CONUNDRUM

Your in a world of hurt.

How did you come to the conclusion that in-line attenuators degraded the sound quality? How did you perform a level matched comparison?

From your original post the phrase that jumped out at me is "in my haste". Has it even been 30 days since you got the new preamp and phono preamp? And now you want to change cartridges and/or one of the preamps. My suggestion is to slow down and carefully consider your options.

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.

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.

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

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

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.

I'm not 100% sure this will help, but here are a couple of things to consider:

From the Calypso manual : Note: The input circuitry of the Calypso accepts a maximum input voltage of 3.5v rms single-ended or 7v rms balanced. This is well above the industry standard 2v rms single- ended or 4v rms balanced. However, there are a few source components that exceed this limit. If the offending source component has a volume or gain control, all that is necessary is to reduce the gain or volume of the source component. In other cases, it will be necessary to have the source component modified to be within industry standard specifications. A clear indication that this limit is being exceeded is a raspy distortion or compression of musical peaks.

From another Audiogoner, on changing the gain of the Calypso:

To change the gain on the Calypso, turn power off for 20 mins, remove top, and locate jumper block for each channel. To find this, locate V2 tube (the left hand one), move right past a block of four resistors, and you should find the jumper block (just to left of two yellow capacitors). The jumper block has four positions, and if the Calypso is on high gain, there should be a shunt in the upper one and the lower one, with two empty positions in between. To change to low gain, move both shunts from the outside to the inside positions. Then repeat for the other channel.

Note: older versions (at least of the Janus) did not have this jumper block in which case obviously you can't adjust the gain. If in any doubt, email glenn@aesthetix.net and he can send you detailed instructions/diagrams,

Elevick, the PH-7, if modified by ARC, has 6 tubes: (4) 6922 tubes in the gain circuit; and (1) 6H30 tube and (1) 5881 tube in the PS. I don't think your idea has legs.

Handymann, the Koetsu is a very expensive cartridge, most models are in excess of $4K. Not sure, but there appears to be several Urushi models. Based on a very high-level check on the Needle Doctor web site, it appears the output voltages range between .2mV and .6mV. This class of cartridge appears to have a low compliance factor of 5.

Clearly, the Koetsu generates much less voltage than the Maestro. Therefore the PH-7's output should be less too.

If you want to try a LOMC, perhaps it would be prudent to try a cheap LOMC and see how it works. As I mentioned above, the PH-7 has a noise rating of 70db. It would be very unfortunate if the PH-7's output put out alot of noise with low output carty. I reiterate, it's worth a 15 min call to Calvin at ARC. He's in the best position to advise you.

If you take Mr. Carr's advice then you have to buy a Lyra ;)

I think I may go with a Koetsu Urushi MC cart. Any comments?

For fun, do you have any 12au7's around? The PH-7 uses 12ax7's, correct? Try the lower gain tube? If not 12ax7's, which tube does it use?

Second Swampwalker and Jcarr, but I would still ask ARC and Tom, FWIW.

TD is most likely correct, but if ARC says no, then I would go w Jcarr's advice. He designs some of the best carts out there and is a frequent and generous contributor to these forums. Just make sure you use good quality resistors. But I am pretty sure you will find that you can change the resistance internally to the phono stage.

I am confident Stringreen is correct in that if you call ARC, there would be an option to replace two or four fixed resistors that would change the gain by at least 12 db (I don't know if that would be enough but its a fair amount) if not more. Thats a job I would do myself and any tech could do in minnutes. I would hope that there could be 18 to 24 db of reduction with no problem.

Keep the old resistors and it can be easily restored. And it would be cheap to do.
TD

Handyman...I don't believe you are correct when assuming that the output can not be reduced without sacrifice. Call Audio Research, and I am quite positive that by substituting a resistor, (an easy procedure...but you need the right kind and value and position in the circuit which Audio Research will provide) your system will sing.

Al, I got us off topic, but I'll close the "capacitance" loop fast. Thanks for the info on the Zephyr. To my untrained journeyman ears, the Zephyr souns great, cables and all. I thought the Maestro did too. Something to be said for ignorance -- if I feel happy, then I guess I am. :)

I agree that the primary problem is line stage clipping. Al, do you agree with my suggestions above, particularly those relating to calling Tom Tutay and ARC???

Hi Bruce,

I wouldn't expect load capacitance to be relevant to issues at bass or subsonic frequencies.

Yes, the Maestro isn't optimally loaded by the capacitance of the PH-7 + cabling, but I have no way of knowing how significant the resulting sonic effects may be with that particular cartridge. And of course it is an issue that is separate from the overloading problem.

With respect to the Zephyr, Mr. Ledermann does provide a load capacitance recommendation, 100 to 200 pf. See page 2 of this datasheet. Again, I don't know how critical that may be.

Best regards,
-- Al

Thanks Al. BTW you may have picked up on something about the Maestro that that I d/n focus on when I fiddled with it on my VPI Classic. As I reported in many posts to the point of ad nauseum, I had a bass ringing/resonance that Mike at VPI and I could not fix. At the time, Mike and I focused on optimizing the set up to manage the tone arm/carty resonance from a mechanical perspective.

In retrospect, I question outloud now whether there might have been a mismatch with the PH-7 by reason of capcaitance: Maestro - recommended 100pF vs. PH-7 - 200pF (not even including I/Cs of another 100pF).

I think this point is relevant to the OP because he has the same front end as I did. Any thoughts??

As an aside, I currently use a SS VPI Zephyr, a MI carty. I checked the SS web site. FWIW, nothing mentioned about capacitance that I could find????? Oh, the Zephyr sounds great to my shriveled ears.

Bruce (Bifwynne), good points about load capacitance. I don't recall offhand the particular discussion you are referring to, but let me clarify a little further.

For cartridges having high inductance, such as most MM's, the load capacitance seen by the cartridge will directly affect tonality in the upper part of the audible spectrum. Too much or too little capacitance for the particular cartridge will adversely affect frequency response flatness. 100pf is recommended by the manufacturer for the OP's Maestro.

For cartridges having low inductance, such as most LOMC's, load capacitance will have insignificant direct effects on the cartridge's behavior at audible frequencies. However, high capacitance will lower the frequency and increase the amplitude of the ultrasonic resonant peak which results from its interaction with cartridge inductance. That in turn can result in the phono stage being required to process excess ultrasonic energy that it may not be able to handle gracefully. In general, therefore, the lower the capacitance the better, for LOMC's.

For HOMC's, such as the Dynavector you referred to, my suspicion is that the second of those two effects will generally be the most significant. But I don't have a precise feel for that, as inductance specs for that cartridge (and most others, for that matter) don't seem to be available. Perhaps Jonathan will comment further, with respect to HOMC's.

Handymann, I'm surprised that the attenuators you tried had such adverse effects. What model did you use, how much attenuation did it provide, and where in the signal path did you place it?

Best regards,
-- Al

Spencer, As I have already mentioned 3 times, I own the PH-7 and owned at one time the Maestro. By itself, the PH-7 has no problem with the Maestro. The real problem here is that the PH-7 is overloading the line stage and the PH-7 does not provide for gain attenuation.

IMHO, the real solution and the best solution is that the PH-7 -- which btw is a very very good phono stage -- would do a great job with pretty much any carty (except those with outputs less than .5mV) IF the PH-7 was matched with an ARC line stage. The synergy is perfect, as would be expected.

I will not repeat the advice I gave above, other than to say that I would ditch the PH-7 and/or the Maestro as a last resort, of course taking cost/benefit into account. This is a practical problem that demands a practical solution.

One last point. Almarg mentioned in another OP that capacitance may be an important and possibly choice limiting factor when selecting MC carties. As I recall, MC carties are sensitive to aggregate capacitance of the phono stage and I/Cs between the TT and phono stage.

The ARCDB web site reports that the input capacitance of the PH-7 is 200 pF. That may be the upper limit of some MC carties. If so, very low capacitance and short I/Cs would be called for.

I had this problem when using a DV 20Xs H carty. I was using long (12') cheapo Radio Shack I/Cs. The DV didn't sound very good -- almost listless and dull. I bought a shorter pair of custom I/Cs from Tom Tutay (16pF/ft) and the TT/carty combo was much improved after break-in.

I reiterate for the last time that a converation with Tom Tutay may be worthwhile. A call to Calvin at ARC may also be warranted.

Good luck. If Almarg catches this thread, perhaps he can weigh in with better advice.

Handyman,

It's a shame you ended up with a mismatched cart and phono stage, but that certainly sounds like the problem. Adding a transformer is a terrible idea IMHO, and clearly avoids the root cause.

If the PH7 is designed for LOMC cart, then get one or sell the phono stage and get something with more flexibility. When evaluating carts, you need to consider the combo of the cart & phono stage for gain; you also need to consider the combo of arm/cart for compliance compatibility.

By reading about what carts PH7 owners use, you will probably be able to quickly get a sense of what output range to consider. Then you can use online interactive chart(vinylengine? somebody help me here, please) to evaluate compliance compatibility for various arm masses vs. carts. Now you will have a list of viable candidates, and you can narrow it down by price and the sonic attributes for each model vs. your goals/preferences.

Perhaps ph7 owners can chime in...cheers,
Spencer

Handymann: In the event of signal overload, I sometimes use interconnect cables that have a built-in two-resistor network that attenuate the signal by a fixed amount. Since only two resistors are used (one series, one shunt), and the attenuator is built into the RCA connector plug right before the line stage input, there isn't much degradation in sound.

You need to determine by how many decibels you need to attenuate the signal from the PH-7, figure out (or ask someone) a resistor network pair that attenuates the signal by the desired amount without stressing the PH-7, then build (or have someone build) that resistor pair into the RCA connector of a decent-quality interconnect cable.

Since the modification will be to the interconnect and not to the phono stage or line preamp, the work should be fairly simple, and won't affect the resale value of the ARC or Aesthetix.

hth, jonathan carr

Addendum: Tom Tutay is very solid. I used him to build a very custom impedance buffer that summed L/R channels and corrected an asymetrical loading problem. That's about as "custom" as it gets. I reiterate my suggestion to call him. Perhaps other folks who know Tom could weigh in with approbations.

Handymann, I think I already responded to another OP that you started about this issue. As previously mentioned, I own an ARC PH-7 and Ref 5. Jfrech's advice is ok, but the PH-7's gain output cannot be adjusted. There are no switches or knobs to do this. As I see it, your "obvious" choices are simple if you are clipping your pre: change the pre, change your phono stage,or change the cartridge.

At one time, I also owned the Maestro. It's may very well be the best MM cartridge on the market today. I'm sure you are not excited to lose it, but a carty is less expensive than a pre or phono stage.

I have two suggestions that you may want to explore for viability. I've never gone down this road, but it be may worth asking. Call Tom Tutay at Transition Audio Design in Florida and ask if he can rig: (1) some type of an attenuator to cool down the PH-7's gain without degradation of the signal to the pre; and/or (2) a SDT (step-down tranny) to reduce the output signal of the Maestro that is fed into the PH-7.

FWIW

I have a rather low end table-Clearaudio Emotion with stock arm. I heard the Concerto cart is good @ reproduction, while not emphasizing surface noise. I really need suggestions on the cartridge. You say the Koetsu?

That Maestro Cartridge has a 3.6 mv output. Do you have your PH7 set to the MM or low gain setting?

You have a great phono stage and preamp. I'd try and get a moving coli in the .5mv-1mv range. What about a Lyra Delos? Big step up in sound quality I suspect, it's not warm cartridge but it has warmth in a balanced way. Won't break the bank to much either.

You can also step up i the clearaudio line...to their moving coils. If you really want warm I'd try a koetsu. Just depends on your price what model.

What arm and table? Need to match here to.