Purifi class-D amplifiers

[Jonasz]

Thank you jaytor!
Valuable information when trying to decide what to build. I don't need a lot of power either so there's lot of stuff to choose from but hard to listen before building.

[jaytor]

The Neurochrome amp works better in my system. It has considerably more detail and images a bit better. I cross over to an active servo sub at about 70Hz, so can't really comment on the low bass.

I also have a Parasound JC5 and I think the Neurochrome is pretty comparable (although obviously much less power), while the lack of detail in the F5T compared to the JC5 was very noticable.

I have long balanced connections between my preamp and monoblocks, so I built the F5T with a Jensen input transformer to convert balanced to single ended. This may be contributing to the reduced detail. At some point, I'm going to rebuild these amps. I may just replace the transformer with an op amp based input buffer, but I've also been thinking about trying to do my own design using a single-ended class A output stage at lower voltage. My speakers are fairly efficient (93db/w) so I don't need a ton of power.

[Jonasz]

Can't answer your question but do you prefer the FW or the Neurochrome and why?

[jaytor]

Hi folks. This is my first post in this forum. I've been an audiophile for about 45 years and a home theater enthusiast for 30. After a 35 year hiatus from DIY, I've gotten back into building some of my own gear. So far in the past year I've built a pair of GR-Research NX-Otica speakers, a pair of triple stack open baffle servo subwoofers, a pair of First Watt F5 Turbo monoblocks, and a pair of Neurochrome Modulus-286 monoblocks.

I'm almost done with a new preamp that uses a Khozmo balanced relay-based stepped attenuator with OLED display and some boards from AMB Labs.

And the reason I'm posting here - I've started working on a pair of Purifi module monoblocks. I'm building a linear power supply and have a couple extra features like audio-sense power-on and a peak power meter. I'm working on figuring out what to do for the input buffer. I think I'm going to start with the Neurochrome input board as a baseline, but plan to build a couple of additional buffers using custom PCBs. I am planning to build a tube based design, but am also considering something similar to the WHAMMY design that @ergo has described above.

@ergo - do you have any more thoughts on using the WHAMMY after a few more months of listening? What opamp did you settle on to drive the MOSFETS?

Thanks,
Jay

[Evil Twin]

LLC SMPS Development platform PCBs

This is for Sven, because I could not attach images to a PM message. Discussion related to PuriFi.

[ergo]

And last two



and a plot from about 60mW to 100W

[ergo]

On electronics side - I originally had the Khomo volume and WHAMMY boards isolated from the ground with non conductive spacers. The XLR cable ground was connected to enclosure at the point of input XLR sockets, then went to Khomo relay volume and from there to WHAMMY and from WHAMMY to Purifi input that is again connected to enclosure ground firmly.

The result did not look bad when volume was at Max, but if I decreased it to 30 (which is moderate listening level) it looked problematic.



So then onto reading Bruno Butzeys article G word.

So onto making my amp from left image to right image concept






And not the spectrum is super clean.... and remains as clean down to lowest volume levels



I've never had a power amp that measures like this

[ergo]

The front panel looks very nice and the dot matrix display is super cool through the tinted glass...

[ergo]

I have not had time to post, but a lot of work has been done after last update.

I received the Khomo R2R relay volume and I'm very happy with it. Very nice engineering for affordable price.



So next step was to mill a suitable cavity and window into the Purifi enclosure front. As I do have a 3D printer also it seemed easier to go the easy route and make 3D printed holders attached with hot glue instead of over engineering and threading the aluminium etc.



I did use a bit of over engineering for mounting the relay board. I had some old rotating hard drive "decoupler rubber grommits". So the relay boards got attached with those to avoid the relay click transferring into the enclosure.



Khomo board inplace before WHAMMY



And the final view..... the case that originally seemed very big indeed is now full of 'stuff'

[ergo]

mocenigo, your description of a change in sound does sound similar to what we have experienced with EVAL1 vs WHAMMY.

My build is still not done, but some progress is made...

On Monday I should get the Mean Well AC/DC adapters and also a kit from Khozmo in Poland to solve the volume control.
It was hard to decide what to choose. I did want a R2R relay based volume. Originally I did build the back panel holes for BPBP preamp which would have that. But as noted before the listening experiments showed it to be a degradation even when compered to lowering the volume from PC and thus potentially losing some bits. I then e-mailed Khozmo and it turns out they have more options available compared to what is up on the website. So below is an image of what I'm expecting now.

At first I planned to put the two WHAMMY modules on top of each other... that then makes it hard to swap out opamps etc. So I printed two stands for them and listed them up. That makes enough room for both of them side by side and the coming volume control boards can hopefully fit below these.

When I bought the case I chose the deepest one and in beginning there seemed to be loads of room left over. Seems I'm now able to fill it easily and parts even on multiple layers.

[mocenigo]

What I was suspicious of was a use case where one has only the "PURIFI 1ET400A / HYPEX NC500 INPUT BUFFER" - as is, we do not yet have user feedback on that scenario it seems.
[ATTACH=CONFIG]30130[/ATTACH]

The sound with just the input buffer of the Neurochrome adapter board is a bit laid back and less dynamic than with the Neurochrome Universal Buffer, but still with an edge over the Purifi FE02 board in the EVAL1 kit in clarity. I do not like the sound of the EVAL1 kit that much, relatively speaking. Absolutely speaking it was great, and better than my previous NC500 based monoblocks with Sonic Imagery discrete opamps - the main difference being in the highs, so smooth that it was closer to vacuum tube ideal. But with the Neurochrome Buffer the bass becomes even tighter and the plasticity of the soundstage (how well the sound sources are modeled and the layering is rendered) just blossoms. The sound now, with the best recordings, is even eerie, like watching a 60fps movie –*nearly disturbing, because we are used to the defects of a lower frame rate.

Most people would probably not even notice the difference between the three buffers with decently sensitive speakers. But in my case, with horn loaded compression drivers and highly sensitive woofers downstream, and a Soekris DAC1541 upstream, all balanced connections, I can say I am very happy with the outcome.

[ergo]

Aha, your comments confirm what I was thinking I saw from the pictures - you essentially bypass the LM4562 opamp on the "PURIFI 1ET400A / HYPEX NC500 INPUT BUFFER" and instead the driving of the Purifi inputs is on the shoulders of LM49724 on "UNIVERSAL BUFFER". That chip has a much more capable output with +/-80mA instead of the +/-26mA specified for LM4562. So it is possible we get to similar outcome with your scenario versus WHAMMY.

What I was suspicious of was a use case where one has only the "PURIFI 1ET400A / HYPEX NC500 INPUT BUFFER" - as is, we do not yet have user feedback on that scenario it seems.

Anyhow, the Neurochrome buffer sure is nice small and easy to set up compared to all the complexity I'm trying to go through. Unless one has dual power supplies there is still a bit a question how exactly is the best way to split the power between the two modules. I see that you did it about mid way the cables between the modules and PS. And for Buffer lower voltage supply the ground split at the regulator out in your case.
Without measuring it it will be hard to tell if that can create some small ground loops or hum. But if you don't hear any than you were probably lucky and it is good as is.

[mocenigo]

I have a Soekris DAC / Bruno Butzey's Balanced Pre project that I've also listened with the Purifi. That Balanced Pre uses the same LM4562 opamp in all stages including the output buffer. Power to the BPBP module is provided by SilentSwitcher. Both me and my friend found that sounding inferior to the WHAMMY buffer doing the same function. Interestingly it was not only low end control but also the depth of the sound stage and sort of 'air' that was missing in BPBP. At the time of listening the power supply for both cases was the SilentSwitcher module.

The Neurochrome is a different circuit of course with only the opamp being the same (and there is only 1 in signal path instead of 3 in BPBP). So it is sure possible that it achieves a different result. It would be kind of interesting to get two modules and try them out in apples to apples comparison, but for me being in EU it'll probably cost quite a bit more due to +20% VAT on modules + shipping.

***
I am making some progress on finalizing the WHAMMY based solution too. I had bought some Jung/Didden Super Regulator PCB-s times ago for ... I don't even remember what for. Anyhow, this project was a motivation enough to finish those. So the plan is now to have a MEAN WELL IRM-20-24 AC/DC unit supplying each positive and negative power rail for the buffers and each channels gets their own. So basically a dual mono build from buffer power supply perspective. Waiting on MeanWells to com in to put it all in action.

[ATTACH=CONFIG]30129[/ATTACH]

ergo, I do not know the BPBP, and I am VERY intrigued by what you are doing. I can tell you this: the Neurochrome Universal Buffer sounds incredible. You really have the feeling that "something opaque" has been removed from the systemm. The Neurochrome Universal Buffer into Neurochrome Input Boards with buffer bypassed and Hypex regs on board into 1ET400A is by far the best amplifier I have listened so far - in particular among those with my source and speakers. At home I have auditioned Abrahamsen (in other words, Electrocompaniet), Lavardin IS, a Naim NAC 552 + NAP 500 DR from a neighbour that went back home saddled, NAP 150, and Apollon NC500-based amps with Sonic Imagery opamps. Source is a Soekris 1541 (I am sure you have a good idea how it sounds) and the speakers you can see here. Your DIY skills surpass mine, but I would like to initiate an exchange of information with you. I am sure I can learn a lot.

Best, and stay safe, sane, healthy.

(reminder that my build can be seen here)

[ergo]

I have a Soekris DAC / Bruno Butzey's Balanced Pre project that I've also listened with the Purifi. That Balanced Pre uses the same LM4562 opamp in all stages including the output buffer. Power to the BPBP module is provided by SilentSwitcher. Both me and my friend found that sounding inferior to the WHAMMY buffer doing the same function. Interestingly it was not only low end control but also the depth of the sound stage and sort of 'air' that was missing in BPBP. At the time of listening the power supply for both cases was the SilentSwitcher module.

The Neurochrome is a different circuit of course with only the opamp being the same (and there is only 1 in signal path instead of 3 in BPBP). So it is sure possible that it achieves a different result. It would be kind of interesting to get two modules and try them out in apples to apples comparison, but for me being in EU it'll probably cost quite a bit more due to +20% VAT on modules + shipping.

***
I am making some progress on finalizing the WHAMMY based solution too. I had bought some Jung/Didden Super Regulator PCB-s times ago for ... I don't even remember what for. Anyhow, this project was a motivation enough to finish those. So the plan is now to have a MEAN WELL IRM-20-24 AC/DC unit supplying each positive and negative power rail for the buffers and each channels gets their own. So basically a dual mono build from buffer power supply perspective. Waiting on MeanWells to com in to put it all in action.

[theSven]

Ergo, What do you think about that new board that neurochrome is offering for the card instead of needing the evaluation board? Would you still use the buffer with that other card setup?

[mocenigo]

And now the amp has new connection boards by Neurochrome! In the following thread at DIYaudio I share my experiences.

https://www.diyaudio.com/forums/vend...ml#post6133929

High resolution pics:

[JonMarsh]

Hey all. Tom has made a a buffer specifically for the 1ET400A and NC500. Plug and play with the SMPS1200.



https://www.diyaudio.com/forums/vend...ml#post6127335




I thought y'all would find this interesting.

Cheers

Peter

Very interesting thread, thanks for the link!

[Supernova]

Hey all. Tom has made a a buffer specifically for the 1ET400A and NC500. Plug and play with the SMPS1200.



https://www.diyaudio.com/forums/vend...ml#post6127335




I thought y'all would find this interesting.

Cheers

Peter

[theSven]

Thank you Ergo. As the days get closer to my Calliope being ready to pick up from Steve I want to start looking into building a 2 channel amp for these. Longer term I want to build the Ardent D’s, but it gets me closer to my goals for the basement project.

[Evil Twin]

Slow work always takes time, and some processes cannot be rushed...

[ergo]

The case is from Modushop in Italy

https://modushop.biz/site/

I ordered also an extra 4mm front panel and then cut it to dimensions on a small bandsaw to be used as the separator internal wall between PS and the amp.


Meanwhile there was also progress and I got 2xWHAMMY modules ready for balanced buffer operation. I was running a single module with Jan Diddens SilentSwitcher regulator, but with 150mA load capability it was not enough for 2 modules. So upgrade to SuperTeddyReg-s was done feed by two 24V AC to DC modules by MeanWell.

I finished those just before my trip to US and my friend was listening to them meanwhile. Now I'm back but he is on trip, so I still have not yet heard these myself. According to him though there was another small incremental improvement in driving the Purifi with true balanced signal (from Denafrips Venus DAC)

I also replaced the heatsinks on the modules for less tall, so that it would be ready to fit the 80mm height I have inside the enclosure.

[theSven]

What super regulated linear power supplies are you using? Where did you order your case from?

[ergo]

I have two WHAMMY modules up and running now since weekend. Plan is to try to run one as a balanced buffer for one channel and the other for the other channel. I will power them from MEAN WELL AC/DC 24V/900mA supplies -> Super TeddyReg regulators. Each WHAMMY MOSFET stage runs at 37mA class-A at moment, but I can increase that once I move to TeddyRegs instead of the SilentSwitchers I used now that have a total load of 150mA. Will be seen if they are 'symmetrical enough' to get some more benefit out of that than we get with SE drive already.

Why I did measure the impedance in the first place was that I did build the WHAMMY boards so that one can extract the signal also after the opamp. So we did try to drive the Purifi also from opamps direct versus the MOSFET class-A stage in between. Surprisingly even the opamps that have ample current output capability of 50+mA seem to do better with the extra power stage in between. And it's not only the bass control, but also the depth of the sound stage for example. So pretty interesting and not easy for me to grasp either as I would also like to know what it is that makes up that difference and how could I measure it out or put numbers to it

[5th element]

I wouldn't call 1.8k low impedance but now you've mentioned it some driver stages would have trouble with it.

The Purifi modules have something like 12dB of gain on their own. To reach maximum amplifier output you'd need a buffer that can swing considerable voltage with, potentially, decent capacitive load drive for the best linearity. Assuming you're only playing with a single ended 2VRMS source.

Most modern, high performance, op amps can do this, but it's certainly not a universal trait. Nor could you opamp roll your favourite of the month into the output of the buffer and assume it would be happy.

Of course the best solution would be driving the inputs of the Purifi module directly with a capable balanced source. This would give you the lowest noise too.

[JonMarsh]

As usual, tells the story about why low driving impedance is desirable... and tells it in a very systematic way.

[5th element]

So 1.58k up until the low pass on the input kicks in it seems.

[ergo]

I finally got around to building a cable for the purpose of measuring the input impedance of the Purifi module (EVK buffer bypassed)

I did build a dummy with 2k2 resistors in each leg and calibrated the series resistor with that... so result should be accurate. And it is 1.58kOhm over most of the audio range. It is close to what is expected. I just wanted to verify it does not change to lower impedance at some range as datasheet gives only one number and did not specific at what frequency. Datasheet does say 2.2k, but I did measure less. There might be a mistake in my method, but at least today I don't see it.

[ergo]

mocenigo - nice progress there and I see the amp has found a new home in a nice case too :T

I now have enough parts to solder up 3 more WHAMMY boards. That will allow us to test out the balanced drive throughout and then decide if we stick to WHAMMY as a buffer or experiment some more. My friend just got some OPA1656 for WHAMMY and says he likes these. He also listened to Burson V6 Classic, likes the bass a lot but says the high are not to his liking. I have not heard either of those yet. So I guess that is the plus in WHAMMY that it is easy to keep rolling the opamps to try find the 'best match' to taste and rest of the system. Measurement wise I suspect those would not look very different as newer opamps measure pretty good generally.

The Neurochrome Universal buffer looks pretty good and interesting indeed. I will be close enough to Canada week after next, so I was considering ordering one to try out as well.

[mocenigo]

The 'evil buffer' refers to schematic Evil Twin posted a page ago here. So I guess my poor attempt to be funny.

Ah ok, understood. Well, it seems that Tom Christiansen's new Universal Buffer goes already in that direction

"the slow diyer" - I don't have nothing against being called slow as long as it includes 'diyer' also in the title Goal is not so much to whip up something fast but rather to learn, gain experience and get things done eventually and as good as possible.

Well, there is a blog by "theslowdiyer" that was building the ACP+, WHAMMY, at the same time, and I thought it may have been you - but then why is this guy no reporting about the combinations of these

***
As for progress - there is some. Yesterday we had a listening session comparing my Soekris 1021 DAC to Denafrips Venus that my friend just got yesterday. Perhaps it will change a bit as it burns in, but initial impressions were good.
We tried with Soekris and Venus DAC driving the Purifi direct (EVK buffer bypassed). Here the Venus can clearly do a better job and Soekris struggles and does not sound as good as when WHAMMY is between the DAC-s and the Purifi. Overall it still seems that having the WHAMMY in path also does add a bit of ease to Venus presentation too. Overall these DAC-s sounded similar in nature. Neither of us felt that there is any big 'difference in sound character'. Venus did seem to have a bit better control of bass and bass presence.

We also tried a new opamp in WHAMMY - OPA1622 instead of the OPA2134. Similar feeling - very similar character overall, just a bit more air and freedom perhaps, but would take longer listening to really be able to tell one over the other.

Next up is soldering up two WHAMMY modules, so we could run full balanced signal chain. All listening this far has been by converting DAC out to single end and then feeding Purifi with single end signal (with cables built per Hypex documentation recommendations).

I also bought a pair of used Super TeddyReg regulators - so there will be a chance to compare those against the SilentSwitcher in use now.

I am very, very curious, keep us posted.

In the meantime, this is my build: Connex SMPS800RE regulated power supply at 54V (max power over 8ohm 155W), Neurochrome Universal Buffer, two superregulated power supplies. Sounds heavenly. It is progressing, now it has a case!

[Evil Twin]

As always, your detailed comments are interesting and appreciated, Ergo.

I have a well known preference for R2R ladder DACs, and have a Soekris DAC1101 (for desktop and portable applications- bus powered, no usage issues whether in a Tie Fighter or Imperial Shuttle) and the "table top/system rack" DAC1541.

The 1021 board has an output impedance of about 640 ohms, which would lead me to expect it will do better with a high input impedance preamplifier, rather than driving a power amp direct. Only with the most recent TotalDAC have I seen a useful capability for direct drive, and I still find that I prefer preamp based operation- with the right preamp selection.

At some point I should do bench and listening comparisons, including against the Denfrips Terminator with the firmware upgrade, but for the immediate future (3-4 months) speaker development efforts will take precedence.

I have a planned bionic upgrade later this year which may give me more time in my personal laboratory for such explorations. Palpatine did not do a very thorough job for me... and that was many years ago.

[ergo]

The 'evil buffer' refers to schematic Evil Twin posted a page ago here. So I guess my poor attempt to be funny.

"the slow diyer" - I don't have nothing against being called slow as long as it includes 'diyer' also in the title Goal is not so much to whip up something fast but rather to learn, gain experience and get things done eventually and as good as possible.

***
As for progress - there is some. Yesterday we had a listening session comparing my Soekris 1021 DAC to Denafrips Venus that my friend just got yesterday. Perhaps it will change a bit as it burns in, but initial impressions were good.
We tried with Soekris and Venus DAC driving the Purifi direct (EVK buffer bypassed). Here the Venus can clearly do a better job and Soekris struggles and does not sound as good as when WHAMMY is between the DAC-s and the Purifi. Overall it still seems that having the WHAMMY in path also does add a bit of ease to Venus presentation too. Overall these DAC-s sounded similar in nature. Neither of us felt that there is any big 'difference in sound character'. Venus did seem to have a bit better control of bass and bass presence.

We also tried a new opamp in WHAMMY - OPA1622 instead of the OPA2134. Similar feeling - very similar character overall, just a bit more air and freedom perhaps, but would take longer listening to really be able to tell one over the other.

Next up is soldering up two WHAMMY modules, so we could run full balanced signal chain. All listening this far has been by converting DAC out to single end and then feeding Purifi with single end signal (with cables built per Hypex documentation recommendations).

I also bought a pair of used Super TeddyReg regulators - so there will be a chance to compare those against the SilentSwitcher in use now.

[mocenigo]

I might yet to go for 'Evil buffer' as well - just to get to hear what a stage that should measure super well can do and how it sound compared to these where one still can measure some distortion and put a for example '2nd harmonic dominated distortion' labels on them

Hello, what is the "evil buffer"? Also, are you "the slow diyer"?

[mocenigo]

Hello, new member here. I have been building my own Purifi+Neurochrome based amp for some time. Here's some pics.

I am using:
- The EVAL1 kit with the buffer bypassed;
- A Neurochrome Universal Buffer (also very, very revealing, configured for a 7.3 Db gain);
- Connex SMPS800re power supply;
- A +-18V superregulated linear power supply for the modulators; and
- A +-15V superregulated linear power supply for the Neurochrome Universal Buffer.

So far, it sounds just great, well above and beyond my previous NC500 based monos (with SI 994 opamps in the buffer).

[ergo]

I did indeed do just that - meaning verified all step by step with multimeter and used soldered connections instead of the small pin connectors for other circuits etc to make sure they don't come loose and I would not have to go too close to the 120V in end.

Yesterday we did some listening too. This this time the WHAMMY (opamp + complementary MOSFET power stage) and ACP+ (JFET / MOSFET based discrete opamp with very high bias). The impression after an hour or so listening was a small positive bias in WHAMMY direction. ACP+ seemed to add something very nice and pleasant to female vocals, but then listening through the to other instruments then the overall clarity and soundstage seemed better with WHAMMY. Due to BOZOS needing a lot of care with it's high supplies we did not get around to listening to that just yet.

Anyhow - it is becoming more clear every time we listen that the Purifi power stage is very revealing indeed. On the setup I had some years ago base on 'normal' mid class AB intergrated amps the two would probably have sounded pretty much same good. Being able to hear the small differences they have I think speaks about the quality of the amp.

It's very fun to do these experiments when the differences of this level can be heard, so that's why I guess I'm also not in super hurry to wrap it up and make the system static yet.

I might yet to go for 'Evil buffer' as well - just to get to hear what a stage that should measure super well can do and how it sound compared to these where one still can measure some distortion and put a for example '2nd harmonic dominated distortion' labels on them

[Norm]

My dear ergo, I am with you in spirit as the leads from series connected bench supplies to device under test are checked, double checked, and checked once more before power is applied. With 140 or 150 mA showing on all the current readouts one is reminded the esteemed Mr Pass does like his bias, and why a line buffer has such big heat sinks.

[ergo]

Generating the +/-60V supplies for testing of Pass BOZOS takes some gear and effort

But it works... though from measurement result does not look too promising. But will be interesting to hear that type of distortion profile (dominated by 3rd harmonic as opposed to mostly 2nd for ACP+)

[Evil Twin]

****

BTW there was an interesting offline tip from Purifi. They have found that magnetic speaker terminals can influence the performance of this amp quite a bit - "Just a single magnetic washer increased the 6kHz distortion by 15dB. removing it made wonders to the sound." We checked ours - My amp had Hypex branded clear speaker terminals - those turned out to be non magnetic. My friends amp had other terminals where both washers and nuts were magnetic. So that could have been a partial influence in our 'cap upgraded Purifi vs stock Purifi' listening test too.

****
[ATTACH=CONFIG]29936[/ATTACH]

This is no surprise either. In developing the Ayre Acoustics equipment, Charles Hansen found that any magnetic type materials in the signal path such as binding posts, resistors, etc, were audible and often measurable. Nickel especially seems a problem when it is asked to be a conductor... but in your friend's case, it's most likely that they are simple plated steel washers.


And yes, slow work takes time seems to be a governing point of existence, especially when the work is detailed and demanding...

[ergo]

Yes, sorry indeed. Goes under Jon's saying that "Slow work takes time".... but there has been a progress behind the curtain.

Had some trouble getting the Pass's ACP+ going. Turned out to be my own mistake from translating a schematic into PCB, so one trace was a bit wrong. Now it works and input dif pair got tuned for lowest THD also over weekend.

I also got the BOZOS soldered up, but not power up yet as my lab power supply seems to need some attention of it's own and one polarity is not working...

Anyhow, I'm quite hopeful that we can put these 3 pre-stages side by side this week for listening and then I'll report back.


****

BTW there was an interesting offline tip from Purifi. They have found that magnetic speaker terminals can influence the performance of this amp quite a bit - "Just a single magnetic washer increased the 6kHz distortion by 15dB. removing it made wonders to the sound." We checked ours - My amp had Hypex branded clear speaker terminals - those turned out to be non magnetic. My friends amp had other terminals where both washers and nuts were magnetic. So that could have been a partial influence in our 'cap upgraded Purifi vs stock Purifi' listening test too.

****

[Evil Twin]

Ergo has impressions which he is cautious about sharing after testing out his current modifications- I will go so far as to say he is surprised, but also that I am not, based on experience derived from completely different circuits over 40 years ago.

I suggest a PM to him if you want more information before he has the confidence to post freely.

[kravi4ka]

@ergo - new impressions? Just silly, untrustworthy subjective impressions that would make you prefer one amp over the other?

[5th element]

Oh I know Jon I keep up to date with the reviews posted on Stereophile and find it saddening that so many expensive products are so poorly conceived.

Your inclusion of the transformer on the front end has actual engineering behind it and benefits that it can provide, so I'm certainly not bashing that aspect of it. I think it's a great idea should it be needed, but I would imagine that the instances where it is actually needed are few and far between. A transformer-less input stage can be designed with properties that will match and/or exceed the performance of the Purifi amplifier modules and going with a transformer would seem like a big step back. Then again if you like the sound that the transformer potentially introduces, that's an entirely different thing.

[Evil Twin]

So does hooking up the speakers to those amplifiers.

What is interesting is the difference in audibility of different effects, especially when they monotonically reduce in level.

This is a “design study” in progress that is taking far too long to complete. The potential benefits for the noise floor are also interesting...

To see real foolishness in action, I suggest reading the February issue of Stereophile and reviewing the measurements for Audi Research, D’Agostino, Pass, and Schitt.

[5th element]

Not to point out the obvious but using the transformer on the input will destroy the immaculate linearity of the purifi amplifiers and all the work Bruno put in to better the ncore. Yes they help with regards to some issues but they should only be used if these issues are actually issues to begin with.

[Evil Twin]

What would be a good place to order these in US (seems they are not available in big ones like Mouser and Digikey and no longer in PartsExpress). I'm coming over to US in end of February and it would be right time to stock up. I suspect these will be harder to get in Europe.

**
Altium is the 'real tool' for sure. I'm getting by with a 50EUR tool called SprintLayout for these small projects where a tie to circuit diagram is not a must. I did buy a perpetual license to Eagle also before they went all subscription, but I find the SprintLayout to be what the name says - so easy and fast that I typically have a board done in same time it would take to figure out the circuit and part match in Eagle.

I, too, have Eagle PCB, on the Mac ("think differently" encompasses a wide range of values...) but never found it particularly pleasant to work with, and creating and managing component libraries is decidedly tedious and restrictive, and limiting in scope in Eagle. The Imperium has switched to a networked license model, and of course, never has enough licenses to check out, as I found when trying to train my Sith apprentice... we never could successfully check out a license for her on her work computer. With my own license, I can install on whatever systems are needed, as long as I only run on one at a time...

[Evil Twin]

Markertek is the distributor I use, though one can order direct from Jensen, the pricing is higher. Markertek is a good distributor for many pro sound and studio oriented items, even items like the Mutec MC3+ digital data and clock reclocker.

Yes, I think this is good value component, all matters weighed and considered.