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Creating parallel resistance and capacitance kit

S

steelglam

Super Member
Hello, I'd like to finally try and tinker with some parallel capacitance and resistance loading, and to create my own kit. I have never replaced, worked, or purchased capacitors or resistors on my own before, so I'm pretty much a newbie. Hence, I have some questions about creating my own kit, and I'm wondering if folks have any insights and suggestions.

1.) Would the following ten loadings be sufficient for a capacitance kit: 50pf, 100pf, 150pf, 200pf, 250pf, 300pf, 350pf, 400pf, 450pf, 500pf. If not, what other values would you add to the list?

2.) What loadings would you suggest for building a parallel resistance kit? Obviously most phono stages come with a standard 47k loading, so I wouldn't need a 47k loading. I was thinking of building a kit with at least 1k, 30k, and 100k loadings, but I'm not sure if that would sufficiently cover the needs of most cartridges.

3.) I assume one needs to account for any capacitance and resistance added by the RCA plugs and Y-splitters when making these kits. Is that true? If so, are there standard capacitance and resistance values that RCA plugs and Y-splitters have? I assume I would then subtract those values from the loading I desire to arrive at the proper value capacitors and resistors that I need. (e.g., if the RCA and Y-splitter is 50pf, I would need to solder in a 100 pf capacitor to get a 150pf loading)

4.) What kind of capacitors and resistors (brand, type) would you recommend for the job?

5.) Any particularly good RCA plugs and Y-splitters that you would recommend for the job?

6.) Anything else that I am missing, or any other calculations that I need to consider?

Thanks in advance.
 
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The capacitance values look as though they cover just about everything.
You might want to add some more values in the resistance part. Perhaps,
25, 33, 47, 62, 75 and 100Kohm values might work.
 
Other things to consider even with a parallel kit as described by Beatcomber's link:

- Existing capacitance of the tonearm wiring and the cables from the TT. You will only be able to add to this base value so this might affect your considerations. The little patch cable approach in the link would not add a whole lot of extra capacitance, I suspect unless it is implemented with poor quality cable.

- Existing fixed resistance in the phono preamp already. You'll need to do the math for parallel resistances according to what this value is. This may well extend your actual value ranges higher than what you're considering.

Cheers,

David
 
Thanks, folks.

The preamps that I'm using right now have phono input resistances of either: 1.) 47k alone, or 2.) 47k and 100k.

The preamps that I'm using right now have phono input capacitances of either: 1.) 50pf alone, 2.) 100pf alone, or 3.) unclear (I can't find input capacitance info. for my Onkyo P-3030, Marantz 1070, and HK 730).

I checked out Davey's page, but I'm still unclear on a few things. Specifically: A.) How much resistance (and capacitance) the RCA plugs and Y-splitters add by themselves (before soldering in the resistors/capacitors), B.) What the equivalent formula is for capacitance loading, and C.) What kind of resistors, RCA plugs, and Y-splitters he is using.
 
Hi Steelgram,
The Y splitters I use are as good a quality as I could find as they are in the direct signal path. They are manufactured by Phillips and should be found on the bay.
Personally I don't believe the quality of the components in the parallel resistive plug needs to be too lofty. Keeping the overall value matched is important though. The plugs I use are fairly basic affairs and the resistors are std. Carbon 1/4 W (5% accuracy) items.
I do measure them though before soldering to match up the pairs.
I would suggest that the incremental length of the splitters can only offer a modest change in overall capacitance, unfortunately I have no means of checking.

Re. the question of plug values - if you plan to use the kit for MM, MI and HOMC's then I'd recommend building up the range of plugs identified in the website pictorial.

Hope this helps
Good luck
Dave
 
steelglam said:
Thanks, folks.

The preamps that I'm using right now have phono input resistances of either: 1.) 47k alone, or 2.) 47k and 100k.

The preamps that I'm using right now have phono input capacitances of either: 1.) 50pf alone, 2.) 100pf alone, or 3.) unclear (I can't find input capacitance info. for my Onkyo P-3030, Marantz 1070, and HK 730).

I checked out Davey's page, but I'm still unclear on a few things. Specifically: A.) How much resistance (and capacitance) the RCA plugs and Y-splitters add by themselves (before soldering in the resistors/capacitors), B.) What the equivalent formula is for capacitance loading, and C.) What kind of resistors, RCA plugs, and Y-splitters he is using.
Click to expand...

Regarding point B, perhaps this link could be of some use, I've used it in the past with good results:
http://www.vinylengine.com/cartridge_database_tools.php#CartridgeAmpElectricalLoading

The gist of it is that you plug in your inductance and capacitance values, it tells you the optimal resistance, if it matches or is close to the given resistance, then you have the capacitance correct. If not, tweak it until the values match.
 
Maybe a variable capacitor (tuning gang from an AM receiver) and a double-gang potentiometer? You won't know the exact values you have set (unless you have an LCR meter) but if you just want to use the setup with the tweaked values, the numerical value doesn't matter.

You CAN increase the resistive loading above 47kΩ, by adding series resistors. This will reduce the signal level somewhat, but even if you increase the loading to 100kΩ by adding a series resistor of 47kΩ or so, the actual level drop is smaller than the difference in recording level between different records.
 
Off shoot to this I was pondering recently - Would the same type of splitter have any benefit on my cd player analogue audio out? if so what resistor values should I be looking for? or formula on how to calculate them?
 
G'day all, no I don't agree with adding 'series' resistors as suggested. That will indeed resistively 'build up' the resistive input value of the phono stage input, but with considerable penalty in terms of phono cartridge power loss, and especially degraded input noise and signal to noise (S/N) ratio. Regards, Felix aka catman.
 
I agree with Felix, don´t do that, it´s a bad design.
Also don´t trust these calculators for loading, they are never right, the only way is to measure.
gusten
 
catman said:
G'day all, no I don't agree with adding 'series' resistors as suggested. That will indeed resistively 'build up' the resistive input value of the phono stage input, but with considerable penalty in terms of phono cartridge power loss, and especially degraded input noise and signal to noise (S/N) ratio. Regards, Felix aka catman.
Click to expand...

I concede you are right - in principle. But I don't agree with "considerable penalty". I agree the penalty will be there, but small, particularly if you are adding only relatively small series resistances, such as 10kΩ, or thereabouts. Whether the improved performance of the cartridge under such conditions warrants the noise/level degeneration, that's for the experimenter to decide.
 
Thanks for the additional responses, everyone. A couple of things in follow-up.

So, I want to make sure that I understand this correctly. By creating these kits, I will only be able to lower the phono stage's stock input resistance and raise the phono stage's stock input capacitance, correct? (Unless I do what steerpike2 says and add series resistors.)

Let's take my Adcom preamp for example. It's stock phono input resistance and capacitance are 47k and 100pf, respectively. What this means, then, is that if I created a kit like we've been discussing in this thread, I will only be able to use it to decrease the input resistance under 47k and increase the input capacitance over 100pf. Correct?

As for the capacitance added by the Y-splitter/patch cable, DB Systems notes that the Y-splitter in their kit adds 70pf of capacitance by itself. So, for instance, the 250pf plug in their kit actually contains a 180pf capacitor, not a 250pf one. (http://store.acousticsounds.com/d/6...o_Capacitor_Loading_Kit-Turntable_Accessories) That's actually not that small of an added capacitance value when you think about it, especially if you're making a kit that deals in increments of 50pf. Anyhow, that's why I asked the question about how much capacitance was added by the Y-splitter that Dave or others use.
 
My measurements of a solid metal Y splitter showed 11pf, and a solid plastic Y split showed 7pf.

To get meaningful results I piggybacked 6 of them to each other, measured the total C, and divided by 6.

My measurement error is around 3 or 4pf (maybe even a touch more) - but that way the error gets "watered down"...

You need to have a digital multimeter with capacitance measurement capabilities in the pf range.

They are not expensive, but they are not all that common either.

Getting one with inductance measurement capability won't cost extra, but is helpful in working out what the cartridge REALLY has in the way of inductance, and then using that data in the various models...

bye for now

David
 
Wow, David, that is a huge difference in pf between the Y splitter that you use and the one that DB Systems uses. That's why I was so interested in what folks are using. I don't have a multimeter right now and really wasn't thinking about figuring one into my budget to create this kit.

Have folks ever used this splitter, and if so is it good quality? http://www.matelectronics.com/acatalog/MAT_Electronics_RP_2RJ_386.html It's gold plated. I ask because I have to order some other stuff from MAT Electronics, so I was thinking of including some of those splitters in the order if they're good enough for this application. Same goes for the RCA plugs that MAT sells.

Another question that comes to mind: if I wanted to change capacitance and resistance at the same time, I assume I would need two splitters per channel, correct? I know that's adding extra capacitance, so I would have to figure that into the calculations...but that's doable, correct?
 
Thanks, David. I will have to see if I can find either of those splitters from a US vendor.

Is it correct that by creating these kits, I will only be able to lower the phono stage's stock input resistance and raise the phono stage's stock input capacitance? (Unless I do what steerpike2 says and add series resistors.) For instance, if I have a phono preamp with stock input resistance and capacitance of 47k and 100pf, respectively, I will only be able to use the kit to decrease the input resistance under 47k and increase the input capacitance over 100pf. Correct?
 
Absolutely - that's how it works...

Which is why I had my JLTI phono built slightly differently when I ordered it - 500k onboard R (makes it easy to set any R, as whatever R I plug in will be pretty close to the R I actually get!)
I also asked him to remove the phono stage additional C load - so C load is my cables/tonearm, plus whatever I plug in...

Then I spent some hours communing with my soldering iron and making up a box of various C's and R's.


You are on your way :thmbsp:
 
Thanks, David. That's what I thought.

So, next question is: what kind of capacitors and resistors do folks recommend for the job? Something decent but inexpensive ($1.00 or less per cap/resistor).
 
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