Ampex 601 Phantom Addition

[CroyTone Audio]

Hello everyone!

I am currently converting an Ampex 601 into a dual mic pre (putting two units into one unit essentially) and I wanted to figure out how to add a phantom power supply to the circuit. I know there's always just adding another transformer and tapping off of that, but the two preamps already make it fairly tight in there and I'm wondering if there's a more simplified solution using the power supply that already exists in the circuit that would avoid all the extra noise and hassle of a new supply line. I'm attaching a photo of the schem with the signal path of the unit highlighted.

I would appreciate any help you all would be willing to give!

 

[FarisElek]

This thread covers this pretty well:

https://groupdiy.com/threads/phantom-v-from-heathers-or-b-opinions.50061/

 

[k brown]

Another option often overlooked, and the cleanest you can get - 5 rechargable lithium polymer 9v batteries. The majority of mics don't actually require a full 48v.

 

[ComodoComplex]

I implemented this in two ways and the second is my favorite:

1) simple Zener-referenced pass-transistor circuit from the B+. Cons are it is wasteful and a bit hot to dissipate 300ish volts at 20-40mA depending on how much current you need for your phantom mics.

2) use a backwards 120vac:10Vac transformer off the 5V winding (while switching to solid state rectification) to get around 90V and regulate down with a standard high voltage regulator. You can use a pretty low VA transformer so it’s not too bad especially if you pull the no longer needed bias oscillator doo-dads

Hope this helps,
Ben