I think the layout is fair but somehow I don't like your efforts to create a groundplane. Probably it will work fine but I would still suggest that you have ground under the opamps and two traces with v+ and V-, close to the IC's. I would also suggest compactness and smaller parts if possible.
Maybe you should have the BUF's close to the outputs of the opamps? Try to get the physical layout similar to the schematics.
Why don't you consider a pcb with groundplane? If you are going to make it yourself it's real easy with a groundplane. Just put brown parcel tape on the upper side. Se picture below.
Maybe you should have the BUF's close to the outputs of the opamps? Try to get the physical layout similar to the schematics.
Why don't you consider a pcb with groundplane? If you are going to make it yourself it's real easy with a groundplane. Just put brown parcel tape on the upper side. Se picture below.
An externally hosted image should be here but it was not working when we last tested it.
Alcaid said:
Hi,
Are you sure you need R5 & R15? It negates the effect of the buffer. What's the value of those resistors?
Jan Didden
peranders said:
Now that's an easy way to get a ground plane! 🙂
Maybe I'll do that, and have all ground on top layer.
P-A,
What do you mean by '50 ohms cable'? Surely you don't mean a cable with 50 ohms between the two conductors? Any decent opamp can drive a 50 ohms *characteristic impedance* cable, of course. It all depends on your termination resistor. If this circuit is used to drive a power amp of a couple of K or more input impedance, the buffer is pretty useless. If you want to drive say 30 ohms headphones, the buffer is a good idea, but then you wast more than half your power in R5,15. That's why I asked. It all depends om the application.
Jan Didden
Jan Didden
What do you mean by '50 ohms cable'? Surely you don't mean a cable with 50 ohms between the two conductors? Any decent opamp can drive a 50 ohms *characteristic impedance* cable, of course. It all depends on your termination resistor. If this circuit is used to drive a power amp of a couple of K or more input impedance, the buffer is pretty useless. If you want to drive say 30 ohms headphones, the buffer is a good idea, but then you wast more than half your power in R5,15. That's why I asked. It all depends om the application.
Jan Didden
Jan Didden
peranders said:
Did you get how I have done?
tape
etch
drill a bit with 3-4 mm drill
very easy
Yep, got it. 🙂
janneman said:
I'm going to use this as a preamp for power-amps, not as a headphone amp. Should I leave R5,R15 out?
No that's OK for this application.
I did note that you used the wide band connection for the buffer. That is important not because you need the bandwidth, but it puts the buffer in class A for this application. That may in fact be the advantage of having the buffer here. But for driving the power amp & cable (unless it's a lot, with high capacitance) you wouldn't really need it.
Jan Didden
I did note that you used the wide band connection for the buffer. That is important not because you need the bandwidth, but it puts the buffer in class A for this application. That may in fact be the advantage of having the buffer here. But for driving the power amp & cable (unless it's a lot, with high capacitance) you wouldn't really need it.
Jan Didden
mekanoplastik said:
In the thread I linked to previously someone (don't remember) had positive results with more than one buffer pr. channel. But the again, more buffers and caps would make the board bigger...
If you have 0-10 m cable I think a single opamp will (or can) be sufficient. BUF634 can deliver 250 mA and any good opamp can deliver quite high level into 600 ohms but I admit that a buffer is more "serious". One positive effect might be lower distortion.Alcaid said:
peranders said:
P-A,
Surely you know that those buffers have quite higher distortion than those fantastic opamps, right? The wideband connection helps a bit by putting the buffer in class A, but it still will not come close to the opamp's performance. So, I am at a loss about your remark about the positive effect from lower distortion.
Jan Didden
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