Resistance of Plate Choke

JBasham · **on:** January 29, 2013, 10:45:31 AM

Can anyone tell me the resistance of the Paramount V1.1 plate choke?

TIA,

Jamey

Paul Joppa · **Reply #1 on:** January 29, 2013, 11:22:33 AM

330 ohms - 165 per chamber. I rate it 80mADC and 23 henries; it runs at 70mA in Paramount with a bit more inductance at the lower current.

JBasham · **Reply #2 on:** January 30, 2013, 05:49:26 AM

Thank you very much!

In the zone for replacement with the unused pair of EXO-04s I have. 10ma over the MQ rating, but I have been doing that to a pair of EXO-03 for years now with no ill effects.

But maybe overkill at 50 henries, especially since I run OB speakers that are 100db sensitive but don't do much under 100Hz. They're supported by stereo subwoofers with their own mono amps.

Does Mr. LeFevre's BH-7 upgrade raise the inductance over the stock choke (I'm not asking you to divulge specs), or make the magic happen some other way? If you're at liberty to share. If not, please accept my apologies for asking rude questions.

Paul Birkeland · **Reply #3 on:** January 30, 2013, 05:56:21 AM

Along with increased inductance, if the capacitance of the plate choke can be decreased (which is likely over the PC-2), then high frequency response can be improved.

The EXO-04's are a pretty serious bit of kit, I'd try them in the circuit before drilling all the holes in the top plate (will they even fit?).

Paul Joppa · **Reply #4 on:** January 30, 2013, 11:51:01 AM

Huh. I guess I'm out of the loop - I have not even heard of an EXO-004.

The BH-7 runs (in my tests) 25 henries at the maximum current of 76mA; at 70mA in Paramount 300B it's 27 henries. So it's a slight improvement in that respect. It has other internal design features and measurements that I like but they are more MQ-proprietary.

For what it's worth, more inductance is always better in a plate choke. It just costs more. :^)

xcortes · **Reply #5 on:** January 30, 2013, 12:29:13 PM

Quote

I have not even heard of an EXO-004

I actually think you have. The 004's were also named Brainiac plate chokes.

Paul Joppa · **Reply #6 on:** January 30, 2013, 12:56:39 PM

The Brainiac was designed for 300Bs at 70mA, and had 30 henries inductance at 70mA maximum; it's built on the same core as the TFA-2004 so they look really good together. I had a full set once, with brass covers, but the amp they were in went on loan many years ago and hasn't been seen since.

I did (finally!) find some specs on an EXO-004: 50 henries at 60mA; DCR 317 ohms. My files are a mess; I don't think I've ever seen one.

Doc B. · **Reply #7 on:** January 30, 2013, 02:47:37 PM

Quote from: Paul Joppa on January 30, 2013, 12:56:39 PM

The Brainiac was designed for 300Bs at 70mA, and had 30 henries inductance at 70mA maximum; it's built on the same core as the TFA-2004 so they look really good together. I had a full set once, with brass covers, but the amp they were in went on loan many years ago and hasn't been seen since.

I did (finally!) find some specs on an EXO-004: 50 henries at 60mA; DCR 317 ohms. My files are a mess; I don't think I've ever seen one.

Actually I think I saw them on a shelf in Dr. Knobs' garage a while back. Maybe I can retrieve them next time I visit.

JBasham · **Reply #8 on:** January 31, 2013, 03:34:34 AM

Sorry to confuse things (though it happens to me often).

Like the EXO-03, which I sometimes see as the EXO-003, I have seen it as the EXO-004 or the EXO-04. They were pretty close in spec, but the 04/004 has bell ends for top mounting.

But wait, Mike explained it better:

http://db.audioasylum.com/mhtml/m.html?forum=magnequest&n=403&highlight=EXO-004&r=&search_url=%2Fcgi%2Fsearch.mpl%3F

I got a pair from his last run in 2006.

Paul Joppa · **Reply #9 on:** January 31, 2013, 10:07:05 AM

I note that Mike's web page currently says 40 henries for the EXO-003. That's consistent with my own measurements. It's easy to get 20-30% differences in measurements depending on the method used; mine is fairly conservative.

JBasham · **Reply #10 on:** February 02, 2013, 10:17:51 AM

Quote from: Doc B. on January 30, 2013, 02:47:37 PM

Actually I think I saw them on a shelf in Dr. Knobs' garage a while back. Maybe I can retrieve them next time I visit.

Here's a field guide photo to aid your search. It's the big boy in the center.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.flickr.com%2Fphotos%2Fjbasham%2F185948464%2F&hash=077f25466b18ebf68493db493d23cbebc41e3254)

I'm not sure my BB code to the Flickr photo is working. If it's not, here's the link: http://www.flickr.com/photos/jbasham/185948464/