Cartridge Loading Questions

baldrick · « **Reply #20 on:** 20 Feb 2010, 04:59 am »

Very interesting. It appears that the M97 follows the ideal model of my V15 simulation fairly closely when loaded to 47K and 250 pF.

What can be learned is that in real life it is important (with this cartridge and I'll wager with many more) there is a benefit to lowering the capacitance loading. Usually this is accomplished by improving the tonearm wiring and improving (and shortening) the interconnects.

It is also apparent that Shure's 47K recommendation is totally out to lunch. It looks like a case of trying to make a cartridge to fit the majority of preamps knowing that very few if any people will change (or even know how to) the loading on the preamps.

What that real life model does not show is the better loading value of 80K and how the M97 behaves with the better load resistance.

neobop · « **Reply #21 on:** 20 Feb 2010, 02:38 pm »

Cartridge manufacturers have no choice but to recommend 47K, the de facto standard. Years ago there were preamps with loading options. There are a few today. 4 ch was loaded at 100K.

Around 60K seems to be the load of choice for the M97. Of course this is system dependant, but similarity of results is remarkable. In general an inductor with a shunt capacitor is a low pass filter, just like a speaker crossover. The net result of too much capacitance is lowering the high frequency resonance peak of the cartridge and rolling off the extreme high end. In general, keep capacitance as low as possible, and tune resistance value for best response. This is most critical with cartridges with high inductance.

Ericus Rex · « **Reply #22 on:** 20 Feb 2010, 04:38 pm »

Is anyone making a phono pre with front panel switchable loading anymore? I haven't seen one since the Counterpoint SA-9 (though I admit I haven't been looking). Seems like a relatively easy feature to incorporate into a design and it's WAY convenient to optimize loading.

BobRex · « **Reply #23 on:** 20 Feb 2010, 05:30 pm »

How much do you want to spend? Manley Steelhead, Gram Slee, Asthetix, Audio Research (last 2 by remote control), McIntosh, Zanden, and of course - assorted others......

That's just off the top of my head.

Ericus Rex · « **Reply #24 on:** 20 Feb 2010, 05:51 pm »

I sit corrected.

exojam · « **Reply #25 on:** 22 Feb 2010, 09:26 pm »

Quote from: neobop on 19 Feb 2010, 11:57 pm

Hi James,
Yes, that's the same thread I linked to previously. If you go to page 5 of the thread, Werner (reviewer for TNT) provides graphs of actual measurements, not models of a Shure M97. You can see the effects of loading - capacitance and resistance. It's a very long thread. But it's very enlightening.

Neobop,

Sorry about that. My eyes must be failing me.

James

BobM · « **Reply #26 on:** 22 Feb 2010, 09:39 pm »

My own personal opinion, but cartridge loading may change as VTA changes. At least by my ears. If the arm is a bit higher in the back then the top end is abundant, and a lower loading helps balance this out, but the bass may be a bit too weak anyway.

If the arm is lower then the bass is more prominent and a higher loading balances out and gives the top end more sparkle (and may actually bring out the best overall sound - I'll have to try this and see).

baldrick · « **Reply #27 on:** 22 Feb 2010, 11:46 pm »

I can't agree with that. There is really only one correct VTA. Compensating for bad VTA with electrical loading is like trying to make a "right" from two "wrongs".

I'd say that the best place to start with cartridge loading is the theoretical correct value, which is based on the inductance and dc resistance of the cartridge's coils. Usually this is published by the cartridge manufacturer. It can then be adjusted for optimum frequency response. Unfortunately the theoretical value for loading is often inadequate because the cartridge's mechanical properties get in the way of its theoretical electrical performance. Although the mechanical performance can improve over time (cartridge break-in) sometimes you just have to pick another (better or more appropriate) cartridge for your table and arm.

Ericus Rex · « **Reply #28 on:** 23 Feb 2010, 12:26 am »

My Oracle manual states that VTA should be adjusted to the user's ear. This would imply that there are many different 'correct' VTAs.

Quote from: baldrick on 22 Feb 2010, 11:46 pm

There is really only one correct VTA.

neobop · « **Reply #29 on:** 23 Feb 2010, 01:01 am »

Cartridge loading changes with VTA. Interesting, but I'd have to say that I too disagree. I can't live without VTA on the fly. It varies from record to record. To me it's much more than relative bass output or sparkle up top. The harmonics change and you can hear when it's dialed in. I don't change it for every record though.

Getting the preferred load for a cartridge is kind of similar, but VTA changes will still be necessary. If you use the M97 as an example, it sounds laid back, mellow at 47K. At 62K the high end is around the same as 1K and below, and the lower treble dip isn't as pronounced. That is, as long as the total capacitance is low. That's in general, not specific to a record.

Housteau · « **Reply #30 on:** 23 Feb 2010, 02:11 pm »

How are you fellows manually adjusting the resistance loading for your cartridges? Are you doing it internally on your preamp, or externally? I have an external loading kit that uses a Y-connector, but that only allows adding resistance and/or capacitance in parallel. For a phono preamp that is set to 47K and cannot be opened easily, parallel resistance can only lower that value which doesn't help one needing to raise it. Also, a Y-adapter adds in capacitance. My Y-adapter is stated at 70pF.

I am not sure for certain what the internal setting for my Cotter is, but it must be higher than 47K, but I am not sure if it is as high as the 500K mentioned in the literature. If it was would it even be listenable? With most material I think it sounds qite nice, but it is too hot for some others. I am out of town now, but will play with some more parallel resistance when I get home to see what happens. Assuming it is set to 500K internally I did add in 100K in parallel last week for a test. In theory I should have had around 83K total. However, to my ears the sound was still dull and very similar to the Pro-ject tube preamp set to 47K. So, I guess I am still not sure what I am working with here.

baldrick · « **Reply #31 on:** 23 Feb 2010, 02:19 pm »

The best place to change the loading is inside the preamp. But since you cannot open yours the second best place to add loading resistors is at the tonearm head-shell right on cartridge leads.

BobM · « **Reply #32 on:** 23 Feb 2010, 02:26 pm »

Well I tried adjusting my VTA and compensating with loading last night and it really wasn't satisfying. I agree that there is an "optimal" VTA where the harmonics gel, but you can adjust the top end to your ear with loading once you've got the VTA set appropriately.

I use a Hagerman Piccolo, which has a dial and variable loading. It really can't be fine tuned completely, because there are set values available to you, but you can get pretty close to "optimal" with the values that ARE available. At least enough to hear the differences easily, by the turn of a dial.

neobop · « **Reply #33 on:** 24 Feb 2010, 12:26 am »

That really is interesting. I have an AHT phono stage. I change impedance with resistors that plug into sockets. After getting to know a cartridge, I might try different loads. I load the AT-440ML at 32K for example. On my system that's where it sounds "right". But, VTA still has to be adjusted sometimes. If you've ever played with VTA on the fly, you can hear it get slightly louder and the tone and harmonics sound better when you get it.

IMO changing load won't correct VTA anomalies. Records are different thickness and are cut at different angles.

Delta Wave · « **Reply #34 on:** 25 Feb 2010, 01:36 am »

Some seriously good info here, thanks guys. It seems we are almost in the same boat trying to tweak our phono stages.

kenreau · « **Reply #35 on:** 2 Mar 2010, 07:40 pm »

I have a related question. My MC cartridge specifies 100 ohms. I typically use an outboard JLTi phono stage that has that 100 ohm load. I am considering purchasing an Integrated amp with built in phono stage that is currently fixed at 1,000 ohms. Reportedly this fixed 1k ohm resistor can be changed out but I do not want to do that prior to purchasing it.

What kind of audible impact would be expected running my 100 ohm MC cartridge into this 1K ohm Integrated amp phono? My notion is it should not mechanically hurt anything, but is that resistor loading variance range significant enough that I shouldn't even bother with the hasle of hooking it up at this time? i.e. it will sound so poorly it is not worth the hassle, or, it is close enough to still get decent sound out of the set-up?

Also - is there any significance to the caliber of resistors to use? It it worth while using a decent Vishay, Caddock or PRP metal film?

Thx,
Kenreau

baldrick · « **Reply #36 on:** 2 Mar 2010, 07:48 pm »

It won't harm anything except maybe the sonics.
You can add loading resistors to the cartridge connection pins right at the headshell to bring the total loading to 100 ohms.
If you add 110 ohms at the cartridge headshell leads (one per channel) you will end up with 99 ohms total loading. Don't forget to re-balance your tonearm.
Use good quality 1% tolerance 1/4 watt metal film resistors. Get small bodied resistors which have lower inherent inductance.
Boutique resistors will do nothing for you except drain your wallet.

neobop · « **Reply #37 on:** 2 Mar 2010, 11:18 pm »

Hi Kenreau,
Nice looking fish you've caught, in your pic.
At 1K the sound will probably be bigger and more dynamic. It might be brighter. As you load it down, toward 100 ohms, it should sound more focused, controlled and detailed. Of course they vary.

What ever you do, don't solder on the clips with the cart connected. I'd recommend putting them inside the jacks of the phono pre. One leg to hot and one to ground. You can get really nice ones from Mouser or Newark. The best IMO are IRC 0.1% metal film 1/4 watt, from Mouser (IRC RC55 series). They cost about $1 each. Depending on your equipment, they can make a significant difference. At .1% you don't have to buy a bunch of them and match em up, either.

analognut · « **Reply #38 on:** 3 Mar 2010, 03:08 am »

Hey! Soldering on resistors at your cartridge headshell sounds pretty bizarre and an excellent way to get into trouble! If you're going to use resistors just plug your TT leads into F-adapters (much neater than the T-adapters you usually see), and then make up plugs of different values you can plug into the 2nd leg of the adapter. You need two F-adapters- one for Left and one for Right. This way you can change loading easily, which you will no doubt do alot until you find the one you like the best! Here is a pic of the one I use. The pic is b/w, although the product is actually gold-plated brass with teflon insulator, available at http://www.ramelectronics.net/

Click "Adapters" under the Audio/video/Home Theater heading at the top of the page and you'll find them on about the 2nd page.

I used the F-adapter with resistors to get the 220/2k ohm switchable MC section of my preamp down to 20ohm for my AT-OC9ML/II. I made up a half dozen different values of plugs. Having different values to easily change back and forth from is a big help! You can Google "parallel resistance calculator" and find a number of easy to use calculators that will compute parallel resistance values for you.

neobop · « **Reply #39 on:** 3 Mar 2010, 04:35 am »

Analognut,
I think the name F-adapter is already taken. But I think solid ones like that are better than the wire ones. A while back when that cartridge loading thread on VE was current, I made a bunch of loading plugs for TheChairGuy. His conclusion was that they're good for finding the right load, but they reduce some high frequency output. Sometimes that can be a good thing though.

I don't know - I use plug in resistors. I agree about resistors at the cart clips - not a good idea IMO.