atmasphere,
The issue is performance, and without a proper low impedance buffer, at the input, not 6 feet of cable, with capacitance and inductance, the performance suffers in my testing (with actual test equipment).
I don't doubt he did it, just pointing out that it is not an optimum implementation.
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What an entertaining thread. A bunch of people (mainly) with obviously from this thread and others weak engineering skills (at best) with odd exception pumping their chests and egos while arguing about things they poorly understand while making wild and patently false claims about all kinds of things.
w.r.t. the purifi and hypex modules they need an input buffer to operate to specification. They cannot just be driven with a "lowish" impedance source. They are meant to be driven with a very low impedance source, i.e. like the buffer circuit on the eval boards. It sounds like the ops supplier is not qualified at what they are supplying.
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While on one hand, op-amps in the same circuit can sound different, which often says far more about the circuit than the op-amp, anyone claiming to be immune to sighted bias is delusional. If you can't be honest with yourself?
Circuits need to be tuned to a particular op-amp for best performance, so I always take with a grain of salt op-amp swaps.
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georgehifi8,490 posts02-17-2021 10:28pmNo, it is not, especially with the Hypex amps. The input is meant to be driven by a very low impedance source. Once again, you have no idea!
The
input impedance of the NC500 Hypex is 2k across the band, and can be
driven by any buffer from a source that has 50ohm or less output
impedance and the voltage gain needed to give you the max level that you
need listen to. Once again, you have no idea!!
I'll try to get my friend who heard it yesterday to post on it.
Well I have listened to enough audio equipment for 5 lifetimes, do I win a prize? I actually know how to design an amplifier too. People who actually know something about high performance analog design (and Class D), can reference the data sheet here on the HYPEX website. Now consider the transient performance with the source 2 meters away in a high speed feedback loop for Class-D. |
georgehifi8,489 posts02-17-2021 7:10pmIn
my past experience with the Nord Hypex NC500 monoblocks using the
Sparkos and Sonic Imagery opamps, the differences were pretty obvious. Best is no buffer at all, direct in, as I’ve done. (you don’t need a buffer driving another buffer)
If
the output buffer in your source (pre or dac) is less than <50ohm
output impedance and has high enough voltage output gain to give the
volume you need, you’ll have better sound than any additional buffer
(regardless of how good) that’s in the signal path
Cheers George
No, it is not, especially with the Hypex amps. The input is meant to be driven by a very low impedance source. The input of the unbuffered amp is essentially in the feedback path. Not having a local buffer is a recipe for doing it wrong. This is the difference between people who actually know what they are doing and those who do not. People who do not make statements like this above. |
I can remember how something sounded 10 years ago.....really! Righhhhttttttt Most people can't pick their own speakers out of a line up once they are gain matched and frequency compensated, and often not even with frequency compensation. You may remember a general impression, but from a comparative basis 10 years ago, sorry, that is just not true. You believing that does not make it right. Toole showed in the Harmon tests how flaky most audio reviewers are. Looking at the rooms many of them used, different speakers, etc. the odds of them effectively pulling the characteristics of a single unit out are slim (to none). |
Linear power supplies on amplifiers draw current in large peaks, much higher than the average power current draw. A 500W isolation transformer will act like an inductor with a current limiter. It may be better, it may be worse.
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Oh george, you must realize by now that everyone knows you are the looney bird here. Quack quack.
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This is what it says, "Furthermore,the NC500 OEM is an unbuffered amplifier leaving the implementation of an input buffer up to the manufacturer. The NC500 is practically devoid of any sonic signature so this external buffer is a good way of tuning in a “house sound”."
It does not say any of the other things you are implying, and there is no truth that this is true. We have noted the performance THD+D and IMD is impacted by the output impedance of the buffer when we did testing .... you know on actual test equipment.
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02-21-2021 7:17pmWhat
you are hearing is what class d amps do they produce high wattage with
low current to save money on energy and expense of manufacture to make
more money for the manufacturer and they will not have the required
current to dive the proac speakers you have they like a good high
current ab type amplifier i am glad you did not spend much money on the
class d amp you dodged the bullet with that decision. More making things up. I really don't consider 25 amps that limited. That's 1250 watts into 2 ohms. Class D amps primarily have thermal limits because real world music is not 1000W continuous, ever. That's a magazine test.
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If you like or need volume, that "pathetic" 20W amp sound quite anemic. So it doubles to 1 ohm. If I have inefficient mainly 8 ohm speakers it will still be anemic. There is no magic in a 160W into 1 ohm amp that halves in power all the way to 8 ohms.
You shot yourself in the foot with this really idiotic argument. I expect most people are shaking their heads reading it.
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Given the price of high end audio equipment, if you are doing 1K units a year, 3 year design, 3000 units, you could amortize the $100K design cost, at $33/unit additional. Most audio companies would be best off contracting that out. Hypex does their own, and I have seen some a company or two offering audio targeted switch mode supplies.
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I will note one thing though- I've seen a number of SMPSs (Switch Mode
Power Supplies) used in class D amps. I think its a bad practice. They
work, sort of; the problem is that class D amps go from almost no
current draw at idle to quite a lot at full power. SMPSs don't have a
lot of capacitance at their output and so can be drained faster than
they can replenish. A lot of them will shut down if you put a lot of
capacitance at their output. So if you're not running an amp with a
regular power transformer and a lot of capacitance available for the
class D amp to feed on, you're probably not hearing what it can do. I can't agree with this statement Atmasphere, it really depends on the power supply, how it was designed, and circuit limitations. Most switch mode power supplies for power amps I see for audio are not power factor corrected. They tend to be single stage LLC, with a simple bulk capacitor arrangement on the front end. Poor design choice in my mind, but is what it Is. They store most of their energy on the high voltage side, not the low voltage side. Let's say no PFC boost front end, so at 120V, say a bulk voltage with losses of 160. Pretty easy to put 1000uF, if not more on the front end. At 160V, that's 12.8 joules. That's the equivalent of 16,000uF at 40V. I would be more inclined to put a PFC boost front end with a link voltage of 400V. Now my 1000uF (450V capacitors) is like 100,000uF at 40V. That 450V, 1000uF capacitor is lot smaller than the 100,000uF, 50V capacitor. All that is required is the LLC stage has high surge (added power capability), and suitable continuous capability. |
