VBITNGC building & comment

[digi01]

dear all,
the thread is starting for vgitngc project assembly & developent.

project antetype below:
T-network: the better feedback solution?
Projects for next hollidays (the world smallest VBITNGC??)
pcb boards set group order below:
VBITNGC group buy

Zang

 

[digi01]

step by step assembly with photos.
the vbitngc has 3 units.the first assembly is tube buffer unit.

Part list below:
Tube PCB *1
E88CC*1
10K 2W*2
3.3K 0.4W*2
1uf 200V mkp *2 *
the sch of tube buffer and amp

**
the tube that I used is 6922.the coupling caps is 2 ero 0.47uf160v connected in parallel per channel.

the source of suitable tube sockets:
http://www.diyaudio.com/forums/showthread.php?postid=758149#post758149
http://www.diyaudio.com/forums/showthread.php?postid=758154#post758154
thanks dave

 

[digi01]

the connection wires(from psu to amp) should be get ready now.there are 9 wires,I think the length 150(mm)-300(mm) is pretty.
the high current wires(3) is 1.2mm diameter.the others are 0.6mm diameter.I use the teflon cable.

 

[digi01]

buffer with cables.

 

[digi01]

the coupling caps sets up at the bottom of pcb.
OK,then the tube buffer is completed!

Zang

 

[digi01]

the second assembly is amp unit.
The parts for the amps board were printed by their value on the boards.
Part list below:
AMP PCB *1
LM3875TF *2
50K log Poti stereo *1
330uF / 35V low ESR *4
180R 0.4W 1% *2
18K 0.4W 1% *6
47K 0.4W 1% *2

**
the bypass caps that I used is Fc 100uf/35V.

 

[digi01]

the bottom view of amp board,I have not set up the 'T' network.

 

[digi01]

buffer has set up on the amp.

 

[Evilsizer]

looks good digi...got any pics of the housing your going to put it in?

 

[Upupa Epops]

Digi, do you have a submarine ?

 

[digi01]

here is the connections of buffer to amp.

P.S.
to Evilsizer,I have got a small enclosure from franz,will show the completed amp pic soon.

Zang

 

[Franz G]

I am waiting for a cad drawing from my supplier and an offer for ready prepared boxes.

As soon as I get the drawing, I will post it here.

On the other hand, it should be quite easy to build the own case out of two aluminium sheets.

Franz

 

[wim]

Zang, witch of the posted PSU schematics can be used? There are different types on the forum. I assume the one from Franz d.d. 6 oktober 2005 is de right one?

And why in the BOM 2 trafo's from 2x18 VAC?


Can we see pictures from a build PSU too?

 

[Hanzwillem]

There seems to be an error in the silkscreen of the PSU board.

I suspect D1,D2,D3 to be printed the wrong way. I don't see this work as a proper bridge as it is drawn at the moment...

 

[Nordic]

I still can't wait to get my hands on one of these, the only valve driven item I have is an old valve radio my grandfather build. Although I know the valve sound from band equipment like Fender bass amps etc... vely nice

 

[Andypairo]

Got my boards today, they seem to be well done.

Maybe the holes for the tube socket could have been bigger. I had a hard time fitting mine into them.

Will inform of the progress.

Cheers

Andrea

 

[Hanzwillem]

I used a drill to make the them slightly larger. There are more holes which weren't as expected. I had to bend the leads of my Elna duorex to make them fit the PSU board.

 

[wim]

I had the same problems, fitting the tubesocket on the PCB.

Hanzwillem, strange there is no comment on your post about the wrong PS PCB layout. I posted some other questions, but received also no answers.

Are Franz and Zang together on a lazy hollyday😉

 

[Franz G]

Sorry, I spend my weekend with my little daughter. Just in a hurry:

It seems in fact to be a mistake in the silk screen of the psu board. So, think about a correct bridge topology, before you solder the diodes!

I think, "my" schematic and the schematic from Zang are adequate. Two corrections: the filament voltage is +6.3VDC and ground (not -6.3VDC) and the 85VAC are too high to use with 63V electrolytics.

http://www.diyaudio.com/forums/showthread.php?postid=753303#post753303

About the tranny:

You could use one, two or three trannies. Important is to have:

- 2 x 20VAC about 165VA (you are free to do your own gain calculation, depending on the available tranny as mentionned in the LM3875 datasheet)
- 6 to 8VAC 10VA (filament 6.3VDC and NE555/relay circuit)
- 35 to 45VAC 5VA min (anode voltage)

Franz

BTW:
Nice PSU simulation, to simulate the available trannies: Search for Duncans Amp Tools, PSU simulator. It is free.

 

[wim]

Thanks a lot for your answers Franz!