Just adjust the offset prior to connecting the output to your real load. 🙂
Things should be just fine.
Cheers!
Russ
Things should be just fine.
Cheers!
Russ
Thanks Russ, I'm going to try to air wire inputs and the output tomorrow night and see how it goes.
Setup of the Placid was very straightforward, the only "trouble" that I had is that adjustments to the output affected the other target value (the CCS pots) but I decided not to worry about that until the output of the PS is loaded.
[edit]One more question - any issue with using a 50k pot? I just looked in my parts bin and that's what I've got.
Setup of the Placid was very straightforward, the only "trouble" that I had is that adjustments to the output affected the other target value (the CCS pots) but I decided not to worry about that until the output of the PS is loaded.
[edit]One more question - any issue with using a 50k pot? I just looked in my parts bin and that's what I've got.
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It won't hurt to use he 50K, but your offset may vary a lot with depending on your feedback Rs.
AC coupling should resolve that.
Just watch the offset with varying pot positions.
Cheers!
Russ
AC coupling should resolve that.
Just watch the offset with varying pot positions.
Cheers!
Russ
Yeah, yeah, I know I'm slow...
So far I like what I'm hearing via headphones and I'll be plugging it into my soldering rig later tonight as a preamp.
So far I like what I'm hearing via headphones and I'll be plugging it into my soldering rig later tonight as a preamp.
Nice work! You did a great job. It's not about how quick it happens, but how much enjoyment you get out of the whole deal. 🙂
Cheers!
Russ
Cheers!
Russ
Thanks Russ, it's 95% done. I'm waiting on an latching switch to replace the mistakenly bought momentary one currently occupying the front panel and I also have a bit of fab to do on the top and bottom panels to provide ventilation for the Placid.
Russ/Brian,
I'm having some ground loop issues with the amp, especially when I try to use it as a preamp. Any suggestions or advice for a recommended scheme. I can provide more detailed internal pictures as well as spell out what is connected to what if that would help.
I'm having some ground loop issues with the amp, especially when I try to use it as a preamp. Any suggestions or advice for a recommended scheme. I can provide more detailed internal pictures as well as spell out what is connected to what if that would help.
Check that there is no continuity between the chassis ground(mains earth) and the power ground with an ohm meter.
A connection here can occur in some unexpected places. For example the volume pot.
Cheers!
Russ
A connection here can occur in some unexpected places. For example the volume pot.
Cheers!
Russ
Russ,
Currently the "mains earth" connection at the IEC is floating so there's 0 chance of there being a connection since it's literally unconnected.
Ok, good, then look next at the power ground. There maybe being an undesired loop from some piece(lot of options here) and the chassis.
Russ,
That's just it, nothing is tied to the chassis right now and maybe that's the problem. But there's definitely a loop somewhere since if I tie the GND terminals on the in/out side of the board to the power supply GND connection the noise all but goes away. There's still some hum at that point but I think that may be due to the close proximity of the transformer and there isn't much to be done about that at this point.
That's just it, nothing is tied to the chassis right now and maybe that's the problem. But there's definitely a loop somewhere since if I tie the GND terminals on the in/out side of the board to the power supply GND connection the noise all but goes away. There's still some hum at that point but I think that may be due to the close proximity of the transformer and there isn't much to be done about that at this point.
I had a thought regarding grounding that I wanted to run by folks - since I'm using the Ventus with SE inputs I have input ground wired it IN- as directed earlier in the thread. I'm guessing that this is part of what is causing my loops, that the actual inputs don't end up grounded this way. Should I connect (via a short jumper) the IN- to GND?
Hallo Russ and Brian,
Have You measured the amplifier THD at various frequecies and loads?
And what about slew/rate and noise?
Thank You and Best Regards.
semola
Have You measured the amplifier THD at various frequecies and loads?
And what about slew/rate and noise?
Thank You and Best Regards.
semola
Just in simulation. I would have to send it to someone who has better testing gear than mine. 🙂
Does this mean I could (should?) leave the output caps off the Opus I'm going to use as my source input?
Just so I'm sure (being a newbie), that's C5, C6, C7 and C8? Or do I need to take out C9, C10, C11 and C12 as well?