Just received one pair of grid chokes, AMCC 8 amorphous C-core, 1700H/8kOhms/15mA, 6x5,5x4 cm specifications. Manufacturer is AE-Europe from Netherlands, they had one pair in stock and I got them in a week. Chokes don`t have "legs" or similar way to fix them to chasis, must invent something...
The nice factory price of 60 Euros (~$71) per pair exactly was doubled at the end, by addition of various taxes, postages and bank provisions...
Listening test coming (not so) soon...

I am also waiting for a few folks to bring the comparitive samples. I ran the 'scope through Cal. What a PItA, and it was OK...and within specification( for an older 100 MHz Tek ). The VOM was quite simple by comparison...:)

I too need a means of mounting them. I think some Cu buss bar bent to shape over the core and bolted to a thicker piece of Cu will do it. Cu gets pretty hard when worked, no?

Looking forward to hearing your impression of the amprphous. That material is VERY nice, even compared to some other exotics. I may try some 7% Si lamination. I know a source, and it ought to be relatively simple to get the core free. Higher perm, and lower loss than 3.5% Si.
cheers,
Douglas

I found a simple solution, little PCB board and strip of rubber between the choke and PCB. Mounting screws M3 through little 3/8" round rubber washer, between the chasis and PCB...

P.S. Direct measuring with capacitance-meter gives horrible ~700pF winding capacitance (not real, I hope:-), haha...

Are those center tapped, or one long winding? AND they carry DC?
cheers,
Douglas

Congrats on your purchase... I hope you enjoy them.

Out of curiosity... did the manufacturer provide you
with any of the following data?

1) what is the max operating level? i.e., what magnitude of
ac signal volts and at what frequency was this unit designed
for?

2) I think you've already said that the winding capacitance was not
specified.

3) what is the leakage inductance?

4) there is a mention of "15ma"... but it is unclear whether this is a spec for a dc current or an ac current.

5) is this unit airgapped to carry unbal current? Was the 1700 henry number specified with any unbal dc current component across the windings? At what frequency and signal level was that inductance measured at?

6) do they provide a measurement of the incremental L? If so... at what signal level and frequency?

7) Do they provide a measurement of harmonic distortion?

On another note; here's an observation I made from the photos... that I have never seen before on a trans...

notice how the lamination does not fill the "core area" of the bobbin?
It looks like too large a bobbin was used for this size c-core and you end up with a large void (unfilled core space)... i.e., that the stack height of the bobbin has not been filled by magnetic core material.

I realize that the core they used is an off-the-shelf part number (i.e., a stock premade core)... but it looks like the wrong bobbin was used on this core. As I recall the manufacturer of this core does offer specific bobbins for their different size c-cores... I wonder why the coil manfuacturer did not use the right size bobbin.

In case you don't see what I am saying.... look at the picture on the left and then look at the left coil... see that large empty space? Never seen that before on an audio trans.

Do you think this empty space would have any effect on performance?

Just wondering.

msl

Congrats on your purchase... I hope you enjoy them.

Out of curiosity... did the manufacturer provide you
with any of the following data?

1) what is the max operating level? i.e., what magnitude of
ac signal volts and at what frequency was this unit designed
for?

2) I think you've already said that the winding capacitance was not
specified.

3) what is the leakage inductance?

4) there is a mention of "15ma"... but it is unclear whether this is a spec for a dc current or an ac current.

5) is this unit airgapped to carry unbal current? Was the 1700 henry number specified with any unbal dc current component across the windings? At what frequency and signal level was that inductance measured at?

6) do they provide a measurement of the incremental L? If so... at what signal level and frequency?

7) Do they provide a measurement of harmonic distortion?

On another note; here's an observation I made from the photos... that I have never seen before on a trans...

notice how the lamination does not fill the "core area" of the bobbin?
It looks like too large a bobbin was used for this size c-core and you end up with a large void (unfilled core space)... i.e., that the stack height of the bobbin has not been filled by magnetic core material.

I realize that the core they used is an off-the-shelf part number (i.e., a stock premade core)... but it looks like the wrong bobbin was used on this core. As I recall the manufacturer of this core does offer specific bobbins for their different size c-cores... I wonder why the coil manfuacturer did not use the right size bobbin.

In case you don't see what I am saying.... look at the picture on the left and then look at the left coil... see that large empty space? Never seen that before on an audio trans.

Do you think this empty space would have any effect on performance?

Just wondering.

msl

Congrats on your purchase... I hope you enjoy them.

Out of curiosity... did the manufacturer provide you
with any of the following data?

1) what is the max operating level? i.e., what magnitude of
ac signal volts and at what frequency was this unit designed
for?

2) I think you've already said that the winding capacitance was not
specified.

3) what is the leakage inductance?

4) there is a mention of "15ma"... but it is unclear whether this is a spec for a dc current or an ac current.

5) is this unit airgapped to carry unbal current? Was the 1700 henry number specified with any unbal dc current component across the windings? At what frequency and signal level was that inductance measured at?

6) do they provide a measurement of the incremental L? If so... at what signal level and frequency?

7) Do they provide a measurement of harmonic distortion?

On another note; here's an observation I made from the photos... that I have never seen before on a trans...

notice how the lamination does not fill the "core area" of the bobbin?
It looks like too large a bobbin was used for this size c-core and you end up with a large void (unfilled core space)... i.e., that the stack height of the bobbin has not been filled by magnetic core material.

I realize that the core they used is an off-the-shelf part number (i.e., a stock premade core)... but it looks like the wrong bobbin was used on this core. As I recall the manufacturer of this core does offer specific bobbins for their different size c-cores... I wonder why the coil manfuacturer did not use the right size bobbin.

In case you don't see what I am saying.... look at the picture on the left and then look at the left coil... see that large empty space? Never seen that before on an audio trans.

Do you think this empty space would have any effect on performance?

Just wondering.

msl