F5 power amplifier

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#2,285
M&M Metals

I have been in touch with M&M metals regarding this profile.

http://www.mmmetals.com/extrusions/drawings/MK62430.jpg

I have a few quotes for 7" high sections and I am hoping to arrange either a group buy or even a group discount if they are willing to work with us. Also, ebayer Barredboss found Here ( http://myworld.ebay.com/barrredboss/?_trksid=p3911.c0.m198 ) is looking into designing a 12" extrusion. I am encouraging him to come to our forum and work with us directly through the vendors section.

Nick
 
#2,286
Hello everyone,

I finished my own F5 pcb layout based on Peters F4 pcb size and fet location. Since this is the first time I designed a board and have them professionally made I was hoping someone is willing to do a review of my design (specially the gerber files) before I have them made. It would be a shame if I ended up with a bunch of worthless boards. I've added the gerber files and diptrace file to the attached .zip file.

Help will be really appreciated!!

cheers,

c.
 

Attachments

#2,287
btw, this is what the pcb looks like right now

c.
 

Attachments

  • pcb f5.jpg
    pcb f5.jpg
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#2,291
rhysh said:
Also, i see this amplifier requires 24v rails. Do you think i would get away with 25v capacitors, as they are half the cost of 63v, and a lot smaller in size...
Click to expand...
NO!

what voltage appears on the output of the rectifiers if the mains voltage varies?
Here in the UK the tolerance is 216Vac to 254Vac. If you use a 230:18Vac transformer on the standard UK voltage it will measure ~18.8Vac when fully loaded.
On 254Vac it will measure ~19.9Vac when fully loaded. when unloaded these voltages will increase by the transformer regulation percentage. Big toroids can be as low as 3%, small EI can be as high as 30%. Find out the regulation of your transformer and adjust the output voltage assuming the PSU output fuses have blown and the caps are now charging up to the peak AC voltage going through the rectifiers.

Mains voltage variations can be surprisingly large and can overvoltage components if ignored. Measure and check, or easier, allow a margin on ratings for the variations that will occur.

BTW, electrolytics are available at many voltages between 25Vdc and 63Vdc, common available are 35V, 50V and less common 40V.

Finally, expect your PSU cost to be more than the cost of the amplifier and heatsinks.
 
#2,292
rhysh said:
...Do you think i would get away with 25v capacitors...
Click to expand...

You might, but only if you use well regulated power supply - but OTOH the voltage reg will cost you more than price difference between 25V and 35V or 40V caps. That's one of those "expensive savings" ...
:cannotbe:
Also, using components in "close to limit" area compromises reliability of the amp and makes the whole thing dangerous, so please think again 😉
 
#2,294
AndrewT said:

NO!

what voltage appears on the output of the rectifiers if the mains voltage varies?
Here in the UK the tolerance is 216Vac to 254Vac. If you use a 230:18Vac transformer on the standard UK voltage it will measure ~18.8Vac when fully loaded.
On 254Vac it will measure ~19.9Vac when fully loaded. when unloaded these voltages will increase by the transformer regulation percentage. Big toroids can be as low as 3%, small EI can be as high as 30%. Find out the regulation of your transformer and adjust the output voltage assuming the PSU output fuses have blown and the caps are now charging up to the peak AC voltage going through the rectifiers.

Mains voltage variations can be surprisingly large and can overvoltage components if ignored. Measure and check, or easier, allow a margin on ratings for the variations that will occur.

BTW, electrolytics are available at many voltages between 25Vdc and 63Vdc, common available are 35V, 50V and less common 40V.

Finally, expect your PSU cost to be more than the cost of the amplifier and heatsinks.
Click to expand...


Thankyou for the info, i have realised i can get the same part in 35V for not much more. I have decided on 2 x 100,000uf Rifa capacitors per rail, do you think this should be okay?
 
#2,297
Hi all.
I am a bit confused regarding the best voltage for rails, I seem to remember Mr Pass saying 25v rails are minimum and any lower every volt makes a difference, but then everybody uses 18v secondaries which after rectifiers, voltage drop etc gives approx 23.5v rails. Why not use 20v secondaries or even 22v ?
What have I missed ?
Thanks.
 
#2,298
jotom750 said:
Hi all.
I am a bit confused regarding the best voltage for rails, I seem to remember Mr Pass saying 25v rails are minimum and any lower every volt makes a difference, but then everybody uses 18v secondaries which after rectifiers, voltage drop etc gives approx 23.5v rails. Why not use 20v secondaries or even 22v ?
What have I missed ?
Thanks.
Click to expand...

I don't think he said minimum of 25V. The amplifier works best with 24 volt rails. Try to get as close to 24V as possble. If the voltage is too high it will probably have to dissipate more heat, and may not sound the same.
 
#2,300
Re: low sound

umut1001 said:
hi..today i built f5 amp with huge heatsinks..i used 2sk1530 and sj201. bias is 1,5a and i see 2,83volts on r3 and r4..but the sound is very low.my soundcard is emu1212m and has enough output.what is the problem? i couldnt solve it
Click to expand...


I would check it with a function generator and a scope before hooking it to a source and speakers.
 
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