Rethinking Phono Preamp Gain Settings

Discussion in 'Audio Hardware' started by avanti1960, Jul 8, 2017.

  1. Bob_in_OKC

    Bob_in_OKC Forum Resident

    Location:
    Dallas, Texas
    These aren't abnormal numbers, although they might occasionally prompt someone to search the forums for why their turntable isn't as loud as their CD player. 1.2 to 1.5 V is higher than I've ever noticed being discussed. As an example, the Rega Brio input sensitivity is listed as 210 mV. The most common output level I've seen is probably the usual 3 to 5 mV MM cartridge into 40 dB gain. That's 300 to 500 mV output from the phono stage.
     
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  2. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    OK, that just answered another question I didn't even ask - the approximate input sensitivity of my Cambridge Azur 851A integrated (which they don't publish). I have a 2M Blue (5 mV) going into 40 dB phono, then into the Cambidge. Which tells me that the Cambridge has at least 500 mV sensitivity, but hopefully even below.
     
  3. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    Would you mind sharing the formula you use to calculate phono's output, given cartridge output and phono's gain?
     
  4. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
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  5. Bob_in_OKC

    Bob_in_OKC Forum Resident

    Location:
    Dallas, Texas
    That's a good calculator page posted above. 40 dB gain is 100x. 46 dB gain is 200x. 60 dB gain is 1000x.
     
  6. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    I tried, and it works, but that's not what I was looking for. The gain calculator I already have and understand. What I meant is this:

    Given the known output of the cart and the known gain of the phono, you gave me the output Voltage coming out of the phono and into the preamp/integrated. It was .240 for Denon and .505 for something else. That's the metric I want to compute and get a calculator for, in order to now see if potential cart/phono combo is suitable for the input sensitivity of my integrated and receiver.
     
  7. Bob_in_OKC

    Bob_in_OKC Forum Resident

    Location:
    Dallas, Texas
    I took the 50 dB you gave me and divided by 20, got 2.5. I raised 10 to the power of 2.5 to get the gain ratio of 316. Multiply that by 1.6 mV and get 505 mV.

    In the other example, there was also the SUT, so there was the first step of 0.4 mV x 40 = 16 mV. Then 23.5 / 20 is 1.175. Raise 10 to the power of 1.175 is 15. Times 16 mV is 240 mV.
     
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  8. missan

    missan Forum Resident

    Location:
    Stockholm
    (gain/20)^10 x Phono in= Phono out
     
  9. Davey

    Davey NP: Electrelane ~ No Shouts No Calls (2007 LP)

    Location:
    SF Bay Area, USA
    Yea, it's hard to advise on just one part of the equation since the system gain is really what you are looking to optimize, based on your preamp gain and amp sensitivity and speaker sensitivity, listening levels, room size, and other factors. Modern amps tend to have higher input sensitivity and modern preamps tend to have less gain, because the CD player has a relatively fixed output level of 2V at maximum, and digital has a fixed maximum value. Phono cartridge output levels are anything but fixed, they specify an average level at a certain recording velocity and frequency, but it could go much higher than that at times, so you have to be careful when calculating the gain you need or you may end up over-driving one of the inputs, or even clipping on loud sections.
     
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  10. Mr Bass

    Mr Bass Chevelle Ma Belle

    Location:
    Mid Atlantic
    The issue is the headroom on the phonostage or what happens when a transient peak or even click/tic from record imperfections happens. Does the phonostage distort it or handle it? This will vary at different frequencies and is sometimes measured at low bass, midrange and high treble for better accuracy. Without knowing what the headroom specs are, it is possible to get an idea by playing records with known loud sudden sounds at bass, midrange or treble frequencies and compare at different gains but level matched.
     
  11. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    I'm concerned about phono only here, CD and FM tuner are more or less fixed.

    Does "higher" input sensitivity mean a lower value, and vise versa? Meaning, with input sensitivity of 1V I need at least 1V input coming out of the component for the amp to get full power. So, if the sensitivity is 0.5V - only half the power is needed, thus the higher sensitivity? Or am I reading it wrong?
     
  12. Davey

    Davey NP: Electrelane ~ No Shouts No Calls (2007 LP)

    Location:
    SF Bay Area, USA
    When I say higher sensitivity, I mean more voltage is required for full output. I think that is the common parlance. Power amps have a circuit gain figure, of course, usually around 25dB, but it's related to the output voltage, and consequently the output power, so is less practical to quote that way, but is directly related.

    My main point was just to be careful when cranking up the gain because the maximum cartridge output voltage is far more than the specified 5cm/sec average value, and is dependent on a lot of factors, including what kind of music you play, vintage of those records, etc.
     
    Last edited: Jul 9, 2017
  13. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    So, with 1.6 mV for Denon-110 into 46 dB gain, I get the output of 319 mV. Can this be insufficient for a receiver with 500 mV input sensitivity?
     
  14. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    I think it should be [10^(Gain / 20)] x phono input, unless my notation is screwed up.
     
  15. missan

    missan Forum Resident

    Location:
    Stockholm
    You are correct, sorry about that.
     
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  16. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    Using that formula, if I fed my Shure M97HE, 4 mV into Budgie Hybrid's 46 db, the resulting phono's output would be 798 mV - nothing too major. Even the 2M's 5 mV would produce 997 mV - still under 1V output, which is nothing catastrophic, considering the Stereophile gain calculator formula assumes 1V output desired.

    Taking the Guesswork out of Phonostage Gain

    "We’ve determined that we need about 1V output from the phonostage to adequately drive the preamp and power amp".

    Which answers my question whether Budgie Hybrid's 46 db is way too much for regular MM carts - I don't think it is now.
     
    Last edited: Jul 9, 2017
  17. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    On the other hand, again using the same formula, my Denon-103 at 0.3mV, fed into 60 dB gain, produces 300 mV at the phono output, and, fed into the same Yamaha receiver with 500 mV input sensitivity, sounds marvelous. So, 319 mV that the Denon-110 will produce into 46 dB may be enough, I think. But, chances are, it may just sound better with Pro-Ject Tube Box S, at 51 dB.
     
  18. blakep

    blakep Senior Member

    Absolutely. Can see this method working in that situation specifically because you're eliminating probably anywhere from 12-20 dB of gain that you have with an active linestage.


    Absolutely again.

    When people are running their calculations here they should be using approximately 10X the rated output of the cartridge as opposed to the rated output to figure out whether they are going to clip or overload, either the phonostage or the gear in front of it.

    Most cartridges are going to output approximately 10X their rated output on peaks on very dynamic records.

    Use that kind of number and you will draw a very different conclusion.
     
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  19. patient_ot

    patient_ot Senior Member

    Location:
    USA
    Not really. Define regular. Some MM carts have 5mv-6mv, or even more if we're talking higher output DJ carts. Try a wide variety of records with that amount of gain, including some that are cut hot and have wide volume dynamics in the pieces/songs. If you hear distortion, it may bother you, which means the mag's proposed calculations don't tell the whole story. Again, went through this recently.
     
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  20. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    I mean 3 - 5 mV for "regular", in audiophile terms. I will never own DJ carts, either. Most of my vinyl is Jazz or Fusion, with some Brazilian samba/bossanova, and very little classic/prog rock. Nothing too "hot" to start with. My listening levels are normal to medium-high, I don't think I ever go beyond the 2 o'clock position on my amp. So, even if I catch a "hot" peak some time, I will just wince and lower the volume.

    The only reason I'm considering a 46 db phono with MM carts is because it will also do HOMC. That way I can run, say, the DL-110 on the S-shaped arm of my Denon DP-110, and an MM cart on the straight arm, while running them both into the same phono. Otherwise, I will have to either change phonos every time I swap, which I KNOW will not be happening, or - forego one cart/arm altogether, and just run one type, which I'm loath to do, since I have a rare chance to run both on the same table. I would not, otherwise, insist on 46 dB for just MM, since I believe 38-41 db to be sufficient.
     
  21. russk

    russk Forum Resident

    Location:
    Syracuse NY
    So if you're running a tube amp with say a 1v input sensitivity it's pretty worthless or at least way off. In fact I can think of a lot of gear with an input sensitivity that low.
     
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  22. Bob_in_OKC

    Bob_in_OKC Forum Resident

    Location:
    Dallas, Texas
    If you have a preamp in there adding 12 dB gain, you're good to go with a 40 dB phono stage and a 2.5 mV cartridge output.
     
  23. russk

    russk Forum Resident

    Location:
    Syracuse NY
    Yes that's fine if you have an active preamp properly matched to an amp. If however you are running a passive preamp, receiver, integrated amp or are just feeding straight into an amp the KAB calculations are pretty useless. In the audiophile world of rave reviews, disappointment and all the conflicting opinions on phono preamps I suspect what's to blame is the fact that people just don't know how to match their phono preamp to their cartridge and amp. They buy based on reviews and hope it works and or accidentally matches what they need. If it does it gets a rave if it doesn't it gets panned.
     
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  24. patient_ot

    patient_ot Senior Member

    Location:
    USA

    On a 3mv cart, with 48db of gain, I got distortion on a Moody Blues LP with volume at 12 o'clock. Dialed it down to 42db of gain, no distortion when turned up even louder than that. Like I said, would ideally prefer to adjust gain 1db at a time to find the narrow sweet spot.
     
  25. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    So 41 dB may work well with 3.3 and 4.0 mv carts?
     
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