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SMSL SU-8 Version 2 Balanced DAC

I heard you can fixed the problem by yourself if you know a little bit of electronics with the old version. You only need to change the connections of the three wires connected to the switch. Be patient they will tell you how to deal with the wire connection. By the way, actually mandy has said that the old version they purposely designed the best listenning condition is around or less than -6db, when amirm test with 0db it showed poor performance because of the power supply could not drive high enough voltage. It will show similar thd+n results as v2 if amirm test with -6db.
 
helloworld said:
I heard you can fixed the problem by yourself if you know a little bit of electronics with the old version. You only need to change the connections of the three wires connected to the switch. Be patient they will tell you how to deal with the wire connection. By the way, actually mandy has said that the old version they purposely designed the best listenning condition is around or less than -6db, when amirm test with 0db it showed poor performance because of the power supply could not drive high enough voltage. It will show similar thd+n results as v2 if amirm test with -6db.
Click to expand...

So sounds like even in V1 this is a non-issue when using the built-in volume control feeding directly into say a power amp as most likely you will never be close to 0db, or even likely -6 for that matter..
 
Roen said:
@amirm Perhaps you should update the titles of the two threads and graph entries to V1.2 and V1.0 respectively?
Click to expand...
Whether they did it because of my review or otherwise, seems like version 2 is sticking:

1543446026292.png


So I think at this point we should stick to "version 2" even though PCB revision is different.
 
gvl said:
So sounds like even in V1 this is a non-issue when using the built-in volume control feeding directly into say a power amp as most likely you will never be close to 0db, or even likely -6 for that matter..
Click to expand...
Yes, that’s what their engineer thinks. For normal listening use, they don’t think there’s any flaw with the old version. If you really want the 0db output, you only need to do the wire connection change.
 
looks like 1.1 splits the difference between 1.0 and 1.2 unsurprisingly. There is a bigger fuse, some different resistor values on some of the blocks, and a few other changes. I would like to know where 1.1 falls performance wise though
IMG_20181128_180417__01.jpg
 
Measuring the voltage at the indicated positions on v1.1, I'm reading 4.8v, so unfortunately I don't believe 1.1 has the fixes applied
 
Roen said:
I'd still go with tone board over the SU-8. If you use the balanced out, you can't use the third gain stage. If you want the third gain stage, the tone board and the su-8 are similar in performance, but the tone board is much cheaper.

Maximum 2.1 Vrms for the third gain stage of the 789. 4~Vrms on balanced out on the SU-8 makes it unusable for the 789's third gain stage.
Click to expand...
Why do you need the 3rd Gain stage on the 789 when you are already at 4V rms input from the XLR of the SU-8 ??
 
maxxevv said:
Why do you need the 3rd Gain stage on the 789 when you are already at 4V rms input from the XLR of the SU-8 ??
Click to expand...
It’ll work out quite similarly but +10 dB @ 2.1 Vrms will probably eek out a little more power than 0 dB @ 4Vrms.

I don’t know, someone might need that power.
 
Roen said:
Can you do that playing DSD files?
Click to expand...
The ES9038Q2M certainly supports it. I would consider any DAC offering volume control that doesn't work with DSD to be a flawed design.
 
derp1n said:
The ES9038Q2M certainly supports it. I would consider any DAC offering volume control that doesn't work with DSD to be a flawed design.
Click to expand...
I was always under the impression that you had to play DSD at full volume and use the analog volume to adjust. You learn something new everyday.

I guess I’ll test for myself on the D50.

When did DACs offering volume control become a thing anyway? I always thought it was the Amp’s job to control volume.
 
I found a link talking about ess chip with the DSD file volume control: https://www.computeraudiophile.com/forums/topic/19381-ess-sabre-and-dsd-volume-control/
Here is John Siau's explanation of how DSD volume control is done in the Benchmark DAC2. The DAC2 uses the ES9018 DAC chip.

MW: How do you handle volume control in that final output stage? Do you convert to analog and then turn it up and down.

JS: We actually don’t. We do process that at the high sample rate and we have multiple 1-bit converters that are available to us. So the increase in word length that we get as a function of that volume control makes use of the redundant 1-bit converters that we have running in parallel.

MW: I see.

JS: So we’re not converting it…in a way you could look at that as if it’s PCM because there’s multiple 1-bit converters summed together in the analog domain. But that’s what you have to do to get volume control to work. The good thing is we don’t take it from 1-bit to multi-bit and back to 1-bit before we convert it to analog.

MW: Yep, as you were saying before.

JS: Instead of sending identical DSD signals to sixteen balanced 1-bit converters that are wired in parallel, we start sending different DSD signals to reduce the signal amplitude. All summing occurs in the analog domain. It is very cool!


Roen said:
I was always under the impression that you had to play DSD at full volume and use the analog volume to adjust. You learn something new everyday.

I guess I’ll test for myself on the D50.

When did DACs offering volume control become a thing anyway? I always thought it was the Amp’s job to control volume.
Click to expand...
 
Roen said:
When did DACs offering volume control become a thing anyway? I always thought it was the Amp’s job to control volume.
Click to expand...

Around the time people started plugging their digital sources directly into power amplifiers and eschewing the preamplifier. It was possible due to
a) the high output level (2.0V) and
b) the low impedance of the output stages of CD players.

I would peg it at about 1985/6 when remote controlled motorized output level controls started appearing on top model CD players. Many power amplifiers started to get additional 'CD direct' inputs and soon after we started to get digital level controls on CD players operated by remote. The 2nd set of variable outputs were designed especially for that purpose of going straight to a power amp.

Then a few standalone D/A converters got level controls and the rest is history as they say. :)

Up until recently, doing it in the digital domain wasn't much good. We got noise (clicks), coarse control and distortion as bits were chucked away. Not the case anymore.
 
Roen said:
It’ll work out quite similarly but +10 dB @ 2.1 Vrms will probably eek out a little more power than 0 dB @ 4Vrms.

I don’t know, someone might need that power.
Click to expand...

The 789 has 3 stages. So its not maxed at 0dB at 4Vrms. There is still a 2nd stage gain to be used. That is like +5 or +6dB gain if I remember correctly.

But who in the world needs that kind of power for headphones ?
I can only think of only 1 current one (the RAAL SRH1A ) that needs more than the power available through the 789 .
That one needs something like 50W of power. (You jolly well connect it to a Class A power amp for that kind of power and forget about headphone amps. )

Crazy but that's what they spec'd.
 
Roen said:
It’ll work out quite similarly but +10 dB @ 2.1 Vrms will probably eek out a little more power than 0 dB @ 4Vrms.

I don’t know, someone might need that power.
Click to expand...
Alternatively one could use balanced out with SU-8 balanced in, which yields +6 dB (@ 4Vrms) on Gain 2, according to 789 specs.

I was originally considering the D50, but am now leaning heavily toward SU-8 V2 given that it's balanced and performs better than D50 in most tests. Coupled with the 789 and 6XX's I can't imagine power will be a concern in my use case.
 
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maxxevv said:
The 789 has 3 stages. So its not maxed at 0dB at 4Vrms. There is still a 2nd stage gain to be used. That is like +5 or +6dB gain if I remember correctly.

But who in the world needs that kind of power for headphones ?
I can only think of only 1 current one (the RAAL SRH1A ) that needs more than the power available through the 789 .
That one needs something like 50W of power. (You jolly well connect it to a Class A power amp for that kind of power and forget about headphone amps. )

Crazy but that's what they spec'd.
Click to expand...
I was under the impression the gain stages were -10/0/+10, which is why we see the weirdness in the channel imbalance in low gain, as shown by @amirm graphs.
 
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