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I have an Ortofon OM20 that I'm using. Since I am pleased with the tonal accuracy and tracking of the cartridge unlike any other, I wish to work with it. What I don't like is it's rising upper midrange and treble response along with somewhat lean bass. I've read about people changing the capacitance of their phono preamps to effectively equalize the sound of the cartridge. How is this done? Do you add capacitors in series with the phono leads? My phono preamp input sensitivity impedance is 2.5mV/47K ohm, 125pF. What values would I use or how would I alter things to roll off the highs and boost the bass of the Orotofon OM20?
Follow Ups:
Typically adding small amounts of capacitance boosts the upper midrange and rolls off the treble at the very high end (15kHz to 20kHz). If you add enough, the treble will start to roll off substantially at a lower frequency, but you don't want that. Take a look at the graph Werner posted plotting changes in frequency response with different capacitance loading with a Shure M97xE (see link below). If anything adding capacitance will boost your Ortofon in the upper midrange region you already find exaggerated and do little, if anything, in the bass region where you want to see more emphasis.
Yet is appears, according to the graph, that the peak is inherent to the cartridge itself or something else in the system. I say this because the peak is there throughout and, ironically, the smallest peak looks like it's the one with the highest capacitance...so I'm not sure I follow you. Alternately, what do you think about the idea of leaving the capacitance alone and just playing with lowering the resistance?
There is a small relative peak around 10kHz, but the cart is down more than 3dB in the 6-10kHz region into 150pF. Adding capacitance brings this region up closer to 0, but by the time you get to 620pF, the cart is starting to roll off completely by 10kHz (not good).
The M97xE is a dark, recessed sounding cart, but it sounds like your Ortofon has the opposite problem, it is probably a little above 0 in the 6-10kHz region. So adding capacitance will likely only make the problem worse. I could be wrong about that, and it wouldn't hurt to experiment. But typically what you would expect is that adding capacitance will boost the frequencies in the 6k to 10k range, which from the way you describe the cart, would not be desirable.
It's possible moving to a lower resistance might help. But I really don't know.
I believe Ortofon recommends 100 to 600pF. I doubt if you'll have to add capacitance. With your preamp, tonearm cable, and internal arm wiring, you're probably somewhere near the middle. Others using the OM series say that a total resistance load between 32 and 42K, does the trick. You can use plugs (like above) to try different values. 400K resistors will net you around 42K. 100K will be around 32K. I suggest trying to avoid additional capacitance. The high end starts to roll off. Capacitors can be loaded in the same plugs if you want to try them.
BIRD LIVES
I find the loading has a big effect. See if you can try lower values.
But also, if you adjust the vertical tracking angle, it may help a lot as well.
"Knowledge is knowing that a tomato is a fruit. Wisdom is knowing not to put it in a fruit salad"
I my experience, it's necessary to adjust capacitance AND impedance loading using a test record such as The Ultimate Analogue Test LP and recording software. Many moving magnet cartridges such as yours will have a steady rise in frequency response around 10kHz with a peak around 15kHz when the impedance is loaded at the standard 47kΩ. I've seen a treble peaks at 15kHz with MM carts at +7dB! This is where the problem is. That peak is caused by two things, 1: an ELECTRICAL resonance (peak) that can be tamed by impedance loading, and 2: a MECHANICAL resonance from the cantilever mass who's treble frequency peak is determined by the total capacitance (measured in pF) of the tonearm wiring, phono cable, and the amount of capacitance at the input of the phono preamp (this spec is often not listed in the phono preamp's manual.)
So, with impedance loading you can tame the amplitude of the peak, and the amount of capacitance an influence WHERE that peak is. The less capacitance, the higher the mechanical resonance peak. Both the electrical and mechanical resonances are likely in the upper treble above 10kHz.
The way a test can be done with the test LP mentioned above is to record the 3 high frequency tests into recording software and look at the waveform. The first test (1kHz test tone) is the reference level. The second test is a 10kHz tone and should match the 1kHz level. The third test is a frequency sweep from 1kHz to 20kHz. Here, you can see where the peak is. Lower the impedance value (example: 47kΩ to 33kΩ or 22kΩ or 15kΩ) to tame the frequency peak and/or the 10kHz tone to as close to the reference 1kHz as possible. When this happens, it will probably induce a frequency dip from 5kHz-9kHz. This is where capacitance comes in. By INCREASING that capacitance, you can lower the mechanical resonance to compensate for the dip in the 5kHz-9kHz range. It might take a lot of capacitance to get that low, and if you get down to that range, it'll likely cause a frequency roll off before 20kHz.
It's a balancing act of compromise, and you just have to put in the time and do that test over and over with different values to get what is a near flat frequency response. It is not possible to get a cart to test perfectly flat in REAL WORLD conditions (you can with math equations though), but it is realistic to get a cart to test within ±1.5dB (which is excellent). If you can do this, I'll be willing to bet your cart won't sound lean in the bass. The exaggerated treble in almost every type of cart has this influence. Unfortunately, not many phono preamps have adjustable impedance, especially ones that go low enough (such as 15kΩ). I have the EAR 324 phono preamp and has the adjustability to neutralize a wide range of MM carts.
Some examples of loading for different carts to measure ±1.5dB are as follows: Shure V15VxMR: 200pF/47kΩ. Shure V15Vx with Jico SAS stylus: 570pF/22kΩ. Audio Technica AT150MLX: 570pF/15kΩ. The pF values listed here is 100pF of tonearm wire/phono cable with the balance from the input of the phono preamp. These carts loaded at these values sound almost identical and sound great. But, it's not necessarily the recommended values specified by the manufacturer!
I hope you find this helpful.
Hell yes, I find this helpful. Do you have any other stock values for various carts that have been pre-determined on file? Your explanation makes perfect sense, though it seems incredibly intimidating and I'm not sure where to begin such a task. This is what it's come down to, though. I think the only way I'm going to find a cartridge I'm happy with is to seek out the best tracker with the most natural tonality and 'tame it'. Are moving coils any different or is it the same principal? Sorry if that's a dumb question, but I'm not an engineer.
I don't have any other charted MM values, but I tested a Lyra Delos (a moving coil) and it too had a high frequency rise, but it could not be made neutral with the step up-transformer in the EAR 324.
When you add the capacitance, do you install it in the preamp or does it go in the signal path? In other words, could I..using clip leads and a handful of caps...experiment with different values and perhaps a cd version of the same lp I'm playing..same mastering...and attempt to tame the cartridge by ear?
I would recommend using a Y-adapter at the phono input to experiment with capacitance loading. When you find the exact value that suits your taste, you can solder it into your preamp or you can continue to use the Y-adapter. Here is a picture of what I'm talking about. These Y-adapters are using resistor loading for a moving coil, but you can just as easily substitute a capacitor for the resistor.
On my preamp, I have 5 choices for capacitance and 5 choices for impedance via knobs on the front pannel. I have never explored using clip leads with caps so unfortunately I can't offer any help here.
Since changing the impedance from 47k-ohm is probably not practical, I recommend getting the phono cable capacitance a low as possible so the peak treble resonance will be as high as possible (although it'll still likely below 20kHz). The lowest you could probably get a 1-meter cable would be about 100-110pF. Then you have to know the capacitance of the phono preamp's RCA inputs. Standard is anywhere from 100pF to 220pF. Again, the lower the value, the higher that treble peak will be. A phono preamp with an input capacitance between 20pF and 50pF will only help you. I think the Manley Chinook actually has a setting for 0pF, but it's too bad it's stuck at 47k-ohm impedance. If you ever have a phono preamp that can have adjustable impedance is when you'd be able to take advantage of adding capacitance instead of subtracting.
Even with all this tech talk, testing by ear may still be more important. A great test is to use the Digital Compact Classics (DCC) gold disc of Van Halen's self titled CD. The currently issued LP by Rhino/Warner Bros. is the exact same mastering (done by Steve Hoffman). For loading, listen to the cymbals. It's likely that without proper loading, the lp will sound bright and have more "air". That's the resonance peak. With the loading values I listed for the other 3 carts, they sounded nearly identical to the CD. The Shure V15VxMR was actually indistinguishable from the CD and is coincidentally Steve Hoffman's reference cartridge in the mastering room. All the comparisons were made from needle drops and their perceived output volume was matched. This is my reference recording for making sure my MM carts are loaded properly.
Edits: 06/18/12
best thing is to put the capacitive loading right on the 47K resistor of the preamp. if you want to get the value just right have it loaded approximately with ceramic caps in parallel with the 47K resistor and add a 100pf trim capacitor. Using a recording that you know well, you can inch up the trim cap. It is almost like adjusting vta, you will know when you got it right, things will be lean and distant when there is not enough load, and suddenly dull and closed up when you overcompensate...between the two the sound will be balanced and natural. The ortofon moving iron cartridges were the most capacitive load sensitive things i ever used...a long time ago i had a VMS 20 and also a VMS 30 and they both had to be precisely loaded. a little change in capacitive load changed the whole sound.
good luck
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
Opus 104
n/t
No matter how people try to help you come up with your own conclusions anyway. It's off-putting.
A forum search reveals "hifitommy" as the one who uses the expression "off-putting". Is Mystman actually hifitommy hiding behind an anonymous username or just a coincidence? You decide.
i am not a troll nor am i mystman. i admit to having used the phrase 'off-putting' but not for whatever reason mystman did.
i KNOW this post is 4 yrs old, just found it.
...regards...tr
What you said makes no sense. Because I ask for advice, then come up with my own conclusions based on either a) my own research or b) the advice I receive or c)a combination of a & b....this is worthy of your contempt?
Or is it that you're offended because I don't follow asinine replies like suggesting I use an Audio Technica cartridge on my Pro-Ject table when in my original post I stated that I was using a Lenco and looking for a warm sound?
Here's my advice for you:
1) Don't read my posts.
2) Shut up.
Trolls are always popping up. Sadly, even here on Vinyl asylum. Your angry response was all he wanted.
n/t
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