Passive Volume Control for DACs/Sources

Hard to tell, no specs really on the site. I use Cordial CMK 222: https://www.cordial-cables.com/en/products/cmk-222 - at 55 pF/m it works well and is not expensive, just a solid cable.

 

Hi,

I only found this:

https://www.tnt-audio.com/clinica/jps2e.html

different cable. If we assume 80 pF capacitance per m and assume the cable is 2.5 m long and the input impedance of the monitors is 20 kOhm and the output impedance also 20 kOhm, then the corner frequency is 79,6 kHz. 80 pF per meter isn’t bad, what bugs me is that the fancier the cable the less data you get it seems. Maybe JPS Labs are willing to let the public know the data of their cable. I do not buy cables anymore if I do not know their capacitance and resistivity.

 

I use Gotham, they have full test specs for the raw cable.

Eg: http://gothamcable.com/en/gothamcables/unbalancedcable/10012gac1ultrapro

 

My desk setup includes a balanced cable run of about 30 feet from my Hattor passive to my Genelec 8040Bs. There's a goldpoint in the path as well to give me Off\On capability for the speakers only.

While I was building my TT and speaker setup (which also includes passives in the chain) I figured out RCA cable capacitance was important and affected the sound quite a bit. So back on the desktop side I changed from "Amazon Basics" whatever XLRs to Blue Jeans Cable customs with Beldon 1800F. Did it make a difference? I like to think so but I wouldn't volunteer for a blind listening test.

On any account the 1800F is nice cable and can be purchased bulk from RawCable if you like to roll your own.

 

how do you avoid having a nervous breakdown

 

I come close to it on a daily basis but not over audio equipment.

Does my approach reek of nervosa or something?

 

no the opposite! Very practical. I was just kidding too. I think it’s absurd this subject isn’t audio 101 and is requiring equations to figure out. Which makes me get the willlies.

 

I agree it should be audio 101. It's probably because it requires some knowledge of what the source/amp impedances are, cable capacitance, etc that people say: just use short cables. Yes, that's safe, but it's restrictive and not a very satisfying answer.

 

Deep thought on cables can quickly dissolve into 'snake oil' territory because most of us aren't electrical engineers familiar with the concepts: We don't have a frame of reference for evaluating the importance of various factors and peoples' claims about them.

Main things I know about RCA interconnects are 1) you want quality (vendor tested) cable with low impedance and high shielding, and 2) companies who sell expensive-ass interconnects don't want to divulge their specs on those measurements. Because of that I have a really hard time justifying 'high-end' cables, it just rubs me the wrong way.

Blue Jeans Cable LC-1 is the best fit I've found in RCA interconnects but its a PITA to work with when building homemade cables. I bought a bunch of Belden 1505F and have been using that to build non-balanced interconnects.

 

According to atomicbob’s post Belden 1800F is 120 pF for a cable 10’ long. I do not know the output impedance of your (@rhythmdevils) passive pre, but if you are suffering nervosa, just order a ready made 10’ cable from Blue Jeans cables and compare it to the JPS Labs. Don’t hear any difference send the Blue Jeans back. Blue Jeans sounds significantly better, it is a keeper and the JPS surplus to requirements. Still a lot cheaper than getting rid of your passive and buying an active.
Bye the way I am happy that someone else came to the same conclusion like me, a passive pre is the natural way to go with active speakers.

 

Great post! This should be better with autoformers, I guess, which are not voltage dividers?

 

You can find the relevant calculations here:

http://www.promitheusaudio.com/tvcfaq.htm

 

There is one new Slagleformer autoformer for sale now: http://www.intactaudio.com/atten.html
At the page bottom, $400 with 28 steps instead of 14 steps. Any insight on how good they are? How hard to work with? Is it easy to damage while soldering? Is it even worth having 28 steps instead of 14? I'm contemplating a DIY project, having just basic soldering skills. If I engage, I will post pics.

 

@androxylo
I have not heard a slagle autoformer myself, but I have friends who have who really liked them. I have had a TVC in the past that I really liked. AVC's in theory have more linear performance than TVC, at the expense of not offering isolation.

I would consider 14 steps far too low for volume control, but 28 sounds good.

Soldering as always requires a hot tip and plenty of flux. In particular here as the pins on the autoformer are a bit thicker than your typical leads and wires. I would use a chisel tip which tends to hold heat a bit better and turn the dial on my soldering iron up a notch or two from my usual. If you really want to go the extra step, use some sandpaper to lightly sand the pins then flux and tin them ahead of time.

 

I currently use a slagleformer - the one with 14 wide steps, and then three finer adjustments (+\- 1.25 dB or 0 dB) - and I love it. Have it in front of a Decware Zen triode, fed by a Schiit Bifrost 2. I wired it up with two outputs, so it also feeds a subwoofer.

I’ve made a few changes here and there with the Slagleformer, and every time, I want to blame it first, on to later find it was something else (usually a tube going) making the problem. The Slagleformer is transparent, dynamic and just straight up fun in my system. Can’t go wrong with any of them. With the Decware, I really like it over the Schiit Freya + I also have, regardless of which active/buffer/passive setting the Freya is on.

 

Probably offtopic, but every passive DIY project requires some wires. It looks like when there is a lot of switching it should be at least 15+ ft of wires. I have few feet of Duelund silver wire but I'm still many feet short. Which wire you use for DIY with well under $10/ft cost?

 

Just saw this on Amazon. Looks like a knock-off of the Nanopatch, except with the addition of a mono/stereo button. Too bad it's white.
https://www.amazon.com/DYNASTY-PROAUDIO-Controller-Extremely-Adjustments/dp/B08HPPXZLH
https://dynastyproaudio.com/products/pmc-1-premium-passive-stereo-monitor-volume-controller

Anyone know anything about it?

 

@gixxerwimp Thanks for pointing out this JBL Nano Patch+ knockoff. I purchased a Nano Patch+ about 6 months ago from Amazon but returned it shortly thereafter bc it had horrible channel imbalance until about 3 o' clock (and, unfortunately, it seems as though it's been discontinued, so I couldn't get a replacement).

I ended up purchasing the Dynasty ProAudio product you mentioned for the Vanatoo T0's I have on my desk (unbalanced mini-jack for input & output). It does the job. A few differences between the Dynasty product & the Nano Patch+:
- Dynasty has a Stereo/Mono switch, which I don't care about
- It's harder to read the volume position on the Dynasty due to the color & location of where there marker line is on the knob. The line on the Dynasty is an unpainted line (similar to the line on a small silver Schiit knob) on the lower/outer part of the knob, while the Nanopatch has a painted white line on the top of the black knob. All in all, this doesn't really bother me bc I don't look at the actual position of the knob when adjusting it.
- The Dynasty is white & silver while Nano Patch+ is black & red
- The Dynasty has stick-on feet; I think the feet were already attached on the Nano Patch?

and, there may be a difference in the resistance when turning the volume knob; I can't really remember the Nano Patch due to how long it's been & how briefly I had it... but, there's not much resistance on the Dynasty. Normally, this would bother me, but due to the size of the knob, it's fine.

Overall, I'm happy with my purchase. I paid $57 for my Dynasty, and the Nano Patch+ costed $59, so no big difference in price.

 

Glad it worked out for you. I was surprised to hear you had imbalance problems with your Patch+. Maybe it was a knock-off

I checked with Thomann last October and they still had lots of stock. But I guess it's really discontinued now.
https://www.thomann.de/intl/jbl_nano_patch_plus.htm

 

Image: https://pasteboard.co/MoZgGXuyXXeQ.jpg

I've replaced my Shchiit Sys with unfinished Slagle Autoformer. That's the basic Cu one, but prewired with 23 steps. The build is very solid and sturdy, all wires are tidy. I used Dunelund silver wire and high silver flux. Some $15 connectors from partsconnection.

Now my chain is ViewSonic monitor USB from MacBook (actually sounds better than using MacBook USB itself) -> Schiit Modius -> basic Slagle autoformer -> Schiit Aegir -> Dynaudio Emit M10.

The Sys was clearly a bottleneck in my system. The improvement is not staggering but clearly audible from the 1st second of listening. What changed: more details (plankton), better instrument separation, black silence between notes. I also found some occasional touches of very deep bass that my bookshelf Dynaudio was totally lacking before.

I think more experienced people should try Slagle and put the bottom line here - my humble opinion is that pots are dead. There could be a lot of advanced solutions but the $200 autoformer + $30 switch must destroy any pot for that much price. I've paid $425 for prewired version but it's still the same $200 autoformer. People say silver autoformer is better, but it's out of my price range.

I think now the bottleneck of my system is $200 Modius, eventually I will replace it with true Multibit. But I'm very happy with sound like it is. I would love to visit a store in NJ to audition something expensive to find out what is my gap to more expensive rigs.