Lace Alumitone Short Technical Review

[Possum]

alumatone patent....

6897369

[madialex]

First thing, I am glad to hear your health is getting better, very good word to hear indeed.

Yeah the whole Christmas economy thing gets to me. I mean, what would happen if Christmas was banned in the US forever. I guess these big stores and everything else associated with this wretched holiday would fall the fuck apart...I mean why bother to offer good sales and customer service throughout the year when you can half ass it all year and make up for it in spades at Christmas. Walmart comes to mind. I am all for making it as big as you can in any business but dont lose sight of what got you big in the first place.. Thanks to Wal mart doing away with layaway is the main reason my kids did without this year. They said they were losing money??????? How do you do that?? People pick items they want, pay walmart 10 to 20% down and the rest in 3 monthly payments, the customer gets their items everyone is happy right?? How the hell is that a money losing thing??? Oh, maybe it is because if you have something in layaway and that same item goes on sale and you tell them about, your items is discounted to the sale price as well, therefore losing money right?? What about all the exact same items they are selling on the floor at the sale price..... Makes no sense sense to me....

Just like the Prez harping about all these new jobs, cheeeya right!! If you take a restaurant worker and re-classify them to service workers there ya go,a huge increase in the service sector job total. Just a little creative number working is all that is. No new jobs are actually there, just a shift in a workers tittle.

[bbsailor]

Joe G. Question: It is plausible for an audio transformer to have a 16 Henry winding. What kind of transformer is it? Output, input, interstage, etc?

I believe it is an output transformer. It has the following numbers on it: 618 629999 then under that number is the following number: 497235. I picked up a box of them surplus many years ago and have been using them as input transformers for experimenting with low impedance pickups. They have a good E core size: .75" wide, .625" tall and has 18 core laminations at 3/16" thick for decent coupling at lower frequencies.

The low impedance side is 1.4 ohms DC at 8.5mH and the high impedance side is 1.25K at 16H. If my calculations are correct, they are 32 ohms to 50K ohms. Two humbucking coil bobbins filled with AWG30 wire should give me a pretty close match to the low Z side of this transformer with some room to mismatch some for tone adjustment purposes.

Thanks for the update on my old Tenma 72-6634. I lost the instruction sheet and was guessing at the test frequency. I calibrated it against my General Radio Impedance Bridge a few years ago and it was within 3% to 5% of the GR bridge across most ranges I use it on. The GR does run at 1kHz and can be also run from external signals at different frequencies. I use these to measure fast pulse induction metal detection coils in the 300uH to 500uH range. See my article: http://geotech.thunting.com/pages/me...s/FastCoil.pdf

I find it faster to use the Tenma than fiddle with nulling of the GR bridge and waiting for it to warm up and stabilize.

I have been doing some experiments with current sensing transformers and guitar pickups. Do a web search on CSE187L, a low frequency current sensing transformer. I initially used a single loop of AWG 18 magnet wire around a magnet and got a usable output. I even tried a piece of bare AWG 14 from household electrical cable and it works. The thicker the better to increase the current. This transformer has a 1 to 500 turns ratio and is inexpensive ($2.50).

I placed a scope current probe on the low Z wire and was able to get a peak reading of between 5ma and 10ma depending on how hard I plucked the high E string and how strong a magnet I used. That should give you something to think about!!!

Thanks for your thoughtful response.

Joseph Rogowski

[mkat]

Then there's the fact that JC is composite character and wasn't actually a single person and may not have even existed at all, the story of him is identical to a whole bunch of more ancient stories of gods born of virgin birth etc. etc. So now its about mass consumption and our economic index depends on its existence!

Well said. It says much about the education systems. A little critical thinking goes a long way, doesn't take much to cut through the recycled crap.

[Joe Gwinn]

6897369

Thanks. That is the one I have that was plausible, but couldn't recall if it was correct. It's actually intended for an acoustic guitar.

[bbsailor]

Joe G.

Look up patent 5831196 to see the actual Alumitone humbucking design along with other variants.

Joseph Rogowski

[Joe Gwinn]

Joe G. Question: "It is plausible for an audio transformer to have a 16 Henry winding. What kind of transformer is it? Output, input, interstage, etc?"

I believe it is an output transformer. It has the following numbers on it: 618 629999 then under that number is the following number: 497235. I picked up a box of them surplus many years ago and have been using them as input transformers for experimenting with low impedance pickups. They have a good E core size: .75" wide, .625" tall and has 18 core laminations at 3/16" thick for decent coupling at lower frequencies.

The low impedance side is 1.4 ohms DC at 8.5mH and the high impedance side is 1.25K at 16H. If my calculations are correct, they are 32 ohms to 50K ohms.

It does sound like a transistor output transformer. The high-impedance side is actually the primary, and the low-impedance side is the secondary. Not that it really matters - transformers work in either direction.

Two humbucking coil bobbins filled with AWG30 wire should give me a pretty close match to the low Z side of this transformer with some room to mismatch some for tone adjustment purposes.

The transformed impedance of pickup coils plus transformer winding should not exceed perhaps one fifth of the impedance of the volume control cum tone control, to prevent undue loading of the pickup assembly.

Thanks for the update on my old Tenma 72-6634. I lost the instruction sheet and was guessing at the test frequency. I calibrated it against my General Radio Impedance Bridge a few years ago and it was within 3% to 5% of the GR bridge across most ranges I use it on. The GR does run at 1kHz and can be also run from external signals at different frequencies. I use these to measure fast pulse induction metal detection coils in the 300uH to 500uH range. See my article: http://geotech.thunting.com/pages/me...s/FastCoil.pdf

If your DMM will measure frequency, you can use the DMM to determine the test frequency by hanging it across the item whose inductance is being measured during the measurement. Likewise, one can use a scope.

I find it faster to use the Tenma than fiddle with nulling of the GR bridge and waiting for it to warm up and stabilize.

Time for an Extech. What model of GR bridge do you have? I built a Maxwell-Wein Bridge to verify the readings from LCR meters, leading to the selection of the Extech. http://home.comcast.net/~joegwinn/

I have been doing some experiments with current sensing transformers and guitar pickups. Do a web search on [Triad] CSE187L, a low frequency current sensing transformer. I initially used a single loop of AWG 18 magnet wire around a magnet and got a usable output. I even tried a piece of bare AWG 14 from household electrical cable and it works. The thicker the better to increase the current. This transformer has a 1 to 500 turns ratio and is inexpensive ($2.50).

This ought to work, and is a cheap way to buy a toroidal half-transformer. The only thing that worried me was the restricted bandwidth - these current transformers are designed for power frequencies, not audio.

The #18 to #14 wire should be welded or soldered to form the loop, as the voltages are far too low for any mechanical connection method to be reliable.

I placed a scope current probe on the low Z wire and was able to get a peak reading of between 5ma and 10ma depending on how hard I plucked the high E string and how strong a magnet I used. That should give you something to think about!!!

If a 7000-turn coil can put a few volts across a 250K pot, the coil is generating 8 microamps. In a 0.250-ohm circuit, this corresponds to 8 amps, so seeing 0.01 amps isn't difficult. And the E string probably doesn't generate the full 2 volts. It takes some kind of storage function for a scope to catch the real peaks as well.

[Joe Gwinn]

Alumitone Patents

6897369

While pawing through my files of patents on paper, I found another patent that may be relevant: 5,831,196 (to Khanagov). The drawings look more like the Alumitone, if I recall, but I don't have an example to look at. I read my paper copy on 10 Nov 05, according to the penciled notation. This may be the data of our initial discussion of the Alumitone.

I see that bbsailor also found 5,831,196, and he has the Alumitone.

[bbsailor]

Joe G. Said: "The transformed impedance of pickup coils plus transformer winding should not exceed perhaps one fifth of the impedance of the volume control cum tone control, to prevent undue loading of the pickup assembly."

The general rule is that the load impedance (Vol and tone) should be 10 times the source pickup impedance. This optimum ratio is not always possible to attain with pot values ranging from 250K to 1M and the pickups having a high impedance at resonance. As you say, a 5 to 1 ratios is probably more realistic. The big tradeoff is the resonance shift due to coax cable capacitance and amp input additional loading. So, by keeping the pickup impedance to a reasonable level, the natural tone of a pickup can be more approximately maintained, however lower output levels are the consequence unless active buffering is used.

I have a General Radio Model 1656 Impedance Bridge and a good range of commercial test equipment including scopes, generators, lock-in amplifiers, Boxcar integrator, low noise voltage and current preamps and a variety of specialized probes.

Your observation about the lowZ input connections being critical is very accurate. I use small tubing about .5" long that matches the diameter of the transformer primary wire size around AWG 12 then use a similar size wire for the primary loop under the strings. Mouser stocks these transformers and it might be worth getting one or two for some experimentation. The secondary resistance of the CSE187L is 21 ohms and I measures it out between 2K and 2.5K ohms impedance. The output impedance value is very sensitive to the input impedance loading/matching. These transformers are very sensitive to being in a low resistance primary circuit so they must be attached directly at the pickup assembly near the strings. This does open the possibility for making a multiple pickup guitar with all volume and tone controls being medium impedance. Then, a Shure microphone matching transformer can be used at the amp to go from a medium Z of 2.5K ohms to 50K into the amp. Les Paul did this years ago.


Joseph Rogowski

[Joe Gwinn]

I just purchased the Lace Alumitone Humbuckers set (black).
Here are the technical details for those interested.

Each magnet is: 1 3/32" long; 7/32" wide and 1/8" thick ceramic.

The metal frame of the pickup shell is also the two primary humbucking windings and it is also 1/8" thick. The magnets are glued to a plastic shelf which is also glued to the underside of the alumium shell.

What are the dimensions of the aluminum frame/windings? Is it one loop, or two? The intent is to compute the DC resistance of the loop from the geometry, on the assumption that the material is pure aluminum (alloy number 1100).

Joseph Rogowski

An illustrious heritage?

http://en.wikipedia.org/wiki/Rogowski_coil

[bbsailor]

Alumitone Physical Dimensions

What are the dimensions of the aluminum frame/windings? Is it one loop, or two? The intent is to compute the DC resistance of the loop from the geometry, on the assumption that the material is pure aluminum (alloy number 1100).


An illustrious heritage?

http://en.wikipedia.org/wiki/Rogowski_coil

Yes, the last name is famous in terms of current sensing coils, but no relation to me that I know of. Maybe back in the old country (Poland) where my Grandfather came from there was a family connection.

http://lacemusic.com/electric_pickup...tone_specs.php My pickups look like the humbucking version of this with the "Z-like" center section and one magnet under three strings and another magnet under the other three strings.

Look at the Transbucker specifications in particular the transbucker with 3.4K resistance and 10.5H inductance. http://lacemusic.com/electric_pickup...nsor_specs.php This is the measured specification of my pickups.

The Transbucker is more similar in electrical specification to the pickups I received than the Alumitone pickups pictured on the Alumitone web page but are listed as having 16.74H at 2.5K ohms. Yes, this is a little confusing????

My pickups have two individual magnets on the top. There are actually two loops sharing a common center conductor piece (zig-zag). The center section is sort of "Z-like" to accomodate the two magnets. Here are the dimensions.

Neck to bridge direction dimension: 1 7/16" in the following three sections
11/32" side conductor piece
15/16" center Z-like conductor piece
11/32" side conductor piece
3/64" gaps between parallel pieces separating center from side pieces.

Width E to E string direction dimension: 2.5"

Tall: .75"

Alumium shell thickness throughout: .125"


Joseph Rogowski

[David Schwab]

6897369

That not it... that's a variation used for acoustic guitars.

The patents are 5767431 and 5831196. Those are for the Transsensor pickups. The Alumitone doesn't have its own patent but uses the same principal.

[madialex]

The transformed impedance of pickup coils plus transformer winding should not exceed perhaps one fifth of the impedance of the volume control cum tone control, to prevent undue loading of the pickup assembly.

Uhm, Hey Joe, not real sure about all this stuff way over my pea brain but this one little thing I have in bold is bothering me. Are you thinking about electronics and maybe a little something else, Ehh.

[Possum]

why?

What is the purpose of this one turn pickup with a transformer? Is it the "cool" factor so the thing looks really cool and space age or is there some kind of tone thing I am missing here :-) These pickups don't sound good to me. I don't quite get the point of doing one of these and trying to make it sound better than what Lace did. I also wonder how they patented something that has a previous patent only a couple years earlier using the same idea. Yeah they look really cool but they dont sound very musical to my ears....

[Joe Gwinn]

Uhm, Hey Joe, not real sure about all this stuff way over my pea brain but this one little thing I have in bold is bothering me. Are you thinking about electronics and maybe a little something else, Ehh.

It's pure electronics. Another way to say it is that if the volume control pot is 250K, the source impedance of the pickup cannot exceed one fifth of 250K, or 50K, and one tenth, or 25K, would be nice.

So, what is source impedance? It's exactly analogous to the output impedance of an amplifier. If you connect a resistor of this value across the output (of amplifier or pickup), the output voltage will be reduced to one half of the unloaded (open-circuit) voltage.

So, the primary effect of requiring that the load resistor (the 250K pot in this case) must be a factor larger than the source impedance is to limit the loss of output.

This light loading has a secondary effect of preserving the spectral balance of the source pickup, as overloaded pickups lose lows, and the overload also increases the width of the resonance, further changing the spectral balance.