I'm thinking of building this or something very similar using the 4U/400Deluxe case. I realize 5U is recommended to get to 50watts. Could I use two 4U cases ( which I already have ) and break the design into two sets of boards? ( 1 for each case ). I really had my heart set on having 1 amp power each speaker, but the speakers I ended up getting don't have bi-amp inputs. ( I was originally going to use two F5m in bi-amp config. ) So I'm looking to parallel or bridge into 'monoblocks' and get 50watts per side. I could spin up my own boards if needed, and can share those too.
I did start to work on a mono version which would be good for a 4U 300m and the 400m case. If you want to be the guanae pig, I can arrange for that. I probably have a few more hours of work to do for that PCB set.
The power supply will be a bit smaller to accommodate the 300mm depth. The original would work for that but it would be a bit tight.
To be honest though, the stereo version works great and leaves the extra chassis available for another cool project. It will work just fine in a 4U/400mm chassis.
The power supply will be a bit smaller to accommodate the 300mm depth. The original would work for that but it would be a bit tight.
To be honest though, the stereo version works great and leaves the extra chassis available for another cool project. It will work just fine in a 4U/400mm chassis.
That's great! I have two AS-3218 transformers ( one of which is in my current F5m ) and have the vertical L brackets for them. Since I already have the 4U/400mm case I could see how it all dry-fits and then worry about getting a 5U if needed.
I could use the 4U/400mm case in a stereo config instead of two 'monoblocks', but do you thin the heatsinks are large enough to dissipate the 50+watts? I'm guessing you would have 1 amp board per heatsink still?
I could use the 4U/400mm case in a stereo config instead of two 'monoblocks', but do you thin the heatsinks are large enough to dissipate the 50+watts? I'm guessing you would have 1 amp board per heatsink still?
I used a 4218 transformer for the initial test which worked well. It was pretty undersized but did the job for the initial testing. I even had it biased to about 50w a channel... The 22vac 800va transformer worked a lot better and resulted in a 26.5vdc rail voltage.
I think your heatsinks would be large enough to dissipate 35-40 watts which should work pretty well.
I think your heatsinks would be large enough to dissipate 35-40 watts which should work pretty well.
So if I understand correctly, my F5m puts out around 35watts per channel with the 4U/400mm case/heatsinks? If I bridge 2 channels together, do I get over 50watts? I can get larger heatsinks if needed. ( and new cases )
The original F5m puts out whatever the mosfets can tolerate in regards to the heat they produce. That probably sits at around 30-35w per channel. If they were a First Watt product, I suspect Mr. Pass would have just called it a 25 watt amp.
I have had the F5mX biased anywhere from 35-65 watts per channel and the sound doesn't change all that much with bias.
In your 4U 400mm, I suspect the heatsinks can tolerate 35-40 watts a channel and be below say 55C. But I haven't calculated that...
If you take two original F5m amplifiers and tie them at the feedback, then you are getting pretty close to this F5mX. With that being said, the F5mX is already bridged. So it kind of is what it is in that regard. But with the 4 mosfets on the output stage per channel, it can make 50 watts very comfortably in class A.
What I would consider is trying the amp in stereo mode to make sure you like it. If you do, then try making monoblocks out of it. Again, I do have it on my list to make a set of mini monoblock PCBs. Basically this stereo kit severed into two. So instead of one output supply board with two phases on it, it would be two boards each with their own phase. One on each side of the chassis. I think this would make a cute little 4U 300mm Monoblock. They would hit the 50 watts and you can have your monoblocks sitting next to the speakers with a short speaker cable which is kind of nice. You would step down to a 400VA transformer.
Another change would be the amount of caps. I would want to make the cap bank smaller. So instead of 24 caps, I would use 18 caps. Which is three rows of 6 rather than 4 rows.
So there are the basic plans for it. I have started on the front end a bit. But with other things in the lineup, It will be at least a few weeks before I can get to finishing it off.
I have had the F5mX biased anywhere from 35-65 watts per channel and the sound doesn't change all that much with bias.
In your 4U 400mm, I suspect the heatsinks can tolerate 35-40 watts a channel and be below say 55C. But I haven't calculated that...
If you take two original F5m amplifiers and tie them at the feedback, then you are getting pretty close to this F5mX. With that being said, the F5mX is already bridged. So it kind of is what it is in that regard. But with the 4 mosfets on the output stage per channel, it can make 50 watts very comfortably in class A.
What I would consider is trying the amp in stereo mode to make sure you like it. If you do, then try making monoblocks out of it. Again, I do have it on my list to make a set of mini monoblock PCBs. Basically this stereo kit severed into two. So instead of one output supply board with two phases on it, it would be two boards each with their own phase. One on each side of the chassis. I think this would make a cute little 4U 300mm Monoblock. They would hit the 50 watts and you can have your monoblocks sitting next to the speakers with a short speaker cable which is kind of nice. You would step down to a 400VA transformer.
Another change would be the amount of caps. I would want to make the cap bank smaller. So instead of 24 caps, I would use 18 caps. Which is three rows of 6 rather than 4 rows.
So there are the basic plans for it. I have started on the front end a bit. But with other things in the lineup, It will be at least a few weeks before I can get to finishing it off.
Mike,
For no other reason than some fun experimenting I'm intrigued about 8 Mosfets per output stage. I'll keep an eye on your posts for the next chapter of your design. Many thanks for your contribution.
Regards,
Dan
For no other reason than some fun experimenting I'm intrigued about 8 Mosfets per output stage. I'll keep an eye on your posts for the next chapter of your design. Many thanks for your contribution.
Regards,
Dan
Yes! I plan to get more IRFP140/9140 mosfets to test that.
240/9240
single quad
4 pairs per channel
6 pairs per channel
J201/k1530
single quad
4 pairs per channel
140/9140
single quad
I like the single quad of the IRFP140/9140 and the single quad of the j201/1530 the best.
I am hoping that the 4 pairs of 140/9140 will sound good. We will see 🙂. I think to get enough matches of the 140/9140 for 4 pairs of mosfets per channel, you need to order them from a place like Mouser, digikey or Arrow and get about 20 of each. I was able to get a some nice matches for the a single quad per channel by purchasing 12 of each.
240/9240
single quad
4 pairs per channel
6 pairs per channel
J201/k1530
single quad
4 pairs per channel
140/9140
single quad
I like the single quad of the IRFP140/9140 and the single quad of the j201/1530 the best.
I am hoping that the 4 pairs of 140/9140 will sound good. We will see 🙂. I think to get enough matches of the 140/9140 for 4 pairs of mosfets per channel, you need to order them from a place like Mouser, digikey or Arrow and get about 20 of each. I was able to get a some nice matches for the a single quad per channel by purchasing 12 of each.
Mike,
Until I saw your construction pic I didn't realize that you could have both single ended and balance inputs?
Regards,
Dan
Until I saw your construction pic I didn't realize that you could have both single ended and balance inputs?
Regards,
Dan
Yes. For a single ended you tie the negative of the XLR to ground. I purchased a few of those little u-shaped jumpers from pass labs
Is there a benefit of having differential balanced inputs over single ended? How does it handle impedance balanced or single ended, does it have added components to generate the negative part of the signal? I'm still looking to build this but have been busy learning about gain staging first.
Input impedance for SE is 47k, double that for bal.
Balanced reduces noise and cancels out distortions... So you lose a bit of the SUSY effect. However, I wouldn't sweat it if you have a nice piece of gear that is RCA only. Generally the higher amount of noise that you will see with SE will derive from the rest of your system.
I have a couple of balanced preamps (one is a F5mX Preamp that I have been slowly working on), a couple balanced DACs and a SE tube Yamamoto YDA-B1 DAC... My favorite setup in my system is to switch between going DAC direct from the Yamamoto, or going through the balanced preamp with the Yamamoto. The Yamamoto being a tube DAC sounds wonderful but has the typical tube noise and other stuff. I have to place my ear on the tweeter to get any sort of noise at normal volumes...
There are no added components to convert the SE to a balanced signal. The SE signal has the negative tied to the GND so the full sine wave goes through the positive connection. The Neg is referenced to GND. If you want, you can use some sort of SE to BAL convertor but that just adds something to the signal path...
Balanced reduces noise and cancels out distortions... So you lose a bit of the SUSY effect. However, I wouldn't sweat it if you have a nice piece of gear that is RCA only. Generally the higher amount of noise that you will see with SE will derive from the rest of your system.
I have a couple of balanced preamps (one is a F5mX Preamp that I have been slowly working on), a couple balanced DACs and a SE tube Yamamoto YDA-B1 DAC... My favorite setup in my system is to switch between going DAC direct from the Yamamoto, or going through the balanced preamp with the Yamamoto. The Yamamoto being a tube DAC sounds wonderful but has the typical tube noise and other stuff. I have to place my ear on the tweeter to get any sort of noise at normal volumes...
There are no added components to convert the SE to a balanced signal. The SE signal has the negative tied to the GND so the full sine wave goes through the positive connection. The Neg is referenced to GND. If you want, you can use some sort of SE to BAL convertor but that just adds something to the signal path...
Ok, good to know. What does the inverted voltage signal connect to if differential balanced is used? ( just curious to know where since the F5m is single ended )
So if you look at the f5mx, you will see that it is essentially two f5m amplifiers that are bridged (pretty much tied at the feedback). Each of the 'F5m amplifiers' that are in the f5mx are responsible for one phase of the signal. So half of one F5mX channel is designated to the negative phase and half is designated to the positive phase. Neither the Negative or the positive binding post are tied GND but rather floating. You adjust the DC offset of each phase relative to GND but that is besides the point.
When you run the F5mX with a RCA, the input stage will act as a SE to BAL convertor and will sum the sinewave on the output. This is kind of the premise of the big Pass Labs amps... Only they have more parts, an extra gainstage and are designed by the almighty Mr. Pass and the almighty Mr. Colburn. We are reeeaaally lucky to have them hanging around here.
In the F5m, there is only one 'F5m amplifier'... Therefore it can only handle one input which is the full sine wave. Hence the RCA connection. The F5mX is inherently balanced due to it being two F5m amps that are bridged. so therefore it can receive a XLR balanced signal and act as a SE to balanced convertor.
The F5mX is balanced from the input to the output. There are a lot of amps that have balanced front ends that convert to single ended output stages. A lot of great amps at that.
I hope this helps. The F5mX is a fun project. I tried to make a balanced Pass 'like' amp that is as simple as possible to construct. Pass has been hinting at this type of design for the DIY crowd for a while between the BA3 as well as the other F5 type of variants that are out there. I was even suspicious of the extra pad on the Feedback of the F5m boards... So it is only natural that someone took the bait.
When you run the F5mX with a RCA, the input stage will act as a SE to BAL convertor and will sum the sinewave on the output. This is kind of the premise of the big Pass Labs amps... Only they have more parts, an extra gainstage and are designed by the almighty Mr. Pass and the almighty Mr. Colburn. We are reeeaaally lucky to have them hanging around here.
In the F5m, there is only one 'F5m amplifier'... Therefore it can only handle one input which is the full sine wave. Hence the RCA connection. The F5mX is inherently balanced due to it being two F5m amps that are bridged. so therefore it can receive a XLR balanced signal and act as a SE to balanced convertor.
The F5mX is balanced from the input to the output. There are a lot of amps that have balanced front ends that convert to single ended output stages. A lot of great amps at that.
I hope this helps. The F5mX is a fun project. I tried to make a balanced Pass 'like' amp that is as simple as possible to construct. Pass has been hinting at this type of design for the DIY crowd for a while between the BA3 as well as the other F5 type of variants that are out there. I was even suspicious of the extra pad on the Feedback of the F5m boards... So it is only natural that someone took the bait.
Hi Mike, PCB Set still available. Would it be possible to take a set without the Powersupply pcb?
Greeting from Bavaria,
Andreas
Greeting from Bavaria,
Andreas
Hi Mike;
Do you still have a set available? I would like to buy a set if you do.
Bob Craig
Lakeland, Fl
Do you still have a set available? I would like to buy a set if you do.
Bob Craig
Lakeland, Fl
Orgonom and comicrcc: Yes, I have plenty. I will shoot the both of you a PM later today when I get home from work with the details!
Mike
Mike
Greetings,
I have a set of Linkwitz Studio Mini's with Nelson's ASP, and I have been thinking about putting together a set of F5m's to drive them, but have been wondering about balanced operation (I'm currently balanced from the pre-ASP-amps). Now, you have solved that. I hope you have two sets of boards still left???
Christopher
I have a set of Linkwitz Studio Mini's with Nelson's ASP, and I have been thinking about putting together a set of F5m's to drive them, but have been wondering about balanced operation (I'm currently balanced from the pre-ASP-amps). Now, you have solved that. I hope you have two sets of boards still left???
Christopher