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Darlington Labs MM-5 Review (Phono Stage)

krichard2496

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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?
We suggest spectral measurements of the distortion from a 1 kHz tone, for both units, at -10dB before reference level, -5dB re: Ref Level, 0dB (Ref Level), +3dB, +6dB, +10dB, +15dB, +20dB, and +25dB above reference level.
 

Lttlwing16

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We suggest spectral measurements of the distortion from a 1 kHz tone, for both units, at -10dB before reference level, -5dB re: Ref Level, 0dB (Ref Level), +3dB, +6dB, +10dB, +15dB, +20dB, and +25dB above reference level.
Keith, thanks for the recommendations, unfortunately, this would be outside of the tools/equipment I have at my disposal, and not sure I'd be the best at those particular measurements.

I originally set out to just bring forth an A/B audio recording of both to allow for some subjective review since @amirm offers us great objective measurments, but unfortunately for phono stages, he does not offer a subjective. Then I realized I could import these audio samples into my Pro Tools rig and run them through a couple tools to glean some objective data from the A/B samples as well. Not grossly scientific, but there for what it is for folks to take what they want from it.

Should be noted -- I'm personally biased. The MM-6 is an amazing phono stage. Hopefully I can bring a fair analysis that folks can see for themselves.

EDIT 11/3/21: I was informed by Keith the MM-6 (and MP-7) are now shipping with an improved power supply which improves the sound quality. In an email he stated "The sonic differences are a deepening and tightening of the bass response, and an overall improvement to clarity across the spectrum. As if you took Windex to a slightly dusty window."

Since my MM-6 is using the old power supply, I don't feel it would be fair to judge it's performance since it is now one version behind. In addition, I opted to trade in my MM-6, for the upgraded and next model higher, MP-7, which Darlington Labs is going to custom build dual output into the unit for me.

That said, I will no longer be able to offer a comparison of the MM-6 to the ART DJ PREII.
 
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krichard2496

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Keith, thanks for the recommendations, unfortunately, this would be outside of the tools/equipment I have at my disposal, and not sure I'd be the best at those particular measurements.

I originally set out to just bring forth an A/B audio recording of both to allow for some subjective review since @amirm offers us great objective measurments, but unfortunately for phono stages, he does not offer a subjective. Then I realized I could import these audio samples into my Pro Tools rig and run them through a couple tools to glean some objective data from the A/B samples as well. Not grossly scientific, but there for what it is for folks to take what they want from it.

Should be noted -- I'm personally biased. The MM-6 is an amazing phono stage. Hopefully I can bring a fair analysis that folks can see for themselves.
You can do this with an AC voltmeter in parallel with the output of both units. Choose a smaller number if needed. -10dB, 0dB, +10dB, +20dB.
Calibrate your Analog to Digital Converter to about 3dB before it's internal clipping. You might need to add an attenuator after the Device Under Test depending on the gain structure of your A/D. Pro Tools should offer a spectrum analyzer. It won't be Audio Precision style but will be useful.
 

krichard2496

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This is a review and detailed measurements of the Darlington Labs MM-5 Moving Magnet phono pre-amplifier. [snip] Company makes up for that partially with good implementation of RIAA equalization: [snip]

>>As noted, there is no high pass filter here so if your woofers are dancing around without making any sound, you know you should have gotten a phono stage with one.

PRODUCT UPDATE ANNOUNCEMENT: AVAILABILTY OF A SHARP-CUTOFF SUBSONIC FILTER

We have developed a fixed custom-slope low-frequency filter that is sonically transparent enough to be left in the circuit at all times, but is intended only for users who need it. We foresee three main scenarios where this could be of potential benefit: 1) Subwoofers with a gain structure optimized for digital sources, 2) Limited turntable acoustic isolation, 3) Moderately-to-substantially-underdamped tonearm/cartridge resonance.

We now offer this fixed Subsonic Filter per client request at no cost. It is available for the MM-5, MM-6, and MP-7. As we expect relatively limited interest, buyers can place a regular order via our website and then email us with the order number. https://www.darlingtonlabs.com/shop

This filter is nominally a 12dB/octave low-cut (‘high-pass’) using a transfer function of our own design. It is optimized to provide good transient response, and minimum excess phase shift, while being musically unobtrusive.

Specifications are as follows:

70Hz +0.05dB; 50Hz 0dB; 30Hz -0.5dB; 25Hz -1dB; 20Hz -2dB; 17Hz -3dB; 12Hz -6dB; 10Hz -8dB; 5Hz -19dB.

The existing gain elements are used as buffering nodes to eliminate filter section interaction. This means NO additional active gain elements in the circuitry for the best sound quality. The curve is also unaffected by external loading, because the output stage does not contain a section of the filter.

It can be deployed in our MM-5, MM-6 and MP-7 at user request and at no additional cost when ordered in a new unit. Current users may contact us for a retrofit quote.

Note that our current standard RIAA equalization is now even flatter in the lowest few octaves, as we have eliminated the slight low-frequency contour seen in the July 2021 measured graph. The overall frequency response is now quoted as 20Hz to 20kHz, +0.25/-0.25dB (MM-5), +/-0.23dB (MM-6) and +/-0.2dB (MP-7). rather than the previous 50Hz to 20kHz.
 
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Lttlwing16

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PRODUCT UPDATE ANNOUNCEMENT: AVAILABILTY OF A SHARP-CUTOFF SUBSONIC FILTER

We have developed a fixed custom-slope low-frequency filter that is sonically transparent enough to be left in the circuit at all times, but is intended only for users who need it. We foresee three main scenarios where this could be of potential benefit: 1) Subwoofers with a gain structure optimized for digital sources, 2) Limited turntable acoustic isolation, 3) Moderately-to-substantially-underdamped tonearm/cartridge resonance.

We now offer this fixed Subsonic Filter per client request at no cost. It is available for the MM-5, MM-6, and MP-7. As we expect relatively limited interest, buyers can place a regular order via our website and then email us with the order number. https://www.darlingtonlabs.com/shop

This filter is nominally a 12dB/octave low-cut (‘high-pass’) using a transfer function of our own design. It is optimized to provide good transient response, and minimum excess phase shift, while being musically unobtrusive.

Specifications are as follows:

70Hz +0.05dB; 50Hz 0dB; 30Hz -0.5dB; 25Hz -1dB; 20Hz -2dB; 17Hz -3dB; 12Hz -6dB; 10Hz -8dB; 5Hz -19dB.

The existing gain elements are used as buffering nodes to eliminate filter section interaction. This means NO additional active gain elements in the circuitry for the best sound quality. The curve is also unaffected by external loading, because the output stage does not contain a section of the filter.

It can be deployed in our MM-5, MM-6 and MP-7 at user request and at no additional cost when ordered in a new unit. Current users may contact us for a retrofit quote.

Note that our current standard RIAA equalization is now even flatter in the lowest few octaves, as we have eliminated the slight low-frequency contour seen in the July 2021 measured graph. The overall frequency response is now quoted as 20Hz to 20kHz, +0.25/-0.25dB (MM-5), +/-0.23dB (MM-6) and +/-0.2dB (MP-7). rather than the previous 50Hz to 20kHz.
Keith, what are the limitations to implementing a switchable roll off filter?

When I listen to my TT through my speakers, I'd love the roll off as I have 2) Limited turntable acoustic isolation, and I get dropouts from resonance (at least is my hypothesis). However, when I am listening on my AEON RT headhpones, which have great low frequency response, I'd like to have that energy there.
 

krichard2496

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Keith, what are the limitations to implementing a switchable roll off filter?

When I listen to my TT through my speakers, I'd love the roll off as I have 2) Limited turntable acoustic isolation, and I get dropouts from resonance (at least is my hypothesis). However, when I am listening on my AEON RT headhpones, which have great low frequency response, I'd like to have that energy there.

Hi, thanks for the inquiry. We can make it switchable via a rear-panel switch for an additional charge.

The complication is that - as part of the filter design - we are also adjusting the 3180 μs (50 Hz) and 318 μs (500 Hz) time constants of the RIAA EQ slightly. We do this for sonic reasons, to make the shape of the curve very slightly resonant/Ellptic-like going into the knee, Bessel-like through the transition region, and slightly Elliptic below. In our listening tests, this optimized the phase and transient response, minimizing the audibility of the filter.

So, with this current design, if you defeat both sections, you end up with slightly elevated LF response (+1dB at 20Hz, shelving downward to flat at about 100Hz). This might actually be perfect for your headphone listening, however.

As part of our work on subsonic filters, we also now offer two optional -- and slightly elevated -- LF responses which can be used to offset the LF rolloff that might be present in a vacuum-tube amplifier, for example... We now have a section in our FAQ discussing this entitled "Can the low frequency response be customized for my system?" Option A is +0.5dB at 20Hz, particularly useful for a push-pull amplifier. Option B is +1.0dB at 20Hz, useful for a Single-Ended Tube amplifier. Both of these are well-tailored low-frequency shelves with minimal impact from 50 to 100Hz. They allow system-level frequency response correction with no additional active electronics in the signal path, which can improve system low-frequency phase and transient response. Those options are also not currently switchable, but if there is enough interest, we could potentially have DIP headers inside on the MM-5 and MM-6 units (not the 7 due to space).

We've had about ten times (10X) the interest in inclusion of a Mono switch (which we added this past spring) as compared to Subsonic Filtering. We came up with an unusual and effective design. Note that some competitive units (like the Cambridge Solo and Duo) appear to have undefeatable-by-the-user subsonic filtering built-in to all models (as tested by Amir) rather than a user-specified option - which we reject from a purist standpoint as being unnecessary. But, we will attempt to respond to market demand and appreciate any input that forum members can provide.

Right now, if someone buys a new preamp from us, and after evaluation determine they need a subsonic filter, we will install our new fixed-design filter at no cost. The buyer will then have another 30-day window for our money-back guarantee (although the return rate--for any reason--is already extremely low).
 
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Lttlwing16

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Hi, thanks for the inquiry. We can make it switchable via a rear-panel switch for an additional charge.

The complication is that - as part of the filter design - we are also adjusting the 3180 μs (50 Hz) and 318 μs (500 Hz) time constants of the RIAA EQ slightly. We do this for sonic reasons, to make the shape of the curve very slightly resonant/Ellptic-like going into the knee, Bessel-like through the transition region, and slightly Elliptic below. In our listening tests, this optimized the phase and transient response, minimizing the audibility of the filter.

So, with this current design, if you defeat both sections, you end up with slightly elevated LF response (+1dB at 20Hz, shelving downward to flat at about 100Hz). This might actually be perfect for your headphone listening, however.

As part of our work on subsonic filters, we also now offer two optional -- and slightly elevated -- LF responses which can be used to offset the LF rolloff that might be present in a vacuum-tube amplifier, for example... We now have a section in our FAQ discussing this entitled "Can the low frequency response be customized for my system?" Option A is +0.5dB at 20Hz, particularly useful for a push-pull amplifier. Option B is +1.0dB at 20Hz, useful for a Single-Ended Tube amplifier. Both of these are well-tailored low-frequency shelves with minimal impact from 50 to 100Hz. They allow system-level frequency response correction with no additional active electronics in the signal path, which can improve system low-frequency phase and transient response. Those options are also not currently switchable, but if there is enough interest, we could potentially have DIP headers inside on the MM-5 and MM-6 units (not the 7 due to space).

We've had about ten times (10X) the interest in inclusion of a Mono switch (which we added this past spring) as compared to Subsonic Filtering. We came up with an unusual and effective design. Note that some competitive units (like the Cambridge Solo and Duo) appear to have undefeatable-by-the-user subsonic filtering built-in to all models (as tested by Amir) rather than a user-specified option - which we reject from a purist standpoint as being unnecessary. But, we will attempt to respond to market demand and appreciate any input that forum members can provide.

Right now, if someone buys a new preamp from us, and after evaluation determine they need a subsonic filter, we will install our new fixed-design filter at no cost. The buyer will then have another 30-day window for our money-back guarantee (although the return rate--for any reason--is already extremely low).
I'd assume the switchable roll off filter would not be able to be retrofitted to an MM-6 from early July 2021 (received July 30th)?
 

antennaguru

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I'd assume the switchable roll off filter would not be able to be retrofitted to an MM-6 from early July 2021 (received July 30th)?

For $30 you can buy a pair of these Harrison Labs High Pass Filters, shipped, and plug them in-line when you need them, and unplug them when you don't:
https://www.ebay.com/itm/372982266630?epid=1551008026&hash=item56d779bb06:g:~~4AAOSw2XJbjx1e

Those that need them can use them, and those that don't - well, they don't need to bother. It really depends mostly upon your turntable isolation (plus its inherent rumble) and if you have an arm/cartridge resonance mismatch. I have only encountered one vintage turntable where the use of these in-line filters was preferred, and it's a very powerful idler drive turntable removed from a radio station with giga-hours on it. The rumble vanishes with the filters and there is no other adverse sonic effect elsewhere in the audio spectrum.

As far as a mono switch goes, you can always use a pair of back to back Y-Cable adapters in your tonearm leads when you need Mono versus Stereo, and just unplug the back to back Y-Cable adapters to return to Stereo.
 

krichard2496

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I'd assume the switchable roll off filter would not be able to be retrofitted to an MM-6 from early July 2021 (received July 30th)?
We can retrofit your unit, and indeed, any existing unit in the field.
Pricing is up on our FAQ.

We can also make the slight LF boost switchable as well, so two switches could be used to have virtually flat response (as normal) plus the optimized Subsonic Filter, as well as a LF boost position with no subsonic filtration. More info in the FAQ. https://www.darlingtonlabs.com/faq

It occurs to us that the FAQ has become long enough that we need to add sublinks at the top. That's on our to-do list.
 

krichard2496

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For $30 you can buy a pair of these Harrison Labs High Pass Filters, shipped, and plug them in-line when you need them, and unplug them when you don't:
https://www.ebay.com/itm/372982266630?epid=1551008026&hash=item56d779bb06:g:~~4AAOSw2XJbjx1e

Those that need them can use them, and those that don't - well, they don't need to bother. It really depends mostly upon your turntable isolation (plus its inherent rumble) and if you have an arm/cartridge resonance mismatch. I have only encountered one vintage turntable where the use of these in-line filters was preferred, and it's a very powerful idler drive turntable removed from a radio station with giga-hours on it. The rumble vanishes with the filters and there is no other adverse sonic effect elsewhere in the audio spectrum.

As far as a mono switch goes, you can always use a pair of back to back Y-Cable adapters in your tonearm leads when you need Mono versus Stereo, and just unplug the back to back Y-Cable adapters to return to Stereo.
We have purchased a pair of these and will test them.
They appear to be a 6dB/octave simple high-pass filter. Yes, if this is all that is needed, that would be an alternative solution. Likewise, Y-adaptors on the turntable input for a Mono solution. Our internal switch parallels the input jacks similarly (although we use a 1 ohm standoff resistor to dampen any parasitics in the cabling).
 

theheavystuff

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This thread has been dormant for a bit, so apologies where due, but I’m posting in the interest of reviving it. I’m the proverbial n00b wrt to audio, and have found ASR to be a tremendous resource; Amir’s reviews of the Dayton MK402X and Aiyima A07 led me to purchase both, and I’m glad I did (I also donated when activating my account; money well spent).

I have an MM-5 on order, the only case where I’ve gone against Amir’s recommendation. I found Keith’s explanations of the trade offs inherent in audio design, and his preferences when confronted by them, rational and persuasive. In particular, being limited to budget equipment myself, the acceptance of some distortion (both inherent in vinyl media, and at times desirable as someone with vacuum tubes already present in my system) as a trade off for the headroom et al promised by the DL design, seems like the right trade off to make.

So bearing in mind that I’ve already bought the argument for the DL preamp and put my money where my mouth is, and am partly just killing time while I wait for my unit to arrive, I’d love to hear more about why and how I’m wrong, or not.

I appreciate you all, this is a tremendous resource for someone who wants to learn.
 

krichard2496

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This thread has been dormant for a bit, so apologies where due, but I’m posting in the interest of reviving it. I’m the proverbial n00b wrt to audio, and have found ASR to be a tremendous resource; Amir’s reviews of the Dayton MK402X and Aiyima A07 led me to purchase both, and I’m glad I did (I also donated when activating my account; money well spent).

I have an MM-5 on order, the only case where I’ve gone against Amir’s recommendation. I found Keith’s explanations of the trade offs inherent in audio design, and his preferences when confronted by them, rational and persuasive. In particular, being limited to budget equipment myself, the acceptance of some distortion (both inherent in vinyl media, and at times desirable as someone with vacuum tubes already present in my system) as a trade off for the headroom et al promised by the DL design, seems like the right trade off to make.

So bearing in mind that I’ve already bought the argument for the DL preamp and put my money where my mouth is, and am partly just killing time while I wait for my unit to arrive, I’d love to hear more about why and how I’m wrong, or not.

I appreciate you all, this is a tremendous resource for someone who wants to learn.
We've sold fewer of the MM-5's than the MM-6s (most popular so far) and the MP-7, but our return rate on the MM-5's is also the lowest of any model (not counting a number of trade-ins to the MM-6)...well under 2% (average for all models is <3%).

Also, parenthetically, we were corresponding with someone who was doing a distortion analysis of the actual signal coming from a Test LP, using an "Amir-approved' Cambridge Audio 5532-based preamp, and was seeing THD in the 10 to 12% region, most of it 2nd (and some 3rd), which seems to correspond to reality, and graphs shown long ago in stereo magazines.

Our contention is, in fact, that because distortion is multiplicative, our equipment's very low 3rd and higher THD (lower than most op-amp gear in fact) substantially prevents "harmonic multiplication" of the "inherent THD" of the record tracing process into the higher order harmonics which are so offensive to the human ear. And our 'well under 0.1%' 2nd HD is, in fact, generally inaudible as such....with most commentators believing than pure 2nd has to be 0.5% to 2% to reach audibility.
 
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theheavystuff

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We've sold fewer of the MM-5's than the MM-6s (most popular so far) and the MP-7, but our return rate on the MM-5's is also the lowest of any model (not counting a number of trade-ins to the MM-6)...well under 2% (average for all models is <3%).

Also, parenthetically, we were corresponding with someone who was doing a distortion analysis off of the signal from a Test LP, and was seeing THD in the 10 to 12% region, most of it 2nd (and some 3rd), which seems to correspond to reality, and graphs shown long ago in stereo magazines.

Our contention is, in fact, that because distortion is multiplicative, our equipment's very low 3rd and higher THD (lower than most op-amp gear in fact) substantially prevents "harmonic multiplication" of the "inherent THD" of the record tracing process into the higher order harmonics which are so offensive to the human ear. And our 'well under 0.1%' 2nd HD is, in fact, generally inaudible as such....with most commentators believing than pure 2nd has to be 0.5% to 2% to reach audibility.
That’s not surprising to me re your market; disposable income and obsessive online forum research would tend to inversely correlate. How many are 1) willing and able to spend money on an audiophile phono stage, but 2) cap their budget at $200?
 

krichard2496

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That’s not surprising to me re your market; disposable income and obsessive online forum research would tend to inversely correlate. How many are 1) willing and able to spend money on an audiophile phono stage, but 2) cap their budget at $200?
Some of it is quite related to economic conditions in different parts of the country, in terms of average disposable income. We started with an MM-3 at $99 which was a scaled-down MM-5, and we sold very few because of the perception of "what else we could do" (additionally it wasn't profitable) BUT we are thinking of bringing back a KIT that may interest DIY'ers, priced well below an MM-5.
 

theheavystuff

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Some of it is quite related to economic conditions in different parts of the country, in terms of average disposable income. We started with an MM-3 at $99 which was a scaled-down MM-5, and we sold very few because of the perception of "what else we could do" (additionally it wasn't profitable) BUT we are thinking of bringing back a KIT that may interest DIY'ers, priced well below an MM-5.
The kit idea is intriguing. I don’t solder, but why not start; I have a few years left before I’m 50.

I ended up looking at Darlington because there isn’t much info available about the onboard phono stage in the AT-LP120X, so I assume it’s equivalent to the sub-$100 op-amp based preamps, give or take. So I started looking at, e.g., the Mani and iFi level (and of course the Art), but they all seem uninspiring. For a few dollars more the MM-5 makes a lot of sense, and I’ll feel better about where my money is going. Also, Amir’s review describes exactly what will give me the most bang for my buck; the headroom and mono switch will improve my experience, but neither my equipment nor my ears are likely sensitive enough to register the distortion levels involved.
 

krichard2496

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The kit idea is intriguing. I don’t solder, but why not start; I have a few years left before I’m 50.

I ended up looking at Darlington because there isn’t much info available about the onboard phono stage in the AT-LP120X, so I assume it’s equivalent to the sub-$100 op-amp based preamps, give or take. So I started looking at, e.g., the Mani and iFi level (and of course the Art), but they all seem uninspiring. For a few dollars more the MM-5 makes a lot of sense, and I’ll feel better about where my money is going. Also, Amir’s review describes exactly what will give me the most bang for my buck; the headroom and mono switch will improve my experience, but neither my equipment nor my ears are likely sensitive enough to register the distortion levels involved.
Thank you for the perspective. On-board phono pre's - uninspiring. We are biased but would agree.

Re: Distortion. Short summary for newcomers to the thread.
It would only take us a couple of dollars to make the unit measure "good enough for Amir to recommend it" based on his non-ear-weighted measurements (e.g., operating our output stage in a differential mode would put 2nd harmonic distortion around 0.01% or lower but increase the 3rd).

We think - based on listening - that building it to suit Amir's simple measurement "makes it audibly sound worse."
That's why it is the way it is.
 

theheavystuff

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This is also an endorsement of Amir’s methods, by the way - I can’t give him a higher compliment than that I feel confident I’m disagreeing with him for the right reasons. Accurate information I can weigh as I see fit is the gold standard.
Thank you for the perspective. On-board phono pre's - uninspiring. We are biased but would agree.

Re: Distortion. Short summary for newcomers to the thread.
It would only take us a couple of dollars to make the unit measure "good enough for Amir to recommend it" based on his non-ear-weighted measurements (e.g., operating our output stage in a differential mode would put 2nd harmonic distortion around 0.01% or lower but increase the 3rd).

We think - based on listening - that building it to suit Amir's simple measurement "makes it audibly sound worse."
That's why it is the way it is.
I don’t think Amir is wrong; he reviewed the MM-5, and based on his review it’s the best in that market segment to my mind. His measurements are objective, recommendations are obviously subjective. Like I said, reading this thread sold me on Darlington.
 

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Darlington Labs, much like JDS labs, sets the bar for customer support and is reason enough to purchase from them.

I have a custom built - one off - dual output MP-7 on it's way with full trade in value for my MM-6, which Keith didn't hesitate to agree to build for me on trade. I'll now be able to, with the flip of a switch, send my audio to the PC for ripping or to my headphone amp for listening all without muddying the signal with some unknown quantity RCA switch box.
 

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I received my MM-5 on Monday, and it’s as expected. Build quality is excellent, and it sounds fantastic.

There’s no hum or other noise that I can detect, and I didn’t take any special care with placement or setup. It sits about 1/4” from my LP120x, with my Aiyima A07 and a tube preamp on top, in that order. Perfectly silent.

As Amir stated, the headroom handles pops and clicks very well; this is a huge benefit to me as I listen to a lot of battered old records. They’re there, but perfectly tolerable. I certainly can’t detect any distortion, but see above re: my equipment. It’s a modest setup, but sounds kind of incredible with the Darlington; I can’t imagine most people buying a sub $200 phono stage have a setup that would reveal distortion from this preamp.

I find the sound exceptional, granting the limits of my subjective opinion. Two things stand out: 1) the clarity is excellent, I thought bright at first but no, it’s just clear. I’m comparing it to the LP120X onboard preamp, granted, but hearing e.g. Brubeck humming along with his solo on a 50s mono record is pretty great. Not every snare drum hit sounds the same! 2) I was struck by the dynamics, with quiet parts playing detailed and clear, while louder passages have punch without being harsh. Is this due to the headroom? It’s a little hard to describe, but striking how well the loud/soft contrast presents, with both detailed and listenable. I listen to mostly jazz and classical, so the dynamic response is crucial.

You won’t believe it, but Keith is actually very engaged and attentive to clients. Lol just kidding - it’s an absolute pleasure doing business with him. Thanks to all who contributed to this thread.
 

krichard2496

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I received my MM-5 on Monday, and it’s as expected. Build quality is excellent, and it sounds fantastic.

There’s no hum or other noise that I can detect, and I didn’t take any special care with placement or setup. It sits about 1/4” from my LP120x, with my Aiyima A07 and a tube preamp on top, in that order. Perfectly silent.

As Amir stated, the headroom handles pops and clicks very well; this is a huge benefit to me as I listen to a lot of battered old records. They’re there, but perfectly tolerable. I certainly can’t detect any distortion, but see above re: my equipment. It’s a modest setup, but sounds kind of incredible with the Darlington; I can’t imagine most people buying a sub $200 phono stage have a setup that would reveal distortion from this preamp.

I find the sound exceptional, granting the limits of my subjective opinion. Two things stand out: 1) the clarity is excellent, I thought bright at first but no, it’s just clear. I’m comparing it to the LP120X onboard preamp, granted, but hearing e.g. Brubeck humming along with his solo on a 50s mono record is pretty great. Not every snare drum hit sounds the same! 2) I was struck by the dynamics, with quiet parts playing detailed and clear, while louder passages have punch without being harsh. Is this due to the headroom? It’s a little hard to describe, but striking how well the loud/soft contrast presents, with both detailed and listenable. I listen to mostly jazz and classical, so the dynamic response is crucial.

You won’t believe it, but Keith is actually very engaged and attentive to clients. Lol just kidding - it’s an absolute pleasure doing business with him. Thanks to all who contributed to this thread.
Thank you, sir.

If pressed for a response, we would say that you are hearing the "lack" of distortions that are audible and unpleasant to the ear, especially those substantial higher harmonics from other units that are generated under conditions of transient peaks (via cartridge mistracking, and surface noise).

Amir measured those at the equivalent of about -103dB, or 0.0007% 3HD and higher...and because of our very high headroom, those higher harmonics stay far down below the desired signal as levels rise to greater than normal. 4HD (fourth harmonic) we estimate at -120dB or 0.0001% although it is largely obscured by noise, with higher orders continuing to sharply decrease.

Lastly, you are also experiencing the general "inaudibility" of the slightly measurable -65dB, or ~0.05% 2HD (2nd harmonic) from our unit, which is nearly completely masked by the ear's own low-order distortion.

It is very instructive to put our unit on a spectrum analyzer and feed it a simple 1 kHz tone, and then raise the level in steps above nominal...to +5dB, +10dB, +15dB, +20dB, and +25dB. Our harmonic spectrum stays nice and clean and downward sloping, while competitors will begin to show a near-stairstep rise in these higher harmonics at levels well below our actual overload (clip). Imagine what is happening when your stylus encounters a large tick or pop at > +20dB above nominal level, or the case when your stylus is flailing around a worn groove, bouncing from side to side, losing contact with the groove wall and recontacting it with the resulting sharp transient hundreds of times per second. Would you rather have high headroom and a natural, graceful overload characteristic, or instead, a unit that was made to look good on a single number on a basic test tone at nominal level?

I personally sold an early vacuum-cleaning record machine about 15 years ago in a move, and never felt the need to replace it. I still keep the 1988 Discwasher set in the plastic case, with it's Zerostat and SC-2 fluid and brush, but mainly for looks, not ever for daily use.
 
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