TRL Dude or Joule 150 MKII for Major Pre Upgrade

Ralph, the present (original) value is 100 ohms. Do you still feel that is not the problem?

Best regards,
-- Al

Acck! I now have to say hold everything cos I just looked at my NP220PG and the grid stops to the 6SN7 (also in diff amp config) is 100 Ohms. They are place after the grid leak which is 100k to ground.
So if my NP100PG is so darn quiet and EM free even with crappy cables whats up with Grannyring's Aesthetix?
My NP has very low gain though, my speakers are 89-90dB efficiency.

Update. The use of a Jensen input transformer under the brand Iso Max completely removed the buzz to a dead silence. Simply place the input transformer between the amp and preamp. Single ended preamp into the Jensen Iso Max using my RCA ic's and out from the Jensen Iso Max into my amp using xlr connectors. So the Jensen receives RCA in and xlr out. I am now able to use my amp in it's fully balanced mode.

The xlr ic's going from the Jensen to the amp must be 2 feet or under to avoid any signal deterioration.

The down side is the cost of the unit plus the cost of an extra set of ic's. Not sure as yet if then Jensen changes the sound as I am using some pro sound Mogami xlr's for now. The sound does seem a little more polite or less alive, but this my be the new set of IC's?

I will soon receive a set of xlr ic's of the same brand that I use throughout my system. I will update all as to wether the Jensen input transformer changes the sound.

The sound is very good with the inexpensive Mogami cable however. A little less top end sparkle is what I notice thus far.

I also left Jensen a message to clarify the compatability of the unit with a higher output impedance preamp. The site suggests the preamp should be no higher then 2k ohms , but other threads I have read seem to suggest this may not be the whole story.

Success, at long last. Outstanding! Although I guess we'll never really be able to be sure of exactly what was causing the problem, given the bizarre results of some of the experiments.

The key thing with the XLR cable is that its capacitance has to be kept very low. I suspect that you are using the PI-2RX transformer, for which the datasheet indicates a maximum acceptable load capacitance of 100 pf. That would be for the sum of the cable capacitance and the input capacitance of the amp (which is unspecified). I suspect that the main consequence of driving the transformer from an output impedance that is significantly higher than the 2K recommendation will be that the load capacitance becomes even more critical, excessive capacitance potentially affecting the highs particularly.

For most purposes the capacitance of Mogami's Gold Studio or other Mogami 2534-based cable (if that is what you are using for the time being) is reasonably low, but it may not be low enough in these circumstances. I don't know what kind of cables you are awaiting, but if they do not have very low capacitance you might want to consider say a 1 foot length of inexpensive Blue Jeans/Belden 1800F, which would be only 13 pf plus the capacitance of the connectors.

Best regards,
-- Al

Thanks Al. I will check into the cable capacitance to be sure I am doing all I can for best sound.