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In Reply to: RE: Hammond 193L Choke Tweak Revisted posted by pixelphoto on December 30, 2016 at 21:34:47
I have 2 sets in each of my 2 systems... 1 pair for each systems main audio EQ AC, another pair for the 'dirty' HW & related EQ.
Each set has 2 of the chokes... 3 of them are a 193L/193M pair (as pictured), the 4th, on one system's dirty side is just a pair of 193Ls (I found a good deal on 2 more 193Ls and didn't want to pop for another 193M).
I pull the endbells off and mount them with brass hardware on a bamboo base. The screws can be tightened to help control humming, but I've had 1 or 2 hum such that tightening the mounting screws down did not cure the hum and I had to replace them (just like your experience, Rick... hi, BTW!). And the nut on the bottom of each is a rounded acorn nut (also brass) so they have some coupling to the floor.
Before I wire them up I try them both ways on the AC line (1 line to hot, the other the neutral, then reverse) and measure the AC leakage voltage from the laminations to the outlet's ground. I wire them with the orientation that gives the lowest measured voltage, just as I do with any power transformer. BTW, I forget which way Alan M suggested you wire them (to the short wire or long wire, which distinction of course disappears when you remove the endbells), this has been consistently opposite of his recommendation. Go figure!
The set pictured was an early configuration where I had a separate power cord and outlet for each of the two chokes. Now they just get wired in parallel. On the main audio EQ AC's, they are inline on the DIY AC power cord (12 gauge 4-cross braided with spiral ground) that goes into a PS Audio P10. On the 'dirty' EQ AC's, they are at the end of a DIY extension cord sized to reach to a nearby outlet on a different AC circuit and breaker.
Best I can do in this house without a major rip-up for dedicated lines... maybe someday!
I top each choke with an almost small-fist-sized raw sodalite stone. That was a recommendation by someone on this forum a few years back (Carcass maybe?) and has worked well for me. AND a lot less expensive than the Mad Scientist stuff, though probably not as good.
Before I wired them up inline on the AC power cords on each system's main audio EQ AC, I would just plug them into the 2nd outlet in that pair. Occasionally when I'd unplug for a thunderstorm, I'd. forget to plug in the chokes... and the system never sounded right until I did.
I don't expect to ever be without them!! Or the P10s, which make a huge diff in each setup.
Greg in Mississippi
P.S. On the topic of isolation transformers, there is some buzz on CA where Uptone Audio has recommended that in conjunction with using one of their fully isolated from the AC LPS-1 Ultracap power supplies, to use a low-interwinding capacitance isolation tranformer appropriately sized for their entire system and plug everything else that is not isolated into a low-impedance non-filtered outlet strip on the output of the transformer, removing all fancy AC filter setups. The low-interwinding-capacitance iso transformer provides both surge protection and noise filtering inherently.
This has seemed to work well for those who have tried it, none have said they are going back to their power filters, even pretty expensive ones.
I plan to experiment with this someday, with the ones on the main Audio EQ ACs' before the P10s. I think it will be complementary, but don't have a spare $1k or so to spend on the iso tranformers right now.
Not sure if it is my chokes that are humming - now I wonder if it the split bobbin HAMMOND power transformers I use for DAC and buffer power!
I am using two SIGNAL DU2 isolation transformers - one for analogue and one for digital - using chokes before and after each of these and another pair at the sub plate amps. In the digital side I have a choke near the DAC supply input and the same for the analog side at the buffer supply input.
Have been working with AC supply lately and think I have found a good way to do this in the minimalist way for materials and expense.
Using only two AC plugs - FURUTECH copper which I have wired with the 10 gauge wire you can get from APEX JR leading to each DU2. I am using these copper connectors: http://www.homedepot.com/p/Blackburn-Copper-Mechanical-Connector-8-Stranded-to-14-Solid-Wire-5-Packs-of-2-Case-10-Total-Pieces-L35-B2-5/202405835?MERCH=REC-_-PIPHorizontal1_rr-_-202487478-_-202405835-_-N. These are used to connect to the transformers and for wire junctions further down the line.
All IEC input connectors have been removed from components. Instead I am using the NEUTRIK POWER CON connectors for my ONLY AC level connector. There is a length of wire from the connector to where the previous IEC thing was. The other half of this connector is connected by the appropriate length of wire back to a junction made with the above mentioned copper connectors. There is only one "break" in each AC line to each component. The only AC receptacle is the one in the wall - there are no others used. All of the POWER CONS are inline - the panel mounts do not impress me -
Using the 10 gauge wire you can get three ends into each of the copper connectors. Depending on how many lines you have will determine how many junctions you need to make and whether you decide to use two connectors and bolt them together (with brass hardware) or just to use the screw down provision. I cover the junctions with plenty of ribbon I make from silk cloth just because I have access to it.
There is no comparison of the quality of the connection with the POWER CONs compared to any IEC. No more of those spring loaded connections except at the wall.
I cannot imagine a simpler less obtrusive set up.
I figure my AC is about as good as it can be.
At this point the SIGNAL DU2s are not in steel boxes - they are on a very thick piece of cardboard (almost an inch thick) and one can hear a slight hum coming from them as opposed to a buzz. I do not doubt it would be better to get them in a steel (not aluminum) box but I cannot find one and will have to make something one of these days.
One good thing about the isolation transformers is that you can use toroids if you want to. Thinking about trading out the buzzing split bobbins for toroids. The toroids in my First Watt amps make no noise at all. never thought i would see myself writing that!
No other AC filters are used. I tried the Jon Risch filter and I was reminded of an early Harry Pearson line about "painted ships on a painted sea" to describe the resulting sound. Depth and air were eliminated. Sounded terrible I am sorry to say since Mr. Risch is one of the best fellows in this hobby. That filter was designed a long time ago and maybe the caps I was using were the problem (paper RIFAs - I have read the paper WIMAs are much better). At this point I am not interested in pursuing the filter.
GStew, very informative reading. I received my third Hammond 193L choke today and it's now connected to my amp. These chokes are one of my four favorite tweaks.
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