[71 dB]

Scientific literacy isn't neccessary, most people are fine without it. Claiming otherwise is just some kind of reflexive elitism.

No, most people are not fine without it. The lack of scientific literacy is a real problem. How much is it to require people to be able to read simple log-log graphs? That's why we have schools for. Not being a moron is hardly elitism.

 

[tansand]

So people who can't read a log-log graph are morons. You're getting a little exited, aren't you"?

 

[Reggy]

just use a 10K balanced passive attenuator. otherwise by a passive monitor controller. There won't be any loss, because the dac is not driving into a lower impedance load that would cause lack of bass response. btw the thread you are referring to is for an unbalanced circuit. The two types that are used are the PI atternuator ( also called "o" attenuator), and "T" type. Typically T-types are used for adjustable attenuators. The monitors are 10K on the input. That is why it states 10K. Also, you have to understand a couple of things about the output stages, the output impedance is the smallest impedance that will guarantee the specifications. Its always better to find the optimal load, on tl071, tl074, types 10K seems to be the optimal load and the norm in electrically balanced systems, but this is not a fixed point somewhere as 2K-10K is the final resulting impedance in an balanced chain (in your system, the terminating resistance on the output of the dac in parallel to the input of the genlecs that we put in parallel an attenuator). I've seen zillions of times interconnecting different pro gear, 600 ohms is the norm for transformer balanced systems this impedance interconnect is a fixed point. Btw, I wire radio stations, pa systems, and pro recording studios for the past 20 years. yes there are other impedances, but 10K is not going to cause the tl071 to pull excessive current and cause white noise, low impedance will. There's maybe 35 different studio setups I've done and about half of them have a 10K attenuators because of these powered monitors. I've hooked up your model before this way, along with Yamaha hs80, Neumann KH80... etc, all of those self powers are like this. So if I go by the 10X rule, the terminating resistance is 12.5K on the dac's output, then 10K is parallel, to another 10K and if we do the parallel formula, we get 3.57K as our ending impedance.

Just giving you some professional advice, recommendations, and a little bit of whats going on in the background for you....

edit: here is some light reading on the subject:
http://www.radio-electronics.com/in...n/attenuators/balanced-rf-attenuator-pads.php

and

https://en.wikipedia.org/wiki/Attenuator_(electronics)

Unless you want to build one out of some high end resistors (like z-foil resistors), a standard, off the shelf 10k attenuator is going to work.

Thanks for chiming in, it's nice to see someone like you have a bit of experience in the industry and give a break down of what's going on.

Using

I see where you get 3.57K, I am just curious to why you 10X the DAC input impedance of 1.25 kOHms. Is it to provide a safety factor to ensure the DAC is not driving into a lower impedance? I guess I just answered my own question as with that I get a 2.8 ratio for the load/source which is above unity.

I will be looking into my options now for passive pre-amps, considering Luminous audio as an end game result as the variable shunt design seems to avoid the signal flowing though the volume pot, I like the idea of a switching network as well.

Funny enough though of doing research I have entered the realm of TVC (Transformer Volume Control) here is a synapse. http://jandkaudiodesign.blogspot.com/2016/10/transformer-volume-control-tvc.html

The quote I found here seemed to scream gold with my setup, that is of course assuming that impedance matching is still an issue:

"Transformer based volume controls are like a passive volume control.. unlike an active pre, they have no gain stage but only attenuate the volume. The transformer acts like an impedance buffer, reducing the impedance mismatch problems associated with resistor based passives, but driving the input stage of the power amp falls by and large on the source.
This reduces the circuit complexity which is associated with active preamps, but if the power amp has a low sensitivity then the lack of gain on the pre will cause problems.

A power amp with decent enough input sensitivity, preferably below 1v, better if near or below .5v, and a source with an output voltage above 2v, higher the better."

My Genelec goes below 0.4V for input sensitivity while my DAC outputs 4 Volts so this seems to be a match.

There is surprisingly a lot of talk here https://forum.audiogon.com/discussions/tvc-vs-active-pre with TVCs, one caveat is the lower volume the better the sound is as the dynamics and bass are better retained unlike passive or even active preamps which suffer at lower volumes and the frequencies don't seem to be repressed.

https://mfaudio.co.uk/preamplifiers/ is also a popular type of TVCs but the prices are absolutely outrageous for the intended purpose.

I would be hoping to go down the Bent TVC route however it seems strictly DIY which I don't have the patience to learn and risk.

 

[71 dB]

So people who can't read a log-log graph are morons. You're getting a little exited, aren't you"?

Some of them are because morons walk among us, but the relevant thing here is you can't absorb information presented in log-log graphs if you can't read them. Since it doesn't take much effort for a person with normal intelligence to learn log-log graphs, why not teach them so people can read them and understand a larger percentage of the information presented to them? It's your own benefit if you can understand graphs. What's the point of resisting? You definitely are a moron if you want to be one.

 

[tansand]

Lol, sure thing man. You have fun with that.

 

[Reggy]

Anybody like TVCs?

 

[tansand]

Never used one, there is quite a bit of hype and they're expensive. They limit bandwidth, which you may want or not. I made some shunt type passive preamps and they sound great. It didn't cost a lot, so it seems like a lot of money for a tvc. As purist as you may want to get, you're still going into a powered monitor full of opamps.

 

[Reggy]

Never used one, there is quite a bit of hype and they're expensive. They limit bandwidth, which you may want or not. I made some shunt type passive preamps and they sound great. It didn't cost a lot, so it seems like a lot of money for a tvc. As purist as you may want to get, you're still going into a powered monitor full of opamps.

True, as much as I would like to praise the Genelec's they are not passive and contain it's own circuitry. I guess I'm not looking to go the purist route sort of speak, I'm just open to TVCs as I've heard they can get the job right without shaving off the information and dynamics, particularly in at low volumes. And yes there is some dangerous hype I'm trying to sniff through to see if it's the real deal. More of along the lines of solving potential problems with dynamics and impedance matching issues which sold me. And again, it looks like the sub $200 pre-amps I've researched have had problems controlling the stereo image. So I have to either try and accept the cheap ones, or continue to open up my wallet to ~$500-$1000 praised ones. At least I've decided on Mogami Gold cables so I have one more item to go now.

 

[Sonic Defender]

I'm all about audibility, as I'm sure the vast majority of people in this community are. I enjoy objective information, even if at times I find it higher level than my knowledge base permits me to fully understand. What I do know is that measureable may not be audible and that is what I often get the sense people are concerned with. I'm not talking about obvious poorly designed circuits, or egregious impedance mismatching, but many of these measurement parameters can have measureable/theoretical implications within circuits, but if they are below the level of audibility in terms of audio being decoded by your brain (the most import system in all of this) then the exercise becomes an academic one. I am not at all saying there is no value in engineers continuing to push design and performance parameters, but our hearing brain is certainly limited, and as we age it becomes progressively more so (individual differences aside).

I have always felt that when you read technical explanations of how factor A is part of an audio signal, we can get lost in the technical language and overly focus on such things and under-emphasize the fact that we really aren't capable of discerning rather minute differences in audio signals in real world listening situations. When you are listening to music with properly designed playback gear, tiny, even if measureable differences are just not going to be audible. Our brain is pretty impressive, but it is still the limiting factor and as wonderful as it is, it is rather limited. Can people really detect miniscule levels of distortion in their music? I'm not talking about clearly audible distortion of course, there is a threshold of audibility to consider, but beyond that, does much of this matter?

 

[tansand]

And again, it looks like the sub $200 pre-amps I've researched have had problems controlling the stereo image.

If you're referring to channel imbalance, you're right that can be a problem. I specifically chose some vintage carbon pots and selected them for minimum channel imbalance. I think about 20% were within 1db over the range. The Alps Blue RK27 pots like in the luminous axiom should be the minimum you look for if this is a big concern. I tested 6 of those, all were within 1db. This issue is not confined to passives, but everything that has a volume control..

Stepped attenuators are even more accurate, of course. One of the things to remember about stepped controls is the steps are coarse, 3db is a lot. I think the ability to set volume very precisely is really important for subjective sound quality, particularly when the speakers are right in your face/ears. There's also the Freya still.

 

[tansand]

-tested 4 of those actually.

 

[bigshot]

Can people really detect miniscule levels of distortion in their music?

The problem with audiophiles is that they are so fascinated with gear and electronic theory, they spend all their time researching that. They spend no time researching the thresholds of human perception. Without a general baseline for what is audible and what isn't, all those numbers and theories have no practical application. In extreme cases of audiophilia nervosa, people may be so intent on protecting the value of their theoretical research, they try to cherry pick studies out of context to come up with evidence that inaudible is inaudible. A good example of that is when people try to defend the necessity of super audible frequencies by pointing to brain scans. You can't consciously hear those frequencies. It's been proven that they add absolutely nothing to the perceived sound quality of music. But because a brain scan registers a blip on the chart, suddenly those inaudible sounds become more important to them than audible frequencies.

If everyone just bought stereos to satisfy their ability to hear and nothing more, a great deal of money would be saved and a whole lot of high end snake oil would be forced out of business. Also everyone would be happy with the way their stereo system sounds! But I suppose if they didn't have audio to worry about, they'd start obsessing on the number of megapixels in their camera or whether they locked the front door when they left for work in the morning. OCD is a driving force in high end audio.

 

[tansand]

I think a lot of the confusion on your part is that you simply can't hear the differences, bigshot. The above post is precisely the reaction one would expect from you if that were the case. Maybe just have a bowl of soup or something.

 

[tansand]

For instance, I've been switching back and forth a couple different interconnects between my dap and amp. These are about 1 and 3 inches long, respectively. One I've found sounds brighter than the other, that is with it plugged in eventually I get irritated it's a bit bright. On another amp that has less high frequency extension, I liked this cable better, the other was too dark.

Is somebody going to tell me there's no difference, that all cables sound the same?

 

[Reggy]

For instance, I've been switching back and forth a couple different interconnects between my dap and amp. These are about 1 and 3 inches long, respectively. One I've found sounds brighter than the other, that is with it plugged in eventually I get irritated it's a bit bright. On another amp that has less high frequency extension, I liked this cable better, the other was too dark.

Is somebody going to tell me there's no difference, that all cables sound the same?

I've never heard such short interconnects as being 1 and 3 inches, again I'm new here. I suppose from electronics theory at those lengths there could be something at play given the short lengths. I would have to do my research but perhaps at a particular number of wavelengths one length of cable is acting as a high pass filter by itself? Of course that could not be not what's happening, it could be that the integrity of the cables at such a short length is weakened, obviously you must be using something other than XLR for one inch. Maybe at greater lengths (2ft or more) the apparent quality of the cable stays the same. Again, you would have to elaborate on the type of cable you are using before someone can draw a useful conclusion on why that is happening.