Dynavector XV-1s loading question.

Hi Raul, I agree. I'm not stressing the fine details yet but the cartridge is sounding better every day.

Thom, Palasr:

Yes, 28dB is a lot! (25 times greater energy than the flat-response amplitude)

My experience has been that when a low-impedance MC cartridges changes in sound and energy balance due to different electrical loading, what we are hearing are mainly the effects of altered distortion characteristics (particularly intermodulation distortion) in the phono stage, and to some extent, dynamic compression of the cartridge (which is what too-heavy loading will do). The oft-repeated mantra that loading-induced alterations in the sound and energy balance are due to the frequency response in the audible frequency range changing is a myth, because there is no measurable sign of this happening. OTOH, factors that I don't see normally mentioned will cause significant changes in the measured frequency response, such as when the ambient temperature changes by a few degrees, or where on the LP the cartridge happens to be tracking (groove radius).

I should now debunk another myth regarding loading, which is that low-impedance MC cartridges are insensitive to capacitive loading. OK, the MC cartridges themselves aren't particularly sensitive to capacitance, but the inductance of the cartridge coils will resonate with the distributed capacitance of the coils and the capacitance of the tonearm cable to create a high-frequency spike, and this spike certainly is sensitive to capacitance. In general, the less the capacitance the better. Having more capacitance (across the plus and minus cartridge outputs) will increase the magnitude of the high-frequency spike and lower its frequency, neither of which is good news for phono stage stability or phase response.

Generally speaking, the greater the capacitance across the plus and minus cartridge outputs, the heavier the resistive loading needs to be to control the resulting high-frequency spike. Conversely, less capacitance allows the resistive load on the cartridge to be reduced, which will benefit dynamic range, resolution and transient impact.

From the above we can deduce that tonearm cables for low-impedance MCs should have low capacitance. As a test, some time ago I built some 5-pin low-capacitance tonearm cables of 1.2m length (configured for use with a Graham Phantom). Including 5-pin and RCA connectors, the smallest-capacitance versions got down to 32pF, there was an intermediate version at 42pF, and the highest-capacitance version had 50pF. I felt that these low-capacitance tonearm cables resulted in greater flexibility in loading, a more natural tonal balance with better dynamics and resolution, and were a worthwhile upgrade.

hth, jonathan carr (preamp and cartridge designer)

PS. The possible frequency range occupied by the high-frequency resonant spike also includes the frequency range encompassed by LP pops and ticks, and these can likewise be of quite large magnitude (larger than any music signal inside the groove). Just as with the high-frequency resonant spike, controlling pop and tick energy is the task of the phono stage (although it is a big help if the cartridge has a low-mass moving assembly). The phono stage and cartridge can have an immense influence on how "noisy" your LPs appear to be.

The load will generally reduce capacitive effects in the cable, so I have been an advocate of cartridge loading on this account, so long as the load does not over-damp the cartridge.

If handled correctly, this means that the phono cable will not have any significant contribution or degradation in the sound of the phono!

I am thankful to Jcarr's for his last post; its an uphill battle getting people to understand that the preamp does indeed play a role in the severity of ticks and pops, so its nice to hear a cartridge manufacturer acknowledge that.

Jonathan, Ralph ... thanks, as always, for jumping in. You always force me to get back to the raw numbers that always explain what I'm hearing.

I think the best we can hope to accomplish, in advising our customers, is to outline the general principles (as we have all done) - providing basic guidelines for fine tuning.

Both of your comments serve to me as objective validation of what I'm hearing, and justify the obtuse answer I always on give loading: "it depends".

So, what we've (re)learned here:

1. All of the capacitances in the cartridge to preamp path (interconnect, Miller capacitance, etc.) contribute to, and interact with the inductance of the coils to create a resonant tank circuit (look it up, if you're interested). This tank circuit can challenge some RIAA stages more than others, and we run the risk of shooting the messanger (the cartridge), instead of the overall solution.

2. The capacitive component of this tank circuit can be altered with a resistive load (look up "RC filter" and "time constant"). Loading can either be the "correct" solution, or a Band-aid.

3. "Just enough" is always the best solution to all of your adjustments. Exercise a delicate hand in applying any adjustment, whether it's loading, anti-skate, tracking force ... whatever.

4. Re-visit your adjustments when you apply a system change. This element was (obviously) most responsible for the wild variance I've experienced with the XV1s loading (anywhere from 35 ohms, to wide open at 47K). Re-investigate whether or not you were using loading as a Band-aid.

5. RIAA stages can go into hissy-fits (pun intentded) if they're not up to the task of handling any of the above. A good design will be more immune to much of the above, but again, the designer has to have a light touch with his implementation, because the "just enough" philosophy applies here as well as it does with the end user in his analog adjustments.

6. This is a great forum, and I learn a lot here, by thinking out loud, and in public. We should not however, underestimte the value of a good dealer to help you save time and money in navigating this minefield we call analog reproduction. They can save you countless experimental iterations (dealer disclaimer) Sharing anecdotal information is extemely helpful, but it is highly unlikely that any two audiophiles will have every element in their signal path identical to one another, so this advice needs to be understood in that light.

Cheers,
Thom @ Galibier

Oooo ... wait a minute! I re-visited items 1 & 2 (resonant tank circuit).

The formula for resonant frequency is given by:

res. freq. = 1 / [2 * pi * sqrt (L * C) ].

I believe this is the net capacitance, but what I'm not clear on is whether the resistive load is taken into account - whether we're talking about the net capacitance as defined by the RC circuit (including the resistive load), or whether the only effect is the raw capacitive elements - without taking the "R" (resistive load) into account.

I believe it takes the resistive load into account, but perhaps Ralph can answer this question for us.

Cheers,
Thom @ Galibier