F5 power amplifier

[jackinnj]

Originally Posted by AndrewT

if I were designing a CLC for an F5, I would use 6m8F//6m8F//6m8F as the first capacitor bank, then 180turns of 1.6mm diameter enameled copper on a 48mm air core former (700gms of copper) and then 15mF//15mF//15mF as the second stage capacitor bank.

Here's a simulation of a 2mH choke and a 200uH choke -- switching the load between 1A and 3.3A -- 800uS/200uS

[tinitus]

Hi

Here is my new F5 layout with triple outputs
I do have both PDs and CVs F5 boards, and looking at them has helped me some
Still, I like a challenge

Do you think this will work ok
Or is there somethindg that needs changed

btw, Amplimo makes 2x18V, 2x20V, 2x22V trafos

[ichiban]

Originally Posted by tinitus

Hi

Here is my new F5 layout with triple outputs
I do have both PDs and CVs F5 boards, and looking at them has helped me some
Still, I like a challenge

Layout

[tinitus]

Originally Posted by ichiban

Layout

Yeah, it slipped but corrected
Please just give your honest opinion
No need to be gentle on me, even if its my first

btw, its supposed to be a hybrid/semi hardwired build

[CBRworm]

Just out of curiosity, what is your goal for bias current over each device?

[tinitus]

Not sure
I may adjust according to heatsinks
Does 0.6-0-0.7A pr device make sense
My goal is not so much higher wattage, but more to avoid power losses in lower impedance

see yo later

[CBRworm]

Could be, I am still trying to find the ideal.

I did my setup with 2 pairs of outputs per F5 channel. I was hoping to bias them at about 1 amp per device, but I ended up at about .8 amps per device before my rail voltage sagged too much - my goal was to stay in Class A throughout the useful range of my highly reactive, less than 4 ohm speakers and get the damping factor up as well. I ended up having the power supply voltage drop a bit as I raised the bias, effectively bringing my power potential down. I had to piggyback a couple more resistors in the power supplies to get the voltage back up a bit, and added some more capacitance to get keep the ripple down, but I ended up with +/- 18 volts instead of +/-24 at the rails. This is with 18-0-18 400va toroid.

I am going to get a higher power transformer and try to get the rails back up to +-22 (or 24) volts and then try again. This is a lot of heat to deal with as well. With the stock value of 1.2 amps per device and a total of 4 devices, everything runs pretty cool compared to 8 devices at .8 amps. with everything biased higher I have to have forced air blowing over the large finned rectifier heatsink to keep it below 70c.

For testing I have one channel set up with .6 amps across each device and one channel with 1 amp across each device trying to see if I can tell a difference in any musical situation. So far I can't tell a difference, but I think that my weakest link is not the amplifier.

Both channels measure well with the measuring software/hardware I have. They have not ever tested identically though.

[Melon Head]

Originally Posted by tinitus

Hi

Here is my new F5 layout with triple outputs
I do have both PDs and CVs F5 boards, and looking at them has helped me some
Still, I like a challenge

Do you think this will work ok
Or is there somethindg that needs changed

btw, Amplimo makes 2x18V, 2x20V, 2x22V trafos

I have already done this, see post number #5047 on page 505.
It ran extemely well. You shouldn't have any problems what so ever.
As a comparison it performed significantly better than a Naim amp.

[Melon Head]

Hi cbrworm.
I am guessing you used crc in the power supply. If you want to up the voltage without the need for a new transformer then remove the resistors.

[tinitus]

Originally Posted by Nelson Pass

Really not a problem. Just match them up a bit, increase
the Source resistance, and go to town.

Occasionally you will have to think about compensation,
but a cap on the feedback loop resistor will pretty much
take care of it.

Nice respond from Nelson upon my question about multiple outputs

Well, I have some not so clever questions

1. Well, which is source resistor ?
2. And raise value by how much ?

3. Cap on feedback loop resistor, which is that ?
How big a cap ?
4. Power resistors 5,6,7,8, from input to output
They are double 100ohm, is that because they need to be 6watt or just
fore adjustment of value ?
5. Power resistors between supply line and power transistors
Why only 3watt resistors ?