Building a better monster (1272 using 1290 Boards)

[3nity]

like a year ago and idea of building a 1272 cross my mind.
However theres no 1272 project pcb available, then i thought it could be done using Martin 1290 board.
Lets take a look at how it went.

Front panel from Dan DDT, unknown input transformers, Martin 1290 pcb, EA 1066 output.
Crappy recycled case and some aluminium, psu is external recycled from another project too.

 

[3nity]

top

 

[3nity]

another from top.

 

[Mr.GrinchSD]

LOOKS GOOD MAN

 

[3nity]

Thanks Grinch.
It sounds good too..although i havent used it a lot since my studio has been in constant change lately.
However i got to install a zobel and minor touch ups!

Good luck.

 

[MicDaddy]

Hi 3nity,  Why did you chose to not take advantage of the full glory of this pcb?

 

[3nity]

I already have a pair of 1290s.
And since the most expensive part was the output wich i already had....
no expensive grayhills or carnhills....

BTW the DI on this is mind blasting.

 

[MicDaddy]

8) Can appreciate that, would you care to show the routing for that switching 1/4" jack?

I'm trying to follow the wiring but I can't from the picture.  I want to add this switching to my 1290s is it just a matter of putting the jack between the input iron and the pcb? 

Thanks 3nity

Besides not having as much gain, are there any differences sonically without the extra gain stage?  Do you miss the stepped gain switch?

 

[3nity]

1/4 jack breaks the input transformer signal when connector is in....
yes is just a matter of putting the jack between the input iron and the pcb.
I cant comment on sound as my 1290 has cinemag iron, this has EA1166 and uknown input...
But you know it sounds exotic...compared to my 002R.

And yes i miss a gain switch.. might build something like a 12 position lorling..for 5K attenuation.
Hope it helps.

 

[3nity]

Forgot to mention:
All transistors are MPSA-18...they work more than fine...you just turn them 90 dgrees.
2N3055 is NOS stock i got from Apex jr...nice stuff.

Thanks.

 

[Mr.GrinchSD]

It cool to see some one SWITCH it up a bit MUCH props!!! How did you figure out how to wire that output transformer thats insaine you must know alot about this sutff.

 

[3nity]

wiring the output was easy just follow the spec sheet.
inputs were harder...however witha scope and signal gen. it goes better.

 

[madriaanse]

Forgot to mention:
All transistors are MPSA-18...they work more than fine...you just turn them 90 dgrees.
2N3055 is NOS stock i got from Apex jr...nice stuff.

Thanks.

Ha! I got a kick out of this project! Nice work! Did you just hard wire the "gain switch" to the 50dB setting and use the trimmer for gain control?

Regarding MPSA18: I think you meant you soldered them in rotated 180 degrees (backwards) on the bc184c footprint. (not 90deg)

Cheers,

Martin

 

[3nity]

Martin i had those boards for a client who change his mind.

Did you just hard wire the "gain switch" to the 50dB setting and use the trimmer for gain control?

Thats exactly what i did...plus the front panel had a Impedance switch on wich i have a boost wired at T for 45 or 65db.
You are right for the transistors should be 90 degrees.
Thanks for making this boards available.
Good luck