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.
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.
Check out this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=60346&perpage=10&pagenumber=2
I used them in that amp and they sound great, and they are certainly co$t-effective.
-j
http://www.diyaudio.com/forums/showthread.php?s=&threadid=60346&perpage=10&pagenumber=2
I used them in that amp and they sound great, and they are certainly co$t-effective.
-j
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
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
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.
Joel
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.
An externally hosted image should be here but it was not working when we last tested it.
Joel
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
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
I'm reviving this thread because I just built a 26 preamp using two 156c plate chokes in series, humbucking as suggested, and it's the best preamp I've ever heard. I've used these plate chokes before with good results in another 26 preamp, but this time I used filament bias with a 5 ohm high quality wirewound resistor (40 watts, gets hot), 95v on the plate of 26, 3.2mA and 4.6v on the cathode. Filament was starved at 1.2v. I used a Rod Coleman filament board supplied by a 12v DC supply. Actually a cheap DC 12v converter even.
The preamp sounds so good I thought I'd pass on the tip.
Talking of the Hammond plate chokes, someone mentioned the 157G - 30H and 40mA. Has anybody tried two in series as a driver plate choke? Or for that matter two of 154E - 20H at 20mA?
andy
The preamp sounds so good I thought I'd pass on the tip.
Talking of the Hammond plate chokes, someone mentioned the 157G - 30H and 40mA. Has anybody tried two in series as a driver plate choke? Or for that matter two of 154E - 20H at 20mA?
andy
Sorry to dig this thread up out of the dark ages, but I'm interested to know the exact wiring which would enable these chokes to operate in the above fashion.
In the figure I have excluded the possibility that one choke's lead are facing the other direction, which could very well be the mentioned setup.
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