Tube DI Project

[okgb]

I don't know that it would be cool to post the demeter schematic
but i can tell you the first stage is a cathode follower which either
switches to the  [ dbe  ] xfmr for unity or goes through the second
stage of the 12ax7 then a pot for boost to a 12at7 CF stage to the other
half of the switch to boost

 

[Whoops]

12AT7???

they all seem to just use one 12AX7.

 

[Kingston]

Also the lack of an organized and complete tube DI project on prodigy pro led me to post this topic.

What do you mean?

There's close to hundred pages of NYD one bottle info around here. It's a proven design, and exactly as flexible as you decide to build it.
I personally haven't heard a better DI than that.

Could be that the fact that it's a serious DI is buried behind the more prominent fact that it's an even better pre-amp. Off the shelf parts, with a cheap tube (12AV7), lots of transformer choice (a one bottle DI could go transformer-less as well).

Or you could do MILA-1. or the two bottle. I'm a big fan of these NYD designs for their simplicity and flexibility.

 

[Whoops]

thanks for the info,

can you provide some links?

 

[Kingston]

using the search above "one bottle" gave me this as the first hit http://www.groupdiy.com/index.php?topic=6711.0

the thread is long, but so is the list of tips and modifications ideas. Some of the stuff has been removed during the years, but if it's not there anymore, you can get the standard I/O (as in DI, trafo, trafo-less, balanced/unbalanced) and PSU choices from other similar designs.

 

[Whoops]

cheers,
will do some research on the "one bottle" .

 

[okgb]

i emailed the article to you  , if you can post it for everyone else

 

[Whoops]

Thanks,
will do that as soon as possible.

it's really kind of you.

 

[Nikolay]

Hi guys, I draw the schematics from Whoops's pictures
I can't read the value of resistors and big blue caps.

If Whoops can give me a better high quality pictures I will draw all the schem including PSU.

 

[[silent:arts]]

someone mailed me the following yesterday:
http://www.silentarts.de/DIY/temp/BuildingATubeDI_001.jpg
http://www.silentarts.de/DIY/temp/BuildingATubeDI_002.jpg
http://www.silentarts.de/DIY/temp/BuildingATubeDI_003.jpg

 

[okgb]

I'ver built that one , it's decent unity gain cathode follower
i added a switch to make it passive without the tube
in case of power problems or preference .
Good beginner one as it talks you through it .

the agular looks a little different , like a white  , totem pole
follower ?

 

[Whoops]

Hi sorry for replying sooner.
have been really busy finishing and album , and with Christmas time it got even worse.

Here is the excellent Canadian Musician Article with better quality files.
Thanks a lot Greg for scanning and sending it to me.

http://twin-x.com/groupdiy/albums/userpics/Buffered_Tube_DI_r.jpg
http://twin-x.com/groupdiy/albums/userpics/Buffered_Tube_DI_2_r.jpg

PDF (save target as):

http://twin-x.com/groupdiy/displayimage.php?pos=-2874

Schematic:

http://twin-x.com/groupdiy/albums/userpics/Tube_DI_Schematic_r.jpg

 

[Whoops]

Tube Buffered DI  from Canadian Musician Magazine

 

[Whoops]

If Whoops can give me a better high quality pictures I will draw all the schem including PSU.

Hi Nikolay,
thanks a lot for making an effort to design the Schematic.
I still don't have the knowledge to do that. Specially the tube part.

I uploaded all the pictures I have with better resolution to my gallery in twinx:

http://twin-x.com/groupdiy/displayimage.php?album=lastup&cat=10263&pos=0


There's more pictures on this link,
and also an handwritten Demeter schematic:

http://www.twin-x.com/groupdiy/displayimage.php?album=161&pos=3

Although in the Demeter inside photo I only see 1 tube and not 2.
maybe it's a different model

 

[Whoops]

I made a Diagram of the PCB,
with the capacitor codes, and the possible values for the resistors.

 

[Whoops]

Jensen Transformer wires:

Yellow - Tip Jack Out

Orange , Black, Grey - Sleeve jack out

Red - Pin2 XLR

Brown - Pin3 XLR

White - not connected

 

[Nikolay]

Here we are
I draw the complete schematics, but I'm not sure about some resistor values. I draw it as I think.

I can't read correctly the resistor color codes.
Whoops, may you write a resistor color codes using your cketch? All elements numbering is taken from your chatch.

I think, that R2 and R4 are 470ohm, R3- 56k, but I'm not sure about R1 and R5. I think that they are 100k or 1Meg, but 100k is too small value there.


R11 is connected over the output jack,

Resistors at the anode power supply are not correct. I can't read it.
C6 and R10 are soldered together at the PSU board, C6 is the big orange cap.

 

[okgb]

the Demeter rack mount has two tubes , maybe the
box model uses just the one  , note too that the boost function
likely inverts the polarity of the signal if the tube half in being switched,
otherwise  [ as maybe the case in the box model ] a resister
and not the tube half is switched for the boost function .
[ still unsure about letting that schemo into the general public ,
anyone want to ask demeter ? ]

 

[Whoops]

Edited my post, the Demeter schematic was removed.

 

[Whoops]

R1 and R5 are 1.01M (from measuring them in the unit) although the colour codes indicate for a 2,01m value (Red,Black, Brown,yellow, Red)

I'm pretty sure that R11 is 75r. (Violet, green, black, gold, red)

The other resistors I measured them when I took the photos I found the notes today.
I also measured some voltages at that time.

There's a capacitor connecting the chassis XLR pin to ground.

here is the revised PCB diagram