Hey DIYers,
I'm in the process of building several things at once, a pair of Heissmann Acoustics' Cinetor Evos, and a few differents fullrange projects, mainly centered around high efficiency, large drivers (Fane 12-250TCs, SBAcoustics SB20FRCP30s).
I was going to buy a Loxjie A30 as an amp, but I figured I might get better results going DIY, for the same price of slightly higher. I have enough experience in electronics to put an amp together.
Between chip amps, class Ds, class A, AB, etc, I'm a little lost here. I gave a look at Pass Labs project but I can't tell anything apart.
Therefore, I'm looking for a recommendation for a DIY amp to build, preferably below 300€, that would help make those higher efficiency (90/92dB) really shine, especially in the bass department.
Full disclosure: I listen at low, medium low volume, nearfield type situation, in a small room, 1/2meters away from the speakers max. I'm looking to squeeze as much dynamic range from the speakers, if that helps...
Any help would be greatly appreciated!
I'm in the process of building several things at once, a pair of Heissmann Acoustics' Cinetor Evos, and a few differents fullrange projects, mainly centered around high efficiency, large drivers (Fane 12-250TCs, SBAcoustics SB20FRCP30s).
I was going to buy a Loxjie A30 as an amp, but I figured I might get better results going DIY, for the same price of slightly higher. I have enough experience in electronics to put an amp together.
Between chip amps, class Ds, class A, AB, etc, I'm a little lost here. I gave a look at Pass Labs project but I can't tell anything apart.
Therefore, I'm looking for a recommendation for a DIY amp to build, preferably below 300€, that would help make those higher efficiency (90/92dB) really shine, especially in the bass department.
Full disclosure: I listen at low, medium low volume, nearfield type situation, in a small room, 1/2meters away from the speakers max. I'm looking to squeeze as much dynamic range from the speakers, if that helps...
Any help would be greatly appreciated!
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Pass circuits would be too expensive unless you already have a suitable chassis.
You need very low noise and hum.
You need very low noise and hum.
I've used this amplifier since 1994 and never felt the need to change it:
"Audio power with a new loop", Electronics World February 1996, pages 140...143, https://worldradiohistory.com/UK/Wireless-World/90s/Electronics-World-1996-02-S-OCR.pdf
It was designed to be cheap, but some components are obsolete and may need to be replaced if you can't get them anymore. The power is more than enough for moderate volume and fairly sensitive speakers. There is no PCB design.
There are probably dozens of other amplifier designs that would also work fine. You won't need a lot of power and high power increases the costs considerably, so I'd look for amplifiers in the 5 W to 30 W per channel range.
"Audio power with a new loop", Electronics World February 1996, pages 140...143, https://worldradiohistory.com/UK/Wireless-World/90s/Electronics-World-1996-02-S-OCR.pdf
It was designed to be cheap, but some components are obsolete and may need to be replaced if you can't get them anymore. The power is more than enough for moderate volume and fairly sensitive speakers. There is no PCB design.
There are probably dozens of other amplifier designs that would also work fine. You won't need a lot of power and high power increases the costs considerably, so I'd look for amplifiers in the 5 W to 30 W per channel range.
Class D is probably cheaper to design, is it acceptable to you? everyone has their opinions on sound quality. I have tried TI parts seem to perform well.
There are lm3886 gain clone designs but those chips are in long back order.
When I have more time I want to try to understand Marcel’s unique design.
There are lm3886 gain clone designs but those chips are in long back order.
When I have more time I want to try to understand Marcel’s unique design.
You can get 50 to 70 w/ch for $50 transistors with https://www.diyaudio.com/forums/solid-state/236256-retro-amp-50w-single-supply-42.html
You can still get 2n5401 input and MJE340 VAS but I used On MPSA06 input, MJE15028 vas & NPN driver, MJE15029 pnp driver, mj15003 output transistors. You can also use single hole MJW21196 or MJL3281 as output transistors which saves about $5 each. Use insulators on the output transistors, and I used little heat sinks on the drivers and VAS. 1.5 cm aluminum channel cut out of a window screen frame. Don't cheap out on the drivers or VAS, TIP31c/32c worked but had dull lifeless highs. You want 30 mhz ft or above for drivers & vas.
Heat sink, used Pentium II ones work well. You want about ~10 cm x 50 cm x 2 cm heat sink with about 6 fins.
You want a 44v to 50 v 500 va transformer. That is 60 to 70 v rail voltage. 7 amp minimum bridge rectifier. Three 3300 uf 80 v electrolytic caps. Since this doesn't have great hum rejection, I regulated the 72 v open circuit voltage to 69 v using 5 parallel TIP142 pass transistor with emitter resistors, a 72 v zener stack as base driver (6 series 12 v zeners series suitable current limiter resistor). I had another heat sink on the regulators. Regulator requires another pre-transistor e-cap, I used 1000 uf.
Case, you can use a metal file box with the heat sinks outside and a metal mesh vent over the transformer. I mounted my output transistors remotely from the driver board, with a 7 turn inductor series the sense wire back from the diode stack to the pnp driver to prevent possible oscillation. Don't put 70 v output transistors outside the case if you have a small child or a dog. Or put a metal mesh guard over them. Metal mesh is sold in the concrete section of a home store. A half box is metal mesh rectangle with squares cut out of the corners, then folded 90 degrees. Use kevlar/leather gloves, cut metal is sharp.
Be sure to put a 11 turn inductor (1 cm diameter) series the output and a 82-120 pf ceramic cap from input capacitor to ground. These are to prevent AM/police/fire/ambulance/CB radio interference. A zobel parallel the output to ground can prevent oscillation on some loads. 1000 ohms series .01 uf cap from output to ground.
wg-ski said this circuit can motorboat if driven to clipping, but why do that? I had to wear earplugs to test my amp at 23.6 vac output, where it was very musical.
A similar circuit using all european parts is www.diyaudio.com/forums/solid-state/343510-prehistoric-amplifier-archosaurus-6.html
As far as class D, my turntable can pick up digital howl located in the same room. Some FM radios do that too. I have the PC located 10 m away from the analog circuits, on a different mains circuit. I had a sampler keyboard with a computer inside once that caused digital howl, very annoying.
You can still get 2n5401 input and MJE340 VAS but I used On MPSA06 input, MJE15028 vas & NPN driver, MJE15029 pnp driver, mj15003 output transistors. You can also use single hole MJW21196 or MJL3281 as output transistors which saves about $5 each. Use insulators on the output transistors, and I used little heat sinks on the drivers and VAS. 1.5 cm aluminum channel cut out of a window screen frame. Don't cheap out on the drivers or VAS, TIP31c/32c worked but had dull lifeless highs. You want 30 mhz ft or above for drivers & vas.
Heat sink, used Pentium II ones work well. You want about ~10 cm x 50 cm x 2 cm heat sink with about 6 fins.
You want a 44v to 50 v 500 va transformer. That is 60 to 70 v rail voltage. 7 amp minimum bridge rectifier. Three 3300 uf 80 v electrolytic caps. Since this doesn't have great hum rejection, I regulated the 72 v open circuit voltage to 69 v using 5 parallel TIP142 pass transistor with emitter resistors, a 72 v zener stack as base driver (6 series 12 v zeners series suitable current limiter resistor). I had another heat sink on the regulators. Regulator requires another pre-transistor e-cap, I used 1000 uf.
Case, you can use a metal file box with the heat sinks outside and a metal mesh vent over the transformer. I mounted my output transistors remotely from the driver board, with a 7 turn inductor series the sense wire back from the diode stack to the pnp driver to prevent possible oscillation. Don't put 70 v output transistors outside the case if you have a small child or a dog. Or put a metal mesh guard over them. Metal mesh is sold in the concrete section of a home store. A half box is metal mesh rectangle with squares cut out of the corners, then folded 90 degrees. Use kevlar/leather gloves, cut metal is sharp.
Be sure to put a 11 turn inductor (1 cm diameter) series the output and a 82-120 pf ceramic cap from input capacitor to ground. These are to prevent AM/police/fire/ambulance/CB radio interference. A zobel parallel the output to ground can prevent oscillation on some loads. 1000 ohms series .01 uf cap from output to ground.
wg-ski said this circuit can motorboat if driven to clipping, but why do that? I had to wear earplugs to test my amp at 23.6 vac output, where it was very musical.
A similar circuit using all european parts is www.diyaudio.com/forums/solid-state/343510-prehistoric-amplifier-archosaurus-6.html
As far as class D, my turntable can pick up digital howl located in the same room. Some FM radios do that too. I have the PC located 10 m away from the analog circuits, on a different mains circuit. I had a sampler keyboard with a computer inside once that caused digital howl, very annoying.
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