F5 power amplifier

[Nelson Pass]

Nelson, Which schematic editor do you use? I like the looks of your schematics. Sorry for OT but I bet other guys are a bit interested to.

We use PCAD 2006. It has been discontinued for several years.

 

[kacernator]

Feedback resistor 3W?

Hi,

I have searched the forum, but didnt find it. Does feedback resistors have to be 3W aren´t ordinary 0.6W enough?

Thanks.

 

[Zen Mod]

calculate dissipation , counting on 22V across them

 

[kacernator]

I would like to rebuild my older amplifier which is capacitor coupled to the output (has only one single rail PSU). What changes do I have to make to F5 schematics to make it work with single supply?

Thanks.

 

[Zen Mod]

not practical

 

[kacernator]

not practical

What does it mean?

 

[Zen Mod]

main virtues of F5 itself will be lost with single-sided supply

if you take a look at price of FW amps , taking in account also their price/quality ratio - you'll realize that skimping with main parts isn't a way to make amp of that quality

in any case - you're making it for small amount of final value

 

[kacernator]

I have simple mosfet non-NFB source follower PP in class A with single supply rail driven by tube preamp. And would like to convert the poweramp to F5 as I like the sound better. For me it is worthy to make the change, so if you can please be so kind and tell me what should I change in F5 circuitry to make it work with single supply rail?

Thank you.

 

[jacco vermeulen]

Amplifier is stupid.
Cap on input, cap on output, then make everything inbetween think it's still floating just above sea level (in Switzerland).

 

[Sangram]

I'm not sure the F5 is a suitable candidate for converting to single supply rail because of the twin feedback paths, and the high level of feedback itself (will need the half-supply to carry large currents).

May I suggest you look at alternative design from the F series, one of the other circuits already operates off a single supply with an output capacitor.

 

[kacernator]

Look at this schematics, it is also run from single supply and has two feedback paths.

 

[AndrewT]

Just copy post10731.

 

[kacernator]

Unfortunately that schematics has problem with thermal drift.

I am not an electrical engineer, but would F5 work with single supply rail just connecting two 10 Ohm JFET source resistors together and not to ground? Isn´t that all what is needed?

Thanks.

 

[AndrewT]

Look at the 4 MJE3x0. None of them are connected to Zero Volts.

 

[bobodioulasso]

Splitting the two rails supply by creating a virtual ground such as Quad used to do works also.

 

[JZatopa]

Hi,

is F5 good in reproduction for rock music mainly? If so, what preamp would you recommend? SS or tubes?

Thanks.

Rock sounds great on mine. I think any preamp will work. I would build the amp and just use what you have on hand.

 

[JZatopa]

Is 40000uf of capacitance per board to low? What is the lowest amount of capacitance you have used and how did the sound compare to using more capacitance? Just looking anecdotal info, not measurements.

 

[CanAm Man]

Is 40000uf of capacitance per board to low? What is the lowest amount of capacitance you have used and how did the sound compare to using more capacitance? Just looking anecdotal info, not measurements.

Depends, on several factors:

1 and 2. Bias level and Volume (both set the current level thru the PSU rails)

3. Acceptable (to you) PSU ripple, and therefore audible hum.

Difficult to quantify PSU cap size, unless you first quanitfy the three factors, above.

 

[tinitus]

I bet you can use 10.000uf, with no audible hum
but might get a bit hot with large constant current draw

 

[JZatopa]

Depends, on several factors:

1 and 2. Bias level and Volume (both set the current level thru the PSU rails)

3. Acceptable (to you) PSU ripple, and therefore audible hum.

Difficult to quantify PSU cap size, unless you first quanitfy the three factors, above.

1. Stock bias
2. stock 25Wrms is more then enough
3. No idea but I would prefer it to be un audible

It's hard to answer 3 when this is my first amp. I currently am using my F5 with a beefy 28-0-28 regulated PS that can put out 10amps continuous. I bought the gigawork F5 power supply because it was easy. It only has 40000uf per board (80000uf total). Before I finish the amp I want to make sure it isn't better to order some larger caps to replace what came with PS board.