Can you believe if I told you, I dont even have a single fully built amplifier with chassis that I can go home and listen to on my main speakers. A nice floor standers in one room and Tarkus in another room, they are waiting for an amp.
There is a big boxfull amps built and tested however that never saw a home in the form of a case/chassis.
There is a big boxfull amps built and tested however that never saw a home in the form of a case/chassis.
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mooly amp
Hi mooly thanks for steering me in the right direction,clumsiness and poor workmanship on my part was the problem.I have made my board from your layout. I don't know how to use spice so it was just a case of experience and reason. So for what it is worth, anybody on this thread there is nothing wrong with Mooly's board and it you build it you will be rewarded and you will have an excellent amplifier which I have enjoyed immensely. I am currently building 4 more, so once again Mooly, thanks and a Very Merry Christmas.
Yours truly, AMPMAN, expat
Hi mooly thanks for steering me in the right direction,clumsiness and poor workmanship on my part was the problem.I have made my board from your layout. I don't know how to use spice so it was just a case of experience and reason. So for what it is worth, anybody on this thread there is nothing wrong with Mooly's board and it you build it you will be rewarded and you will have an excellent amplifier which I have enjoyed immensely. I am currently building 4 more, so once again Mooly, thanks and a Very Merry Christmas.
Yours truly, AMPMAN, expat
Hey prasi
What will be output when used with 24 0 24 v ac trafo.
And what changes will be necessary to work on this voltage.
Regards
Viki
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You should get around 50 watts rms/8 ohm with a 24/0/24 transformer. Just make sure the TL071 supply is OK dropping the value of the 10k as needed.
Try a 6k8 and as long as the -12 volts is stable then its fine.
Try a 6k8 and as long as the -12 volts is stable then its fine.
mooly amp
Hi mooly once again. can we use irf fets ala nelson pass? also why the 10u and why electrolitic? I have seen JLH use .47 at the input. And why not film? and at plus or minus 25 volts we could use bc550-560? through out. thanks ampman
Hi mooly once again. can we use irf fets ala nelson pass? also why the 10u and why electrolitic? I have seen JLH use .47 at the input. And why not film? and at plus or minus 25 volts we could use bc550-560? through out. thanks ampman
The simple answer is no, IRF's are not suitable at all without some major redesign work.
The bias generator (the fixed resistor) would need to be an active type that tracked the output stage temperature such as vbe multiplier.
The FET's would probably need the 0.22 ohm resistors moving from drain to source to improve thermal stability.
And worst of all, it would lose that magic quality that the lateral FET's bring.
The 10uF electrolytic cap was specified for two reasons,
1/ Because of the lowish input impedance which is determined by the 33k to the opamp output.
2/ The single stage servo adds a small hump to the very low frequency response and so you want that point to be below where it could be audible. The peak occurs at 5Hz with the values shown. Using 0.47uF would move this to close to 30Hz.
The BC550 is only 45 volt Vce so its marginal even for -/+25 volts DC rails. Remember that some devices in the amp see almost full rail to rail voltage under conditions of maximum drive, for example the VAS.
The bias generator (the fixed resistor) would need to be an active type that tracked the output stage temperature such as vbe multiplier.
The FET's would probably need the 0.22 ohm resistors moving from drain to source to improve thermal stability.
And worst of all, it would lose that magic quality that the lateral FET's bring.
The 10uF electrolytic cap was specified for two reasons,
1/ Because of the lowish input impedance which is determined by the 33k to the opamp output.
2/ The single stage servo adds a small hump to the very low frequency response and so you want that point to be below where it could be audible. The peak occurs at 5Hz with the values shown. Using 0.47uF would move this to close to 30Hz.
The BC550 is only 45 volt Vce so its marginal even for -/+25 volts DC rails. Remember that some devices in the amp see almost full rail to rail voltage under conditions of maximum drive, for example the VAS.
Hi Mooly,
I just noticed a little thing in your schematic on post #1. If I'm not mistaken, the pin numbering for the MOSFETs is wrong. Gate is correctly numbered with 1, but Drain and Source are numbered reverse from what the datasheets mention (Source should be pin 2, not 3, and Drain be pin 3, not 2). Seems like nobody stumbled upon that yet, but while I created some Devices for the EAGLE layout editor I had to double-check to get it right.
Anyhow, here's the schematic so far. I tried to make it a little 'neat' and easily printable as a PDF.
The layout will follow, but I have not yet decided on whether it will be something along the line of Alex's work of art, or more like a tidy stuffing guide for a perfboard. Maybe I'll do both...
I just noticed a little thing in your schematic on post #1. If I'm not mistaken, the pin numbering for the MOSFETs is wrong. Gate is correctly numbered with 1, but Drain and Source are numbered reverse from what the datasheets mention (Source should be pin 2, not 3, and Drain be pin 3, not 2). Seems like nobody stumbled upon that yet, but while I created some Devices for the EAGLE layout editor I had to double-check to get it right.
Anyhow, here's the schematic so far. I tried to make it a little 'neat' and easily printable as a PDF.
The layout will follow, but I have not yet decided on whether it will be something along the line of Alex's work of art, or more like a tidy stuffing guide for a perfboard. Maybe I'll do both...
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The reason is (and its not an excuse 😉)... is that when I posted all those years back that drawing was one of my first attempts at using a PC to do such things (it looks like I used Diptrace for that one) and it was just an attempt to get something neater than the hand drawn original. I must have used the standard library images for the common IRF types.
I also never imagined at the time there would be so much interest over the years and so post #1 is unrecognizable now as to how it was way back then, when looking at the dates I was actually a newbie here 😉
This is the original 🙂
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Not too bad actually
!I've been intrigued by your design for several years now, so maybe now is the time that I actually get around to build it...
merry christmas
Thank's Preamp for new schematic drawing, have saved the files. 🙂
Some month back i have started own drawing pcb with diptrace and
taken prasi's schematic for help.
Because this amp has awaked AKSA's interest and i like much how
LatMos could sound (FX-8, LM60- M.Chua, Hybrid+ 6N6P gain stage, not to forget FetZilla), i decided i should build one.
Now i've nearly finnished the build and hopefully can present with
success next time.....
Mooly, hope the amp will longer get attention. 🙂
Wish all here very good Christmas time and good start to new year.
Thank's Preamp for new schematic drawing, have saved the files. 🙂
Some month back i have started own drawing pcb with diptrace and
taken prasi's schematic for help.
Because this amp has awaked AKSA's interest and i like much how
LatMos could sound (FX-8, LM60- M.Chua, Hybrid+ 6N6P gain stage, not to forget FetZilla), i decided i should build one.
Now i've nearly finnished the build and hopefully can present with
success next time.....
Mooly, hope the amp will longer get attention. 🙂
Wish all here very good Christmas time and good start to new year.
Mooly-E-Wonk
And for something completely off-topic I would point out that the Mooly-e-wonk is a feared Crytid in Australia. Refer to cryptozoo-oscity: More on the Moolyewonk, said to be Australia's living plesiosaur