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Review and Measurements of Schiit Mani Phono Stage

audiopile

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Clos -I'm not sure the SYS is going to be transparent other than reducing output -while the input impedance of a SUT is critical -unfortunately in somewhat the opposite way (capacitance) so is the output into a MM input from a SUT ? Despite dealing with it for 50+ years -I still get a headache everytime I try to reason my way thru anything to do with the goofy way we EQ audio off of records. I remain puzzled by the many positive reviews of the Mani : 1.) I've never run a LOMC thru mine . Is the MC section amazingly better than the MM ? 2.) I bought the multi-voltage "octopus" power supply from Schiit and that's all I've used with the Mani. Is it possible that the cheaper stock supply that usually comes with the Mani sounds better ?
 
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The following spectrum is the Mani left channel RCA output (no input) with the Mani set to the low output moving coil gain setting (Gain stages 1 and 2 both at Hi).

In this high gain mode there is power supply rectification harmonics evident at the RCA outputs, with the Left channel being most impacted and the Right channel some 6 db lower.

I have identified the cause of the harmonics, this being the physical layout of the Bridge Rectifier and the main filter capacitor C1. Capacitor C1 is mounted horizontal on the circuit board and lays directly over the Gain Stage 1 OpAmp and associated components. While C1 is on the top face of the circuit board the input OpAmps are directly below on the other side of the circuit board. The high current transients resulting from the rectification of the 16VAC power supply input passing through C1 filter capacitor generates an EMI signal which is being induced into the Gain Stage 1 OpAmps and/or associated components. This issue is not a power supply design issue but one of physical layout dictated by the small size of the Mani case. I am in Australia so the power supply rectification harmonics are at 100Hz intervals.

1568952645577.png


I have modified my Mani such that the power supply harmonics are now absent as shown in the spectrum plot below, also the 50Hz power supply hum component related to the 16VAC input power is also reduced.

1568953411082.png


If anyone is interested I can supply further details on the approach I took to resolve this issue. I undertook this measurement after ordering a Hana ML moving coil cartridge and wondering what the Mani Hi Gain noise performance looked like. I think it sounds superior now, the best part is I can measure the difference!
 

steve-z

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Clos -I'm not sure the SYS is going to be transparent other than reducing output -while the input impedance of a SUT is critical -unfortunately in somewhat the opposite way (capacitance) so is the output into a MM input from a SUT ? Despite dealing with it for 50+ years -I still get a headache everytime I try to reason my way thru anything to do with the goofy way we EQ audio off of records. I remain puzzled by the many positive reviews of the Mani : 1.) I've never run a LOMC thru mine . Is the MC section amazingly better than the MM ? 2.) I bought the multi-voltage "octopus" power supply from Schiit and that's all I've used with the Mani. Is it possible that the cheaper stock supply that usually comes with the Mani sounds better ?
I ran a Schiit Mani for several months in conjunction with a Nagaoka MP110 which I’d seen recommended as a good combination, I thought the combination was good if rather ordinary and I decided to try a LOMC, an Audio Technica ATF7, unfortunately in conjunction with the Mani the sound quality was pretty abysmal, dull and lifeless, checking the Mani specs found the input impedance on MC is a non adjustable 47ohms, AT like most manufacturers of MC cartridges specify the correct load for their cartridges is 100ohms or above, because of that the Mani was sold on, because of scarcity value at the time, at a profit, replacing it with the Cambridge Audio CP2, the predecessor of the Duo, in conjunction with the ATF7 the performance is superb. Sorry for the slightly long winded answer but in my estimation the Mani is not up to scratch with MC cartridges.
 

Voxy

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The following spectrum is the Mani left channel RCA output (no input) with the Mani set to the low output moving coil gain setting (Gain stages 1 and 2 both at Hi).

In this high gain mode there is power supply rectification harmonics evident at the RCA outputs, with the Left channel being most impacted and the Right channel some 6 db lower.

I have identified the cause of the harmonics, this being the physical layout of the Bridge Rectifier and the main filter capacitor C1. Capacitor C1 is mounted horizontal on the circuit board and lays directly over the Gain Stage 1 OpAmp and associated components. While C1 is on the top face of the circuit board the input OpAmps are directly below on the other side of the circuit board. The high current transients resulting from the rectification of the 16VAC power supply input passing through C1 filter capacitor generates an EMI signal which is being induced into the Gain Stage 1 OpAmps and/or associated components. This issue is not a power supply design issue but one of physical layout dictated by the small size of the Mani case. I am in Australia so the power supply rectification harmonics are at 100Hz intervals.

View attachment 33882

I have modified my Mani such that the power supply harmonics are now absent as shown in the spectrum plot below, also the 50Hz power supply hum component related to the 16VAC input power is also reduced.

View attachment 33883

If anyone is interested I can supply further details on the approach I took to resolve this issue. I undertook this measurement after ordering a Hana ML moving coil cartridge and wondering what the Mani Hi Gain noise performance looked like. I think it sounds superior now, the best part is I can measure the difference!

Would be interested what modification you had taken to reduce the power supply harmonics. Pls share since I ordered one to test out. :)
 
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Hi.

Below is a simplified diagram of the Mani power supply based on my tracing of the circuit. The issue I discussed above is to do with the 16VAC rectification current surges passing through the bridge rectifier BR1 and the associated filter capacitor C1.

The steps I took at the time were:
  • I raised the rear of C1 as high off the circuit board as I could will still allowing the Mani cover to fit; the harmonics reduced by around 6db. (the greater the distance from C1 to the OpAmps on the opposite side of the circuit board the lower the impact of the EMI).
  • I replaced C1 with a physically smaller capacitor mounted as high as the Mani cover would allow; the harmonics were reduced by a further 3db, but still present.
  • I elected to remove the bridge rectifier entirely from the Mani and use a DC power pack; therefore transferring the task of AC rectification to an external power pack, thereby delivering a filtered DC supply to the Mani. I am using a iPower 15VDC power pack to supply the Mani. The outcome is the clean spectrum shown in my first post.
Before Change
1580267084093.png


After Change
1580267326447.png


After I had removed the bridge rectifier and added links I realised that I had performed more changes than is really required given the traditional bridge rectifier input design used in the Mani. It is technically feasible to feed the Mani directly from a DC power pack without any circuit changes. (see the article in the following link). This would allow an iPower 15VDC to directly power the Mani without any internal changes. The iPower 15VDC even has the correct power connector for the Mani allowing a direct swap. Of course read the article referenced here and proceed at your own risk, however if I had thought harder about it at the time (rather than racing for the soldering iron) I would have taken that approach.

link to article: https://www.quora.com/What-happens-when-a-dc-current-passed-through-a-bridge-rectifier

The overall Mani power supply design is quite elaborate with the actual external power supply having no real effect on the performance of the amplifier. There are three level of power supply regulation, the main 12V regulator to establish a default 12VDC supply to feed the Voltage Converter which establishes balanced +/- supplies then individual voltage regulators for the Stage 1 OpAmps and Stage 2 OpAmps. I am quite impressed with the attention to detail. I have read of others who have purchased high current AC supplies to power the Mani, I cant see how, given the overall power supply design, how that could possibly make any difference. The input supply is completely isolated from the amplifier circuits by the Voltage Converter. They don't even share the same earth circuit.
 

audiopile

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Stephen - thank you for the info and analysis . I've still got a Mani that I haven't sold on -and a couple of iFi iphono's -so have iPower supplies -gonna give this a try with a LOMC cart. Perhaps I can be converted to believe in the Mani ?
 

Voxy

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Stephen, thank you for the comprehensive explanation. I had also ordered the iPower upon reading since technically there is should be no issue given the iPower is a 15V 2A adaptor vs the 16 VAC 0.5A step down transformer (correct me if I am wrong). So basically we move the DCDC conversion into iPower instead on the Mani board.

So by feeding clean DC into the DCDC stage, it has eliminated the EMI issues during the rectification with a VAC input. Just curious, if the board had been bigger, would the same issue surface?

Lastly, will there be grounding issues since you are using a DC supply instead....
 
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Stephen - thank you for the info and analysis . I've still got a Mani that I haven't sold on -and a couple of iFi iphono's -so have iPower supplies -gonna give this a try with a LOMC cart. Perhaps I can be converted to believe in the Mani ?

Hi audiopile

I would like to hear your impressions of the iFi Phono compared to the Mani. I have read about the iFi Phono design concepts and like them. I have been thinking about grabbing one to try, your feedback would be most welcome.

I purchased the Mani on a whim when I decided to return to the record format and refurbish my Denon direct drive turntable last August (after many years with SACD). The Mani looked like something I could play with (modify) without any real financial impact (it replaced a 10 year old Cambridge Azur 640P which I didn't like with the new Hana ML moving coil).

So the Mani is a starting point, and I enjoyed the tinkering to clean up its output. Now that the Hana ML is run in I'm wondering what other MC amps may sound like.
 
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Stephen, thank you for the comprehensive explanation. I had also ordered the iPower upon reading since technically there is should be no issue given the iPower is a 15V 2A adaptor vs the 16 VAC 0.5A step down transformer (correct me if I am wrong). So basically we move the DCDC conversion into iPower instead on the Mani board.

So by feeding clean DC into the DCDC stage, it has eliminated the EMI issues during the rectification with a VAC input. Just curious, if the board had been bigger, would the same issue surface?

Lastly, will there be grounding issues since you are using a DC supply instead....


Hi Voxy

You are correct that if the Mani case was larger then the bridge rectifier and power supply capacitor C1 could have been located away from the very sensitive Stage 1 OpAmps.

In the Hi Gain mode for low output Moving Coils the Stage 1 OpAmps have significantly more gain and so are more sensitive to the EMI generated by the current pulses rushing through the Bridge Rectifier and filter capacitor. In the lower gain Moving Magnet setting the issue is nowhere as evident. Schiit could have used an external DC supply for the Mani and the issue would not have existed, however it appears that the 16VAC is the standard external supply they use for all small products.

I have no grounding issues, the Mani analog earth that the output cable use is not connected to the external power supply ground.
 

audiopile

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Neither I or any of the friends I have loaned the Mani to - have tried it with LOMC's -so -gonna try it with a 15V Ifi iPower runnin it and probably a Denon DL-103r before I make up my mind. So far -as a MM preamp-none of us have been impressed. I bought my first iFi iPhono as a very versatile/very portable service instrument. That and a O2 headphone amp n Grado phones and I could substitute for what ever brilliant/strange equipment choices somebody had made. I just want to get their TT/arm/cart workin right- the other stuff is just confusing. I bought a MK-II iFi Iphono because the original was pretty darn impressive -the II is probably a bit quieter -that might be about it. I switch carts a lot -so the versatility of the IPhono is appreciated -especially the ability to change capacitors for classic MM carts. Downside: to my old nun handles -- very slight tendency towards steely highs -this can be a nuthin problem depending on your 'phones/speakers - it is VERY quiet -which is nice and especially appreciated driven into headphone amps/headphones.
 

audiopile

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BTW- on the issue of the challenges of placing power supplies in compact enclosures/actually the reverse: I use a couple of Parasound JC-3 jr.s and a ELAC PPA-2 - in both cases -once you pull the covers -you will notice how much air is inside those cases.
Part of this is probably for issues of consumer convenience /placement and a common "look" to those manufacturers line of products. Afterall -the ongoing fantasy is that you enjoy one component and then buy the matching "stack" to go with it. But the point is that both designers used that air space to move the power supplies a way off from the active phono circuit boards. Both companies produce VERY quiet phono stages - with identical equipment they still don't sound much alike.
 

audiopile

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ReallY? Well here goes : Some of the best meals of my life have been in households that practiced either Halal or Kosher cooking.
But I am a agnostic and neither religion (any) calls me to it's path. Still -food and company are much appreciated. So-I approach audio (for more than 50 years with increasingly decrepit hearing) much the same way - I have friends who are very influenced by the Joe Friday "facts" and others who seem to feel price/exoticism increases their listening pleasure - every once in awhile something sounds good -I really would like to know why and maybe I can find some sort of answer here or elsewhere like HFN&RR that has a long record for testing what they listen to ? But I suspect we may still be possibly looking at the issue of audio quality thru a not terribly clean lens.
 

LTig

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ReallY? Well here goes : Some of the best meals of my life have been in households that practiced either Halal or Kosher cooking.
But I am a agnostic and neither religion (any) calls me to it's path. Still -food and company are much appreciated. So-I approach audio (for more than 50 years with increasingly decrepit hearing) much the same way - I have friends who are very influenced by the Joe Friday "facts" and others who seem to feel price/exoticism increases their listening pleasure - every once in awhile something sounds good -I really would like to know why and maybe I can find some sort of answer here or elsewhere like HFN&RR that has a long record for testing what they listen to ? But I suspect we may still be possibly looking at the issue of audio quality thru a not terribly clean lens.
So no evidence then?
 

Voxy

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Ok hook them up and the Mani is absolute a bargain.... even with the iFi DC 15W wall adaptor.... no EMI no RFI.

Ok I just gonna leave it as it is.
 

P_M

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Hi.

After I had removed the bridge rectifier and added links I realised that I had performed more changes than is really required given the traditional bridge rectifier input design used in the Mani. It is technically feasible to feed the Mani directly from a DC power pack without any circuit changes. ...
...
I am quite impressed with the attention to detail. I have read of others who have purchased high current AC supplies to power the Mani, I cant see how, given the overall power supply design, how that could possibly make any difference. The input supply is completely isolated from the amplifier circuits by the Voltage Converter. They don't even share the same earth circuit.

I use two 9V rechargeable batteries in series. I observed the same improvement in line frequency injection and overall noise floor of the amp. But I have something to add to what you have already said -
I dont remember the exact part# of the 12v regulator but I remember when I had checked its data sheet the min input to the regulator was about 15V. The bridge rectifier will add some voltage drop (2x.7=1.4V) so the reg sees only 15-1.4=13.6V - too low, almost outside or on the edge of its operating boundary. I'd be more comfortable having it operate within its range. I didn't have a 18VDC supply so just wired up two batteries, and there has been no looking back since.
 
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