F5 power amplifier

hi all
im just about to start building my f5 x2 and am thinking about installing output caps/inductors to them so i dont have to use a crossover

they will be used to biamp a 2/way system and will be run through a goldpoint passive pre and the crossover point is 300hz

what are the plus and minus,s of this method and how do i implement things like baffle step,notch filters and the like

ive seen this method mentioned before and its got me curious

regards sheafer
 
slr 5000 said:
hi all
im just about to start building my f5 x2 and am thinking about installing output caps/inductors to them so i dont have to use a crossover

they will be used to biamp a 2/way system and will be run through a goldpoint passive pre and the crossover point is 300hz

what are the plus and minus,s of this method and how do i implement things like baffle step,notch filters and the like

ive seen this method mentioned before and its got me curious

regards sheafer

Can't tell if that is or isn't the best way to do it, but I'm also interested to see where will this get you. I am about to finish my 4 channels and will play a bit wit a Behringer active crossover to find the best frequency and steepness to combine my ESLs with the OB LA... I was also thinking about the 250-350Hz region but would rather either go active or even better, passive... However, if there is a better way to do this, what a heck, why not?

:D
 
hi Babowana,
Thanks for your sharing, is this your own design?
i was refering to Rod Elliot article
" http://sound.westhost.com/project15.htm "
i do not know much more about this topic.
I am a bit lost with your schematic: you are using big caps at the outputs. Elliot says " I do not recommend more than 4,700uF, as the charging current will be very high."
Rod Elliot uses a darlington, the gain of which will multiply a small cap in its base circuit, you use only one mosfet instead.
I thought that one among the advatages of a C.M. was the possibility
to use smaller normal caps.
Could you lighten me about this?
 
hi mate
i have seen a few mention it before on diy but i have never really pursued it until now

in theory it would be great say one amp is only allowed to pass up to 300hz and the other from 300hz up

in my case it would run a 2way with the ss 25w/8565 on base crossed to my mangers from 300hz up

it seems simple in theory but there must be more too it
otherwise why would anyone bother to use a crossover when you could just have an amp for each frequency range
 
slr 5000 said:

it seems simple in theory but there must be more too it
otherwise why would anyone bother to use a crossover when you could just have an amp for each frequency range

Some twenty years ago, I was fiddling with a very simple RC combination in front of my homebuilt Quad 405 replica to be able to use it as a subwoofer amp. Can't recall the exact way to calculate the elements now (I'm at work now, no access to private docs) but since the F5 has no caps in the way of the signal, some would be required to create a high and low pass filters and because the amp is so simple, I would prefer not to spoil it with fiddling inside the topology. Since F5 needs a gain stage anyway, I'd rather focus on building a preamp with properly calculated RC networks and implement those around one or two active stages that provide the required gain. With some skill and luck, it would easily run from the main PSU (+/-24V) and be integrated within the same housing neatly tucked in at the input jacks... Furthermore, the resistor(s) in the RC section could be adjustable/variable potentiometers to adjust or fine tune the exact value for desired frequencies. In such systems, it often comes to the problems with delay/phase shifting so, either have to implement a switch or phase shifting or... well, not so simple when you get to the implementation. That is why I would rather not spoil this amp, I need at least one component in the system to be a reference point ...


:cool:
 
so a a preamp with multiple outlets ?

with each outlet assigned a certain frequency range

say output 1 bass amp
output 2 mid amp
output 3 high amp

hmm this has got me thinking instead of putting caps and such on the amp output build a good diy pre from an existing design and modify it to have say 3x or 2x outputs with each doing a certain frequency band

i suppose it would be easyer to just get a active crossover board like the elliot sound one and build it into a case with a diy pre and have them share a common powersupply
 
Formerly "jh6you". R.I.P.
Joined 2006
bobodioulasso said:
hi Babowana,
Thanks for your sharing, is this your own design?
i was refering to Rod Elliot article
" http://sound.westhost.com/project15.htm "
i do not know much more about this topic.
I am a bit lost with your schematic: you are using big caps at the outputs. Elliot says " I do not recommend more than 4,700uF, as the charging current will be very high."
Rod Elliot uses a darlington, the gain of which will multiply a small cap in its base circuit, you use only one mosfet instead.
I thought that one among the advatages of a C.M. was the possibility
to use smaller normal caps.
Could you lighten me about this?


No, the capacitance multiplier itself was not my idea. I just used it for my F5. When I built F5, I wanted to have the rail voltages of about 24V. But, that time I had nothing but the transformer of 500VA EI type with 2x25VAC secondary. So, I was wondering how to get the 24V rails from the 2X25VAC secondary, and finally I ended up with the method as shown to you.

I made C1 and C2 filters with 33,000uF, which were followed by the capacitance multipliers, and then followed by C3-C6 of 33,000uF. I made C3-C6 big to have the supply rails as better AC signal ground because the output impedance of the capacity multiplier (mosfet) is not zero.

Not insisting, but just informing for you . . .

>:)<
 
chassis thickness

Nelson,

A machinist friend is helping me build the chassis for my amplifiers. What thickness is good for a bottom plate supporting a 1kVA Plitron that is dimensioned at 15.9375"x14"?

I was going to go .125", but thought I would ask you and the community first.

Thank you in advance for any and all help,

Chris