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Phono Cartridge Loading For Moving Magnet?
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jrhughes View Drop Down
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    Posted: 14 May 2012 at 12:34pm
The Ortofon 2M bronze has the following specs:

Frequency response20-20.000 + 2 / - 0 dB


Internal inductance630 mH
Recommended load resistance47 kOhm
Recommended load capacitance150-300 pF

if the Reflex M has 220 pF input capacitance and my arm/cable (it's an OEM RB300) has about 100, the I'm on the outside or just over the recommended limit. I must say that it's an education reading all this, even though I don't understand it all, since there's so much more to matching components that I'd thought. Should I be doing something (?) to try to get the total capacitance a bit lower? It certainly doesn't sound spitty, nor dull. Would sounding dull be a sign that total capacitance was too high?
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jupiterboy View Drop Down
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Hi. First post. Found this thread while searching today. I don't have a Slee product, so please don't throw rocks. I'm also in way over my head, but have enjoyed experimenting with alternative loading for MM carts. I've had some difficulty getting solid specs on my cart, and made some initial errors based on incorrect data.

I'm now running a AT 150MLX happily at 54.7K loading and 117pF capacitance. I have RCA splitters with some Radio Shack resistors soldered in series to get that load, and wonder how much capacitance I've added with the splitters, and also wonder about a final implementation and a better quality resistor than what I now have (5% error).

Anyway, great thread. Thanks for letting me post. Cheers.
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Fatmangolf View Drop Down
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Points: 8998 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 15 Oct 2010 at 7:07pm
If it sounds right, it probably is the right value. But I would also trust a reputable manufacturer to state the electrical loading and arm setup that best suit their cartridge.
 
As I wrote elsewhere in these forums I have my 2500 at the top end of Goldring's 150-200pF combined load and it does sound very good. But thanks to Graham I now think the type of capacitors is a key big factor in the sound.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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tg [RIP] View Drop Down
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Points: 1866 		Post Options Post Options   Thanks (0) Thanks(0)   Quote tg [RIP] Quote  Post ReplyReply Direct Link To This Post Posted: 13 Oct 2010 at 12:54am

A double win then, your fave cap fitted in and the result was what you hoped for, or at least had a reasonable expectation of achieving.

I use a big illuminated magnifier to deal with a lot of circuit work these days myself.

Interestingly, Terratec marketed a phono EQ for computer soundcard input a few years back that included 3 different capacitance settings and 3 gain levels.

Cap levels were 100, 200 & 425pf - did not use it a lot, but IIRC, the 200 loading sounded rather better with an Ortofon OMB 10 that I used with it at that time.

I think there has been some discussion on and experimentation with, various loadings, over at vinylengine for anyone who is interested in reading further.
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Graham Slee View Drop Down
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Points: 16298 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 13 Oct 2010 at 12:05am
Well tg, good idea but I have to wear two sets of specs (spekky six eyes...Ouch) as it is...Wink

My choice for the load plug set (something I've been trying to put together now for the last 12 months) includes the Switchcraft phono plugs (picture on its way soon), and I'd thought my favourite PFR's wouldn't fit, but lo and behold, tried it today, and they fit a treat, and I only had to wear one set of "bottle-bottom" spectacles!

I fitted a 100pf and put it in parallel with the input to a Reflex M which now has 220pf loading, using a Tee adapter (per channel) and it made a difference. The total loading is now near the recommended 400pf for the old VMS20E II with arm cable capacitance factored in.

I'd previously been increasing the tracking weight to try and rid it of the slight bit of spit it had operating into roughly 300pf, but currently the additional 100pf has enabled me to set it to 1 gram (0.8-1.2g specified) - quite amazing, especially considering this is a bog standard Technics arm! Big%20smile

So here we have a case of increasing capacitance to rid a treble peak (instead of what you'd expect). The hunch paid off with this cartridge.

The clarity is staggering and the tonal balance quite fantastic. It's smooth too. Not bad at all for a cartridge of its age - and an MM at that!



Edited by Graham Slee - 13 Oct 2010 at 12:07am
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tg [RIP] View Drop Down
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Points: 1866 		Post Options Post Options   Thanks (0) Thanks(0)   Quote tg [RIP] Quote  Post ReplyReply Direct Link To This Post Posted: 11 Oct 2010 at 12:46pm

Yes, they are - 3mm x 1.6 or thereabouts - should fit in almost any plug.

Don't sneeze while they are loose on the bench though.  Ouch

Chosen by a consensus of DIYers on SQ grounds as bypass caps for a TDA1545 DAC chip.

Bit more pricey than ROTM caps but considered worth it. (in that application at least)

I suppose any kind of film could be OK - it was the size issue I was considering.
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Graham Slee View Drop Down
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Points: 16298 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 11 Oct 2010 at 11:12am
Originally posted by tg tg wrote:

These plugs would have the capacitor across the plug as for a load resistor ?

Perhaps a nice Panasonic 1206 film cap would fit nicely ?




A web search suggests these are surface mount?
That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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