I have the same idea with you. Great! Thanks for sharing.
Glad to hear you're using this: I plan to keep it much more aggressively up-to-date than has been the case in the past, but don't hesitate to let me know if you find errors or need clarifications.
Did you ever look into the datasheet? Page 8: Rm = (|Vee|-2,6 V)/0,0005 A. Check how much the voltage sags under load to avoid that the amplifier mutes itself at high power demands.
LM 3886 datasheet specs hunt
While waiting for my Modulus 286 I decided to have some fun and learn.
After some time spent reading on this forum, reading about PCB designs and @tomchr guide on LM3886 I got inspired and made this LM3886 layout in KiCad with certain goals:
-Making my first CAD PCB
-Making a basic stable LM3886 configuration
-Achieving datasheet specs
-Making companion PSU PCB-s in future
Input CAP is meant to be polypropylene 4.7uF, power supply is decoupled with 1000uF generic, 22uF organic polymer and 4.7uF X7R caps.
For C3 Nichicon BP cap i suposed to be on the board with the C11-100uF smt 6V X5R.
Grebes are uploaded here.
And here are is the schematic and the PCB layout photos.
Amp is set to gain of 20 db ATM.
I would appreciate your critiques and advice with the layout.
While waiting for my Modulus 286 I decided to have some fun and learn.
After some time spent reading on this forum, reading about PCB designs and @tomchr guide on LM3886 I got inspired and made this LM3886 layout in KiCad with certain goals:
-Making my first CAD PCB
-Making a basic stable LM3886 configuration
-Achieving datasheet specs
-Making companion PSU PCB-s in future
Input CAP is meant to be polypropylene 4.7uF, power supply is decoupled with 1000uF generic, 22uF organic polymer and 4.7uF X7R caps.
For C3 Nichicon BP cap i suposed to be on the board with the C11-100uF smt 6V X5R.
Grebes are uploaded here.
And here are is the schematic and the PCB layout photos.
Amp is set to gain of 20 db ATM.
I would appreciate your critiques and advice with the layout.
That's pretty impressive for a first timer! There's room for improvement, but what you have is better than many of the eBay layouts already.
It looks like you got quite a bit out of reading my Taming the LM3886 article series. That's good to see.
Watch the power dissipation in R4! That'll limit the THD if you're not careful.
Tom
It looks like you got quite a bit out of reading my Taming the LM3886 article series. That's good to see.
Watch the power dissipation in R4! That'll limit the THD if you're not careful.
Tom
250 mW resistor should be fine. However, the SMD resistors used on the board look rather itty-bitty. Many 0805 size resistors can only handle 125 mW, which I would consider very marginal for 80 mW of dissipation, especially if you want any hope of low THD. The resistors on the board look more like 0402 or maybe 0603, hence my comment.
80 mW assumes ±28 V operation. If you up the supply to ±35 V to drive 8 Ω loads, you're looking at 136 mW dissipation in R4.
Tom
80 mW assumes ±28 V operation. If you up the supply to ±35 V to drive 8 Ω loads, you're looking at 136 mW dissipation in R4.
Tom
You could squeeze in two, or preferably three resistors in series for R4.
I try to get the upper leg feedback resistor dissipating <10% of rating when signal is at maximum working voltage.
that would be 20Vac
Three 3k in series for 9k gives 36mW dissipation and 375mW capability.
If the amp output goes to supply rail (assuming protective diode bypass across C3), then 38Vdc across the 9k gives a fault condition dissipation of 130mW. No damage to the resistors, nor the diode, nor the capacitor.
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