Michael Fidler Spartan 20 Phono Stage Review

[Michael Fidler]

I wonder how much this is a problem in practice. I have user replacable caps but use none while cabling add around 28 pF for the tonearm and about 100 pF for the RCA cable. I’ve never experienced any RFI problems though.

Probably the quick-and-dirty solution, then... Just use a big resistor of a couple of kOhms in series with input amplifier.

It's noisy, but it does the job. See link below for an example (R2L):

https://sound-au.com/project06.htm

EDIT - not even the biggest source of noise in that design. R5L at 4k7 makes me wince with the power of a million limes.

 

[sergeauckland]

Do they, do they really these days?

I don't know. Over the years, I've changed to low output MCs really because I drove myself nuts fiddling with the load on MMs and getting poor results every time, with each change in loading, the frequency response was different, but still wrong. At least with MCs, what you get is what it does. Fiddling with loading makes no noticeable difference.

One of my cartridges (EMT TSD15) is somewhere in between a LOMC and HOMC, as it has a 1mV output at 5cm/sec and a coil resistance of 20 ohms if I remember rightly.

Whether I load it at 470 ohms or 47k ohms makes no difference to the frequency response, nor does any sensible amount of capacitance.

On the other hand, my Shure V15-VMR (fitted with SAS stylus) is very fussy about loading, which is why I either use it as it is and don't bother to measure what it's doing as it'll only upset me, or it stays in its box.


S.

 

[ElJaimito]

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

Transient response due to lower moving mass. Ideally, of course! And only for the first ~ 100 plays of a disk (wild guess, hugely variable). But the best MM beat average MC... and I prefer digital anyway, none of this messing about.

 

[DSJR]

I don't know. Over the years, I've changed to low output MCs really because I drove myself nuts fiddling with the load on MMs and getting poor results every time, with each change in loading, the frequency response was different, but still wrong. At least with MCs, what you get is what it does. Fiddling with loading makes no noticeable difference.

One of my cartridges (EMT TSD15) is somewhere in between a LOMC and HOMC, as it has a 1mV output at 5cm/sec and a coil resistance of 20 ohms if I remember rightly.

Whether I load it at 470 ohms or 47k ohms makes no difference to the frequency response, nor does any sensible amount of capacitance.

On the other hand, my Shure V15-VMR (fitted with SAS stylus) is very fussy about loading, which is why I either use it as it is and don't bother to measure what it's doing as it'll only upset me, or it stays in its box.


S.

Only trouble is, the JAS stylus for the V15VMR does alter the response I believe (if VE posts are anything to go by). I loved mine dearly and was heartbroken when the cantilever was accidentally damaged (and not by me either!!!). The fracture is right at the hinge point, so no idea if a facility such as Expert Stylus Co. could repair it as the diamond itself is rather low hours. Whatever, it'd cost many hundreds to repair or properly replace and I very much doubt it's sound the same For now, a 'Super' OM30 will do, and a mint Sonus Blue for 'best' (ignoring the post 18kHz response peak).

Loads more to add, but it'd drift this review too far off. I'd love one of these phono stages as a final one-off box to do the job, but for me, a Spartan 5 would do what I need, should I ever have the chance to play vinyl in quantity again (I like the format in a tactile way, accepting the objective weaknesses which careful set-up can minimise well I think still).

P.S. The lf filter is how it SHOULD be done I think, as long as it doesn't have phase or whatever effects a little further up (talking out my backside again I suspect).

 

[DSJR]

Perhaps it is analogous to the preference for vinyl itself. Fussy, inconvenient, expensive, and delicate equipment with bad sound quality and nostalgic vibes.

WOAH there

I've owned a CD player since 1985 and nearly bankrupted myself over the next few years with the credit card over buying discs to feed it - and they were expensive back then!

Vinyl DOES NOT have to sound bad - AT ALL - as modern pickups and turntable systems, if properly set up, can sound really good. Look on Youtube at the Spartan 5 post using a VM95ML mounted in a £400 or so AT LP5X deck and played through a Spartan 5. I know the music is simple, but background noise is low and using my 'tune dem' conditioning of old, the 'tone' is very 'musical' (runs for cover ).

 

[Bland_username42069]

I’m sure someone does one , but is there an unequalised mm board that can be mounted in the turntable? Personally I’d like line out to a Dac so I use its PEQ to play anything I want in the best quality whilst taking an unequalised feed to a pc without ever having to think about the stressful world of phono stages again.

(I’m assuming that would give the best quality?)

 

[NHL99]

Owned a https://leema-acoustics.com/project/essential/ which had an impressive sound. Would be interesting to see comparison.

Moving magnet gain: 36 dB
Moving coil gain: 62 dB
Frequency Response: 20 Hz to 20 kHz (+/- 0.5 dB ref > RIAA curve)
Distortion: Less than 0.02% (@ 1 kHz)
Residual noise (MM): Better than -86 dBA (input short circuit)
Residual noise (MC) | Better than -75 dBA input short circuit
Headroom: Greater than +26 dB @ 1 kHz
High pass filter: -3 dB @ 20 Hz
Dimensions (wdh): 113*102*60mm
Carton: 320*160*110mm
Mass: 1.1Kg

 

[Thomas_A]

Probably the quick-and-dirty solution, then... Just use a big resistor of a couple of kOhms in series with input amplifier.

It's noisy, but it does the job. See link below for an example (R2L):

https://sound-au.com/project06.htm

EDIT - not even the biggest source of noise in that design. R5L at 4k7 makes me wince with the power of a million limes.

It's a rather conventional design.

Schematics | Muffsy Phono Kits

www.muffsy.com

Measures like this

Muffsy phono preamplifier mini review (update)

This review was updated September 21, 2023. Main change was the use of the E1DA Scaler to fix the impedance issues that is evident when using the E1DA ADC alone. This is an attempt to make a small review with measurements of the Muffsy MM phono preamplifier. It is a DIY kit so it is far from...

www.audiosciencereview.com

 

[cgallery]

The U.S. Military specs call for up=on/down=off. Also, right=on, left=off. Also, CW=more, CCW (or ACW for many reading this)=less.

You can google and read-up on this, a lot of the reasoning is sound (no pun intended).

 

[Michael Fidler]

It's a rather conventional design.

Schematics | Muffsy Phono Kits

www.muffsy.com

Measures like this

Muffsy phono preamplifier mini review (update)

This review was updated September 21, 2023. Main change was the use of the E1DA Scaler to fix the impedance issues that is evident when using the E1DA ADC alone. This is an attempt to make a small review with measurements of the Muffsy MM phono preamplifier. It is a DIY kit so it is far from...

www.audiosciencereview.com

So we have a 300R stopper resistor. Not much for impeding RFI, but also not too bad in terms of noise contribution... I wouldn't like to try this for a commercial product, but each to his own.

Of more concern, IMO, is the front end gain is fixed at 30.6dB; flat for the passive RIAA network that follows. This means that if the gain is set for 41dB (300R in parallel with 180R for the second amplifier stage), we are going to see premature clipping/overload occurring at 6.5kHz, at which point the overall gain will drop below the gain of the first stage, compromising overload margin.

At 10kHz, the overall gain of an RIAA preamp with a nominal 1kHz gain of 41dB will be 27.4db, so with 30.6dB of gain in the first stage, it's evident that we are going to be losing 5.2dB of headroom exactly where we want as much as possible due to clicks and pops...

 

[mike70]

Vinyl DOES NOT have to sound bad - AT ALL

generally, the opinions about "bad sound", "high noise and clicks and pops", etc etc comes from people without experience in modern analog systems.

i listen to vinyl since 70s and i never (never) have had the SQ in vinyl that i can have today.
microline cartridge / stylus under 200 USD?
high quality external preamps under 300 USD?
infrasonic record cleaning machines under 400 USD?
high quality recordings? (i don´t remember Mofi editions on that time)

i mean, it's not a cheap or convenient format, not at all, since i can remember ... but can sound great, totally. For those who enjoy the experience, worth it, oh yes.

 

[Thomas_A]

So we have a 300R stopper resistor. Not much for impeding RFI, but also not too bad in terms of noise contribution... I wouldn't like to try this for a commercial product, but each to his own.

Of more concern, IMO, is the front end gain is fixed at 30.6dB; flat for the passive RIAA network that follows. This means that if the gain is set for 41dB (300R in parallel with 180R for the second amplifier stage), we are going to see premature clipping/overload occurring at 6.5kHz, at which point the overall gain will drop below the gain of the first stage, compromising overload margin.

At 10kHz, the overall gain of an RIAA preamp with a nominal 1kHz gain of 41dB will be 27.4db, so with 30.6dB of gain in the first stage, it's evident that we are going to be losing 5.2dB of headroom exactly where we want as much as possible due to clicks and pops...

With respect to headroom, it clips around 120 mV @ 1 kHz and 44 dB gain. I have not xperienced much problems but then I do not own many records with loud clicks and pops. Heavy damaged records get discarded. I am more concerned to adjust loading since it is clearly audible and there are not many cheap preamps with this feature.

 

[abrcdbra]

Because, while most audio op-amps such as the NJM2068 and NE5534 have excellent RFI handling in an audio setup .....

Well, yes. Yes.
2068 is the cheapest OPA for audio now. From this point of view, it is excellent for the manufacturer. But no more than that. And there are simply no really good OPAs for use in the RIAA corrector in the DIP8 case now. Sorry)
But the marketing strategy is great, and the color scheme of the filling looks lovely to the eye. Respect!

 

[BeeKay]

Circuit breakers are down for off though.

True for Germany and central breaker panels (we don’t have switches per power outlet integrated to the socket)

 

[Michael Fidler]

With respect to headroom, it clips around 120 mV @ 1 kHz and 44 dB gain. I have not xperienced much problems but then I do not own many records with loud clicks and pops. Heavy damaged records get discarded. I am more concerned to adjust loading since it is clearly audible and there are not many cheap preamps with this feature.

I may have to challenge that figure... If you were to amplify by 44dB and have 120mV of (peak) headroom at the input, then you'd need an output level of a whopping 19V peak.

This unit seems to have a 15V split supply (LM311/337 regulators running 300 and 3600 ohm set resistors), so most op-amps would top out around 14V.

 

[Thomas_A]

I may have to challenge that figure... If you were to amplify by 44dB and have 120mV of (peak) headroom at the input, then you'd need an output level of a whopping 19V peak.

This unit seems to have a 15V split supply (LM311/337 regulators running 300 and 3600 ohm set resistors), so most op-amps would top out around 14V.

It might be a misprint on the PCB. New version says 32-38-40-43 for low-medium-high-max gain while old version says 36-40-44-46 dB. I measured it in high gain which means 40 or 44 dB. I think resistors were changed while the old PCB print was there. Otherwise math does not compute as you say. Anyway, it clips above 120 mV as seen in measurments which could be ≈14 V out with 40 dB gain.

 

[WDeranged]

@Michael Fidler Congratulations on another excellent preamp. I notice you have a Spartan 15 mk2 available now, what changes did you make?

 

[abrcdbra]

I may have to challen ...

Sorry, I want to understand the sound quality of your RIAA preamplifier. Therefore, I ask about the quality of the radio components that you used. Burgundy capacitors are not Chinese noname? What kind of dielectric do these capacitors have?

 

[restorer-john]

Sorry, I want to understand the sound quality of your RIAA preamplifier. Therefore, I ask about the quality of the radio components that you used. Burgundy capacitors are not Chinese noname? What kind of dielectric do these capacitors have?

 

[Michael Fidler]

View attachment 443296

LOL - all I can say is see the measurements in the first post! Zero failures in the field related to these parts for almost 3 years of production.