F5 power amplifier

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G

gaborbela

Member
Joined 2005
Hello
Bigger transformer than necessary mostly waste of money .
To me big capacitors always worked fine, like 66 000uF or so. Even I used 400 000uF Mallory in my Aleph X with a smaller 50 000uF Philips capacitor..
I think more important the capacitor quality .. We can find lot of small capacitors like 10 000uF or 4 700uF they have bad sound.
Again the quality of the capacitor U use effect more the sound of the amp than the uF size.
These opinion based on my experience... Al do these is a area in DIY were many different opinion.
Greetings
 
A

AndrewT

R.I.P.
Joined 2004
JimM said:
Heat sink USA has a sink with 2in fins and 10in by 7 in which they claim E=C\W\3in of 0.80, so I'm assuming the 10 by 7in sink would be around 0.4, if E is a linear function to size. Has any one used one of these sinks for a single channel F5 and do you think it is sufficient. Any help is appreciated.
Thanks
Click to expand...
hi the dissipation capability is roughly proportional to the square root of the height.
and proportional to the width.

Starting with a 10w * 3h with Rth s-a = 0.8C/W.
using 20w * 3h gives ~0.4C/W
using 10w * 12h gives ~0.4C/W

note: the tall version is roughly twice as expensive and twice as heavy.
 
M

Marra

Member
Joined 2009
Paid Member
This morning I connected up the 2nd channel of my F5 but before plugging it in I decided to check that P1 & P2 were at zero ohms. On one channel both settle at 3.3R whilst the other one gives readings fluctuating between 50 & 60R; this is the pcb I fired up yesterday through the light bulb tester and which had 0.5V on its output.Can anyone please suggest what might have gone wrong. When it was plugged in yesterday nothing smoked although I only had it on for a couple of minutes.
TIA Marra.
 
cviller

cviller

Member
Joined 2005
It is really hard to measure those pots reliably when they are in a circuit with active devices. What I normally do is to measure both ways (yes, the resistance meter is often directional), so with a bid of fiddling, you'll know what way to turn the screws to get the pots down to the lowest value. You cannot measure their absolute value in circuit.
 
M

Marra

Member
Joined 2009
Paid Member
Thanks Christian. I have P1 & P2 such that ccw lowers the resistance and all are fully ccw. As my knowledge is somewhat limited I wondered why the channel which had not been powered up gave low steady readings whilst the other one which had won not settle. Do you suggest that I plug the amp in again with the light bulb and check voltages again?
Another question if I may. I am using a soft start circuit which when connected through the bulb takes 2-3 goes before latching on [ it does not do this when directly powered]. Could this damage anything?
TIA Marra
 
cviller

cviller

Member
Joined 2005
I have not followed your power up quest, but the bulb test can only tell you if you have shorts in the system - what rail voltage do you get with bulbs in? Did you get any current through the 0.47 power resistors?

Relay flickering is not a good thing if a lot of current is involved, but it is probably not a major issue.
 
M

Marra

Member
Joined 2009
Paid Member
Yesterday when I powered up one channel I had p/s voltages of +-24.2V but had a reading of 0.5V across the speaker terminals which threw me. As I had the bulb tester connected I did not attempt to adjust anything. I had not shorted the input; would this matter? The bulb was not glowing at all.
 
T

tinitus

Ex-Moderator R.I.P.
Joined 2005
A

AndrewT

R.I.P.
Joined 2004
Marra said:
Another question if I may. I am using a soft start circuit which when connected through the bulb takes 2-3 goes before latching on [ it does not do this when directly powered]. Could this damage anything?
Click to expand...
yes.

A timer for bypassing the delay relay will not be affected by the bulb tester.
An RC charge circuit used as a delay must be disabled.

The bulb tester is there to prevent damage if you make silly mistakes.
You use it to check the wiring to the transformer.
Then you use it to check the transformer and the wiring to the rectifiers.
Then you use it to check the transformer and rectifiers and the wiring to the smoothing capacitors.
Then .........
Eventually all the wiring has been checked.
All the voltages have been checked. Then it's time for a direct to mains start up. STOP. This is when you need the soft start.
When this is tested you can bias the amplifier.
 
W

Woody1911a1

Member
Joined 2010
i need to solder !!!!

hey guys , i spend my days working and my nights reading these forums searching for audio nirvana . actually it's the search / journey that i look forward to .

diyaudio is my new journey . i just recently built Peter Daniels excellent 3875 chip amp and loving it . however my soldering station sit's silent soooo ... i'm off on a new quest the F5 .

i've got two tabs of the f5 thread going . one starting at page one , the other starting at page 1016 reading backwards :) much going over my head while absorbing so much that's new to me .

i've got the diyaudio/cviller boards on the way and about to order the Tech DIY Company Store .

so now to the question . the power supply ? so far in my reading saying use the zen not the aleph . then one saying he was using the peter daniels . assuming the basic 8 diodes per basic . can you aim me in a direction as i finish reading the rest of the 1016 pages ? a pcb available or build the original from http://www.firstwatt.com/pdf/prod_f5_man.pdf using perfboard ?

any comments or advise on my direction is very welcome .

thanx in advance :)
 
6L6

6L6

Moderator
Joined 2010
Paid Member
The Peter Daniel's PSU board will work, although you need to use 33,000uf caps (to get the stock amount of capacitance) because there is only pads for 2 caps per rail. There is room for the (4) .47ohm resistors, and the bleeder. You can use the rectifier board (included) for diodes similar to MUR3060, or just snap the section off and use rectifier blocks like the factory FirstWatt offerings. I am using it, and there are examples of many F5 built with it.

More info on the board - http://www.diyaudio.com/forums/audio-sector/149672-universal-power-supply-pcb.html

I am a huge advocate for simplicity, and it's very simple to use a good PCB like the Daniels PSU board.
 
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cviller

cviller

Member
Joined 2005
Hi woody, I still have some psu boards available (cviller order site), but you can also solder a nice psu on perf board. The psu for F5 is really simple, but you should look around for the capacitors, as they are often hard find for a good price. Do you prefer snap-ins or screw mount?
There is a guy in the states selling antek transformers on ebay and possible also here - if you haven't already found the one you need.
 
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