SMSL SP400 Review (headphone amp)

[foxxx0]

So today my SP400 arrived and there are a few things I noticed (some of which have been mentioned here already) :

1. no way to toggle between pre-out and headphones, both outputs are driven simultaneously all the time
2. In my opinion the volume range is too fine-grained

In order to work around the first one, I have ordered a little Nobsound XLR 3-way Switch thingy, so I can just choose where my M500 DAC output goes, either to the powered studio monitors *or* to the SP400. Fine by me, also gives me the ability to add a third consumer later down the road if needed.

The second one is unfortunately out of my control. I have played a bit with different volume levels and then cycling through the gain settings but the volume control really is a bit cumbersome.
What I would *really* like to see here is a firmware update from SMSL, which basically adds a user-configurable setting in the menu called something like "volume step" or "volume increment". It can default to 1 and it could be configurable from 1 to let's say 20.
This would also solve the "slow" volume change, especially with "volume mode enabled". You could then just set it to 5 or 10 and the volume would increment (or decrement) by that amount.

One of the reasons I went with the SP400 was the resistor ladder output stage to have good channel balance and not having to rely on an analog potentiometer which might degrade over time. Unfortunately the slow volume change is more annoying than anticipated.
I will test it a few more days but I'm already slightly annoyed which is not a good sign.

Are there other R2R headphone amps within the same price range (~570 EUR / ~$650 US) that have comparable performance?
If not, I might give the Topping A90 a try.

My current gear:
- SMSL M500 DAC fed via optical toslink
- Sennheiser HD660S (150 Ohm)
- KRK Rokit RP6 G3 powered studio monitors (XLR <-> M500)
- new: SMSL SP400 HP-AMP (XLR <-> M500)

 

[bgtip]

So today my SP400 arrived and there are a few things I noticed (some of which have been mentioned here already) :

1. no way to toggle between pre-out and headphones, both outputs are driven simultaneously all the time
2. In my opinion the volume range is too fine-grained

In order to work around the first one, I have ordered a little Nobsound XLR 3-way Switch thingy, so I can just choose where my M500 DAC output goes, either to the powered studio monitors *or* to the SP400. Fine by me, also gives me the ability to add a third consumer later down the road if needed.

The second one is unfortunately out of my control. I have played a bit with different volume levels and then cycling through the gain settings but the volume control really is a bit cumbersome.
What I would *really* like to see here is a firmware update from SMSL, which basically adds a user-configurable setting in the menu called something like "volume step" or "volume increment". It can default to 1 and it could be configurable from 1 to let's say 20.
This would also solve the "slow" volume change, especially with "volume mode enabled". You could then just set it to 5 or 10 and the volume would increment (or decrement) by that amount.

One of the reasons I went with the SP400 was the resistor ladder output stage to have good channel balance and not having to rely on an analog potentiometer which might degrade over time. Unfortunately the slow volume change is more annoying than anticipated.
I will test it a few more days but I'm already slightly annoyed which is not a good sign.

Are there other R2R headphone amps within the same price range (~570 EUR / ~$650 US) that have comparable performance?
If not, I might give the Topping A90 a try.

My current gear:
- SMSL M500 DAC fed via optical toslink
- Sennheiser HD660S (150 Ohm)
- KRK Rokit RP6 G3 powered studio monitors (XLR <-> M500)
- new: SMSL SP400 HP-AMP (XLR <-> M500)

The slow volume change is annoying to me too, but most of my music is replaygain compensated in foobar2000, so I don't change volume too often or too much.
My main gripe is about the perceived lack of power with my Goldplanar GL2000, especially on higher listening levels.
How the HD660S sound with SP400? I used to have HD660S, but I didn't have powerful enough amp then. I suppose the bass is fuller with SP400?

 

[jjluke]

So today my SP400 arrived and there are a few things I noticed (some of which have been mentioned here already) :

1. no way to toggle between pre-out and headphones, both outputs are driven simultaneously all the time
2. In my opinion the volume range is too fine-grained

In order to work around the first one, I have ordered a little Nobsound XLR 3-way Switch thingy, so I can just choose where my M500 DAC output goes, either to the powered studio monitors *or* to the SP400. Fine by me, also gives me the ability to add a third consumer later down the road if needed.

The second one is unfortunately out of my control. I have played a bit with different volume levels and then cycling through the gain settings but the volume control really is a bit cumbersome.
What I would *really* like to see here is a firmware update from SMSL, which basically adds a user-configurable setting in the menu called something like "volume step" or "volume increment". It can default to 1 and it could be configurable from 1 to let's say 20.
This would also solve the "slow" volume change, especially with "volume mode enabled". You could then just set it to 5 or 10 and the volume would increment (or decrement) by that amount.

One of the reasons I went with the SP400 was the resistor ladder output stage to have good channel balance and not having to rely on an analog potentiometer which might degrade over time. Unfortunately the slow volume change is more annoying than anticipated.
I will test it a few more days but I'm already slightly annoyed which is not a good sign.

Are there other R2R headphone amps within the same price range (~570 EUR / ~$650 US) that have comparable performance?
If not, I might give the Topping A90 a try.

My current gear:
- SMSL M500 DAC fed via optical toslink
- Sennheiser HD660S (150 Ohm)
- KRK Rokit RP6 G3 powered studio monitors (XLR <-> M500)
- new: SMSL SP400 HP-AMP (XLR <-> M500)

I thouth about using Nobsound and I think it is a really nice idea, to have it in the chain to just toggle either the head-amp or speakers.
About the volume, I would suggest to play with the Volume Mode in the menu and see if either of the 2 modes, makes a difference to you.
I keep Volume mode enabled.

About volume control, I personaly use the 3 gear approach, as with my brompton bike High/Medium/Low
The SP400 gains are fairly close to each other.

Using this to my advantage, I have mastered to configure the SP400 using the following steps:
-Switch gain to Medium
-Set the volume using the wheel, while playing a song you listen to often, using the headphone you use the most. (I keep my volume to 50).
-Once you are set, toggle between (Low/Medium/High) to low or raise the volume slightly to suit your tracks.

With time, I noticed that 50 is my volume, and just use the remote FN button, to toggle the gain I want.

 

[foxxx0]

The slow volume change is annoying to me too, but most of my music is replaygain compensated in foobar2000, so I don't change volume too often or too much.
My main gripe is about the perceived lack of power with my Goldplanar GL2000, especially on higher listening levels.
How the HD660S sound with SP400? I used to have HD660S, but I didn't have powerful enough amp then. I suppose the bass is fuller with SP400?

It took quite some time to finally decide on the HD660S for me, I was deciding between multiple options and the HD650 was also in the ring. Finally I chose the HD660S in the hopes of similar stellar performance like the HD650 albeit at half the impedance and thus hopefully being easier to drive.
While I had not reached the maximum volume on my M500 headphone output with the HD660S yet (even with a -7dB pregain EQ), I had already prepared a nice little spot on my desk for a headphone amp.
Also the headphone output of the M500 is not the greatest SINAD/SNR wise, especially when at 50mV output.
Needless to say, I was going to purchase a headphone amp at some point anyways and now I pulled the trigger on the SP400.

At lower/moderate volume levels the HD660S have a bit more brilliance and clarity on the SP400 compared to the hp-out of the M500.
With higher volume levels the lower frequencies have a bit more energy than on the M500.
I'm quite impressed and please with the audio performance and fidelity of the SP400, the usability with respect to changing the volume is quite annoying though.

I thouth about using Nobsound and I think it is a really nice idea, to have it in the chain to just toggle either the head-amp or speakers.
About the volume, I would suggest to play with the Volume Mode in the menu and see if either of the 2 modes, makes a difference to you.
I keep Volume mode enabled.

About volume control, I personaly use the 3 gear approach, as with my brompton bike High/Medium/Low
The SP400 gains are fairly close to each other.

Using this to my advantage, I have mastered to configure the SP400 using the following steps:
-Switch gain to Medium
-Set the volume using the wheel, while playing a song you listen to often, using the headphone you use the most. (I keep my volume to 50).
-Once you are set, toggle between (Low/Medium/High) to low or raise the volume slightly to suit your tracks.

With time, I noticed that 50 is my volume, and just use the remote FN button, to toggle the gain I want.

Thanks for sharing your SP400 experience, will give that a try and fiddle around with it over the weekend.

The one thing that is nice when having two "current Gen" SMSL devices: I can control them both with one remote, the one that already came with my M500. Just press the B button to then control the SP400, press C and control the M500.

 

[Standingstones]

I received the SMSL M400 last week. I wanted to see how things went with my new DAC before I consider buying a SMSL headphone amp. I wanted to read how others felt about SMSL headphone amps.

 

[foxxx0]

Thanks to Amazon Prime shipping the Nobsound XLR switch thingy already arrived today and I had enough spare XLR patch cables (although slightly varying lengths) lying around to connect everything together.

I have to say this improved usability already quite substantially.

Thanks to the M500 at max volume (40) outputting 6.8V over XLR (according to amir's review) I seem to have plenty of headroom on the SP400. I've also tried the M500 at volume 34 which is supposed to give nominal ~4V over XLR and that takes out a noticeable amount of power so that I have to crank it a bit higher.
With a -7dB pregain EQ applied I have yet to cross the 60 volume level at high gain, stayed about half an hour at volume 55 but then turned it down again. Long time enjoyable volume seems to be around 40 at high gain for me and as suggested by @jjluke switching between the gain settings makes for quite nice and quick gain adjustment.

Over the last couple of hours I have been playing around with varying volumes and gain settings in the SP400 and I'm slowly getting the hang of it, turns out I don't adjust the volume that often either.
(I still wish the volume step size would be adjustable though, increments/decrements of 5 could be ideal, at least for my gear)

While listening I have put together some orders at multiple shops:
- 8 pairs (different vendors) of Sennheiser's proprietary 2-pin plug for HD6xx/HD580 headphones at aliexpress
- some Neutrik 4pin XLR connectors (male)
- some Neutrik 3pin XLR connectors (female + male)
- various cables with 20, 22 and 24 AWG
- some paracord in 2 sizes, in black and orange with 30m of each

Looks like I'll be making custom length XLR patch cables for the M500<->Nobsound<->SP400 and a custom braided paracord balanced cable for the HD660S when all parts have arrived.

 

[Inkey31]

It's fully balanced and has resistor volume. So no 399 won't happen..

Do you know if 2 different amps can have the same output wattage but have different Current and Voltage?

 

[jruser]

Is it correct that this take XLR input, converts it unbalanced, runs it through volume control, and then converts it back to balanced?

 

[MadMan]

Is it correct that this take XLR input, converts it unbalanced, runs it through volume control, and then converts it back to balanced?

No, because line level balanced and headphone 'balanced' (which should really be called 'dual mono' at best) are not the same thing. There's no 'conversion back to balanced' for so-called balanced headphone outputs.

 

[m8o]

No, because line level balanced and headphone 'balanced' (which should really be called 'dual mono' at best) are not the same thing. There's no 'conversion back to balanced' for so-called balanced headphone outputs.

I like to think this too. But do we know this for sure?

Edit: okay, found this... Best would be to see the schematic. But I think we see what we want to see. I'm apt to believe this shows a (+) & (-) set of devices for both L & R here.

 

[jruser]

I like to think this too. But do we know this for sure?

Edit: okay, found this... Best would be to see the schematic. But I think we see what we want to see. I'm apt to believe this shows a (+) & (-) set of devices for both L & R here.
View attachment 126138

Wouldn't it need 16+ relays for 256 levels for 4 channels (+L,-L,+R,-R)? This only has two more relays than the SH-9, which I understand the extra 2 relays are for the preamp function.

 

[m8o]

Wouldn't it need 16+ relays for 256 levels for 4 channels (+L,-L,+R,-R)? This only has two more relays than the SH-9, which I understand the extra 2 relays are for the preamp function.

Could be. I'll fall back to, best would be to see a schematic.

 

[MadMan]

I like to think this too. But do we know this for sure?

Edit: okay, found this... Best would be to see the schematic. But I think we see what we want to see. I'm apt to believe this shows a (+) & (-) set of devices for both L & R here.
View attachment 126138

What I wrote has nothing to do with the topology of a specific amp. Balanced signal transmission is +/-/neutral (reference) or more accurately: signal +/inverted signal -/neutral (reference). Headphones are +/- only....'balanced' is a misuse of the term for headphones, and it's clear audio enthusiasts don't understand this because the question about 'true balanced headphone connections' comes up alllll the time. Tyll Herstens said one of his regrets from the early days of Headamp was calling dual 3-pin XLR outputs 'balanced', when each 3-pin XLR only used two wires +/- with one XLR socket for each channel (because no one used 4-pin XLR at the time, which simply combines two channels of +/- (4 wires) into one connector). It should have been called 'dual mono' at most. This misnaming conflated the physical connector with the signal it carried and ended up causing confusion that continues to this day.

 

[Aloen]

My first stack, M400 and SP400. Zero complaints so far. Beautiful sound, can't wait to get my LCD 2's!

https://imgur.com/a/32QrvhL

 

[Veri]

Looks great, man! Beautiful picture, too

 

[SimoF]

New stack arrived for me too.
Superb audio quality imo. Well done SMSL

 

[Panoramious]

I am considerin it to go between my adi 2 dac fs and my bryston. Main reason is for connnecting my avrs preouts on its analogue se inputs and the dac on the balanced xlrs.

Questions:

1) Will there be any gain on my headphones rig too? Perhaps on dynamics, slam and soundstage? I own a set of focal clears.

2) As a preamp, what am i to expect comparing to the rme hooked up straight in to bryston?

3) i was cosidering the topping a90. Which do you guys think is Best suited for the task? The bad with the topping series is that you cant combine preamp functionality, headphones amp and remote control but if there is going to be a serious benefit from a topping device i may consider accepting some inconvenience.
Thanks in advance

 

[Red@]

View attachment 105722
I was hoping you can verify the power output on the SP400 because there is no way it is outputting 12W at 16ohm on balance. SP400 on low gain can go higher than THX889 low gain but on high gain it’s way weaker than THX889 high gain. I doubt the SP400 can even output 6W at 16ohm on balance. I am testing on an 16ohm Ether 2.

Hello,
Can you please point me to where I can find any reference to thx 889 ?
I don't think it exists.

 

[Veri]

Hello,
Can you please point me to where I can find any reference to thx 889 ?
I don't think it exists.

Drop is 789, monoprice is 887. 889 is a typo I'm sure.

 

[Roland68]

Hallo,
Können Sie mir bitte einen Hinweis zu thx 889 geben?
Ich glaube nicht, dass es existiert.

SMSL SP400 = THX AAA 888