Audio Research PH5 Phono Preamplifier Input Clipping Problem
Yes, I purchased my VTPH-2 new, directly from Keith after speaking with him on the phone. You would want to confirm with him that the lower gain version is the optimal choice for use with a 0.27 mv cartridge. I suspect that it will be, though, in part because he recommended that version for use with a 0.3 mv cartridge I was considering at the time. I ended up going with an Audio Technica AT-ART9, though, which is rated at 0.5 mv. Best regards, -- Al |
This has two gain settings. Take a look, it just might fit the bill ! https://www.youtube.com/watch?v=RfpJYJv3ddo |
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 |
