Thanks for pointing out that DC converter is back again. Did not realize parts cost that much as I had most stuff from my lab bench bins. Good luck on the build.
Hi
I have built my version of this amplifier with my PCB design. It is still on the tests with many different headphones (32 ohm ortho and 32, 50,300 600 ohm dynamic
it is not in the case yet, but I can say that
this amplifier sounds great.
Thanx XRK for sharing this project!
BTW
Have you thought about the power version of this amplifier (about 5-8 W) for HF loudspeakers? I have pair of old full range speakers with AlNiCO
Something like CAMP AMP Nelson Pass?
I have built my version of this amplifier with my PCB design. It is still on the tests with many different headphones (32 ohm ortho and 32, 50,300 600 ohm dynamic
it is not in the case yet, but I can say that
this amplifier sounds great.
Thanx XRK for sharing this project!
BTW
Have you thought about the power version of this amplifier (about 5-8 W) for HF loudspeakers? I have pair of old full range speakers with AlNiCO
Something like CAMP AMP Nelson Pass?
Attachments
Beautiful work, Zoltan!
Glad you like the sound - it is very clear and articulate with gobs of deep deep bass. I suppose a 5-8w could easily be made by using IRFP9240's and increase rails to +/-24v and boost bias current to say 1.25amps, and we would have to be careful not to over-stress the BF862's as they are rated only 20v, but it may work because the voltages between them is not that high.
Glad you like the sound - it is very clear and articulate with gobs of deep deep bass. I suppose a 5-8w could easily be made by using IRFP9240's and increase rails to +/-24v and boost bias current to say 1.25amps, and we would have to be careful not to over-stress the BF862's as they are rated only 20v, but it may work because the voltages between them is not that high.
Simply replace the main bias current control power resistors with 0.22R, use +/-19v power supplies (2 laptop bricks in series), and switch to IRFP9240 MOSFETs. This gives a 1.83amp bias current and decent performance at 5Wrms and nice at 1Wrms into 8ohms. Not as clean as an Alpha 20 (which has fewer parts) and can go to 35w at 4ohms. But it is DC coupled all the way thru.
FFT for 8Vpp into 8ohms:
Attachments
Last edited:
Yes, you may need more than 10mF caps if you are flowing Class A currents. Or use a cap multiplier and 10mF is fine. The new Mark Johnson /Prasi BJT cap multiplier works well on Class A amps. Will let you use single 10mF and achieve under 2mV ripple with 1.25amp load vs 4x33mF caps per channel ($$$).
Progress has been slow on my build, getting there though. Finished up the PSU yesterday and a little more to go on the amp PCB.
Just wanted to post that the Meanwell converter posted a while back seems to be a drop in replacement for the traco - I just shifted a few things to the back side of the PCB as the meanwell is a lot larger than the traco.
Just wanted to post that the Meanwell converter posted a while back seems to be a drop in replacement for the traco - I just shifted a few things to the back side of the PCB as the meanwell is a lot larger than the traco.
Here are some pictures of my power supply board.
Regs are socketed - testing with 7818 and 7918 at the moment.
Getting 16V on +ve & -17V after reg & cap mx.
I've forgotten - what was the output voltages we are aiming for after cap mx? (once the adjustable LDOVR regs are in place)
Regs are socketed - testing with 7818 and 7918 at the moment.
Getting 16V on +ve & -17V after reg & cap mx.
I've forgotten - what was the output voltages we are aiming for after cap mx? (once the adjustable LDOVR regs are in place)
Attachments
How would that be achieved on the neg rail? (the LDOVR negative reg is max of -18V meaning final output will be -18 less cap mx drop?)
TPS7A3301 Ultra Low Noise LDO Voltage Regulator
Features
Ultra Low Noise Voltage Regulator
-3V – -18.3V (1V step) 1A
TPS7A3301 Ultra Low Noise LDO Voltage Regulator
Features
Ultra Low Noise Voltage Regulator
-3V – -18.3V (1V step) 1A
LDOVR.com doesn't make an adjustable negative output one - you can reprogram yourself by changing the resistors. Or get the eBay made in China version with a pot. Here is an example of one (but not in TO220 format).
TPS7A3301 1A -1.18V~-33V Adjustable Low Noise Negative Linear Power Supply Board 699986551561 | eBay
I just came across this dual rail regulator (programmable via DIP switches):
TPS7A4701 TPS7A3301 Low Ripple Positive Negative Linear Power Supply Module 1A | eBay
TPS7A3301 1A -1.18V~-33V Adjustable Low Noise Negative Linear Power Supply Board 699986551561 | eBay
I just came across this dual rail regulator (programmable via DIP switches):
TPS7A4701 TPS7A3301 Low Ripple Positive Negative Linear Power Supply Module 1A | eBay
adjustable pot - very bad idea for the voltage reference circuit, specially for low noise application, TPS7A3301 can be shipped with 3-21V configurable version (with 1V step), BUT MAX INPUT 25VDC
replace R7 (1M5 resistor @ top right corner - 0.3V pad) with 105K (SMD 0603)
after modification 0.3V PAD will add 4V - you can configure from 3V to 22V with 1V step
for 20V - need to solder 8V, 4V, 1V and 0.3V (now 4V) pads
Vout = 3+8+4+1+4 =20V