44A 57X
ECC86 6GM8 6N27P                           0.30A 14X
ECC189 6ES8                                   0.36A 31X
ECC804 6GA8 6/30L2                         0.30A 18X
ECC812                                          0.44A 50X
ECC865                                          0.44A 58X
ECC180 6BZ7 6BQ7 6BS8 6T27           0.40A 36X
6N2P 6CC41                                    0.34A 100X
6BK7                                              0.45A 40X
6BC8 6BZ8                                      0.40A 35X
PCC88 7DJ8                                     0.30A 33X
6AU7                                              0.30A 20X
6AX7                                              0.30A 100X
6BX8                                              0.40A 25X
6CH7                                              0.40A 36X
6DT8                                              0.30A 60X
 
 
 
12V tube types
 
ECC83 12AX7 B339 95-127-01 6L13 CM1        0.30A 100X
ECC82 12AU7 B329 95-126-01 CC82E CV491  0.30A 17X
ECC81 12AT7 B152 CC81E CV455                 0.30A 60X
E81CC 12AT7WA CV6091 6201                     0.30A 60X
E82CC 6189 M8136 6189W                         0.30A 17X
E83CC 12AX7WA 6057                              0.30A 100X
E180CC CV8431 7062                               0.40A 50X
E181CC                                                  0.40A 32X
ECC186 12AU7WA 7316                              0.30A 17X
ECC802S                                                 0.30A 17X
5751 GL5751 CK5751 CV4017                      0.35A 70X
5814A CK5814-A                                      0.35A 17X
5963 CV3900                                           0.30A 21X
5965 6829                                               0.45A 47X
6679                                                      0.30A 60x
7025                                                      0.30A 100X
12AD7                                                   0.45A 100X
12DF7                                                   0.30A 100X
6680                                                     0.30A 20X
6211                                                     0.30A 27X
12AZ7                                                   0.45A 60X
12AD7                                                   0.45A 100X
12AV7                                                   0.45A 40X
12AY7 6N4P                                           0.30A 40X
12DM7                                                   0.26A 100X
12DF7                                                   0.30A 100X
12DT7                                                   0.30A 100X
12U7                                                     0.30A 20X
6072                                                     0.35A 44X
6681                                                     0.30A 100X

Edited by Artsi - 10/21/13 at 10:57am
post #3 of 5
Quote:
Originally Posted by Artsi View Post
 

To do box like this, you need:

Suitable electric box, like Hammond manufacturing 1591MSBK

9pin ON-ON or ON-OFF-ON switch 3PDT

B9A socket

2 B7G tube pin protector/straightener, ebay-seller yitry have these

1mm or 18gauge thick copper wire as pins

Epoxy and gel super glue

 

 

 

Would this wire be ok to make the pins ? I'm not sure about the quality (Jewelwey wire) and stiffness:

http://www.ebay.com/itm/Solid-Copper-Wire-for-Jewellery-making-hobby-and-craft-work-CHOICE-OF-SIZE-/141085530179?pt=UK_Crafts_JewelleryMaking_GL&var=440187256745&hash=item20d95a5843

post #4 of 5
Thread Starter 

It should work.

post #5 of 5
Thread Starter 

Here is how to connect wires for OCTAL 6SL7GT tube as driver adapter. Remember to think are you looking socket from up or down. Apply this to previous double triode adapter making guide.

 

1000

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