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I may not have golden ears (not sure), but, last night, I was playing with passive vs. 0-gain active on my Schiit Kara preamp, and I can easily hear the difference (and greatly prefer the preamp in passive mode).
This becomes interesting when one looks at the specs:
Passive
THD+N unmeasurable with APx555; below analyzer capability
Balanced to Balanced
Gain: 1 (0dB)
Frequency Response: 20Hz-20Khz, -0.1db, 3Hz-500KHz, -3dB
THD: <0.0002%, 20Hz-20KHz, at 4V RMS
IMD: <0.0002%, CCIR
SNR: >129db, A-weighted, referenced to 4V RMS
So, THD & IMD levels well below .0002% are audible?
It seems so. Something is.
(My system is probably pretty transparent, with a NAD M23 and Quad ESLs downstream.)
(Oh, by the way, Schiit's tubed version of this preamp is *Stereophile Class A,* among a sea of $30,000 wonders - and the non-tube version sounds better IMO. For $800.)
I have served as a benchmark listener. My hearing acuity is world renowned.
What do we hear with our ears?
The reason you rarely if ever see distortion spec's for loudspeakers is because that would not help sell them, in light of the numbers people are used to seeing with electronics.
Also, many had noticed that a measurement like THD may or may not indicate how it sounds.
It was pretty good when all there was were tube amps that behaved similarly, not so now.
The reason is we measure the entire range equally because with instrumentation that is easy. You don't want any preferred or shunned frequencies haha, same for a loudspeaker.
Examine the ear's equal loudness curve, if you are used to a "frequency response curve", invert that equal loudness curve shape and now you have a hearing sensitivity curve, that's the shape of it's frequency response..
Your ears ARE NOT flat in sensitivity. There are several ramifications to this;
Examining the curves again, you will notice that at 20Hz, it takes about 75-80dB SPL to reach the threshold of audibility while around 4KHz, around 0dB is the threshold.
What Dolby labs discovered in an early paper was given that sloped curve, that at the threshold of audibility at 20Hz, the 3rd harmonic of only 7% had an equal perceived loudness as the 20Hz signal.
One conclusion was there is no practical way to make a subwoofer with inaudible distortion.
Looking at the hearing curve inverted, one can see that when harmonics fall in the 3-4KHz range, that is where your ears are most sensitive to distortion. This is why at work with the Unity and Synergy horns I put an acoustic low pass filter between the mid range drivers and the horn throat. That attenuates the distortion above crossover that the drivers produce and would fall in that most sensitive range.
Why do loudspeakers sound bright, gritty etc when driven hard? ALL the distortion components add content 1,2,3,4etc octaves above the original signal.
Ok, this part was simple, the next part reminds me of what one of my audio hero's, the late Dick Heyser once said something like "we measure what we do because we can, not because these are the most revealing of what we are investigating". So many questions i would ask him now.
So actually a lot is known about how our ears work but it is the image painted by the kinds of measurements we can do and some of these show unexpected behavior, like how the ears shape and pinna responses were the missing detail of how we localize sound..
Doug Jones, former co-worker was one of the team that discovered these what look like flaws, position dependent notches in our hearing and then went on to make the LEDR recordings demonstrating these effects.
So far as distortion itself, an unexpected thing is called "perceptual masking" and this is the idea behind data compression, various degrees of don't count what you can't hear (easily).
Our hearing is apparently divided up into segments about 1/6 octave wide (called a Bark) and what one finds is that IF one has a single tone, that on either side of that tone is an area "masked off" or that you can't detect a second tone in that area until it's above this masking level.
Also, the even harmonics are musically related and in the recording process, it was either the white album or Abby road where they intentionally (new circuitry) added distortion to enrich parts.
A figure i remember was that a 2nd harmonic was inaudible as a flaw with music up to around 30% but with organic / natural sounds (not harmonic sounds ) that it was audible at around half that level.
An over driven woofer, maybe most drivers produce a 3rd harmonic the strongest and a familiar sound.
And then there is the top side of the sensitivity curve.
The falling hf sensitivity is why (in % numbers) we are comparatively insensitive to high frequency distortion. You can hear 20KHz and higher, it depends on how loud it is and if there is any other sound that masks it AND how far away you are as depending on temp and humidity 20KHz can be absorbed surprisingly fast by the air itself.
I find this to be an especially interesting area to investigate so if inclined, google some of these things.
Distortion measurements would help sell the speakers I listen to - Quad 63/988/2805s - because, at ~.1% across the audioband, the only dynamic speakers that can compete cost around ten times their price.
(And anyone can get a good used pair for ~$2,000.)
Mr. Servo
Your response reminded me of an astonishingly spec'd 0.009 THD preamplifier produced during the mid 70's solid state audio spec olympics by a highly regarded company.
The preamplifier had a variable Bass Contour control that offered me another level of welcome subwoofer control.
While I didn't doubt the companies THD figure the preamps overall presentation seemed overly sterile. Not necessarily a bad thing in the world of audio but as a Bassist a little dirt in the sauce seemed to be missing.
Great response, thanks.
.
I think the primary understanding to consider is that human hearing is only subjective.
the rest of this stuff is just expounding on that statement. no offense intended to those who have already given this audiophile centric concern some thought. or to those who haven't.
if one thinks something sounds good, it does. that is your reality. right or wrong, you will never know, nor care about challenging your own lifelong reality. unless you are a scientist interested in understanding the brain.
this is not to deny reality, but one must be aware that hearing is always only subjective . it did not evolve to be able to objectively analyze hi fi sound, and lacks that ability.
the brain is not concerned with anything other than reporting something to resolve a passing uncertainty and then moving on to the next needed report. because, in uncertainty is threat, and categorizing threats is the evolutionary advantage.
the brain doesn't spend the time to be objective , and such thinking was never an evolutionary advantage. it will make stuff up to fill any uncertainty, that's why suspersticious people only see ghosts at night , when optical uncertainties are more prevalent. errors in hearing have no finite enabling conditions , but it is established fact that the brain will report as a reality what one might desire to hear.
today , logic is the evolutionary advantage. and logic must inform that what the brain reports as hearing becomes each persons separate reality, real or illusionary , one would never know.
understandably , setting a course encompassing the theory of " I don't know what I hear but I can enjoy the reality my brain provides" would upset a lot of audiophiles who think that certain people hear better than standard issue ears can manage, and that they can buy a bunch of stuff and ultimately achieve perfection in sound.
it could very well be that the real advantage of mega buck systems is to play to the ego and to strengthen the owners concept of what they think sounds good. because does it really sound better than a child's suitcase record player , to that listener. most children would know the difference, but wouldn't care.
on a personal note. I am very interested in the new phono stage Michell Engineering was showing at an audio show. I am very biased toward the brand, since I enjoy the very well thought out design of the gyro turntable. I also think that modern designs have the ability to be informed from classic designs from the past, giving some modern designs a market advantage of applied knowledge and modern manufacturing. As employed in the Michell Gyro, a design largely informed by customer feedback and engineering knowledge.
conventional tests using uncorrelated sine waves have little relevance.
Uncorrelated to what?
A fundamental property if waves is that they interact to create interference so they are correlated to each other. Maybe you were trying to suggest that sine wave testing is not well correlated with the subjective experience, which does seem to be the case.
(not sure about you) but I never listen to sine waves. Just too boring! ;)
I'm with you on that.
The active stage is committing sins we don't know about.
dynamic challenges often posed by passive attenuators.
Maybe; I can't hear that in my system.
(It most definitely occurs when impedance matching is off, tho.)
"dynamic challenges often posed by passive attenuators"
Can you think of a technical reason/explanation for why that might be happening?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Used attenuators for years.
Impedance matching but not so much the output impedance vs. input impedance but output impedance vs. the shunt capacitance that it's driving (cable, stray and Miller).
Apart from that there is no reason (that I can see) for there to be a loss of dynamics when using a passive preamp.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
for years until I finally understood that he was right.
Along with John Atkinson. :)
.
Have Fun and Enjoy the Music
"Still Working the Problem"
A truly good active will be superior.
Put all components (Source, preamp, amp) in the same pretty box and you have eliminated the visual concept of a separate "passive" component.
As an audio system, you are left with either good engineering or poor engineering.
A resistive/autoformer/transformer volume control individually is a "passive" attenuation element that is employed in every single audio system. Some people do not know how to create a good system out of various components That is why the hobby has good sounds and poor ones.
Just like the old 2 stage vs. 3 stage single ended amp debate.
A 2 stage amp with a one stage preamp is a 3 stage amp. It doesn't matter which box that third stage is in.
All preamps that I know of use a passive pot somewhere. It boils down to how much total capacitance the pot has to drive. In an active preamp there is only a short wire run to the amplifying device. In a passive preamp that cable run needs to reach the power amp.
A active preamp can be made to have a very low output impedance that keeps the cable capacitance (and stray and Miller) from being a problem. With a passive preamp all of these things need to be thought of and solved.
As long as that is successfully done, there should be no loss in dynamics (or highs).
A 10k pot has a worse case output impedance of 2500 ohms. That is at the -6db position, all other positions yield a lower output impedance.
2500 ohms against 320pF gives a -3db point of the low pass filter of about 200kHz. That will make 20kHz completely untouched by the filter. If the shunt capacitance is higher than that, then the phase at 20kHz will start to shift.
2500 ohms driving 1500pF will cause a -3db point of about 40kHz and 20kHz will be 1db down. I'm not sure how many of us old guys would hear that but I don't know for sure. To be safe I keep all the filters, that I have control over, at or above 200kHz.
I use a old school 25k Daven stepped pot so its worse case output impedance is 6.25K but my cables are only 3 feet long and very very low capacitance (about 45pF total) and the input tube I use in my amp has the lowest Miller capacitance I have ever seen in a triode. About 40pF. 6.25k ohms driving 85pF gives a -3db point of the filter about 300kHZ. So that filter has no effect at all on 20kHz.
In some cases a passive might very well "rob dynamics" but if the system as a whole is designed right that will not be the case. Unless there is another mechanism causing it but so far no one has come up with one.
Maybe active preamp stages act as "dynamic expanders" and a passive preamp doesn't? :-)
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
is this approach using DACT attenuators between source and power amp:
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It is, however, more transparent than some preamplifiers employing SS or tube gain stages.
Wow, what a waste of Earth's precious resources. Helping to destroy the planet one box at a time. ;)
Here's a simpler (and cheaper) approach:
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*********
We are inclusive and diverse, but dissent will not be tolerated.
and leftover Audio Research knobs that cost more than everything else! Ones with fixed values are pretty much useless for playing music.
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Just didn't sound as good. :)
"leftover Audio Research knobs"
Hahaha! That right there is funny.
*********
We are inclusive and diverse, but dissent will not be tolerated.
I commented on that at the time .
Can you think of a technical reason/explanation for why that might be happening?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
nor could he.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
that's all that matters. Ping JA and see if he has discovered the answer.
Ever heard of "expectation bias" ?
At the neural level, it is clear that our ability to hear is anything but objective. There is a huge component of descending control that shapes the incoming signal before it reaches the auditory cortex. We can tune our hearing quite precisely to hear what we want to hear. Much of this is done unconsciously, but the end result is that we don't hear objectively--all incoming auditory signals are colored or biased by higher brain structures before the signals reach those structures.
With no offense intended, this is a silly reply.
Yes, I am familiar with expectation bias and several other forms of bias that can influence audio experiences.
But your implicit assertion that you know what I hear has no value.
No one can answer your question without considering how you hear.
... just saying it's possible to have "expectation bias". Not just for you, though...It's possible for anyone, I think. There are ways we can get try to get around it - if you're interested.
Edits: 03/07/25
What is the output impedance of the unit in passive mode?It is most likely that the filter effects of that output impedance is causing the difference that you prefer.
Edit, That preamp has a input impedance of 10k in passive mode. I will guess that the input impedance is higher than that when the preamp is in active mode. If your sources are not happy driving a 10k load that might be what you are hearing as a difference between the two modes.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 03/07/25
Nope. Definitely not.
The source is the Schiit Yggy with a Zout low enough to not be a factor.
Also I know what impedance mismatch vs. *increase in purity* sounds like.
I'm not asserting that I am certain I can hear THD & IMD at those levels and that that is what accounts for the difference in sound. But it is something related to the active circuitry.
(There is a reason why very high-quality passive linestages, such as the Placette, have the reputation they do.)
I know what you mean. I've been using a passive preamp for years and years.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Touche!
I've had my share of passive preamps over the decades. Probably about 1/2 dozen of them. One setup was especially good but the rest were not great. Component matching is hugely critical in a passive setup and not very forgiving. The only advantage I hear in a passive is ultimate transparency but not much else. They often give up too much in other areas. For that reason, I (and others here) have come full circle and prefer active preamps.
Touche!
P.S. There is no right or wrong. Some of us build our systems based on our personal sonic preferences. I'd say most of us do. Others go for 'accuracy' - whatever that means. I for one probably wouldn't enjoy complete 'accuracy' anyway.
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Yes, component matching is critical with a passive line stage.
So is keeping interconnects short. (I use .5m.)
But matching is easy when you're all solid-state. And, when done right, there just aren't any weaknesses. IMHO.
"I for one probably wouldn't enjoy complete 'accuracy' anyway."
I am convinced that most people wouldn't.
Insert drawing from the cover of a Hi-Fi magazine from years ago depicting a guy seated in a concert hall, at a live acoustic string quartet concert, reaching for the tone control knobs on the back of the seat in front of him.
Recording engineers, who have the opportunity (on a regular basis) to make that quick trip between the studio and the control room, are maybe the only people for which the term "accuracy" has any real meaning.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
This reminds me when I was in my early teens I went with my Brother and his band to Studio West here in San Diego when it was located just off Clairemont Mesa Blvd.
I remember the Control room Engineer asking the Drummer to loosen his snare drum and do something with his bass drum. The reason I remember for him saying this and I could be wrong since it was so long ago, was his snare drum was to bright/tight (He was a funk drummer and had his snare really tight for that Pop sound most Funk drummers have) The reason was for later final mixing and it would be more easy to do. I didn't understand why at that time but years later understood the reasoning. But the Drummer and brother wear pissed cause it took away from the sound of the tune they were laying the track down. I was sitting in the control room when they were recording the tunes. I remember that 24 track Ampex tape on the reel to reel and that huge mixing board with all the DBX units. :)
We had a Ampex MM-1200 2" with no DBX. We ran Quantegy Ampex 499 Grand Master Gold tape at +6db bias at 30ips and I never felt that tape hiss was a problem.Producers/engineers don't like to be painted into a corner. They want "room to move" with regard to the sound so they can go which ever direction they want/need to in post.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 03/08/25
I dunno.... in my setup I preferred 12 dB Gain mode over 0 dB Buffered Unity Gain or 0dB Passive. That was with two Schiit preamps that I have owned including the Freya + tube preamp and the Kara solid-state preamp.I thought the Freya+ was excellent but not up there with some better tube preamps. I was hoping that the bargain priced Freya+ with 6SN7 tubes would sound similar to my old Cary SLP-05 with 6SN7 tubes but that wasn't to be. The Cary was far more robust with deep rich lower mids and excellent bass grunt. The Cary was noticeably more dynamic too. The Freya+ was 'light' in comparison..... not bad but not what I was hoping for.
Still, I preferred the Freya+ in 12dB Gain active mode over Passive. Maybe I can't hear 0.0002% THD & 0.0002% IMD
I'm driving the NAD C298 Purifi Class D amp and Tannoy Definition D500 speakers.
"Oh, by the way, Schiit's tubed version of this preamp is *Stereophile Class A,* among a sea of $30,000 wonders - and the non-tube version sounds better IMO. For $800."
But I would take my pricey old Cary SLP-05 over the Freya+ any day - but I would take the Freya+ over the ARC preamps I had. I agree 100% on the Schiit Kara. It sounds better to me than the Freya+ when comparing each in 12 dB Active vs 12 dB Active mode. I sold the Freya+ a couple years ago but I still have the Kara even though it is not in my system right now.
I guess we all hear differently.
Edits: 03/07/25
Hey Abe, I don't know if you've ever mentioned it, but why did you get rid of that Cary piece? If I'm ever in the market for a new pre, and I just might be, as I'm thinking about putting together a mono block system (at least in my post op drug addled state of mind I am) it would be one of the few I would consider. I love the 6sn7 sound. I have a Supratek Syrah with them that is currently gathering dust (no remote) since I bought my LTA integrated. LTA makes a 6sn7 (or 12sn7, never heard that tube before) piece that I would also consider. I'm a sucker for system matching, in the appearance sense as well as the functional sense.
Oh, and if you reply to this post, BE NICE! I hear you're not being nice. I might have to send a note home to your mother.
The main reason I no longer have the Cary SLP-05 and the pair of Manley Neo-Classic 250 monoblocks is because of physical size, weight, and heat. I setup a new rack at our previous home and the Cary was rather tall and wouldn't fit quite right. Similar constraints with the large Manleys.And that was BEFORE we moved to our new place and my audio system was relegated to the home office. Since finishing the basement in our new place a couple years ago I would have more than sufficient space again but I continue to enjoy a somewhat minimalist compact system.
I liked the 6SN7 sound in the Cary but it was quite different in the Schiit Freya+. But I think Cary is known for their more 'tubey' sound in general.
I'm trying to be nice by not participating much in Inmate Central. My posts are often deleted in that right-leaning echo chamber anyway ;-)
Hope you start feeling much better.
Edits: 03/07/25
Similar story here with my Supratek. Love the sound, but the two boxes took up so much room, and when I lost my space I had no place to put them. I made the mistake of putting them in my rack, too much heat swelled the wood and I ended up with a broken attenuator. Luckily I found an absolute master amp wizard (Scott Frankland of Moore, Frankland & Associates) who repaired it. I think when my space returns I'll bring it back out with my SME 20 TT. One of the best things about it was its phono stage. Lack of a remote won't matter if I have the two new knees, and have to get up to flip sides anyway.
Thanks for the good wishes. Things are improving. The downside of that is they then make you work so much harder! I'm actually spending more time at central killing time under the ice. I try and stay away from the politics though. What's the situation in Colorado these days? Daughter was accepted at Boulder. Has to be better (though not cheaper) than Alabama (another school she's been admitted to).
I almost posted a reply to our favorite person who "loves music" defending your honor, after I stopped laughing, but just couldn't be nice, so I gave up. All the trolls sound alike these days.
Nt
Sounds like your tube preamp prefs might be subjective: Which was the more *accurate*? :)
(S-file did deign to give the Freya the A rating, FWIW.)
Same thing WRT the gain setting. Also, preference wasn't the point of the post, but, rather, the ability to distinguish between the (unmeasurable distortion) passive and (incredibly small distortion) active.
I could see someone preferring the active mode.
I wasn't looking for *accurate* - whatever that is. What metrics would be used? Frequency response flatness and distortion?"....preference wasn't the point of the post, but, rather, the ability to distinguish between the (unmeasurable distortion) passive and (incredibly small distortion) active."
No, I didn't hear a difference in distortion but I wasn't trying to. I suppose I could try again but that's not how I normally listen.
I admit that I listen based on preference and to that end the difference in dynamics in Active mode vs Passive stood out to me w/o *trying* to hear it, if that makes sense. Active mode seems more 'alive' to me and that caught my attention and suited my preference.
On a related note that wasn't detailed, did you compare the Freya+ vs Kara in Passive vs Passive mode? Any difference?Or did you compare them in 12 dB Active Gain mode vs 12 dB Active Gain mode between the two preamps? In 12 dB Active Gain mode I prefer the Kara over the Freya+
When I had the Kara in my system
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Edits: 03/07/25
Well, we can certainly define "accuracy" in audio components: The least damage to the signal.
Tube preamps all produce substantial distortion, relatively small but not after subsequent amplification down the line, and transformer coupling (I don't recall if the Cary is TX-coupled) causes very substantial bandwidth-limitation and resultant phase-shift.
(The very audible effect of TX output stage of the DirectStream DAC I used to run was one of the reasons I got rid of it.)
"On a related note that wasn't detailed, did you compare the Freya+ vs Kara in Passive vs Passive mode? Any difference?"
I never compared the two side-by-side, but in passive mode the two should be identical. No gain stage in the circuit. I guess the only differences might be due to inference from the different power supplies - likely of tiny/no factor since I think Schiit knows what they're doing in that regard...
In your earlier post you mentioned how good the Freya+ is but your preference is for the Kara. How so? How did the Kara sound to you compared to the Freya+? I assume you were talking about Active vs Active modes between the two.You might enjoy Amir and the Audio Science Review website. They're all about signal measurements there.
Edits: 03/07/25
Sorry to be unclear about that but I never owned the Freya. I did hear one once and was going by that and user reports in general.
The Freya is a very good tubed linestage, as with everything Schiit does. And its measurements are very good indeed. But, I become very familiar with what tubed linestages do, over 20 year or so, and don't really desire that sound signature anymore.
You misunderstood me as believing that measurements are everything. They are something - not everything. My ears and the experience I have are the "everything."
I'm not a fan of Audio Science Review because I find the fellow who runs it (who uses a woman as his avatar) to be rather annoying, and extremely naive in some ways.
During the period in which I actively and routinely evaluated gear, I owned, in total, something like $500K worth. I've had dozens of tubed preamps, including boutique pieces from the likes of Shindo, as well as at least 30 horribly-measuring SET amps. My humble opinion now: It's all tone controls.
Ten years ago, no one knew how to measure gear at all. The worse-sounding solid-state amps "measured well" because nobody was measuring high-order THD on peaks and crossover distortion. We're past that now, mostly.
The Purifi switching amp modules are, essentially, perfect. They measure it, *and sound it.*
So, my bliss now is a top-rate digital front end, a humble passive linestage, a good Purifi amp, and electrostatic speakers.
Still, audio will always be a subjective experience. And the best-sounding room at every show (IMHO), High Water sound, is all vinyl & SETs.
Cool stuff!
I did own one Curl phonostage. Definitely he knew what he was doing.
"Ten years ago, no one knew how to measure gear at all. The worse-sounding solid-state amps "measured well" because nobody was measuring high-order THD on peaks and crossover distortion. "That's not "entirely" true. While there probably are many designers who "know about it" and can probably measure it and design around it, many don't, simply because it's more expensive and requires a higher level of design talent. But the knowledge and measurement methods have been out there for several decades.
Here are a couple of places where you can start to explore the history:
https://www.audioasylum.com/cgi/t.mpl?f=amp&m=208080
https://proaudiodesignforum.com/images/pdf/Leinonen_Otala_Curl_TIM_Measurement.pdf
John is adamant (rightly so) about high-order harmonic distortion, and has shown me some measurements on his test equipment. As a musician, I surmise that at least part of the audible issue is caused by the difference between natural harmonics and the musical scale of "equal temperament". He and I have not talked about this aspect in any depth, but we should, even if just to separate a little more chaff from the wheat, so to speak.
*********
We are inclusive and diverse, but dissent will not be tolerated.
Edits: 03/11/25 03/11/25
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