Or bend slightly, if its only a couple of mm.
Mpmarino, In the Norwegian Oil business they use the term "sledge mechanic" for those that dont posess the finer mechanical skills.
In Iceland the approach used to be different as the skills where there but availability of parts was poor so you fixed things with what you had
In the late 70s i ordered a set of parts for a 66' Oldsmobile my father gave me. 3 years later I got only one part and it was the wrong termostat
Mpmarino, In the Norwegian Oil business they use the term "sledge mechanic" for those that dont posess the finer mechanical skills.
In Iceland the approach used to be different as the skills where there but availability of parts was poor so you fixed things with what you had
In the late 70s i ordered a set of parts for a 66' Oldsmobile my father gave me. 3 years later I got only one part and it was the wrong termostat
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Got the Edcors today. They are the wrong ones ie 15k:600.
As the pins are of soft metal I tryed bending them so I can mount them rotated 180deg in the PCB. Seems ok. No I just need to wait for the PCBs
Well, the parts are coming in... good luck with your build kbergsson! And keep us posted.
Got the Edcors today. They are the wrong ones ie 15k:600.
As the pins are of soft metal I tryed bending them so I can mount them rotated 180deg in the PCB. Seems ok. ........
Excellent! So you only needed a chisel
Don't feel bad. I ordered the wrong ones as well. Fortunately i think better while I'm asleep - woke up in a cold sweat and immediately sent an email asking for a change
Looking forward to hearing my M2 when it's done. Assuming it works at all
Excellent! So you only needed a chisel
Don't feel bad. I ordered the wrong ones as well. Fortunately i think better while I'm asleep - woke up in a cold sweat and immediately sent an email asking for a change
Looking forward to hearing my M2 when it's done. Assuming it works at all
I'm a screw up
Went to power the M2 up.
I totally messed it up. Never went back to check the board layout in relation to components. Used a footprint for the p-Mos with swapped source and drain AND used the wrong pin-out for the LM385 - DOH!
Serves me right for rushing. Did a swaperoony on the bottom of the board for the P -IRFPs and my LM385s now look like they are doing the twist
Now she biases up beautifully! What an elegant design - bias is so accurate and consistent.
Uses a 'universal' +/- 24V external PSU. It's still out in the shop, haven't heard it, nor done the finishing touches yet. Attached is a crappy pic (crappiness is intentional). Any similarities to a Big Boy Pass amp are purely intended
Went to power the M2 up.
I totally messed it up. Never went back to check the board layout in relation to components. Used a footprint for the p-Mos with swapped source and drain AND used the wrong pin-out for the LM385 - DOH!
Serves me right for rushing. Did a swaperoony on the bottom of the board for the P -IRFPs and my LM385s now look like they are doing the twist
Now she biases up beautifully! What an elegant design - bias is so accurate and consistent.
Uses a 'universal' +/- 24V external PSU. It's still out in the shop, haven't heard it, nor done the finishing touches yet. Attached is a crappy pic (crappiness is intentional). Any similarities to a Big Boy Pass amp are purely intended
Attachments
I have a question about the bias settings on this amp. As I understand it, the fets are set at roughly 1.5A. The F4 uses the same fets in a similar configuration, and same voltage, but are only biased at around .5A.
How do we account for this?
Are the distortion characteristics so similar at such a wide range?
Can the m2 be run at 1/3 the bias and still sound good?
I understand that the F4 has three fets in parallel, so more current capability, but my question is more about distortion characteristics.
Thoughts?
How do we account for this?
Are the distortion characteristics so similar at such a wide range?
Can the m2 be run at 1/3 the bias and still sound good?
I understand that the F4 has three fets in parallel, so more current capability, but my question is more about distortion characteristics.
Thoughts?
It's an easy experiment to try, just modify the negative feedback loop that sets the bias, and listen to the modified amplifier. Do you like what you hear?
The components of the NFB bias loop are (R6,P1,R7,Q5) and (R10-R14) from the schematic attached to post #1 of this thread.
Keep in mind that when you reduce the DC bias current in the output stage, you reduce the maximum Class-A output power. If you propose to set DC bias to 0.5 amperes, then math says the amplifier will exit class-A when driving more than 4.0 watts into an 8 ohm load. Maybe you will find the amplifier has one sonic signature when playing very loud, and another sonic signature when not playing very loud. (Maybe you'll LOVE both of them!). Try it and see how you like the sound.
If you want to hook it up to distortion measuring equipment, before and then after the modification, please feel free!
The components of the NFB bias loop are (R6,P1,R7,Q5) and (R10-R14) from the schematic attached to post #1 of this thread.
Keep in mind that when you reduce the DC bias current in the output stage, you reduce the maximum Class-A output power. If you propose to set DC bias to 0.5 amperes, then math says the amplifier will exit class-A when driving more than 4.0 watts into an 8 ohm load. Maybe you will find the amplifier has one sonic signature when playing very loud, and another sonic signature when not playing very loud. (Maybe you'll LOVE both of them!). Try it and see how you like the sound.
If you want to hook it up to distortion measuring equipment, before and then after the modification, please feel free!
I haven't built it yet. Just asking, wondering if I could build a smaller idle heat machine, and wondering as I look at the F4 schematic whose output appears similar. So it's a theoretical question not so much a try it and see question.
As I understand it, "Push-pull ampliers generally operate in Class A mode up to a point where the output current is twice the value of the bias current." So in the case of .5A that would be leaving class A at 8w @8 ohms for the M2, right? But high bias also is good for the distortion spectrum too. Since the F4 is only biased at .5A using these same fets, then I'm theorizing that .5A is ok here too (from a distortion perspective)
So, summarizing I'm guessing if I'm ok with leaving class A at 8W, then I can build a much smaller (and still really good sounding) m2 by biasing at only 1/3 the original design. Is my logic flawed?
As I understand it, "Push-pull ampliers generally operate in Class A mode up to a point where the output current is twice the value of the bias current." So in the case of .5A that would be leaving class A at 8w @8 ohms for the M2, right? But high bias also is good for the distortion spectrum too. Since the F4 is only biased at .5A using these same fets, then I'm theorizing that .5A is ok here too (from a distortion perspective)
So, summarizing I'm guessing if I'm ok with leaving class A at 8W, then I can build a much smaller (and still really good sounding) m2 by biasing at only 1/3 the original design. Is my logic flawed?
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Listened to the M2 first time for about an hour.
The first thing that surprised me was the bass control - this amp really does this extremely well, compared to say.... the Aleph.
Where the Aleph really shined for me was in the midrange, so much so that I was happy to give up a little grip.
I think this amp does both really well. The midrange is sublime, AND the bass grippy. Best of both worlds It really seems to match the Klipsch Forte' II well.
All with only 4000 uF capacitance following my SMPS. YUP - an M2 on SMPS
....waiting for the flames.
The first thing that surprised me was the bass control - this amp really does this extremely well, compared to say.... the Aleph.
Where the Aleph really shined for me was in the midrange, so much so that I was happy to give up a little grip.
I think this amp does both really well. The midrange is sublime, AND the bass grippy. Best of both worlds
It really seems to match the Klipsch Forte' II well.All with only 4000 uF capacitance following my SMPS. YUP - an M2 on SMPS
....waiting for the flames.
Remember that M2 has excellent PSRR.
The M2 circuit completely eliminates the weakest link in conventional power amplifiers, where noise and spuriae from the supply can mix with the signal and find their way onto the output. That weak link is the voltage gain stage a/k/a "VAS". M2 uses an autotransformer instead of a VAS, and it's not connected to either power supply. Voila, that entry point for supply noise has been sealed off and eliminated.
The M2 circuit completely eliminates the weakest link in conventional power amplifiers, where noise and spuriae from the supply can mix with the signal and find their way onto the output. That weak link is the voltage gain stage a/k/a "VAS". M2 uses an autotransformer instead of a VAS, and it's not connected to either power supply. Voila, that entry point for supply noise has been sealed off and eliminated.
Thanks Mark, that is good to know.
Is it necessary to shield the autoformer at all? If so, would MuMetal do the trick? Any recommendations as to how much shielding is needed?