Analog_SA: Was this problem solved eventually?
I see two dancing lines on my scope moving, as you can see here (http://www.youtube.com/watch?v=xiHFP1aqjbQ). This is taken with 20mV/div. The pcb's were placed under a box to minimize airflow. If I take the box off, the lines are off the chart.
Normal or not normal?
Bingo! Thanks........
Hi, this is the R2 layout, the R3 layout is identical except it has the input offset trimmer right next to the input connectors.
R43a-b are left of that, and reducing them gives the servo more "authority". This will help reducing the output fluctuations a little bit. You can try values down to 10k, i would not go any lower than that though.
You may also want to reduce the servo time constant, by reducing C5 to 470nF or 220nF, but at some point this will eat into the bass signals, basically acting like a rumble filter, and this is not the best-sounding way to implement that, according to the master...
Let us know if this helps!
Analog_SA: Was this problem solved eventually?
I see two dancing lines on my scope moving, as you can see here (Scope - YouTube). This is taken with 20mV/div. The pcb's were placed under a box to minimize airflow. If I take the box off, the lines are off the chart.
Normal or not normal?
normal, according to my measurements. just be careful with those DC-coupled 1kW subwoofers
You must be joking. Are you pulling leg of the builders? You consider this "normal"?
Yes. With 10k in parallel to the original resistors offset is now a few mV. As Salas mentioned in an earlier post during power on and off this goes off the scale, so a muting relay with a slow on, fast off is required.
normal, according to my measurements. just be careful with those DC-coupled 1kW subwoofers
Guess what my system looks like....... (Currently building a dcb1 as preamp)
Listening the first time... far too early for a verdict but so far very nice. Detailed and exact but not at all overly analytic or harsh. I have to resist the temptation to make it louder. And then louder.
Servo voltage came down to 4/6 Volts after implementing the "real" RIAA network. Output offset still wanders a bit within 100mV but I decided to not worry about it (and switch on the power amps last).
I had to move the PS aways from the ampifier and now its surprisingly quiet even with no ground from the TT connected.
There could be a bit more gain - right now I'm using the nCores but I suspect when I use my belowed F4s I will not have enough gain. I'll worry about that later...
Servo voltage came down to 4/6 Volts after implementing the "real" RIAA network. Output offset still wanders a bit within 100mV but I decided to not worry about it (and switch on the power amps last).
I had to move the PS aways from the ampifier and now its surprisingly quiet even with no ground from the TT connected.
There could be a bit more gain - right now I'm using the nCores but I suspect when I use my belowed F4s I will not have enough gain. I'll worry about that later...
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Use AC coupling somewhere in the chain when with DCB1 and DC prone at times source. If the amp has an input cap already your speakers are safe.
I have to resist the temptation to make it louder. And then louder.
I had a Deja vu with it, reminded me a Nak on Dolby C for tone overall.
A little on makeshift hook up. Common central raw PSU is ruled out, it really needs double mono. I preferred the flattened EQ. Its tame enough for transimpendance BJT. Its center of gravity is mid bass I guess. More like an easy force kind of sound. Not that spectacular but reliable. Like a good deck on Dolby C allegorically.