clintrubber
Well-known member
Arriving at the input-side of an old Ampex-machine, I found transformers in the line-input circuits looking like this:
and wired like this:
So they're making some current through the 25k5 + TX-prim. + 25k5,
transforming that current and then feeding it to a virtual earth
(opamp TL071).
It'll obviously work, and assuming a 1:1 TX-ratio I figure the attenuation
will be (18k/51k) some 9 dB. This input is rated for -24 to +24dBm.
But I've never seen such a topology before.
What would be the idea here ?
Could they be using attenuated mic-TXs here as line-inputs ?!
And what could these TXs be for type ?
Ampex-numbering is 4290942-01 but removing the mu-cap
reveals a round TX with markings Lestronics, Inc., T-2604
/ 4580066-01 (should add a pic).
Thanks,
Peter
and wired like this:
So they're making some current through the 25k5 + TX-prim. + 25k5,
transforming that current and then feeding it to a virtual earth
(opamp TL071).
It'll obviously work, and assuming a 1:1 TX-ratio I figure the attenuation
will be (18k/51k) some 9 dB. This input is rated for -24 to +24dBm.
But I've never seen such a topology before.
What would be the idea here ?
Could they be using attenuated mic-TXs here as line-inputs ?!
And what could these TXs be for type ?
Ampex-numbering is 4290942-01 but removing the mu-cap
reveals a round TX with markings Lestronics, Inc., T-2604
/ 4580066-01 (should add a pic).
Thanks,
Peter