drasw
Seeker Of Truth
Posts: 1
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Post by drasw on Dec 8, 2023 9:51:01 GMT -5
Any reason to upgrade to the XPA-1 Gen3 Monoblock when I already own the XPA HC-1 High Current Monoblock Amplifier that I bought 18 months ago? Thanks
T
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Post by ttocs on Dec 8, 2023 10:01:01 GMT -5
No. Same guts, different boxes. One box is expandable, the other isn't.
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KeithL
Administrator 
Posts: 9,976
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Post by KeithL on Dec 8, 2023 10:01:55 GMT -5
Nope... they're pretty much the same inside. The XPA-1 just lives in a full-sized cabinet - for people who like the "standard size cabinet". (Arguably it might have a tiny bit more room for cooling... but that is not a significant difference.) Any reason to upgrade to the XPA-1 Gen3 Monoblock when I already own the XPA HC-1 High Current Monoblock Amplifier that I bought 18 months ago? Thanks T |
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Post by leonski on Dec 12, 2023 23:04:03 GMT -5
for the FEW who actually need and use the power provided by the most powerful amps?
DO NOT underestimate the 'cool factor'... At the limits, every bit helps......
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Post by ttocs on Dec 12, 2023 23:24:09 GMT -5
for the FEW who actually need and use the power provided by the most powerful amps? DO NOT underestimate the 'cool factor'... At the limits, every bit helps...... I agree with your suggestion. However, I tried a pair of HC-1 amps with my electrostatics that dip to 0.7Ω, and the HC-1's never got more than slightly warm at high volume for hours at a time. |
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Post by leonski on Dec 12, 2023 23:26:28 GMT -5
You wern't trying!
years ago I had a Carver Cube...the M400t. claim was for cool running. but not ME! I ran amp to redline (ladder display flickering to +3) for
hours at a time. Speakers coudn't take any more......they were basically 5 ohm and very low reactance......But that amp? I could warm it up
considerably to the point I built a fan for it which 'nested' to the back of the amp and sucked air OUT. Problem solved......at least for another
decade. Didn't matter that the fan was noisy. Music was MUCH louder.
I was being snarky saying you weren't trying. Truth is? You probably don't need that kind of power. Even though the panel IS of very low impedance
and being a 'stat, I'd also suspect a highly reactive load....for maybe the last octave (10k to 20k). the good news is that power demands at those frequencies
is maybe only 20% or so of power required....
Cudos to the amp for surviving such conditions. I don't know if my Parasound amps would or most anything I've ever owned......though I also have never
owned 'stats....Friends of mine back in the early 80s BLEW UP an amp in testing stats. I was there for the test. It emitted an ultrasonic 'chirp' and ceased....
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Post by PaulBe on Dec 12, 2023 23:52:23 GMT -5
Amps that use feed-forward techniques don't have ultrasonic problems. Amps with ultrasonic problems driving High frequency, Low impedance, High capacitance reactive loads, are amps that derive all their feedback from the output stage and have too many poles in the circuit. They become oscillators - This is almost All power amplifiers that Don't use feed-forward techniques, regardless of output capability.
A feed-forward amp still needs to produce enough current into a low impedance load, and stay within SOA, but stability is independent of load.
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Post by leonski on Dec 13, 2023 3:32:26 GMT -5
Could you provide any kind of link? I see all sorts of references, some going back to the 1930s.....but mostly very technical......
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Post by PaulBe on Dec 13, 2023 7:25:18 GMT -5
Try looking for articles from Peter Walker or Nelson Pass. Quad, Threshold, and Benchmark used/use feed-forward. I added it to a couple of big amps I modified. The first place I saw it was an article by Peter Walker. Then an article by Nelson Pass in Audio Amateur. Then, I saw it in a schematic for one of Threshold's Stasis amps.
The point is to add the high frequency feedback from the drive stage, forward of the emitter follower output stage. This avoids the 2-3 poles in the double or triple darlington output stage. Hence - Feed-foward.
The drive stage needs to be made robust enough to handle the additional high frequency feedback current load. It's not much more, but too much for a normal voltage gain drive stage.
This is as non-technical as I can make it. Just look at key word references, including ones you already found, and grok on it. There are more details; all technical; all off topic from this thread.
I don't know what the XPA-1 Gen3 Monoblock, or the XPA HC-1 are doing. The XPA amps still have a Zobel on the outputs. They are obviously stable enough into a Martin Logan electrostat with a reactive low impedance high frequency load.
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Post by leonski on Dec 13, 2023 23:49:47 GMT -5
Threshold was, of course, a Pass effort which yielded several patents......I think Nakamichi got involved here, at some point?
You can buy a Nakamichi Stasis power amp.....
And Paul? What if you simply SKIP the darlington output? (2x or 3x) Either single ended 'A' (like the Pass ACA kit) or more
conventional A/B outputs....? Who, besides EMO still uses such output devices? Who makes 'em? Or can you build-up using
discrete?
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