[Venture Guy]

While SMPS is better because it can be regulated and it doesn't have hum noise, there are two problems with it that make it sound "thin" compared to LPS:

1) While regulation may hold the output voltage constant (it won't, read later), the caps are still too small to have low impedance in low frequencies. As in most amplifier topologies, for the AC current that goes through the speakers, the electrical circuit is closed through the PSU caps. They are in series to the speakers. They are sized adequately from the vantage point of PSU for smoothing out the HF switching noise but they are not large enough to be in series to the speakers, unless you're leaving it to the amp feedback to recover a bit too early bass roll-off.

2) They are always overrated for the actual power they can supply. For example 300W rated SMPS is more like only 100W continuous power. That is because the manufacturer assumes the crest factor of 6 dB (average music power is 6dB lower than peaks). The problem is that it will hold current and voltage for about 100ms and then the current/voltage limiter will kick in and start reducing pulse width and voltage and current will start drooping as fast as those small output caps are depleted. Not good for long notes in bass.

I have yet to hear a SMPS powered amp (including my beloved Benchmark AHB2) that sounds as full and rich in bass and have a slam as an amp with a beefy LPS. The guys from Esoteric do know why they chose LPS instead of SMPS.
Also, some PSU caps sound much better than other PSU caps and I have yet to see a good sounding caps used in SMPS.

So, my preference goes to a double-power EI transformer (no toroids and no crest factor applied) LPS with 40000-50000uF per rail per channel, preferably with multitude of small Cornell-Dubillier 381LX caps VS. resonant mode zero-crossing switching SMPS, any day of the week.

Besides, for Class D, which is the most dynamic load for PSU of any amplifier class, the best power supply is a battery...No current limit, no noise, no small caps in series to the speaker...

So, if there will be a R-r Class-D headphone amp, it will probably get supplied with gel-acid lead or Li-ion batteries.

Your comments about SMPS are completely misinformed. NCORE Amps ARE DESIGNED TO USE SMPS. THX maps ARE DESIGNED TO USE SMPS. I really hope you guys know A LOT more about ribbon tweeters than you do about amplifiers

 

[Zhanming057]

NCORE Amps ARE DESIGNED TO USE SMPS. THX maps ARE DESIGNED TO USE SMPS. I really hope you guys know A LOT more about ribbon tweeters than you do about amplifiers

The fact that a particular design is built around SMPS doesn't mean that SMPS is not inherently flawed. LPS is "better" - if you can make it work with size restrictions and the particular constraints of the design.

I had this conversation once with Masanori Masuda, the amp builder behind Mass Kobo. He sources extremely expensive SMPS modules, hand-built in Japan, that account for >50% of the price of his $5,000+ amps. Masuda wants his amps to be portable and take global voltage, and the easiest way to achieve that is to use the best SMPS he can find - but even then, he acknowledges that a good LPS will outperform the SMPS - and we're talking about $1,500 modules that are built around low output power for headphone use. The end result is exceedingly clean and robust performance at a lower output than most contemporary solid state designs. At that point, I suspect that the difference between LPS and SMPS is largely academic - but falling short of that, I do agree with Alex's points.

Alex, if you do go with the gel-acid battery route, I do hope that the battery is a separate module. If the amp can be driven off a 12v 1a LPS that would make portable/on-site use a possibility. Otherwise the battery will fail a lot sooner than the amp itself, and the modular design will help keep the amp alive long after the chemistry deteriorates.

 

[Aleksandar R.]

Your comments about SMPS are completely misinformed. NCORE Amps ARE DESIGNED TO USE SMPS. THX maps ARE DESIGNED TO USE SMPS. I really hope you guys know A LOT more about ribbon tweeters than you do about amplifiers

It is definitely true that I know a lot more about ribbons than amps, but you weren't really reading what I said.
If Hypex and THX figured out how to turn 5000uF into 50000uF, then I'll believe the marketing you just served me.
But you don't have to convince me. Tell it to the speakers that it's the same when they are charged and discharged through 10 times less capacitance than what's neefed for a proper bass slam.

 

[Venture Guy]

It is definitely true that I know a lot more about ribbons than amps, but you weren't really reading what I said.
If Hypex and THX figured out how to turn 5000uF into 50000uF, then I'll believe the marketing you just served me.
But you don't have to convince me. Tell it to the speakers that it's the same when they are charged and discharged through 10 times less capacitance than what's neefed for a proper bass slam.

That comment makes clear your level of understanding EE...

 

[Aleksandar R.]

The fact that a particular design is built around SMPS doesn't mean that SMPS is not inherently flawed. LPS is "better" - if you can make it work with size restrictions and the particular constraints of the design.

I had this conversation once with Masanori Masuda, the amp builder behind Mass Kobo. He sources extremely expensive SMPS modules, hand-built in Japan, that account for >50% of the price of his $5,000+ amps. Masuda wants his amps to be portable and take global voltage, and the easiest way to achieve that is to use the best SMPS he can find - but even then, he acknowledges that a good LPS will outperform the SMPS - and we're talking about $1,500 modules that are built around low output power for headphone use. The end result is exceedingly clean and robust performance at a lower output than most contemporary solid state designs. At that point, I suspect that the difference between LPS and SMPS is largely academic - but falling short of that, I do agree with Alex's points.

Alex, if you do go with the gel-acid battery route, I do hope that the battery is a separate module. If the amp can be driven off a 12v 1a LPS that would make portable/on-site use a possibility. Otherwise the battery will fail a lot sooner than the amp itself, and the modular design will help keep the amp alive long after the chemistry deteriorates.

I'll take your suggestions seriously into consideration.

 

[Aleksandar R.]

That comment makes clear you level of understanding EE...

OK, if you say so.

 

[Venture Guy]

OK, if you say so.

"Real knowledge is to know the extent of one's ignorance." Confucius

 

[WilliamWykeham]

What’s the point of this - it’s getting very trolly here - waste of everyone’s time

 

[Venture Guy]

What’s the point of this - it’s getting very trolly here - waste of everyone’s time

The point, which seems to escape you, is this: We as consumers are attempting to get the most out of a vendor's product. The vendor is making statements about certain potentially fruitful directions to get the product to perform well, which are patently false. A few of us are injecting some truth into the conversation.

Those truths are:
1. Properly implemented, Class-D amplifiers can produce TOTL sound quality.
2. Class-D amplifiers have ridiculously low output impedance, which MAY allow them to drive ribbon transducers directly.
3. Properly implemented, SMPS can outperform LMPS on the dimensions of noise, speed, high current capability, heat production, weight and cost.

 

[Zhanming057]

The point, which seems to escape you, is this: We as consumers are attempting to get the most out of a vendor's product. The vendor is making statements about certain potentially fruitful directions to get the product to perform well, which are patently false. A few of us are injecting some truth into the conversation.

Those truths are:
1. Properly implemented, Class-D amplifiers can produce TOTL sound quality.
2. Class-D amplifiers have ridiculously low output impedance, which MAY allow them to drive ribbon transducers directly.
3. Properly implemented, SMPS can outperform LMPS on the dimensions of noise, speed, high current capability, heat production, weight and cost.

I don't want this discussion to continue but Alex has conceded that he needs more experience regarding point 1, and he is right about point 2 and 3 and not you, as far as my own understanding and expertise suggests.

1. Yes, but it takes heroic effort to implement a strong class D design that sounds good. I don't think I've heard a pure class D design south of $3,000 that holds up against class A amps in the same price range. The good and cheap ones might be out there but I haven't tried those yet.

2. Maybe, but low output impedance is meaningless in this context unless the amp can drive a load down to far less than 1 ohm. AFAIK Bakoon has a direct current system that goes down to 1 ohm and there are a couple development efforts toward pushing that even lower, but it's an unresolved issue. A class D design has as much of a chance of driving the ribbons as a solid state class A design, the big constraint is the extremely low resistance of the ribbons.

3. SMPS works if you have low power requirements and high parts quality and is wiling to take a small hit in dynamics on top of all that. It's okay in principle but it takes a lot of effort to do correctly. Otherwise it's LPS all the way, precisely as Alex said.

All of this is highly theoretical but yes, if there is an Rr amp I'd like to see a standardized LPS or an optional LPS module Nagra/Sotm style.

Going back to the SR1A's, has anyone else received their production unit yet?

 

[Venture Guy]

I don't want this discussion to continue but Alex has conceded that he needs more experience regarding point 1, and he is right about point 2 and 3 and not you, as far as my own understanding and expertise suggests.

1. Yes, but it takes heroic effort to implement a strong class D design that sounds good. I don't think I've heard a pure class D design south of $3,000 that holds up against class A amps in the same price range. The good and cheap ones might be out there but I haven't tried those yet.

2. Maybe, but low output impedance is meaningless in this context unless the amp can drive a load down to far less than 1 ohm. AFAIK Bakoon has a direct current system that goes down to 1 ohm and there are a couple development efforts toward pushing that even lower, but it's an unresolved issue. A class D design has as much of a chance of driving the ribbons as a solid state class A design, the big constraint is the extremely low resistance of the ribbons.

3. SMPS works if you have low power requirements and high parts quality and is wiling to take a small hit in dynamics on top of all that. It's okay in principle but it takes a lot of effort to do correctly. Otherwise it's LPS all the way, precisely as Alex said.

All of this is highly theoretical but yes, if there is an Rr amp I'd like to see a standardized LPS or an optional LPS module Nagra/Sotm style.

Going back to the SR1A's, has anyone else received their production unit yet?

Just to finish up. I have a degree in the field from Leland Stanford Junior University. Over my 40 year career, I have consulted on these very topics for Apple, Hewlett Packard, Sony and Mitsubishi, among others. You are wrong about 1, 2 and 3.

 

[Bill13]

Received my new Raal Requisite SR1a headphones yesterday, Friday. Still listening to get a handle on these ribbon headphones - expect to post some initial impressions later - However, with my not -so -'golden ears', feel like would be going out on a limb to give initial impressions with sufficient confidence. Had them for only a day.

SR1A POWER REQUIREMENTS:
Driving them with Hypex Ncore 400 wpc 2-channel amp. I tend to listen at low-to-moderate volumes. I roughly measured the amplifier's power output to the 6 ohm load presented by the SR1a interface box with the headphones connected. I played a piano recording and set the volume level to where I felt that listening started to become uncomfortable. Remarkably, average loudness only required well under 1/4 watt per channel, and also, surprisingly, piano fortissimos demanded under 1 watt - the peaks didn't exceed two watts per channel -as far as I could tell.
Yes, my measurement was crude, because one might expect the highest loudness peaks to take far more power than only 2 watts -- just reporting what I saw.
Perhaps headphone power measurement was roughly verified by a 120 VAC power wattmeter. Wattmeter indicated that 2-ch amp's idle power consumption was 22 watts (with no input signal) -- but amp's AC power input evidently never exceed 23 watts during this piano music test -- according to the AC-power watt meter, anyway.

APPLYING EQ:
So far, I've found that the reported SR1a's excessive resolution for poor quality recordings can be remedied by adding EQ in the playback chain (see graph below).
For poor recordings I applied EQ using Redscape in the playback mix.

Here's a picture, .jpg, of a preliminary, very subject to change, EQ graph giving what I felt allowed euphonic "polite" = subjectively 'forgiving' playback for poor recordings, IMO, YMMV.

At the risk of being flamed, my preliminary impression is, stated hyperbolically, that this EQ in a way, kinda turns the SR1a into an Ether 2 on steroids. --- Why 'steroids'? -- because IMO, so far, the SR1a, even severely toned down by applying EQ, still offers exceptional resolution while sounding euphonic -again, of course YMMV.
Realize that I'm going out on a limb here - but hopefully, will stimulate some helpful conversation(s).

Said enough in this post for now.

 

[Thenewguy007]

Your comments about SMPS are completely misinformed. NCORE Amps ARE DESIGNED TO USE SMPS. THX maps ARE DESIGNED TO USE SMPS. I really hope you guys know A LOT more about ribbon tweeters than you do about amplifiers

I read that SMPS have come a long way & the expensive Chord Dave, Mola Mola Tambaqui & I think even the Rockna line of DACs have SMPS & they all sound good. Though the power of a DAC is not the same as one needed for an amp. There was also criticisms of the DACS (at least Chord ones) to sound thin, a sound signature of a SMPS.

 

[Thenewguy007]

Just to finish up. I have a degree in the field from Leland Stanford Junior University. Over my 40 year career, I have consulted on these very topics for Apple, Hewlett Packard, Sony and Mitsubishi, among others. You are wrong about 1, 2 and 3.

That really means nothing.
People with even more impressive credentials have been proven wrong & I have never seen a Class D amp sound better to a equivalent Class A amp in terms of sound quality.

If those $500 NCore amps on ebay were so hot, there would be thousands of people praising them & dumping their Audio Note, Dartzeel, Pass Labs etc... but that hasn't happened.

 

[Zhanming057]

Finalizing my SR1A review...here's another teaser shot