Choke selection

malig · Post by **malig** » Mon Jan 28, 2013 5:36 am

Do what is the minimum ma rating for a modded 100w (with tube fx loop, and an added gainstage ?

100ma is not enough, 150ma will do it ?

demonufo · Post by **demonufo** » Mon Jan 28, 2013 8:28 am

100mA is the standard vintage Marshall fare for a 100W amp, but in those with high plate voltages it can be a bit overstressed.
150mA should be sufficient.

malig · Post by **malig** » Mon Jan 28, 2013 8:56 am

Cool ! Thank you

HTH · Post by **HTH** » Mon Jan 28, 2013 9:17 am

Its worth noting that Mercury Magnetics make multi-chokes with various taps - the MM-MULTI-12H or MM-MULTI-CH-25 would make a great candidates for plexi tweaking, could put the taps on a rotary switch and listen on the fly...

MM-MULTI-12H
2 Henry (DCR = 32Ω)
5 Henry (DCR = 50Ω)
7 Henry (DCR = 58Ω)
10 Henry (DCR = 69Ω)
12 Henry (DCR = 76Ω)

MM-MULTI-CH-25
5 Henry (DCR = 63Ω)
10 Henry (DCR = 88)Ω
15 Henry (DCR = 110Ω)
20 Henry (DCR = 125Ω)
25 Henry (DCR = 140Ω)

malig · Post by **malig** » Mon Jan 28, 2013 9:29 am

Looks perfect for testing

I might buy one actually...

demonufo · Post by **demonufo** » Mon Jan 28, 2013 11:27 am

I wouldn't bother with the 25. The sweet spot for most people is between 2 and 7 henry's. More than 10 is just overkill.

malig · Post by **malig** » Mon Jan 28, 2013 1:55 pm

demonufo wrote:I wouldn't bother with the 25. The sweet spot for most people is between 2 and 7 henry's. More than 10 is just overkill.

Exactly my thoughs

Ralle · Post by **Ralle** » Wed Jan 30, 2013 5:00 pm

I don't know how many H my two chokes have, but they messaure 105 ohm ( C1999 ) and 114 ohm ( Drake 352-114 ) when they're dissconnected... and the c1999 sounds the best in my ears... the Drake choke is a bit to loose and muddy for me...

malig · Post by **malig** » Sat Feb 02, 2013 7:25 am

Lots of Drake measures a bit higher than 3H, a lot of them where 5h (I think...)
The Dagnall where a bit more consistent at around 3h

demonufo · Post by **demonufo** » Sat Feb 02, 2013 9:09 am

Measuring inductance is very hit and miss without a really decent meter anyway.

yngwie308 · Post by **yngwie308** » Fri Feb 08, 2013 10:52 pm

Brilliant thread I have learned a lot, wish I had known all this gen when I had my Black Flag!!
Only on Metroamp would this data surface and people who have experimented with various models and passed on their knowledge!!

yngwie308

Roe · Post by **Roe** » Sun Feb 24, 2013 4:35 am

demonufo wrote:...
What should be noted in this investigation, is the actually mA rating of the chokes, which will affect ghosting vastly. In the original 100 watt amps, the chokes were 100mA rated, which at full tilt, is running these beyond spec, hence the ghosting can be quite apparent.
According to specs, the Marstran C1999 choke is 150mA rated, and the ClassicTone equivalent 49-18058 is 250mA DC rated. This will have a massive bearing on ghosting and filtration. Equally as much as the actual inductance rating, since the originals often cannot cope with the task.

max current on a 100w is around 140mA, if you have el34s that draw a lot of screen current (RFTs/Siemens in particular). although the drake and dagnall chokes are rated for 100mA they will typically handle more current. however the inductance will probably drop below 3 Henry.

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