SMSL SP400 Review (headphone amp)

[Xaviedie]

thank you all, i will analyze everything

 

[v1adpetrov2]

It is perfectly normal for the balanced signals to be debalanced after the input and rebalanced after the volume control, before the amplifier stage. This has been done for tens of years and is the case even with many devices costing several thousand dollars.
Few devices are fully and consistently balanced.
To see that, you just have to pay attention to whether the volume control has 2 or 4 channels. So stereo vs. quad potentiometer, 2-channel or 4-channel chip on the volume control, 6-8 relays or 12-16 relays, etc.

I completely agree with you!
A balanced signal is not an end in itself and the device can transform it internally into an unbalance and process it in various ways.
The important thing is how it is implemented in a particular device.
A closer analysis circuits of the SMSL SH-9, SMSL SP400, Topping Pre90 and the latest Topping A90 Discrete revealed the same typical primitive differential amplifier circuit used to convert a balanced signal into an unbalanced one.
The circuit does not have any tuning elements to suppress the common-mode component and looks something like this:

As a rule, without tuning and using 1% resistors, this circuit will provide suppression of the common-mode component of about 40 dB, but tuning will allow you to significantly improve this value.
Theoretically, the suppression of the common-mode component can be infinite, but if the resistances are balanced within ±1 Ohm, 80 dB or even more can be expected.


And we would like a better hardware implementation of this scheme for such a cost of these amplifiers.

 

[Roland68]

They're expensive! I'm usually going for Cordial cables (on amazon).

The cheap Cordial cables are not so cheap for nothing.
Really cheap China plugs made of cheap materials are used, just hold a magnet to the jack plug. Only Cordial can tell you whether the cables used are really original.

As is the case everywhere, if a product is cheaper in retail than the parts for it are wholesale, then something is wrong.
You can also find original Cordial cables with high-quality branded connectors, but they are no cheaper than the ready-made cables from Sommercable, Mogami (World's Best Cables) or Gotham.

 

[BenF]

The cheap Cordial cables are not so cheap for nothing.
Really cheap China plugs made of cheap materials are used, just hold a magnet to the jack plug. Only Cordial can tell you whether the cables used are really original.

As is the case everywhere, if a product is cheaper in retail than the parts for it are wholesale, then something is wrong.
You can also find original Cordial cables with high-quality branded connectors, but they are no cheaper than the ready-made cables from Sommercable, Mogami (World's Best Cables) or Gotham.

I don't get your point. All my Cordial cables have Rean/Neutrik connectors. Are you saying these are bad connectors?

 

[Roland68]

I don't get your point. All my Cordial cables have Rean/Neutrik connectors. Are you saying these are bad connectors?

Please post a picture of your plugs (of the cheap cables), then I can tell you that more precisely.

 

[Roland68]

I completely agree with you!
A balanced signal is not an end in itself and the device can transform it internally into an unbalance and process it in various ways.
The important thing is how it is implemented in a particular device.
A closer analysis circuits of the SMSL SH-9, SMSL SP400, Topping Pre90 and the latest Topping A90 Discrete revealed the same typical primitive differential amplifier circuit used to convert a balanced signal into an unbalanced one.
The circuit does not have any tuning elements to suppress the common-mode component and looks something like this:
View attachment 250134
As a rule, without tuning and using 1% resistors, this circuit will provide suppression of the common-mode component of about 40 dB, but tuning will allow you to significantly improve this value.
Theoretically, the suppression of the common-mode component can be infinite, but if the resistances are balanced within ±1 Ohm, 80 dB or even more can be expected.
View attachment 250137 View attachment 250138 View attachment 250139 View attachment 250140 View attachment 250141

And we would like a better hardware implementation of this scheme for such a cost of these amplifiers.

Of course, these devices can still be improved, but they are low cost/low budget devices that we are talking about here. Most devices on the market with such equipment cost x times more, although they are not necessarily better.
Check out expensive preamps, headphone amps, AVRs, and especially AV preamps. I agree with you and sometimes I can't understand how cheap it is.

But the bigger question is, would the SP400 really sound better if you changed that part of the circuit? Would it be audible? If not, what is the higher effort for, also in development?
I would change some things about the power supply on the SP400, but even then it would be questionable whether it is really audible.
Out of 10 significantly more expensive (¢ 800-12000) headphone amplifiers, only one was audibly better than the SP400 for me, but also more than $ 5000 more expensive.

But in this price range you have to save, especially on development costs. At some point a line has to be drawn. If not, you will die beautiful.
Most people don't realize that the manufacturer often only sees 30% of the amount paid.
Of this, equipment packaging and padding, remote control, power cables, housing parts, components, circuit boards, assembly, all building costs, energy costs, personnel costs, government taxes, development equipment, etc. must be paid for.
And of course the development costs, without which this device, the next device and also the company would not exist.

 

[siwmad]

Hi all,
I bought a used SP400 and in my opinion it plays too quietly. For comparison, I have Ho200, which plays much louder.
Does the amplifier sound quieter due to wear of the R2R volume control?
What are the symptoms of worn out R2R volume control?
I have HW version 1.0 on display, does that mean it is very old and the volume control may be worn out?

 

[Roland68]

Hi all,
I bought a used SP400 and in my opinion it plays too quietly. For comparison, I have Ho200, which plays much louder.
Does the amplifier sound quieter due to wear of the R2R volume control?
What are the symptoms of worn out R2R volume control?
I have HW version 1.0 on display, does that mean it is very old and the volume control may be worn out?

You can assume that nothing on the relay-based volume control is worn out. The device can be a maximum of 3 years old, not 30 years.

What gain level is the device at and what is the source?

 

[Snoopy]

Hi all,
I bought a used SP400 and in my opinion it plays too quietly. For comparison, I have Ho200, which plays much louder.
Does the amplifier sound quieter due to wear of the R2R volume control?
What are the symptoms of worn out R2R volume control?
I have HW version 1.0 on display, does that mean it is very old and the volume control may be worn out?

If you want loud , you will need a dac that outputs 5 volt or more

 

[siwmad]

You can assume that nothing on the relay-based volume control is worn out. The device can be a maximum of 3 years old, not 30 years.

What gain level is the device at and what is the source?

The source is smsl su-10 connected via xlr. DT-990 pro headphones, modded cable to balanced. I listen at 40 high gain and it's OK for me. What worries me is that Ho200 is much stronger. I think I read somewhere that the R2R regulation gets damaged over time and the symptom is an increasingly quiet sound. I'm not sure if this is the correct thesis.

 

[Jimbob54]

The source is smsl su-10 connected via xlr. DT-990 pro headphones, modded cable to balanced. I listen at 40 high gain and it's OK for me. What worries me is that Ho200 is much stronger. I think I read somewhere that the R2R regulation gets damaged over time and the symptom is an increasingly quiet sound. I'm not sure if this is the correct thesis.

How far from max is 40? Likely the HO200 just has a higher gain setting. If you have plenty of room left to max volume on the Sp400 I wouldnt worry.

 

[siwmad]

Max is 99

 

[Jimbob54]

Max is 99

Yes, the ho200 high gain is 23dB and the sp400 is 11.6.. Nothing to worry about if you're not anywhere near max.

 

[Roland68]

The source is smsl su-10 connected via xlr. DT-990 pro headphones, modded cable to balanced. I listen at 40 high gain and it's OK for me. What worries me is that Ho200 is much stronger. I think I read somewhere that the R2R regulation gets damaged over time and the symptom is an increasingly quiet sound. I'm not sure if this is the correct thesis.

This volume control has nothing to do with R2R, so maybe that's why you have incorrect information.
There are only resistors that are switched into the signal path for attenuation with the help of relays. Since the relays are not loaded at all, the probability of a defective relay is greater than wear and tear. In over 25 years of using such volume controls, I have never experienced or heard of any wear and tear.

However, you can never compare devices with each other in terms of the position of the volume control. The gain factor and characteristics of the potentiometer do not allow this comparison, especially not in terms of the possible performance.

 

[Snoopy]

The source is smsl su-10 connected via xlr. DT-990 pro headphones, modded cable to balanced. I listen at 40 high gain and it's OK for me. What worries me is that Ho200 is much stronger. I think I read somewhere that the R2R regulation gets damaged over time and the symptom is an increasingly quiet sound. I'm not sure if this is the correct thesis.

Low and High Gain doesn’t make much of a difference really.

I use headroom of -7db + convolution filter and with jazz recordings with a high dynamic range I’m often between 60-75 with my SP400. (Balanced)

 

[Audioboxer]

If supplied with a D10 balanced how much more power would this amp have over the L50? My L50 is acting up a bit and I'm considering my options for replacing it.

 

[Hal Rockwell]

L50 has no difference between the balanced and SE inputs which means it works as SE-only input. You can compare specs but the SP400 will have more power. The question is if you need more power.

 

[Audioboxer]

L50 has no difference between the balanced and SE inputs which means it works as SE-only input. You can compare specs but the SP400 will have more power. The question is if you need more power.

Just powering Sundara's just now so L50 is fine power wise, thinking longer-term if I'm replacing my L50 for it being faulty.

I know the L50 is only balanced in, not out, but it does seem to deliver pretty decent power on SE. I just struggle at times to figure out Amir's review graphs properly and decipher what would deliver more power to planar headphones lol (If I replace my Sundara it might be going up the HiFiMan range as I really like open back planars).

For example I was looking at the SABAJ A20h as a cheaper replacement for the L50 for now with my Sundara's but even although it's balanced it seems to have less power than the L50 SE for a pair of Sundara's!

 

[Hal Rockwell]

Just powering Sundara's just now so L50 is fine power wise, thinking longer-term if I'm replacing my L50 for it being faulty.

I know the L50 is only balanced in, not out, but it does seem to deliver pretty decent power on SE. I just struggle at times to figure out Amir's review graphs properly and decipher what would deliver more power to planar headphones lol (If I replace my Sundara it might be going up the HiFiMan range as I really like open back planars).

For example I was looking at the SABAJ A20h as a cheaper replacement for the L50 for now with my Sundara's but even although it's balanced it seems to have less power than the L50 SE for a pair of Sundara's!

You'll probably never need more power than the L50 puts out.

 

[Roland68]

Just powering Sundara's just now so L50 is fine power wise, thinking longer-term if I'm replacing my L50 for it being faulty.

I know the L50 is only balanced in, not out, but it does seem to deliver pretty decent power on SE. I just struggle at times to figure out Amir's review graphs properly and decipher what would deliver more power to planar headphones lol (If I replace my Sundara it might be going up the HiFiMan range as I really like open back planars).

For example I was looking at the SABAJ A20h as a cheaper replacement for the L50 for now with my Sundara's but even although it's balanced it seems to have less power than the L50 SE for a pair of Sundara's!

The L50 is SE only and therefore has the same power on the XLR output. The A20h only has half the power on SE as on XLR.
The SP400 should have a little more power and of course also has the relay-based volume control, but you are in a completely different price range.
There is now the topping A70 Pro in this price range and this puts them in the endgame range for HPAs in terms of performance.