ISA Preamp PCB

[Strawtles]

Hello, someone can help me to find the PCB design of the old Focusrite ISA preamp ?
I know that it is a simple circuit that can be realized with a proto PCB, but i I'd prefer to have a PCB
Kind regards

 

[gyraf]

The ISA is still in production, so I doubt you'll find a ready-made pcb layout.

As you say,  perfboard (veroboard) is an option.

Jakob E.

 

[Strawtles]

I think you are right
Do you know if the one in production is the one realized in the '80 for sir George Martin?
Eventually I can consider to buy a ISA One for my collection ... but I remember to have read that the last productions are different fron the original one, but I am not sure

 

[mista min]

I think you are right
Do you know if the one in production is the one realized in the '80 for sir George Martin?
Eventually I can consider to buy a ISA One for my collection ... but I remember to have read that the last productions are different fron the original one, but I am not sure

The only curent ISA to have the correct input and output transformer is the ISA 430 MK ii.  The new Red preamp also has the input and output circuit and it sounds amazing.

All other ISA's don't have the output transformer and so don't have the soft creamy sound from an original ISA 110 preamp.

 

[Strawtles]

Thank You mista min

 

[Whoops]

I think you are right
Do you know if the one in production is the one realized in the '80 for sir George Martin?
Eventually I can consider to buy a ISA One for my collection ... but I remember to have read that the last productions are different fron the original one, but I am not sure

The only curent ISA to have the correct input and output transformer is the ISA 430 MK ii.  The new Red preamp also has the input and output circuit and it sounds amazing.

All other ISA's don't have the output transformer and so don't have the soft creamy sound from an original ISA 110 preamp.

Hi

What are the correct input and output transformers?

thanks

 

[nille]

https://www.youtube.com/watch?v=Vu_hEdgn8Pw

 

[Fablab]

The input transformer is a Lundahl LL1538
The output one I don't know
The circuit is based around the cheap (but not bad) opamp NE5534 (or NE5532)
Some years ago I realized some preamps with this transformers but instead of the IC I have used the GAR2520 from Classic Api and a Lundahl LL1539 for output
The circuit is the same of API 312 with the zobel network from the ISA
I have not compared these preamps with the Focusrite ISA, but I love how they sound!

 

[gyraf]

The ISA output transformer is a "pumpkin" toroid transformer, also used by some Neve stuff - look at http://groupdiy.com/index.php?topic=12451.0 for approximate type

Jakob E.

 

[Whoops]

The ISA output transformer is a "pumpkin" toroid transformer, also used by some Neve stuff - look at http://groupdiy.com/index.php?topic=12451.0 for approximate type

Jakob E.

Hi Jakob,
thanks for the post.



thanks

 

[gyraf]

That's probably an ISA110 or 115 - PCBs still has room for the edge connectors fitting a neve board...

Jakob E.

 

[peterc]

I have a layout that uses an electronic output stage.

Laid out for Lundahl, OEP or Neutrik mic transformers.

Will post later tonight.

Peter

 

[Fablab]

No news from Peter?

 

[peterc]

Sorry, will get to this.

Peter

 

[Fablab]

 

[Strawtles]

Great!

 

[peterc]

Hi all

I am going to take a bit of time this weekend and clean up this design.

I have 2 designs, one of which uses Lundahl or OEP transformers, and the other which uses a Neutrik transformer.

I suspect the Lundahl/OEP option will be more popular, but I will try and combine the 3 into a single design.

The design uses a 2 pole 12 way Lorlin switch, the same as I have discussed here:

http://groupdiy.com/index.php?topic=59327.msg754889#msg754889

Peter

 

[Fablab]

Thank you Peter!

 

[Whoops]

Hi Peter,
how is your design going?

thanks