SMSL SP400 Review (headphone amp)

[rocksteady]

600ohms headphones (beyerdynamic dt 880 600ohms) some magnetic planar headphones. More power means headroom,and its always a good thing. Sometimes you need a couple of watts at relatively low impedence.

Exactly. I mostly use vintage High impedance Hedaphones and I don’t find these Specs particularly impressive. Incidentally, Armin’s published figures at 300 Ohms are much lower than SMSL’s own. Especially so on SE mode. 173 mW don’t seem quite sufficient to me. Am I missing something here?

 

[rocksteady]

He gets corrected in the comments and that double the power only equates to +3db and that's exactly what he was seeing.

Double the power equates to +6dB, not +3dB…

 

[odyo]

Exactly. I mostly use vintage High impedance Hedaphones and I don’t find these Specs particularly impressive. Incidentally, Armin’s published figures at 300 Ohms are much lower than SMSL’s own. Especially so on SE mode. 173 mW don’t seem quite sufficient to me. Am I missing something here?

SE performance is normal. It's a balanced amp. BAL 700mw may not be impressive at 300 ohm but it's fair. This amp is impressive when it comes to low impedance loads. Amir didn't measured it but SMSL claim 12W at 16 ohm, 6W at 32 ohm. Very impressive for low impedance, current hungry planars. 300 ohm performance is same as my Zen Can which was something like $149.

 

[Roland68]

Exactly. I mostly use vintage High impedance Hedaphones and I don’t find these Specs particularly impressive. Incidentally, Armin’s published figures at 300 Ohms are much lower than SMSL’s own. Especially so on SE mode. 173 mW don’t seem quite sufficient to me. Am I missing something here?

Most headphone amplifiers are tuned to the low-impedance headphones that are common in the hi-fi sector and only work at the output stages with +/- 15 volts (usually +/- 12-18 volts).
Take a look at the data from a headphone amplifier that originally comes from the studio area and works with +/- 30 volts.

https://www.audiosciencereview.com/...-measurements-of-lake-people-g109-s-amp.7227/

SE Power @300 Ohm 350mW, but only 1,1 watts @33 Ohm

 

[Snoopy]

I got the SP400 for a couple days. So far I really like it. Running a -7db headroom in roon + doing some EQing for my Aeon 2 noire headphones.

Low, mid, or high gain doesn't make much of a difference so I'm running the amp in mid gain and Im between 54-65 on the volume wheel.

Plenty of headroom left for me. I will probably never own headphones that this amp won't be able to power well enough.


I'm using a SMSL D300 that outputs 4 volt balanced.

 

[mrjayviper]

Anyone paired this with a smsl d1se? Thoughts? Or maybe something cheaper but of equal/similar performance? Thank you

 

[Roland68]

Anyone paired this with a smsl d1se? Thoughts? Or maybe something cheaper but of equal/similar performance? Thank you

I don't think you will find a better price/performance ratio with balanced output than the SMSL DO100 right now.
https://www.audiosciencereview.com/forum/index.php?threads/smsl-do100-review-stereo-dac.34198/

 

[Noob]

I don't think you will find a better price/performance ratio with balanced output than the SMSL DO100 right now.
https://www.audiosciencereview.com/forum/index.php?threads/smsl-do100-review-stereo-dac.34198/

I think the Topping D10 balanced is the best price/performance. It's only $140, and performs very similarly to the DO100. So that's a big cost saving. It does only take usb input, but the trade is that is also works as a digital converter/bridge with coax and toslink output.

 

[Roland68]

I think the Topping D10 balanced is the best price/performance. It's only $140, and performs very similarly to the DO100. So that's a big cost saving. It does only take usb input, but the trade is that is also works as a digital converter/bridge with coax and toslink output.

Exactly there I have a different opinion, but everyone should have their own.

Power supply for the D10 Balanced via USB, a no-go for me.
Balanced connection via 6.35mm jack, significantly poorer contact quality compared to XLR, plus only a few available cables to XLR.
Only balanced connection. According to Topping, RCA can only be connected with an expensive real electronic RCA -> Balanced Module.
Only connection via USB possible, all other devices that are connected via SPDIF, e.g. TV, streamer, CD player, etc. are left out.
Added to this is SMSL's experience in implementing 2x ES9038Q2M, which can also be seen in the performance of the SMSL DO100.
But I would recommend it for a headphone amp like the SP400 just because of the XLR connectors. But that's just my opinion, of course nobody has to share it.

The Topping D10 Balanced is certainly a good device with the special SPDIF output function, but that comes at the price of only USB input and only Balanced Output.

 

[Veri]

Balanced connection via 6.35mm jack, significantly poorer contact quality compared to XLR

In studio use, TRS balanced jacks are really widespread alongside XLR microphone cables. What "significantly poorer contact" are you talking about...

 

[Noob]

Exactly there I have a different opinion, but everyone should have their own.

Power supply for the D10 Balanced via USB, a no-go for me.
Balanced connection via 6.35mm jack, significantly poorer contact quality compared to XLR, plus only a few available cables to XLR.
Only balanced connection. According to Topping, RCA can only be connected with an expensive real electronic RCA -> Balanced Module.
Only connection via USB possible, all other devices that are connected via SPDIF, e.g. TV, streamer, CD player, etc. are left out.
Added to this is SMSL's experience in implementing 2x ES9038Q2M, which can also be seen in the performance of the SMSL DO100.
But I would recommend it for a headphone amp like the SP400 just because of the XLR connectors. But that's just my opinion, of course nobody has to share it.

The Topping D10 Balanced is certainly a good device with the special SPDIF output function, but that comes at the price of only USB input and only Balanced Output.

I see your point.
But the contact quality thing is probably a myth. Both TRS and XLR are just metal touching metal. And it's actually quite easy to convert TRS to RCA. No fancy device needed.

RCA to 1/4'' TRS Cable | Made from Mogami 2549 Neglex Cable & Neutrik Gold & Amphenol Gold Connectors | Pro Audio LA

Save money on custom cables at Pro Audio LA : Lifetime warranty included : Any length, configuration, or color. Get what you need : 323.319.5936

www.proaudiola.com

Other than that, I understand preference for non-usb power and using other types of digital input.

 

[Veri]

And it's actually quite easy to convert TRS to RCA. No fancy device needed.

RCA to 1/4'' TRS Cable | Made from Mogami 2549 Neglex Cable & Neutrik Gold & Amphenol Gold Connectors | Pro Audio LA

Save money on custom cables at Pro Audio LA : Lifetime warranty included : Any length, configuration, or color. Get what you need : 323.319.5936

www.proaudiola.com

This is unbalanced. Plugging unbal into bal source's output will lower performance quite a lot in most devices. Someone measured just that in the D10 balanced thread and it was really not good using the device this way. I would advise against it.

 

[Roland68]

And it's actually quite easy to convert TRS to RCA. No fancy device needed.

I specifically pointed this out because most users do not realize that they are purchasing a purely balanced device with the D10 Balanced.
The D10 Balanced uses a balanced output circuit that does not conform to the usual studio standard for 2-pin jack or RCA adapters.
Please also note the posts by JohnYang1997 #484 #513 and the note on the Topping page:

 

[Roland68]

In studio use, TRS balanced jacks are really widespread alongside XLR microphone cables. What "significantly poorer contact" are you talking about...

But the contact quality thing is probably a myth. Both TRS and XLR are just metal touching metal.

Over 30 years of experience with stage technicians and studio technicians. Talk to a stage technician about which plug connections cause the most problems. For every 100 problems with a jack there is one with XLR, if at all.
In addition, jack plugs are much more susceptible to contamination such as sweat, grease/oil, etc. and are subject to greater wear (the leaf spring contacts of the sockets are literally ground off every time they are plugged in and lose their coating)
But this is not a new topic. The problems and disadvantages of the jack connection were already known in the professional field in the 80s and 90s. Where the jack wasn't enough, XLR was used, which at the time was definitely a question of cost.
It was often measured back then, but it's old hat.

The problem simply lies in the simple construction of the jack plugs/sockets.
The XLR plugs have an approx. 1 cm long socket and plug for each plug contact, which contact each other all around and over the entire length. The same principle can be found e.g. with Lemo laboratory plugs.
Depending on the socket, contact is made with the jack plugs on one or two sides via a plate (leaf spring). This metal sheet is bent in such a way that it only has a small contact area.
So you only have a small folded piece of sheet metal that rests on a very small spot on a pin.
The purpose of this plug connection is the same, which leads to an inferior contact quality. This plug-in connection was developed with the aim of being inexpensive, safe contacting and easy to use. This small contact surface (in reality often far below 1mm², especially due to cheap production and large tolerances) in connection with the high contact pressure, you get a secure contact (high contact pressure per mm²), but with the loss of good contact quality.
Contact pressure and contact area vary from contact to contact, even with the same socket, and change over time due to decreasing contact pressure, wear and tear and dirt.
Even a slight pull from the cable to the plug changes the contact resistance at the individual contacts, and of course not evenly.
Sometimes you even hear volume differences L/R with the headphones, or changes when you turn the plug a little.
But you can't lump everything together here and of course most of the jack plug connections work inconspicuously.

Jack plugs come from a time when all other connectors were x times more expensive and in the stage and studio area you usually needed a few hundred of them.
Today, XLR connectors are cheaper than jack connectors.

But let's be honest, most people go to great lengths here and the devices with headphones cost a few hundred to well over a thousand euros. Good, gold-plated XLR plugs and sockets cost between 0.80 cents and around €5.00.
Then why use such an antediluvian plug contact as a jack plug?
Or does anyone think that XLR is not the better connector contact?

But that was enough OT in the SP400 thread from me (luckily the SP400 has a jack and XLR ;o).

 

[Veri]

But let's be honest, most people go to great lengths here and the devices with headphones cost a few hundred to well over a thousand euros. Good, gold-plated XLR plugs and sockets cost between 0.80 cents and around €5.00.
Then why use such an antediluvian plug contact as a jack plug?
Or does anyone think that XLR is not the better connector contact?

Fair enough

 

[Noob]

Over 30 years of experience with stage technicians and studio technicians. Talk to a stage technician about which plug connections cause the most problems. For every 100 problems with a jack there is one with XLR, if at all.
In addition, jack plugs are much more susceptible to contamination such as sweat, grease/oil, etc. and are subject to greater wear (the leaf spring contacts of the sockets are literally ground off every time they are plugged in and lose their coating)
But this is not a new topic. The problems and disadvantages of the jack connection were already known in the professional field in the 80s and 90s. Where the jack wasn't enough, XLR was used, which at the time was definitely a question of cost.
It was often measured back then, but it's old hat.

The problem simply lies in the simple construction of the jack plugs/sockets.
The XLR plugs have an approx. 1 cm long socket and plug for each plug contact, which contact each other all around and over the entire length. The same principle can be found e.g. with Lemo laboratory plugs.
Depending on the socket, contact is made with the jack plugs on one or two sides via a plate (leaf spring). This metal sheet is bent in such a way that it only has a small contact area.
So you only have a small folded piece of sheet metal that rests on a very small spot on a pin.
The purpose of this plug connection is the same, which leads to an inferior contact quality. This plug-in connection was developed with the aim of being inexpensive, safe contacting and easy to use. This small contact surface (in reality often far below 1mm², especially due to cheap production and large tolerances) in connection with the high contact pressure, you get a secure contact (high contact pressure per mm²), but with the loss of good contact quality.
Contact pressure and contact area vary from contact to contact, even with the same socket, and change over time due to decreasing contact pressure, wear and tear and dirt.
Even a slight pull from the cable to the plug changes the contact resistance at the individual contacts, and of course not evenly.
Sometimes you even hear volume differences L/R with the headphones, or changes when you turn the plug a little.
But you can't lump everything together here and of course most of the jack plug connections work inconspicuously.

Jack plugs come from a time when all other connectors were x times more expensive and in the stage and studio area you usually needed a few hundred of them.
Today, XLR connectors are cheaper than jack connectors.

But let's be honest, most people go to great lengths here and the devices with headphones cost a few hundred to well over a thousand euros. Good, gold-plated XLR plugs and sockets cost between 0.80 cents and around €5.00.
Then why use such an antediluvian plug contact as a jack plug?
Or does anyone think that XLR is not the better connector contact?

But that was enough OT in the SP400 thread from me (luckily the SP400 has a jack and XLR ;o).

I guess you have a point. It still takes a very long time and very many cycles for a 1/4" Jack to start showing actually significant wear that compromises the integrity of the connection, but I will admit XLR connections have much more consistent long-term reliability.

I just don't consider it an issue with something like a DAC where one is very rarely plugging and unplugging cables, unlike the jack on a guitar or a DI that would show issue much quicker due to almost daily plugging and unplugging, and even with those high-usage cases, the plugs last quite a while.

So while technically correct, I think it's not really an issue for DAC that just gets installed in a system and then doesn't get messed with.

 

[mrjayviper]

how warm/hot does this get during normal operation? Thanks in advance!

(a thought came to mind suddenly. is the heat given out by the device directly proportional to volume?)

 

[Noob]

how warm/hot does this get during normal operation? Thanks in advance!

(a thought came to mind suddenly. is the heat given out by the device directly proportional to volume?)

It doesn't get very warm at all.

 

[mrjayviper]

It doesn't get very warm at all.

I'm very tempted to get an audio-gd dac/amp combo (I was blinded by all that parts) but I have a strange feeling 3 transformers + what seems to be a circuit running in Class A is not going to be pleasant in my home office that has no aircon in summer.

 

[Lupin]

I'm very tempted to get an audio-gd dac/amp combo (I was blinded by all that parts) but I have a strange feeling 3 transformers + what seems to be a circuit running in Class A is not going to be pleasant in my home office that has no aircon in summer.

I would have to dig up my infrared thermometer to be sure but just by touch I would say my Topping A30Pro gets hotter than my Audio-GD NFB-11.38

Don't know what your situation is but I can't imagine my Topping nor Audio-GD being any influence on my room temperature..