Good point! What's the thinking on galvanised steel enclosures (junction boxes)?
FWIW I think EMI rejection is important for these low-level circuits, so I'm looking at some form of Faraday cage for the boards. https://hollandshielding.com supply Mu-copper Faraday cases, but they're custom and expensive. They also have the same material as tape or sheet; maybe that's cheaper. Can anyone else suggest suppliers?
Magnetic shielding for the transformer; distance and either a case or a steel barrier.
Magnetic shielding for the transformer; distance and either a case or a steel barrier.
If the 17 volts (dual) you mention, is after the bridge rectifier and without regulation, that dual 17 volts is insufficient for
the Pearl 3. If you want the 7815/7915 on the Pearl3 to work/regulate properly, you need at least 3 volts above their stated
15 volts = dual 18 volts into Pearl3 is the absolute minimum to get a ripple free regulated supply.
Btw..... The Rotel RQ-970BX is actually a decent phono-stage, and even better with a few mod´s.
IMO it would be a real pity to scrap it just for the power supply 😉
The 7815/7915 datasheets say max dropout is 1.1 to 1.3V, depending on which manufacturer you read. 17V will be fine.
As for hacking up the Rotel to use as a case for pearl, I hope the Rotel is not working... it's a nice little unit all by itself. (Pearl 3 is better though, no doubt...) More to the point, is there really room in the chassis? if using the existing PSU, looking at photos online it looks as if you'll need to remove a large portion of the Rotel PCB to get things to fit.
As for hacking up the Rotel to use as a case for pearl, I hope the Rotel is not working... it's a nice little unit all by itself. (Pearl 3 is better though, no doubt...) More to the point, is there really room in the chassis? if using the existing PSU, looking at photos online it looks as if you'll need to remove a large portion of the Rotel PCB to get things to fit.
Forgot to post some internal pics.
At this point: thanks to everyone for the great support and to @wayne for this amp 👍
At this point: thanks to everyone for the great support and to @wayne for this amp 👍
I have a question about the PEM for the Pearl 3. The BOM that came with my kit specifies Schurter DD12.9111.1111. That is a switch rated for 10A that has a filter on it. Given the current draw of the Pearl 3, would a 1 A switch like the Schurter DD12.1111.111 be a technically better match because the filter is designed for a lower current? The data sheets indicate that both PEMs are dimensionally the same.
I am going to build both the Pearl 3 and the Zen Mod Preamp. The same Schurter PEM is said to work for both units. I have the Modushop Pearl 3 chassis and the Modushop Zen Mod chassis. I can tell you the openings for the PEM in the rear panels of those two chassis are not the same size. Will the Schurter PEMs actually fit in both chassis?
Many thanks,
John
PS: The fuse drawer needs to be ordered separately for both of the above Schurter PEMs.
I am going to build both the Pearl 3 and the Zen Mod Preamp. The same Schurter PEM is said to work for both units. I have the Modushop Pearl 3 chassis and the Modushop Zen Mod chassis. I can tell you the openings for the PEM in the rear panels of those two chassis are not the same size. Will the Schurter PEMs actually fit in both chassis?
Many thanks,
John
PS: The fuse drawer needs to be ordered separately for both of the above Schurter PEMs.
Hi John,
interesting point you have here. Because of the better filtering of the lower-current versions, I did actually use in all my preamp builds (and in the Pearl 3 PSU) the 0.6 A version Schurter 5500.2000.
I use a standard filter-less IEC inlet, and mount the Schurter filter on a small proto board adjacent to it.
If it would really make a noticeable difference I can't tell, because I haven't used the bigger filter modules so far. I just went with what according to the manufacturer's specs was most appropriate for my use case 🙂
Of course, the integrated bigger filter sizes are more convenient to use ...
Best regards,
Claas
interesting point you have here. Because of the better filtering of the lower-current versions, I did actually use in all my preamp builds (and in the Pearl 3 PSU) the 0.6 A version Schurter 5500.2000.
I use a standard filter-less IEC inlet, and mount the Schurter filter on a small proto board adjacent to it.
If it would really make a noticeable difference I can't tell, because I haven't used the bigger filter modules so far. I just went with what according to the manufacturer's specs was most appropriate for my use case 🙂
Of course, the integrated bigger filter sizes are more convenient to use ...
Best regards,
Claas
John,
Openings are different sizes as the Pearl mounts the PEM from the outside, where the Iron Pre inside-mounts.
As for a lower rated current PEM filtering better, there may be something to that, however it’s not the kind of thing I’d worry about at all, as any filtered PEM will have a lot of advantage over a non-filtered. Do whatever strikes your fancy.
Openings are different sizes as the Pearl mounts the PEM from the outside, where the Iron Pre inside-mounts.
As for a lower rated current PEM filtering better, there may be something to that, however it’s not the kind of thing I’d worry about at all, as any filtered PEM will have a lot of advantage over a non-filtered. Do whatever strikes your fancy.
Thanks for the input Claas. I prefer to do the theoretically best thing, but I do wonder if it makes an audible difference in the real world. I sometimes wonder if there is an audio pixie somewhere laughing at all of us....🤣
Thanks for the clarification Jim. I wondered what was going on with the different size openings.
I'm going to order two identical 1 A PEMs. They are the same price as the 10 A version.
John
I'm going to order two identical 1 A PEMs. They are the same price as the 10 A version.
John
The Rotel stopped working some time back and I don't have the expertise to diagnose and fix it, hence the plan to remove the section of board beyond the psu and use the power supply and enclosure for the Pearl boards. The chassis is big enough to accommodate this and I'm inserting a steel partition to isolate the transformer. If there is interference then I will relocate the PSU to a separate enclosure. I'm finding that chassis costs are quite high so it seems like a good solution....
Hi,
so... the Pearl 3 sounds gorgeous, it's the best phono preamp for me in the last 40 years, period 😍
Stage, dynamics (DYNAMICS!!!) are great, the whole spectrum is perfect, and there is so much liveliness, unbelievable.
It gives a higher than usual output level, so I have to turn down the volume on my Iron Pumpkin 6-7 clicks, but it's not an issue.
Hum? - very-very slight hum at listening volume in a distance of 20 cm from the speaker, and absolutely no hum audible at my listening position. But I know it's there, so I will make some trials. But again, it's not an issue.
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Congrats on an awesome looking build.
But seems, there´s room for improvement.
My P-3 on 600w monoblocks, tube pre and 97dB sensitive speakers.......... absolutely no hum at all on MC/64dB.
Volume to max = a very slight hiss, that´s all.
A big +1 for your impression of the sound. This really is the "gadget of the decade".
Again...... Thanks @wayne
The Pearl 3 sounding awesome does not surprise me at all. I bought a Forte preamp that Wayne designed back in 1988. It had a phono section that could drive a MC cartridge. I ran that preamp for thirty years and never turned it off (it had no on/off switch). The power supply was attached via an umbilical cord. It never failed and records sounded great. Since then I've built the Bottlehead Eros, tubes4hifi PH16, ANK Signature 2.1, and an Akitika phono pre. I'm running 3 tables in separate systems. And yes, I love phono preamps.
Picture below of my ANK Signature phono pre with my TTWeights GEM modified turntable.
PS: I passed the Forte preamp on to a friend and it's still playing music. Are Wayne and Nelson amazing or what?
Attachments
Ok, starting on the next DIY adventure with the P3.
Major concern was the SMD parts, which after a little practice, seemed to go ok (Q1-Q4 passed testing).
If anyone sees a need to touching up soldering pls let me know. I assume the spillage in the through holes are ok.
What i cant find/dont know how to do is to test the SMD capacitors. Given advice to go no further without testing, that’s my next step.
Thanks in advance!
Major concern was the SMD parts, which after a little practice, seemed to go ok (Q1-Q4 passed testing).
If anyone sees a need to touching up soldering pls let me know. I assume the spillage in the through holes are ok.
What i cant find/dont know how to do is to test the SMD capacitors. Given advice to go no further without testing, that’s my next step.
Thanks in advance!
