Input transformer for 1272
« on: June 13, 2020, 06:25:26 AM »
I'm building a clone of the Neve 1272 that I will use to provide makeup gain for a passive summing mixer or to record line level signals into my DAW.

I'm using Carnhill VTB1847 for the output (which I understand is a direct replacement for LO1166) but I'm a bit unsure about what to use for the input. I see a lot of references to VTB9045 but I'm thinking this must be because a lot of folks convert 1272s into mic pres? I guess a 9046 is what I want for line level stuff?

 


ruffrecords

Re: Input transformer for 1272
« Reply #1 on: June 13, 2020, 08:49:29 AM »
For gain make up for a passive mixer you do need a mic input  transformer - the usual 10468 equivalent. You will probably need around 30dB of gain. For line level recording just use one of the passive mixer inputs and short the others.

Cheers

Ian
« Last Edit: June 13, 2020, 04:14:11 PM by ruffrecords »
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Input transformer for 1272
« Reply #2 on: June 13, 2020, 10:53:49 AM »
For gain make up for a passive mixer you do need a mic input  transformer - the usual 10468 equivalent. You will probably need around 30dB of gain. For line level recording just use on of the passive mixer inputs and short the others.

Thanks, VTB4095 it is.

From the information I have gathered so far, it seems the LO1166 was wired in series:series (200:600) in the 1272, providing +4dB gain. I'm not sure how to wire up the input transformer yet, but the VTB4095 will provide somewhere between 0 and +12dB gain, depending on the wiring. Finally, the BA283AM should provide up to +35dB gain according the the old Neve documentation (not including the +4 dB from the input transformer) for a total gain of somewhere between 39 and 51 dB.

Should work  :)


Re: Input transformer for 1272
« Reply #3 on: June 13, 2020, 11:21:18 AM »
According to this post the input transformer should be wired 1:2 or 1:4, so +6 to +12 dB gain. 

ruffrecords

Re: Input transformer for 1272
« Reply #4 on: June 13, 2020, 04:16:10 PM »
According to this post the input transformer should be wired 1:2 or 1:4, so +6 to +12 dB gain.
The 'normal' Neve arrangement for mic inputs was 1:2 for 6dB of gain.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

ruffrecords

Re: Input transformer for 1272
« Reply #5 on: June 13, 2020, 06:03:37 PM »
51dB of gain make up will be plenty for a passive mixer. If you use a pair of 4K7 resistors at the input and a 200 ohm bus slugging resistor that attenuation you get is 48 times or about 34dB. You get nearly 10dB of that from the transformers so the amp only needs to provide about 24dB.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


 

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