Does anyone care to ask an amplifier designer a technical question? My door is open.

And I thought the unanswered question was who wants the last piece of pie?

We get requests from folks who want their old RM-9s refurbished. One of the common side requests we get is to put in an IEC inlet in place of the captive power cord, which from Roger’s perspective is more than adequate for the job, of reasonable length, and quite flexible. We try to talk folks out of this as there is just not enough room between the transformer cover and the edge of the frame to add an IEC inlet. In addition, the RM-9 frame makes this task rather difficult as you have to cut into the wood and there is risk of damage if not done properly. So for those who insist we advise them we will chop the stock cord about 6" from the top plate strain relief, attach a male IEC, and finish it off with shrink wrap and the customer gets to choose the power cord of their choice. Now the signal comes from the Romex in the wall, through the designer power cord, then that last 6" through the original stock power cord into the power supply.

However, some may not be aware that Roger does acknowledge a power cord can make a difference in the system. In this case, a power cord that addresses hum caused by having DC on the line, which can be a hard problem to fix. So he designed a power cord rated at 5 amps that removes DC and will quiet troubled transformers.

The little under the bridge creatures have caught the scent Roger.

Exclamatory math.

QUESTION: Roger (or Ralph?)...

Question about the effects of different impedance settings and phono cartridges.

I’m a newbie with high end turntables (just replaced my old turntable with a much better one). My phono stage is convenient in that it allows easy access to changing the impedance levels from the front panel. I actually enjoy playing with the impedance settings to alter the sound to taste depending on what I want.

Mine is an MC cartridge and I find an impedance setting of 100 Ohm to be just about right in terms of sounding tonally accurate (like my digital source).

I won’t be telling anyone here what they don’t know when I mention that as I set it to higher impedances, the sound gets brighter and more taught (to more "pinched" and less relaxed/natural sounding towards the high end of the impedance settings). And the sound becomes darker (more rolled off in the highs), richer, more spacious and the bass seems to bloom a bit more in size and lose some tightness. I actually often enjoy just dipping down the impedance from the 100 Ohm setting to the 33 Ohm setting, to enjoy the slightly richer sound sometimes.

So my question is: What exactly is happening to cause the type of sonic changes on hears when changing impedance settings for a cartridge?

My know-nothing layman’s hunch is that it’s similar to how speaker impedance interacts with certain tube amps, where some combinations contour the frequency response...and (sorry for the word) damping factor? (The changes in the bass in lower impedances do give me that "lower damping factor in the bass" vibe).

Thanks..