Help lundahl-300bxls problem

[nicoch58]

HI all
my amp http://www.audiodesignguide.com/my/n...ew300bxls.html

with B+ 430v bias -87v I have only 53ma on all two Emissionlab 300bxls not near 100ma ....

look at the opt ll1623 120ma ,the primary is wired as SE, the secondary have the pcb_B
http://www.lundahl.se/pdfs/datash/1620_3_7.pdf
http://www.lundahl.se/pdfs/datash/1620_pcb.pdf

that mean 5.6k on 8ohm 3k on 4 ,my fullrange is 5.5ohm ,what is wrong??

Any expert on lundahl OTP??

Salas (thanks a lot!!) suggestion is that the trafo is config for 3k ie near 2k with my FR ,but for what I have understain this is possible only with PCB_C for secondary setting ..

[nicoch58]

ideal\desired works point

[nicoch58]

actual work point (by Salas )

[disco]

Originally Posted by nicoch46

... with B+ 430v bias -87v I have only 53ma on all two Emissionlab 300bxls not near 100ma

Looking at the graph you need about 450V to obtain 100mA with -87V. At what voltage is the anode?

My 300Bxls uses Kron tubes in a setting like this. Only difference I use a 3K5 OT and they are running 130mA.

Here's another without autobias, running 120mA.

[dsavitsk]

This is a tube/PS issue, not likely a transformer one.

[disco]

Sure and certain.
Use connection 'F' (8 ohm) and raise your supply voltage.

[nicoch58]

Originally Posted by disco

Sure and certain.
Use connection 'F' (8 ohm) and raise your supply voltage.

F ? I don't see

thank for help guys

[nicoch58]

today the main is a bit lower

main 225vac
trafo 325Vac
B+ 421Vdc
V anode 408Vdc

set the bias to -80v with Ia 70ma for now

this suggestion point as I have low b+ can be good ?

[disco]

Originally Posted by nicoch46

today the main is a bit lower

main 225vac
trafo 325Vac
B+ 421Vdc
V anode 408Vdc

set the bias to -80v with Ia 70ma for now

this suggestion point as I have low b+ can be good ?

Emission Labs suggests -74V bias (running 100mA) and 1.5-3K load. The reason might be maximal power or a 'sweet spot'. Aim for this setting to begin with.

Make the secondary connection 'PCB-C' on your LL1623, as outlined in the document. Connecting a 8 ohm speaker presents a load of 3K to your 300Bxls tube and you are in the ballpark.