Purifi 1ET400A new range of class D amp modules

[March Audio]

8 minutes ago, cafe67 said:

They usually go the same way as power cable threads

aaaahhhh I see   

 

Hopefully we can have some intelligent discussion about it instead of throwing rocks from different camps.

 

I hope that the technical info above demonstrates some good reasons why a tube amp may well sound different to a solid state (be it A/B or class D). Note I said "different" not "better".

Edited September 3, 2019 by March Audio

[Ittaku]

Good old measurements for comparison eh? BTW the 150 isn't the 150SE, and the 150SE isn't the 250SE which was used in the comparison. Nonetheless, I can recite measurements from 1980s amplifiers that look spectacular, but sound terrible. Enjoy your measurements, I'll listen to my amps instead.

[ghost4man]

7 hours ago, Ittaku said:

Good old measurements for comparison eh? BTW the 150 isn't the 150SE, and the 150SE isn't the 250SE which was used in the comparison. Nonetheless, I can recite measurements from 1980s amplifiers that look spectacular, but sound terrible. Enjoy your measurements, I'll listen to my amps instead.

Setting this to one side my view has always been to set a blind test. 

 

Benchmarking does have value from a technical perspective but I'm inclined to temper that with a listening test rather than engage in an endless pursuit for perfect graphs. 

 

As Trevor from Rage Audio once said to me, distortion figures are a good example of chasing more zeroes after the decimal point but would a figure of say 3% be indicative of distortion that can actually be picked up by the human ear. Hence the value of the blind test. 

[andyr]

As it seems my reply to your challenge (of comparing the sound of your amp to any other amp), Alan, has set up this measurement fracas, I believe I owe you a response.

 

11 hours ago, March Audio said:

How did you conduct the comparison?

 

Was it blind?

 

How did you set volume levels?

 

what was the class D amp? They aren't all created equal.

 

The listening was not done blind - nor even on the same day.  I don't know what the D class amp was - but I think Con mentioned it earlier?  I'm well aware that all amps are not created equal but I know Con wouldn't have just gone out and bought the cheapest D class amp he could find.

 

Quote

What does "delivered more" mean?  Did have a "sound"? Out of curiousity did you find the class D a little bland in comparison?

 

Mainly, delivered more air around the instruments.  If you call this "having a sound" then:

1. yes, the AR amps had a sound.
2. and, yes, this made them more interesting to listen to than the D class amp.
3. which means, yes, the D class amp was (more than a little!) bland, by comparison.

 

Quote

 There is actually an issue here.  Frankly I dont trust a tube amplifier not to have a discernible "character" due to technical deficiencies (distortion and load dependant frequency response issues) which does cloud things somewhat.

 

I don't see this as a problem?  Yes, tube amps have a 'character'; so do, say, 1970s Japanese ss amps (with 0.0000000001% THD, from massive amounts of global NFB)! 

 

Quote

I am happy to compare the Purifi or Hypex amps to any other amp; it simply does not follow that more expensive equal better Im afraid.

 

Absolootely! 

 

Quote

However it does seem to make more sense to me to compare items with a broadly similar price range. 

 

Agreed - but you left this bit out, in your original challenge. 

 

Quote

I will try to get a test set up.  Basically you will need to identify the respective amps with different tracks consistently.  It will of course be blind.

 

You are going to record some tracks, for us to download and listen to on our PCs (with their tinny little speakers)?

 

And when you say "identify the respective amps " - do you mean:

• identify - name! - the amps?
• or simply define them as tube/Class D/Class A/Class AB?

 

11 hours ago, March Audio said:

If you want to see what I mean above re the technical deficiencies, whilst I haven't found 250 measurements I have found 150 measurements.  There is enough going on there to make it have a "sound".  Exactly as I suspected and all too common with tube amps.

 

What do you measure, to illustrate the amount of 'air around instruments ' that an amplifier delivers?

 

Quote

 

 

 

You need to provide a key for each graph.  For instance, in the last graph there are 5 different-coloured curves; what does each represent?

 

Regards,

Andy

 

Edited September 3, 2019 by andyr

[March Audio]

20 minutes ago, ghost4man said:

Setting this to one side my view has always been to set a blind test. 

 

Benchmarking does have value from a technical perspective but I'm inclined to temper that with a listening test rather than engage in an endless pursuit for perfect graphs. 

 

As Trevor from Rage Audio once said to me, distortion figures are a good example of chasing more zeroes after the decimal point but would a figure of say 3% be indicative of distortion that can actually be picked up by the human ear. Hence the value of the blind test. 

Whilst I agree to an extent; there is a point when distortion, noise etc become inaudible, the performance we see above of the 150 is very much in territory of audible. 1% thd is audible.  It has a spread of IMD products up to - 50dB.  The variable frequency respose is quite audible.  I would expect that amp to sound different compared to another good performing one. 

 

Audio is engineering. There isn't some kind of magic going on that makes any particular amp special. I don't have an issue if people like the subjective effects of the deficiencies seen above, but it's probably cheaper to buy a fuzz box and a graphic equaliser.

 

I have performed a number of blind tests with groups some quite ardent audiophiles.  They have equipment along the lines of Dave, PS audio and audio physics.   Every time I perform tests blind and volume matched the massive differences they claimed to hear evaporate or are suddenly minimal /trivial.  (I'm excluding speakers where again differences can be huge). 

[March Audio]

4 hours ago, andyr said:

As it seems my reply to your challenge (of comparing the sound of your amp to any other amp), Alan, has set up this measurement fracas, I believe I owe you a response.

 

 

The listening was not done blind - nor even on the same day.  I don't know what the D class amp was - but I think Con mentioned it earlier?  I'm well aware that all amps are not created equal but I know Con wouldn't have just gone out and bought the cheapest D class amp he could find.

 

 

Mainly, delivered more air around the instruments.  If you call this "having a sound" then:

1. yes, the AR amps had a sound.
2. and, yes, this made them more interesting to listen to than the D class amp.
3. which means, yes, the D class amp was (more than a little!) bland, by comparison.

 

 

I don't see this as a problem?  Yes, tube amps have a 'character'; so do, say, 1970s Japanese ss amps (with 0.0000000001% THD, from massive amounts of global NFB)! 

 

 

Absolootely! 

 

 

Agreed - but you left this bit out, in your original challenge. 

 

 

You are going to record some tracks, for us to download and listen to on our PCs (with their tinny little speakers)?

 

And when you say "identify the respective amps " - do you mean:

• identify - name! - the amps?
• or simply define them as tube/Class D/Class A/Class AB?

 

 

What do you measure, to illustrate the amount of 'air around instruments ' that an amplifier delivers?

 

 

You need to provide a key for each graph.  For instance, in the last graph there are 5 different-coloured curves; what does each represent?

 

Regards,

Andy

 

Andy, 

 

With respect if the test wasn't performed blind you will be hopelessly biased.  If it wasn't level matched within 0.1dB you will draw incorrect conclusions.   Listening on different days...... Come on.....you are not being serious are you? . 

 

Your subjective comments above don't surprise me if we assume the 250 has similar performance problems to the 150.  Its coloured, not neutral and adds a whole bunch of spurious signals that aren't in the original music signal.  BTW good class d (like all things there is bad class d) doesn't sound bland, I deliberately used that term to see your response, it just sounds neutral, ie it doesn't have an overt "sound". 

 

"air", that's just a nebulous Audiophile term like PRAT.  Largely meaningless.  However one thing for sure is that the 150 above adds lot additional intermodulation tones.  What you see above should only show two signals, at 18 and 19 kHz.  The rest of the signals are created by the non linearity of the amplifier.  What this means is that with complex music signals the noise floor (well its not really the floor in this instance, the levels are massive) is going to filled with erroneous signals harmonically and a-harmonically related to the music. 

 

I suspect that's what you might call "air"

 

The test was intended to be performed live with visitors at the hifi show, so I'm not sure what you are referring to with recordings and tinny speakers. If the differences are significant people will be able to consistently pick out which amp is which when listening to a selection of tracks played on both.  However I will exclude an amp such as the 150 above for the reasons discussed here. 

 

Let me know which class d amp and we can look at it's performance. 

 

I linked to the Stereophile tests above so you can read all about it.  The frequency response graph lines are of different loads, the really wobbly one being of a speaker and not just a resistive loads.  Variations of well under 1dB are quite audible when spread over a frequency range. 

 

Basically that amp will sound different with every different speaker you attach it to. 

 

As I said above, I have no problem with people liking a sound, or the effect a particular product may have due to its technical deficiencies, but if so you probably will save a lot of money if you get a fuzz box and a graphic equaliser

 

Look, all I am saying here is that if the 250 performs like the 150 then it comes of no surprise to me that they sound different to other better technically performing amps. Personally I'm not looking for an amp that colours the sound, my experience is that the more neutral a system is, the better it sounds.  This is particularly pertinent with speakers where differences are large.  An understanding of the speaker measurements afforded to us by the work of Floyd Toole et al has moved us on greatly IMO. 

Edited September 4, 2019 by March Audio

[Ittaku]

29 minutes ago, March Audio said:

Let me know which class d amp and we can look at it's performance. 

I already said what it was above. Dual NC400 monoblocks.

[aussievintage]

On 02/09/2019 at 10:07 PM, andyr said:

Certainly!  But isn't that why Class D is popular ... you can get lots of watts for relatively little money?    Whether it sounds any good ... is the $64,000 question! 

A comparison point.  I compared my 2A3 SET amp to a cheap TK2050 (Tripath 50 watt amp/module).   I think on balance the Tripath is better.  It does most things better than the SET.  It's certainly cheaper.

 

I know neither amp is hi end, although some will argue a 2A3 SET  might be.

 

To answer the $64000 question at this level, yes it does sound good.

[andyr]

26 minutes ago, aussievintage said:

A comparison point.  I compared my 2A3 SET amp to a cheap TK2050 (Tripath 50 watt amp/module).   I think on balance the Tripath is better.  It does most things better than the SET.  It's certainly cheaper.

 

If this was driving your Osborn Ref Eclipses, av ... I'm not surprised! 

 

Andy

 

[March Audio]

56 minutes ago, Ittaku said:

I already said what it was above. Dual NC400 monoblocks.

Well they are great and I have owned a pair.  Although I would ask if they had an input RF filter? There is a potential issue if they don't. 

 

However I think generally I would just refer to my comments above, differences are readily explainable.   Although I do understand it may not quite be what you want to hear considering the price of the amps. 

 

However if you enjoy what it does then it's of no consequence. 

Edited September 4, 2019 by March Audio

[aussievintage]

23 minutes ago, andyr said:

 

If this was driving your Osborn Ref Eclipses, av ... I'm not surprised! 

 

Andy

 

Actually I have yet to connect the SET to them.   I am considering bi-amping - see    

 

[Guest deanB]

1 hour ago, March Audio said:

"air", that's just a nebulous Audiophile term like PRAT.  Largely meaningless. 

I do enjoy your complete lack of reverence for some of the audiophile twonk-speak. I have eventually realised the worthlessness of trying to grasp it's meaning.

I'm Class D curious but I really enjoy valve amp "colour". To get my bearings on what is neutral, I head up to @JDWest place every once in a while for a listen to the superior sound quality of his ATC actives and Mola Mola preamp.

This doesn't diminish the enjoyment I get from my system, it actually helps keep things in perspective.

I've used good ss amps (ATC and Bryston) but for my listening tastes, sooo many of my albums benefit from valve amplification.

38 minutes ago, March Audio said:

However if you enjoy what it does then it's of no consequence.

Spot on. But the myriad details of the hobby can prove too distracting for some.

[aussievintage]

3 minutes ago, deanB said:

I'm Class D curious but I really enjoy valve amp "colour".

I always use valve phono and line preamps with my Class D 

[Guest deanB]

1 minute ago, aussievintage said:

I always use valve phono and line preamps with my Class D 

Yes, I can't imagine not having a valve somewhere in my system ever.

[andyr]

3 hours ago, aussievintage said:

 

Actually I have yet to connect the SET to them.   I am considering bi-amping - see    

 

 

Aah, OK.    It seemed to me that a poor little SET just wouldn't have the grunt to drive your Osbornes - so no wonder the Tripath sounded better!

 

But to use it for 3.3kHz and upwards ... might do the trick! 

 

However, to do this (bi-amping), you need to actively bi-amp - which involves removing (or bypassing) Osborn's internal passive XO and using an active XO in its place.  Passive bi-amping - ie. still using the internal passive XO but removing the links and putting the SET on the tweeters and the Tripath on the woofers - strangely enough does not reduce the power draw on each amp.  (Counter-intuitive, I know!   ) 

 

But an active XO does - and in an active bi-amp scenario, a SET might conceivably handle your tweeters.  And the active XO will give you the ability to compensate for the different gains each amp might have.

 

Andy

 

[Ittaku]

4 hours ago, March Audio said:

 Although I do understand it may not quite be what you want to hear considering the price of the amps.

 Uh yeah I'm quite aware of how badly valve amps measure and how they add colouration, thank you very much.

 

Fortunately I have done a blind test comparing the two and they were light years apart, but I already mentioned this earlier. No I did NOT match them to 0.1dB because let's get a grip here, I was just doing a simple comparison at home with a friend for grins; not conducting a scientific experiment. Luckily the gain of both amps is very similar so the volume levels were closely matched enough.

Edited September 4, 2019 by Ittaku

[March Audio]

2 hours ago, Ittaku said:

 Uh yeah I'm quite aware of how badly valve amps measure and how they add colouration, thank you very much.

 

Fortunately I have done a blind test comparing the two and they were light years apart, but I already mentioned this earlier. No I did NOT match them to 0.1dB because let's get a grip here, I was just doing a simple comparison at home with a friend for grins; not conducting a scientific experiment. Luckily the gain of both amps is very similar so the volume levels were closely matched enough.

 

Well it wasnt me who started making noise about how much "better" they are...........thank you very much.

 

Well I think the term used was "how much more they delivered", which in one respect is actually quite accurate a description in terms of what they add which is not in the original signal.  Its of no surprise to me they would be identifiable in a blind test.

 

I have just been pointing out why they would most certainly sound different (including testing methodolgy), and no, not everyone is aware of the mechanisms as to why tube amps tend to sound different to solid state.  Generally they are not good reasons.

 

I guess there are some different definitions of "better" out there.

 

The gain of the 250 it specced at 25.5dB.  The NC400 can be up to 26.3dB.  Both will vary due to component tolerences and could easily be 1dB apart.  Thats not close enough.  0.1 dB.  Simply measure the voltage at the speaker terminals with a sine test signal.

Edited September 4, 2019 by March Audio

[Ittaku]

No thanks. You may not be satisfied with my methodology but considering I've even done a blind test of any sort, that sets me apart from more than 99% of the people who pay megabucks for equipment. I'm satisfied with my results. It's also why I spend very little on cables...

[andyr]

32 minutes ago, March Audio said:

 

I guess there are some different definitions of "better" out there.

 

 

I'm sure there are many differences in people's definitions of 'better', Alan! 

 

Mine is quite simple - and I suspect Con's is similar: if amp A grabs you and draws you into the music more than amp B does ... then amp A is better! 

 

(Note any concept of measurement is absent, here - it's simply about engagement !)

 

 

Andy

 

[andyr]

5 minutes ago, Ittaku said:

 

It's also why I spend very little on cables...

 

 

But Con ... you've never tried one of my cables! 

 

(Not that they are expensive.  )

 

Andy

 

[Ittaku]

5 minutes ago, andyr said:

 

But Con ... you've never tried one of my cables! 

 

(Not that they are expensive.  )

 

Andy

 

Well I spent more than yours cost... But proportionately only 0.5% of my budget. Analogue cables make a difference, they just don't make that much of a difference...

Edited September 4, 2019 by Ittaku

[March Audio]

8 minutes ago, andyr said:

 

I'm sure there are many differences in people's definitions of 'better', Alan! 

 

Mine is quite simple - and I suspect Con's is similar: if amp A grabs you and draws you into the music more than amp B does ... then amp A is better! 

 

(Note any concept of measurement is absent, here - it's simply about engagement !)

 

 

Andy

 

 

No issue with that as I have pointed out previously.

 

Measurement just allows you to be informed about whats going on.  It also allows you to move past the bias of sighted decision making.  There is no doubt in my mind that part of the decision making with this amp has been influenced by its brand, technology type (tubes) and price tag.

 

The implication there is an amplifier that doesnt significantly distort the signal cant or wont be engaging - thats something I do take issue with.

 

 

Edited September 4, 2019 by March Audio

[andyr]

1 minute ago, March Audio said:

 

Measurement just allows you to be informed about whats going on.

 

 

 Provided you know what you need to measure! 

 

You didn't think much of my concept of 'air' - but I sure do know when I hear it.

 

So, if measurement informs you what's going on ... if you have the situation where:

• amplifier A has the singer (in front of a band) in the plane of the speakers, but
• amplifier B projects her a few feet forwards of the speaker line

... what do you measure, to account for this difference in soundstage presentation?

 

Because I've experienced this situation.  Amplifier A was a Bryston AB amp - at least 100w (into 8 ohms); amplifier B was Hugh Dean's "Glass Harmony" - a SE ss amp which could deliver only about 18w.  Amplifier B just didn't have the output to drive the Dali speakers to their limit but it had it all over the Bryston, in terms of soundstage.

 

1 minute ago, March Audio said:

 

It also allows you to move past the bias of sighted decision making.  There is no doubt in my mind that part of the decision making with this amp has been influenced by its brand and price tag.

 

I can understand why you would think this.  But given the other 3 of us in the comparison hadn't outlaid our green to purchase either of the amps being compared ... we couldn't care less what they cost. 

 

1 minute ago, March Audio said:

 

The implication there is an amplifier that doesn't significantly distort the signal can't or won't be engaging - that's something I do take issue with.

 

 

But I never suggested that, Alan - you are putting words into my mouth! 

 

Andy

 

[March Audio]

39 minutes ago, andyr said:

 

 Provided you know what you need to measure! 

 

You didn't think much of my concept of 'air' - but I sure do know when I hear it.

 

So, if measurement informs you what's going on ... if you have the situation where:

• amplifier A has the singer (in front of a band) in the plane of the speakers, but
• amplifier B projects her a few feet forwards of the speaker line

... what do you measure, to account for this difference in soundstage presentation?

 

Because I've experienced this situation.  Amplifier A was a Bryston AB amp - at least 100w (into 8 ohms); amplifier B was Hugh Dean's "Glass Harmony" - a SE ss amp which could deliver only about 18w.  Amplifier B just didn't have the output to drive the Dali speakers to their limit but it had it all over the Bryston, in terms of soundstage.

 

 

I can understand why you would think this.  But given the other 3 of us in the comparison hadn't outlaid our green to purchase either of the amps being compared ... we couldn't care less what they cost. 

 

 

But I never suggested that, Alan - you are putting words into my mouth! 

 

Andy

 

 

Thats an issue of your communication and terminology.  Did you hear air with the 250 or did you hear the intermodulation distortion?

PRAT is a frankly comical term, it has no meaning.

 

Soundstage is primarily a product of your speaker dispersion characteristics coupled with the room acoustics.  Phase issues with amps can cause differences.

 

Its a fact that sighted listening will cause you to be biased.  Its nothing to do with the fact that you didnt personally spend the money.  Its a $64k amp, it must be good.   Its class D, they are rubbish.  Its subconcious even if you tell yourself otherwise.  Oh forgot to mention the group dynamics.  So you all came to the same conclusion........... No surprise there. 

 

In any case it's fairly clear in this instance why you heard differences, FwIW my opinion they are not good reasons but I wouldn't criticise your preferences. 

Edited September 4, 2019 by March Audio

[andyr]

15 minutes ago, March Audio said:

 

Thats an issue of your communication and terminology.  PRAT is a frankly comical term, it has no meaning.

 

You should stick to what I actually have written, Alan.

 

I didn't mention 'PRAT' - that was some other contributor to this thread.

(As I'm sure you know, 'PRAT' stands for 'Pace, Rythm and Timing' - a marketing phase used by Naim & Linn (the 'Flat Earthers'! ) to jusify the prices they were charging for their gear in the 80s.)

 

15 minutes ago, March Audio said:

 

Soundstage is primarily a product of your speaker dispersion characteristics coupled with the room acoustics.  Phase issues with amps can cause differences.

 

Sure, but given in the recording studio, the singer was undoubtedly in front of the band ... to me, the amp that presented her as such through the speakers is more accurate - irrespective of whether it has "phase issues".  (Bcoz you surely aren't suggesting that a Bryston amp would have "phase issues" - hence wasn't able to present the singer as she was recorded?  )

 

Regards,

Andy