Michael Fidler Spartan 20 Phono Stage Review

[amirm]

This is a review and detailed measurements of the Michael Fidler Spartan 20 Moving Coil and Magnet phono preamp. It was sent to me by the company and costs £500/€600/$670.

Is it me or is the On/Off upside down? I am used to On being up, not down. That nit aside, there are LP noise mitigation facilities such as mono conversion and dual frequency cross feed. Unlike many other phono preamplifiers, there are independent moving coil and magnet inputs:

I appreciate the upside down additional labeling when you are trying to change things and doing it from above. Nice to see the range of input voltages as well.

Best part of the design is what is on Michaels's site:

That is one pretty looking PC board! The box badly needs a clear top for this to be appreciated in use.

ICs are socketed but company mentions that is only for repair and not silly "op amp rolling."

Spartan 20 Moving Magnet Preamp Measurements
As usual we start with our dashboard with fair bit of optimization on my part to minimize ground loops:

Nice to see no distortion and only hint of power supply noise. This easily lands the Spartan 20 in our upper tier ranking of phono stages:

What is absolutely superb is the frequency response:

It doesn't get better than this folks. Not only the equalization perfect but so is channel matching. We also have a proper high pass filter to get rid of LP rumble.

There is a crossfeed function for noise reduction but I am unclear as to whether this is the optimal implementation or not:

Another excellent aspect of this phono stage is the way it almost doesn't care what the frequency is when it comes to overload:

Most phono stages lose substantial amount of their headroom at high frequencies which is where you need it when it comes to ticks and pops. Not here. You have that nearly 100mv at all frequencies.

Distortion is admirably kept low:

Spartan 20 Moving Coil Measurements
Let's look at our dashboard:

Due to much higher gain, it is hard to completely minimize mains noise. What we have is respectable anyway.

Same excellent overload characteristic is provided for moving coil:

I already showed you the distortion vs frequency in previous section.

Conclusions
I don't know any other phono stage designer that is so focused on engineering excellence as Michael. Spartan 20 is another evidence of that with execution that borders on perfection. You pay some premium of course but considering the device is manufactured in the UK, I think that is justified.

I am happy to recommend Michael Fidler Spartan 20.

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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/

 

[polmuaddib]

Thanks for the review.
I will never understand why people prefer MC over MM.
Don't all these measured Phono stages perform better with MM?
Don't we want better SINAD at all times?
There is some gap in my knowledge or I am missing something surely.

 

[Endibol]

Is it me or is the On/Off upside down? I am used to On being up, not down.

This is the definition used for switches in the Common Wealth countries (UK, India, Australia etc.).

 

[phoenixdogfan]

I wonder if maybe the need for higher gain moving coil phono stage with concomitantly poorer noise and distortion numbers might better be addressed with a step up transformer like the Mitch Cotter MC-1, which could passively step up output voltage to match with a conventional moving magnet phono stage and perhaps avoid the penalty in higher noise levels?

 

[Michael Fidler]

Thanks for the review.
I will never understand why people prefer MC over MM.
Don't all these measured Phono stages perform better with MM?
Don't we want better SINAD at all times?
There is some gap in my knowledge or I am missing something surely.

I keep trying to tell people this very thing - but nobody seems to take any heed ! The high-output MC cartridges are excellent, but the market loves these troublesome low-output devices for reasons that escape me most of the time:

https://www.audiosciencereview.com/...cartridges-is-the-former-really-better.59088/

I wonder if maybe the need for higher gain moving coil phono stage with concomitantly poorer noise and distortion numbers might better be addressed with a step up transformer like the Mitch Cotter MC-1, which could passively step up output voltage to match with a conventional moving magnet phono stage and perhaps avoid the penalty in higher noise levels?

Unfortunately, I can confirm on my end that these mains spikes/noise always seem to appear when connecting a non-isolated MC input to an audio analyser, even one with electronically floated outputs. The gain is so high at 80dB for 50/60Hz that even the slightest induced current in the reference/cable shield path, or leakage through the analyser, will skew the measurement downwards by 6dB or more. When connecting 10 ohm RCA plugs (to mimic coil resistance), or a floating moving-coil cartridge shielded by a turntable's separate ground drain, you do get the rated 77dB from 220Hz to 22kHz or 74dB from 22Hz to 22kHz. From my notes file:

Full noise measurements (dBV readings) - MC HEAD

DC to 22kHz 79dBV
22Hz to 22kHz 79dBV
220Hz to 22kHz 82dBV
A-weighted 83dBV

Therefore A-weighted SNR is 78dB or so...

Cartridge loader on MM...

DC to 22kHz 83dBV (78dB SNR)
22Hz to 22kHz 83dBV (78dB SNR - maybe use this figure in the manual?)
220Hz to 22kHz 84.3dBV (79dB SNR)
A-weighted 85.5dBV (80.3dB SNR)

I've found that using an RCA/inline L-pad attenuator of some -40dB for measurements, with the series resistor in series with the centre pin of the input connector, and the shunt resistor soldered straight across the centre pin of the output connector can mitigate this greatly, as the the attenuator reference shares the shortest path possible with the internal reference point of the input amplifier.

Using a transformer would isolate the input and stop the loop currents from affecting the reference, but it's not a problem most of the time in real MC setups. I am considering this solution for a high-end product (with electronic compensation for the typical transformer response anomalies at the top and bottom of the response), though, as the isolation can make some of the most hideous LOMC setup issues (made worse by the tiny nominal level) quite innocuous. Handy from a 'customer service' point of view!

Looks like I'll have to finish off the web-page now before someone notices the 'More text...', and 'Further chatter...' paragraphs on the specification section.

Thanks @amirm for the excellently detailed review! Extremely sensible commentary on the unfortunate phenomenon known as 'op-amp rolling'.

 

[fordiebianco]

Good morning from the British Isles.

Great to see that a dedicated individual with the obvious engineering nous can create a no-nonsense piece of kit without Schwurbel and Woo that measures perfectly and is even affordable.

Puts the rest of the British audiophile cottage industry to shame.

Nice work and thanks for the review @amirm.

 

[The_Lecht_Rocks]

Delighted with my recent charcoal grey Spartan 15 mk2 being fed from Roksan Attessa into Cambridge EXA100.
It suits the combination brilliantly…
Also tested it with my Planar 6 into my NAIT 50 but prefer the sound of RP6 direct to N50 phono stage.

 

[welwynnick]

Thanks for the review.
I will never understand why people prefer MC over MM.

Er ... because they sound better?

Anyway, nice one, Michael. I will update my chart.

It's the next test that I'm looking forward too.

 

[MaxwellsEq]

Is it me or is the On/Off upside down?

Not if you're from the UK - down is always on. However, from a safety point of view I often feel the US way is better, since if you slip you will switch something off rather than on!

 

[Sokel]

That PCB is good enough to eat!
And it fortunately reflects the quality of this phono measurement-wise.

(you should make one in black too )

Thanks Amir!

 

[sergeauckland]

Not if you're from the UK - down is always on. However, from a safety point of view I often feel the US way is better, since if you slip you will switch something off rather than on!

Similarly, with mixer faders. The BBC has its faders going up for off, the joke being that if a Presenter dies on duty, the last thing they do as they slump over the console is to fade down the open channel...

S

 

[Grotti]

Zoomed in on the PCB as much as I could: beautiful! I would order it in an instance if I was in the market for a phono preamplifier right now. And it's another example of how important ASR is: who would have known about the technical perfection of this device without this platform?

I hope you will sell tons of it, Michael!

 

[Rja4000]

Thanks for this review.

The gain (and performance ?) is a bit lower than for his specialized MC preamp, isn't it ?

Classic Audio MC Pro Phonostage Review

This is a review and measurements of the Classic Audio MC Pro by Michael Fidler. It was sent to me by the company and costs US $850 (£650/€750). As non-fancy enclosures go, this is pretty nice looking and with some unusual features such as low frequency blending to reduce noise, mono switch and...

www.audiosciencereview.com

 

[welwynnick]

Thanks for this review.
The gain (and performance ?) is a bit lower than for his specialized MC preamp, isn't it ?

Classic Audio MC Pro Phonostage Review

This is a review and measurements of the Classic Audio MC Pro by Michael Fidler. It was sent to me by the company and costs US $850 (£650/€750). As non-fancy enclosures go, this is pretty nice looking and with some unusual features such as low frequency blending to reduce noise, mono switch and...

www.audiosciencereview.com

Agreed, but it does have an MM input as well, and it's cheaper. Here's where the Spartan 20 sits in my updated chart (sorry about the dates). Since there's usually a direct trade-off between gain and SNR, this adds together gain and SINAD to give a total which is a sort of figure of merit. The chart is ordered by MC total.
EDIT: Dates fixed.

 

[Drengur]

Not if you're from the UK - down is always on. However, from a safety point of view I often feel the US way is better, since if you slip you will switch something off rather than on!

I was going to point this out. Is it the same with high power devices?

 

[LTig]

Thanks for the review.
I will never understand why people prefer MC over MM.

IME pops and clicks are less audible, sounds closer to digital.

Don't all these measured Phono stages perform better with MM?
Don't we want better SINAD at all times?

In real use with my AT33ptg/2 (0.4 mV) and both my old DIY MC phono stage and the Cambridge Audio Duo the vinyl noise of my best and cleanest records is much higher than the electronics.

Raise the volume until you hear the records groove noise, then lift the arm. If there is no audible noise you're good - no need to chase for higher SNR.

 

[SIY]

I wonder if maybe the need for higher gain moving coil phono stage with concomitantly poorer noise and distortion numbers might better be addressed with a step up transformer like the Mitch Cotter MC-1, which could passively step up output voltage to match with a conventional moving magnet phono stage and perhaps avoid the penalty in higher noise levels?

Input transformers are an almost ideal solution and allow balanced connection. BUT... in order to realize good performance, the circuit has to be tailored to the specific cartridge being used. One size fits all outboard units never do this so are almost always suboptimal.

 

[Thomas_A]

Seems to have the features needed and good measurements as well. I am a bit perplexed by the mono bass filter though. I had expected a bit more steep filter. I use a Muffsy preamp + KAB RF1 filter.

 

[LTig]

The chart is ordered by MC total.

https://www.audiosciencereview.com/forum/index.php?reviews/​ Brand	Model	Price USD	SINAD	GAIN	TOT	SINAD	GAIN	TOT	Rec'd	Review Date	Review Link
MM	MM	MM	MC	MC	MC
Classic Audio	MC Pro	$850			0​	73​	68​	141​	Yes	8/13/23	Review Link
Pyxi	$300	80​	46​	126​	65​	59​	124​	Yes	5/27/23	Review Link
Cambridge Audio	Alva Duo	$300	84​	39​	123​	63​	60​	123​	Yes	7/24/23	Review Link
		​

Shouldn't the first SINAD/GAIN/TOT group be labeled as MM instead of MC?

 

[welwynnick]

Shouldn't the first SINAD/GAIN/TOT group be labelled as MM instead of MC?

Quite right. It's corrected now. You can see the attached spreadsheet was correct.