"single ic and input trafo preamp"...

[isophase]

hey oragall, how is your preamp doing ? did you get rid of the hum ?
i'm thinking of building this also, but as a quad.
i've have 4 of these nice wilesden/belcler transformers that came from neve modules laying around for a long time now not knowing what to do with them, and i think this is the right project for them
cheers

 

[isophase]

ok i want to start building the PSU, how much VA for a quad (NE5534) with seperate Phantom Power ???
i have an original mnats PSU board left over i want to use for this, and then add a separate power transformer+circuit for phantom power ? or is there a better solution ?

i started gathering the parts, i want to build it on vero board, i'm thinking of using 12 step Lorlin switches for the gain and use the following input irons i have available:
Belclere    TF 10016
Belclere    TF 10015
Willesden  EM 20014
Willesden  EM 20031

these came from neve modules, couldn't find much info about them. i think they can be configured as a 600:2K4 - 1:4 ratio 1:2 ratio.
does anyone have information on these transformers ? can someone help me figure out the right Zobel network for this project ? any thoughts or suggestions greatly appreciated !
thank you!

 

 

[gyraf]

1:2 is 600:2K4 - 1:4 is 600:10K

Jakob E.

 

[nielsk]

10015 is a mic input, roughly equivalent to 31267, 10016 is line input, as in 14068. 10014 is somewhere in-between the two. I have no info on the 20031.

 

[isophase]

oops,
thank you for your help,
i thought they had roughly the same specs, i wouldn't want to use a line input transformers as i'm sure the impedance wouldn't be right for my project ?
Nielsk, do you know if the 10015 and 10014 can be configured for a 1:4 step up ?
otherwise will have to rethink my project  :-\

 

[nielsk]

10015 yes, 10014 I am not sure but I doubt it
The only application I am familiar with using the 10014 is as the input (line level) to a distribution amp.

 

[isophase]

thanks !
ok i'm trying to measure the DC resistance on the transformers and see if they match, seems like the windings of the secondary are not symmetrical, i get different resistance values...
do you know the correct pinout ?? thanks a lot

 

[oragall]

after while without post finally end the project.!! the sound its exelent a great clear sound and the noise its minimun.
The problen now its the frequency response, have a " low cut by 125hrz...
which is the problem? maybe the trafo??? :S

attached a picture to compare.

 

[pablobolche]

Orgall,

saludos.. pareciera que podrias probar con distintos valores para el condensador del zobel network.
Tengo algunos trafos si quisieras probar con alguno maname un correo y conversamos.. soy de santiago.

Suerte

 

[isophase]

after while without post finally end the project.!! the sound its exelent a great clear sound and the noise its minimun.
The problen now its the frequency response, have a " low cut by 125hrz...
which is the problem? maybe the trafo??? :S

attached a picture to compare.

hi oragall,
glad your pre is sounding good, i was so busy i havn't had the time to even start mine yet but is part of my plans for this summer
could you fix that low cut problem yet?

 

[EvLoutonian]

ok i want to start building the PSU, how much VA for a quad (NE5534) with seperate Phantom Power ???
i have an original mnats PSU board left over i want to use for this, and then add a separate power transformer+circuit for phantom power ? or is there a better solution ?

i started gathering the parts, i want to build it on vero board, i'm thinking of using 12 step Lorlin switches for the gain and use the following input irons i have available:
Belclere TF 10016
Belclere TF 10015
Willesden EM 20014
Willesden EM 20031

these came from neve modules, couldn't find much info about them. i think they can be configured as a 600:2K4 - 1:4 ratio 1:2 ratio.
does anyone have information on these transformers ? can someone help me figure out the right Zobel network for this project ? any thoughts or suggestions greatly appreciated !
thank you!

Did you ever work out the spec on the EM 20031?

Also, does anyone know- is EM 20015 equiv. to the 10015 transformer ?

 

[Matt Syson]

Noticing the comment about dissimilar resistances of the two 'halves' of the secondary, I think this can be the case on 'single bobbin format transformers where one of the secondaries is wond on top of the other (or the primaries) so that although it will have the same number of turns (same voltage induced) the wire length (and thus resistance) is longer. the twin bobbin design of Lundahl and similar format cores produce winding resistances that are closer matched for resistance.