Impedance mismatch question

Regarding tube preamps would an output trandformer in place of the capacitor eliminate or reduce this potential fluctuating impedance mismatch ?

The issue with an output transformer is loading. If loaded at an impedance too low, it will roll the highs. In addition, the tube driving the transformer will see a lower impedance and so will make more distortion.

If the load is too high the transformer can ring. This will add brightness. In some cases where the loading is really way too high, the transformer will begin to express the inter-winding capacitance as part of its output (rather than the turns ratio), causing a loss at the frequency extremes and what response there is will not be flat.

Amplifier input impedances can vary by 10:1 so it is helpful to know what the transformer is set up for. The manufacturer of the preamp can supply that information.

George, I agree with you. Wow, I think this is a first! My tube preamp has an output impedance much like Almarg outlined. Can go as high as 4k etc.....

I have run it with all kinds of amps with as low as 22k input impedances with no issues at all. Seems this whole thing of a 10 to 1 rule is really not hard and fast. My experience indicates it is not really that helpful. My last solid state amp had a 22k input impedance and my 4k output impedance preamp sounded fantastic with it with no roll off at all. Also, the output cap's value was a low .47uf again with no issue or bass loss.

Just my actual experiences. Others own the same preamp and with amps that have 20-40k input impedances with no issue. Pass Labs and Nuforce amps....

This question comes up often and the answers with the ratios have puzzled me of late simply based on my and others experience.

Yes I have extremely happy Lightspeed customers that are driving it into 22k poweramps with tube riaa phono stages as the source.
As for driving interconnects the only time this comes into factor is when the interconnects is poor quality and has vast amounts of capacitance (>200pf per foot), then it can roll of the highs, but the same cables will also roll of the highs with high output impedance tube preamps, tube phono stages and tube cdp's of which there are quite a few around.

Cheers George