You might find this thread interesting and helpful.
https://www.diyaudio.com/community/threads/f5x-the-euvl-approach.183362/
Or this:
https://www.diyaudio.com/community/threads/f5x-the-euvl-approach-the-build-thread.208880/
Rush
F5X -- the EUVL Approach
https://www.diyaudio.com/community/threads/f5x-the-euvl-approach.183362/
Or this:
https://www.diyaudio.com/community/threads/f5x-the-euvl-approach-the-build-thread.208880/
Rush
In a F5 Turbo for 100 watts, I think you need to start at about 44 rail volts (accounting for the -4 volt loss) and 2.5 amps current into an 8 ohm load. 4 ohm load would need to increase bias to 3.5 amps.
100 watts @ 8 ohm = 220 watts; 4 ohms 100 watts = 308 watts dissipation.
I may have this wrong, but in a balanced F5X you still end up dissipating the same watts, but each have (balanced is a F5 times 2) can run at half the voltage. So the you need 24 volt rails (you lose the same -4 volts) and run at the same current, 2.5 or 3.5 amps.
Where I am confused is, in the F5X each F5 amp sees half the load??? so a 8 ohm speaker appears as a 4 ohm load to each half of a F5X?
I think you will run out of heatsink before you get 100 watts in pure class A into a 8 ohm load. It will happily give you 100 watts in class AB though.
Rush
100 watts @ 8 ohm = 220 watts; 4 ohms 100 watts = 308 watts dissipation.
I may have this wrong, but in a balanced F5X you still end up dissipating the same watts, but each have (balanced is a F5 times 2) can run at half the voltage. So the you need 24 volt rails (you lose the same -4 volts) and run at the same current, 2.5 or 3.5 amps.
Where I am confused is, in the F5X each F5 amp sees half the load??? so a 8 ohm speaker appears as a 4 ohm load to each half of a F5X?
I think you will run out of heatsink before you get 100 watts in pure class A into a 8 ohm load. It will happily give you 100 watts in class AB though.
Rush
I'm not familiar with those terms, but are you talking about something like this...
https://www.digikey.com/en/products...ND5OqHBznEqrCoS2MduwQNsnPzblKXVRoChPoQAvD_BwE
Just for example... I don't know what sizes the PCB holes might be or the wire diameter you intend to use.
Either way... that may get you started.
https://www.digikey.com/en/products...ND5OqHBznEqrCoS2MduwQNsnPzblKXVRoChPoQAvD_BwE
Just for example... I don't know what sizes the PCB holes might be or the wire diameter you intend to use.
Either way... that may get you started.
A free good diy solution is to use leftover stripped leads of 3/5 watt resistors. Cut small pieces, strip small wire covering, insert one end of lead into wire and solder the exposed end with excess solder. Apply good amount of solder to both sides of hole, heat the solder and simply insert the lead into pcb hole and solder the joint. Make sure wire touches the solder pad from top and is soldered well to top of the pad. This will keep lead from bending and breaking. Solder joint at bottom will keep the wire from pulling the copper trace off the board.
Hello,
I wanted to do some routine checks on the F5-Turbo power amp, and to my amazement I saw that the multimeter couldn't read the offset values on the left channel of the power amp correctly, it was oscillating continuously in a range between -65mv and +35mv, I reset the trimpot values on the FE board and re-calibrated the bias to values around 300mv (I can't get them any higher), but the multimeter couldn't read the offset correctly, it always reads values between -50-60mv and +30-35mv.
I measured the AC voltage at the output terminals of the left channel and the multimeter reads a stable AC voltage of 10V, while on the right channel the bias and offset values are within the normal range.
I don't understand what could have happened.
What do you think?
What is the source of the problem?
I wanted to do some routine checks on the F5-Turbo power amp, and to my amazement I saw that the multimeter couldn't read the offset values on the left channel of the power amp correctly, it was oscillating continuously in a range between -65mv and +35mv, I reset the trimpot values on the FE board and re-calibrated the bias to values around 300mv (I can't get them any higher), but the multimeter couldn't read the offset correctly, it always reads values between -50-60mv and +30-35mv.
I measured the AC voltage at the output terminals of the left channel and the multimeter reads a stable AC voltage of 10V, while on the right channel the bias and offset values are within the normal range.
I don't understand what could have happened.
What do you think?
What is the source of the problem?
Here is what 6L6 says about oscilation in his most excellent build guide for the f5t v2/3. I used 470 ohm gate resistors on my build.
"Also, in my opinion, C3 and C4, labeled here as ‘OPT’, are required for stability from destructive oscillation. This is a very high bandwidth design and those caps help protect it from ultrasonic HF oscillation. Use 1000pF. Also, if oscillation is a problem for your build, increase the value of the gate resistors (R13 -16 and similar) any value from 47.5R to 680R will work and sound fine, the higher the value the more damping occurs."
I checked the P-ch and N-ch boards, the capacitors
c3-c4 are there and have a value of 1nF, so OK, while resistors R13-R16 are 47.5 Ohm, I will replace them with 1/2W 470 Ohm, following your advice, resistor R11 2k2 ohm is not present, I will also install this.
I hope to solve the problem.
Of course I will also perform the same operations on the other right channel.
Thank you.
c3-c4 are there and have a value of 1nF, so OK, while resistors R13-R16 are 47.5 Ohm, I will replace them with 1/2W 470 Ohm, following your advice, resistor R11 2k2 ohm is not present, I will also install this.
I hope to solve the problem.
Of course I will also perform the same operations on the other right channel.
Thank you.
Hello everyone!
I'm currently in the process of integrating the current limitation from the F5 into another F5 iteration from the Nelson universe.
A question about this:
Dad talks about the involved resistors R16-R19 in the article:
"You can remove the current limiting (Q5, Q6, R15 to R18 of the original)..."
But what are the resistors R19/20 used for?
(In the original F5 these are the resistors R21/22)
In the simulation (micro-cap) it also works without these resistors, but R17/18 (R19/20 in the original) have to be adjusted.
In the simulation, nothing changes in the gain without these resistors.
Maybe some kind of negative feedback?
Have a good time!
Mike
I'm currently in the process of integrating the current limitation from the F5 into another F5 iteration from the Nelson universe.
A question about this:
Dad talks about the involved resistors R16-R19 in the article:
"You can remove the current limiting (Q5, Q6, R15 to R18 of the original)..."
But what are the resistors R19/20 used for?
(In the original F5 these are the resistors R21/22)
In the simulation (micro-cap) it also works without these resistors, but R17/18 (R19/20 in the original) have to be adjusted.
In the simulation, nothing changes in the gain without these resistors.
Maybe some kind of negative feedback?
Have a good time!
Mike
Assuming you're talking about the divider that's feeding the I(lim) transistors:
The ratio of the resistors defines the point at which the current limit transistors begin to conduct. You can calculate it theoretically. The transistors conduct at 0.6V Vbe, and the voltage across the combination is (from memory) [R(dsource) x I(out)].
The ratio of the resistors defines the point at which the current limit transistors begin to conduct. You can calculate it theoretically. The transistors conduct at 0.6V Vbe, and the voltage across the combination is (from memory) [R(dsource) x I(out)].
I built an F5V3 in 2017 as monoblocks with a 47v PS and it puts out about 120w into 8 ohms. It will do about 400 into 2 ohms. Big power supplies! I used an Jensen input transformer to get a balanced input. I have them biased for about 60 or so watts class A at 8 ohms - I’m dissipating about 90w / heatsink. The transformers are easy to implement and give you freedom from ground loops for both balanced and SE inputs. They have some other benefits as well. See Pg 238-240 in this thread if you want to see what I built.
Hi
I just made F5T V1 with +/-32V rails and got best dc offset around 10mVdc but its problem came from when I run over 30Wrms. My protection circuit start and then I measured dc output it shown 1.5Vdc ! I used matched pairs JFETs K170/J74 at 10mA and also used matched quad MOSFET 240/9240. Normally VGS of MOSFETs are N 4.9Vdc, P-4.9 Vdc for total 2A biased a channel. But I saw VGS gone to N 5.2Vdc, P -4.9Vdc when dc came out. How do I fix this problem ?
Thank you
I just made F5T V1 with +/-32V rails and got best dc offset around 10mVdc but its problem came from when I run over 30Wrms. My protection circuit start and then I measured dc output it shown 1.5Vdc ! I used matched pairs JFETs K170/J74 at 10mA and also used matched quad MOSFET 240/9240. Normally VGS of MOSFETs are N 4.9Vdc, P-4.9 Vdc for total 2A biased a channel. But I saw VGS gone to N 5.2Vdc, P -4.9Vdc when dc came out. How do I fix this problem ?
Thank you
It’s a good thing you had DC offset protection! Was the offset stable when you ran the amp without a signal? Seems like it could be a thermal issue to me. What could be happening is that the P and N mosfets are running at different temperatures. Just how hot are you running the output stage? Over 30w/device is pushing into thermal considerations to where you need to take great care of all the details to maintain reliability. Check to be sure all thermistors are making good thermal contact with the mosfet. Use thermal compound to help with that. If not, readjust them and re bias the output stages. I would check the mounting bolts for the mosfets to make sure they are all at roughly the same torque. You are also running 10ma Jfets at 32 volts so they may be running hot as well, which could cause an offset issue.