[TAFKA Steve]

Hi again,

Traderz, make sure that the cap is actually bad using a capacitance measuring device.  Using the resistance function on a meter won't work, as all functioning caps will measure with infinite resistance ("open circuit") because they block DC from passing.  Only AC signals can pass through caps.  If the cap isn't bad and the ribbon is intact, the tweeter can still fail if the internal wiring goes (I've seen this) or the internal impedance matching transformer fails (this I have not seen).  I mentioned spraying Deoxit in the L-pads not to fix your dead tweeter problem, but to remove the oxidation that can build up in these (especially in 10+ year-old speakers) and make them noisy and intermittent.  I got fed up with L-pads and their sound, so I removed them from the circuit, but I was able to match driver outputs with an outboard active crossover feeding separate amps for the drivers.

I think Brian probably special ordered batches of 1.3 uF caps for his tweeter crossovers from J. Peter Moncrieff at TRT.  You can buy 1.0 uF and 0.33 uF caps and wire them in parallel (like the big bundle in the midrange crossover) to match.  A 1.3 uF cap with the 6 ohm tweeter (along with the parallel inductor) gives a second order Linkwitz-Riley high pass filter at 10 kHz.  I underestimated the crossover frequency at 7 kHz based on the RM/X literature, but 10 kHz is more likely because the stack of six Neo panels are run full-range at the top (no low pass filter on the mids) and have significant output above 10 kHz, but their dispersion is quite narrow at that frequency (unless you install the constant directivity waveguides).  Be sure to order the "speaker" version of the caps and not the "electronics" version.  Also, orient the TRT caps in the correct direction (see installation instructions, or follow the orientation of the cap that you removed) as they sound worse if you reverse them.  And remember, they take a while to break-in.  Heck if you've got the money you can go up from TRT and try the Teflon caps from VH Audio or Dueland, but 1.3 uF of these will cost you more than the actual tweeters, and Teflon caps take FOREVER to break-in.  If you want to go full monty you can install batteries (24 VDC) parallelling the caps to maintain DC polarization of their dielectric even when there is no audio signal, but then you have to open up the speaker to replace the batteries when they go bad, unless you OXO your speakers (remove the crossovers from the enclosures, install another set of binding posts, and run three pairs of wires from your outboard crossover to separate terminals for the woofers, midranges, and tweeter.  And then there is the active crossover option with tri-amplification of each speaker.

BTW, for the James Bongiorno electronics fans among the VMPS crowd, Cullens Circuits bought the rights to manufacture and market updated models of the Ampzilla, Son of Ampzilla, and Ambrosia preamp.  They were playing the new Son of Ampzilla at T.H.E. Show at Newport Beach this weekend.

Steve

 

[James Romeyn]

Steve,
Which of the SST amps did you hear at Newport, if any?  Powering Emerald Physics or Fritz? 

I talked with EJ at Newport to see if I could briefly compare SOA to what may be the best amp I ever heard, which was in our own AudioKinesis room.

EJ did not have the SOA I requested, the $4200 amp released circa 2004, that looks like Ampzilla mono.  But EJ did have $3000 SOA II in all-new all-black chassis, classic shape and dimensions, withi heat sinks on both sides (image at Part Time Audiophile Newport THE Show coverage for Wyred4Sound). 

At 2012 Las Vegas THE Show Bongiorno showed me SOA II chassis (empty), and he said it would be the new GOA (Grandson).  For reason I'd rather not say I suspect the all new SOA II replaces the '04 SOA.  I suspect each day is one day closer to no more new SOA.

For some strange reason I did not think of auditioning SOA II.  I regret the oversight and wish I heard it.  EJ said SOA II mimics SOA circuit, with some lower cost parts and obviously lower cost enclosure. 

The other SS amp worth looking at, for exact same $3k price is Benchmark's all new AHB2, releasing just about now (a few months later than expected).  SOA II is much larger and likely weighs much more, but that says nothing about performance. 

I wonder if SOA II has "captive" AC Mains, a Bongiorno main stay on all his power amps.  When I last check Ampzilla website a couple weeks ago absolutely nothing about SOA II. 

Between SOA and Ampzilla mono series I, I preferred audio performance of the former.   

[TAFKA Steve]

James, I heard the SOA II playing the Emerald Physics speakers in their room, but the sound (for any number of reasons) was not that impressive to me.  Wished they were playing it in the Fritz room.  The Benchmark amp on the Benchmark speakers produced good sound.  Russ Stratton (russtafarian at AC) had an overnight loan of one and he told me it was an excellent, highly resolving amp, so maybe their greater claimed S/N or dynamic range is actually audible.