Xmas Amp - Dibya's TDA7293 by Jhofland

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#804
Been listening to this amp for a good while now and I do like it.

Today I was doing some speaker measurements in room using the amp and we discovered that one channel is 6db higher than the other. I measured AC voltage at the speaker with a 50Hz signal and one was approx 1v while the other was 1.5v.

What should I be looking at please?

Thankyou
 
#805
Gain is set by R1 and R3. Perhaps use of 5% carbon film here may have caused gain error if R1 is +2% and R3 is -5%. Measure the values and select matched pairs for left and right channels. Or replace with 1% metal thin film.
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#808
You can always bridge a standard amp by feeding two amps from a balanced line driver with opposite phase. The +ve outputs from each amp is now positive and negative and live and you cannot reference speaker output to a ground. I am not sure about parallel though. You’ll have to ask Jhofland about that.
 
#811
It's a fine sounding amp on par, I think, with any LM3886 gainclone-like amp. For cost, it's a worthy DIY build with trustworthy design. One would need to go to more complicated & expensive amp builds, i.e., the Freman Evo A LM3886 based amp, to get a more refined amp. One always has to make the choice of the total cost of putting together a new amp (PCBs are free, cost of components, case, transformer + PS, etc) versus just buying an already built Class D unit (the Topping PA5 is the new darling of the inexpensive Class D world). If your more into DIY it's a fun little project.
 
#812
X, and other builders,

Getting my Xmas build going. For the low cap psu, I have 25 Vac (35Vdc) from secondaries. My question is: Taking into account transformer loss, maybe 3 volts, should I be using a 15K ohm resistor to drop the current to around 2mA or is better to go to a larger value, say 20K ohm since the SSR's regulate to 15 VDC.

Thanks for the help,
 
#813
Are you asking what size resistor is needed for the indicator LED on the low capacitance PSU? The SSR itself draws 20mA and you want to let it be connected directly to the output of the low cap PSU so that it can draw down the current and shut off quickly. Indicator LEDs should be sized for 2mA current to prevent them from blowing too bright or not lasting long enough.
 
#814
Hi X, That is what I meant, just never worded it correctly. The same conversation that we had on the FH9 thread. 35VDC /0.002A = 17.5K ohms for the resistor on the low cap board. I assume it is better to have a slightly higher resistance than a lower value for the resistor.
 
#820
Good Afternoon,

I have attached some images of my proposed layout for the Xmas amp. This is a very preliminary prototype enclosure just built to make sure I can build a working amp, no lid will ever be attached. I will be moving the Xmas amp to a better home in the future.

The one thing that bothers me: I purchased some switches and wiring harness's to have a remote switch. The switch harness has 20 ga. x 500V wires. Are these 20 ga. wires sufficient to safely handle the 120V mains voltage and current that one might expect. The IEC/filter module is rated for 220V/10A

Depending on the answers I receive I am thinking of using some 16ga. silicon wire and running from the IEC/filter module to the switch and then to the soft start module. ( No harness with 20 ga. wire).

Any recommendations please.

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