[WGH]

I like getting the best performance out of my system for as little money as possible which is one reason I own AVA electronics. The Insight+ DAC has been superseded by the new Vision DAC which I haven't heard yet, but the attenuator tweak is keeping me happy and toes tapping.

The System
Toshiba laptop --> Windows Vista 64 bit --> Foobar2000 v0.9.6.7  --> .wav files --> WASAPI --> 15' Monoprice USB cable --> HagUSB --> 16' Belden 1694A from Blue Jeans Cable --> Insight+ DAC --> Insight+ EC pre-amp --> Insight+ 440 double --> Von Schweikert VR-2.

The Tweak
I have been following the Reflections and Attenuators thread in the Lab and Pat's measurements are very interesting. An in-line attenuator reduces reflections so your DAC sees less jitter. There are also anecdotal reports of better sound by using attenuation with the HiFace MK2 and a short review of a modded SB3 by kyrill. I had a 6dB attenuator laying around from another project so I decided to plug it in between the DAC and S/PDIF cable to see what would happen.




The Results
At first listen it seemed like nothing changed, the DAC easily locked on the signal and music played as before. The attenuator can be quickly taken out and put in while music is playing for A-B comparisons which is how the changes were easily heard. The biggest change is more solidity and focus to the sound stage, center images have a new roundness and low level information is easier to hear. Another big change is the music has less of a digital edge, the music is easier to listen to which also means it can be played louder without fatigue. Sibilants are controlled and the music now flows effortlessly.

I'm sure different USB-S/PDIF converters and cable will yield different results but this tweak is so cheap and easy there is no reason not to try it, you might be pleasantly surprised.

Wayne

[rajacat]

Where did you purchase that particular attenuator?

Thanks,

Roy

[Tone Depth]

I imagine some DAC chipsets or their implementation in the circuit may be more sensitive to jitter from signal reflections at the input than other DACs?  Interesting investigation, and that you are getting results that seem to confirm the effect.

[2gumby2]

I'd be interested in Frank Van Alstine's opinion on this.

[werd]

Wayne

How long is your spdif cable you are using the attenuator with?

[WGH]

Unfortunately I don't remember where that I bought that attenuator, Radio Shack is usually my go to place for parts but I didn't see this model in their catalog. I doubt I spent $35 for it, probably more like $5-$10.

My laptop lives in my office, 25' from the stereo so I use long USB and S/PDIF cables with the HagUSB in the middle. My S/PDIF is 16'. Pat has always advocated for long S/PDIF cables, they just measure better. It has to do with the timing of reflections and how they interact with the DAC. Do long cables sound better? That is up to you, he just measures - but he is very good at it.

If you stop and think about all the other tweaks and tricks you guys try, how many of them yield radically obvious changes, that can be measured on any multimeter?

Of course, if you don't believe in tweaks, and have no interest in trying any, then why are you reading this?!

Pat

[WGH]

I imagine some DAC chipsets or their implementation in the circuit may be more sensitive to jitter from signal reflections at the input than other DACs?  Interesting investigation, and that you are getting results that seem to confirm the effect.

It will be interesting to see if the new Wolfson 8742 digital chip set in the Vision DAC benefits from any attenuation.

Wayne

[rlee8394]

Hmmm... from the photo, that looks like an RF attenuator by virtue of the DC PASS THROUGH label. This would imply that there is no attenuation since the path from source to DAC input is a DC path. Try an attenuator without a DC PASS THROUGH and report back.

Ron

[WGH]

Good catch Ron. I have also seen attenuators with DC blocking, is that good or bad?

Is DC pass through just in one direction, so even though (if) there is no attenuation the reflections are reduced? I'm winging it here, throwing out the rule book and playing around.

The doohickey certainly does something good, I might be able to do a blind test in a week to make sure I'm not delusional.

Wayne

[WGH]

Hmmm... from the photo, that looks like an RF attenuator...

That is EXACTLY what we are looking for (you gotta follow the links folks, that is why I include them).

John Keny is the respected modifier of the HiFace MK2, he explains what is happening much better than I can:
"What you are hearing with these RF attenuators is a reduction in reflections ( & hence jitter). These reflections only occur in high speed signal transmissions (in the MHz/GHz range ) & will not be seen in the slower analogue signals. Therefore the RF attenuators have no significance to analogue RCA cables.

To try to explain, consider the MHz signal like a wave in water. If this wave meets a rock sticking up out of the water reflections will be created. Many rocks, many different reflections! These rocks are the equivalence of impedance anomalies that are found in real world digital systems. The faster the signal the more reflections arise. The Hiface produces fast SPDIF signals. Fast signals are a benefit for digital - it makes for a better, more accurate signal.

So what you are hearing with the attenuators is a reduction of jitter which I believe is proof positive of the sonic effect of jitter. You know people question/argue about jitter & what level is audible & indeed if it has any effect on audio. These attenuators answer that question."

I will be ordering some 75 Ohm, 3 to 20 dB, DC to 2000 MHz attenuators from Mini-Circuits to see what difference they make, they are only $12 each. Unfortunate I will have to use some BNC-RCA adapters which screws up the 75 ohms but it's the best I can do with the connections I have.
http://www.minicircuits.com/products/attenuators_coax_fixed.html

Wayne

[jkeny]

Hi Wayne,
Just wanted to say that there are a number of reports from end-users in using these RF attenuators already posted on this forum (not just usage on the Hiface) http://www.audiocircle.com/index.php?topic=72468.msg815751#msg815751

As regards the quote above, you should go to Pat's thread for a more technically correct explanation form an RF expert - this one has a few mistakes in it.

[WGH]

Thanks for the link, I read all of Pat's threads even though I can understand only parts of them so I wouldn't know where your mistakes are.   

My listening experience mirrors the remarks in other threads but I formed my opinion before I read any reviews. I read the attenuators reduced jitter but I didn't know what to expect sound wise.

I just received some 75 ohm attenuators from minicircuits but the adapters are still in-transit. I plan to use some and loan out others. Maybe an attenuator tour - we'll see.

Wayne

[WGH]

The "official" 75 ohm attenuators have arrived and they sound as good if not a little better than my no-name attenuator.



I bought a 5 pack to try out different configurations, the goal is to maximize attenuation without loosing the signal. Right now I am running a 10 dB on my main system and a 6 dB on my shop DAC. I tried a 6 dB on each end and 12 dB was too much, no signal got through.



I have 3  2 - 6 dB attenuators along with the 75 ohm BNC to RCA adapters left over so I selling them as a kit.



The price is $20.50 for each kit + $2.00 postage, buy one or all - here is the link:
SOLD OUT - Link removed

Wayne

edit: 0 left

[rajacat]

Will you sell just the 6db attenuator? I have a 20' Blue Jeans BNC cable.

-Roy

[WGH]

I'm going to keep the kits together and see how it goes.

Wayne

[festuss]

  Sounds like mind games.  Of course it improved something, don't they always?  Funny stuff.  What if you put 2 in series, I bet you would get 2X the improvement, based on current thinking.

[WGH]

Hey festuss - I did try 2 attenuators in series with one at each end of the spdif cable and the change in sound was even more dramatic than a single attenuator. The difference was easily picked out in an A-B test that even non-audiophiles could hear, with 2 attenuators the music has a blacker background, and a blacker foreground because no signal got through.

Wayne

[jkeny]

Yes Wayne, that is 2X improvement - cutting down noise by that much, wow - I'm impressed 

Even an uninformed  naysayer like Festuss would be able to hear this or maybe he would say it was placebo effect  ?

[festuss]

  You need better equipment if it all full of noise, my stuff is silent, with zero tweaks, or mystical plug in.  Have you measured what is really being changed, 6dB attenuation of WHAT?  What if they put the wrong stickers on these BNC connectors, and called em 10dB.  Why is the output of your players so faulty with noise that is audible?  I remain clueless, but only on how this stuff is for real, let alone actually improving the imaginary sounds you are hearing.  Sometimes reality isn't as much fun as imaginary BS.  Try understanding electronics, and you might save a few dollars.

[jkeny]

Oh please Festuss, you really are clueless about all this. The best thing you can do is take your own advice and "Try understanding electronics" - it would prevent you putting your foot in it. You don't even understand the humour in the last 2 posts - as you say yourself "I remain clueless" - try to do something about this before posting again.