Anyone using a Lyra Delos yet?

Hi Byron:

Sorry for making you wait for a reply. To give you the short answer first, the Delos should work with the PhonoCube just fine. The PhonoCube uses what is called "current-mode" topology, which is a very similar configuration to the I/V stage in many DACs. I believe that the Dynavector P-75 is also of this type. This kind of circuit has three characteristics worth keeping in mind.

1. The circuit varies in gain depending on the impedance of the cartridge coils. There is a main feedback resistor inside the circuit, and the gain is the ratio of this resistor to the cartridge resistance. The lower the cartridge resistance, the greater the gain, so the PhonoCube will have higher amplification with the 8.2-ohm Delos than the 38-ohm 17D3. Note that the Delos also has two times the output level of the 17D3, so altogether the PhonoCube will produce significantly higher listening levels with the Delos than the 17D3.

2. The phono amp's signal input is the summing node of the feedback system, and this feedback reduces the input impedance to effectively 0 ohms (except for ultra-high frequencies, where there may not be enough gain to sustain feedback). As a result, the PhonoCube's circuit presents a heavier-than-normal load for the phono cartridge, and this increased level of electrical damping may result in a somewhat different sound than what you'd get with the same cartridge if it were paired with a normal voltage-mode circuit (with higher input impedance).

3. This type of circuit inverts phase, so it may be worthwhile to try swapping the plus and minus leads that connect the cartridge to the tonearm/headshell.

cheers, jonathan

What is the significance of the output voltage level of a give cartridge with regard to audio fidelity? For example, the Lyra Delos cartridge puts out 0.6mV. Some MC cartridges that I have seen put out less than half that voltage level. The apparent benefit would seem to be that the higher output level needs less gain in the phono stage, which likely means higher S/N ratios as opposed to lower output MC cartridges where you would need more gain in the phono stage. I guess my question is, are there disadvantages of the higher output voltage level relative to cartridges that output lower voltage levels?

I appreciate that the ultimate determination of whether one cartridge sounds better than another can only be determined by listening (which has it's own limitations because it can often be difficult to due an apples-to-apples comparison under the same conditions), but I am trying to get a sense as to what is the consideration in determining what output voltage a given cartridge will be designed to produce.

On a related topic, I read the instructions that come with the Lyra Delos that specify suggested load impedance values for use at the phono stage. My question is how did you determine those impedance ranges? By SPICE analysis, or some other method?

Jonathan,
Thanks for your thoughts and input. I received my Delos the other day and installed it on my RB300 last night.
All I can say so far is, wow, great job!
Very dynamic and balanced, much more than previous cartridges such as the Argo (which I did like, but found could be a little strident at times).
I am really looking forward to the next 50 hours or so.
Byron

Paperw8, before we speak of output levels, we need to distinguish what kind of core the coils are wound onto. Assuming the same level of magnetic field strength (flux), non-permeable cores are more inefficient at converting the physical movement of the stylus into electrical output, but what output they produce is quite linear. Permeable cores still aren't what I'd call efficient, nonetheless they result in much higher output for a given amount of stylus movement, but the permeable core adds noise, distortion and reduces resolution.

OTOH, distortion in a cartridge is caused by physical issues (such as tracking resolution) as well as magnetic, and the better the physical aspects (styli with longer and narrower contact patch, more linear dampers, less body resonances, more complete energy evacuation from the cartridge structure), the more noticeable magnetic and core issues will be. The reverse is also true, if the stylus is conical (spherical) and the damper is a simple one-way design, distortion due to magnetic and core issues will be swamped and therefore much less noticeable.

The next thing that needs to be stated is that distortion or noise in analog playback is caused not only by the cartridge, but also the phono stage and signal cabling. Tonearms likewise cause tracking and energy evacuation distortions, but we will leave them outside of the current discussion (as things would get too complex). In particular, the contribution of the phono stage is not small. Areas that phono stages struggle with include noise and gain (if noise and gain are insufficient, the designer may need to add one complete gain stage or an input transformer), and immunity to high-frequency energy (which are triggered frequently, by ticks and pops, mistracking, electrical loading, and RF issues), which can cause inharmonic distortion, which is particularly nasty-sounding. If the phono stage has a lower level of performance, it is usually better to design the phono cartridge for higher output levels, even if it means so much coil inductance that the electrical phase is seriously messed up (the worst in this respect being MMs).

If the phono stage is state-of-the-art, the cartridge designer can afford to design a lower-impedance, low-inductance, low-output cartridge. The extreme case here would be a ribbon MC (single-turn coil), but to my knowledge, no phono stage has ever been built which could do justice to such a cartridge, which shows you how challenging the task can be.

As far as the cartridge is concerned, lower output is more ideal. Lower output means less metal in the coil windings (copper has a specific gravity of 8-9, which is greater than iron!) for lower moving mass and reduced tracking distortion. Lower output also means fewer coil winding layers, which enables the coils to be of cleaner shape and will improve crosstalk, phase response, and channel matching (cleaner-made coils also look much better).

The majority of cartridges these days have permeable-core coils (well-known exceptions being Benz Micro's ruby core, and the carbon cores used in some of Ortofon's designs). Compared to permeable-core cartridges with their core-induced distortions, air-core cartridges will need more coil windings to achieve similar output levels, and the extra copper may result in more moving mass than if a permeable core had been used, and the increased number of coil layers will impair the geometric shape of the coils. Comparisons between the two approaches tend not to be straightforward.

Feedback from Lyra's markets (we make only permeable-core cartridges) has been that to go below 0.5mV (5cm/sec) means that many phono stages will be less than happy. The user may hear problems like noise, grain, insufficient bass response, or in less problematic situations, they may simply not hear the improvement in resolution that the lower-output cartridge should be giving them.

As a cartridge manufacturer, our problem is that the user may not be happy with the sound, but in most cases they will blame it on the cartridge rather than the phono stage or that they have excessive electrical contact points in the signal cabling system (which seems to work OK with MMs, MIs and high-output MCs), but will impair the sound of low-output MCs. Since no manufacturer likes to hear that users are unhappy, we've shifted our cartridges away from where they were some years ago (0.22-25mV, single-layer coils) to our present level (0.5mV, double-layer coils, although the Dorian and Delos use three-layer coils to generate 0.6mV). We are willing to make single-layer coil versions of our cartridges upon customer requests (especially the lower-volume, more expensive models), and if the customer's phono stage is up to the task, our experience has been that everyone is happy.

Does this answer your question adequately? It's a complex topic, so please feel free to ask more questions if some things remain unclear.

cheers, jonathan

What arms have you guys installed this cart in ?
Will something is the 14g effective mass work like the Phantom ?
In terms of cart loading, how many ohms are you guys loading it with ?
thanks!!