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Balanced to unbalanced board


sbelyo
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21 hours ago, kevin gilmore said:

my balanced/unbalanced/cast to balanced/unbalanced.  but its a pile of transistors, single resistor gain control, and would need a buffer for low impedance loads.

Is that the board that you posted with mention of using it in a modular preamp of sorts?

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  • 2 weeks later...

The most significant issue with the THAT 1200 series of receivers is noise, -107dBu. It is dominated by the rather large values of noise-generating resistors inside (7k typical). With a good discrete design, or clever use of opamps you can get to -120dBu, which challenges measurement (<1uV in a 20kHz bandwidth).

Edited by Craig Sawyers
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He doesn't say what the measurement bandwidth was. Which really makes it a very loose specification. The only hint is the very sharp mains harmonics in the noise plot, which are way sub-Hz in width. To get to -158dBV (-155.8dBu) from -107dBu on a 20kHz B/W you would need a measurement bandwidth of 0.25Hz,

Shockingly badly specified.

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  • 2 months later...
On 10/3/2016 at 9:03 PM, Skooby said:

I've used Jensen transfo for XLR-2-SE.  Not sure it's the best/cheapest method.  May be a step-down transfo's better than 1:1

 

Jensen JT-11P-1 Balanced to Unbalanced Line Level Connections

I think this might be the best solution...  anyone else do this compared to an opamp based solution?

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Any audio signal level transformer has a resonant peak at some frequency, hopefully outside the audio bandwidth, caused by leakage inductance resonating with distributed winding capacitance. The RC network on the output is chosen to damp that resonant peak.

But if you put a cable after it, which has some capacitance, it screws with the damping. The catchall of using less than two feet of cable comes from that consideration.

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