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2nd generation EIGENTAKT PURIFI 1ET6525SA (successor to the 1ET400A)

What is its SINAD Value?
It's unbelievable. Better than Benchmark AHB2's.
Do we still hear the difference between these extreme fidelity amps?
 
What is its SINAD Value?
Depends mainly from the input/gain stage it is hooked to. The 1ET6525SA is a part (the main one tbh) used to build an amplifier, not a finished amplifier.
The same way that the DAC chip performance doesn't tell the DAC performance since it is highly dependent from the power supply and output stage used.
 
A comment on THD+N vs. SINAD: These are usually close but not always exact because not everybody measures the same. Consider the following IME.

Audio commonly measures THD+N by measuring THD when driven by the signal, which is harmonic spurs (only) relative to the fundamental, and then noise by shorting the inputs and measuring the output noise. Combining (normally RSS -- square root of the sum of the squares) yields THD+N. Thus THD is the ratio of signal to the sum (typically RSS) of harmonic distortion terms, and noise is measured with no signal present. THD neglects other spur sources like power-supply noise, clock noise, and so forth. Noise measured this way ignores the influence of signal level on the noise, and may include power supply spurs and other "noise" in the measurement.

SINAD is meant to be all-encompassing and so includes harmonic and non-harmonic distortion terms (can include things like clock noise/spurs, power supply noise/spurs, etc.) as well as in-band noise. It uses the ratio of the signal to all other terms captured by the measurement so generally is a little worse than THD+N.

SNR is ideally the ratio of the signal to only noise, though again some include other terms in the SNR. A fairly common scheme is to apply a signal and subtract out the harmonic distortion terms, since a long FFT has narrow enough bins that the result is not significantly affected. High power or other spurs can corrupt the "pure" SNR measurement.

Both measurements include noise in the fundamental (and harmonic) bins so a high level of noise can cause errors in their level. This is usually important only at very low power levels, as harmonic spurs approach (and often fall below) the noise floor, and is one reason for the rise in THD+N at low power levels (it is dominated by noise).

A single number is often useful as a baseline metric, but a more detailed look at the frequency spectrum of the noise and distortion is normally required to make a final decision among comparable devices, and recognition of the system. Low noise may be more important for highly-sensitive speakers, for example, along with low power-supply spurs. Switching power supplies put the supply noise at very high frequency, above the audio band, so may be desirable in some applications. Etc.

Spread-spectrum communications and some other RF applications can make calculating these terms challenging on the actual "live" signals...
 
Couldn't agree more. My 4216/E2 stereo amp just arrived last week and I find both build- and sound quality, as well as the feature set excellent. Fred was super helpful and worked with me on customizing the low gain input setting to better match the low pre-out voltage (1.4V max) on my Denon X3800H. Good luck finding this level of engineering-first customer centrism from any larger manufacturer. So even though I'm US based, I had zero concerns ordering with Fred.

In general, the continuous power ratings and 2 Ohm stability with these new Purifi modules paired with minimal heat emission (vs older Hypex, or class A or A/B amps), low power consumption and compact form factor in a very nice implementation objectively represent an excellent HiFi value. I appreciate Purifi, Boxem, Buckeye and other smaller vendors here who are pushing Class D forward at reasonable prices for helping democratize sound quality.
May I ask how this was resolved or what the best practice is? I will add a A 4216/E3 to a Marantz Cinema 40 on a KEF R(7+6) Metas setup. Just have to wait until the room is finished..
 
The way the new Purifi modules just keep pushing clean power at over 100 W and that smooth and gradual onset of distortion look so damn sleek :D

Some graphs:

THD+N Comparison_1ET6525SA.png


The usual disclaimer: I gathered this data from various sources including manufacturer spec sheets. The measurement conditions might differ. Especially the gains are likely not the same for each amp.

Sources:
 
May I ask how this was resolved or what the best practice is? I will add a A 4216/E3 to a Marantz Cinema 40 on a KEF R(7+6) Metas setup. Just have to wait until the room is finished..
Are you asking about how the amp was optimized for the Denon's output voltage?

@boXem can configure the input stage of his A series amp for you during assembly.

IIRC, the standard high gain setting on mine was going to be 2V (low gain 4V) and that can be matched to extract the 3db more gain from the amp module with our AVRs. I paid a little extra to keep the low gain setting at 4v (instead of 2.8v) to have a better match with higher pre-out voltage stereo pre-amps.
 
If it was me I would start with one of these :

One of these to clean up the aux power from the supply:


And a bunch of opamps. Along with an APx555. My goal would be to exceed the performance of the amp module in the input stage.
Designers usually start a simulation SW before investing 35k in a measurement rig. This allows to check how realistic the requirements are...
 
Simple opamp based buffers are so trivial to implement. It a kindergarten level circuit. One would need to be severely incompetent to mess it up. However spending $35k on an APx555 or renting one is the only way to verify the final performance of the buffer+amp module when dealing with in excess of -120dB THD+N.
According to it's datasheet, the typical 5W SINAD for the 1ET6525SA is 116.1 dB. If we want to keep the performance almost untouched, let's consider that we allow no more than 0.5 dB SINAD degradation. THD being far below noise with these amps, that means that the target noise for the amp would be 7.4 uV unweighted.
That means that the buffer noise must be below 2.4 0.58 uV unweighted.
To have an amplifier with 26.5 dB gain, we need 14.2 dB gain at buffer level.
Since you passed all kindergarten grades with flying colors, could you please show us preschoolers the schematic of a differential input stage with 14.2 dB gain and less than 2.4 0.58 uV unweighted noise, at least in theory.
Edit, I forgot that the buffer noise was amplified by 12.3 dB.
 
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Designing an input gain stage with the constraints of low noise and maintaining SFDR isn't trivial - given the amp's final output power requirements with a SINAD exceeding 100 dB. That too given the price of these amps in the range of $500-$800/channel.
 
Whats harder designing the 1ET6525SA, or an input buffer for it?
Obviously the Purify module, but implementation will vary between DIY and production. If you can get the required output power, gain and a SINAD > 100 dB with an additional 6-9 dB requires a bit of work.
 
Simple opamp based buffers are so trivial to implement. It a kindergarten level circuit. One would need to be severely incompetent to mess it up. However spending $35k on an APx555 or renting one is the only way to verify the final performance of the buffer+amp module when dealing with in excess of -120dB THD+N.
You obviously went to a much better kindergarten than I or any of the engineers with whom I worked for decades designing state of the art circuits. Achieving >100 dB dynamic range, let alone 120~140 dB, requires a lot more than throwing an op-amp on a board. Op-amps themselves have quirks that may not be obvious until you work with them a bit, especially for high dynamic range circuits. Then there is implementation... Seemingly trivial things like guard rings (which may make things better or worse), placement and routing of decoupling and signal lines, shielding, proper component choice for coupling and decoupling caps and other passive components, etc. depends upon the application and throwing an eval board in the box (or even copying the layout) will not always work.

But thanks for trivializing my career (and all the other great designers who failed kindergarten and learned in the field).
 
On a difficulty scale of 1-10, if we put the Purifi module at 10, a low noise input buffer for it would sit probably around 0.5.
The Purifi modules are being mass produced for many different implementations. If you're building production amps, you want to get a reliable input gain stage design which can go into production. This is non trivial, but there are a fair amount of DIY implementations that look good and you can build a nice 2-channel Purifi amp for >$3,000.
 
Well I find high speed digital multi-layer boards far more difficult than simple analog circuits. I’ve had to redo a few of them
Depends on your requirements of frequency range, noise, dynamic range and required gain. They can become difficult. Ask NG or Raytheon when they do radar or EW amplifier designs for aircraft and ships. Those analog circuits can put noise on digital circuits manifesting in strange results.
 
Well I find high speed digital multi-layer boards far more difficult than simple analog circuits. I’ve had to redo a few of them
Care to enlighten us as to why you came here? Its looking more and more like its to goad existing members in the amp business.

If it is, just move on. If its something else I am all ears.

Thanks
 
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