Audio Research PH5 Phono Preamplifier Input Clipping Problem

Dear @scottwsmith : """   I know the SUT's historically have been used when you have a phono preamp which is designed for MM cartridges only. """

With all respect that statement is a misunderstood. In the old times active high gain phono stages designs were almost non-existent and almost all the phonolinepreamps were designed for LOMC cartridges using SUTs internally and the external SUT option were used with Phonolinepreamps or phono stages with no internal SUT.

A well designed today SS active high gain phono stage or phonolinepreamp performs with a higher quality that a phono stage with external SUT.

Normally all SUTs has " problems " at both frequencies range extremes. Has inherent limitations at low bass and high frequency against a well designed SS active high gain phono stage. 

Regards and enjoy the music,
R.

It seems to me that the ARC PH-5 is less flexible than some other phono stages, because it has fixed gain.  This might be more of an issue if the cartridge is MM has high output.  For example, if the cartridge's output is 4 mv, almarg's math gives me:

4 mv x 750 = 3 volts.

Only a 3X factor for headroom during loud passages, seems likely the 10 volt limit of the REF 3 would be reached often, and hello clipping!  Is my logic faulty, or this combination of components just a bad idea for MM cartridges with higher output?

So a PH-5 and REF 3 are really only good for LOMC?  Yipes. 

Yes, under most circumstances 57.5 db is considerably too much phono stage gain for use with a MM or other high output cartridge. Typically MM phono stages provide gain that is in the area of 40 db or so.

In addition to the possibility of clipping, another downside that can occur in many applications would be having to operate the volume control undesirably close to the bottom of its range. As you may have seen in other threads it is not uncommon for that problem to occur with digital sources having **maximum** outputs in the area of 2 volts.

That much gain would often be suitable, though, for use with MM cartridges in systems employing passive preamps, to cite one example.

In your particular case, given the very high overload margin of the phono stage itself a means of utilizing a high output cartridge without overloading the preamp would be to insert a Rothwell in-line attenuator, or something similar, between the two components. Although reports I have seen over the years on the sonic effects of those devices have been mixed, with some (including me) having found them to be quite transparent, and others reporting significant adverse effects on dynamics or other sonic characteristics.

Rothwell attenuators are available in both balanced and unbalanced configurations, and in 10 db, 15 db, and 20 db versions. I believe that most and probably all of those versions would be suitable with respect to ARC’s loading recommendations for the outputs of your phono stage (quoted below from www.arcdb.ws), and certainly with respect to the 10K minimum requirement. But I know that some similar devices from other manufacturers would not meet that requirement.

ARC PH5: Recommended load 50K-100K ohms and 100pF. (10K ohms minimum and 2000pF maximum.)

Regards,
-- Al

I am learning some good stuff here.  Switching gears a little, I also have an ARC DAC7 (which I use in balanced mode) with these analog specs:

OUTPUTS, ANALOG: (Stereo)1. Balanced XLR 5.2V RMS (+14.3dBv) max.2. Single-Ended RCA 2.6V RMS (+8.3dBv) max

And yes, I do operate the REF3 at rather low volumes (maybe 20%) when using the DAC.  Is there any possible benefit in using an attenuator?