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In the Forum: Audio Discussions
In the Thread: Initial thoughts about new/old Lamm ML2s
Post Subject: Coincidental clippingPosted by Paul S on: 9/30/2007
Maybe my output tubes are fading already because that seems like a lot of drift happening pretty fast compared to what I have experienced so far. I suppose there is a lesson in it, in any case.
No fantasy about dropping the current from 320 mA & 310 mA (where right and left channels had drifted) to 280 mA and raising the voltage from 183 to 185. At the points where they drifted to they sounded "over-driven" (as you might imagine), rather like my speakers sound when they are over driven, and at 280 mA (measured as VDC) the sound settles down with excellent harmonics and all else. Whatever the reasons, the differences in sound between these operating points are considerable, and in my stystem it involves more than just bass. For one thing output in the "worst case" drops from ~59 Watts to ~52 Watts. Although I would never intentionally shoot for 59 W, it is also unlikely that would I have gone to 52W unless you had tossed out those numbers.
I have not tried to calculate whether the 280 mA/185 V combination is the mutual-clipping point of voltage and current with my speakers, but unless it damages the amps I will run them where they sound best. As I mentioned earlier, my speakers are nominally 8R but they have a significant spike and also a sharp dip to 4R, so I would not know apart from listening which calculated points to regard.
In this case I measured the amps' OPs because it was obvious that something was wrong.
OTOH, at the referenced lower operating point the harmonics from this amp are far and away superior to anything else I have ever heard; pretty much of a revelation, really. Pitch and timbre are just excellent, and I am very happy with it. Also at the referenced points noise damps down and the whole comes into much better focus musically. With my speakers, Lamm's recommended points sound more hi-fi and less musical by comparison, along with an edge that I find annoying, especially at HF. Also with my speakers the whole thing "congests" at lower SPL/complexity when set at the "stock points". Maybe I have just better matched my speakers, or for all I know I am rolling off HF, although I have to say that musical HF improves at the lower setting. Likewise with the bass. But I am not trying to explain it, I am just reporting.
It does make me think when you report preferring the same operating points with such different speakers.
Sunday is usually OK for electricity here, and today was OK.
Obviously I will have to keep a closer watch on the OPs.
Best regards,
Paul SRerurn to Romy the Cat's Site