Lundahl 1922 tranformer ratio
« on: August 06, 2020, 12:23:34 PM »
I'm using the Lundahl 1922 as an input transformer for a Sta-Level build and I have no idea on transformer ratios. I'm able to use 1:4 or 1:8 ratio in the circuit. What is the difference? Is there different benefits to using different ratios?


Thank you,
Ryan


Heikki

Re: Lundahl 1922 tranformer ratio
« Reply #1 on: August 07, 2020, 01:00:25 AM »
6dB difference in voltage gain and possibly change in frequency response if the source impedance and load impedance are kept same. I think Sta-level originally had 1:8 input transformer and a 20 dB pad in front of it. It's not 1956 anymore so compressor doesn't need gain of 60 dB padded down to 30dB and 600 ohm input impedance. For today's use 1:1 high impedance transformer would be better fit. If I had to use Lundahl 1922 I would leave the input pad out, flip the transformer around and change the 100k input attenuator R1 to maybe 1k and check the frequency response of the transformer when driven with low source impedance.

Re: Lundahl 1922 tranformer ratio
« Reply #2 on: August 07, 2020, 09:30:31 AM »
I’d like the sound to be as close to the original as I can get. Also this build has a built in pad I can switch it off and on. There is an input and output attentuator so I don’t see any harm in extra gain.

scott2000

Re: Lundahl 1922 tranformer ratio
« Reply #3 on: August 07, 2020, 12:50:56 PM »
6dB difference in voltage gain and possibly change in frequency response if the source impedance and load impedance are kept same. I think Sta-level originally had 1:8 input transformer and a 20 dB pad in front of it. It's not 1956 anymore so compressor doesn't need gain of 60 dB padded down to 30dB and 600 ohm input impedance. For today's use 1:1 high impedance transformer would be better fit. If I had to use Lundahl 1922 I would leave the input pad out, flip the transformer around and change the 100k input attenuator R1 to maybe 1k and check the frequency response of the transformer when driven with low source impedance.

Good info...Thanks


 

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