@mhenschel confirming your observation that my little diagram is wrong -- the signal identiification and pin numbers are correct, but I had indeed switched "shield" and "white".
The corrected summary: V+/V-/Ground -- pin 2/3/1 -- red/white/shield.
Thanks again for catching this, and I'm very glad I didn't connect it to my preamp this way!
Attachments
@ekobi
You're welcome.
Actually, while you're rewiring... I'm also unconvinced about the correctness of wiring pin 1 to the signal ground on the board... theoretically it should connect to the chassis directly and by a short conductor.
In practice -- according to all reports -- grounding seems to be as much "art" as science. Conventional wisdom is to try different schemes and use the one that works best in your particular situation.
Let us know what works for you.
You're welcome.
Actually, while you're rewiring... I'm also unconvinced about the correctness of wiring pin 1 to the signal ground on the board... theoretically it should connect to the chassis directly and by a short conductor.
In practice -- according to all reports -- grounding seems to be as much "art" as science. Conventional wisdom is to try different schemes and use the one that works best in your particular situation.
Let us know what works for you.
The power supply with LM7915/LM7815 is going to be stable. There are no decoupling capacitors specified in the design.
It's somehow caused by the preamp. Changed it for another and all seems fine. Thanks for your help 😃.
Hello sagittariusx,
sure, you can use batteries to drive the PEARL 3. But you have to arrange them, that you get a symmetrical
voltage out of your batteries (easy).
From your voltage reference (0 V / ground) 2x 9V batteries in series (=+18 V DC) for the positive voltage and 2x9V batteries in series (= -18 v DC) for the negative voltage. The voltage regulators on the PEARL 3 boards do the rest.
I have done this a few times with phono-pres with very good (silent) results...
Cheers
Dirk
sure, you can use batteries to drive the PEARL 3. But you have to arrange them, that you get a symmetrical
voltage out of your batteries (easy).
From your voltage reference (0 V / ground) 2x 9V batteries in series (=+18 V DC) for the positive voltage and 2x9V batteries in series (= -18 v DC) for the negative voltage. The voltage regulators on the PEARL 3 boards do the rest.
I have done this a few times with phono-pres with very good (silent) results...
Cheers
Dirk
While I understand and appreciate where you are coming from, I have so many projects in the works that I am not looking to add more. If there is a meaningful improvement... I am doubtful, largely based on faith in Wayne's design chops that he would have minimized noise. I realize this is largely a subjective evaluation w/ many variables, speaker efficiency being a big one. Oh, by the way my Pearl is sitting waiting for me to get started on the build, somehow an Aleph J jumped to the front of the assembly line
We were using helping hands and bamboo shiskibob sticks on the BA 2018 line stage....
Wait, I was supposed to actually Read The Fine Manual???
Sigh. I don't know how I missed this.
Excellent point. I ended up running shielded twisted pair from the pads to the connector; shield floating at board, but wired to pin 1 & case of connector; and connector pin 1/case wired to rear panel grounding post. I also wired the power connector shield to the rear panel binding post to eliminate mains hum.
As an aside, I was relieved to confirm that that the differential line driver chips survived being shorted to signal ground for a couple of hours.
The balanced outputs? Great! More precisely, to my ears they work exactly as well as the RCA outputs. I did a relatively brief A/B test by dialing in a 6dB boost on the RCA input to the HPA4 (actually a bit complicated, since the RCA inputs are automatically boosted by 15.8dB, but not important). Over the course of about half an hour, even though I knew which input was playing at any given moment, I really could not hear any qualitative difference between the two. I've been listening to the balanced outputs for much of the weekend, and am pretty confident that they're sonically equivalent to the RCA outputs.
My sense is that the only compelling reason for populating the XLR line drivers is to accommodate long cable runs between the phono stage and preamp (which is my justification). It obviously also frees up an RCA input on the preamp, which could be important, I suppose.