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Darlington Labs MM-5 Review (Phono Stage)

amirm

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#1
This is a review and detailed measurements of the Darlington Labs MM-5 Moving Magnet phono pre-amplifier. It was kindly purchased new by a member and drop shipped to me. It has a few options but as purchased, it costs US $199 from the company.

The front panel doesn't look half bad for a budget device:

Darlington Labs MM-5 review phono stage amplifier.jpg


The back side, not so much:

Darlington Labs MM-5 review phono stage back panel.jpg


While the RCA connectors are high quality, the labeling and input power hole are as Dave Jones would say, "how you doing."

I must confess the name Darlington takes me back decades to my childhood when I was learning electronics. Darlington is a simple pairing of two transistors where their gain multiplies almost like magic. I would always have a smile on my face when I would spot it in a circuit diagram.

Here, I am not sure if any Darlington circuit is used or not. Company says it uses J-FET discrete class A amplifier with no feedback. I suspect we are going to see plenty of distortion.

Darlington Labs MM-5 Measurements
With only moving magnet supported, our job here is pretty simple as far as measurements starting with our dashboard:

Darlington Labs MM-5 Measurements.png


We have two problems here. One is mains and harmonics which I could not get to change one bit no matter how I grounded things. And quite high second harmonic distortion as we expected. Ranking therefore is quite low:

best phono stage review 2021.png


Company makes up for that partially with good implementation of RIAA equalization:

Darlington Labs MM-5 frequency response Measurements.png


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.

I was really impressed by the high level of headroom available:

Darlington Labs MM-5 THD+N vs Level Measurements.png


Immunity to pops and clicks should be good then.

What distortion there is, is almost constant with frequency which is good:

Darlington Labs MM-5 THD vs frequency Measurements.png


Conclusions
A design choice was made to leave feedback behind which then resulted in quite elevated distortion. Usually we don't see any distortion spikes in decently implemented phono stages with SINAD completely dominated by noise. Not here. There is plenty of distortion but it is second order so maybe folks can feel good about that. Given the high distortion of the LP media itself, I decided to not be too critical of that and assign some weight to nice headroom and decent RIAA implementation.

Of note, company provides pretty accurate measurements that correlate well with mine. Kudos on that.

Personally I can't recommend the Darlington Labs MM-5. You can choose otherwise with the data provided.

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
OP
amirm

amirm

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Thread Starter #5
No. One is broken or seems that way. And the other is a speaker and I need to listen to it more tomorrow before posting.
 

restorer-john

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#7
The headroom (THD vs input level) test is done at 1kHz? 100mV at 1% is not great, but we've seen a lot worse.
 
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#8
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.

Isn't this like, very, very bad especially with smaller speakers?
 

Helicopter

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#14
Thanks Amir.

I am always interested in this category, but so far the only products tested that might compliment or replace my little NAD PP2 are the Puffin and the Duo.

Seems there is no shortage of >$100 products in the category that are outperformed by the $66 DJPREII. This example is another loser.
 
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#15
This is a review and detailed measurements of the Darlington Labs MM-5 Moving Magnet phono pre-amplifier. It was kindly purchased new by a member and drop shipped to me. It has a few options but as purchased, it costs US $199 from the company.

The front panel doesn't look half bad for a budget device:

View attachment 143208

The back side, not so much:

View attachment 143209

While the RCA connectors are high quality, the labeling and input power hole are as Dave Jones would say, "how you doing."

I must confess the name Darlington takes me back decades to my childhood when I was learning electronics. Darlington is a simple pairing of two transistors where their gain multiplies almost like magic. I would always have a smile on my face when I would spot it in a circuit diagram.

Here, I am not sure if any Darlington circuit is used or not. Company says it uses J-FET discrete class A amplifier with no feedback. I suspect we are going to see plenty of distortion.

Darlington Labs MM-5 Measurements
With only moving magnet supported, our job here is pretty simple as far as measurements starting with our dashboard:

View attachment 143210

We have two problems here. One is mains and harmonics which I could not get to change one bit no matter how I grounded things. And quite high second harmonic distortion as we expected. Ranking therefore is quite low:

View attachment 143211

Company makes up for that partially with good implementation of RIAA equalization:

View attachment 143212

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.

I was really impressed by the high level of headroom available:

View attachment 143213

Immunity to pops and clicks should be good then.

What distortion there is, is almost constant with frequency which is good:

View attachment 143214

Conclusions
A design choice was made to leave feedback behind which then resulted in quite elevated distortion. Usually we don't see any distortion spikes in decently implemented phono stages with SINAD completely dominated by noise. Not here. There is plenty of distortion but it is second order so maybe folks can feel good about that. Given the high distortion of the LP media itself, I decided to not be too critical of that and assign some weight to nice headroom and decent RIAA implementation.

Of note, company provides pretty accurate measurements that correlate well with mine. Kudos on that.

Personally I can't recommend the Darlington Labs MM-5. You can choose otherwise with the data provided.

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Amir - looks like headroom is almost 30 db at clipping relative to a 5 mv input. (20 x Log (154/5)). How does than compare to other phono preamps you have tested. Also, can you plot headroom by frequency? Something like your multi-tone test for DACs except the vertical axis is in db at clipping. Compared to another preamp with better SINAD but much lower overload - do you hear a difference with critical listening? This may be source material dependent - as is full scale music versus compressed music.
 

krichard2496

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#16
This is a review and detailed measurements of the Darlington Labs MM-5 Moving Magnet phono pre-amplifier. It was kindly purchased new by a member and drop shipped to me. It has a few options but as purchased, it costs US $199 from the company.

The front panel doesn't look half bad for a budget device:

View attachment 143208

The back side, not so much:

View attachment 143209

While the RCA connectors are high quality, the labeling and input power hole are as Dave Jones would say, "how you doing."

I must confess the name Darlington takes me back decades to my childhood when I was learning electronics. Darlington is a simple pairing of two transistors where their gain multiplies almost like magic. I would always have a smile on my face when I would spot it in a circuit diagram.

Here, I am not sure if any Darlington circuit is used or not. Company says it uses J-FET discrete class A amplifier with no feedback. I suspect we are going to see plenty of distortion.

Darlington Labs MM-5 Measurements
With only moving magnet supported, our job here is pretty simple as far as measurements starting with our dashboard:

View attachment 143210

We have two problems here. One is mains and harmonics which I could not get to change one bit no matter how I grounded things. And quite high second harmonic distortion as we expected. Ranking therefore is quite low:

View attachment 143211

Company makes up for that partially with good implementation of RIAA equalization:

View attachment 143212

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.

I was really impressed by the high level of headroom available:

View attachment 143213

Immunity to pops and clicks should be good then.

What distortion there is, is almost constant with frequency which is good:

View attachment 143214

Conclusions
A design choice was made to leave feedback behind which then resulted in quite elevated distortion. Usually we don't see any distortion spikes in decently implemented phono stages with SINAD completely dominated by noise. Not here. There is plenty of distortion but it is second order so maybe folks can feel good about that. Given the high distortion of the LP media itself, I decided to not be too critical of that and assign some weight to nice headroom and decent RIAA implementation.

Of note, company provides pretty accurate measurements that correlate well with mine. Kudos on that.

Personally I can't recommend the Darlington Labs MM-5. You can choose otherwise with the data provided.

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Thank you Amir for the review.

The single-ended Class-A feedback-free gain circuitry is a conscious design choice.
We could have chosen differential-operation of the gain stages and still not used feedback; the result would be around -70dB to -80dB second harmonic distortion.

As it is, we could also 'optimise' the second harmonic and lower it a few dB by trading off some overload headroom. Doing so in our ear leads to a brightened, forward, more strident quality and increases the relative proportion of the third harmonic. Also note that unlike other units which also use Passive-RIAA EQ, our special design avoids an increase in High Frequency distortion due to overload of the input stage.

Third harmonic at ~ -103dB as tested is a goal which we worked hard to achieve. Lastly, unlike some other "no feedback" units, our models have a low-impedance output that interface well with most gear. The residual mains harmonics are NOT related to a noisy regulation scheme; they are induced due to the size of the enclosure, and with A-weighting being typical of the ear's response, are inaudible in normal conditions.

Our listening tests lead us to the current design.
We have a 30 day return option for all clients to audition the unit (or our other higher-end models) in their own system.

Sincerely,
Keith Richardson
Director of Engineering
Darlington Labs LLC
 

Helicopter

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#17
Thank you Amir for the review.

The single-ended Class-A feedback-free gain circuitry is a conscious design choice.
We could have chosen differential-operation of the gain stages and still not used feedback; the result would be around -70dB to -80dB second harmonic distortion.

As it is, we could also 'optimise' the second harmonic and lower it a few dB by trading off some overload headroom. Doing so in our ear leads to a brightened, forward, more strident quality and increases the relative proportion of the third harmonic. Also note that unlike other units which also use Passive-RIAA EQ, our special design avoids an increase in High Frequency distortion due to overload of the input stage.

Third harmonic at ~ -103dB as tested is a goal which we worked hard to achieve. Lastly, unlike some other "no feedback" units, our models have a low-impedance output that interface well with most gear. The residual mains harmonics are NOT related to a noisy regulation scheme; they are induced due to the size of the enclosure, and with A-weighting being typical of the ear's response, are inaudible in normal conditions.

Our listening tests lead us to the current design.
We have a 30 day return option for all clients to audition the unit (or our other higher-end models) in their own system.

Sincerely,
Keith Richardson
Director of Engineering
Darlington Labs LLC
Interesting. No doubt some people will enjoy that distortion, and that it should be fairly benign. It should sound like some of the common tube based circuits. If it had some pretty glowing tubes on top, it would be more interesting to me. Not sure I would want the noise with sensitive speakers though.

Thanks for chiming in and welcome to ASR!

@AdamG247 can someone get this guy a badge? ;)
 

AdamG247

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#18
Interesting. No doubt some people will enjoy that distortion, and that it should be fairly benign. It should sound like some of the common tube based circuits. If it had some pretty glowing tubes on top, it would be more interesting to me. Not sure I would want the noise with sensitive speakers though.

Thanks for chiming in and welcome to ASR!

@AdamG247 can someone get this guy a badge? ;)
Request submitted to Amir for consideration and action. Thank you @Helicopter for bringing this to our attention. :cool:
 

DSJR

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#19
Thank you Amir for the review.

The single-ended Class-A feedback-free gain circuitry is a conscious design choice.
We could have chosen differential-operation of the gain stages and still not used feedback; the result would be around -70dB to -80dB second harmonic distortion.

As it is, we could also 'optimise' the second harmonic and lower it a few dB by trading off some overload headroom. Doing so in our ear leads to a brightened, forward, more strident quality and increases the relative proportion of the third harmonic. Also note that unlike other units which also use Passive-RIAA EQ, our special design avoids an increase in High Frequency distortion due to overload of the input stage.

Third harmonic at ~ -103dB as tested is a goal which we worked hard to achieve. Lastly, unlike some other "no feedback" units, our models have a low-impedance output that interface well with most gear. The residual mains harmonics are NOT related to a noisy regulation scheme; they are induced due to the size of the enclosure, and with A-weighting being typical of the ear's response, are inaudible in normal conditions.

Our listening tests lead us to the current design.
We have a 30 day return option for all clients to audition the unit (or our other higher-end models) in their own system.

Sincerely,
Keith Richardson
Director of Engineering
Darlington Labs LLC

I do wish I could discuss with you on more of an equal level to yourself, but I can't, so profuse apologies..

I do have to ask though, what is all this about low or zero feedback in the audiophile community, when other makers seem to use it carefully (local, global and possibly carefully adjusted amounts of both) and get a superb performance and 'great sound' as well. I'm not a Bruno Putzeys disciple as such, but he seems to feel feedback isn't the enemy it's been made out to be, but he's designing power amp circuits and not to my knowledge, phono stages.

After that possibly too-naive question above, I must congratulate you on a nice high overload margin, as that's one thing that I feel many vinyl lovers aren't aware of - the effects of a phono stage momentarily overloading on surface ticks and splats and making it appear subjectively worse than it really is.
 

Vini darko

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#20
Thank you Amir for the review.

The single-ended Class-A feedback-free gain circuitry is a conscious design choice.
We could have chosen differential-operation of the gain stages and still not used feedback; the result would be around -70dB to -80dB second harmonic distortion.

As it is, we could also 'optimise' the second harmonic and lower it a few dB by trading off some overload headroom. Doing so in our ear leads to a brightened, forward, more strident quality and increases the relative proportion of the third harmonic. Also note that unlike other units which also use Passive-RIAA EQ, our special design avoids an increase in High Frequency distortion due to overload of the input stage.

Third harmonic at ~ -103dB as tested is a goal which we worked hard to achieve. Lastly, unlike some other "no feedback" units, our models have a low-impedance output that interface well with most gear. The residual mains harmonics are NOT related to a noisy regulation scheme; they are induced due to the size of the enclosure, and with A-weighting being typical of the ear's response, are inaudible in normal conditions.

Our listening tests lead us to the current design.
We have a 30 day return option for all clients to audition the unit (or our other higher-end models) in their own system.

Sincerely,
Keith Richardson
Director of Engineering
Darlington Labs LLC
Welcome to ASR always good to see manufacturers getting involved.
 
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