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| Model: | 139L Filter Choke |
| Category: | Power Conditioner/Surge Protector |
| Suggested Retail Price: | 36 |
| Description: | DC choke filter, plugged into AC circuit with gear. |
| Manufacturer URL: | Not Available |
| Review by The Killer Piglet (A) on May 15, 2006 at 19:15:31 IP Address: 65.6.174.198 | Add Your Review for the 139L Filter Choke |
This is a story about a Hammond 139L choke; I first saw this mentioned here:http://www.audiocircle.com/circles/viewtopic.php?t=10310&sid=1ceed1b96ce8d99fec4816a36ff4a7d5
I had put this out of mind when I first read it, but it was brought to the fore again when it popped up on AA.
These are my impressions, take them for what they are worth (try printing them, take the printout to a 7-11, and see if you can a stick of gum).
The setup was a bit of a jury rig, just plugged regular PC's into the outlet, then dropped the terminals of the choke into. Not very permanent, or elegant, but I wanted to see if it worked before I went through any more trouble, and my DIY skill rivalling those of the marmoset. Parenthetically I would welcome any suggestion on making this into a more permanent and far safer device.
Short answer: yes. It works.
When I first installed the Hammond, there was no change in the sound. After letting it play for 10-15 minutes and then removing it, the change was obvious, as soon as the unit was unplugged. The Hammond was right next to the speaker, so the drop off in bass was easy to detect from that position - on tracks that had very deep bass.
I found the best way to test it was to let it stay plugged in for a few minutes, then listen. Unplug, listen again.
As my patience is limited for this sort of stuff, I did it maybe 6 times on each outlet over the course of the day.
My set up is (see system link for more details, heres the elctrical side):
20 amp circuit for the Rogue M150's (I do have another 20 amp line there, but it's not been terminated, so they both share a line at the moment - note to self: brow-beat brother in law into completing lines).
20 amp for BPT 2, with some add-ons like Bybees. No idea if the Bybees help it, that's how I got the unit, but since they are considered filter I figured they should be mentioned. PS Audio 300 Power Plant plugged into that.
Modded Sony transport plugged into PS300; PS Audio high current UO fed by PS 300; Audio Note 3.1x Balanced DAC and Rogue 99 Magnum pre with beefed up caps into UO.
Room treated with Argent Room Lens and GIK 244 & Super Bass traps.
I tired the Hammond in the outlet for the amps, an outlet on the BTP, and an outlet on the PS300.
I have not changed any gear 2 years, generally being happy with the sound while continuing to improve on with tube rolling and room treatments.
Mostly, I was playing Chachao, Master Sessions I, Master Sessions II, and Cuba Linda.
The results were similar in all cases.
- the first an most obvious change is in the bass; clearer and most of all noticeably deeper and with greater texture. If you have the Cachao Cuba Linda CD, the first 45 seconds of track 6 highlight the changes in the bass.
- highs are smoother, and more extended. there's a greater sense of I would imagine is generally referred to as "air."
- overall presentation is slightly clearer, and the soundstage is slightly more defined, with fairly more depth and height, while the images are a tad more forward. It's very difficult to quantify these judgments, what does "slight but noticeable" work out to? Let's say 3-5%?
- if you are considering buying a power cord or even a line conditioner, try this first.
Addendum:
I wrote the above yesterday, and re-read it today. I am wary of slipping into the sate the hyperventilation that seems to go hand in hand with so much of audio commentary, where small changes are often inflated to events of Biblical proportions. I was glad to see I didn't, becuase, well, it's not exactly like a plague of locust. I also wanted to try it again.
Oh, back to trying it again. Yes, I did hear pretty much what I heard the first time, except this time what I appreciate the most is the added weight and space to the sound, without any downside witch sometimes accompanies changes that improve said attributes (such as rolled off highs, loss of dynamics and detail, too much warmth).
So, this tweak or project does provide a small improvement. Not as substantial as good tube change, but on the other hand it will just sit there and sound better when you do make that tube change, etc. Maybe best of all, this is the first power add-on that has not taken away anything from the amps.
It's not shiny, nor made from exotic panda bear kidney stones. You can all to clearly see what it is: it's not wrapped in a sealed box and embedded in tar.
Zero, possibly negative, cachet. But a lot of function.
Somehow, this escalated into a very wordy post on a very cheap item. Maybe you can hold out for two sticks of gum? Throw in some cash, and I think you can.
KP
| Product Weakness: | Not UL listed; made for DC |
| Product Strengths: | Effective all around |
| Associated Equipment for this Review: | |
| Amplifier: | see review/system link |
| Preamplifier (or None if Integrated): | see review/system link |
| Sources (CDP/Turntable): | see review/system link |
| Speakers: | see review/system link |
| Cables/Interconnects: | see review/system link |
| Music Used (Genre/Selections): | see review/system link |
| Room Comments/Treatments: | see review/system link |
| Time Period/Length of Audition: | 3 days |
| Type of Audition/Review: | Product Owner |
Follow Ups:
Killer Piglet et al. --I got curious about this choke tweak and conversed with Al Sekela about it. In the process (and asking my usual frugal question about alternatives) Al clued me into what a choke is and how it is related to other coiled electrical devices. He speculated that you could mock up something with similar impact to the more expensive chokes with any large enough transformer. He suggested that simply capping off the secondaries, so that there was no load, and plugging in the tranny via the primaries might do the same filtering as a choke.
Well, I happened to have a spare EI tranny around of what seemed like minimally suitable size, so decided to try it. Simply wired into the primaries a cut off PC and taped off the secondaries. Plugged it into my power strip with the rest of the gear (except the CDP, which is in the same circuit but separated at the wall outlet.)
It works! Tranny warms up and the clarity improves. On CDs it seems to bring vocals slightly forward which I like, separates vocalists and stringed intruments quite well, and the piano sounds more detailed like a bunch of strings in harmony (not just one mixed chord). Even some better HF detail, especially on FM. Gave a better sense of air/separation/spaciousness, particularly with HDCD discs. It's noticable, above subtle, but not intrusive. And nothing else was lost (not dynamics nor range). Like it so far.
So I'm going to experiment some more.
As always, YMMV and ELECTRICTY CAN KILL - WATCH YOUR ASS AND THAT OF YOUR NEIGHBOR....
Correct....I would have picked the donut, but EI's are fine.Alan
KP
The Hammond chokes are specialty items made for B+ supply filters in a limited range of tube amp designs, so they are only sold by a few places. As you've found, they are expensive and the shipping costs are substantial.Power transformers are easy to find cheap in surplus shops, especially the ones that have odd or unknown secondary windings. As long as the primary was designed for 120-volt service or higher, it will function similar to a choke. You take the chance that the particular unit will not have an annoying buzz.
After Bartc and I communicated, I dug out a pair of Stancor NOS filament transformers I have. These are rated for 20 amperes at 6.3 volts, and the primary DC resistance on them is only 2.5 ohms. The primaries exhibit the equivalent reactance to 2.75 Henry chokes. This is smaller inductance and resistance than the Hammond 193H chokes I reported below.
I attached junk line cords to them and compared them to the Hammond chokes. They produce more relaxation in the midrange and a slight improvement in the treble, compared to the chokes. Remember that I'm using smaller chokes than those Alan recommended, so I won't say the transformers are superior to the 193L chokes.
For safety it is very important that the secondary leads be individually insulated so there is no possibility of a short. The chokes are safer in this regard, as there are no secondary leads.
KP
I found that I have a pair of Hammond 193H chokes acquired for another project. These are 200 mA instead of 300 mA, but are the same inductance (5 H). The DC resistance is 65 ohms instead of 57 ohms.I wired these up with junk cords and plugged them in to the circuits feeding my Atma-Sphere MA-1 monoblocks. There was an immediate improvement in the midrange. It became easier to hear the separate piano strings in the decay of notes on Shirley Horn's _You Won't Forget Me_.
There was little or no effect on the high treble. I tried adding Power Wraps to the cords but am not sure this made any difference. My system is already very clean.
Thanks to Alan for posting this tweak.
I was very sorry to see the thread at AC get insulting to Alan; if it hadn't been form his mentioning the tweak here I would have never had the impetus to actually try it.And thanks to you for the follow up as well. I ordered a couple more.
KP
If so , are the effects additive ? I've read of some of the Power station crew adding three or so of these to their stereos .Oh by the way , they are connected parallel to the hot/neutral aern't they ?
Thanks Joe
Joe...all parallel chokes have to be spaced away from each other or they will have the opposite effect. I find 3 to 4 feet (minimum) to be good. The effect does multiply as you increase the number on the line. As long as you keep your spacing good you should have no negitive side effects.Yes they are connected in parallel.
Alan
Thanks for posting your results.Like the others on the thread you linked, I don't think the Richard Gray assertions regarding the ability of a parallel choke to absorb fast voltage transients are correct.
However, there may be benefit from forcing reactive current to flow in the power wiring that feeds your audio system. Two possibilities that come to mind are (one) preventing noise from dirty connections from appearing near the AC voltage zero crossing, and (two) forcing nearby steel parts to be at different levels of magnetic saturation when the audio power supplies are drawing current.
This tweak involves continuous exposure to the AC line, so some care in building and insulating such a device is required. You don't want to burn your house down for a small improvement in sound!
So please clarify... this is a worthwhile tweak but it is really dangerous? A person doesn't get that impression on the Audio Circle thread. Seriously, i was going to give this a try but if it is a fire hazard, i would rather leave it alone. Thanks for any insight.
Chokes like this are made with transformer laminations for the core. The steel used is selected for its magnetic properties as well as cost, so there will be some magnetic losses from nonideal behavior, as well as circulating currents. These will cause some heating in this application. I don't know how much, so I suggested that KP test for warmth.If the choke gets hot, I would worry about it as a fire hazard and not leave it plugged in all the time. Either plug it in as needed, or get a higher-grade choke. If it stays cool, it is less of a risk. In any case, good workmanship in making the connections and preventing cord strain or damage where it comes out of the box are important factors.
Al relax. I consulted Hammond prior to suggesting the tweak. Both Hammond and myself came to the same conclusion. Simple Inductance at 60Hz / 120v will do nothing to overheat the core in the choke. I have several in my set up and all are running ice cold, and have for months.Alan
Alan,how do you have them connected? Just wired into an AC cable or do you have them in a box, fused, etc?
KP
KPAll are wired off the secondary of a isolation transformer. I haven't found the need for fuses. The first choke is installed inside the power conditioner. It is wired directly into the outlets. The temps inside are slightly warm because I use a combination of a step up/down and a isolation transformer. The step throws a lot of heat, but I haven't seen the choke throw any heat or be effected by the step. All the others are wired into the power cords. I made myself a filtered cord using a extruded aluminum Hammond project box. The cord is wired into a Kleen Line lab grade filter / surge protector. The choke leads are soldered directly to the primary side of the filter. The choke sits external to the box the same a it would on a tube amp. And thats it.
Alan
This sounds like something I want to try.
I was nervous at first until I spoke to Hammond's tech staff. I'm super pleased with the results. I have actually installed around 20 at EMI and I haven't heard any complaints. I did that back in Feb.
Alan
KP
Mine have been plugged in since the Nov / Dec 05' time frame and all are ice cold.Alan
I agree, the risk of fire is not worth it; I only plug it in when I am listening and remove if afterwards.I will like to try a couple more of them, to see if the effect is cumulative but first I'd like to come up with a way to make it safer. Maybe drop it in a box with a fuse?
KP
Hammond has the nickname "buzz-and-burn" in certain audio manufacturing circles. Plug the choke in for an hour or so, then uplug it and feel it to see how warm it gets. If it gets more than mildly warm, so that it is uncomfortable to keep your fingers on it, put it inside a larger box with some ventilation holes. A fuse would be a good safety measure.If it does not get warm, I'd be tempted to put it in a sealed box, embedded in quartz sand, and skip the fuse.
The link doesn't seem to work and I can't find the article. Is the choke wired up one lead to hot, one to neutral - parallel across the line?
Try the link, it seems to be working now.And yes to your question.
KP
KP
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