Review and Measurements of Schiit Mani Phono Stage

[psemeraro]

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.

Ryobi 18v 4Ah tool battery works great. And no, I don't have a laboratory so I can't measure what I'm hearing but there is to my perception a subtle difference. I use the Mani at lowest gain setting only. What we know is there is a lot of current available from a tool battery like this and likely less noise inside the Mani without the diodes constantly switching.

A test that might be useful beyond the usual noise, response and distortion would be a null test. Two matching Manis that null to 70dB or more (that was Bob Carver's number that he considered inaudible) then power one via battery and null test again.

 

[Stephen Bayley]

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.

Hi P_M,

I like the battery option!

I found that I still had a regulated 12v out from the LM7812 regulator, and I think that the very low current draw of the Mani circuit doesn't challenge the regulator with respect to the close-to-minimum input voltage.

Enjoy

 

[Tom Ace]

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.

The capacitor at the input to the voltage regulator (C1 in the schematic posted by Stephen Bayley) charges to the peak of the rectified waveform, a higher value than the RMS AC voltage of the wall wart. I measured 24.7 VDC across C1 in my Mani, using the wall wart that came with it.

 

[P_M]

Thanks for doing the measurement, that would be about the expected voltage from a bridge rectifier with 16-17vac input.
But would be a different story when the input is dc itself. Would you mind measuring what you get on the capacitor when you input say 18VDC to he mani ?
btw the mani draws a good 50ma current, so those 9v batteries do run down in a couple of sessions and have to be recharged often. I am going to change them out to a Li-on batteries soon.

 

[Tom Ace]

But would be a different story when the input is dc itself. Would you mind measuring what you get on the capacitor when you input say 18VDC to he mani ?
btw the mani draws a good 50ma current, so those 9v batteries do run down in a couple of sessions and have to be recharged often. I am going to change them out to a Li-on batteries soon.

I measured 16.1VDC across C1 when using two 9V batteries (which, together, measured 17.6VDC when putting out the 50mA that the Mani draws).

I don't hear hum from my Mani at any volume level I ever use so I don't feel a need to power it with DC rather than the AC wall wart. About that wall wart: the label says 16VAC output but that's a nominal figure. I measured 19.4VAC when it's driving the Mani and 15.3VAC when it's putting out its rated 500mA into resistors. The Mani uses about 0.9W of power and the wall wart wastes about 4W as heat (whether it's connected to a Mani or not).

C1 is rated at 25V which I don't think is enough. As I mentioned, I measured 24.7VDC across C1 when using the wall wart Schiit sent me. That's the DC component of the voltage across C1 and there's ripple superimposed on that. Schiit is probably getting away with it--they would hear about it if Manis were blowing up caps in the field--but I would've used a part with a higher voltage rating.

 

[P_M]

Thanks. The cap rating is too close. It may not blow but surely impact performance as it ages.
You wont hear hum but subpar psu filtering and noise will increase noise floor and cause unwanted distortion products that reduces the dynamic range and distortion performance.
If you have a spectrum analyzer (I use pc software and sound card) you might be able to appreciate the difference in the spectrum with ac v/s dc supply to this unit.

 

[Stonecold]

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
View attachment 47815

After Change
View attachment 47816

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.

Stephen. Thanks so much for taking the time to investigate, research and test this, and for posting the results.

I have a Mani paired with a low output Ortofon Quintet Bronze. After experiencing some muddying of the soundstage compared with a MM cart I stumbled upon your post. I have purchased an iFi Power X 15v dc 1.5a supply (£99) and the soundstage has really opened up, with the drums much punchier in the attack, the cymbals shimmer more and have far longer decay, and the vocals and guitars sound separated and more defined, detailed and airy. It’s now back to being the Mani that impressed me so much and I can’t fault it.

 

[Bob from Florida]

I used a Mani for awhile in my system which motivated me to read this thread. As far as I can tell Amir did not test the unit with gain 1 set to low. It would be interesting to see the results of testing in that variation. Set up from the manual is below.
—————————————————
There are no controls on the front, just a LED. When the light is on, it’s on. Flip Mani over and you’ll see a bunch of switches.
1 Gain Switches. These have been set in
Gain 1 = L, and Gain 2 = H, which offers 42dB of gain for most moving magnet (MM) cartridges. Other gain modes include:
Gain 1 and Gain 2 both L: 30dB of gain Gain 1 = H, Gain 2 = L: 48dB of gain Gain 1 and Gain 2 both H: 59dB of gain
2 Load Switches: Use 47 for moving coil (MC), or 47K for MM cartridges. Unknown cartridge? Try 47 first. If your sound fades to almost nothing, set it back to 47K.
If the sound is distorted, one or more of the gain stages is overloading. Switch them to “L” until the distortion goes away. Set both switches in the same position (L, H, or 47, 47K.)
——————————————————
My testing - listening tests with different cartridges - repeatedly would result in audible distortion any time gain 1 = H. This was the case with higher output MM and MC - through the appropriate step up transformer - most especially with wider dynamic range recordings. The power supply is deceptive at 16 VAC - thinking Schiit is taking advantage of the easy way to get plus and minus rails - until you find out otherwise. With the low plus and minus 5 volt supplies headroom becomes a problem before uncorrected RIAA. Keeping gain 1 = L helps here with more headroom prior to the RIAA correction. Accepting the lower gain - 42 db which is not really all that low in the MM world - which will help to keep you out of overload territory resulting in a better listening experience. Turn your preamp up to make up the difference in levels when comparing to typical digital output - just don’t forget to turn it back down when switching back to other sources. Given the asking price - not a bad deal if you work within its limitations, but you can do better if your budget allows.

 

[Stephen Bayley]

Hi Stonecold, glad you enjoyed the lift in performance. I really did as well once I understood what the issue was. Its the sense of adventure that keeps us going in this hobby of ours.

To Bob from Florida, I agree that I was surprised a bit about the +/- 5 volt rails, considering that some designs use +/- 15 or higher. The Hana ML moving coil cartridge I'm using is low output so I have never experienced issues with highly modulated content.

All up a great phono stage for the money, having looked closely at the design, via the components on the board and the approach to overall layout and design principles, (excuse power supply layout) this is one very well designed unit.

 

[Stephen Bayley]

I have recently moved on to a iFi iPhono2 (in Australia a X6 lift in price). I am enjoying this new phono stage a lot. My modified Mani is with my youngest son and his new Project Carbon Debut2 turntable. In true enthusiast fashion we pass our passions on to others and watch them enjoy.

 

[Bob from Florida]

I have recently moved on to a iFi iPhono2 (in Australia a X6 lift in price). I am enjoying this new phono stage a lot. My modified Mani is with my youngest son and his new Project Carbon Debut2 turntable. In true enthusiast fashion we pass our passions on to others and watch them enjoy.

My Mani is with one of my Brothers now. I had replaced it with a Musical Surroundings Phonomena 2+ which I used with various cartridges with good success. However, since I bought a Luxman 507ii integrated - simplifying from all separates - I find the built in phono stage in the Luxman to be quite satisfying. There is no adjustability - 36 db gain MM with 47K load or 56 db MC with 100 ohm load - so you pick a cartridge that mates well. Plenty of gain in the line section
to make up for overall gain if needed. Without easy adjustability - like on the Phonomena - I find myself simply listening to the music more rather than tweaking gain or load. More relaxing and enjoyable if that makes sense.

 

[Porter]

Couldn't you have simply turned down the gain of the Mani to achieve the same result? There is a 30dB setting available. I'm interested to know if it might have solved your issue without any other changes.

I ran one more experiment tonight. My hypothesis is this: the Mani reduces dynamic range only if it receives a signal that is sufficiently loud, the evidence of this being the loss of dynamic range on "Livin' Different" (the title of the dubstep track that is causing problems with the Mani) while maintaining full dynamic range with the quieter classic rock LPs.

So, tonight I put a Schiit SYS in the signal path, after the SUT but before the Mani, and used it to reduce the strength of the signal to the Mani. I ripped a sample of "Livin' Different" and got this:
///////
There we go! Finally!

Here is what we can learn from this: a 0.4 mv MC Cartridge with a 10:1 SUT (which is 3.6 to 4mv I believe) will overload the Mani set to 42db gain with loud records.
The Ortofon 2M Red and Blue is 5.5 mv.
Grado Prestige is 5mv.
Nagaoka MP-110 is 5mv.
The 42db setting on the Mani is supposed to be the correct setting for these cartridges....

 

[ClosDeLaRoche]

Couldn't you have simply turned down the gain of the Mani to achieve the same result? There is a 30dB setting available. I'm interested to know if it might have solved your issue without any other changes.

Sure, but then your amp will be receiving a really weak signal.

Best to buy a different phono stage that can handle 40db gain from MM without clipping.

Anyway, I sold all of my vinyl a long time ago. Can't beat digital these days IMO, I love Bandcamp.

 

[sofrep811]

Owned a Mani and didn't really buy into the burn in and lost patience. This was when they first came out. As usual with Schiit it sold quick with a minor loss. Yesterday iFI Phono Zen arrived and wow. That preamp kicks it right now out of the box. Very impressed so far. I think it be is the same type of amp as the Mani as well but sounds much better on my Rega

 

[Klankbeeld]

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
View attachment 47815

After Change
View attachment 47816

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.

Thnx for this explanation. After reading this I replaced the power supply with a SBooster 15v DC PSU and works fine. Still have to do some comparisons between the PSU's. I have to say, I bought the Mani second hand with an audio grade AC PSU. I think that is already a bit better than the standard wall socket PSU. Using a Quintet Blue cart by the way which will be replaced by a Nagaoka MP-200 in the near future.

 

[Klankbeeld]

Thnx for this explanation. After reading this I replaced the power supply with a SBooster 15v DC PSU and works fine. Still have to do some comparisons between the PSU's. I have to say, I bought the Mani second hand with an audio grade AC PSU. I think that is already a bit better than the standard wall socket PSU. Using a Quintet Blue cart by the way which will be replaced by a Nagaoka MP-200 in the near future.

Did some comparison. The 15V DC SBooster (old model) is definitely an upgrade to hte Swagman Labs 16V AC PSU. No measurements, but the two of us notice a more relaxed sound, more separation. I might modify the Mani by bypassing the rectifier just to be sure it does not interfere anymore as it will be obsolete after changing to a DC PSU. I will order a new 18V SBooster coming week because I use the old 15V Sbooster with some synth modules. The DC voltage after the rectifier will be around 21V when using a 16V AC PSU. So I think 18V DC is the best option, because a step higher voltage is the 24V DC model.