 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
24.6.198.63
I had a Hammond 193L gathering dust (left over from a tube amp project) and decided to try the "choke tweak". Let me say first that many AC tweaks have not had a big impact on my system. I have a filter made out of ferrite rods with a layer of wire around them and small caps that does a good job of blocking and isolating RF. So I wasn't expecting very much.
Well after hooking it up and plugging it in I noticed a significant change, the soundstage got much sharper, like tweaking the focus of a projector. Things sounded louder, even though nothing else had changed. BUT the sharpness was a little too much, kind of like the sharpness control on a TV turned up too high. It was a little harsh and glaring and fatiguing after a short time listening. There was also kind of a hollow sound to the whole thing.
I decided to give it the prescribed 5 days burn in. For the first 3 days there was no difference, at day 4 it started smoothing out significantly. At day 5 WOW! The harshness was completely gone, the hollowness was gone. The dynamics were majorly improved, any percussive instrument now has an amazing attack. You can feel a plucked string bass. Drums, piano, guitar etc are radically improved. The sound stage on well recorded live events is huge, I can sense the space around the performers like never before. Building reverberation is more there but less obvious. Previously it kind of hung around the performers in their "space", now its part of the ambient space like it should be. Its definately wonderfully there, but doesn't call attention to itself. A much more natural presentation.
Kingston Trio recordings and large choirs have made the greatest improvement with this tweak. I sing in a several choirs and go to concerts frequently, recordings of such groups have always left me wanting something more. A good choir has a dynamic range and impact that is spine tingling, I just haven't heard this before in reproduction. With the choke in place it got much closer to live (its still not all the way there).
Something happens when a good choir is singing well together where the sound from the individual voices fuse together forming an almost palpable sound field around the whole group that has an amazing sonic "texture". I hear this fairly often in live performances, but it almost never makes it across the recording barrier. With this tweak I'm hearing this on several recordings now, it really is spine tingling.
My wife is having a hard time prying me out of the listening room to work on the "honey do" list today. I keep on telling her this is a scientific experiment, I have to asses if the "tweak" is working or not, I don't think she believes me!
So it definately works, way more so than I thought it would. That 5 day burn in is absolutely essential. Don't even think about critically assesing the sound earlier - you will be disappointed.
Highly recommended. By FAR the biggest bang for a tweak I've ever gotten.
John S.
Follow Ups:
I will second what you wrote, "Highly recommended. By FAR the biggest bang for a tweak I've ever gotten". Especially considering the cost and ease of implementation. I currently have six 193L in my system. I have four more to experiment with at the house.
Chris
John,
Thanks for your subjective impressions. Now, what I'm really looking forward to hearing from you is the results of your empirical investigation into what exactly is going on with this shunt inductor, rather than speculation. While I've heard much discussion of what is going on, it seems that none of this is supported by any measurements (leastwise, that I've seen).
TIA,
Paul
The Hammond 193H is a smaller brother of the 193L. Both are specified as 5 henrys, but the 193H is for use at 200 mA instead of the 300 mA rating of the 193L.
It is reasonable to assume both use the same core material.
The core will limit the maximum frequency for which the device will act as an inductor. Above the maxumum frequency at which the core magnetic domains will follow the impressed current, the core stops participating, and the device has the residual inductance of the winding geometry, the parasitic winding capacitance, and a frequency-dependent resistance due to skin effect in the solid wire.
I don't have a 193L handy, but I do have a 193H. I connected it to a resistor and a signal generator, and swept the frequency. The choke impedance rises with frequency to 5 KHz, then it drops.
Many power transformers I've tested this way have a maximum frequency in the 40 to 100 KHz range, so Alan is correct that the Hammond chokes are superior as AC noise filters. However, the real reason they work so well is that their cores are not built for wide frequency response.
I would like to see the results of similar measurements on the 193L and 193M.
Given your explanation above, I'll rephrase and say that I look forward to Mr. Swenson's take on what underlying mechanism(s) is responsible for the efficacy of this component.
If its functioning as a noise filter, I look at it as a attenuation network with frequency dependant reactive elements terminated with a reactive/resitive load, a freqency dependant voltage divider.
If it is(also) fuctioning as a passive power factor correction interacting with the specific reactive charateristics of the load(s), I'd look at the line's harmonic content under appropriate load, both with and without correction.
I don't follow the logic of the explanations, unable to comprehend at this level of abstraction. It certainly doesn't behoove either you or Alan to actually measure anything in situi or appoximate. I'm not grasping how/why this durn thing works, and I'm just hoping that John might investigate its mechanism with additional tools and share those findings.
Bad form, no doubt, to re-post a post, but perhaps the link below helps.
In it I mention resonant frequencies in the MHz range, but it seems from Al's post that it is much lower--in the 5 KHz range.
Correct URL is http://www.audioasylum.com/audio/tweaks/messages/14/145002.html
or core magnetic behavior (or both). I suspect core magnetic behavior in the Hammond chokes, as transformers of similar size have much better frequency response.
All real capacitors and inductors are limited in frequency response by their parasitic inductance and capacitance, respectively. Getting an inductor that is useful at the noise frequencies that affect audio component performance is not trivial. Even so-called "RF" chokes with ferrite cores tend to have low self-resonance frequencies. I've found it necessary to make composite inductors, with several units in series, each one with smaller inductance and higher self-resonance frequency, to get broad-band coverage.
As far as I can see, the placement of the inductor across the line provides a low impedance at frequencies lower than the 60 Hz power line frequency, thus, it would attenuate low frequency disturbances on the AC power line below 60 Hz, with it's DCR the impedance at "DC".
While this may seem trivial, it helps to remember that almost all AC line filters, including my own DIY AC Line Filter & SS, filter out the HF's, and do nothing to the frequencies below some cut-off frequency. In the case of my AC Line Filter, it starts to cut-off up near the top of the audio band, depending on the exact source and load impedance.
As for how much AC power line content there is below 60 Hz, this is entirely dependant on your local power line conditions, and it is not uncommon for there to be residual "DC" present on the order of a volt or two, as well as frequency components between DC and 60 Hz. Most of those are the result of industrial equipment, unbalanced loads, and poorly designed and implemented power supplies that are sharing the AC line with your stereo equipment, esp. switchmode types. In a "perfect world", they wouldn't be there, but hey, we live in the real world, where Murphy thrives and rules.
Given that many of the classic audio components that are highly regarded for their sound also can have very simple/basic power supplies, and may be the most susceptible to LF AC line garbage, it would not be surprising to find that filtering out/attenuating those lower frequencies could provide a sonic inmprovement.
Whatever the choke does for HF's or RFI would be in addition to it's benefit at frequencies below 60 Hz.
Jon Risch
Thanks Jon - I hadn't considered it as a highpass shunt filter. I wouldn't think it makes a particularly good lowpass filter when its impedance finally falls below that of the line frequency. It would make a very expensive, ineffective X cap.
I still think its something to do with passive power factor correction, but I have no real or valid measurements to back up any suppositions.
Alan, are you suggesting that each component be provided with a choke in parallel as close to the component as possible?
thanks
Les
Les
Yes I am...that combination appears to work best for me. Inside the PLC I use one choke per duplex, but each component power cord has a choke built in for additional filtering and isolation. I have said this many times before...the choke effect is local, if you use the method I described you will be hard pressed to find a better a/c filter for under a grand. The choke is part of a idea I came up with several years ago...if you stick to that idea you will never go back to traditional filtering again. One step at a time.
Alan
Hi Alan
Do you mean to say that you have "hard-wired" a choke into each of your power cords as well as putting on into the empty outlet on the duplex powering your system? That is, near the male AC plug end from each component, you wired the hot and neutral wires in your AC cord into the the choke leads and then these combined twisted wires to your male AC plug and the ground wire from the AC cord and a new one from the AC plug to the body of the choke? I'm sorry to be dumb, but I just want to be sure I understand correctly what it is you're recommending, because I really like what the choke has done plugged into my duplex and would consider adding more if things can get even better.
Thanks
Chris
I had the same experience. However, mine won't take 5 days to get the improvement. After a day plugging the choke in, i can hear the difference in bass which is the most improvement in my system. I feel strong punch in my chest...and by the way, vocal is so sweet....:)
As Alan suggested, i put in a second choke, but heard not much improvement. Then i took one out and moved it the hometheater room. I can tell you that 193L does improve in video! Color is deeper and vivid, less noise.
So, now i have one choke in home theater and one choke in 2 channel system.
have fun.
Ive just installed and burned in a 193M choke (took it up a notch cause Im in 240V land).
For those asking on how to install, this is what I did to give me maximum flexibility.
The choke has two leads. I wired them into a chassis mountable IEC socket that had screw-in connectors (longer lead to hot, shorter to neutral). I also added a ground wire to the choke by tightly wrapping one end around one of the ends of the chassis bolts and secured it tightly by adding another nut of the same gauge. I wrapped this new ground wire down and under the chassis so it came out parallel to the other two lead and secured this to the ground pin of the IEC. I wrapped the wires in tech flex and heatshrinked the ends. I then put a rectangle of adhesive acoustic rubber foam sheeting to the underside of the choke to hold all of the wires in place and to acoustically isolate the choke from the floor where it sits.
So now I have a choke with a small 'tail' of cable terminated with an IEC. This allows me to plug in any power cable so that I can move it around between sockets to try it out.
For the first hour of use there was a major bass hump. In fact all bass sounded like the same frequency. Over the night the bass evened out to be accentuated across all of the bass range, still way too much. Buried in there the high frequencies and mids definitely seemed nicer smoother and more forward without being unpleasant. I knew it took a week to settle in. So let it settle in, I did.
It took 10 days to stabilise/burn-in. The bass has subsided and the whole presentation is more neutral with nicer mid range and highs with a hint of the new choke warmth remaining. For me it wasnt revelatory like for some, but it was definitely an improvement.
As discussed elsewhere the addition of a 1A slow blow fuse on the hot lead is a very good idea, which I might implement when I find the best socket for it and I take the IEC off and wire it directly into a power cord.
to the choke, but how does it hookup going to the equiptment??
AB.
The choke connects to a standard power cable which plugs into an outlet next to the outlet to the component (no direct connection to equipment needed).
the power and the equiptment, its just pluged into the curcuit at the receptacle.
Thanks.
AB.
Wire the choke leads into a ac plug and plug it in...that's it :)
Alan
I've been hearing about this tweak for awhile now, but no clear description. How does it implement, John!
Mahalo,
Poinz
Can you post a photo of this tweak? I would like to know how it should be implemented, thanks if you are able to.
John
Glad to hear the tweaked worked for you. I have had huge success in many installations. May I make a suggestion...remove the ferrite rod and parallel caps. The rod and caps are causing odd harmonic ringing, which is why it took the choke 5 days to set up, removing these items for the system will take the sound and video quality up another notch. I also recommend adding a couple more chokes for better component isolation and filter extension.
Regards
Alan
Has anyone checked the DCR, current draw and inductance after it's been in service?
After two days, I decided to test it out.
DCR can't get a reading, H is 0, and load is 34mA.
I've run the same tests on surplus chokes and all test fine.
I had a 0.5A breaker on it at all times.
Alan,
Do you mean that when using the 193L choke, the Jon Risch DIY AC power line filters and isolation transformers should be disconnected from the main power system as they contain ferrite rods and parallel caps ?
Thanks.
Yes and no...I have some cables with built in filters for noise and surge protection. In this situation I just place the choke on the output of the filter. The filter still does it's job and the choke continues to reduce the ringing.
Alan
Harmonics of what? The LPF pole? 60Hz?
I'm considering updating my line filtering so am sort of keeping my eye on what other folks are doing. Since scant detail of his filter was given in the post, I'm surprised that you can tell that it's causing problems.
Just what is the concern? If I knew what it was and how it causes problems perhaps I could avoid it by design.
Thanks, Rick
Rick...it's fairly simple...all noise is caused by frequency imbalance. The incoming service into your house is fairly clean. Noise, harmonics, Rf, or whatever you want to call it is caused by the appliances (including your stereo) that are plugged into the circuits of your house. Ringing harmonics are caused by the cap / choke filter in 99% of your electronic components. What we are talking about here is the leakage from the first shunt capacitor in each component. The ringing could be caused by a uf value mismatch between component A, B, and C...or it can be too many at the same value causing a overlap in frequency (very similar to a crossover effect for the ac line).
As I mentioned before, everything on the line effects frequency. Ferrite rods shift frequency. Harmonic ringing caused by the shift can be fine tuned by moving the rod up and down the cable. In this case you are not fixing the problem, but altering / shifting the problem to another less noticed frequency.
I have been playing / installing the choke in various products that I design for the last couple of years. I have run into problems many times when combining the choke with normal single cap parallel filtering or ferrite beads and rods. Multi-valued cap filtering on the other hand has offered a nice step forward when combined with the choke.
My best advice to you is to install one choke per component. The choke will remove the ringing and offer PFC for the isolated component. At the same time it will offer parallel filtering for the other components plugged into the same circuit.
regards
Alan Maher
Hi Alan,
I appreciate the info and am trying diligently to understand it. My difficulty may be with the terminology as I think of "noise", "RF", and "harmonics" as largely separate things. Let me try this in Rick-speak and see if I'm close...
Is "leakage from the first shunt capacitor in each component" the voltage imposed upon the power line at the outlet due to processes within the component?
Does this statement describe the resonance situation? "The process of using L/C filters to reduce susceptibility and emissions can have the side effect of resonating at one of the harmonics of the power line which causes problems".
It would help my understanding a great deal to know within an order of magnitude the frequency range where you are seeing the ringing. It sounds like you've identified a band that causes the worst problems.
Last winter I tried connecting a honking transformer as a choke to my study stereo and heard no difference at all. Which tells me nearly nothing. The choke may not have had the right attributes, the system might not be susceptible to the effect, who knows?
Thanks, Rick
Ok...lets look at them one at a time.
"Is "leakage from the first shunt capacitor in each component" the voltage imposed upon the power line at the outlet due to processes within the component?"
A typical switch mode power supply has a very simple noise filter at the input. Capacitor-Choke-Capacitor is a very simple noise filter. In this design the capacitor is placed across the hot and neutral. The capacitor will leak on the neutral side. Simple parallel filtering is designed to create common mode rejection in electrical wiring (power cords) by altering the magnetic balance of the cable. The leakage from the capacitor is how the magnetic flux of the cable will be altered. Sounds simple...and it is...but, the value of the cap has a narrow band ringing frequency. The frequency is altered by the magnetic flux inside the cable...this is problem number two. By itself it causes minimum harm, but combined with multiple components and now you have a problem. Maybe component A has a .33uf cap and component B has a .22uf. Maybe component A and B both use a .33uf making it .66uf in parallel back at the wall outlet. Maybe the wall outlet is made out of brass and steel and ringings in the upper mids right at the same frequency as the caps. The odd harmonic ringing that has just been created is described by audiophiles as RF noise. RF in reality is the wave patterns (multipath) you see on tv or the radio station that is heard. What we are talking about is harmonics.
"It would help my understanding a great deal to know within an order of magnitude the frequency range where you are seeing the ringing. It sounds like you've identified a band that causes the worst problems."
We are addressing harmonics from dc to about 100KHz. The main area of concern for audiophiles is between 500Hz and 5KHz...well within the range of the choke. Lowering the harmonic ripple at this range provides true to life audio reproduction. The same can be said for people commenting about improvements to video. By reducing or eliminating the ringing in the lower band we are able to greatly reduce the ringing in the MHz and GHz range...which is why both digital audio/video and analog video are greatly improved.
"Last winter I tried connecting a honking transformer as a choke to my study stereo and heard no difference at all. Which tells me nearly nothing. The choke may not have had the right attributes, the system might not be susceptible to the effect, who knows?
I will ne honest with you...the transformer doesn't come close to the choke benefit. Some large (20A plus) transformers (isolation) offer small benefits from the added inductance, but most of that inductance is on the secondary and blocked by the center shield. The choke is different in every way.
Alan
Hi Alan, thanks for the details, it's a great help knowing that you are considering frequencies <100KHz.
Perhaps one of the reasons I noticed no effect last winter was because that system is rather old and only has linear power supplies in it as far as I know. Maybe adding the choke make more difference in systems that use switchers.
I think the main things I'm coming away with is to concentrate my efforts on stuff under 100KHz and to get one of the "right" chokes to play with. That's probably enough fuel for the fire for now...
Thanks for sharing your insights and experiences, I look forward to getting the chance to pursue this further,
Rick
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]