FX LOOP: Hoffman Fender Blues Junior Conversion

[bakerlite]

https://www.tube-town.net/info/datenblaetter/kits/tt-fxlooplnd150.pdf


I took a chance on this kit but i am not sure where to tap the signal? In between R18 and c8 before the master volume?


does anyone know roughly what VPP this would be as the little board has a low and high input depending on vpp -


Also is Dougs shielded cable ok for the hookup?


Sorry i dont have a schem of this serial loop, it uses lnd150's for recovery.

[tubenit]

That looks like an appropriate insertion place.  Doug's shielded cable should be fine.

It may be possible to have the MV either before or after the FX loop?  A schematic would be helpful if possible. 

with respect, Tubenit

[bakerlite]

The schematic is not available and I am not sure I could accurately pull it from the board.


Before the MV makes more sense in my head as in thats what I wold expect otherwise the MV would have to much effect on the loop if it went after.


So i am thinking after v2b coupling cap.



How does one measure calculate what the  VPP would  be at that point?

[2deaf]

How does one measure calculate what the  VPP would  be at that point?

The signal at C8 is way too big for that LND150 FX Loop.  I don't know what the input impedance is for that device.  Guessing that it is high, a voltage divider like the one attached should work.  Also guessing that it has unity gain into a high-Z load, a 1M Master Volume should work.

[kagliostro]

Ciao 2deaf

Why you short to ground some frequencies using C9 (.001 cap)



Thanks

Franco

[DummyLoad]

Ciao 2deaf

Why you short to ground some frequencies using C9 (.001 cap)



Thanks

Franco

2deaf didn't, fender or doug did that (i have not looked at fender schema). have a look at doug's schematic. replace 2deaf's 47K with 50K pot... same difference.


--pete

[kagliostro]

Ahh .... Thanks Pete

Franco

[bakerlite]

OK it's working! Took the signal between treble and 10k resistor of v2a .
Had to use ears to calibrate as couldn't get the scope to show me what I wanted on the send despite being able to use it else where ... anyway the only issue was hum and interference  which was mostly solved by firstly changing the B+ supply to loop ground from the filters ground and moving it to cathode ground of v2 it helped some.
Then I have had to manafacrure a shield to go between the loop board and the PT due to the ridiculous proximity  of both. 
It's a small shame as without loop you wouldn't know the amp was even on! Now though there is some tiny noise but can live with it.

I only did a mcguiver on the shield (an old laptop ground plate!) If anyone has some handy tips to improve the efficiency  of my shield that would be awesome as I only made it up and grounded it to chassis .
Thanks

[purpletele]

Did you install any of the Billm Mods to your build such as the Presence or clean boost?  What about the tone stack?

Can you send photos of how you are mounting the FX Board.  Just confirmed that my Chassis (multiple) will be done soon so I can start my Blues Junior Build. 

Thanks

BV