July 10, 200817 yr i've searched a bit, but can't find any specs on the pearl... are gain, load impedance and capacitance adjustable and if not what's it set at?
July 10, 200817 yr Author yes, input resistance and capacitance are user definable. The circuit uses split-RIAA. The second stage has 30dB gain. The first is 29dB minus the RIAA EQ... .. so around 60dB. Here's an excerpt from the service manual: "The phono stage was tested on two different systems with a Grado Sonata (47 Kohms load), a Kiseki Lapus Lazuli (100 ohms load), and a Sumiko Celebration (1000 ohms load) cartridges all of which have outputs in the range of 400 to 500 microvolts. The circuit was quiet and had sufficient gain. A subjective consensus has it that the phono stage offered precise imaging and spatial placement and good depth. Compared with the Xono, the Pass Labs reference, it was slightly noisier, and had less gain. From a sonic standpoint, it acquitted itself well in comparison, lacking only slightly in dynamics."
July 11, 200817 yr So will this work properly with both MM and MC carts, or does the circuit need tweaking to adjust the gain for one or the other?
July 11, 200817 yr Author So will this work properly with both MM and MC carts, or does the circuit need tweaking to adjust the gain for one or the other? it has fixed gain and will work with MC down to 0.4mV-0.5mV. With MM carts you'll have have that much more gain. No problem with that. The Grado Sonata mentioned is what, 4-5mV MI output? It's been a while since I owned one. I'm planning on using a 2.5-3mV high output MM cartridge.
July 11, 200817 yr I plan on getting an MC cartridge with 2.2mv output. How do you adjust the input impeadance of the Pearl to match the cartridge being used? Or is there any need to?
July 11, 200817 yr Looking at the schematic and the manual, it looks like R27 is the input loading resistor, and is spec'd at 47K. It looks like there is an R1 (also marked RX) position on the board which is in parallel to R27. You could place resistors or caps or both here to adjust the cartridge loading.
July 11, 200817 yr I plan on getting an MC cartridge with 2.2mv output. How do you adjust the input impeadance of the Pearl to match the cartridge being used? Or is there any need to? with the denon DL-110 it would be ideal to match the loading closer to 1K (some even suggest a bit lower) for correct damping of it's hi-frequency range.
July 11, 200817 yr Looking at the schematic and the manual, it looks like R27 is the input loading resistor, and is spec'd at 47K. It looks like there is an R1 (also marked RX) position on the board which is in parallel to R27. You could place resistors or caps or both here to adjust the cartridge loading. When I get the specs on my cartridge, I'll prevail upon you smart guys to help me determine those resistors/caps to match my cartridge
July 11, 200817 yr Author Looking at the schematic and the manual, it looks like R27 is the input loading resistor, and is spec'd at 47K. It looks like there is an R1 (also marked RX) position on the board which is in parallel to R27. You could place resistors or caps or both here to adjust the cartridge loading. close, but no cigar well, lemme qualify that... if it's like the Xono, then note where the words "jumper" appear on the silk ... it'll be easy to adjust the loading.
July 11, 200817 yr Author oh and... stop reading the T-Shirt threads and please pay for your boards. Thanks to the 3 people that already have
July 11, 200817 yr close, but no cigar well, lemme qualify that... if it's like the Xono, then note where the words "jumper" appear on the silk ... it'll be easy to adjust the loading. See em now. There are 2 capacitor locations marked CX each with a location marked jumper plus a jumper location for resistor RX to patch it in parallel with R27 I assume. Neither of which are documented in the manual.
July 12, 200817 yr Author See em now. There are 2 capacitor locations marked CX each with a location marked jumper plus a jumper location for resistor RX to patch it in parallel with R27 I assume. Neither of which are documented in the manual. yup! here's some extra credit: what's the optional 9v battery input for? hint: it's not documented in the manual either. edit: I guess it's on the schematic... oh well...
July 13, 200817 yr Author last call for the 2 people who haven't paid. You have until midnight tonite (7/13/08 12:00 central) to pay, otherwise there's not much I can do. Sorry about that.
July 14, 200817 yr Author payment sent...sorry for the delay Cheers. boards have been ordered. On the subject of parts, since there's a relatively low number of boards (8 stereo sets) and I'm such a great guy, I'd consider tracking down (some if not all) the parts for people if there's interest. My strategy at this point is to wait on the boards to see if slightly larger parts will fit in a few locations, and then wait until the end of the month when parts connexion announces their next monthly sale. If it's resistors, then that would be a score... and less of a score if capacitors, but anyways. In the meantime I'll get the boards and order the rest of the parts from Digikey. If you're interested in this, then I'll charge you for the Digikey parts once I place the order and then a separate payment for the partsConnexion order. now we wait.... cheers!
July 14, 200817 yr Author one more thing... I will be offering a basic part kit. If you're interested and I haven't already contacted you, then *you* contact me
July 14, 200817 yr Author mods: can we move this to the DIY forum and retitle the thread? I did some research on the transformer today, and here are some options: - Plitron transformer (part number #017017201) 30VAC @ 0.5A 30VA qty 1 = $64.21 US + $23.46 US shipping ($87.67 US each) qty 5 = $304.35 US + $33.89 US shipping ($67.78 US each) - Ebay R-Core transformer (R80-35 0-28-35 X2(1A)、0-5 (3A).0-12 X2(2A)) 100W R-Core Transformer 110V//240V ,Pre amplifier / DAC - eBay (item 250259952059 end time Jul-16-08 01:25:05 PDT) qty 1 = $83.00 US shipped - Avel Y236107 qty 1 = $22.47 + $11.39 shipping ($33.86 each) qty 5 = $21.35 + $13.55 shipping ($24.06 each)
July 14, 200817 yr Moved. You need to let me know what you'd like the thread title to be. Also, you might have a look at sumr transformers. My custom unit for a beta22 will be in this week and I can that up to this point the service has been great.
July 14, 200817 yr Moved. You need to let me know what you'd like the thread title to be. Also, you might have a look at sumr transformers. My custom unit for a beta22 will be in this week and I can that up to this point the service has been great. I have dual Avel Lindbergs for my Dynamite PSU and they work just fine, not sure there is anything to be gained with more expensive toroids. Now a mag sheilded toroid may be of some use in this application...
July 14, 200817 yr Now a mag sheilded toroid may be of some use in this application... That's exactly the kind of thing that sumr can offer, for a lot less money that plitron or Avel for that matter. In truth I've only spoken with Avel about custom one-off trafos before, maybe with a group of some size their shielded options would be more affordable? In terms of stock prices you're right, Avel is probably the best option.
July 15, 200817 yr I'd already moved it to group buys, since it was still mostly about people buying parts
July 15, 200817 yr That's exactly the kind of thing that sumr can offer, for a lot less money that plitron or Avel for that matter. In truth I've only spoken with Avel about custom one-off trafos before, maybe with a group of some size their shielded options would be more affordable? In terms of stock prices you're right, Avel is probably the best option. I'd be in favor of a single trafo powering both boards, vs. dual trafos with about a 50-65% loading.
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