Audio Research PH5 Phono Preamplifier Input Clipping Problem

I have had no luck with using a SUT with the ARC-5.  The gain of 57.5 is difficult to work with.  Almarg is correct.  However, if you look at the signal to noise ratios of active MC/MM phono stages, you will find that the signal to noise ratio using MM is higher than the signal to noise ratio using MC.  Additionally, increased distortion results from using the MC active stage.  That is why many manufacturers using SUTs in their phono preamps to accomodate MC cartridges.  The challenge is making different gain adjustments to accomodate different cartridges. ARC makes this easy by only offering one option and designing the phono preamp for only one gain setting.  It is great for a cartridge of about .5-.6 mV, but lower output cartridges don't work as well.

In the ARC world, you can move to the Reference product line, which does offer different gain levels, but they are pricey, I don't think I am too interested in that solution.   For those phono preamps that really do have an MM/MC switch -- I think you are saying using the MM setting with an SUT, instead of the MC setting might yield better results for a MC cartridge with output in the .25 range, such as mine.

For example, on the Manley Chinook, there is an internal setting to set the gain at around 45 dB, " for MM cartridges".  With my SUT's of 1:13 and 1:7 and that gain setting, what would be the input levels to the REF3, and given your suggestion of possible lower noise and distortion, is this a good upgrade?  Same set of questions for the Herron, if you would indulge me?? 

Hi Scott,

In the specific case of the Herron I would not expect using a SUT into its MM input to be preferable to going directly into its MC input. I say that in part because of the great results many have obtained using LOMC’s directly into the VTPH-2; in part because as I had mentioned I have found the VTPH-2 to be absolutely quiet at any volume setting (even when using my Stax electrostatic headphones, with the volume control at max); and in part because using a SUT into a 47K MM input will result in the cartridge seeing a much heavier load (i.e., a **much** lower number of ohms) than seems to usually be necessary with the Herron. (Keith recommends that with the VTPH-2 it is often preferable to apply no loading at all, with the input impedance of its LOMC input being almost infinite. And as Atmasphere and others have pointed out in past threads here, optimal loading of an LOMC is primarily dependent on the design of the phono stage, not on the cartridge).

To answer your question about gain, based on the relation db = 20 x logarithm(Vout/Vin) it can be calculated that for a 45 db gain setting of the Chinook the corresponding voltage multiplication is 178x, and the 43 db MM gain of the Herron corresponds to a voltage multiplication of 141x.

0.27 mv x 7 x 141 = 266 mv
0.27 mv x 13 x 141 = 495 mv

0.27 mv x 7 x 178 = 336 mv
0.27 mv x 13 x 178 = 625 mv

All of those alternatives would provide the 10x headroom factor Bob recommended, relative to the max input spec of the REF3.

Regards,
-- Al

Dear @bobsdevices  :   """  That is why many manufacturers using SUTs in their phono preamps to accomodate MC cartridges. """

Not really and not exactly as you posted. Yes, S/N is higher in MC active high gain devices than the same S/N figure in MM mode but this is just a number and if we know " to read " those numbers then it does not matters and does not goes against a SS active high gain designs.

The phono stages/phonolinepreamps that needs and use SUTs are the all tube designs because tubes are " noisy ".

AR, Herron and other tube designers instead of SUTs use SS devices at the input gain stage trying to lower noise and distortion levels.

The other designers that use SUTs are not because SUTs are better than SS active high gain designs ( that are not. ) but because is a lot more easy to design that " elussive " active high gain knowledge levels to do it.

A good SS active high gain design always beats to a design using SUTs.

What makes the real differences?: knowledge and skills level of the designers, nothing else.

In the other side here are 3 precise examples ( there are many more. Name of the game is in the design and implementation of that design. ) of SS active high gain designs where you can't detect that difference in S/N ratio between MC stage and MM one or even if the phono stage does not handle MM cartridges the S/N is so low in the MC stage that's imposible to detect any sign of noise or distortion levels:

http://www.stereophile.com/content/bmc-phono-mcci-phono-preamplifier-specifications#TWPUCjhcM5muLLb2...

http://www.stereophile.com/content/liberty-audio-b2b-1-phono-preamplifier#zP3dCRyDuo1Zyzoi.97

http://www.stereophile.com/content/parasound-halo-jc-3-phono-preamplifier-measurements#sEEGXPqsWEtwr...

As I said there are many other SS designs that are less affordable $$$  for almost any one.


Regards and enjoy the music,
R.

Dear @scottwsmith : I owned the A-90 that's one of the finest ( still ) today cartridge performers and I can tell you that for the cartridge can shows at its best  it needs a very good matching tonearm and the finest phono stage/phonolinepreamp we can get and with all respect your PH5 can't do it.

The gentlemans that posted in your thread are not a little " concerned " on the  A-90 cartridge needs and IMHO this must be the first " parameter/premise " to judge what to do.

Regards and enjoy the music,
R.