Don, sorry for your challenges.
So the first list refers to the four gain settings of your phono stage and the overload margins for each one. The second set has an asterisk, but you don't provide the info attached to it.
At any rate the sensitivity is the amount of input signal from your cartridge needed to achieve a pre determined output signal. Usually 2 or 3 volts.
IMHO, the 1mV output of your cartridge is kind of a tweener. I would try both the 40db setting, and if noise, or diminished dynamics was an issue, I would move up to 64db, and pick whichever sounded better. You will do no damage by using either one, it is strictly the sound quality that you prefer that should guide your choice. Good luck!
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@viridian
Thank you for your quick reply!
I think the 40dB will seem quite anemic with my cartridge, but I’m hoping the 64dB will be just what it needs.
My concern is if the 1mV will overdrive the phono amp or not.
So with the 5.7mV maximum input, you feel that I will have plenty of dynamic headroom and I wouldn’t overdrive or clip the phono amp?
Do you have any idea how much headroom I would have with the 1mV going into the 64dB input? I remember that we should try to have at least 20+dB of overload margin.
I truly appreciate your help!
best wishes,
Don
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From the Benz Micro site:
"The ZH at .7mV, is ideal for tube phono stages in the 50-60dB gain range.'
https://benzmicro-northamerica.com/benz-micro-ruby/
Determining what sounds right to your ears won't damage anything.
64db choice isn't far out of suggested range.
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Don:
Agree with all the theory you are profering. And 20db overload is the accepted figure, more better, of course.
But if we can agree that both implementations are imperfect, we are left with what distortions you can best tolerate, the possibility of occasional overloading or the potential loss of dynamics and increased noise of the lower setting. Which has nothing to do with theory, and everything to do with listening.
Until you try both, IMHO, you will never know. Also realize that at the higher gain settings you may be operating the volume control of your preamp at the bottom of its range, out of it’s linear region.
But you will do no damage, since you have to listen to the rig, pick the setting that you like best. Many of us have to make compromises, and pick the distortions that are least intrusive to us every day.
BTW are you the same No Regrets on WBF, love your dog!
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@tablejockey Thank you for reminding me about the the Benz site stating the ZH was ideal for tube stages with 50-60dB of gain. I'm embarrassed to say that I had forgotten about that piece of information.
However, with that being said... each phonostage design can be different in how they deal with their overload margins.
I realize that using my .7mV@3.54 (equating to 1mV@ 5cm/sec) may be pushing the overload limits of some phono amps that are pushing 60-64dB of MC gain.
Therefore, I am trying to learn as much as I can about the parameters of some various phono stage before buying them. Sadly, if seems virtually impossible to demo anything in home now-a-days, even when buying new. Let alone if you want to entertain purchasing a used item.
I'm looking at costly pieces, and I'm trying not to take an unnecessary bath, so to speak if it doesn't mesh with my cartridge and system.
Thanks again,
Don
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@viridian Hello and thank you again for your reply!
I wish I could know how much overload margin I would have when using my .7mV@3.54cm/sec or 1.mV@5.0cm/sec cartridge into the 64dB MC input.
I've reached out to the distributor; they didn't give me any answers. Instead they pawned me off to a dealer; which sadly, still hasn't given me any answers.
Hence the reason I decided to implore the wisdom of my fellow forum friends here 
I totally agree... listening will be the only way to tell. However, I haven't been able to arrange an in-home trial as of yet. The piece is quite expensive and I don't want to step into this completely blind just to find out I made a huge mistake and then take a huge loss trying to sell it off.
You brought up a great point about how the higher the gain, the lower the voume control will be.
The nice thing about my line stage is that it is using a very high quality ladder stepped attenuator that only uses two resistors per step and the excellent sound quality has remained the same throughout it's range. I have used several different power amps with this line stage that had widely varying input sensitivities which required me to have the dual mono volume controls to be set very low on some amps to very high on other amps and the sound has been truly excellent. Also, when going thru the range of volume with any of my amps, the quality of the sound has been really great... only the volume seem to change. I wonder if it has to do with the design of the "ladder" vs using a "pot"?
Yes... good catch :) I am indeed, one and the same - No Regrets from WBF. Thank you so much for loving my dog!!!
Many thanks to both you and tablejockey again for trying to help me better understand these things.
Best wishes,
Don
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If you are contemplating a new Phone Stage, I can recommend the Sutherland Duo. There are other Sutherland options in various price ranges; given the impedance of the Benz ZH the "Loco" Sutherlands are probably not right. In reviews their phono stages are noted for having large headroom.
The Duo (and 20/20) offers five gain settings (40, 46, 52, 58, and 64 dB) and five loading options (100, 200, 475, 1k, and 47k ohms).
The 52dB or 58dB with 475 ohms would seem to be a good match.
Upscale Audio (e.g.) offers 60 day auditions.
I have the Duo, paired with the Koetsu Rosewood Platinum and am delighted with the sound.
Best wishes to you.
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I think you got most of the info you need already, but let's put it in context. An amp has a maximum output level it can provide. Think of it as an electrical volume. The larger the amplification factor -- (multiplies the input signal to get output, for example 1V input with 2X gain (amplification) means 2V output) -- the smaller the input must be so the output is not exceeded.
So this is stable of "gains" whcih is the amplification factor expressed in decibels. At various gains they provided the largest output voltage in mV it can handle. You cna look up your cartridge's output max and make sure it is lower (bro not too much or the volume will be low).
Phono amps are a tradeoff of gain, noise, and overload all the time. Drove me nuts until I got my few recipes.
To put real numbers on this, one listing is 40dB, which is 100X. The maximum input they list is 90mV (0.09V). We can then infer the overload output level is 0.09 X 100 = 9V.
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I agree with the other @retiredaudioguy…your preamp jumps from 40 to 64 dB while your cartridge’ sweet spot is in the middle. I have used Pro-Ject PhonoBox DS3B and it has a 55 dB setting. They make a TubeBox version as well.
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Thank you everyone for your help and recommendations!
@itsjustme
I appreciate you trying to put some numbers on this!
To take this another step further….
Im considering the Accuphase C-47 phono amp.
From their manual, it states the following information…
Input Sensitivity for 64dB of gain = 1.26mV for 2V output @ 50 Ohms
Maximum Input voltage for 64dB of gain = 5.7mV
Maximum Output Level .01% THD 20-20k hz = 8.0 V
I have read that you should strive to have at least 20dB of overload margin across the frequency range.
Are you able to estimate what the overload margin expressed in dB would be if my cartridge output is 1mV going into their 64dB MC input with the specifications they listed above?
Here is their link.
https://www.accuphase.com/cat/c-47_e.pdf
Thank you so much for trying to help me better understand!
Best wishes to you all,
Don
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Nice phono! Wouldn’t the maximum input voltage listed in the Accuphase lit be the point just below overload? Says 5.7mV at 64db gain. 20db above 1mV would be 10mV.
Perhaps the KAB cartridge calculator will be of help, there is also a general chart at the bottom showing the appropriate gain for a 1mV cartridge. You can also play around by changing any parameter and recalculating. Good luck.
https://www.kabusa.com/pregain.htm
To complicate things further, Bob's Devices makes a 1:5 SUT which would lift the nominal output to 5mV and allow you to go straight into the MM phono gain. Unfortunately for more money of course.
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Hi Don, Pretty busy so wont do the arithmetic but to help you along:
20dB margin = 10X margin.
64 dB of gain is 1500X
So calculate backwards
hope the is helpful
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@viridian
Thank you so much for sharing the link 👍
However, I don’t know if I am using it correctly.
If I plug in the following data:
1mV@5cm/sec
1.2mV of Sensitivity
64dB of gain
8 V rms Max Output
it seems to solve for:
50dB Otimum gain (but I could use higher if I need to, right?)
46dB of overload margin
5mV before overloading
Am I doing this correctly? I would actually have 46 dB of overload margin if using my 1mV into 64dB of gain in this phono amps? If, yes then that is far higher than the 20dB that is often recommended 👍
Somehow, I feel like I’m doing something wrong
Any thoughts?
Thanks much!
Don
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@viridian
As I relook at your previous reply, you mention that …
Overload is 5.7mV@64dB of gain
20dB above 1mV=10mV
So, does that mean I’d only have around 10dB or less of overload margin?
if yes, then that would mean I would probably clipping the phono amp quite often, right?
Im very sorry that my brain is having trouble trying to comprehend this.
Any thoughts?
I really appreciate everyone’s help 😊
Best wishes,
Don
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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.
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@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
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"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.
..........................
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@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
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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.
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With that spec showing overload occurs at 5.7mV output from the cartridge when the phono is set for 64db gain, and given that the cartridge has a nominal output of 1mV, then for a hypothetical 20db of overhead margin, you would like to see at least 10mV before overload. 5.7mV is about 15db of margin above the nominal 1mV of output. "db" are in log scale so half the voltage is not half the db. As others have mentioned, 64db is probably more gain than you need, but the next lower gain you can select, if it is 40db, is too little gain. You are better off with 64db, IMO. As for the rest of it, just listen. If you hear distortion on loud passages, maybe the cause is phono overload but maybe not, as distortion on loud passages can have many other causes as well.
In general, the overload margin of a phono stage is inversely proportional to its gain; the higher the gain, the lower the overload margin, but since you use high gain with cartridges that have a very low output to begin with, overload is less likely to be an issue. Also, in general, tube phono stages tend to have a higher overload tolerance than SS ones.
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As part of this, can others who have solved HUM from SUTs please let us know what worked.
Thanks ahead of time
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@lewm
Thank you for your reply!
At least I feel a little better now knowing that the overload margin will be 15dB with my 1mV cartridge going into the 64 dB gain setting of the Accuphase C-47 vs the roughly 10dB overload that I was fearful it might have been.
I totally agree that some distortions with vinyl playback can come from other sources than just phono amp overloads. Such as, groove wear, pressing qualities, recorded to hot, etc.
I just didn’t want to risk paying out a huge cash outlay just to find out that the Accuphase C-47 wasn’t a good match for my 1mV cartridge, especially considering that this is a solid state design vs the all vacuum tube design of my current phono amp.
So, do you think the 15dB of overload margin will be fine with my cartridge and the 64dB gain of the Accuphase?
I truly appreciate yours and everyone’s help!
Best wishes,
Don
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Yes I think so, but you’ll be the judge based on listening.
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