SMSL SP400 Review (headphone amp)

[bequietjk]

Dat channel balance.

 

[JB5150]

It seems to me that you prioritize loud volume far more than others on this forum. Do you own an FA-10 PRO? It seems like that would be the ideal end-game amp for you. The sp200 has very high gain, but will distort if you try to push he6 or some other crazy headphone through them at the volumes you seem to enjoy because it doesn't have the current delivery for extremely low sensitivity headphones, or at least that is what I gather from other reviews.

If you want truly limitless headroom to power any headphone to insane level, I think you should probably get an FA-10 PRO from Flux Labs.

Just a suggestion since it's probably the most powerful dedicated headphone amp on the market right now both in gain level and in max output power, and very low noise and distortion if the measurements are correct.

Just thought you might be interested in that. It's definitely overkill for the vast majority, but it seems like it was made for you.

Thanks for the hardware suggestion! I'll look at the amp you mentioned (not that I need ANOTHER amp hehe).
I do listen loud sometimes, but more importantly, I use a LOT of Headroom Management and Volume Leveling in Roon. This useage results in -3db to -8db of output truncation.
The "EXTRA" gain and volume is useful in an amplifier for me due to my Roon useage.

 

[Noob]

Thanks for the hardware suggestion! I'll look at the amp you mentioned (not that I need ANOTHER amp hehe).
I do listen loud sometimes, but more importantly, I use a LOT of Headroom Management and Volume Leveling in Roon. This useage results in -3db to -8db of output truncation.
The "EXTRA" gain and volume is useful in an amplifier for me due to my Roon useage.

That's definitely a good reason to want an amp that gives you extra gain to make up for what you lost. But my personal approach to your issue would be a dac that outputs at a higher voltage, because you are not outputting line level signal to your amps. But if you have a dac that you really like and don't want to change it, that is also understandable. There are multiple acceptable ways to solve the issue. And an amp with tones of gain is valid as long as that doesn't introduce too much noise.

 

[bgtip]

I have a question: should I set the DAC volume to 99 and control the overall volume from the amp, or should I set the SP400 to 99 and control the volume from the DAC?

This is my setup - SU-9, SP400 with Goldplanar GL2000, all fully balanced:

 

[cursive]

I have a question: should I set the DAC volume to 99 and control the overall volume from the amp, or should I set the SP400 to 99 and control the volume from the DAC?

This is my setup - SU-9, SP400 with Goldplanar GL2000, all fully balanced:

View attachment 113426View attachment 113427View attachment 113428

Nice setup! For best performance I would leave the SU-9 at 99 volume, and use the SP400 for the volume. This gives you the best SINAD, and also lets you take advantage of the resistor ladder volume on the SP400 which has perfectly matched channel balance.

 

[Noob]

What cursive said. 100%


The major advantage of the sp400 over something like the A90 is the volume control.

So you should definitely use it since you paid extra for that feature.

If you don't use it, you would have been better off saving the money and getting an A90.

 

[w1000i]

Which amp has more power, THX SMLS, A90, the SA-1?

SA-1

 

[bequietjk]

From a production/recording standpoint the SP400 is going to do wonders with that perfect channel balance.

 

[Veri]

SA-1

I think from someone who owned both, the A90 was actually marginally louder.

 

[Noob]

From a production/recording standpoint the SP400 is going to do wonders with that perfect channel balance.

That's my hope.

I'm glad it's finally available in something much cheaper than the Benchmark HPA4.

The Sparkos labs Aries also has it and is reported to measure similarly well to the Benchmark but with even lower noise floor and is cheaper than the Benchmark. . . but it is still over $2000.

This is the only product I'm aware of in this level of uncolored neutrality that has a stepped attenuator at under $2000. And not only under $2000, but under $700! I wish someone had done it sooner.

 

[bequietjk]

When it comes to my next amp purchase, for an upgrade, it must come with superb channel balance as recent manufacturers such as SMSL have begun to implement. I believe it is the next standard in amp features.

 

[cursive]

Amir posted this in his initial measurements. 4.1w per channel @ 50 ohms max power, this is balanced output with 4.0v balanced input. Is there some math I could do to calculate how many watts would be output at 50ohms with 5.3v balanced input? Unsure of the correct formula, or perhaps more information is needed.

 

[Noob]

Amir posted this in his initial measurements. 4.1w per channel @ 50 ohms max power, this is balanced output with 4.0v balanced input. Is there some math I could do to calculate how many watts would be output at 50ohms with 5.3v balanced input? Unsure of the correct formula, or perhaps more information is needed.

View attachment 114037

5.43W

You take the ratio of the two voltages, in this case 1.325.
Then you multiply the wattage at four volts by the ratio you got in step 1.

And that's how you get 5.43watts at 50ohms

The only times this does not hold true are when the amp is current limited. But the current limits of this amp are actually quite high, so there is no problem with the higher voltage.

 

[cursive]

5.43W

You take the ratio of the two voltages, in this case 1.325.
Then you multiply the wattage at four volts by the ratio you got in step 1.

And that's how you get 5.43watts at 50ohms

The only times this does not hold true are when the amp is current limited. But the current limits of this amp are actually quite high, so there is no problem with the higher voltage.

Awesome, thank you so much, not only for the answer, but explaining the formula. Helps me estimate output with a new headphone I have coming.

 

[Noob]

Awesome, thank you so much, not only for the answer, but explaining the formula. Helps me estimate output with a new headphone I have coming.

You are very welcome.

 

[Chuck S]

I agree. I computed 6.25 watts at 16 ohm. More may be available though if you drove it at more than 4 volts input. You would then need a DAC that can go up that high which is rare.

Bought one to replace Cayin iha6 driving Susvara via Matrix Element X. Definitely does not output 12 watts, but is very sweet sounding and does the job, albeit at much higher volume settings than Cayin. Very musical, actually (at risk of sounding ironical).

 

[cursive]

Bought one to replace Cayin iha6 driving Susvara via Matrix Element X. Definitely does not output 12 watts, but is very sweet sounding and does the job, albeit at much higher volume settings than Cayin. Very musical, actually (at risk of sounding ironical).

Well the Susvara is the hardest to drive headphone I know of, and if it can bring it to satisfying levels I'm not sure what more someone could need. I'm really enjoying mine as well, so no power complaints here either. Nothing wrong with having the volume on the higher end of the scale.

I was taking another look at Noob's math above, and if Amir computed 6.25 watts @ 16 ohm on 4 volts input, it would need 7.68 volts input from the dac to get 12 watts output @ 16ohms. That would then match their printed specs. I've never heard of a DAC with that high of voltage output, but perhaps there's one out there somewhere.

 

[Noob]

Well the Susvara is the hardest to drive headphone I know of, and if it can bring it to satisfying levels I'm not sure what more someone could need. I'm really enjoying mine as well, so no power complaints here either. Nothing wrong with having the volume on the higher end of the scale.

I was taking another look at Noob's math above, and if Amir computed 6.25 watts @ 16 ohm on 4 volts input, it would need 7.68 volts input from the dac to get 12 watts output @ 16ohms. That would then match their printed specs. I've never heard of a DAC with that high of voltage output, but perhaps there's one out there somewhere.

There are DACs that can produce very high output, but they are typically more professionally marketed studio gear. The RME ADI-2 DAC can get close.

Pro gear can run at 24dBu which translates to about 12.2Vrms

 

[cursive]

There are DACs that can produce very high output, but they are typically more professionally marketed studio gear. The RME ADI-2 DAC can get close.

Just looked it up and you're definitely right! I didn't realize the ADI-2 was so powerful, it's near 7v out at +19dbu.

I think SMSL must be smart enough to know they stretched the truth a bit, 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.

Again this is nitpicking though, I recently got a used SP400 and have no problems with it's level of output. Especially considering I don't think the volume is linear. 79-89 seems like it's a much bigger jump than 29-39 on the volume knob, but I'll have to measure this with multimeter sometime to be sure.

 

[bgtip]

Well the Susvara is the hardest to drive headphone I know of, and if it can bring it to satisfying levels I'm not sure what more someone could need. I'm really enjoying mine as well, so no power complaints here either. Nothing wrong with having the volume on the higher end of the scale. ...

Higher end of the scale? What do you listen to?
This is my moderate listening level on 99dB sensitivity Goldplanar GL2000: