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RE: What tubes to use with this Interstage Transformers?

Dave,

I can certainly try that. Is it to stimulate 5K source impedance so it's close to the ideal load impedance from the IT Primary?

Looking from the IT side, inserting a 5K (2 x 10K Resistor in Parallel) in series with the Input so the source impedance of 50 ohms before is now 5K resistive source with still 50ohms impedance drive at 20Hz.

But looking from the Signal Generator, the source impedance of it's own is still 50ohms (that is somewhat variable with frequency it's set at) and it is now driving a voltage divider of 5K series resistor which is in parallel with DCR plus the impedance of the Primary side of IT at 20Hz.

Max Current from SigGen supply to the IT is about 42mA (21Vp-p@20Hz / 5000ohms) but it need to drive the parallel load with (40-100ohms) DCR plus some reactive impedance of the primary of the IT side.

As far as I have learned, most Signal Generator are made to drive mostly resistive load or reactive load at much higher frequency than 20Hz. There are some shortcomings and stability at driving reactive at low frequency due the transmission line reflection.

Anyway, what I am saying is that the input signal to the IT will be highly distorted at 20Hz due to the reflective impedance back to the Signal Generator combined with it's own internal impedance at 20Hz.

That distortion is not due to the lack of inductance of the Transformer at 20Hz since there is no load connected to the IT yet (secondary side still open).

That distorted signal will somewhat recover when the frequency on the signal generator slowly rises (let's say 50Hz or more). It's again not due to the connected IT with the open secondary.

I have some other transformers with 50ohms primary and 15Kohms secondary (step ratio of 1:18) which I can cascade the IT for more FR sweeps.

Would it do what you want to do?

Thanks,
James



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.Thou shall not stand where I type for I carry a bottle of Certified Audiophile Air and a Pure Silver Whip.


Edits: 08/27/16 08/27/16 08/27/16
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