How do you add transformers to a solid state passive pultec EQ?

[canidoit]

I have a solid state passive pultec EQ which does not have any transformers, I don't think. How easy would it be to add an input or output transformer?

Is it as simple as inserting from the wiring that goes to the input and output XLR?

 

[CJ]

solid state and passive?  ???

yes, just splice them in but you need different ratios than the tube version, more like 1:2 or 1:4 in, and 4:1 out,

Lange made a solid state pultec, but the Freed transformers are tough to find.

a circuit diagram would help,

 

[canidoit]

solid state and passive?  ???

yes, just splice them in but you need different ratios than the tube version, more like 1:2 or 1:4 in, and 4:1 out,

Lange made a solid state pultec, but the Freed transformers are tough to find.

a circuit diagram would help,

CJ, thanks for the reply.

How about this Input transformer: UTC A-20 transformer: +15dbm, line to line 50/150/250/333/600 ohms impedance both sides.

Will this work? Do I have to grab power from somewhere?

Do you know what wires go where?

 

[CJ]

A20 good , maybe even for output also,

pins 2 and 3 go to the pri,
sec wires go to where 2 and 3 used to go,

still need a schematic to make sure we don't blow anything up,

 

[syn]

UTC A-20 has pinouts printed on its case.

 

[CJ]

depends on the vintage of the a-20,

i was talkin bout the pultec schemo,

 

[okgb]

Yeah , just check the schematics and compare to what you have

 

[CJ]

any snow up there yet?

where is the pultec schemo?

anybody?

 

[canidoit]

any snow up there yet?

where is the pultec schemo?

anybody?

The pultec I have has no schemo. No-one here knows about it??

It's a Lounge Audio PEN-1 SS Passive EQ based on the Pultec EQP-1A but a solid state design. It was made in 2003.

 

[CJ]

it looks like that thing has transformers already,

how do you get power into the box?

1/4 inch jack that supplies DC?

you might want to leave that box alone and build a vacuum tube pultec,

splicing in transformers with those in/out jacks already mounted to the pc board means we have to cut traces and splice wires onto the board,

there is a good chance of messing up the board,

how does that thing sound?

did you get it off evilbay?

 

[Nele]

how do you get power into the box?

wallwart socket on the right?

 

[canidoit]

I wanted to put an 18volt power supply in there. It runs on an 18 volts AC adaptor. So hard to find an AC power supply instead of DC with Australian plug!

It's passive though, so doesn't that mean it does not have transformers?

 

[pucho812]

Whats there website?

 

[canidoit]

Their website does not exist anymore. lounge audio dot com

 

[okgb]

I forget his name , but he was a good guy , i had sent him some schematics in the days when
the pultec schematics weren't common , hope he made out alright

passive as in , any pultec,  where the eq  " network " is a no gain loss type - passive -
  [ which suffers about a 20db gain loss ] and needs an make up gain amplifier after the network
you might want to read up a little on the internet .

In the case of newer versions input transformer = balanced in , which becomes unbalanced feeding the network anyway
and unbalanced in = no transformer .  Yes the transformer is passive , but passive in regards to pultec refers to the filter network
which has no gain or  " Active "  [ requiring power ] components .