Original Neve 1272 input question. 300 or 1200 ohms

I just connect up an original 1272 module and have a question about the input. It appears that you can connect the transformer in series for 1200 ohm input, or parallel for 300 ohms. I assumed I need 300 ohms so I connected A-B and used it for Hi. And C-D and used it for low.

This works and sounds wonderful, but it seems I can distort the front end of the preamp. So, I am wondering if this is where my problem is. Or maybe its in the amplification stage itself.

I will be ordering one of Daves switches in the near future, but for now I only used a resister in the first stage of 56 ohms. Which is supposed to be about 30db. I left the second stage open for 18db (I think it was). Should these two stages be better matched? I think you can set each stage for very simular outputs. The over all output of the amp is not being overdriven, so I assume its in the first stage or the transformer.

Thanks,

Joe

the trans will be overdriven worse in 1200 mode.

It would be my guess that you are overloading the amplifier, the transformer can take a good degree of level. I used to think those transformers really needed to be padded but Ive definitely come around on that one. The circuit can definitley NOT take a lot of level.

dave

Thanks I will double check my input gain structure.

What is the most common input for these being used for Mic Pres? 300 or 1200 ohms.

Thanks again,

Joe

I would say 1200

Ok, I rewired it to 1200 ohms which was the two coils in series. The output actually seemed lower compared to the 300 ohm connection. That is, with the gain control in the same position, the level seemed a few db lower. No problem though as there is plenty of gain.

What I found out though is that most of distortion is comming from the mic. I can overload the pre with the MXL V69 tube mic if I get to close. I did not notice this before. I will have to try that mic with my API's. But with all the other mics in the studio, I did not overload the input. That mic must be quite a bit hotter. It definely was hotter than any others I had. So there will be a good use for a pad.

I'll have to ask Dave about his GLIDE FADE Switch. I know it has a few positions of pad. But I am not sure it is the same place I need it. Meaning, I need to have gain on the output, but pad the input. I have a feeling his switch in the pad mode, will not have enough gain at the output. Does that make any sense? With the V69, I need to pad before the transformer, but still have control over the gain of the output....

Dave....SoundGuy?


Joe

"my" switch is nothing more than the 1073 switch for only the 283 card. Neve figured out how to properly pad that circuit with those transformers, there's really not a good reason to go reinventing the wheel on the subject unless you want to extract MORE gain from the circuit than they did. Ive certainly never needed any kind of extrnal pad using 1073's and Ive never needed a pad using the switch on my site. The last record I did I used 1272's with that switch for guitars, vocals and drums with no problems, I didnt even build a pad into the box. You dont need one, thats the whole point, its built into the switch.

If you email me your address I'll send you a switch. If you arent going to go with the design that is on Joe Malone's site, you want this. That amp is really picky and the switch jens and I came up with is essentially what Neve designed in order for it to work efficiently.

dave

email sent.

Joe