Pultec transformers

[bram9206]

Hello all,

I'm almost finishing my Cayocosta layout, point to point Pultec clone. I was just about to wire my original Triad HS 56, but I was wondering if I should wire it 600 Ohms or 250 Ohms. For the output stage I used a Sowter replacement and I must say I don't know, according to Cayocosta's layout, what resistance it is wired for.
Anyone any idea what resistance I should choose? I know the original Pultecs are wired 600 Ohms, but is that still in accordance with today's standards...?

Thanks!

 

[CJ]

i think the schemo says 600:600,

250 on the input would be for matching up a low Z device to the input,

most of that 200 ohm stuff is history by now,

 

[telefunk]

Any opinions about using Edcor WSM600:600 and WSM2.4k:10k instead of the Sowters as input and interstage tranfos?

What do you think? Could the lack of shielding in Edcors be a problem in this circuit?

For the output I don't think there is any options for the Sowter...

 

[bram9206]

i think the schemo says 600:600,

250 on the input would be for matching up a low Z device to the input,

most of that 200 ohm stuff is history by now,

Thanks CJ. You mean like all my old mic stuff, like RCA DX77 etc... ;-) So in my case I guesse it would be usefull to make a switch to choose between 250 and 600 Ohms, right? Or would you go for the 600 Ohms anyway?

 

[Biasrocks]

Since your mics will see a pre-amp before a Pultec you'll want to wire it for 600 ohms.

Regards,
Mark

 

[lassoharp]

but I was wondering if I should wire it 600 Ohms or 250 Ohms.

600 ohms is a hard load to drive.  250 is even harder to drive.  Remember that the Pultec input has termination on the secondary so it is presenting a real 600r load (or 250) to whatever is driving it.  I assume you may be thinking in terms of ratios only 1:1 vs 1:2 etc.  I can't think of any good reason to strap the input for 250r.

I know the original Pultecs are wired 600 Ohms, but is that still in accordance with today's standards...?

Most would probably say that today's standards specify a High Impedance bridging input.  The only practical way to get that using an input transformer is to use a 10K or 15K:600.  But the problem there is the loss of gain.

For the output stage I used a Sowter replacement and I must say I don't know, according to Cayocosta's layout, what resistance it is wired for.

The secondary is wired for 600ohm.  Did Sowter send you a schematic for the 9530?  If not, pink & white are the signal, grey & blue/yel are tied as the center tap = 600r.