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Re: 27 preamp

Thank you for your responces. About the filements I tied them in parallel to a Center Tapped 2.5V winding on my transformer, the voltage is about 2.42V AC and I connected the CT to the signal ground. Former experiments with Voltage regulation did not satisfy me. Due to a light hum I will try Current Reg. soon.
I also think the problem is with the LineOPT, but just because it is not settled in yet. Slowely I hear more bass. It measures 11 Hz - 62 kHz (-2dB), specs are prim. imp = 10k (110H), sec.= 600 Ohm. Maybe I just have to be patient. I did not start with an Anode resitor/Cap output because I do not need the gain for my power amps. I also tried some different PSU configurations without great difference in sound. At the moment I use 150 0 150V AC 6X5 - 22u BG - 12H - 220u BG (split to LR) each channel - 10K 2W AB - 22u BG.
What striked me most yesterday was, removing a 150 ohm (1W RikenOhm) gridstopper also removed some graininess, the same happened when I swapped the 2k2 2W Tant. cathode resistor bypassed by a 220uF BG FK for the 9V NiMh batt. The only resistors left, except for the 2 x 10k AB 2W PSU resitors, are the 100k Nobel vol.control and a 2k 1W Tant load resistor on the sec. of the line OPT.

Thanks so far,

Ronald Koridon,
Amsterdam.


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