Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: pro_crip on July 29, 2010, 09:23:10 AM
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Based on various postings here and there and a nice low price of 80 or 90 bucks I picked up said cartridge to use in my Project Debut iii. According to Shure's directions it's happiest with a 47K ohm load. Would this be the 47k resistor that goes from T19u to T20u (page 65, top step)? I looked at the schematic and based on my (very) limited knowledge of electronics, it looks to be the case and I just want to make sure it is. Thanks
Rich (continuing a theme)
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That is all correct.
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Those are the same terminals you can also apply a cartridge loading capacitor across. They would go in parallel with the resistors. The Shure V15 in all iterations wanted a little extra capacitance. Somewhere PJ tells how much capacitance the Eros has on the inputs, you add your cables and come up with the additional capacitance you might want to try.
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Eros has very little capacitance itself due to the pentode input tube. Perhaps 10pF would be a good estimate.
(Seduction, which has a triode input, has Miller capacitance in addition to the usual stray capacitance, total probably around 60pF.)
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According to Shure's specs, it wants 3-400 pf of capacitance. The instructions said to include the capacitance of the tonearm but when I checked the specs included with the Debut iii, the capacitance of the tonearm wasn't listed. But those silver-mica caps are available in those sizes, maybe I'll grab some soviet surplus. I love the look of them, I got some .1 microfarad caps just waiting to be coupled somewhere. I guess not here though. Off to Ural Spirit (Dimitry is a good guy) with me.
Rich
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Something that small is only available as a silver-mica, huh? My usual kommie surplus dealer doesn't have anything that small so I'm off to somewhere else.
Rich
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Here's a tip - I have not tried these yet, but VoltSecond says that type COG (formerly NPO) ceramic caps are excellent. Ceramics have a bad reputation based on the high dielectric constant versions, Z5U and X7R. I have a lot of confidence in VoltSecond's thoughts on sonics as well as engineering. (He isn't posting a lot lately - something about having a kid in teh house ... :^) If they behave like other caps, look for copper leads rather than copper-clad steel - or at least keep those leads very short.
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According to Shure's specs, it wants 3-400 pf of capacitance. The instructions said to include the capacitance of the tonearm but when I checked the specs included with the Debut iii, the capacitance of the tonearm wasn't listed. But those silver-mica caps are available in those sizes, maybe I'll grab some soviet surplus. I love the look of them, I got some .1 microfarad caps just waiting to be coupled somewhere. I guess not here though. Off to Ural Spirit (Dimitry is a good guy) with me.
Rich
Rich,
I have heard good things about the sounds of the KK Mica caps a in brown rectangular package. There was an article on their improvements to cartridge loading in a magazine I read in the last year, can't remember which. That article made me look into what my Grado wants to "see," the response from the Grado site was, "Grado cartridge need no capacitor." Seriously! I gave up.
I bet there is someone out there who knows the pF/Ft for the Rega arm and leads. It probably has been posted. I got some really small value capacitors, polyester I think, from Marshland (??) Electronics.
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The prices of caps in these sizes is cheap enough for me to do some 'sperimenting when I finally get around to building my eros. My usual guy has some pio's in that size as well. Slightly OT, but where's a good place for a noob to educate himself on TT and cartridge set-up?
Rich
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If they are available and cheap you can hand match the caps you select for your phono input.
There is a lot of information out there about TT setup. If your table comes with a factory arm the adjustments are minimal. If not, then there is arm positioning, minimum tracing distortion arcs, protractors, VTF, VTA, SRA and other initials that can give you a headache, me too!
I'll see if I can find a few links to better information.
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This has some good info, http://www.audiophilia.com/features/cartridge_setup.htm I also purchased this tool. http://www.mintlp.com/best.htm
might be a little expensive but worked very well. There is oodles of info out there as I'm sure you know. PS the Eros is fun to build just take your time, double check everything and by all means NO cold solder joints, they should be shiny. Good luck and you're in the right place for expert help