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Variable phono input loading

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 23 Aug 2010 at 10:06pm
Check this link: http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2404707

You'd have to do a bit of cheating to get through the registration process (trade only...Wink) and then you can order online (like most do... Wink), or if you know somebody...

By the way, 100pf is the smallest value in the range.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 23 Aug 2010 at 10:12pm

As agreed I did a quick snip and solder to put the polystyrene 220pF and Evox 220pF next to each other, then left both connected to op amp input and +9V potential for a few hours. This is an early test.

The Evox is better, it is not about the sound being brighter or slightly harsh on the polystyrene. I think the Evox is easier on the ear. I would normally describe the difference as detail or resolution but it is probably speed of response to transients. The mix is clearer with instruments more distinct and reverberation/delays being audible.

The best example I can give is a hi-hat. With the Evox, the stick hits and foot work can be heard in the mix. The polystyrene rendering makes it more like a ride cymbal, splashier for want of a better word. I am surprised how big a difference this makes.

Both 220pF's are a little trebly with my Goldring cartridge. But choosing between them is no contest! How many years ago did you discover these little gems?

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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 23 Aug 2010 at 10:13pm
Graham Slee wrote:
"Check this link: http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2404707

You'd have to do a bit of cheating to get through the registration process (trade only...Wink) and then you can order online (like most do... Wink), or if you know somebody...

By the way, 100pf is the smallest value in the range."
 

Thank you Graham.
 


Edited by Fatmangolf - 23 Aug 2010 at 10:14pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 23 Aug 2010 at 11:44pm
"How many years ago did you discover these little gems?"

10!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 24 Aug 2010 at 12:22am


Just to clarify because I did get a bit lost for a moment, the curves are thus...

(looking at the right hand end of the chart)

The biggest peak +3.5dB is the pink line into 570pf load (is this the total load, i.e. 100pf wiring plus 470pf cap?)

The next biggest peak +1dB is with the standard 220pf load cap (in parallel with the arm wiring - total 320pf)

The flattest almost as extended response is the 100pf load cap (plus the 100pf arm wiring making 200pf)

The early roll-off - the lowest curve - is with 0pf (plus arm wiring equals 100pf)

Generally, the correct total loading is 200pf for a typical 500mH magnetic cartridge. However, that can cause (to use an old carburettor tuning term) "hunting" where the input slew rate can, in some circumstances, lead or match the phono stage output slew rate.

The 220pf load cap plus 100pf arm wiring is a case of finding some common ground - limiting input slew rate (only slightly though), but with a +1dB peaking around 16kHz (if memory serves me...)

My old favourite was always 100pf (plus 100pf wiring) but over the past year I've felt the 220pf (plus 100pf wiring) better for my tastes. It should also be noted that arm wiring capacitance can vary +50%/- 30% depending on manufacturer (in my experience), and on the Hadcock Integra tone arm... well, I shall say nothing much apart from the peak will go off the Y-axis - but advise that the standard model (with the pig-tails) is better and the user to get a 1.5 metre Cusat50 (sorry about the "plug").

In passing I shall mention the popularity of the Ortofon 220pf adapter plug back in the late 70s. Tone controls had been "abolished" by then... Cool

(with the 220pf adapter plug, a DIN standard onboard phono stage with 220pf loading cap and 100pf arm wiring equaling 540pf there must have been some dull sounding phono inputs back then...Wink)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 24 Aug 2010 at 8:14am

"The biggest peak +3.5dB is the pink line into 570pf load (is this the total load, i.e. 100pf wiring plus 470pf cap?)" Yes it is, and your reading of the other curves is spot on.

The Goldring 2500 I am now using has a higher inductance of 720mH so you will already realise the LC curves are different from the "standard" 500mH. It peaks at 10.5KHz,  lifting 5 - 10kHz like a treble control, and rolls off lower that a 500mH would. For this I am using the formula, Fpeak = 1 / (2 x Pi x square root (L x C))

Goldring recommend 100-200pF total loading, including the cable. Anyway I was curious enough to experiment as described above.

My cartridge and turntable are not exotic or high end, but I know what you mean about the 220pF plus cable loading. That gave a nice emphasis and definition with the Rega Exact. I have experimented here to fine tune it for the Goldring 2500 but it definitely needs the right parts! You were right, of course, about my comparing the 220pF PS with the Evox PFR. I learned the type of capacitor makes a bigger difference to listening to music than a 50% change in the value. My final step is to get some of the 100pF Evox PFR caps to compare to the stock 220pF. And I won't bother comparing with the 100pF polystyrene.

This was a stimulating and enjoyable experience, for which I thank you Graham.


Edited by Fatmangolf - 24 Aug 2010 at 7:55pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 26 Aug 2010 at 7:27pm
Noting again my thanks for Graham's steer on obtaining Evox EFR, here is an update.
 
The Evox EFR 100pF capacitors have now been in the Genera for a day or so. I left them on in parallel with the 220pF's. There is an audible difference between 100pF and 220pF, so I am glad I tried this. It is quite a small and subtle impact on the high frequencies (like a tone control as Graham has pointed out elsewhere) and could easily be masked by a less transparent preamp than the Genera, which is a great design with carefully selected parts.
 
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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