Hammond 156C - good Plate choke load?? - diyAudio
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Old 12th November 2005, 03:24 PM   #1
kmtang is offline kmtang  Canada
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Default Hammond 156C - good Plate choke load??

Hi,

I am courious what kind of plate load choke is used in the 5842's driver circuit.

The Hammond 156C is rated 150H at 8mA. Wondering if this is good for this purpose.

Johnny
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Old 12th November 2005, 04:42 PM   #2
rdf is offline rdf  Canada
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Hi kmtang

My two samples measure a DC resistance just under 3500 ohms and impedance max at 2.1 kHz. From Spice this suggests a parallel capacitance in the 30 pf range, still good for a total choke impedance over 150 kohms at 20 kHz. FWIW I thought they sounded pretty good between a triode-connected E180F biased near 7ma and an 0C3 but were since replaced with IXYS CCSs to try higher currents. They may eventually go back in.
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Old 12th November 2005, 05:39 PM   #3
Fuling is online now Fuling  Sweden
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Ive used 156C as plate choke together with 6C4, PCC88 and PC86. Hard to beat for that price
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Old 13th November 2005, 03:48 PM   #4
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Check out this thread:

Vertical deflection tubes for audio output?

I used them in that amp and they sound great, and they are certainly co$t-effective.

-j
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Old 14th November 2005, 02:36 AM   #5
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I'll put in a good comment for the 156C's also. Quite nice sounding, especially for the money!

With the low cost of the chokes you can spring for the big bucks and use 2 in series. This has 3 things going for it.

1st, the inductance is double so you get 1 more octave on the bottom end of the frequency range.

2nd, because the capacitance of the chokes acts as 2 caps in series you will get better high frequency response. In the 26 preamp I built the 3dB down point went from somewhere near 30K to out past 70K. The single choke had a 4dB dip around 40K. With the pair of chokes the dip was only 2dB. There is a broad very low Q resonance around 60K so with 2 chokes in series it drops 2dB down near 30K, then rises back up gently and finally drops below the -3dB point somewhere above 70K. The numbers are vague cause I'm working from memory of a project done several years ago...

3rd, you can mount the chokes on standoffs, bottom to bottom and wire the chokes with one winding backwards. This makes the pair of chokes hum buckers. In my test setup the pair of chokes picked up 20dB less hum than a single choke.

Gary
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Old 14th November 2005, 12:41 PM   #6
Joel is offline Joel  United States
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Great ideas Gary, thanks.

I used the 156C in my 01A-01A-71A amp several years ago. Much better sounding than a 36k resistor load, as I first configured it.

Click the image to open in full size.

Joel
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Old 14th November 2005, 01:50 PM   #7
kmtang is offline kmtang  Canada
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Thank you guys for your valuable information.

Unfortunately, Hammond has the 156C choke only good for plate choke purpose. I am going to experiment using the 5842 tube to drive the 2A3.

The 5842 tube needs almost 20mA. Therefore, I need a plate choke to handle such high current. Any recommendations for a low cost plate choke like the Hammond 156C???


Johnny
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Old 14th November 2005, 02:20 PM   #8
Fuling is online now Fuling  Sweden
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I know that Hammond has a 30H / 40mA choke and I think they have a 20H / 20mA too.
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Old 14th November 2005, 09:50 PM   #9
rdf is offline rdf  Canada
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Quote:
Originally posted by Gary P

3rd, you can mount the chokes on standoffs, bottom to bottom and wire the chokes with one winding backwards. This makes the pair of chokes hum buckers. In my test setup the pair of chokes picked up 20dB less hum than a single choke.

Gary

What a great tip! Thx for that keeper.
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Old 15th November 2005, 12:43 AM   #10
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Quote:
With the low cost of the chokes you can spring for the big bucks and use 2 in series
But that's crazy money - literally DOZENS of dollars! Jeeze louise!

-j
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