F2 with 12V supply

Ipanema

Member
2004-06-15 10:34 am
KL
Hi Mr. Pass,

Since I enjoy your F2 amp so much, I'm planning to build one for my car. May I know how much power can I expect with 12V car battery? Or which other current source amp of your design is more suitable for low supply voltage? FYI, I'm planning to match it with Fostex Fe-126/7 speaker.

Thanks a lot.
 

winslow

Member
2005-08-05 6:27 am
You are going to have to build some sort of switching power supply to get the + and - rail voltages...or use 2 batteries and reference power the opposite on one of the batteries, but you couldn't listen and charge the batteries while driving.

That and I don't think you have the proper space for those drivers to get any kind of lowend from them.

But I'm more of a car audio guy than a home guy, and those are my 2 cents.
 

Ipanema

Member
2004-06-15 10:34 am
KL
winslow,

Agree that SMPS is a better solution, but I do not have the experience building that. I'm thinking of using F2 in bridge mode in order to increase the output power if there is no other suggestions coming in.

The fostex will only provide midrange and high frequency at the front. Subwoofer at the back will supply the low end grunt. Is this feasible?

May I know why fostex is seldom use in car audio?

Thanks.
 

woody

Member
Paid Member
2002-01-15 12:57 am
Tyrone Ga. U.S.A.
I realy don't think the f2 will like operating on a 12 v supply.
Mosfets usualy need some voltage to operate best. If you look
at the capacitences of a mosfet they gets higher the lower
the drain source voltage and tend to get verry high below
6v.

I haven't heard of anyone building it but Andrew Cirnoff sp?
(one of my many spelling errors) had an interesting fet amp
for car use. It used an inductor as the current source. But
then geting a good 3a low dcr inductor at about 500mh is
another problem!
 

Ipanema

Member
2004-06-15 10:34 am
KL
I just browse through Passdiy website. It looks like ZV5 or Babo version of ZV5 might be suitable for use in 12V supply due to the almost rail to rail ouput swing. But I'm afraid that this design might clean up the 2nd harmonic that I so love in the F2. hhmm...dead end again...:bawling:
 

winslow

Member
2005-08-05 6:27 am
I put Mini-A boards into my Monolithic A501 heatsinks and power supply. PS needed a lot more filtering but sounded good...not that the A501s were bad to begin with.

But I wouldn't recommend doing that to such a hard to find amp like the Monolithic.

Maybe find another car amp that has the rail voltages you need and use it for the PS?
 

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
Well, the problem is that the FETs like to have some Drain-Source
voltage, like 4 volts or more. So most of the time we design the
supply at 4+V more than we want for peak swing, and this is just
throw-away voltage.

A car has a 13.8V supply. Subtract 8 volts, and you have 6
volts left, or 2V rms - less than a watt into 8. And that's ignoring
the drop across any Source resistors.
 

Ipanema

Member
2004-06-15 10:34 am
KL
Mr. Pass, may I know what's the reason to have 4+ volt margin for mosfet Vds? As for as I know, the upper swing is limited by RdsON of IRFP240 X bias current, which should be very minimal for large current.

Do you have any suggestion on how to migrate F2 sound into car?

Thanks for your inspiration. :)
 

Babowana

Formerly "jh6you". R.I.P.
2006-07-13 4:23 pm
www.aheadamp.com
Ipanema said:
... the reason to have 4+ volt margin for mosfet Vds?


For the operation outside ohmic region, I think . . .



:darkside:
 

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Ipanema

Member
2004-06-15 10:34 am
KL
Speaker recommendation

Build a DC/DC converter using an LT1680
Thank you. This doesn't look too complicated at first glance. I might give it a try. :)

Guys,

Can you recommend a speaker system that will work well with F2 in a car? I propose FE126/7 as front speaker and subwoofer at the back but was shoot down by the caraudio guys because they said Fostex are not built for car environment. At home, I love to listen to my Coral Flat8A in a big bass reflex enclosure. Any idea?

Thanks.
 
woody said:

I haven't heard of anyone building it but Andrew Cirnoff sp?
(one of my many spelling errors) had an interesting fet amp
for car use. It used an inductor as the current source. But
then geting a good 3a low dcr inductor at about 500mh is
another problem!


Winding such an inductor is sure possible, I have made something similar for a hefty power amp.


Magura :)