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RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → Pairing an energizer with the ADI-2 DAC
Hey,
So I'll be getting a chance to try my first Stax tomorrow and was wondering about connecting the energizer with my ADI-2 DAC. Obviously just RCA-RCA but what about the integrated amp on the DAC? Do I just set it to 0db and control the volume from the energizer to get the optimal results?
... Stax tomorrow and was wondering about connecting the energizer with my ADI-2 DAC. Obviously just RCA-RCA but what about the integrated amp on the DAC?
Most STAX amplifiers have true balanced inputs and work balanced all through internally.
• So the best connection, if available, would be XLRf-XLRm.
If you don't have such cables go to a local music store and buy two short so called "microphone cables", preferable with Neutrik connectors like these e.g.:
https://www.rockshop.de/klotz-m2fm1-010 … -xlrm-xlrf
Don't pay more then 22€ each, these already are top notch studio quality.
RCA-RCA will work nicely too.
• ADI-2 DAC's headphones amps are not used for STAX.
Do I just set it to 0db and control the volume from the energizer to get the optimal results?
Yes, this way you get the best possible quality out of the DAC.
Switch off "Auto Reference Level" and set the Line Output: Ref Level to -5dBu.
This way you can use the most travel path on STAX Driver Unit's volume control.
STAX drivers don't need much input level for full scale drive.
Alright thank you.
exact wrote:... Stax tomorrow and was wondering about connecting the energizer with my ADI-2 DAC. Obviously just RCA-RCA but what about the integrated amp on the DAC?
Most STAX amplifiers have true balanced inputs and work balanced all through internally.
• So the best connection, if available, would be XLRf-XLRm.
If you don't have such cables go to a local music store and buy two short so called "microphone cables", preferable with Neutrik connectors like these e.g.:
https://www.rockshop.de/klotz-m2fm1-010 … -xlrm-xlrf
Don't pay more then 22€ each, these already are top notch studio quality.RCA-RCA will work nicely too.
• ADI-2 DAC's headphones amps are not used for STAX.
exact wrote:Do I just set it to 0db and control the volume from the energizer to get the optimal results?
Yes, this way you get the best possible quality out of the DAC.
Switch off "Auto Reference Level" and set the Line Output: Ref Level to -5dBu.
This way you can use the most travel path on STAX Driver Unit's volume control.STAX drivers don't need much input level for full scale drive.
"Do I just set it to 0db and control the volume from the energizer to get the optimal results?
Yes, this way you get the best possible quality out of the DAC."
That's factually incorrect, you can lower the volume up to -48db without any impact on dac's performance and even to 96db with extremely small impact, dare I say it "undetectable by human ears" and that's assuming that Ref Level is not set to auto, if you do set it on auto you'll get even more range.
most analog vol pots just do not match the performance of RME's vol control apart from multi thousand $ relay based pre amps likes the ones from Audio GD.
From my experience with stax I would set the volume knobs on energizer to max and do volume and LR balance on RME as staxs (and electrostat energizers in general) tend to suffer from channel imbalance.
As for XLR or RCA don't worry too much about it, if you have XLR use it, otherwise RCA will do just fine if you have good cables (Blue Jeans LC-1 etc...) and keep them shorter than 2.5 meters
exact wrote:Do I just set it to 0db and control the volume from the energizer to get the optimal results?
KaiS wrote:Yes, this way you get the best possible quality out of the DAC.
Switch off "Auto Reference Level" and set the Line Output: Ref Level to -5dBu.
This way you can use the most travel path on STAX Driver Unit's volume control.STAX drivers don't need much input level for full scale drive.
... That's factually incorrect, you can lower the volume up to -48db without any impact on dac's performance and even to 96db with extremely small impact, dare I say it "undetectable by human ears" and that's assuming that Ref Level is not set to auto, if you do set it on auto you'll get even more range.
most analog vol pots just do not match the performance of RME's vol control apart from multi thousand $ relay based pre amps likes the ones from Audio GD.
From my experience with stax I would set the volume knobs on energizer to max and do volume and LR balance on RME as staxs (and electrostat energizers in general) tend to suffer from channel imbalance.
As for XLR or RCA don't worry too much about it, if you have XLR use it, otherwise RCA will do just fine if you have good cables (Blue Jeans LC-1 etc...) and keep them shorter than 2.5 meters
Sebastian,
I just tried, following your proposal:
ADI-2 Pro -> 0,75m Audiolink C-X11 Blue, RCA-RCA cable -> STAX SRM-1/MK-2 Professional -> STAX SR L-700.
ADI-2 Pro Reference Level +4dBu (lowest setting available).
Bass +4dB (to my liking with the STAX SR L-700).
Tidal Masters "Instrumental Jazz" Playlist 88.2 and 96kHz masters.
The result was night and day:
• STAX Driver Unit volume full, RME ADI-2 Pro volume -54dB:
Scratchie, cold, piano and vibraphone sound like with pieces of paper on strings and keys.
Room sound, ambience, resolution gone, ..., ...
Simply no good, annoying!
• STAX Driver Unit volume ca. 8:30 position, RME ADI-2 Pro volume -4dB (to deal with the bass boost):
Warm, transparent, clear and detailed sound as one would expect from such a high-class set.
Just the opposite of above!
Fun to listen on this relaxed low sound level.
No stereo imbalance BTW, STAX potentiometers always have been very high quality. Anyway the control has the possibility to set L/R individually (split concentric).
To be true, I did not expect such an obvious difference, but wanted to try practically before I reply to your posting - you're simply wrong, sorry.
Sebastian.Athea wrote:exact wrote:Do I just set it to 0db and control the volume from the energizer to get the optimal results?
KaiS wrote:Yes, this way you get the best possible quality out of the DAC.
Switch off "Auto Reference Level" and set the Line Output: Ref Level to -5dBu.
This way you can use the most travel path on STAX Driver Unit's volume control.STAX drivers don't need much input level for full scale drive.
"Do I just set it to 0db and control the volume from the energizer to get the optimal results?
Yes, this way you get the best possible quality out of the DAC."
That's factually incorrect, you can lower the volume up to -48db without any impact on dac's performance and even to 96db with extremely small impact, dare I say it "undetectable by human ears" and that's assuming that Ref Level is not set to auto, if you do set it on auto you'll get even more range.
most analog vol pots just do not match the performance of RME's vol control apart from multi thousand $ relay based pre amps likes the ones from Audio GD.
From my experience with stax I would set the volume knobs on energizer to max and do volume and LR balance on RME as staxs (and electrostat energizers in general) tend to suffer from channel imbalance.
As for XLR or RCA don't worry too much about it, if you have XLR use it, otherwise RCA will do just fine if you have good cables (Blue Jeans LC-1 etc...) and keep them shorter than 2.5 metersSebastian,
I just tried, following your proposal:
ADI-2 Pro -> 0,75m Audiolink C-X11 Blue, RCA-RCA cable -> STAX SRM-1/MK-2 Professional -> STAX SR L-700.ADI-2 Pro Reference Level +4dBu (lowest setting available).
Bass +4dB (to my liking with the STAX SR L-700).
Tidal Masters "Instrumental Jazz" Playlist 88.2 and 96kHz masters.The result was night and day:
• STAX Driver Unit volume full, RME ADI-2 Pro volume -54dB:
Scratchie, cold, piano and vibraphone like pieces of paper on strings and keys.
Room sound and Ambience gone, ..., ...
Simply no good, annoying!• STAX Driver Unit volume ca 8:30 position, RME ADI-2 Pro volume -4dB (to deal with the bass boost):
Warm, transparent, clear sound as one would expect from such a high-class set.
Just the opposite of above!
Fun to listen on this relaxed low sound level.No stereo imbalance BTW, STAX potentiometers always have been very high quality. Anyway the control has the possibility to set L/R individually (split concentric).
To be true, I did not expect such an obvious difference, but wanted to try practically before I reply to your posting - you're simply wrong, sorry.
Just out of curiosity, I'm not familiar with energizers (I'm not too much into electrostats) is it perhaps solid state? As the issue you are describing is generally associated with transistors being pushed a bit too much (especially the problem with drive (input signal) amps, they can start acting like noise gates), it's a common issue with solid state energizers as transistors (unlike tubes) struggle to deal with voltages high enough to drive electrostats, stax solid states are infamous for having subpar performance compared to their tube counterparts. I don't remember the model I was listening but it was all vacuum tubes and I had exactly the opposite experience, actually now that I think about it I'm not sure if it was made by stax (sorry I listened to it at my friends place). And I haven't noticed any performance degradation on any power amps, and even the headphone amps set to max with rme and high volume attenuation around -60db and auto gain.
If you're using solid state energizer consider investing in a tube one, they don't sound like "tubes" at all, I think you'll be pleasantly surprised with the result, and if you do would you mind doing the same test? I would be very interested in the results.
I intentionally did NOT refer to any technical explanation this time, only listening results.
If you know my postings, technical expertise is my territory, besides beeing a recording engineer all through my life.
I do own 10 or so of STAX Driver Units, tubes and transistors, and an almost complete collection of all STAX headphones ever made.
STAX tube powered amps do use tubes only in the final output stage only, solid state in the stages before.
The volume control always is first, located ahead of all electronics.
So for the STAX amp's active part it doesn't make any difference where the user sets the volume, it's working with the same sized signal in both our cases.
And no, STAX amps in general are fully single sided class A throughout, no crossover distortion that can act like a "noisegate" and cut off or distort low level signals.
The SRM-1 MK-2 Professional is known as one of the highest resolution STAX amps available - if you get the right revision of it, and there are quite a few.
E.g. despite beeing single sided there's not a single coupling capacitor in the signal path - DC coupled throughout.
If you want to go technical:
download the data sheet of high end operational amplifiers and have a look at their distortion vs. level curve:
Even the best ones have their optimum at 3V level.
Going down to 0,003V (-60dB, kind of what you propose) the figures really don't look good any more.
That's what happens if you dial down ADI-2 xxx too far, all stages work on too low level.
The STAX amps have a cascode input, lot's (most) of their 60dB gain in the primary stage.
Output is in the 300V range at max.
No problematic extreme low level anywhere in the amp.
Lot's of drive, lot's of heat.
BTW:
From your other postings I know you're a recording engineer too.
So you certainly have learned:
for a good recording you have to bring your level up to studio standard in the input and keep it there through all stages of processing.
Else you either loose S/N ratio or headroom - dynamics.
I intentionally did NOT refer to any technical explanation this time, only listening results.
If you know my postings, technical expertise is my territory, besides beeing a recording engineer all through my life.
I do own 10 or so of STAX Driver Units, tubes and transistors, and an almost complete collection of all STAX headphones ever made.
STAX tube powered amps do use tubes only in the final output stage only, solid state in the stages before.
The volume control always is first, located ahead of all electronics.So for the STAX amp's active part it doesn't make any difference where the user sets the volume, it's working with the same sized signal in both our cases.
And no, STAX amps in general are fully single sided class A throughout, no crossover distortion that can act like a "noisegate" and cut off or distort low level signals.
The SRM-1 MK-2 Professional is known as one of the highest resolution STAX amps available - if you get the right revision of it, and there are quite a few.
E.g. despite beeing single sided there's not a single coupling capacitor in the signal path - DC coupled throughout.If you want to go technical:
download the data sheet of high end operational amplifiers and have a look at their distortion vs. level curve:
Even the best ones have their optimum at 3V level, going down to 0,003V (-60dB, kind of what you propose) the figures really don't look good any more.
That's what happens if you dial down ADI-2 xxx too far.The STAX amps have a cascode input, lot's (most) of their 60dB gain in the primary stage.
Output is in the 300V range at max.
No problematic extreme low level anywhere in the amp.
Lot's of drive, lot's of heat.
I work in audio field too although I'm self thought, I'm not gonna pretend like I understand all ins and outs of electrostats as they aren't really my thing for numerous reasons, most things that I know about them I learned from friend who is into them.
I have a question though; why would matter how you set the volume (adi2 or analog vol pot) is vol pot is the first thing in the chain, wouldn't it be the same if low level signal passed thru maxed out vol pot or if full signal is attenuated by vol pot?
I have a question though; why would matter how you set the volume (adi2 or analog vol pot) is vol pot is the first thing in the chain, wouldn't it be the same if low level signal passed thru maxed out vol pot or if full signal is attenuated by vol pot?
I edited my posting above, might already explain some.
The difference is what happens inside ADI-2 xxx.
In your proposal the levels in the analog part of ADI-2 xxx become extremly small, too small for even the best OPA's to handle them properly.
Not to mention that the best DAC chips have their limits too.
With the DAC at full level the whole signal chain works on optimum level.
As said, the active part of the STAX amp works with a fixed high gain in stage one, therefore high signal level throughout, no problem arises here.
It's simply, the STAX electrostatic headphones need several volts even if playing quietly.
A dynamic headphone would use only some 1/1000V (some mV) for the same loudness.
Inbetween ADI-2 and the final amplifier is STAX amp's volume potentiometer as "interface", to set the audition level:
1V from ADI-2 - reduced to 10mV by the volume control, passive with minor sideeffects - immediately boosted to several Volts again.
Result:
No transistor has to deal with problematic low levels.
A remark according the gain structure:
In theory it would make sense not to use a passive control right before the active part inside the STAX amps, but make the amp's gain variable, to avoid the down and up.
Practically this is not possible:
Optimizing the characteristics of a power amp that has to drive a load, is only possible for a certain amplification factor / gain.
Else you get instability or at least a compromized sound.
Sebastian.Athea wrote:I have a question though; why would matter how you set the volume (adi2 or analog vol pot) is vol pot is the first thing in the chain, wouldn't it be the same if low level signal passed thru maxed out vol pot or if full signal is attenuated by vol pot?
The difference is what happens inside ADI-2 xxx.
In your proposal the levels in the analog part of ADI-2 xxx become extremly small, too small for even the best OPA's to handle them properly.
Not to mention that the best DAC chips have their limits too.
All of my high end systems work with -40 to-30 for music and -27 to -9 for audio tracks, only system that requires around -60db of attenuation is one designed to emulate crappy speakers built into tvs. with that in mind I did not notice any quality drop with higher volume attenuation.
English isn't my first language so I just want to confirm; you are implying that that performance of your system is degrading due to loss of signal quality outputed from ADI2-dac at higher volume attenuation. If that isn't correct please ignore the rest of the post.
If it is correct though it would mean that either your unit is defective, or RME along with certain scientific audio review and equipment measuring site are engaged in serious case of false advertising as it would go directly against the specifications provided by RME, listed in manual (page 64&65), and confirmed in a review.
Also I googled stax amps and I'm pretty sure one I listened to wasn't made by stax, because it had exposed tubes.
The diagram on manual page 65 is done in the digital domain, showing the precision of calculations in ADI-2 DAC's 42bit digital domain.
The results are as expected, kind of.
I could do the same in my DAW in 32bit Float with the same result and wouldn't need ADI-2 for it.
The measurement is not showing the DAC and analog section of ADI-2 DAC.
To see this, kind of, go to manual page 59, this time with fullscale signal showing a different picture.
I intentionally did not refer to theory or measurements, just listening.
My results where surprisingly obvious: at -54dB digital volume control signal degradation is clearly audible.
Everybody with a STAX system can easily reproduce the test.
The STAX SR L-700 / SRM1 MK2 Professional system is one of the highest resolutions you can get.
It might reveal things that other headphones would not.
The music, instrumental jazz, presented in 24bit 96kHz, did it's part.
Heavy metal guitars (your favorite style, according to your postings) might bury some of the artifact I heard.
Due to the high voltages and the balanced architecture measurements at a STAX amp's output are complicated and need special preperations.
Time consuming, and one false move can easily fry expensive equipment with 300 or more volts.
I won't do it.
@ KaiS: your theory about loss of signal quality at lowest levels is based on a misunderstanding. The data sheets of opamps do not show higher distortion at lower levels - just the opposite. The lower the level the lower the distortion. It is only the noise part that gets bigger and bigger the lower the level falls. Also the statement 'best at 3V' does make sense to me. The opamps that we use in the ADI have their best performance (THD+N) near max level, which is around 20 dBu or 7.7 V. This is also where expensive measurement systems like the APx555B run into their limits. THD of -140 dB and better and THD+N of -123 dB and better can not be measured anymore.
Below +20 dBu THD becomes unmeasurable, noise rises proportionally.
While I can't explain your listening experience I would be cautios of using volume pots in extreme positions. Full up should be ok. High attenuation might cause a low pass filter effect between pot and the following electronic circuit. One would need to measure it to be sure that is not the case. Which might be problematic if there is no output available other than to the Stax phones.
@ KaiS: your theory about loss of signal quality at lowest levels is based on a misunderstanding. The data sheets of opamps do not show higher distortion at lower levels - just the opposite. The lower the level the lower the distortion. It is only the noise part that gets bigger and bigger the lower the level falls. Also the statement 'best at 3V' does make sense to me. The opamps that we use in the ADI have their best performance (THD+N) near max level, which is around 20 dBu or 7.7 V. This is also where expensive measurement systems like the APx555B run into their limits. THD of -140 dB and better and THD+N of -123 dB and better can not be measured anymore.
Below +20 dBu THD becomes unmeasurable, noise rises proportionally.
While I can't explain your listening experience I would be cautios of using volume pots in extreme positions. Full up should be ok. High attenuation might cause a low pass filter effect between pot and the following electronic circuit. One would need to measure it to be sure that is not the case. Which might be problematic if there is no output available other than to the Stax phones.
Thanks for confirming this, I was staring to wonder if my ears are failing me; as I never noticed any performance degradation when maxing out volume knobs, just the opposite in some cases, especially with THX AAA 789 which got surprisingly more cleaner and transparent with it's vol pot set to max and volume controlled by RME.
KaiS's energizer might have a weird quirk though, it wouldn't surprise me as solid state energizers are known to be a bit quirky, most electrostat ppl recommend using transformer like WOO audio WEE coupled with low voltage amp if you "must" go with solid state to power your electrostats.
Matthias:
I measured the frequency response at the STAX SRM-1 MK2 Pro's output:
Flat line, within <0.02dB 5Hz-20kHz, completely independent of "Level" (that's the label) control setting, even in the most critical -6dB position.
This measurement was done with Fluke 8060A, no risk, this thing is unbreakable.
A setup for spectrum analysis via the STAX SR L700 and a Bruel&Kjaer Artificial Ear 4153 did just show that neither setting has visible distortion components.
This measurement was limited by the low audio level related S/N ratio of just about 70dB, so only shows that nothing really bad (Sebastian: no obvious "quirks") is going on.
Then I repeated the audition under more controlled conditions
I built an adjustable "stopper" for the STAX level control.
This way I got exactly repeatable level settings with 50dB between full scale and dialed down.
Now I could do (sighted only) A/B comparison.
Everything else as described before.
Result: same as before.
Even better gripe on it now that I can fast and easy switch back and forth.
Too obvious difference to be just imagination.
I have to admit:
You have to be concentrated and relaxed.
Need a quiet and undisturbed surrounding.
The listening level is really low, ca. 70-75dB SPL Peak at max.
If I go up with levels only moderately the difference diminishes, I tried that.
My current approach for an explanation:
When I dial down ADI-2 Pro to -54dB a lot of the musical component are, of course, way below that level, specially with the music program I choose.
Lot's of space between the notes where you can hear sound decays, ambience and reverb, all kinds of micro-details.
I'd estimate these being down to -100dBfs or lower with ADI-2 Pro's -54dB setting.
Might be the DAC chips resolution isn't sufficient any more down there.
The OPA's might not distort at low level (I'd even question that for push-pull output stages), the DAC certaily does if it has just a few bits left to work with.
I have to admit this all is just a humble attempt to find an explanation.
I'm thinking about a way to measure that.
Might be I need to revoke and adapt my measurement system for capacitor distortions that can analyze distortions down to -155dB.
I'll have to find something to deal with the very low levels.
Sebastian:
Your statements about stuff "known to be quirky" made without personal experience and, quasi quoting without naming the source, doesn't help much.
There is no "common knowledge" in the audiophile community, it's 99% mumbo-jumbo without underlying facts.
People throwing around technical talk without having any technical insight.
Red cables sound warm, blue cables sound cold ... you got what I mean.
I'm trying to find evidence for what I can clearly and repeatably hear.
I know I am scratching on a base that Matthias an his team has established, and I don't do this lighthearted.
I'm an objectivist, have the knowledge and the equipment, and will do my best to do exactly that: finding objective reasons for what I hear.
You as a colleague, are 1000% welcome to chime in with whatever idea you have, but I'd kindly ask you to do me the favor and leave out hearsay please.
Sorry if things I said about electrostats were formed like facts, I have little 1st hand experience with them and I repeated what I was told by people who I know and who are into electrostats.
Unlike you, I don't have equipment or knowhow to do analog measurements, but I haven't noticed any loss in signal quality at higher attenuation with my RME ADI-2 DAC fs, even on very clean and transparent systems including electrostats I auditioned; actually in some cases my experience where exactly the opposite.
@ KaiS: At a -54 dB setting with +4 dBu Ref level the remaining SNR is 117 - 54 = 63 dB, RMS unweighted. That is not better than my old Dolby B cassette deck. If the Stax amp still allows you to hear at normal listening volume then you should hear low volume noise all the time. You will not be able to hear distortion, it's just simple noise. Maybe that noise biases your hearing so you can get better into details 
When you do so don't talk about 'resolution' or 'bits left' as it steers you into the wrong direction. There is no issue, only noise. Even with a few lowest bits only, the original signal can be still found (forum member kstr has done research deeeeep into the noise by thousands of averages of such signals).
I forgot to mention that all of the volume settings I listed where with auto ref level enabled.
Hey KaiS I'm really curious about something if you don't mind testing it.
Could you enable auto ref level on your RME, set the volume to ~35db and adjust your energizer volume to comfortable listening level; how does it sound?
Thank you all.
I will have a closer look tomorrow.
The multi-average FFT is what I do to resolve -155dB distortions in caps.
The test signal level is higher.
As mentioned, the listening level with both, the ADI-2 set at -54dB volume, or the STAX down-dialed, sound levels are quite low, ~ 70dB SPL peak.
I don't hear any noise in either setting.
What I hear is a dynamic sound change, peaks sound brigther, lower level signals duller.
Sorry to bump this thread, but is there a consensus as to what is the optimal volume settings with the ADI-2 while connected to a Stax amp (SRM 353X or any solid state amp)? Do we set the volume to 0db on the ADI-2 and control directly in the amp or full volume in the amp and control the volume on the ADI-2?
Sorry to bump this thread, but is there a consensus as to what is the optimal volume settings with the ADI-2 while connected to a Stax amp (SRM 353X or any solid state amp)? Do we set the volume to 0db on the ADI-2 and control directly in the amp or full volume in the amp and control the volume on the ADI-2?
I prefer enabling ADI-2’s Auto Reference Level, set volume somewhere between -20 and 0 dBr and then control the basic volume on the STAX “Driver’s” volume.
This way I can use ADI-2 for fine-tuning the volume.
I do use EQ, but don’t use ADI-2’s Loudness function.
With the STAX volume to full I would need to dial down ADI-2 to -50 dBr or even lower, as mentioned above this doesn’t sound perfect to me.
RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → Pairing an energizer with the ADI-2 DAC
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