Ay.... being cute but missing the point!! I'm quite serious.
I intend on keeping with rolling opamps.
I took the lid off the previous iteration of my P3. Because it was not a structural piece, I just left it on top and took it off as needed.
Sometimes I'd swap op amps three times per day.... ( now, don't call me psychotic... we're all audiophiles here ).
Ideally, I would not need any tools, perhaps four thumbscrews on the top lid that make it easy to pull off and on. No need to pull it off the shelf.
Hence my question, as the pictures are not clear. Is the lid its own piece or is it part of the sides as well (an inverted U shape )?
What kind of screws are they?
Maybe I'll get another lid for it and cut holes above the DIP sockets so I can reach in and out?
Another question... has anyone heard any deleterious effects by stacking op-amp sockets? I don't want to plug directly onto the sockets on the board. In the past, I had a second one right on top of it (socket over socket) so it minimizes the wear on tear on the soldered parts and the op amp on a 3rd one. That the main wear and tear was on the middle one, leaving the op amp proper in a low connection interface.
Maybe I need the Fabulous Audio Miracles Reference op amp digital interfaces Mk III with cryogenic single crystal treatment ?
But seriously, I am serious, I have noted that it's quite important to make good contact in that interface. I have run into noise in the past.
I intend on keeping with rolling opamps.
I took the lid off the previous iteration of my P3. Because it was not a structural piece, I just left it on top and took it off as needed.
Sometimes I'd swap op amps three times per day.... ( now, don't call me psychotic... we're all audiophiles here ).
Ideally, I would not need any tools, perhaps four thumbscrews on the top lid that make it easy to pull off and on. No need to pull it off the shelf.
Hence my question, as the pictures are not clear. Is the lid its own piece or is it part of the sides as well (an inverted U shape )?
What kind of screws are they?
Maybe I'll get another lid for it and cut holes above the DIP sockets so I can reach in and out?
Another question... has anyone heard any deleterious effects by stacking op-amp sockets? I don't want to plug directly onto the sockets on the board. In the past, I had a second one right on top of it (socket over socket) so it minimizes the wear on tear on the soldered parts and the op amp on a 3rd one. That the main wear and tear was on the middle one, leaving the op amp proper in a low connection interface.
Maybe I need the Fabulous Audio Miracles Reference op amp digital interfaces Mk III with cryogenic single crystal treatment ?
But seriously, I am serious, I have noted that it's quite important to make good contact in that interface. I have run into noise in the past.
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well... there used to be "low insertion force" or "zero insertion force" sockets on computer PCBs for CPU upgrades...
We are all safe, thanks for asking 🙂 Unfortunately, can't say the same for people in Romagna, the situation is quite dire there (I live and work in Emilia)
@tonyEE The top cover is separated from the rest of the chassis, in order to mount it you should put the provided nuts in the "rails" of the side panels then screw the bolts from above the cover itself
The lid is its own panel. The side rails are aluminum extrusions, (2) M3 nuts are in the rail and the top attaches to it via M3 screws. Thumbscrews are a good idea, they’ll need thread of about 5-7mm. You may have to grind them down or add washers under the head.
I wouldn’t ever suggest stacking sockets as that would introduce 16 points per socket where connections could become intermittent or open, and absolutely will add parasitic capacitances in a high gain circuit… so your experiences of adding noise is completely expected. That said, it might work fine. Post your results.
I wouldn’t ever suggest stacking sockets as that would introduce 16 points per socket where connections could become intermittent or open, and absolutely will add parasitic capacitances in a high gain circuit… so your experiences of adding noise is completely expected. That said, it might work fine. Post your results.
Changing opamps several times a session might be worth trying to add some wires to one of the “see link” (16pin versions) possibly even cutting the lid or base and mounting to that. https://www.amazon.com/HUNGARIEL-Narrow-Universal-Socket-Solder/dp/B0D5NC25Z8
The maximum flexibility approach might be, to hire somebody to create a new Pearl3 PCB layout with Zero Insertion Force sockets at every DIP position. You'd probably require a double-height ("2U") chassis to accommodate the ZIF actuator arms, and perhaps greater chassis width and depth too, if the new board layout turns out to be significantly bigger.
Are there any significant downsides adjusting the RIAA network in the opamp feedback loop by downscaling C4 and adjusting the resistors accordingly? I'm asking this because I have a nice bunch of NOS polystyrenes that I could use for C4, value would be approx 80nF. I've recalculated the RIAA network and simulated the changes, looks good and very accurate in a sim at least.
I share the concern with adding contact points with stacking DIP-8 packages.
I make a lot of SOIC-8 to DIP-8 adapters, and to eliminate the extra contact points between the adapter board and the socket (which is then plugged into a socket on the board), I make sure to flow solder from the pins through the board into the contacts of the socket. If this is then soldered into the main board, there are no friction points, but if plugged into another DIP-8 socket, the high-quality round pins make good contact with the round-pin sockets soldered into the main board.
I've also used thumbscrews on a several phono preamp builds. These are actually captive, with press-collars and springs - they stay in the lid/panel.
OK, some of you can start laughing now. I'll dip my toe into where it has no business.
It's my extremely limited understanding that (some) op-amps, particularly high speed op-amps work best with some sort of (insert technical term here) cap that ideally is in very close proximity to certain pins to maintain stability. It's also my understanding that the insanely brilliant people that design the PCBs take this into account.... but... moving on...
A similar (I think) situation has arisen with certain power amplifier output devices that we may want to mount "remotely" and/or not all PCBs align with a UMS pattern. Some super-clever person came up with a PCB that had some pads to accommodate MELF-style resistors (for the gate or source... I don't remember) that similarly keep that resistor in close proximity to the output device regardless of its mounting position away from the "main" PCB using flying leads (or whatever).
Would something similar be of benefit here? Separate from contact / resistance / consistency, is there a potential benefit from having the spot for the cap on those adapter boards?
I truly have no idea whatsoever... If this has no merit for discussion, just move along with my thanks for reading this far. 🙂
It's my extremely limited understanding that (some) op-amps, particularly high speed op-amps work best with some sort of (insert technical term here) cap that ideally is in very close proximity to certain pins to maintain stability. It's also my understanding that the insanely brilliant people that design the PCBs take this into account.... but... moving on...
A similar (I think) situation has arisen with certain power amplifier output devices that we may want to mount "remotely" and/or not all PCBs align with a UMS pattern. Some super-clever person came up with a PCB that had some pads to accommodate MELF-style resistors (for the gate or source... I don't remember) that similarly keep that resistor in close proximity to the output device regardless of its mounting position away from the "main" PCB using flying leads (or whatever).
Would something similar be of benefit here? Separate from contact / resistance / consistency, is there a potential benefit from having the spot for the cap on those adapter boards?
I truly have no idea whatsoever... If this has no merit for discussion, just move along with my thanks for reading this far. 🙂
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No, it's a good question, IAIMH. Local rail bypass caps are recommended by the manufacturers for many/most high-speed op amps. In the vintage preamps I've worked on and updated, I just add those caps to the bottom of the main PCB, because they originally came with TL072 and had no bypass caps. Unfortunately, in most positions, there is barely enough room for the adapter board, so making it larger for the bypass caps won't work, but that surely isn't the case with other situations.
I've made really tiny adapter boards for mounting SMD JFETs to through-hole PCBs, so I might see if I can come up with something you have envisioned.
I've made really tiny adapter boards for mounting SMD JFETs to through-hole PCBs, so I might see if I can come up with something you have envisioned.
^ I appreciate the reply and the consideration for a novice question. Learning "what matters" about certain aspects of design is making me go (even further) gray.
Edited to add - Going right to the end of the pier (or plank) ... maybe using an SMD cap on the adapter board is an option vs. a (relatively speaking) big through hole film cap. Again... I truly haven't the foggiest of clues. However, it is fun to see that some aspects of design can carry across "themes".
Edited to add - Going right to the end of the pier (or plank) ... maybe using an SMD cap on the adapter board is an option vs. a (relatively speaking) big through hole film cap. Again... I truly haven't the foggiest of clues. However, it is fun to see that some aspects of design can carry across "themes".
Thanks for adding this @rhthatcher. I was answering the question generically, though it doesn't apply to the Pearl 3. Or, for that matter, most circuits designed for high-speed op amps, since bypass caps are generally already designed in. Op amp rolling is much more straightforward with this phono preamp!
@ItsAllInMyHead - most local rail bypass caps for fast op amps for stability are around 0.1 - 0.01uF, generally ceramic. Small, even with TH, but much easier to design for SMD if making a new adaptor board for other situations.
Again, not needed for the Pearl 3, but as an example:
@ItsAllInMyHead - most local rail bypass caps for fast op amps for stability are around 0.1 - 0.01uF, generally ceramic. Small, even with TH, but much easier to design for SMD if making a new adaptor board for other situations.
Again, not needed for the Pearl 3, but as an example:
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It’s not the decoupling that will be an issue, it’s the unknown parasitic capacitance from additional sockets and/or flywires that you are introducing into a circuit that has more than 100db of open-loop gain. A few random pF here and there can add up into instability (possibly) and noise (effectively guaranteed).
Everything matters in phonostages when it comes to noise. The most direct and obvious point being the additional headache and expense in putting the PSU in a completely separate chassis, yet things that also matter more than you’d expect include the grounding scheme, sockets, jacks, plugs, resistor choice, wire dress and routing, etc… heck, the difference between the chassis panels being properly strapped to each other or having even one panel floating is audible.
A lot of work was done to make this circuit very quiet, enough for direct amplification of very low output Moving Coil cartridges. This is no small feat. I’d personally not want to mess that up.
YMMV
Everything matters in phonostages when it comes to noise. The most direct and obvious point being the additional headache and expense in putting the PSU in a completely separate chassis, yet things that also matter more than you’d expect include the grounding scheme, sockets, jacks, plugs, resistor choice, wire dress and routing, etc… heck, the difference between the chassis panels being properly strapped to each other or having even one panel floating is audible.
A lot of work was done to make this circuit very quiet, enough for direct amplification of very low output Moving Coil cartridges. This is no small feat. I’d personally not want to mess that up.
YMMV
Thanks, @6L6, for steering this back on target. My responses were about the concept/practice in general, but I totally agree - there is no need to either add additional parasitic capacitance or other opportunities for noise/RFI with this phono preamp.
Thanks, Randy!
Yep, with my lack of understanding of the technical terms, you've described much more clearly what I could not.
What I was wondering (out loud amongst friends) was with this insanely high-gain circuit that performs so darn well, if those "remote" adapter boards for the Op-amps may benefit from having those critical caps mounted on the adapter board vs. the main PCB.
Anyway, I've learned A TON from you, @GKTAUDIO, and @6L6 in a few posts.
You guys rock!!!
