Hmm...
I'am not intersteed in modifing the kit board , i'am interested in a simple voltage reg for 40 V or what resistors i have to add on the 55 + 55 - rails to decreas at 40 V + and 40 V - , i assume the resistors should have a big wattage but .. i don't know the value and wattage .
Thanks
I'am not intersteed in modifing the kit board , i'am interested in a simple voltage reg for 40 V or what resistors i have to add on the 55 + 55 - rails to decreas at 40 V + and 40 V - , i assume the resistors should have a big wattage but .. i don't know the value and wattage .
Thanks
Re: Hmm...
I doubt you will be successful with resistors. The current drain from the PS will be dependent on output power (which fluctuates a lot). Using resistors essentially turns a good PS in to a very bad PS.
As to regulated power supply, a linear regulated PS will require a lot of heatsinking in this case (think about how to dissipate 7ax15v), and as will most regulated power supplies, transient responsess suffer big time.
One (far less than optimal or even desirable) is to use a switching supply for this. I am not aware of one off-the-shelf product to handle your situation but I am sure you can get a switching controller and stack a mosfet to it to make it work. Alternatively, you can build one. One idea is to use a mosfet as a switch to charge up (or cut off as the situation maybe) the output rail. but I haven't sketched out it.
If you don't want to touch the amp, your best bet is to get another transformer.
darkm4n said:
I doubt you will be successful with resistors. The current drain from the PS will be dependent on output power (which fluctuates a lot). Using resistors essentially turns a good PS in to a very bad PS.
As to regulated power supply, a linear regulated PS will require a lot of heatsinking in this case (think about how to dissipate 7ax15v), and as will most regulated power supplies, transient responsess suffer big time.
One (far less than optimal or even desirable) is to use a switching supply for this. I am not aware of one off-the-shelf product to handle your situation but I am sure you can get a switching controller and stack a mosfet to it to make it work. Alternatively, you can build one. One idea is to use a mosfet as a switch to charge up (or cut off as the situation maybe) the output rail. but I haven't sketched out it.
If you don't want to touch the amp, your best bet is to get another transformer.
Resistors won't work unless your load has a constant current
consumption, since the voltage drop over the resistors will
vary with the current according to Ohms law. I understand
the kit is a power amp, so presumably you don't really need
a regulated supply. The simplest solution then is probably
to use an emitter follower to drop the voltage and use a
zener diode to set the output voltage.
Anyway, whatever method you use, you will have to drop
15V, which means you must disspate 15W per Ampére. Are
you sure you want to do that? For high power the best
solution is to get another transformer that has the correct
voltage.
consumption, since the voltage drop over the resistors will
vary with the current according to Ohms law. I understand
the kit is a power amp, so presumably you don't really need
a regulated supply. The simplest solution then is probably
to use an emitter follower to drop the voltage and use a
zener diode to set the output voltage.
Anyway, whatever method you use, you will have to drop
15V, which means you must disspate 15W per Ampére. Are
you sure you want to do that? For high power the best
solution is to get another transformer that has the correct
voltage.
The schematic I posted is the best I've found for high current and high voltage regulation. If you can't find the 1k trim pot I would hestitate to build any high power project though. These are deadly power levels! 
The 350w is obtained by bridging the two channels of the amp. I still think it is on the optomistic side! Remember to use only 8 ohm speakers as a bridged amp see it like a 4 ohm load.
The 350w is obtained by bridging the two channels of the amp. I still think it is on the optomistic side! Remember to use only 8 ohm speakers as a bridged amp see it like a 4 ohm load.
Ok
That 1 K trim pot it's a simple pot , but it's small , right ?
Like this one ? http://www.vitacom.ro/pictures/cerm.jpg
On .. how many amp's can handle that voltage reg ?
That 1 K trim pot it's a simple pot , but it's small , right ?
Like this one ? http://www.vitacom.ro/pictures/cerm.jpg
On .. how many amp's can handle that voltage reg ?
darkm4n, forget all about voltage regulators.
You have these options:
1 Analyze the amp if it's possible to use it at +- 50 V (maybe with modifications). 50 volts aren't very high so I see not so big problems to make it work at this not very high voltage.
2 Change transformer
3 Choose an another amp or amp design
You have these options:
1 Analyze the amp if it's possible to use it at +- 50 V (maybe with modifications). 50 volts aren't very high so I see not so big problems to make it work at this not very high voltage.
2 Change transformer
3 Choose an another amp or amp design
Christer said:
darkm4n,
If this is a toroid xformer, wind some wire on it, and put that in series with the primary. Depending on the phase, you either get MORE or you get LESS sec voltage. Test is with the bare xformer, not connected to anything on the sec side. Make sure you use isolating tape before and between windings. Start with say 20 windings to determine the amount you need. After you're done, isolate it again, this is mains live voltage.
Now, this is possible, but with all due respect, following this thread, you need to decide whether you are really ready to tackle a high-power bridged amplifier. I would advise you something less powerfull and less complex. Why not try one of the ZENs? There are many people doing that so you will have expert advise at every step.
Jan Didden
Info ....
The regulator schematics posted previously looks like it should go down to ~36V
so in theory it should work. There are also more simpler requlator circuits than
this, that could also do the job, but with fewer components (and with poorer
regulation - not such a problem for an amp designed for unregulated supply).
The downside with requlators like this, as pointed out by Christer, is the power
dissipation. At worst case, with a load current of 7A and 15V drop accross the
regulator it would dissipate ~100W of power per supply rail !!! You would
need an enormous heat sink to keep the tempature down. I would guess you will need
a force (fan) cooled heatsink if you took this route.
You may well find a new transformer is the lower cost option ...
As an alternative, if you have not already bought the amp kits, find an amp that
will work up to +/- 55 V supply - this should not be a problem .....
Dave
The regulator schematics posted previously looks like it should go down to ~36V
so in theory it should work. There are also more simpler requlator circuits than
this, that could also do the job, but with fewer components (and with poorer
regulation - not such a problem for an amp designed for unregulated supply).
The downside with requlators like this, as pointed out by Christer, is the power
dissipation. At worst case, with a load current of 7A and 15V drop accross the
regulator it would dissipate ~100W of power per supply rail !!! You would
need an enormous heat sink to keep the tempature down. I would guess you will need
a force (fan) cooled heatsink if you took this route.
You may well find a new transformer is the lower cost option ...
As an alternative, if you have not already bought the amp kits, find an amp that
will work up to +/- 55 V supply - this should not be a problem .....
Dave
) Good advice !!! LIKE IT !!!
Jan, I think your advice isn't so good, because this is typical safety issue and our gentleman seems not to be the person for such activities, sorry darkm4n.
The transformer has approx. 0.3 volts per turn and it requires lots of turns in order to reduce the voltage, also rather thick wire, not very easy.
The transformer has approx. 0.3 volts per turn and it requires lots of turns in order to reduce the voltage, also rather thick wire, not very easy.
Ok ..
Ok , thank's all of you , i think this is the right way to do it ..
It's that affecting the xformer Amps ?
Ok , if i use isolated wire , if there any chance i can distroy the toroidal ? If i wind to less or to much ??
I was winding the secondary of a tesla coil and i have to admit it's very nasty ...
Ok , thank's all of you , i think this is the right way to do it ..
It's that affecting the xformer Amps ?
Ok , if i use isolated wire , if there any chance i can distroy the toroidal ? If i wind to less or to much ??
I was winding the secondary of a tesla coil and i have to admit it's very nasty ...
Best way would be to get another torodial...mod the amp to accept your higher voltage...or unwind some stuff outta the trao...try not to use some phase cancelling stuff...looks messy and is messy...best would be to get a new trafo if you are afriad...but I think the amp can handle higher volatges without major problems...best to be careful and try it out first though...
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