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Review and Measurements of the PS Audio Stellar Gain Cell DAC

When I see measurements like this, I find it hard to escape the conclusion that it was deliberately designed to sound and measure the way it does. The motive? Anybody's guess.

At least we now know why the Joker is the way he is. Paul McGowan? Not so much.

The kindly, old grandfather of "high end audio" strikes again!
 
Last edited:
Though I personally don't have much interest in YAD (Yet Another DAC) and would like more on 'weaker links' in the chain (AVRs, Power Amps, Integrated amps, and specifically 'portable amps' including es100 and BTR3), I do have to congratulate and thank Amirm for exposing these frauds for what they are.

Thanks, Amirm!
 
It seems as if they designed their products badly on purpose

I can't understand that effort to use "solutions" that become trobles.
It can't be so difficult to design a DAC that simply fulfills its mission with dignity... Follow the chip designer's reference circuits and datasheets, without reinventing the wheel in each corner.

Wouldn't it be much easier for them to make a good product using proven components and reliable techniques instead complicating their lifes?
 
amirm said:
This is a review and detailed measurements of the PS Audio Stellar Gain Cell DAC. It is on kind loan from someone who read my review of PS Audio DirectStream DAC and wanted to know how this model of PS Audio DAC performs. The Stellar Gain Cell costs US $1,699 which as high-end audio DACs go is a "bit of a bargain."

The industrial design is good:

There is quite a lot of heft to the unit. Not a great fan of blue OLED display with tiny font for sample rate and filtering. Then again, I take this over blinking/color LEDs you are meant to interpret yourself on some other units. Volume control and associated display value is responsive which I appreciated.

The back panel shows the true value of this unit:

In addition to usual set of digital inputs we also have a set of analog inputs! For people like me who have Reel to Reel deck and others who have turntables, being able to integrate everything into the DAC and thereby eliminating an external pre-amp, this is great!

Inclusion of an analog pre-amp and switcher presents a problem for volume control though. Standard way of using the volume control built into the DAC chip (ESS in this case) doesn't obviously work for analog inputs. So companies resort to an external analog variable gain output stage. This brings is up to the name of this product, "Gain Cell."

The Gain Cell is the PS Audio name for a differential mixer circuit called Gilbert Cell. Using 6 transistors in a clever differential configuration, you can either mix two analog signals together, or use DC on one pair of inputs and control the gain of the other. The latter is what is used here. By controlling that DC unit using the front-panel microprocessor, you can now have control of the attenuation including the ability to have a remote control.

PS Audio contrasts this with using a potentiometer which could have longevity issues. That is true, but PS audio goes further, saying this scheme puts nothing in the signal path and hence is "pure" in execution:

View attachment 35202

Well, if anyone is able to test for "zero-loss" and "pure analog signal path is us." :) With instrumentation it is easy to see if the paper concept of Gilbert cell is realized in practice. While Gilbert cell is used in IC designs to good effect, there, matching of the transistors is easy. Not so in a discrete design as is used here. The transistors used to control the gain have their own non-linearities so the concept that there is no loss is quite dubious. But again, measurements will tell us all so let's get into that.

Pre-amplifier Audio Measurements
I fed a set of XLR signals to the Stellar Gain Cell from my Audio Precision APx555's analog output which has a SINAD well above 120 dB, with distortion products at vanishingly low levels. The signal is at 1 kHz so an ideal, zero-loss device under test would just produce a single sharp line and nothing else. This is what the Stellar Gain Cell (SGC) produces instead:
View attachment 35203

You are seeing what I am seeing? PS Audio, what the heck have you done to my pristine input signal?

Starting with the worst offenders, second and third harmonic distortions are way up at near 70 dB, resulting in SINAD (signal over noise and distortion) of just 68 to 71 dB. The distortion is asymmetrical between the channels showing lack of precision that way too.

But look at what else is going on. The button of our 1 kHz tone has been broadened. This indicates noise modulation of our signal much like can happen with DACs and jitter. Gilbert cell is also a modulator so any noise fed to its second input will modulate the primary (music) signal giving us what we are seeing. Not good.

Likewise, any power supply noise and spikes will also modulate our main signal creating sidebands on each side of our desired signal, creating that spray of spikes all around our 1 kHz tone we fed to the unit.

Put simply, we fed the Stellar Gain Cell one tone, and got dozens and dozens of unwanted tones and distortion product. The modulated ones are by definition not harmonic in nature so let's not have the argument that these are "good distortions."

At any rate, no way, no how this pre-amp and its core circuit can be called "zero loss" or "pure." There is nothing pure about it. Imperfect and non-matching transistors are in the circuit fed by noise and distortion that modulate them. The cure for potentiometer is far, far worse than the disease.

There are voltage controlled amplifier ICs used in Audio/Video Receivers and they perform far better than this.

We can test the non-linearities by feeding the unit dual tones: one low frequency and one high and compute the "intermodulation" distortion relative to the level of input signal:
View attachment 35204

Up to about 0.3 volt input, the Stellar Gain Cell is dominated by high level of noise. After that, distortion starts to take over. At full output level, one channel goes nuts far worse than the other (light green). At the nominal 4 volt output used in the dashboard and most of these tests, that doesn't happen but we suffer from higher levels of distortion than full output! This is backward of what typically happens in amplifiers.

Changing our tones to 19 and 20 kHz, we get high intermodulation distortion there as well:

View attachment 35205

Only the two tall spikes are the signal tones fed to the unit. Everything else is "non-pure" contributions from the Gain Cell giving us a usable distortion-free range of 70 dB (SINAD) which agrees with our dashboard.

Fortunately in some other areas things are not as broken. Frequency response is very flat and good:

View attachment 35206

Dynamic range is good too especially at full output although I am not sure how often you would use that:

View attachment 35207

Notice that both here and in our THD+N in the dashboard we are getting almost the same specs PS Audio advertises. This means our testing very much matches theirs and they are well aware of the poor measured performance of this unit.

Crosstalk audibly is fine as well:
View attachment 35208

DAC Audio Measurements
I was surprised to find out that the PS Audio chose a very low-end offering from ESS to use in this DAC: the ES9010K2M mobile DAC:

View attachment 35209

THD+N translates into a SINAD of 106 dB which is way, way better than the pre-amplifier in the PS Audio Stellar Gain Cell. So I thought we would get the same dashboard view as the pre-amplifier. I was wrong:

View attachment 35210

What? What??? How did the digital path cost us another 10 or more dB of distortion? What have you done PS Audio?

This is nothing short of disaster, placing the SGC DAC third from the bottom of over 175 DACs tested:
View attachment 35211

The SGC DAC uses an FPGA to supposedly clean up jitter. It is a wasted effort:

View attachment 35212

Noise floor is very high (in best DACs it goes under the AudioScienceReview tag). And we see countless sources of noise, jitter and unwanted spurious tones. No doubt many of these are contributed by the output gain stage but why bother with any digital jitter clean up when you are analog stage sprays a good bit on it?

Linearity is poor graphically:
View attachment 35213

But looking at the spectrum as the test was running showed that the actual tones produced by the DAC were fine but high amplitude spike at 180 Hz shown in FFTs was interfering with it. Linearity test uses a very sharp bandpass filter to exclude almost all noise and distortions but is wide enough to let the 180 Hz in. In other words, the little ESS DAC is trying to do right but the actual implementation steps on its output.

Multitone test simulate "music" with 32 tones shows the problem with this DAC vividly:

View attachment 35214

Since music has even more tones than 32, this means that no detail below -70 dB or so will be resolvable. Converting that to bits, you have 12 of them. Yes, 12 bits. Anyone who thinks they are hearing new detail they had not heard before with this DAC, should know that it is not the DAC that is doing that. It is your brain listening better than before and hearing detail that is well above -70 dB. Don't confuse perception with what your ears pick up.

There are only 3 filters for the DAC unlike the usual 7 or so:
View attachment 35215

The F1 filter is basically no filter. F2 and F3 are similar. F3 was recommended for best measurements and that is what I used for my testing. And would be my choice if I were to use this DAC.

The one benefit of digitally controlling gain is that channel matching should be good and is:

View attachment 35216

Listening Tests
I have to run out to our Audio Society meeting in half hour so no time for this. Will perform tests and update the review later. Owner was anxious to see the measurements so here they are.

Conclusions
The words on PS Audio website for Stellar Gain Cell DAC paint a super seductive picture of this DAC. The words "pure," "zero loss," etc. are music to everyone's ears, mine included. Going into this review I didn't think it would be exciting. Due to use of ESS DAC I thought the performance would be good. Nothing prepared me for the disaster that unfolded in front of me in test after test.

This DAC and pre-amp spray your beautiful recordings with a ton of noise, and distortion caused by non-linearities. The pre-amp/output stage is so bad that it gives you digital-like distortions while using a completely analog stage!

Then we have a DAC stage whose performance has been degraded by whopping 50 dB! Engineers kill themselves to get 3 dB improvement in noise and distortion at times. Yet, PS Audio destroys the purity of what comes out the ESS DAC by incredible 50 dB. Is there any hope that companies respec the word "high-fidelity" anymore?

I hear it: "but it sounds great to my ears." I am sure it does because a) audiophiles are terrible when it comes to critical listening abilities and hearing non-linearities and b) you don't know how to do proper listening tests.

So no, don't help bastardize this hobby any more than it already is by paying a fortune for a DAC and pre-amp which destroy any hope of fidelity to what the talent and engineers produced for us.

My head is down on behalf of the industry I participate in. :( Needless to say, I cannot recommend the PS Audio Stellar Gain Cell in any form or fashion. There is nothing that is stellar about its measured performance.

------------
As always, questions, comments, recommendations, etc. are welcome.

Please consider supporting reviews like this (I have to pay to ship this back) by donating using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Click to expand...
Digital experts...
 
BDWoody said:
Let the tantrums begin!! How long before someone comes in with one post, looking to tell us our ears and systems suck?
Click to expand...

Your systems are not revealing enough... Using an LPS and a Regenerator with this unit substantially increase the width of the soundstage and the blackness of the background.
There!

In all seriousness , when measurements are so bad. perhaps a second unit ought to be tested just to clear the air and for fairness sake .. Then again a second model from the same manufacturer has been tested ...
And to think that Schiit thought they had the excretory reference cornered ...;)
 
JRG said:
Wouldn't it be much easier for them to make a good product using proven components and reliable techniques instead complicating their lifes?
Click to expand...

But then that couldn't be used as a unique selling point in their marketing material, and it would minimize the allure of the boutique branding... :p;):rolleyes::facepalm:
 

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StevenEleven said:
Maybe kind of like this? :facepalm:

https://www.innerfidelity.com/content/ps-audio-stellar-gain-cell-dac-sound-quality

https://www.dailyaudiophile.com/ps-audio-stellar-gain-cell-dac-review/

https://www.headphone.guru/ps-audio-stellar-gain-cell-dac-a-new-era/
Click to expand...

...digital inputs produced gobs of detail, great dynamics, proper soundstage, and excellent extension. Ripped CDs and hi-res downloads sounded astoundingly good via USB input played by my player of choice, ...the analog inputs sounded clean, full, and lively. Exactly like I hoped they would!

The Gain Cell DAC is characterized by a clean, organic, and full bodied tone, which I definitely prefer to the starkness of many other all-in-one units. The Benchmark DAC 2, for example, sounds both thin and etched...

The detail was such that it produced a huge soundstage with the individual instruments portrayed separately in their own space, with their own individual timbre and sense of air. And the musicality was astounding. Even the harshest of instruments, such as trumpet or violin were put forth as a honeyed ideal. A quick cable change (to single ended) and engaging the Gain Cell awarded me with a straight from the DAC sound with amazing dynamic range and musicality.

Above is what passes for 'reviews', today. The 'reviewer' just inserts the device into his system, then pronounces all sorts of sonic descriptions that no one can decipher. Peer review? ...they may bring their wife in to confirm their conclusions. Very depressing.
 
amirm said:
This is a review and detailed measurements of the PS Audio Stellar Gain Cell DAC. It is on kind loan from someone who read my review of PS Audio DirectStream DAC and wanted to know how this model of PS Audio DAC performs. The Stellar Gain Cell costs US $1,699 which as high-end audio DACs go is a "bit of a bargain."

The industrial design is good:

There is quite a lot of heft to the unit. Not a great fan of blue OLED display with tiny font for sample rate and filtering. Then again, I take this over blinking/color LEDs you are meant to interpret yourself on some other units. Volume control and associated display value is responsive which I appreciated.

The back panel shows the true value of this unit:

In addition to usual set of digital inputs we also have a set of analog inputs! For people like me who have Reel to Reel deck and others who have turntables, being able to integrate everything into the DAC and thereby eliminating an external pre-amp, this is great!

Inclusion of an analog pre-amp and switcher presents a problem for volume control though. Standard way of using the volume control built into the DAC chip (ESS in this case) doesn't obviously work for analog inputs. So companies resort to an external analog variable gain output stage. This brings is up to the name of this product, "Gain Cell."

The Gain Cell is the PS Audio name for a differential mixer circuit called Gilbert Cell. Using 6 transistors in a clever differential configuration, you can either mix two analog signals together, or use DC on one pair of inputs and control the gain of the other. The latter is what is used here. By controlling that DC unit using the front-panel microprocessor, you can now have control of the attenuation including the ability to have a remote control.

PS Audio contrasts this with using a potentiometer which could have longevity issues. That is true, but PS audio goes further, saying this scheme puts nothing in the signal path and hence is "pure" in execution:

View attachment 35202

Well, if anyone is able to test for "zero-loss" and "pure analog signal path is us." :) With instrumentation it is easy to see if the paper concept of Gilbert cell is realized in practice. While Gilbert cell is used in IC designs to good effect, there, matching of the transistors is easy. Not so in a discrete design as is used here. The transistors used to control the gain have their own non-linearities so the concept that there is no loss is quite dubious. But again, measurements will tell us all so let's get into that.

Pre-amplifier Audio Measurements
I fed a set of XLR signals to the Stellar Gain Cell from my Audio Precision APx555's analog output which has a SINAD well above 120 dB, with distortion products at vanishingly low levels. The signal is at 1 kHz so an ideal, zero-loss device under test would just produce a single sharp line and nothing else. This is what the Stellar Gain Cell (SGC) produces instead:
View attachment 35203

You are seeing what I am seeing? PS Audio, what the heck have you done to my pristine input signal?

Starting with the worst offenders, second and third harmonic distortions are way up at near 70 dB, resulting in SINAD (signal over noise and distortion) of just 68 to 71 dB. The distortion is asymmetrical between the channels showing lack of precision that way too.

But look at what else is going on. The button of our 1 kHz tone has been broadened. This indicates noise modulation of our signal much like can happen with DACs and jitter. Gilbert cell is also a modulator so any noise fed to its second input will modulate the primary (music) signal giving us what we are seeing. Not good.

Likewise, any power supply noise and spikes will also modulate our main signal creating sidebands on each side of our desired signal, creating that spray of spikes all around our 1 kHz tone we fed to the unit.

Put simply, we fed the Stellar Gain Cell one tone, and got dozens and dozens of unwanted tones and distortion product. The modulated ones are by definition not harmonic in nature so let's not have the argument that these are "good distortions."

At any rate, no way, no how this pre-amp and its core circuit can be called "zero loss" or "pure." There is nothing pure about it. Imperfect and non-matching transistors are in the circuit fed by noise and distortion that modulate them. The cure for potentiometer is far, far worse than the disease.

There are voltage controlled amplifier ICs used in Audio/Video Receivers and they perform far better than this.

We can test the non-linearities by feeding the unit dual tones: one low frequency and one high and compute the "intermodulation" distortion relative to the level of input signal:
View attachment 35204

Up to about 0.3 volt input, the Stellar Gain Cell is dominated by high level of noise. After that, distortion starts to take over. At full output level, one channel goes nuts far worse than the other (light green). At the nominal 4 volt output used in the dashboard and most of these tests, that doesn't happen but we suffer from higher levels of distortion than full output! This is backward of what typically happens in amplifiers.

Changing our tones to 19 and 20 kHz, we get high intermodulation distortion there as well:

View attachment 35205

Only the two tall spikes are the signal tones fed to the unit. Everything else is "non-pure" contributions from the Gain Cell giving us a usable distortion-free range of 70 dB (SINAD) which agrees with our dashboard.

Fortunately in some other areas things are not as broken. Frequency response is very flat and good:

View attachment 35206

Dynamic range is good too especially at full output although I am not sure how often you would use that:

View attachment 35207

Notice that both here and in our THD+N in the dashboard we are getting almost the same specs PS Audio advertises. This means our testing very much matches theirs and they are well aware of the poor measured performance of this unit.

Crosstalk audibly is fine as well:
View attachment 35208

DAC Audio Measurements
I was surprised to find out that the PS Audio chose a very low-end offering from ESS to use in this DAC: the ES9010K2M mobile DAC:

View attachment 35209

THD+N translates into a SINAD of 106 dB which is way, way better than the pre-amplifier in the PS Audio Stellar Gain Cell. So I thought we would get the same dashboard view as the pre-amplifier. I was wrong:

View attachment 35210

What? What??? How did the digital path cost us another 10 or more dB of distortion? What have you done PS Audio?

This is nothing short of disaster, placing the SGC DAC third from the bottom of over 175 DACs tested:
View attachment 35211

The SGC DAC uses an FPGA to supposedly clean up jitter. It is a wasted effort:

View attachment 35212

Noise floor is very high (in best DACs it goes under the AudioScienceReview tag). And we see countless sources of noise, jitter and unwanted spurious tones. No doubt many of these are contributed by the output gain stage but why bother with any digital jitter clean up when you are analog stage sprays a good bit on it?

Linearity is poor graphically:
View attachment 35213

But looking at the spectrum as the test was running showed that the actual tones produced by the DAC were fine but high amplitude spike at 180 Hz shown in FFTs was interfering with it. Linearity test uses a very sharp bandpass filter to exclude almost all noise and distortions but is wide enough to let the 180 Hz in. In other words, the little ESS DAC is trying to do right but the actual implementation steps on its output.

Multitone test simulate "music" with 32 tones shows the problem with this DAC vividly:

View attachment 35214

Since music has even more tones than 32, this means that no detail below -70 dB or so will be resolvable. Converting that to bits, you have 12 of them. Yes, 12 bits. Anyone who thinks they are hearing new detail they had not heard before with this DAC, should know that it is not the DAC that is doing that. It is your brain listening better than before and hearing detail that is well above -70 dB. Don't confuse perception with what your ears pick up.

There are only 3 filters for the DAC unlike the usual 7 or so:
View attachment 35215

The F1 filter is basically no filter. F2 and F3 are similar. F3 was recommended for best measurements and that is what I used for my testing. And would be my choice if I were to use this DAC.

The one benefit of digitally controlling gain is that channel matching should be good and is:

View attachment 35216

Listening Tests
I have to run out to our Audio Society meeting in half hour so no time for this. Will perform tests and update the review later. Owner was anxious to see the measurements so here they are.

Conclusions
The words on PS Audio website for Stellar Gain Cell DAC paint a super seductive picture of this DAC. The words "pure," "zero loss," etc. are music to everyone's ears, mine included. Going into this review I didn't think it would be exciting. Due to use of ESS DAC I thought the performance would be good. Nothing prepared me for the disaster that unfolded in front of me in test after test.

This DAC and pre-amp spray your beautiful recordings with a ton of noise, and distortion caused by non-linearities. The pre-amp/output stage is so bad that it gives you digital-like distortions while using a completely analog stage!

Then we have a DAC stage whose performance has been degraded by whopping 50 dB! Engineers kill themselves to get 3 dB improvement in noise and distortion at times. Yet, PS Audio destroys the purity of what comes out the ESS DAC by incredible 50 dB. Is there any hope that companies respec the word "high-fidelity" anymore?

I hear it: "but it sounds great to my ears." I am sure it does because a) audiophiles are terrible when it comes to critical listening abilities and hearing non-linearities and b) you don't know how to do proper listening tests.

So no, don't help bastardize this hobby any more than it already is by paying a fortune for a DAC and pre-amp which destroy any hope of fidelity to what the talent and engineers produced for us.

My head is down on behalf of the industry I participate in. :( Needless to say, I cannot recommend the PS Audio Stellar Gain Cell in any form or fashion. There is nothing that is stellar about its measured performance.

------------
As always, questions, comments, recommendations, etc. are welcome.

Please consider supporting reviews like this (I have to pay to ship this back) by donating using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Click to expand...
I don't believe that this can be representative of the product. It's clearly broken. If the owner has given his permission, could you open it up and have a look? There must be loose bits ratting about in there, dry solders joints, cracks in PCB tracks, or something obviously wrong.
 
AudioSceptic said:
I don't believe that this can be representative of the product. It's clearly broken.
Click to expand...

Well, since the implementation of their $6K DAC was horrible... :rolleyes:
 
I wonder how their speakers will turn out, they went from the cool looking Arnie Nudell prototype to having a BG Neo tweeter in front of their BG Neo midrange and call it a coxial planar; I can’t for the life of me believe their claim that it won’t hinder performance; I need me some measurements.

I also wonder how their upcoming >$10,000 Obsidian DAC will perform, with it’s separate boxes for digital and analog components.
 
Last edited:
AudioSceptic said:
I don't believe that this can be representative of the product. It's clearly broken.
Click to expand...
My measurements for THD+N and SNR/DNR almost completely match that of PS Audio. So no, it is not broken.
 
And as others have pointed out, why would you not use a chip with good performance? It doesn't market well or actually sound different. Automatically limiting the appeal to certain markets and how much you can charge. The PS audio pitch for decades has been simple circuits, and this aura of we are guru's who listen and make circuits with something extra in the sound beyond simple measurements. It is apparent now what that 'extra' is.

Do they listen and decide? Do they fool themselves into circuits that sound like it has extra because of barely audible noise and extra meat and detail that is really sourced from nominally audible distortion? If so not much different than SET amps or such. They have a sound, and you are buying into their "good taste" in design choices. It seems an odd choice to make something more difficult to produce, uses more expensive components, and even if it has a sound, sure is a long strange way to result in nearly broken result in terms of performance. If they own it as their approach, then okay. Ted didn't own it. Maybe Paul will own this for the whole company as being what they intend.
 
amirm said:
My measurements for THD+N and SNR/DNR almost completely match that of PS Audio. So no, it is not broken.
Click to expand...

I think this point needs to be highlighted. Their published specifications are reasonably met, so there is little or no deception or false advertising.

Judging by the factory video tour I linked in another thread, the company appears healthy, clearly productive, and perhaps they understand their customers well enough to continue designing products along the lines they are. They are not saying their products are state of the art as far as I can tell.

Care needs to be taken with reviews and comments to prevent ASR appearing like yet another internet web site with a vocal lynch-mob membership.
 
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