Just some recent thoughts on preamps with GC.After having tried various pre's i.e.Pass BLS , op-amp buffered types etc I have come to the conclusion that they can sound initially better in every way particularly because of a perception of increased dynamics and bass.However...... recent auditioning again between them and passive types sugest that a certain harmonic purity is lost in the process.Ok you might need to turn the volume up a tiny bit extra for the dynamics but overall now I am back to listening with a passive device.I feel that if you tweak the gain up on the GC a little bit more the dynamics are better and of course the feedback is less which is a good thing and leeds to a more natural presentation.
king30 said:
I don't plan to make gerber files, and I don't even know how to make them. 😉
I just plan to send the .brd file to www.olimex.com
They process .brd files and their price is good.
Current status:
(only change from last post is that I've drawn the wire links in the silkscreen instead of the top layer).
(only change from last post is that I've drawn the wire links in the silkscreen instead of the top layer).
Does anyone have more comments on my PCB?
When just using one pair of electrolytics, do I have to use something like 200uF instead of the 100uF like planned when using two pairs?
Are the BUF634 and the OPA627 close enough now?
I'll guess I'll have to build it to get an answer to all questions 🙄
When just using one pair of electrolytics, do I have to use something like 200uF instead of the 100uF like planned when using two pairs?
Are the BUF634 and the OPA627 close enough now?
I'll guess I'll have to build it to get an answer to all questions 🙄
100uF shoud be fine and yes, I think that is close enough to avoid problems.
So build it and let us know what it sounds like 😉 (Not that I am doubting the findings of Carlos FM etc 😱 )
So build it and let us know what it sounds like 😉 (Not that I am doubting the findings of Carlos FM etc 😱 )
Heatsink
What spec should the heatsink for the BUF634T be in wide-BW mode and a +/-18V supply?
Something like 20 C/W, 10 C/W or 5 C/W?
What spec should the heatsink for the BUF634T be in wide-BW mode and a +/-18V supply?
Something like 20 C/W, 10 C/W or 5 C/W?
heatsink capacity
That would depand on your supply voltages. If you use +/- 15V the power dissipation of BUF would be just around 0,5 W.
With an ambient temperature of 20 Celsius and a 20k/W heatsink the BUF would heat up to about 30 degrees.
In my preamp the BUF are only lukewarm. So any heatsink will do.
Abo
Oops I just saw you use 18 V supplies. The power diss. of the device will increase up to around 0,55 W. That's all. Use any heatsink that fits and you'll be fine.
That would depand on your supply voltages. If you use +/- 15V the power dissipation of BUF would be just around 0,5 W.
With an ambient temperature of 20 Celsius and a 20k/W heatsink the BUF would heat up to about 30 degrees.
In my preamp the BUF are only lukewarm. So any heatsink will do.
Abo
Oops I just saw you use 18 V supplies. The power diss. of the device will increase up to around 0,55 W. That's all. Use any heatsink that fits and you'll be fine.
Thanks. I got to the same figure myself (18Vx2x15ma), but I thought the dissipated power went up when you turned up the volume.
It does. Depending on load resistance.
But in normal operation as a preamp or cd buffer, the buf will stay in class A operation, and dissipation will not increase.
And it's better for sound too...
PS: I wouldn't go as high as 18 volts myself. For most opamps this approaches the absolute maximum rating which is never good. I've heard of opamps failing even below that value.
In my experience, increasing supply voltages over 15V will not improve sound.
But in normal operation as a preamp or cd buffer, the buf will stay in class A operation, and dissipation will not increase.
And it's better for sound too...
PS: I wouldn't go as high as 18 volts myself. For most opamps this approaches the absolute maximum rating which is never good. I've heard of opamps failing even below that value.
In my experience, increasing supply voltages over 15V will not improve sound.
hi carlosfm,
i have built a stereo version of this preamp but have yet to test it. i would like to know the effect of having R11 in circuit but R10 and R12 removed.
thanks,
i have built a stereo version of this preamp but have yet to test it. i would like to know the effect of having R11 in circuit but R10 and R12 removed.
thanks,
Anyway - R12, if used, should be placed at the end of the output cable. I recommend to try R10 and R12 resistors, this makes considerable sonic improvement.
Somebody is shooting down the pigeons between Singapore and Europe.
I have drawn a line of flight on a map and it passes over you guys in India Ashok. Is there a new trend for pigeon curry? 😉
I have drawn a line of flight on a map and it passes over you guys in India Ashok. Is there a new trend for pigeon curry? 😉
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