CONUNDRUM

The ARC phono stage with your cartridge is outputting 2.7 volts to the line stage. This is more than enough to drive your amps w/o the linestage. Adding the gain of the linestage, you now have a whopping 38 volts of output to drive the amps at full tilt. You need to either change out the cartridge to match the phono stage or change the phono stage the match the cartridge. I wouldn't mess around trying to mod the phono stage - who knows how that will sound.

Two suggestions. Clearaudio has a reasonable trade up program. Look for a model that has output less than 1.0mv. That should take care of the problem. On the other side of the coin, I would consider looking at a Aesthetix Rhea. It will work well woth your line stage and you get variable gain with the ability to voice it as you like by tube selection.

The input impedance of the Calypso is 20kohm if unbalanced, 40kohm if balanced.

The output impedance of the PH-7 is 200 ohms unbalanced. According to ARC, the output load should be a minimum of 10kohm, so let's assume that value as the total load, and estimate the values of some resistor networks that could be built into the interconnect between the PH-7 and Aesthetix.

If you want to reduce the PH-7's output to half (-6dB), you would need two 4.99kohm resistors per signal polarity. One resistor pair if you use the unbalanced outputs from the PH-7, two resistor pairs if you use the balanced outputs.

One of the 4.99k resistors should be soldered in series with the "hot" signal wire of the interconnect cable, the other resistor is soldered from the output side of the first 4.99kohm resistor to ground (outer shell of the RCA connector).

However, we must keep in mind that the Calypso already has a 20kohm input resistor, so for the second resistor (from output to ground), we want a value that forms 4.99kohm when placed in parallel with the Calypso's 20kohm resistor.

One such value for the second resistor would be 6.8kohm, which in parallel with 20kohm, will form 5075 ohms, which is a +1.7% error.

Another possible value for the second resistor would be 6.65kohm, which in parallel with 20kohm, forms 4.991kohm, for an error of +0.01%.

In either case, the first resistor remains 4.99kohm.

For a reduction to one-quarter (-12dB), the series resistor should be 7.5kohm and the ground-side resistance should be 2.49kohm.

Again, since the Calypso already has 20kohm at its inputs, we want a value for the second resistor that forms 2.49kohm when placed in parallel with the Calypso's 20kohm resistor.

One possible value is 2.7kohm, which in parallel with 20kohm, forms 2.379kohm, which is an error of -4.46%.

A more suitable value would be 2.87kohm, which in parallel with 20kohm, forms 2.51kohm, which is an error of +0.8%.

If your ears suggest that the total 10kohm load is too heavy for the PH-7 (slightly muted dynamics, slight loss in resolution), generally you would double all of the resistance values. 10kohm becomes 20kohm, 4.99kohm becomes 10 kohms, 7.5kohm becomes 15kohms, 2.49kohm becomes 5kohm. But all of the second resistors will need to be re-calculated, I suggest that you try the 10kohm setting first, and if that isn't to your liking, let us know and I or someone else will do the math for 20kohm instead.

Please keep in mind that the lower resistance, the lower the noise, so I would not increase the resistor values unless I thought that the sound lacked life.

Theoretically, the resistor network could be placed either at the output of the PH-7, or the input of the Calypso, but if you place it at the output of the PH-7, you will get a roll-off in the high frequencies, due to the capacitance of the interconnect. Better to place the resistor network at the input of the Calypso.

I believe that the above will be the easiest and most economical solution to your troubles.

kind regards, jonathan carr

FWIW, the Rothwell Attenuators, and I would imagine most other comparable devices, are configured in the same manner as what Jonathan has described, with a series resistor, and with a shunt resistor at their output. I have a pair of the Rothwell's, and as measured with my not particularly accurate analog multimeter the series resistor has a value of about 21K, and the shunt resistor has a value of about 9.5K. In conjunction with the Calypso's 20K unbalanced input impedance (the PH-7 does not provide balanced outputs), that will result in an attenuation of about 12.6db. The load impedance seen by the PH-7 with the attenuators in place would be a presumably comfortable 27.4K. The attenuators are intended to be placed directly at the input connectors of the destination device (the Calypso in this case), so cable capacitance would not be an issue.

Handymann, while I'm not sure that 12.6db will be a sufficient amount of attenuation (given that the cartridge will probably exceed its 3.6mv nominal output by a considerable amount on the peaks of some material), I repeat my earlier comment that I'm surprised that you reported significant sonic degradation using an attenuator. Can you indicate what model attenuator you used, how much attenuation it provided, and exactly where in the system it was connected?

Regards,
-- Al

I tried both GOLDENJACKS and ROTHWELL attentutors. Both do the job they have been assigned, however I did notice a slight difference in the clarity of the sound. Having spent money to achieve more clarity, this was obviously not a viable solution. For some systems they might be just the thing and are for sale if anyone wants them.
Both the Aesthetix as well as the PH-7 are excellent pieces of equipment and sound VERY good separately as I'm sure they will together with a lower output cart. I didn't consider possibly needing a variable output on the 7, or a variable input on the Calypso-but should have. I really appreciate all the responses and various suggestions to help remedy my problem. A lower output cart is on it's way.
Soon, the Calypso and the 7 should be working well together.

Handymann,

The real issue is one you highlighted, that your turntable is way below the level of your phono stage and preamp. Therefore a good low output moving coil will potentially be too good for the arm and sound awful. My suggestion would be to find a lower output cartridge of medium to high compliance for the budget arm on your deck. My suggestion would be to look at the Grado MI cartridges as they have Moving Iron cartridges with 0.5mv output in both the Reference and Statement Series from about $350. The other recommendation would be the cheaper Benz MC's with low output as they are medium compliance.