A60(+) Amplifier. Build this?

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#84
Parohod5, when the left and right channels have the same ground (GND), then yes, the scheme is suitable. And for my case (dual mono), the GNDs of the left and right channels are not galvanically coupled. Then the right indicator will not work according to this scheme. Unless, of course, you combine the midpoints of the secondary windings of the two transformers. By the way, this is also a question, is it possible and necessary to do this?
 
#86
We are of-topic now. This thread is about A60 amplifier, not about VU. Please, let's keep it clean. You can discuss this elsewehere in a conversation about VU then get back here later with issues related to the present topic.
Hope you understand.
 
#89
Hi Berlusconi. All the components came from China and I finally managed to figure out the connection diagram for all the components. Assembled the amplifier. I had to make myself a power supply for the control board with arrow indicators (on LM317, adjustable, set to 9.5VDC), and power supply for the backlight of the power button. It turned out to be with a fixation of the on / off position. As a result, the indicators work, and in the case I have 4 transformers, 2 - power, 1 in soft start, and 1 - power supply of the indicators. Upset by the presence of transformer pickups in the speakers. There is audible noise in audio pauses (50Hz). I examined the power amplifier boards and found out that the GND of each channel combine the midpoint of the secondary winding of the transformer (36-0-36 AC), the output of the secondary winding of the 12V transformer (0-12AC) and the IN input from the preamplifier. What I've done. Connected "-" of the left and right channels of the output signal (which are connected to the acoustics) to the amplifier body. I also connected the "-" input of the indicator control board there. It got better, but the noise of the transformer can be heard in the acoustics. How can you improve? And by the way, which wire is better to connect the input RCA connectors to the inputs of the power amplifier boards? I don't like mine. I want to see links to good cables.Thanks in advance.
 
#90
HI VMK2002.
I'm glad you have safely started the amplifier. My A60+ is dead silent without signal at the input and you will have the same. Patience.. Make sure that the amplifier isconnected to good source: DAC, good preamp or good player. Use shielded wiring for input connection. There is a good thread here about eliminating noise. You can also read great article at hifisonics.com, this article:

Ground Loops
 
#91
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#94
Hi Berlusconi. Everything that I depicted on the PCB PowerAmp 1 and 2 board I measured with a multimeter on my boards. Do you also have 0 and GND connections inside the boards? By the way, do you have 2 power transformers? I also want to ask you how you connected the input signal to the PCB PowerAmp from the RCA inputs and what connections you made for the RCA connectors. Have you used a shielded cable?
 
#95
terranigma said:
Your measurement seems done at 5V/div so slew rate must be around 30/1.25=24 V/uS right? Have you managed to sim or measure THD at 1kHz and 20kHz respectively? Can put some more measurement data please? Did you manage to sim phase margin, open loop stability etc?
Click to expand...
Grounding within the board is fine - don't worry about that. Properly connected board may easily attain noise below -100 dB. All you have to do is to connect according to the published schematics. I am using capacitance multiplier for power supply (to do this I have bypassed internal rectifier) and I have my own 2X4X20.000 uF capacitors in place of these (probably) fake "ELNA". I have purchased a board without the "ELNA" capacitors and likely generic power transistors and purchased these parts from Farnell. Connect input with shielded cables and keep transformers as far as possible from the input cabling and keep input cables as short as possible. Important: you have to connect input with quality DAC, preamplifier or player. Otherwise there will be hum if you leave input just disconnected.
Remember, use current limiter or variac and never leave the amplifier turned overnight before you find optimal quiescent current for your amplifier.
Cheers and pleasant Sunday evening.🙂
 
#96
vmk2002 said:
Hi Berlusconi. Everything that I depicted on the PCB PowerAmp 1 and 2 board I measured with a multimeter on my boards. Do you also have 0 and GND connections inside the boards? By the way, do you have 2 power transformers? I also want to ask you how you connected the input signal to the PCB PowerAmp from the RCA inputs and what connections you made for the RCA connectors. Have you used a shielded cable?
Click to expand...
This could be very helpful:😉
http://hifisonix.com/wordpress/wp-c...B-Design-Guidlines-for-Minimizing-Hum-1-1.pdf
 
#97
Hi Berlusconi! Have you finished customizing your A60 +? I would be grateful for a photo of the assembled amplifier and, if possible, with the top cover removed. I'm expecting the supply of a high-quality cable for wiring the input signal from the RCA connectors, maybe the photo will inspire me to do the assembly work as efficiently as possible (We have such a joke: do it well, but it will turn out badly 🙂) ... And along the way the question, what capacitors did you put on the board? (at least the manufacturer).
 
#100
I hope when I finish my amplifier and post detailed photos of it, I will receive constructive criticism. I hope my experience is useful to someone. I thought the owners were feeling well, if not pride in their power amplifier, then at least aesthetic satisfaction. Smilies for children. Regards, Victoire!
 
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