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

OK so here’s some SPL measures using db meter pro app on iphone 6 . Disclaimer: I have no info on how accurate this tool is but the numbers I am reading seem reasonable.

So in a samplling of various "typical quality nothing special" CD resolution recordings over several minutes from my closer listening position, I hit peak spl of 99 db and averaged about 86 db. Very clear and amps never break a sweat which I take as a good sign

I would rarely go louder but can and have. I’ve used amps rated at 60, 120, 180 360 and current 500w/ch into 8 ohms. I view the 500w/ch with the big OHM 5s as my insurance policy against clipping at minimum and the current Bel Canto ref1000m amps are the best sounding overall by far especially at higher SPLs. I also seem to hear the correlation between amps with specs that better double power into 4 ohm and better performance overall meaning better sound at least with the big OHM F5s. Not as much with my other smaller OHMs (8" main driver) and even smaller monitor speakers (Dynaudio contour 1.3mkII) and very small Triangle Titus that I also run off same amps.

Roger, 

Wow!  What a fast moving post.  Glad to see all the interest.

"There is a lot to this question so lets hear back from you and others."

First off, I suspect many of us non-technical types may not know much about clipping.  I've been aware of it a few times but suspect it occurred other times when I was not certain what was happening.  In my experience I've heard the sonics become thin, hard or harsh, even metallic (as opposed to musical) when pushed to loud levels but before the crack or pop of an actual clip.  I considered that a related but slightly different issue.

When listening for pleasure it is generally in the 80-85 dB range.  But I doubt my RS dB meter is accurate to identify actual peaks so I'm unsure of those.

Regarding amps > 100 wpc, for many years I enjoyed a large pair of Duntech speakers, rated at 90 dB.  John Dunlavy recommended 200 wpc for "full musical enjoyment".  I experimented with a variety of amps (tube and SS) rated from 30 to 300 watts.  I finally settled on a pair of VTL 300 monos for a few years.  That was until I heard Curl's Halo JC-1s, rated at 800 wpc into the speaker's designated 4 ohms.  That was the best I found - musically accurate, solid bass (determined by good recordings of acoustic upright bass), and effortless, unstrained sonics.  To be fair I don't believe the 90 dB efficiency was accurate with such a complex 1st order crossover.

I've since moved on from that system but continue to believe this question of headroom is very important.  Interestingly I remember hearing several times some years ago the idea that within a given line up of amps, the model with 60 to 120 watts was likely the best sounding.

I did have a RM-9 for a few years, one of those few components I was later sorry I sold.

RM - what starter book on basic electronics / circuit s would you recommend ? 

thanks again for your contribution here, so greatly appreciated.

Roger, glad to see you pop up in this thread. I still own 2 RM-9s from the mid-1980s. At my request, you modded each to become  pentode/triode switchable (dropping total power from 100 wpc pentode to 50 wpc triode). That amp in triode mode + Vandersteen 4s and VTL Ultimate remain the best sound I ever heard. My love of tubes dates from those RM-9s. 

All that gear has been in storage for decades...now it's all desktop audio/headphone audio in home office, where I recently got an OTL tube unit for several high impedance headphones (Woo WA3). Impedance issues aside, everything I love about tubes is right there, just as before--the palpable feel of music, 3D notes, imaging, humane/slightly warm tonality.

Wish I could hear your more recent designs, because based on the RM-9s, they must be very very good.

And, with regard to the great interconnect debate: do you know of any testing done that approaches that of scientific blind testing that shows that any given wire, if made out of a certain material, and wound in a certain way, and shielded in a certain way, will cause electrons to move in one manner as opposed to another that can be explained as doing so and that because of that movement can be explained as yielding sonic performance that is measurably and quantifiably superior, or even just different?

One is building a system in which all components sum for the final sound. A cable that sounds fine in one system may not in another. See http://ielogical.com/Audio/CableSnakeOil.php for more information. Be sure to read the PS Audio links. It’s a good primer on audio cable.

The great problem in HiFi is that products are touted as ’the solution’ when in reality, only ’an option’

A great deal of what is claimed is absolute nonsense.