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Author Topic: Is a balanced (differential) Fix possible?  (Read 2315 times)

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Offline Mikey

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Is a balanced (differential) Fix possible?
« on: December 19, 2013, 10:48:20 AM »
I realize that this product is designed to be inserted between a single ended preamp and a single ended amplifier(s).

Can the Fix be modified for use between a balanced preamp and and a balanced amp?
If so, I presume that I will need two kits (one per channel), correct?

Mike
Mike Paschetto

Online Paul Joppa

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Re: Is a balanced (differential) Fix possible?
« Reply #1 on: December 19, 2013, 01:27:59 PM »
A true balanced design might have roughly twice as many parts, but would not consist of two unbalanced units - it would be a different circuit.

First you need to determine what source and load impedances you need it to work with. There are three approaches:

1) one that goes from low impedance to high impedance, like the Fix which iss designed to work with 4K or less source impedance and 100K or greater load impedance.

2) one that works with 600 ohm source and load, the old telephone standard which became the studio standard in the thirties (more or less)

3) one that has a constant impedance so it works with any source or load impedance. These are usually done at either 600 ohms in and out, or 10K ohms. This pretty much requires as many inductors as capacitors, and hence magnetic shielding for the inductors, so it can get expensive quickly.
Paul Joppa

Offline Mikey

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Re: Is a balanced (differential) Fix possible?
« Reply #2 on: December 20, 2013, 04:23:09 AM »
Hi Paul,

I'd be working with a preamp output impedance of 30 (thirty) ohms,
and an amplifier input impedance of around 200K ohms.

So, I think option number 1) would work in this case.

How would the circuit change for balanced operation?
Wouldn't a balanced version of the circuit simply be two single ended circuits 'mirrored' over ground (pin 3)?

Mike
Mike Paschetto

Online Paul Joppa

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Re: Is a balanced (differential) Fix possible?
« Reply #3 on: December 20, 2013, 11:33:05 AM »
A true balanced circuit does not have a ground. At all. Anywhere.

Sorry I had not really given it much thought in the previous post. You can connect the grounds of the two channels to each other and use the L and R hots as + and - balanced. (Don't connect the grounds to anything, the 3rd pin is for a shield not a ground. The input XLR shield connects to the output XLR shield only.) This would convert a stereo FIX to a mono balanced Fix, with a minimum load impedance of 200K.

If you draw out the circuit you will realize there are ways to simplify, but that would be a new design.
Paul Joppa

Offline Doc B.

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Re: Is a balanced (differential) Fix possible?
« Reply #4 on: December 20, 2013, 02:11:25 PM »
I was gonna say you could do it that way, but I usually find out I'm wrong for some obscure reason I didn't think of ;^)>
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline Mikey

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Re: Is a balanced (differential) Fix possible?
« Reply #5 on: December 26, 2013, 08:07:49 AM »
Very good.

Can the baffle width turnover frequencies and magnitude settings be customized?
In other words, is the math that describes the component value selection process included in the manual (like the C4S manual)?

Mike
Mike Paschetto

Online Paul Joppa

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Re: Is a balanced (differential) Fix possible?
« Reply #6 on: December 26, 2013, 11:47:36 AM »
Yes they can be customized. No the math is not included.  :^)
Paul Joppa