Audio Research PH5 Phono Preamplifier Input Clipping Problem


I have an ARC PH5 phono preamplifier and most of the time it sounds fine.  But on a few of my favorite LP's with wide dynamic range, it will clip and distort on loud sections, especially those with lots of bass content.  This only happens with use of a step-up transformer, without the SUT in line, there is no clipping. I do prefer to use the SUT, as without it I have to turn the volume setting on my ARC REF 3 preamp to a very high level.   I have to conclude that the PH5 is distorting because of high input signal levels, due to the gain of the SUT.   I have tried two SUT's, one with 13:1 and the other at 7:1, both exhibit the same problem (although the lower gain SUT is much better).  The cartridge is Ortofon A90 with .27 mv output.  Given this, would you expect clipping or do you think there is something wrong with the PH5?  I have talked to ARC about this issue, and they seem to think that there is a chance the PH5's maximum input of 70 mv is being reached on these loud sections.  Would appreciate opinions from those that have experience with a similar setup.  Thanks.
Ag insider logo xs@2xscottwsmith
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?
In many designs low settings of the volume control may result in an inability to adjust volume in fine enough increments. I see that your REF3, however, provides 104 steps of volume adjustment, so I suspect that is not an issue in your case.

Also, in some designs channel imbalances can occur at low settings of the volume control. But again I would suspect that is not an issue with the REF3.

Finally, it is conceivable that in some designs having to operate the volume control at low settings may result in whatever sonic side-effects may be introduced by the volume control mechanism itself being worse than at higher settings. I have no knowledge, though, as to whether or not that possibility may have any applicability to the REF3. And even if it does, it would be anyone’s guess as to whether or not the possible sonic side-effects of an in-line attenuator, used with these particular components, would outweigh the possible benefit.

Best regards,
-- Al

almarg, I'd be interested in knowing if you have any favorites in the phono preamp category, care to comment?
Scott, yes, inspired by a great many overwhelmingly positive comments I've seen here and elsewhere, late last year I purchased a Herron VTPH-2 phono stage ($3650).  It is beautiful sounding, versatile, very intelligently engineered, absolutely quiet at any volume setting in my system in both LOMC and MM modes, and as many others have commented Keith Herron is a treasure to deal with.

It is offered in a choice of two gain configurations.  For the majority of applications, including mine, the lower gain version is preferable.  It provides gains of 43 db in MM mode and 64 db in MC mode.

The one slight caveat I would cite is that like your PH5 it does not provide balanced outputs, and John Atkinson's measurements of the REF3 indicate somewhat better measured performance in balanced mode than in unbalanced mode.  But even if those measured differences have any audible significance, which I doubt, I would suspect they are mainly attributable to JA having used the preamp's unbalanced outputs for the unbalanced measurements, not just the unbalanced inputs.  And I note the following statement in the body of the review:
ARC states that the long-tailed pair used in the Ref.3's input stage provides identical performance (save for the amount of gain) using either the balanced or the single-ended inputs.
Good luck.  Best regards,
-- Al
 
Yes I have noticed that one is recommended a lot.  Looks like a move from PH-5 to Herron could cost about $ 2K.  Will have to consider whether that is "reasonable" or not.  But for me, swapping gear and upgrading is part of the fun.  It seems that used versions of the Herron are hard to find.  I guess those who have them, keep them.  Did you purchase yours new?