Racking Pres - Need Output Transformer

[Siegfried Meier]

Hey all!

I have a few random console pres to rack - in this case, a few Mitsubishi Westar plugin pres. These are balanced on the inputs, so I just need to find a way to balance the outs. I've done some others, like the Sony MXP3000 racks I've made with electronically balanced PCB's but I was wondering about a transformer that would work in these situations.

Would a Carnhill VTB1148 be possible as an output transformer? I've used lots in my Neve builds, but I'm certain there might be some frequency loss or other odd behaviour because of the preamp circuit...but perhaps not? If it wouldn't work, is there a transformer recommended in these situations, or is just best to stick with balancing boards for this task?

Any help much appreciated!
Thanks,
Sig

 

[pucho812]

How similar are those to the mxp3000 pres?

 

[ruffrecords]

It might be simpler to mod it for impedance balanced outs. No transformer required.

Cheers

IAn

 

[Siegfried Meier]

How similar are those to the mxp3000 pres?

Similar...but different enough...both are cool! I racked many of those, but used the SSL 9k balancer boards on the outputs.

 

[Siegfried Meier]

It might be simpler to mod it for impedance balanced outs. No transformer required.

Cheers

IAn

You're referring to a balancing PCB as I've used before?

Thanks Ian!!
Sig

 

[pucho812]

Any reason you wouldn’t use a that or equivalent balancing line driver?

 

[Siegfried Meier]

Any reason you wouldn’t use a that or equivalent balancing line driver?

That's exactly what I will be using if nothing else - but I just wanted to know if there was a transformer out there that could be used easily.

 

[pucho812]

Would have to see the circuit schematic

 

[Siegfried Meier]

Would have to see the circuit schematic

 

[My3gger]

THAT 1646 would provide balanced output, or drive transformer.

 

[pucho812]

Why do I keep thinking a 1:1 transformer would work fine here and wouldn’t need to be driven?

 

[Siegfried Meier]

THAT 1646 would provide balanced output, or drive transformer.

And what transformer would you use?

 

[My3gger]

Why do I keep thinking a 1:1 transformer would work fine here and wouldn’t need to be driven?

Good question, maybe we didn't know better when SSM2015 THAT replacement preamp IC's came out, or Edcor started selling cheap models that fit already built balanced line driver?
SSM2015 datasheet states 2k oh load minimum for +-12Vout, i calculated 12mA out but don't understand this part in datasheet:
https://www.analog.com/media/en/technical-documentation/obsolete-data-sheets/ssm2015.pdfIt is early morning here, in the afternoon i'm hoping to find a forum where schematic came (post #15):
https://groupdiy.com/threads/simple-cheap-solution-for-driving-a-transformer.27426/Siegfried Meier; we were using Edcor WSM a lot, also API out, Cinemag, can't remember Carnhill from that time.

 

[gyraf]

referring to above schematic: As Ian said: why not just impedance balance it - take a 22R resistor and a 100uF lytic in series, connect to ground, and call this inverting out or cold (XLR Pin3)

 

[My3gger]

Why do I keep thinking a 1:1 transformer would work fine here and wouldn’t need to be driven?

Why do you think it could drive a 1:1 transformer?
Googling didn't help, later i found lots of information on our forum. This thread is a good place to start for those interested in knowing more about (op) amp drive capability:
https://groupdiy.com/threads/driving-step-up-transformer-directly-from-opamp.44520/#post-557516