glens

Well there are many who love the warm smooth velvety sound of phenolic diaphragms.  Possibly half that and half the higher-ESR (aged) capacitors in series with the HF drivers in the IIs causing the noted difference. And maybe mostly the caps... Still, I'd think there wasn't a night/day difference in sound and a couple grand left over goes a long way.

Yeah, but are they going to swell again, only this time sooner? And if nothing else is amiss, maybe more suitable caps are in order?

I looked over the schematic and service manuals and don't quite see what you stated. Both amp channels still run with their own error corrections. I don't know the merit in doing it the way they did over the Hypex implementation but I'm sure they had a reason. Hypex's method doesn't require an explanation for me. Along with the load appearing to the output as half impedance, I'm pretty sure there's a halving of damping factor as well, though with the astronomical level of that in the Hypex it won't be a factor even if I've got that right. Which boards are you going to use?

It might've been the caps just went bad, but just as likely, or more, something else made them die. A more thorough checkout should be in order.

Yes, NCore. I don't need any amps at the moment, but the next one(s) will be Hypex. I seriously doubt there will be any negatives regarding bridging NCores. Hurry up, put it together, and give us your positive report!

I'll take that as a compliment. So he was an opinionated *** as well?

That works for me. Here's something to consider as well. Draw a graph in your mind with the X axis being 0 volts and a waveform alternately going positive and negative; it's easy, you've seen it a million times. 'Normal' operation would consist of one lead hooked to the X axis and the other lead hooked such that it follows the curve. When bridging, everything works the same, except that what would normally be a stationary X axis now moves in equal and opposite directions from the curve; that's to say it's no longer stationary. Or you could consider it to remain stationary but the waveform is affected by a 2x multiplier at all times. I've used bridged amps in the past, and wouldn't rule them out in the future, but there is one conceptual aspect that I've always considered. It pertains to linearity between any two samples of a component; transistors in this case. It may be that any two have exactly the same operational characteristics, but I rather doubt it (I mean exactly the same in all respects). Compound that to include other circuitry as well. The purist in me thinks that bridged mode must entail a certain amount of degradation. It's likely below the threshold of notice for the most part, and in this particular case the Hypex stuff makes use of liberal negative feedback anyway, so my musing is likely unimportant. But the thought remains in the back of my mind nonetheless. I'm a fan of Hypex. My NAD uses a UCD implementation. I like how the following generation (forget what it's called) has a pinout for a clipping indicator, which I'd utilize in a heartbeat - just because I like to know such things.

I'll have to look it up - there's a website which catalogs the dynamic ranges of recordings. You can also get a utility for your computer to analyze digital audio and arrive a figures which match those of that database. It's subsiding somewhat, but during the 2000s there was a concerted effort, it seems, to do just what you seem to be espousing: increase the recorded signal to the max. To get it sounding even louder yet, they compress the dynamic range and usually shape the spectrum to favor the midrange/treble. One such example is (at least the version I have if there's more than one) Zeppelin's "Mothership" which is a compilation of "remastered" hits. It's almost unlistenable on decent-enough equipment. I bought a remaster of Lou Reed's "Rock 'n Roll Animal" (arguably one of the best ever "live" recordings) which included a couple more songs from the event which wouldn't have fit on a single LP. I had the LP (maybe still do) from the late '70s, and bought the CD sometime in the late '80s. The extra songs on the remaster are hardly worth the reduced sound quality compared to the early CD (which may well have been produced from the LP-era master tape). The disc isn't terrible until you hear the non-remastered version. One of the lowest-level-recorded CDs is (the early version of?) Dire Straights' "Brothers In Arms." I believe you would complain about the low level of the disc. But it has one of the highest scores (very high dynamic range) in that database! And it's an utterly pleasurable sonic experience when listened to, even if the equipment gain must be increased to play it loud. So I'd have to say that your contention, that a low (average) signal level on a digital recording is undesirable, is misinformed. There's nothing wrong with getting the hottest recording level possible so long as the content isn't compressed or unfavorably altered in other ways to accomplish the goal.

I don't know about loss across transistors... I do know that when bridged, the load appears to the amp as half what it would be un-bridged. Just build it the way they suggest. You'll be satisfied, I'm sure.

Like I said above, what you've got in that case is +/- 50 volts (25 volts each in equal and opposite directions simultaneously), or 100 volts to work with.

You've got the two DC rails at +/- X volts. When a waveform is heading toward one rail in "normal" use you can end up with only X volts maximum across the load at any given instant. When bridging, you're inverting the signal to one of the amp channels and driving them simultaneously to the single load, so when a waveform is heading to one one rail, it's also heading to the other rail at the same time on the other lead, so you can end up with 2X volts maximum across the load at any given instant. Did you not understand that? So on only 1 of the two peaks in "peak-to-peak" you've got 2x the rail voltage, and on the inverse peak it's another 2x. Ultimately you wind up with 4x a single rail voltage for your available peak-to-peak output.

Yeah. At least a couple inches! But that's all...

 Sorry, but Led Zeppelin remasters are not as digital as it gets. Those are not digital recordings. The original masters are analog. 50 year old analog tape masters. Every instance that I've encountered of Zeppelin (digital) "remasters" rank in the lowest of low quality. 'Mothership' has got to be one of the worst discs I own. Excessive levels with compression and utterly horrid frequency balance. The capability of (even "lowly" CD) digital so greatly outshines that of LP that it's not even close. The specific implementation is the key. 'Twinkle toes', you should find the thread about "demastering" in the technical forum for a better understanding in general. Your ideas are not "sound" in this matter, from what you've stated here in this thread.

Whole-heartedly agree. Though reviewing the photo, you could recover use of, or at least access to the fireplace if you flew those Hereseys inverted about head-high at the tweeters. I guess I'd do that before buying bigger speakers, but if you want to tie up the floor, the Forte IIIs will occupy almost exactly what the Hereseys do and give arguably better sound.

Ouch

Jubilee

Moving ain't so bad if you're the one that packed your stuff. In that respect, sometimes "help" ain't so helpful...

While the voltage level in-to-out of the transformer is a direct function of the turns ratio, the impedance as seen by the source is a function of the turns ratio squared. Without seeing what else is going on in the network it's hard to say just what he's doing, but with the transformer by itself it's utterly impossible for the amplifier to see "Flat 8 Ohms impedance load to amp at all settings." At a turns ratio of 1:1 an 8-ohm driver would appear as an 8 ohm load. At a turns ratio of 2:1 (50% reduction in output voltage) an 8-ohm driver would appear as a 32 ohm load. If the crossover elements are before the transformer, the crossover point would change as well as driver output level when different taps are used. If the elements are behind the transformer then only the output level would change, though the amplifier would still see the drastically different load. Modern solid-state amps shouldn't care, but those with output transformers will behave differently.

And yet JBL goes with the inverse of mumps...

After all these years I recently became aware that transformers do weird things with impedance. Especially with tube amps L-pads would be the superior implementation and I just don't get why transformers would (have) be(en) used. Surely a transformer is so much more costly to produce than an L-pad that it would more than offset the cost of the higher-value capacitor(s) required with the L-pad. Re: resistance vs. impedance, it doesn't matter whether it's AC or DC, if the load is purely resistive, it's resistance. With AC only, if the load has complex components (inductance and/or capacitance) then it's termed impedance. If the complex load is fully corrected by adding capacitance or inductance in the proper amount needed to maintain the current and voltage being in step, then the source would see, effectively, resistance.

I use 128k mp3s for the bike. Plenty good sound quality for the environment. As well for the jam box at work. Most times the fact that there is music at all solidly trumps any technicalities about it. In the house, however CD quality is the preference. If space / bandwidth is a concern then flac to the rescue. Higher sample rates and bit depths might in some cases have an audible difference, but I've never been able to detect, much less appreciate, them in any of the samples I've encountered. The mix/mastering is the larger limitation to good sound quality.

Later even than me. I'm fixin' to start my 58th year of breathing oxygen.

The worst of the damage may be hidden by the dust cap. Have you got a look at the backside yet? What hit it?

That was more like a buck and a half. There were a couple points I disagree with, but not enough to actually do it. There's enough info there to arrive at a determination in this case. If not, the question wasn't genuine.

Looks like a blunt object impact just left of the split, ~1/3 from dust cap to surround was the cause. May be more damage than a bit of glue can right.