the 5kHz sq w has severely attenuated harmonics.
The sq should just be slightly rounded when the input filter is set to 160kHz (F-3dB=160kHz) the 11th harmonics of 5kHz is 55kHz and should pass with nearly full strength.
It appears that something is attenuating the treble of the MyRef.
Can you try 10kHz sinewave and 20kHz and 30kHz? You may just be able to see a slight lessening of the output voltage ref the input voltage at these frequencies of a good MyRef.
I suspect you will see strong attenuation of 10kHz and upwards compared to the 1kHz setting.
The sq should just be slightly rounded when the input filter is set to 160kHz (F-3dB=160kHz) the 11th harmonics of 5kHz is 55kHz and should pass with nearly full strength.
It appears that something is attenuating the treble of the MyRef.
Can you try 10kHz sinewave and 20kHz and 30kHz? You may just be able to see a slight lessening of the output voltage ref the input voltage at these frequencies of a good MyRef.
I suspect you will see strong attenuation of 10kHz and upwards compared to the 1kHz setting.
Hi,
Generator output impedance is 40R and output is 5V peak to peak. I made a potential divider (500R/150R) to reduce voltage around 1V peak to peak. (I did not use a pot between divider and amp). I tested the surviving monoblock (LM318 ordered for his dead sibling today...), result was the same, squarewave is very damped. I also tested without any load on amp output, and there is no difference.
As Andrew pointed, I confirm attenuation increases with freq.
What else could I check ?
Generator output impedance is 40R and output is 5V peak to peak. I made a potential divider (500R/150R) to reduce voltage around 1V peak to peak. (I did not use a pot between divider and amp). I tested the surviving monoblock (LM318 ordered for his dead sibling today...), result was the same, squarewave is very damped. I also tested without any load on amp output, and there is no difference.
As Andrew pointed, I confirm attenuation increases with freq.
What else could I check ?
C34 is marked 10pF but I do not want to desolder it because I have no spare. Is it safe to short it to see if it changes the response attenuation ?
Too bad I already had desoldered the LM318 from the dead board (damaging a pad
). In fact R11 was dead, with a new resistor (and a new LM318...) the board is back from the deads, thank you very much for your help on this.I've checked and rechecked each R and C values, they're ok. However square wave response is still the same...
C34 seems ok, the only other RC is R37-C30, 3K3-1nF. Check the values, and also replace C7 with the best film-foil cap around 10 nF that you have. FKP2, FKC or FKS2 are good choices.
LED Voltage Question
Hi
I want to try and use the LED part of the circuit board as the feed to an LED in an on/off switch, however the LED in the switch needs to powered by a 12V DC supply, but the voltage on the rails for the MyRefC is 33.6V (assuming a 24V secondary supply to the bridge rectifier).
My thinking is to use a suitably sized resistor in series between the LED in the switch and the circuit board, however I need to calculate the size of the LED.
Looking at the circuit board I can see that the resistor size for the onboard LED is 470 ohm, thus the current to this part of the circuit should be 0.07 Amps.
Am I correct in thinking that I would need a further resistor valued at 171 ohms in series with the 12V LED and the circuit board? That's the answer I get when I plug 12V and 0.07 ohms into Ohm's law.
Or is it more complicated than that?
Thanks
Hi
I want to try and use the LED part of the circuit board as the feed to an LED in an on/off switch, however the LED in the switch needs to powered by a 12V DC supply, but the voltage on the rails for the MyRefC is 33.6V (assuming a 24V secondary supply to the bridge rectifier).
My thinking is to use a suitably sized resistor in series between the LED in the switch and the circuit board, however I need to calculate the size of the LED.
Looking at the circuit board I can see that the resistor size for the onboard LED is 470 ohm, thus the current to this part of the circuit should be 0.07 Amps.
Am I correct in thinking that I would need a further resistor valued at 171 ohms in series with the 12V LED and the circuit board? That's the answer I get when I plug 12V and 0.07 ohms into Ohm's law.
Or is it more complicated than that?
Thanks
I've checked, rechecked, unsoldered/resoldered, changed RC capacitors and... now I've got a much nicer square wave response over the audio band !
Thank you very much for your help.
I've a 100nf MKS2 for C7, what is the effect of lowering it to 10nF FKP ?
Thank you very much for your help.
I've a 100nf MKS2 for C7, what is the effect of lowering it to 10nF FKP ?
Fine
But what you did to obtain it?
The point is not the value but the quality of the cap.
Sadly film/foil caps in 5mm LS are 33nF max.
You're welcome - please post the key changes, if any, to achieve the square wave response.
The effect of the foil cap at C7 is tighter definition and imaging. The lower value also increases the self-resonant frequency with the track inductance about 3x, putting it well outside the audio band.
Hi,
Sorry to disappoint, I do not know exactly what was the culprit. No special discover here, I guess I just messed up a C value. Or perhaps a bad solder, or a bad component, but I doubt since my two mono-blocks behaved the same. I didn't measured the capacitance of the replaced capacitors.
Short listening session on a real speaker last night in mono, it sounds fine to me, and I noticed very clean and tight bass. I remember from previous Gainclone of changes during the first hours, is there a "burn-in" time recommended with the MyRef before playing with component swap ? I plan to change C7 as recommended on one monoblock to compare.
Thanks again, your support gave me the motivation to sort this out and finish this project, I'm sure the boards will otherwise have stay 6 month longer on a corner of the bench...
Time for metal work, maybe a finished amp in 6 months
...
Sorry to disappoint, I do not know exactly what was the culprit. No special discover here, I guess I just messed up a C value. Or perhaps a bad solder, or a bad component, but I doubt since my two mono-blocks behaved the same. I didn't measured the capacitance of the replaced capacitors.
Short listening session on a real speaker last night in mono, it sounds fine to me, and I noticed very clean and tight bass. I remember from previous Gainclone of changes during the first hours, is there a "burn-in" time recommended with the MyRef before playing with component swap ? I plan to change C7 as recommended on one monoblock to compare.
Thanks again, your support gave me the motivation to sort this out and finish this project, I'm sure the boards will otherwise have stay 6 month longer on a corner of the bench...
Time for metal work, maybe a finished amp in 6 months
...
Sorry for the off topic post linuxguru, but I've tried e-mailing you, and have also sent a private message via this site, with no response to either, and yet you've been online... I paid for my kit on the 26th September and have yet to receive anything. Have you sent it out yet please?
Thank you.
John.
MyRef C Caddock R3 with LM3886 grounded at power GND
An externally hosted image should be here but it was not working when we last tested it.
MyRef Dario Caddock R3 old C32 value
An externally hosted image should be here but it was not working when we last tested it.
Isn't it interesting?
Sorry ,can someone explain what these graphs is showing ?
How the graphs are done and how is the measurement done ?
Thank you !