Hi there,
I have just won a lovely pair of vintage graetz BV8070 drivers for a full range OB project. The issue I have is not been certain of the appropriate voltage to apply to the field coil. I have seen it suggested that they take 100V, but at 950R that would mean 100mA, and about 10W heat - which seems excessive for this situation.
I know that often these were used in a radio and that they were used as a smoothing choke - so it that case the current and voltage would be defined by the Radio's current draw - which might be as little as 50mA or less.
Anyone got any informed ideas on this one.
Shoog
I have just won a lovely pair of vintage graetz BV8070 drivers for a full range OB project. The issue I have is not been certain of the appropriate voltage to apply to the field coil. I have seen it suggested that they take 100V, but at 950R that would mean 100mA, and about 10W heat - which seems excessive for this situation.
I know that often these were used in a radio and that they were used as a smoothing choke - so it that case the current and voltage would be defined by the Radio's current draw - which might be as little as 50mA or less.
Anyone got any informed ideas on this one.
Shoog
put this one through google translate Field Coil - Ñòðàíèöà 20 - Ôîðóìû ÀÓÄÈÎ ÏÎÐÒÀË
look at post 497
it sez 80mA - 90mA
ZM sez - use CCS and don't care for voltage
maybe asking Kwayzee Rullit guy via e-mail will help ?
dunno anyone else looking more adequate to have ancient FC knowledge
I found pictures back - in post 405 , but I'm lurker there , so I can see pic , even if I understand Russian almost good as English
look at post 497
it sez 80mA - 90mA
ZM sez - use CCS and don't care for voltage
maybe asking Kwayzee Rullit guy via e-mail will help ?
dunno anyone else looking more adequate to have ancient FC knowledge
I found pictures back - in post 405 , but I'm lurker there , so I can see pic , even if I understand Russian almost good as English
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Its definately not like that one. The field coil is somewhat lighter. Still I am hopeful for good things. I spoke to a man today who has quite a bit of experience on OB's with field coils and he reckoned at the cost of a bit of sensitivity I could get a better bass and tone by running them down at 50V.
I am thinking at this stage to go with an adjustable CCS arrangement with a raw 100V trimmed down to whatever voltage delivers the required 60-80mA. I feel a little more confident that I am not going to fry my new babies on first power up
Shoog
I am thinking at this stage to go with an adjustable CCS arrangement with a raw 100V trimmed down to whatever voltage delivers the required 60-80mA. I feel a little more confident that I am not going to fry my new babies on first power up
Shoog
Going for a lower setting than many suggest should keep thing nice and cool. I wouldn't be that happy running them at 45C.We don't have to many issues with things overheating in the frigid north of Ireland
Shoog
Started the build.
Surprisingly sweet sounding and quite extended in both directions. Unfortunately they are easy to overdrive in the bass so I may have to consider rolling the bottom end off with a cap (horrible).
Field coil energies nicely with a 100V Rectifier > 100uf cap > Microwave Oven transformer configured as a choke.
My active subwoofer amp is oscillating something horrid in the top end so is going to need a complete rebuild. One channel of the preamp has already burnt itself out - but the other shows potential.
Will keep you posted.
Shoog
Surprisingly sweet sounding and quite extended in both directions. Unfortunately they are easy to overdrive in the bass so I may have to consider rolling the bottom end off with a cap (horrible).
Field coil energies nicely with a 100V Rectifier > 100uf cap > Microwave Oven transformer configured as a choke.
My active subwoofer amp is oscillating something horrid in the top end so is going to need a complete rebuild. One channel of the preamp has already burnt itself out - but the other shows potential.
Will keep you posted.
Shoog
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