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
even if I can't help with this one , I don't mind some porn .
that way I can be even happier for you
that way I can be even happier for you
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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Sounds a bit of a fan to me.
I heard it said that these were made in the same factory as the siemens Klangfilm drivers which go for €1000+. These ones I got for €100, so hopefully they will be something of a sleeper bargain😉
Shoog
I heard it said that these were made in the same factory as the siemens Klangfilm drivers which go for €1000+. These ones I got for €100, so hopefully they will be something of a sleeper bargain😉
Shoog
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
whatever you do - count that ~45C on surface of FC is safe ;
don't know above , considering type of ancient glues and VC former
don't know above , considering type of ancient glues and VC former
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
😉
no - 45C isn't that much
it's just 8C warmer than human body
edit - for illustration - just look at linked Klangbild auction
2420R FC , clearly written 250Vdc
that means scorching ~26W of dissipation .......
no - 45C isn't that much
it's just 8C warmer than human body
edit - for illustration - just look at linked Klangbild auction
2420R FC , clearly written 250Vdc
that means scorching ~26W of dissipation .......
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Sounds painful.
Your right 45C aint that bad really.
If I make the power supply adjustable it will be a suck it and see thing.
Shoog
Your right 45C aint that bad really.
If I make the power supply adjustable it will be a suck it and see thing.
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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