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RE: Phono Step-up Transformer

Posted by Ralph on July 16, 2021 at 15:12:57:
I prefer a good solid-state unit
I understand the lower noise thing quite well.
The problem I have with solid state is not what they sound like. Its ticks and pops. Now this doesn't happen all the time, but its quite annoying when it does.
The cartridge is an inductor and the tonearm cable has capacitance. Together they create an electrical resonance; with a LOMC cartridge this might be at a couple of MHz- and it can be a good 30dB peak! (30dB suggests 1000x higher than the cartridge signal)
If that peak is energized (goes into 'excitation', the radio world term for this phenomena) the resulting energy can overload the input of the phono section, resulting in a tick or a pop, unless the input circuit has a very good high frequency overload margin. With tubes this is easy to do, so if there is an overload in a tube phono section it starts at the output of the circuit and progresses backwards if the input signal continues to be increased.
In a solid state circuit the overload can occur right at the input circuit itself. If this happens you can get a tick or a pop, sounding for all the world as if its on the LP surface. If the phono section employs an opamp at its input this can be very hard to avoid!
Now if you design with this electrical peak in mind, a side advantage is that you will find you don't need the 'cartridge loading' resistor since its there to detune that electrical peak; IOW its there for the benefit of the phono section rather than the cartridge.
When you load the cartridge from the stock 47,000 ohms down to 100 ohms you are asking it to do over 2 orders of magnitude more work. This causes the cantilever to get stiffer, which can affect how the cartridge performs in the arm.