Analyzing DACs

I sense the preamp is an afterthought for some of these low end DAC/preamps. Super high end ones may warrant a discussion however. I read the MSB select manual; the OEM suggests direct to amp connection. I'm not playing in that league. A high quality DAC in the 3k-5k range is ideal. Holo Audio and Exasound DACs are interesting. And maybe the Qutest.

+1 @bigkidz "You cannot pick a components by measurements alone."

Glad to see this statement in the first sentence to advise newbies more. A few years back I followed ASR tests, bought (and later returned) a highly praised DAC, with 125-128db signal to noise ratio, and all of these great measuring parameters.

Then, later to discover all of the different type dac connections were not tested and reported, and after playing the dac for a while it was one of the most sterile and boring sounding dac units I’ve ever tried or owned. The dac got returned for a full refund, thankfully. Agree, you cannot pick a component by measurements alone if you care about how it sounds too.

You cannot pick a components by measurements alone.  Price has nothing to do with sound quality.  You have not mentioned what type of sound you prefer so every recommendation here is completely useless.  Do you like a tube sound or SS sound and do you know why they sound different?
Most products use less expensive parts no matter what the price.  Parts make sound quality.  Power supplies are where you should start first.  Computer grade PS capacitors or Nichicon Supers?  Bradly resistors or Takman, Amtrans or Audio Note.  V-Capacitors?  If not then you get what you pay for.

As far as a DAC without a preamp, I would suggest that method until you find a preamp that helps your system sound better to your own ears.

You do not mention a price range.  So without that, I cannot assist you.

Happy Listening.
 

@tee_dee 

When you use the DAC as a digital volume control directly into an amp the DAC is lowering the bit depth and therefore taking resolution out of the bit stream.

If you want  less boxes then go with an integrated amp, I'm thinking you would very much like to have the volume control in the analog world.

Go forth and listen, then listen some more and then even more.  Talk is cheap. Trust you ears. They won't lie to you.

Regards,

barts

Interesting to me, how these discussions become so incredibly polarizing. Isn’t it true that there are many variables to consider here? A good sounding dac is a good sounding dac. A dac that measures well does not guarantee that its output stage will be particularly pleasing. But it is possible that a dac that measures well can also be a great good sounding dac. It is possible for a poorly measuring dac to still sound unique and wonderful. So much of this is subject to personal trial and error. However objectivist we’d like to be, two individuals with the exact same equipment will find differences in their setups for reasons that extend beyond their equipment.

Circuitry and the arrangement of internal components, board designs, filter caps (or lack there of), chips, or discrete circuits, wiring (and the amount of it), etc etc etc. all render different results. Question is, how do we listen? What are we finding or looking for when we do?

Not a guarantee, and there are some price conscious outlier/somewhat giant killer components out there…but I have found that quality components paired with good design = good sound. But I suppose even that’s too subjective.

There’s a lot to be said about separate components if you have the space. The two biggest issues are noise isolation and separate power supply’s. That’s where you get performance. 

I would say that the one advantage to following the ASR sheep is that the units recommended by ASR can be resold very quickly and without taking as much of a haircut in the process. 
 

That is a good observation.

Charles

@larryaa55

A costlier DAC should, at least in theory, produce more accurate output. Specs like ultra-low THD are not very important when considering which DAC to buy. Like I said before, if you can’t hear it, it doesn’t matter. Tons of negative feedback in the circuit and other shortcomings...and many who have not heard a lot of audio gear before are quick to praise it...simply because it produces sound/ouput!!

Ranking by cost alone may not provide the results you want. It’s all about the design topology, quality and longevity ratings of internal parts, protocols, USB controllor specs, and of course the designers intent. Do you want a very detailed DAC? then go hunting for "accurate or resolving DACs" online. A lot of pro audio gear (such as steinburg interfaces, for example are more suited for recordeding and will not reach the same level of performance as a standalone DAC. Once again, cost savings. 

At any rate, software settings on programs such as jriver can alter the sound quality of a DAC in many different ways. If you’ve got a resolving DAC that sounds cold for example, you can easily fixate its tonal quality to be a bit warmer and easier on the ears. The details in the music will still be there...just less obvious or upfront.

I’ve read quite a few of @jasonbourne52 posts, and much of what he says is practical and makes sense.

@tee_dee

Also, from my experience with my current equipment, some tracks are mastered at high levels. I assume the double gain (eg from the DAC and the preamp) exacerbates the loudness. Some tracks sound like screaming vocals. I assume that won’t allow me allow to realize the full potential of the amplifier if I have to listen at low levels.

Right, these folks don’t match for LUFS!! Look this one up...

Other problems include excessive dithering, not converting a CD quality file to 32 bit by 96 KHz or higher, dynamic range compression, Equalization mistakes, etc.

And you’re absolutely right about that. Having to turn down the volume because of problems with loudless won’t allow you to experience full extent of the music.

Which tracks? I’d love to fix them.

You buy hifi to listen to it, when buying a component, listen to it.

@steakster : congratulations! You are some sleuth! Yes, I am "roberjerman" and I have 4319 posts using that moniker. I suggest you read some of them! I changed my alias here on Agon because I couldn’t log-on when I got a new phone. I did buy a pair of speakers at the Greenwich Village, NYC Crazy Eddy’s in 1976. A pair of Acoustiphase two-ways large boxes - an Advent copy - for $200. I used them for a few months with a Marantz 2270 receiver. Sold them in the spring of ’77 and bought a store-demo pair of Infinity Monitors 1A with Walsh tweeters! By that time I had an AGI 511 preamp, GAS Son of Ampzilla, Mitsubishi DA-F10 tuner and an Empire 698 TT with a Dynavector 20B homc cartridge. How’s that for a late - 70’s high-end system! Speaker wire was Polk Cobra Cable and ICs were Verion Triaxials made by Mitch Cotter.

I would say that the one advantage to following the ASR sheep is that the units recommended by ASR can be resold very quickly and without taking as much of a haircut in the process. 

I was revamping a system last year and the first two units that sold "measured very well".  Those were the units I liked the least and thought would take the longest to sell.

For my next test I am going to try the GD Audio R-27 HE as a preamp/DAC combo.  It fit my needs for where it was going and the sources that would be connected.  Also, their latest DAC did very well in Stereophile which does not usually lavish praise on units in that price point. 

I’ve tried different scenarios:

Topping D70s dac acting as a preamp straight into a GoldNote PA10. Then a Creek integrated amp acting as a preamp preceded by the same dac switched to pure dac mode, Then eventually purchased an SPL Elector for a dedicated preamp instead of the Creek (same configuration).

This particular dac as pre sounded…pretty good. Decent stage, good clarity, bass weight ok.

with the Creek, sounded…pretty good. Just wider stage, more interesting tonally, but not as fast.

Enter SPL preamp…huge improvement, by several factors, at least. Wider and deeper, more balanced while being more tonally rich, but also more accurate/there. Much more clarity, bass weight, bass quality, presence, center image, believability, pace, speed, dynamics, refinement, smoother. Sometimes even have trouble stopping the music to pee, it’s so good.

It’s interesting how nuanced and variable sampling different components in the chain can become. But to me, a very well designed output stage (or series of very good output stages) can be a game changer.

Topping dac as a dac is great in this arrangement. Better than as a pre/dac. But a Chord Dave as a pre/dac? I would assume a whole other animal much much better than a topping pre/dac. But I’d still stick with my SPL pre, given the choice. Always with the prospect of getting an even better dac down the line.

@jasonbourne52 - There’s a review by Goldensound for the Denafrips Ares II that includes measurements that demonstrate the oversampling slow filter having some very unexpected and the fast filter appearing to measuring as expected.  The recommendation was to not use the slow filter.  I don’t know if the specific unit being reviewed had an issue, but it’s very interesting that the nearly unanimous consensus is that the DAC sounds the best using the slow filter.  I have not spent a lot of time comparing the two, but switched to the fast filter based on the review and recently went back to the slow filter and also preferred it’s sound. 
 

Experiences like this challenge my natural tendency to believe that something that measures better should sound better.  I’m starting to believe that measurements have little meaning because it’s become unquestionably clear that individual preferences simply do not align with measurements.

Objectivists accuse subjectivists of being subject to expectation bias, placebo effect, etc.  Is it possible that the primary factor in objectivists preferring the sound of equipment that they believe to be superior based on measurements is a result of the same factors?

@mastering92 And not all DAC chips are created equal. The easier it is to implement/ it can withstand all kinds of substandard parts tolerances and teperature variations/ the worse it will sound. Rather than have all parts when, which measured, do not vary wildly and will compliment eachother to create a high-performace unit

The tried and true formula seems to be cheap and low quality level parts then utilization of off the shelf OP-amps. One thing is for sure, these OP-amps will consistently provide very good test measurements.That’s the apparent objective target, measure good.

The sound quality reproducing music can be subpar. But that seems besides the point, and not the important criteria. The game plan is great measurements at a very low retail cost. OP-amps and their generous NFB will get the desired result.

Charles

Confusion is a part of audio unless you are pretentious enough to think you know all the answers as some in these forum posts are prone to pontificate🤣

I HIGHLY recommend, before you attempt to digest many of these opinions, purchase and read "The Complete Guide to High-End Audio", 5th edition, Robert Harley. You won't need to read it cover-to-cover unless you want, just refer to areas of interest. I downloaded the kindle version three years ago and still refer to it. He is an expert and well respected by many audiophiles. And he writes well enough for novice or pro.

You may want to search Hans Beekhuyzen's YouTube channel for great info on DACs et.al. He reviews, but does not try to sell. (For e.g., he reviewed several in the Denafrips line, Jay's Audio DAC ladder, the Arcam ST60, Mola Mola, Chord products, and the well respected NAD C658 (which you can simply use the DAC bypassing the preamp as in others). Decide if you want a Roon endpoint when considering your next DAC.

Have fun learning! And welcome to the wonderful world of audio! 

"How do more expensive DCS’s make a difference in sound quality? " Larry, a dac does not have to be more expensive to sound better. However a dac that uses better components and shielding should definitely sound better. Obviously you pay more for better components and shielding.

How do more expensive DCS’s make a difference in sound quality?  If they make a difference what will you hear that is different and why.  It sounds like upgrading a DAC to improve sound quality is the first upgrade one should do.  I would guess Jason Borne would know how to answer this question.  

I have 2 analog setups to run along with 4 digital ones, so running a dac directly into my amp is not an option. Preamp is a must for me regardless of sound issues. Love my wyred4sound stage2 preamp.

ASR is horrible most don’t know anything , measurements are only good for so much nothing to do with sound  . I don’t like preamp is a dac separates are almost always better.

I pair a JDS-Lab_Atom DAC to a Van Alstine Transcendence RB 10 preamp. The JDS is well-rated on ASR, is inexpensive, and sounds better than the DAC built into a HEOS2 box, for example.

I put the money into the Van Alstine. It is moderately expensive (that is, economical by audiophile standards 😉) and has proved to be an accurate and musical tube preamp.

@jasonbourne52

Because they all use descriptive language to describe what they are hearing with a new system, audio component, headphone, speakers etc. they have in for review. What HiFi does the same thing. So did the legendary Tyll Hertsens, former editor in chief of a now defuct site called: innerfidelity, the same domain is now "stereophile" He was the best reviewer in the world for headphones!

We could easily say that they are "subjectivists" rather than "objectivists" but then we start sounding too much like the minions at ASR; and I don’t want that.

Descriptors are necessary...just like someone trying to describe a personal experience, a food critic explaining what to do better next time, or even in the workplace when describing standard operating procedures or internal documentation regarding the skill or difficulty level. Therefore, using such language does not automatically turn someone into a subjective reviewer with no basis in the objective realilty of their review/testing.

The measurements on ASR are easy to replicate (if you know how to do them) and do not correlate with what we hear as humans. Extremely low THD specs for example; since achieving lower levels than is physically possible to hear is a rather pointless pursuit. But these brand keep doing it....because all that negative feedback in the circuit is dumbing down the performance; while making the specs look amazing on paper / online marketing material. And people buy in to it.

For example, the THX 789 sounds dreadful. I wrote an amazon review that you may want to check out. It explains why...

If Amir and his followers were the prophets of objective truth, many sectors in the audio industry would have collapsed by now..everyone would be buying ASR recommended gear, and ignoring the rest. People like to save money. So they would likely opt for cheaper components that measure well.

Like I said in previous posts, a null-test that allows us to see the actual ouput in a waveform is not done on ASR. In other words, using an ADC (analog to digital convertor). We can even use software that tells us if the ouput files are alike or indifferent with percentage match software. Run the same test track (30 seconds) through 3 different DACs or CD players - get different output each time...

He has not consulted real manufacturers or even veteren brands insofar as regarding how they measure audio gear; or even why their measurements are poor or just average; according to him and his pink panther figurine. He simply produces rash and impulsive reviews that do not depend upon proven or reliable testing methods. There are videos on YouTube where an employee working at audio precision explains why measurements don’t always translate to improved or even superior sound quality. His measurement system that costs as much as a half-average car, is made by that company: Audio Precision.

I’d much rather have Amir and his friends send their test results to Audio Precision, have them replicate the same test, along with null tests, comparing output files for their percentage of differences, wow, flutter, gang errors (between circuits) measuring the tolerances and voltage outputs inside the gear to see if it meets the engineering spec, reliability, circuit design carried out properly,  etc. I could keep going....but by now I think you and (perhaps others) get the point.

Paul from PSAudio weighs in on Preamp / No Preamp

@mastering92 : why not level the same charge at the scribes that write for Stereophile, TAS, HiFi+ ...? All those glossy ad pages ...

@jasonbourne52 

it is possible. For more information, just send me a message.

What a wealth of great information despite different views on components. Thanks for chiming in.

I like the advice to test in my own environment and trust the ears. Reviews and measurements have their place but a poor room set up and equipment matching might matter more.

I currently have a fairly entry level set up:

Bluesound N130>Brooklyn DAC>Parasound P 6>Parasound A21+>Revel M106 speakers.

My concern is that a $3k-$5k higher quality DAC requires an equivalent or better separate preamp. It sounds like the jury is out. Whether the preamp section is good enough I'll have to determine the best set up for my room and tastes.

Also, from my experience with my current equipment, some tracks are mastered at high levels. I assume the double gain (eg from the DAC and the preamp) exacerbates the loudness. Some tracks sound like screaming vocals. I assume that won't allow me allow to realize the full potential of the amplifier if I have to listen at low levels.

I won't even spark the debate about cables and power cords!

@mastering92 : so you imply that Amir is being bribed by unscrupulous audio manufacturers? And that's why Benchmark is highly rated? I'd like to have Amir respond to this!

This was a common way for sales men at audio stores to sell speakers! They made sure that speaker A was just a wee bit louder than speaker B. The customer always preferred A! 

@jasonbourne52 

Anyone who has done research on ASR will tell you the back story. I don't believe it it is personal for audio enthusiasts, but it is definitely personal for manufacturers of otherwise good audio gear. Him reviewing a product unfavorably can directly impact sales. That is bread and butter for the companies...their employees, electronics engineers, and founder etc. That hurts.

If you want to know all the research and info I have about ASR, send me a message.

As an example in an A/B listening test of two preamps, amps, CD players ... the component that has an output level 0.2db higher will always sound "better" - more exciting, more lively, more engaging! All due to a simple level difference! Yet most audiophiles are ignorant of this psychoacoustic fact! 

Lot of hate here for Amir and ASR! Measurements do matter! More so than "golden ears" listening because human hearing is easily fooled! Trying to have a discussion here with subjectivists is like Galileo confronting the Inquisition! 

In the publication’s DAC published tests the reviewers almost always tested the DAC connected directly to the amplifier. I think I understand why—nothing in the chain influencing the DAC sound. Is that the correct assumption?

No.  It’s very system dependent, but in my experience most systems benefit from a good preamp.  A lot of amps just need the added boost from a dedicated preamp to be driven optimally, so that will be of particular importance to pay attention to.  

This thread is getting sidetracked a bit but thought I'd put my 2 cents worth in.

The reliance on measurements is as old as this hobby. Back in the 1960's Julian Hirsch was editor of THE major Hifi magazine at the time, Stereo Review and he was one of the first to promote the concept that measurements are most everything. He was an electrical engineer and that's what they do, they measure things.  

Anyone who has been in the hobby a long time has experienced gear that measured well but didn't sound great.  "Everything that can be measured can be heard but not everything that can be heard can be measured". 

Now back to the OPs post. Different DACs have different output stages and implementations and will mate with different amps for better or worse. In one system I have a DAC that sounds very good direct into the power amp but to my ears sounds improved with a preamp, yet in my second system the same DAC not drive the power amps nearly as well and a preamp was definitely needed. A modern well made preamp will be transparent to the source but can add weight, drive and dynamics to a system.

I assume you have no preamp, just a power amp... and your system sounds good to you, then likely you can get by without a preamp, assuming the new DAC has similar output voltage. The gains you hear with a better DAC should be easy to hear. Then if you wants, buy a decent preamp on the used market and see for yourself, in your own environment, if its' a benefit. It's the only way you will know. If you find it adds nothing, you can easily sell it for what you paid. If you are building a new system, then getting an integrated amp does make sense as was previously posted.

Well then move along @jasonbourne52 and go sell some insurance.

I'd rather trust ASR's rankings than the subjective blather here.

@tee_dee

First, you will need to decide if you want your system to excel when bench tested, or to sound good. If the former then visit ASR, which does an excellent job of measuring and if the later, throw out sources that take money from the industry and use your ears.

In general, something that cost $1000 out performs something that cost $10, but this isn’t always the case. I recently put together a system from scratch over eight months. I had been heavily into this hobby twenty years ago, but then got married and lost my listening space. Now rectified, I had a 131/2’x24’x10’ dedicated room without anything in the room. So, to start out is the question of money. I started building the system without realizing that realistic musical reproduction requires lots of money. Consider building a digital system and forget the extra musicality of analog. That dream greatly increases expense. Next, visit your local shops with a budget in mind for an integrated amplifier and speakers. Only purchase based on the pairing that you have listened to. Buy the speaker/integrated combination together. Then I found a major internet dealer with a sixty day no questions asked return policy and most importantly, I found a sales person that really knew what he was doing. This step can also be provided with local dealers, but I will say that my purchases from local dealers were at MSRP and those through my internet dealer was greatly discounted. My sales person first concentrated on clean power and proper budget appropriate cables.. I made multiple trades, including returning some equipment and then buying a different component from a forum/dealer/member here who I have found to be absolutely reliable. Lastly, there are at least half a dozen people that post on this forum that have decades of experience and are willing to help you out.

So step number one is to decide if you are going to trust measurements, or your ears. Notice I’m saying trust your ears and not mine.

As I've said elsewhere, ASR doesn't do science.  They do quality assurance.

The idea of using those measurements alone to determine the pleasure I would derive from listening is ludicrous.  It's like knowing the HP of a car without knowing how it feels driving it.

If you want to know if you would like the sound of a DAC, or would prefer brand X over brand Y you need to listen for yourself.

@mastering92 That is exactly what I said. Open up one of these boxes and look at the poor quality components contained therein. Seriously, how could it be otherwise given the pricing.

As I am new to the hifi hobby, reading various product reviews and noting the details of the test environment have made me very confused.  I understand Stereophile is the hifi bible.

Well, not to me but I rely on their measurements.  I take only my own advice when it comes to sound quality.

In the publication’s DAC published tests the reviewers almost always tested the DAC connected directly to the amplifier. I think I understand why—nothing in the chain influencing the DAC sound. Is that the correct assumption?

Yes, fewer variables involved.  You already have the issues of the reviewer's speakers and room (not to mention advertiser dollar) influencing the experience. A preamp is yet another major variable the reader has to interpolate from.

If that’s the case why incorporate a preamp if the DAC has a preamp section that is a common feature even on high end DACs?

The role of a preamp has changed a lot, making it almost a vestigial component.  Besides switching sources, preamps also provided equalization (i.e. treble, bass, phono) , gain and impedance matching between a variety of sources and amplifiers.

If your needs are simple, with modern solid state amps and no vinyl playback, there's no electronic NEED for a preamp.   The reason you might incorporate a preamp is for the appeal of the sound quality of the preamp.  Nothing wrong with using a juicy and overly sweet preamp if you like the sound quality.

My one time experience with using a DAC as a preamp was that I didn't like the sound quality that much and if statically shocked during winter months the volume would jump to 100%, causing an alarmingly loud output. Instead I've settled on an integrated amplifier, and an outboard DAC.

DAC, Phono Stages: I suggest you buy from a source that accepts returns. 

@jasonbourne52

@laoman

ASR - Very inexpensive DACs, headphone amps, speakers, and even headphones that measure well. Because measurements alone are the bread and butter of these brands...it is the basis of their marketing material and the primary reason why people jump the gun and buy ASR-recommended gear. Let me tell you...it’s a pipe dream...

I have been disappointed my so many of the top-measuring audio electronics featured on that website..! To such an extent that I sold all of them!! From DACs, to headphone amplifiers, to USB C dongles for android smartphones that claim better performance on paper than any high-end stand-alone DAC. You would think that Hollywood studios, Sony Music Studios, and other big players in industry would using or recommending ASR gear by now...

High-end audio and the pro audio/live sound industries should have died off since the inception and frequently-posted publications on ASR - The industry as a whole has not adapted; and there are a multitude of reasons why they haven’t.

Products from those brands (You know who they are) are all "built to a cost" meaning that costs savings was all-important in terms of the quality of internal parts, design/implementation of DAC chips, the use of OP amps rather than discrete or custom types of FETs, poor quality casework that is feather-light and does not damp the internals properly, soldered-on inputs/outputs, vertical-chip capacitors that are computer-grade, rather than audio grade and therefore much cheaper to buy in bulk, the use of axial or radial capacitors rather than snap-in, the lack of ceramic saftey capacitors, no saftey resistors, and even the total absence of sacrificial fuses that blow in the event of a malfunction; to protect the inputs/outputs, reactive load (speakers, headphones), and the circuit itself. I could go on and on... lol

It is so easy to buy the latest DAC chip in bulk, slap it on a PCB, include a cheap crystal oscillator at 10 cents a piece, and have output. Therefore, the measurements are often not the total sum of parts inside the electronics, but the DAC chip at engineering standard itself. And not all DAC chips are created equal. The easier it is to implement/ it can withstand all kinds of substandard parts tolerances and teperature variations/ the worse it will sound. Rather than have all parts when, which measured, do not vary wildly and will compliment eachother to create a high-performace unit.

I understand what Amir is trying to do...he wants to be popular online. If you want the total backstory of ASR and why it exists, send me a message.

It’s great that you are asking a question about a new hobby but you also need to know some of the people you asking and if you should believe them or not.

ASR is a joke. Stereophile is a joke, tell me a review of any product that had a negative outcome, every product they review is the best of the best. Also, jasonbourne posts are all the same, if you spend more than $500 you spent too much.

Now, to answer your question about if you need a preamp or can you hook up the dac straight to the amp, it all depends. If you go jasonbournes way and go cheap, you are most likely going to need a preamp because they will go cheap on the volume control section and it will be noisy AND the dac might not have the range to  control the amps output. If you go with a much better dac (I paid over $8000 for mine), it has a quiet volume control and provides an attenuate button so you can properly control any amp. I sold my 5-digit preamp when I purchased this dac because my system sounded better without it and my volume setting is in the sweet spot of control.

Again benchmark Amps measure well on ASR but in reality they leave a bit to be desired. As far as the Topping Amp goes, that is reflective of the poor materials this company uses. This amp is not the only piece of equipment from that company that has problems. However, again you were told this.

@jasonbourne52 do you own any Benchmark equipment?

@laoman : that if I recall was the $349 Topping Class D amp. A new product. ASR considers the $3K Benchmark ABH2 amp to be the best in their survey. They rate the Benchmark DAC to be in their top class. 

"Regarding problems with cheap gear there are plenty of posts here about expensive gear needing repair" The only expensive gear I know of that got a good recommendation is the Tambaqui.
Are you aware that with one particular piece of equipment 38% of purchasers complained? You get what you pay for.

If you don't have a preamp, it cannot degrade the sound.

Listen to a DAC direct to amp at low volume and then listen to the same DAC via a preamp like the Benchmark LA4. There are some expensive DACs that are similar to the LA4 level of volume, such as the Lumin X1 with Leedh volume control. All DACs I have owned in the moderate price range were not good direct to amp at low volume.

@laoman : ASR has also given thumbs up to four-figure DACs. The measurements made using the Audio Precision APx555 are comprehensive. Regarding problems with cheap gear there are plenty of posts here about expensive gear needing repair.

I was fortunately enough to get a reference DAC or two from a high-end electronics manufacturer. Quote nice. But since my emphasis on on vinyl playback, the DACs, as spectacular as they are, iust another toy.

I’m trying to avoid unnecessary components if possible. Any thoughts would be appreciated.

op - buy a one box integrated unit with built in streamer, and speakers

or even powered, streaming speakers