Dual La2a - [silent:arts] version

[[silent:arts]]

Support thread @ the mother forum

D-LA2A schematic
D-LA2A ground scheme
wiring the heaters
wiring the Rondo Müller PSU transformer
tube socket modification for 2RU cases

Rx25 (TBD) & Meter callibration by SSLtech
comments about Cx04 & Cx14 (aka Arco caps) by Kingston

US BOM by azone

FINISHED UNITS:

[silent:arts]
waldorfcave
bernbrue
Infernal_Death
ChuckD
ChuckD (Numero deux)
geoff004
inputoutput
stitch-o
tskguy
Holger
stereokillah
USIEL
stereokillah  (Numero deux)
Silvas
crisotop (scroll down thru all those nice builds)
Kingston
alexc
electrisizer
Soeren_DK
horvitz
poctop

[ChuckD]

Here's a link to my on resources on this project.

{removed} by request of Drip
Much respect to drip and all his hard work...
Sorry.


Iron: UTC A10 etc...

T4B : cheapest so far is Drips @ $85USD each. But he was reproducing these himself.


-ChuckD

[ChuckD]

Scroll Down to Drips reply on why he does not offer Kits for these T4Bs
Has to do with the cells and the number of rejects there are when testing.

http://www.prodigy-pro.com/forum/viewto ... c&start=90

[[silent:arts]]

there are a few differences between the Drip and the [silent:arts] LA2A.

first: GROUNDING
on the PCB there are 4 independend Grounds (each side of audio, PWR and the 5V for the true bypass relais)
at least you MUST connect the audio and power grounds to a star point, best is connected to the chassis and the IEC safety earth (that is the way I did it with NO problems). the 5V ground can be jumpered to the PWR ground on the PCB.



the PCB layout for the GND connectors is for this:


since the molex 3way connectors for in and out are directly connected to the channel grounds just wire the XLRs Pin 1 there (no need for a direct "PIN1 to chassis" in this layout)

[[silent:arts]]

the caps I used (and the PCB layout is made for):

ceramic:
C181, C281
C182, C282

silver mica:
C104, C204
C114, C214
C113, C213, C115, C215
C112, C212

poly:
C106, C206, C111, C211
C109, C209
C101, C201
C8 (wrong picture there, spacing is 5mm)
C102, C202, C103, C203
C105, C205

electrolytics
C1, C2, C3, C4, C171, C271, C172, C272, C173, C273, C174, C274
C6, C110, C210
C5

[bernbrue]

Hi,
I made a BOM in Excel for the D-LA2. I´m going to include Volkers ordering links and upload it tonight. I consider to use a beautiful pair of old bakelite meters I´ve got here instead of the VU meters , because I don´t need the output level. Can a 1mA Meter be adapted to be used in the D-LA2? The neon lamps, do they have any special voltage? Looking forward to built this beautiful piece of gear. Thx a lot, Volker, for sharing your design. Chuck, the boards are so nice, can´t wait to get them!
regards
Bernd

[[silent:arts]]

NE2 Neon Lamp
65V - or use a 65V zener diode

[waldorfcave]

muchos gracias

at the end of next week i will phone to rondo mueller for the psu trafos...

i´m very excited for this sexy project

[bernbrue]

Hi,
here is an Excel Partlist and the pcb component placement as pdf. I mailed DRIP, the price for a T4B remake is 90 USD. Will ask him for a price reduction in case we order more than ten.

http://www.twin-x.com/groupdiy/images/thumb_xls.jpg
http://www.twin-x.com/groupdiy/albums/u ... nlayou.pdf

regards
Bernd

[[silent:arts]]

this link for the parts list will work better:
http://www.twin-x.com/groupdiy/albums/u ... nt_Art.xls

[bernbrue]

thx, Volker

[Infernal_Death]

So after receiving the board i am wondering about the transformers. Volker seemed to have used the Sowters. I am sure they are nice but also pretty expensive.
Now i am wondering if you can substitute the 4383 with the Edcor XSM600/10K and the 8940 with the Edcor XSM6K/600 ? Although i just realized that the XSM6K/600 isn't listed on the edcor site anymore, just in the price list i received from TonyDB some time ago so i have to ask if it's even available anymore. Also if it's even a good choice to substitute a 5k/600 with a 6K/500. Don't know how sensitive the circuit is.

The Edcors are supposed to be of good quality and you can get all 4 transformers for the price of 1 sowter so that's definitely attractive. Otherwise i have to postpone this project as i really don't have the money for the sowters right now.

Flo

[bernbrue]

Flo,
was thinking about that as well. The other day I saw the "Tube Recording Channel" from Michaels "Tegeler Audio Manufaktur" using OEP as Input- and Edcor as Output-Transformer. The VK1s were already such expensive that another project with 300 bucks for the transformers only seems hard to afford. I'll try to get the T4b for us, build the pcb and case and wait and see.
regards
Bernd

[[silent:arts]]

you find an interesting read here:
http://www.prodigy-pro.com/forum/viewtopic.php?t=22288

for the Jensen mod they use a 10K:10K at the input ...

[bernbrue]

Hi,
just scored these transformers:



two for the price of one new.
regards
Bernd