SMSL SP400 Review (headphone amp)

[gvl]

Acrylic it is. Doesn't change the fact it impairs heat dissipation but if there's aluminum plate under it it's better than I thought.

 

[Roland68]

Acrylic it is. Doesn't change the fact it impairs heat dissipation but if there's aluminum plate under it it's better than I thought.

But far less than you think. The entire housing has no direct contact with the heat-generating parts. Since the housing is completely closed and the heat exchange inside and outside takes place via air, the difference to a pure aluminum plate would be less than one degree.

 

[gvl]

You might be right, but the sides are fairly warm to the touch so even via air they get heat up pretty well. The top and bottom parts have area much larger than the sides and there is no surface to air heat exchange there due to acrylic, so I would think they could help more than just a bit if the metal was exposed. But it's all speculation of course. At 40C box temperature I don't think it's it's too bad anyway,

 

[gvl]

Whatever magic I'm hearing, if it's not my imagination, must be coming from the amp. I spent some time switching inputs between the M400 and the Topping D10s and could not detect any meaningful differences, at times it seemed the former was a bit smoother on voices but not enough to be conclusive. It does feel the analog volume control on the amp works better than the digital I experienced, I always felt that digital control robs you of some details below -25db volume level which was the level I often had to listen ar, things start to sound grayish. Not here, even at lower comfortable background music levels everything sounds pretty crisp and detailed.

 

[fabflix]

Does anybody use this as a preamp only? I'm interested in this unit to replace my Topping PRE90 due to the low input impedance on the later.

 

[gvl]

I tried it briefly and it was fine. No RCA outs though. There's also the Gustsrd P26, decent XLR performance there.

 

[nobody]

Does anybody use this as a preamp only? I'm interested in this unit to replace my Topping PRE90 due to the low input impedance on the later.

I had Topping A90 and still have SP400. Both primary used as preamp. The SP400 is definitely more transparent. A90 has fantastic bass, but is little bit worse in top octaves details. In terms of sound A90 should be same as PRE90. But honestly, if I had not the oportunity to compare them directly, I would live happily with any of them. PRE90 is in terms of functions better preamp than SP400 - XLR and cinch out, ability to match volume of inputs, extender. SP400 can obviously serve as headphone amp and you don't need another device.

 

[MSomi]

My RME can output 13dBu (3.5Vrms) and 19dBu (7Vrms)

7Vrms won't / can't cause the SP400 input to clip?

What is the input voltage limit for SP400?

I asked Shenzhen Audio a while ago, I can't remember exactly but it is around 10 volts. I also have the RME ADI-2 DAC and use it on 19 dBu all the time.

 

[waver]

What is the line output impedance of sp400? Is it same as headphone output impedance on the front?

 

[McCluskey]

SMSL SP400 - fully balanced (4x THX 888 module), Pre-out, remote control, relay volume control, headphone out
SMSL SH-9 - unbalanced (2x THX 888 module) remote control, relay volume control NO Pre-out
Topping A90 - fully balanced, pre-out, potentiometer volume conrol, NO remote control, headphone out
Topping Pre90 - fully balanced, pre-out, remote control, relay volume control, NO headphone out
Topping L30 - unbalanced, Pre-out, NO remote control, potentiometer volume conrol, headphone out

In my eyes the SP400 is most complete package. For same price as Pre90 you get headphone out, but no option to expand inputs and volume preset for inputs.

I’ve had both the A90 and the SP400. Clarity and soundstage on the SP400 are both superior. I found the A90 soft on top, closed and bottom heavy. Its crazy but the DCA Stealth and the SP400 fed by an ADI-2 Pro are great.

 

[McCluskey]

So just to clarify the A90 has more power at 33 and 50 ohms and had a better Sinad.
Are there any standout measurement to point out where the SP400 actually outperforms the A90 in a significant way?

Have them both at least until I return the A90. Clarity and sound stage better on the SP400

 

[McCluskey]

if you're listening on a pair of headphones at 99 and wishing it were louder can you raise your hand and list the pair of HPs, the dac and whether you're bal or unbal input and bal or unbal output? (SE out gain is lower in one case)

I’m running +19db out on my Adi-2 Pro..I think that equates To 7.7v. Mid gain, lots of volume headroom.

 

[McCluskey]

My only concern is that RME Adi uses AKM 4490 chip while Monolith uses the more advanced AKM 4493 chip. Can you hear a difference in these dac by having two different generation of chips?

The simple answer is no..I have three generations of ADI-2 Pros all with different AKM chips. No Audible difference between them! Purely esoteric measurements

 

[gvl]

I have a grin on my face every time I listen to SP400 on my HD6XXs, so much clarity and top/bottom end extension, just a delight.

 

[McCluskey]

I’ve got mine going now..love it. DCA Stealth. Holographic.

 

[DawgSlaya]

Quick question: with the SP400, bal in/bal out, on low gain and 99 volume, what's the overall gain?
Is it at +0 unity gain?
Or +6.5db (+6.5db low gain +0 bypassing the relay volume control)
Or +6db (+6.5db low gain -0.5db assuming 100 is no relay, but the last step is locked)

 

[Music1969]

I just wish they would qualify this in their specs, post an input voltage, especially if no product or DAC they manufacture has that kind of output.

@SMSL-Mandy @SMSL_Liu can you guys please confirm max input voltage for SP400?

Someone mentioned 10Vrms input voltage - is that correct?

 

[McCluskey]

I run min my ADI-2 Pro output at +19 db. It’s about 7 volts. I have plenty of headroom on medium and high gain.

 

[Music1969]

I run min my ADI-2 Pro output at +19 db. It’s about 7 volts. I have plenty of headroom on medium and high gain.

Yep but just curious at what input voltage the SP400 starts clipping.

 

[Music1969]

SMSL confirmed 10Vrms max.

So ADI-2's 7Vrms output, is nicely inside that to give SP400 good power output and keep low distortion.