Hi !
I just bought a board for this on Ebay.
Anybody have some experience or comments for this circuit?
Is it any good as a linestage in a preamp?
How does it sound?
Any take on component values before I start soldering?
Any input will be wellcome.
The pws is onboard standard LM317/337 setup🙂
I just bought a board for this on Ebay.
Anybody have some experience or comments for this circuit?
Is it any good as a linestage in a preamp?
How does it sound?
Any take on component values before I start soldering?
Any input will be wellcome.
The pws is onboard standard LM317/337 setup🙂
I use a similar circuit as a headphone amp - in mine the 3K9 resistors are active current sources. It sounds pretty good to me.
I scaled mine up a bit - the output devices are MJE15032/3, because I run it with enough bias current that it is class A for 32 ohm loads. Try your kit, it'll sound nice 🙂
I scaled mine up a bit - the output devices are MJE15032/3, because I run it with enough bias current that it is class A for 32 ohm loads. Try your kit, it'll sound nice 🙂
Good choice! I did the same. I have two of these boards from Jim's Audio. I built one but have not listened to it. I ran some square waves through it and they looked good. I matched the output transistors as well.
No, BC550/BC560, and MJE15032/3 for the outputs. How much gain you'll need depends on your source. I found that for a 2V RMS input, no gain was needed.
Bear in mind that headphones are typically quite sensitive and it doesn't take much output power to blow your head off!
Bear in mind that headphones are typically quite sensitive and it doesn't take much output power to blow your head off!
Tube Cad had a little discusion of using the Diamond buffer in a sort of unconventional way to use it to get 6db gain. To do this you let the center of the powersupply float and connect the output of the buffer directly to ground. Then you can use that center tap of your floating power supply as your output node.
Yeah! The output stage has no voltage gain, only current gain. The voltage is set around the op amp. You can make it what ever you want it to be.
One more question guys.
I know that the gain is R3/R5+1, but how high will I set R3 in Ko in your experience
to get the best out of LME49720🙂
I know that the gain is R3/R5+1, but how high will I set R3 in Ko in your experience
to get the best out of LME49720🙂
I would be very tempted to have a switchable gain.
+0dB, +6dB +12dB. (+0dB would be a direct wired bypass into a buffer circuit.)
and always use the lowest setting that gives adequate volume at your listening position.
But switchable (or any variable) gain leads to variable gain and phase margins. You need to find a way to ensure that similar margins are maintained at all gain settings, otherwise the results (sound output) are likely to be quite different.
+0dB, +6dB +12dB. (+0dB would be a direct wired bypass into a buffer circuit.)
and always use the lowest setting that gives adequate volume at your listening position.
But switchable (or any variable) gain leads to variable gain and phase margins. You need to find a way to ensure that similar margins are maintained at all gain settings, otherwise the results (sound output) are likely to be quite different.
What I meant is the size of R3 F.ex. 100k or 10k or 3k etc. where R5 will be 9times smaller for a gain of 10
I suspect that 100k/11k would have more noise than lower resistances. Try it to hear.
3k/330r would be a quite difficult load for the opamp to drive if there is also a low Zin and some capacitance to be fed. Could the opamp send full voltage signal through without performance deteriorating?
This might be quite difficult (resource expensive) to disprove.
I would be tempted to stick with the 10k/1k1 that is fairly typical of opamp stages.
3k/330r would be a quite difficult load for the opamp to drive if there is also a low Zin and some capacitance to be fed. Could the opamp send full voltage signal through without performance deteriorating?
This might be quite difficult (resource expensive) to disprove.
I would be tempted to stick with the 10k/1k1 that is fairly typical of opamp stages.
The gainlevel can be found with a trimmer in the feedback (R3) and then replaced with a suitable resistor when the right value is found. It is more whether it should be like 90/9k or9/1k or? to give the best conditions for the LME49720
- Status
- Not open for further replies.