Phono Amp Spec’s

I don’t think you can use the kAB calculator to determine the overload margins as this is specific to your phono pre. However, if I plug in your specific figures it yields an optimal gain of 50 db, and if you go to the chart at the very bottom, this is confirmed as optimal gain is specified as 43db minimum, and 53db maximum. And realize, if your phono pre is putting out 8V as suggested, you may be overdriveing your preamp or overloading the phono preamp. And yes, I think your math’s are correct and you would only have 10db of headroom before overload.

Rather than skiing uphill, and trying to make something work that inherently doesn’t, the best options might be to buy a phono pre with the correct gain settings for that cartridge, replace the cartridge with low output at the same time as buying the Accuphase, or using a 1:5 SUT with your current cartridge and running it into the MM setting of the Accuphase.

@viridian Thank you again for your reply.  Believe me, it is very much appreciated!

I understand that the KAB is suggesting the optimal gain for my cartridge is from 43 to 53dB.

However, as @tablejockey had correctly posted above... the Benz website says my cartridge is ideally suited for tube phono amps that have 50-60dB of gain.

I have used my cartridge with phono amps that had 40dB, 52-54dB and 60 - 62dB.  I have found that "in my system" the cartridge really comes alive and is full bodied with at least 60dB of gain and it works beautifully with my current 62dB all tubed phono amp.

Based on these experiences, I was hoping 64dB would be close enough and still work well, but obviously I am concerned about the overload margins with this new phono amp.

I was really hoping to avoid the use of step up transformers, because oftentimes you may have to deal with hum - due to placement, etc.

I do have an extremely nice vintage Hirata Tango step up transformer that offers 1:6.6 ratio.  There are times when I get no hum and then other times when I do... it can be frustrating at times.... but when there is no hum - it's simply stunning!

Anyhow, I'm at a point in my life, with all of my health issues, etc I don't want anymore stress.  So, I guess that is why I'm trying to avoid using my SUT if at all possible.

Best wishes,

Don

"I do have an extremely nice vintage Hirata Tango step up transformer that offers 1:6.6 ratio.  There are times when I get no hum and then other times when I do... it can be frustrating at times.... but when there is no hum - it’s simply stunning!"

That means the sound of your MM Phono is stunning. That is why I use a SUT, to keep using my beloved McIntosh tube preamp mx110z's MM Phono EQ.

You simply MUST find a hum free location for the SUT, put it inside an isolation box  ,,,,, different length or type of cables ..... Don’t walk away from ’stunning’.

Your cartridge's impedance is 38 ohms, they say it should see around a 400 ohm load (that fits the formula 38 x 10 = 380 ohms).

That cartridge: you might need a unit that provides separate control of gain and impedance. My Fidelity Research FRT-4 SUT (gain and impedance are a 'resultant' relationship) to 'get' 470 ohm load, it would be x factor of 10.55 which may be too much signal.

..........................

@elliottbnewcombjr 

Hello and thank you for your message!

When you say an isolation box.... what materials should it made of?  

Is this something that I would build, or is this something that you purchase?

I do love the Hirata Tango transformer... when it doesn't cause any hum, that is.

Best wishes,

Don

2db's over the stated "optimal" range is likely negligible.

You'll maybe experience a click or two more sensitivity on the volume knob?  

I wouldn't stress over it.