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Darlington Labs MM-5 Review (Phono Stage)

krichard2496

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I took a quick look at the 2 pdf links posted. I am puzzled by the choice of topic. Please explain how this relates to a phono preamplifier.
Occasionally LPs are now cut from digital files (albeit usually 24 bit/192K direct from the original source master tape, avoiding one to three generations of analog tape from back in the day)?
 

Francis Vaughan

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We're not in the business of building electronics for the telecommunications industry.
I took a quick look at the 2 pdf links posted. I am puzzled by the choice of topic. Please explain how this relates to a phono preamplifier.

The impression this is about digital communication only can be easily had. It isn't. The mathematics and conclusions are perhaps more applicable in those areas, but there is nothing about the fundamentals that requires a digital coding. This is covered in the papers.

Again, this stuff is fundamental, it is taught in any university engineering course on the planet, although probably not in the depth it deserves.

The important point is that claims that the ear can hear 140 - 170dB below signal are fundamentally unfounded. We can hear below noise, but the limits to what can be resolved are bounded by the nature of the universe we live in.

All of audio is bound by Shannon's fundamental findings. Digital audio clearly, but the duality of information representation means that analog systems are identically bound.
 

Postkrunk

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When I studied op amp circuitry we where shown that op amp negative feedback in audio circuitry is not a bad thing with op amp circuitry.
Negative feedback is not a bad thing at all. But there are a lot of possible opamp-based topologies for a phono preamp, and a lot of manufacturers just go for one dual opamp with a frequency-dependent global NFB loop. If feedback factor could solve all the problems, there would be no difference between iFi Zen and Behringer PP400.
 

krichard2496

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The impression this is about digital communication only can be easily had. It isn't. The mathematics and conclusions are perhaps more applicable in those areas, but there is nothing about the fundamentals that requires a digital coding. This is covered in the papers.

Again, this stuff is fundamental, it is taught in any university engineering course on the planet, although probably not in the depth it deserves.

The important point is that claims that the ear can hear 140 - 170dB below signal are fundamentally unfounded. We can hear below noise, but the limits to what can be resolved are bounded by the nature of the universe we live in.

All of audio is bound by Shannon's fundamental findings. Digital audio clearly, but the duality of information representation means that analog systems are identically bound.
We look foward to your upcoming company's products introduction to the marketplace.
 

Francis Vaughan

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We look foward to your upcoming company's products introduction to the marketplace.

I look forward to your paper refuting Shannon's work.
Seriously, you make a good product. Don't demean your capabilities with idiotic retorts.

You are basically making claims that go against well understood science. And claims with no backing other than "we make a good product".
The jump from "nice product" to "proof of new physics and mathematics" is a very big one. You can make a good product without needing to make outrageous claims about the human hearing process.
 

Bob from Florida

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The impression this is about digital communication only can be easily had. It isn't. The mathematics and conclusions are perhaps more applicable in those areas, but there is nothing about the fundamentals that requires a digital coding. This is covered in the papers.

Again, this stuff is fundamental, it is taught in any university engineering course on the planet, although probably not in the depth it deserves.

The important point is that claims that the ear can hear 140 - 170dB below signal are fundamentally unfounded. We can hear below noise, but the limits to what can be resolved are bounded by the nature of the universe we live in.

All of audio is bound by Shannon's fundamental findings. Digital audio clearly, but the duality of information representation means that analog systems are identically bound.

I used to work with this guy that knew engineering and nuclear physics quite well. When he was in the Navy he served on the USS Los Angeles - first 688 attack sub. His expertise and understanding of electronics was amazing. Only he could not explain it in terms the rest of us could easily understand. Shannon's papers, you linked, reminded me of my old co-worker. Dry mathematic proofs about morse code and other digital communications would not be my first choice for explaining why we can't hear below a certain level. Posting a link to hearing research showing the average human can hear -xxx db would seem more informative.

Please note this is not meant to offend. Just making the case - my opinion - that "a lay person explanation" would be more suitable.
 

Francis Vaughan

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There are really two parts to this. What the ear can hear and what the physical universe we live in allows. Hearing studies abound, and they provide some remarkable indications about how limited our ear actually is.
My point is that no matter what you are using, be it ears or the most sensitive equipment humanity has devised, there are fundamental limits. We have some astounding technology in some systems. LIGO perhaps being the most extreme. It can haul a signal out from seemingly impossible depths of noise. But our ears are not LIGO and music is not the sound of black holes colliding.
I’m happy to explain in layman’s terms. But we started the conversation at an engineering design level, one where I would have assumed layman’s explanations were not needed.
The underlying mathematics and duality of the nature of information is quite beautiful and sits at the base of the very core of the universe.
 

psemeraro

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I currently have an MM6 on trial. I've also learned over time that ASR can be a difficult place to share impressions without an APA printout and peer-reviewed double blind test results to backup a claim of what I'm hearing.

Compared to my battery powered, DC output coupled Mani which is silent in use, the MM6 is remarkably open, and clear sounding vs the Mani. The Mani even at lowest gain setting has a grainy, slightly "hashy" sound compared to the MM6, even though they both measure with noise that is lower than the source. The MM6 has lots of clean detail but does not sound brighter than the Mani, just more resolved. Surface noise has a very different character between the two preamps.

Maybe the technical folks here can better explain what I'm hearing? Its as if there's subtle noise that moves around and through the audio in the Mani that I dont hear in the MM6.

Pat
 

Bob from Florida

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I currently have an MM6 on trial. I've also learned over time that ASR can be a difficult place to share impressions without an APA printout and peer-reviewed double blind test results to backup a claim of what I'm hearing.

Compared to my battery powered, DC output coupled Mani which is silent in use, the MM6 is remarkably open, and clear sounding vs the Mani. The Mani even at lowest gain setting has a grainy, slightly "hashy" sound compared to the MM6, even though they both measure with noise that is lower than the source. The MM6 has lots of clean detail but does not sound brighter than the Mani, just more resolved. Surface noise has a very different character between the two preamps.

Maybe the technical folks here can better explain what I'm hearing? Its as if there's subtle noise that moves around and through the audio in the Mani that I dont hear in the MM6.

Pat
The Mani has less headroom - made worse if you set gain stage one to high. Music content above 1 khz may be clipping in the first stage before RIAA correction. My guess is you are hearing distortion.
What did you do to your Mani to allow for a DC supply? Mine had a 16 VAC walwart.
 

psemeraro

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The Mani has less headroom - made worse if you set gain stage one to high. Music content above 1 khz may be clipping in the first stage before RIAA correction. My guess is you are hearing distortion.
What did you do to your Mani to allow for a DC supply? Mine had a 16 VAC walwart.

I did nothing to allow for DC supply. Correct polarity DC passes thru the AC rectifier diodes with about a 1.5v drop. The nominal 16v AC wall wart becomes about 24v DC in the Mani after rectification. The first internal voltage regulator regulates the rectified 24vish v DC to 12v, so anything above 12v allows for the regulator to do its job correctly. I use a Ryobi 18v tool battery which works great. Powered from my lab supply, anything above 7 volts will allow the Mani to work, anything above 12v (post rectifier diodes after their forward voltage drop) allows the power supply to dual regulate correctly to the 5v +/- internal it actually operates on.

A $25 amazon adapter for the Ryobi battery allows using power tool batteries and chargers which many people already have. This is not "audiophile approved" parts solution with space dust coatings, etc... but does allow using high current high capacity batteries and charging infrastructure for the cost of a pizza. The 50 ma draw of the Mani is no challenge for batteries that power leaf blowers, drills etc and can go for months before popping back into the charger for a top up.

Pat
 
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psemeraro

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The Mani has less headroom - made worse if you set gain stage one to high. .
As mentioned earlier, I only run my mani at lowest gain setting. Battery powered, in isolation, it sounds quite good - powerful, punchy, wide separation, etc., but its character seems to change for the worse at higher gain settings.

Pat
 

krichard2496

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I did nothing to allow for DC supply. Correct polarity DC passes thru the AC rectifier diodes with about a 1.5v drop. The nominal 16v AC wall wart becomes about 24v DC in the Mani after rectification. The first internal voltage regulator regulates the rectified 24vish v DC to 12v, so anything above 12v allows for the regulator to do its job correctly. I use a Ryobi 18v tool battery which works great. Powered from my lab supply, anything above 7 volts will allow the Mani to work, anything above 12v (post rectifier diodes after their forward voltage drop) allows the power supply to dual regulate correctly to the 5v internal it actually operates on.

A $25 amazon adapter for the Ryobi battery allows using power tool batteries and chargers which most people already have. This is not "audiophile approved" parts solution with space dust coatings, etc... but does allow using high current high capacity batteries and charging infrastructure for the cost of a pizza. The 50 ma draw of the Mani is no challenge for batteries that power leaf blowers, drills etc and can go for months before popping back into the charger for a top up.

Pat
We were very surprised to see a rail splitter design in the Mani. Had not thought of the external DC supply like this; nice work.
We wonder whether a complete redesign of the Mani would be possible to raise the rail voltages significantly to improve the headroom.
Version 1.0 used a front end op-amp with a max supply voltage of something like 12V (probably for sonic reasons and/or noise floor), and the following op amps were able to tolerate up to ~24V. Hence the low overall supply voltage.
Then V. 1.1 and 1.2 made some adjustments to improve RFI rejection and/or deal with an end-of-life situation of one of the op amps.
In V. 1.2, the op amps appear to have a max supply voltage of 24V so a +/-11V design would certainly be possible and would likely double headroom. We suspect this is not being done because it could cause confusion and/or call into question the original design.
 

Bob from Florida

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I did nothing to allow for DC supply. Correct polarity DC passes thru the AC rectifier diodes with about a 1.5v drop. The nominal 16v AC wall wart becomes about 24v DC in the Mani after rectification. The first internal voltage regulator regulates the rectified 24vish v DC to 12v, so anything above 12v allows for the regulator to do its job correctly. I use a Ryobi 18v tool battery which works great. Powered from my lab supply, anything above 7 volts will allow the Mani to work, anything above 12v (post rectifier diodes after their forward voltage drop) allows the power supply to dual regulate correctly to the 5v +/- internal it actually operates on.

A $25 amazon adapter for the Ryobi battery allows using power tool batteries and chargers which many people already have. This is not "audiophile approved" parts solution with space dust coatings, etc... but does allow using high current high capacity batteries and charging infrastructure for the cost of a pizza. The 50 ma draw of the Mani is no challenge for batteries that power leaf blowers, drills etc and can go for months before popping back into the charger for a top up.

Pat

I understand - possibly a little less hum with the battery. If I recall correctly it uses an inverter to get the -5 volts for the negative rail.
 

DonH56

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I'm reading a bit of a disconnect... It seems @krichard2496 's statement about -140 dB to -170 dB was not to say we can hear that far down; in fact, he said that is buried in the noise. The statement was about R and C noise at that level, which implies perhaps passive component thermal, current, and kTC noise is that far down? Not that humans can pull any sort of signal from -140 dB or below? I'm confused (i.e. normal).
 
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krichard2496

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I'm reading a bit of a disconnect... It seems @krichard2496 's statement about -140 dB t0 -170 dB was not to say we can hear that far down; in fact, he said that is buried in the noise. The statement was about R and C noise at that level, which implies perhaps passive component thermal, current, and kTC noise is that far down? Not that humans can pull any sort of signal from -140 dB or below? I'm confused (i.e. normal).
Yes, we are not making ANY scientific claims regarding human hearing capacity. This is not our specialty. The ony claims we make are related to our units conventional specifications, which as Amir noted, are reasonably consistent (i.e., accurate and repeatable).

The Cyril Bateman articles do analyze passive R and C and show differences at those levels.
Our listening tests confirm the preference for a ranking similar to what his results showed - i.e, in general, the resistor and capacitor technology that he showed as having "better" performance, isolated down at those levels, was directionally similar to what we perceived in our testing.

Therefore, our only sincere hypothesis is that the human ear must be able to perceive distortion well down into the noise floor (this is generally known but probably conventionally accepted as 10 to 20+dB into the noise floor. We hypothesize that it may be greater than this.

D.E.L. Shorter's 1949 article is available at: https://www.bbc.co.uk/rd/publications/rdreport_1949_30

Attached are our original calculations based on Shorter's formula. To our knowledge we have not seen them posted elsewhere with an actual derivation by harmonic. They have been peer reviewed by an ASR member and the calcuations shown have small insignificant rounding errors.

Essentially they propose a weighting formula that increases the upper harmonics (above the 2nd) in total contribution to a new "weighted THD" metric.

The top of page 611 of RHD4 shows an analysis of 5 BBC broadcast transmission plants, some AM, some FM, whereby the ear's assessment of the "impared-ness" of the plant was ranked in correct order with the "measured result" when the "measured result" was via this new weighting. It is the "more drastic weighting" as mentioned by the editor of RDH4 on page 610.

We don't refute Shannon, et. al; we just question the applicability to this discussion.

Keith Richardson
Director of Engineering
Darlington Labs LLC
www.darlingtonlabs.com
 

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DonH56

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Yes, we are not making ANY scientific claims regarding human hearing capacity. This is not our specialty. The ony claims we make are related to our units conventional specifications, which as Amir noted, are reasonably consistent (i.e., accurate and repeatable).

The Cyril Bateman articles do analyze passive R and C and show differences at those levels.
Our listening tests confirm the preference for a ranking similar to what his results showed - i.e, in general, the resistor and capacitor technology that he showed as having "better" performance, isolated down at those levels, was directionally similar to what we perceived in our testing.

Therefore, our only sincere hypothesis is that the human ear must be able to perceive distortion well down into the noise floor (this is generally known but probably conventionally accepted as 10 to 20+dB into the noise floor. We hypothesize that it may be greater than this.

D.E.L. Shorter's 1949 article is available at: https://www.bbc.co.uk/rd/publications/rdreport_1949_30

Attached are our original calculations based on Shorter's formula. To our knowledge we have not seen them posted elsewhere with an actual derivation by harmonic. They have been peer reviewed by an ASR member and the calcuations shown have small insignificant rounding errors.

Essentially they propose a weighting formula that increases the upper harmonics (above the 2nd) in total contribution to a new "weighted THD" metric.

The top of page 611 of RHD4 shows an analysis of 5 BBC broadcast transmission plants, some AM, some FM, whereby the ear's assessment of the "impared-ness" of the plant was ranked in correct order with the "measured result" when the "measured result" was via this new weighting. It is the "more drastic weighting" as mentioned by the editor of RDH4 on page 610.

We don't refute Shannon, et. al; we just question the applicability to this discussion.

Keith Richardson
Director of Engineering
Darlington Labs LLC
www.darlingtonlabs.com

Thank you, downloading the paper.

I had a vague memory of weighting harmonics by n^4 and have a spreadsheet that does it but did not have the original paper for the basis. It was a reference in another paper so I appreciate the link to the original.

The argument of higher relative amplitudes of higher harmonics being a drawback of feedback has been made over the years (decades) and not just in audio, but the usual response is higher feedback lowers the overall distortion more than enough to compensate and additional added or natural filtering rolls off the higher harmonics. The latter argument is valid for a lot of narrowband systems but not as much for wideband systems like audio components.
 

antennaguru

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All of audio is bound by Shannon's fundamental findings.

Claude Shannon's work in 1948 was certainly impressive, but we seem to be forgetting all about the importance of the contributions from those that came before him such as James Maxwell's work in 1865, Ludwig Bolzmann's work in 1896, Lee De Forest's work in 1906, and Edwin Armstrong's work in 1919 and 1933 - to name a few.
 

Francis Vaughan

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Claude Shannon's work in 1948 was certainly impressive, but we seem to be forgetting all about the importance of the contributions from those that came before him such as James Maxwell's work in 1865, Ludwig Bolzmann's work in 1896, Lee De Forest's work in 1906, and Edwin Armstrong's work in 1919 and 1933 - to name a few.
Well they were enabling technology. Even without any electronic reproduction Shannon holds. An Edison Cylinder is still subject. Even just listening live is. Our entire universe is.

Maxwell was a prince amongst physicists; any list of the greatest must include him.
 

CausticStorm

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I did nothing to allow for DC supply. Correct polarity DC passes thru the AC rectifier diodes with about a 1.5v drop. The nominal 16v AC wall wart becomes about 24v DC in the Mani after rectification. The first internal voltage regulator regulates the rectified 24vish v DC to 12v, so anything above 12v allows for the regulator to do its job correctly. I use a Ryobi 18v tool battery which works great. Powered from my lab supply, anything above 7 volts will allow the Mani to work, anything above 12v (post rectifier diodes after their forward voltage drop) allows the power supply to dual regulate correctly to the 5v +/- internal it actually operates on.

A $25 amazon adapter for the Ryobi battery allows using power tool batteries and chargers which many people already have. This is not "audiophile approved" parts solution with space dust coatings, etc... but does allow using high current high capacity batteries and charging infrastructure for the cost of a pizza. The 50 ma draw of the Mani is no challenge for batteries that power leaf blowers, drills etc and can go for months before popping back into the charger for a top up.

Pat

Pretty much what I was talking about earlier, but you went into more detail :) I ran my diy phono stage and headphone amp the same way, simple and effective .

Cheers!
 

Lttlwing16

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I plan on beginning work on a comparative analysis of the Darlington Labs MM-6 and the ART DJ PREII, as I own both currently. I will create a new thread and post the findings there.

Here is my plan:

Waveform analysis

-- System Noise
- measure both with just ground from TT
- measure both with ground compensation for PREII for known ground loop

-- Gain --
MM-6
PREII at -0-
PREII adjusted to just below clip

-- Record Noise--
IGD -- Leon Bridges Gold Diggers
Click and Pop handling

Subjective listening samples

Any other thoughts or additions?
 
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