Rethinking Phono Preamp Gain Settings

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

  1. avanti1960

    avanti1960 Forum Resident Thread Starter

    Location:
    Chicago metro, USA
    I was never really completely happy with the nominal range of phono preamp gain for a given cartridge as suggested by the well accepted KAB calculator. Typically I would bump it up to the next highest gain setting if possible.

    For example I ran my .3mv cartridge at 60 db gain (KAB suggest 61db) but it sounded much better using the 66db gain setting.

    My newest cartridge has a .5mv nominal output and the calculatd gain setting is 56db.

    The 56db setting sounds somewhat lifeless and anemic (compared to my other sources). Bumping it up to 66db (quite a jump) sounds incredible- micro dynamics, punch and drive that are so much better than the 56db setting.

    I searched for other recommended gain setting info and found this article in TAS that is based on an output level of 1.2 to 1.5 V output from the phono preamp.

    By this formula:

    Ndb= 20 log V1/V2; Ndb= gain setting, V1= desired output voltage, V2= cartridge voltage.

    Converting mv to V = 1/1000, e.g. .5mv cartridge = .0005 V.

    Ndb= 20 log (1.2V / .0005V ) =
    Ndb= 20* log (2400)
    Ndb= 20* 3.3802 (use the log function of a windows scientific calculator)
    Ndb= 67 db.

    Now that seems more reasonable (IMHO) 67db for a .5mv cartridge. Since the 66db gain setting on my preamp sounds so much more alive than the KAB recommended 56db, I will use the above formula as a reference for future cartridge output / phono preamp gain requirements.

    Try it if you haven't already, you may be in for quite an improvement in the sound of your vinyl......

    Taking the Guesswork out of Phonostage Gain
     
  2. KT88

    KT88 Forum Resident

    I almost always prefer a slightly lower gain setting to the standard or to a higher gain setting. It isn't universal, and phonostages differ in sound enough that there is so much more to it than gain that it can't be applied universally to different phono stages. I think that your opinion will also change based upon the amp and speakers that you use. No harm in trying a bit higher or lower setting though.
    -Bill
     
  3. russk

    russk Forum Resident

    Location:
    Syracuse NY
    That's how I've always figured my gain setting. I just brought this up in a thread last night. The math not the Absolute Sound article. I was taught that by my dad in the early 80s. Back then people figured if you were within 2db you were good. Phono preamps are quieter now and amps tend to have much easier to drive input sensitivities so I think there is even more leeway but if you go too low, especially with tube gear, I find that you suck the dynamics out. Too high and of course you can run into overload and clipping and the sound gets harsh. Fortunately I found that good phono preamps today are also harder to overload.

    I typically find that my preferred gain being a little higher or lower then optimal depends on the preamp and gear sometimes a little higher is better sometimes a little lower. As long as I'm not more than 4 or 5db off I usually don't run into any issues. That said some phono preamps like the Leben seem to be doing their own thing. It has a very low stated gain and it's one of my favorites. Though I assume the Leben and Line Magnetic integrateds and I've heard it with have an input sensitivity of around .75v
     
  4. Rolltide

    Rolltide Forum Resident

    Location:
    Vallejo, CA
    Perhaps this explains why my 0.4mv Koetsu sounds so much better with my SUT on the wrong setting (1:40) then the right setting (1:20). It's not any sort of hedonistic loud-button sounding better either, it really opens up the dynamics so much more.
     
  5. russk

    russk Forum Resident

    Location:
    Syracuse NY
    Wow. 1:40? That is really interesting. I'd have assumed that would overload it but if you do the math it kind of works out. That guy made a great and weird phono preamp. I wish someone would do a review and measure it and tear one apart and see what makes it so great. Or at least interview him and get his ideas behind the design.
     
  6. Rolltide

    Rolltide Forum Resident

    Location:
    Vallejo, CA
    I actually wasn't aware the Leben had a non-standard gain, it never occurred to me to check. In hindsight, it might explain why I've never really been a fan of any cartridge that required the 1:20 setting. But with other cartridges that called for 1:20, they sounded muddy on 1:40, as you'd expect.

    [​IMG]

    The circuit to me looks like something out of a kit from 1962. Nothing especially exotic looking, but it sure does win. I know the transformer is custom made for this device, probably has a lot to do with it.
     
    russk likes this.
  7. Interesting. If I did that right I get 68db for my .4mv cartridge. I'm running it at 60db, but the max is 66db. I think the KAB calculator has it at 58db if I recall. I've tried it more than 60db, and on some material it sounds better at 63 or 64db (punchier, more bass). I've just left it at 60db for quite a while now which I think gives the best balance to my ears, but I may have to experiment again.
     
  8. Bob_in_OKC

    Bob_in_OKC Forum Resident

    Location:
    Dallas
    I've read the recommended impedance for Koetsu is 30 Ohm. Running into a 47k Ohm input, it would take 1:40 to work out to 30 Ohm on the input side of the SUT.
     
    Rolltide and Davey like this.
  9. patient_ot

    patient_ot Forum Resident

    Location:
    USA
    If I had my way, all phono preamps would allow you to adjust gain 1db at a time. There is a fine line IMHO/IME between getting the gain a little hotter than a generic 35-40db setting so it's fine tuned to your cart, and getting too much gain, which results in distortion on dynamic and/or hotly cut records.

    I recently got a cart with 3mv of output. My preamp only has fixed gain settings of 30, 42, 48, and 59db. 42db was too light for the cart and 48 was too much gain. The proper number, for my tastes was somewhere in the middle. No incremental adjustments so I leave it at 42db rather than have distortion.
     
    punkmusick likes this.
  10. blakep

    blakep Forum Resident

    Agreed. And even more important with very low output cartridges IMO.

    I have been using a phono stage for the past 10 years with infinitely variable/adjustable gain between 55-75 (although it is a current gain amplifier and a bit different in that absolute "delivered" gain will vary to some extent with the internal impedance of the cartridge used-it tends to work better IMO with low impedance designs).

    So I have the ability to adjust gain very quickly and very broadly. If you have that ability you soon realize how important it is, how narrow the sweet spot is and, to a certain extent, how gain requirements can actually vary from record to record based on how they've been cut: hot, cold or in between. I'm not into the audiophile nervosa of changing gain for individual records; much like setting VTA/SRA, my approach is to set it to work well with the majority of my records and listen to music.

    That being said, the window for optimal gain is IMO very narrow. Personally, I think if you have to err on one side as opposed to another, a little less gain at the phono stage is probably better than too much, but this may be system dependent and tube preamps ahead of the phono stage seem to offer challenges, so the generalization is just that. A generalization.

    I do, however, think that some listeners confuse "loudness" and "punchiness" with dynamics. In the era of loudness wars and compressed digital music there are listeners who think this kind of presentation is "right" and seek to turn their vinyl listening experience into something similar by jacking up gain (you continually see posts on audio forums from listeners seeking to volume match their CD and turntable listening, most often by jacking up phono preamp gain levels to the point of ridiculousness). I have my doubts as to whether this kind of approach ends well or results in decent analog sound. ;)

    Almost all of my vinyl is analog cut and much of it has pretty broad dynamic swings, often in the 18-20 dB range. Too much gain and, even with a very good phono stage and preamp or integrated ahead of it with vinyl like that, it's pretty easy to hear that something is not quite right. In my systems over the years, some of the numbers being bantied about with respect to gain/cartridge output level in this thread would make my ears bleed, but our ears are all different along with our systems & subjective listening preferences.
     
    punkmusick, AaronW, missan and 2 others like this.
  11. russk

    russk Forum Resident

    Location:
    Syracuse NY
    There is definitely beauty it it's simplicity and you cant deny that sound. It's a beautiful phono preamp.
     
  12. DrZhivago

    DrZhivago Hedonist

    Location:
    Brisbane Australia
    Excellent post!

    Using the above, I have just re-calculated gain settings for both of my carts. 2m Blue, and 2m Black. 2m Blue sounds much punchier now.

    Kind Regards
     
    Optimize, punkmusick and avanti1960 like this.
  13. Subvet

    Subvet Forum Resident

    Location:
    Southern Maine
    With my .4mv Soundsmith I run 66 db gain. I can go to 76, which I may try, but the 66 sounds excellent. The provided formula say 69.5 is the number to reach 1.2 volts.
     
    punkmusick likes this.
  14. avanti1960

    avanti1960 Forum Resident Thread Starter

    Location:
    Chicago metro, USA
    Absolutely, there are no hard and fast rules.
    The point of the post was to suggest an alternative to the KAB calculations and to try a higher gain setting if you have the capability.

    The TAS calculations worked well for me without even knowing they existed and the KAB results left me wanting more.

    I would recommend to anyone seeking a new cartridge, preamp (or both) make sure they have the capability to achieve the TAS calculated
    values.
     
    punkmusick likes this.
  15. avanti1960

    avanti1960 Forum Resident Thread Starter

    Location:
    Chicago metro, USA
    The idea of a SUT is also interesting. possibly a way to achieve the higher TAS recommended gain with less risk to adding noise / grit? I do not have that issue with my hardware but maybe it would be a solution for some.
     
  16. avanti1960

    avanti1960 Forum Resident Thread Starter

    Location:
    Chicago metro, USA
    Can't fault your experiences but this has not been the case for me. Adjustments in +/- 10db are likely too coarse but I believe if your calculations are close to target you should be able to achieve excellent sound with quality hardware.
     
  17. 33na3rd

    33na3rd Forum Resident

    Location:
    SW Washington, USA
    This method works particularly well for those running Passive Preamps. Thank you for sharing this!
     
  18. patient_ot

    patient_ot Forum Resident

    Location:
    USA
    People have different ways of doing the calculations. The TAS and KAB methods are different, to name just two examples. Not all records are cut at the same volume either. Some records also have wide volume shifts. Agree w/ @blakep that the optimal gain should be a fairly narrow range for any given cart.
     
  19. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    What is the gain of your phono? After 1:40 SUT treatment, you have an output of 16 mV (!) going into the phono...
     
  20. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    This thread made me re-calculate the needed gain for Denon DL-110, an HOMC cart I just bought. This formula points squarely at 50 dB (51) - something I have in my Tube Box S already. It may have just saved me some coin...
     
    punkmusick and Gumboo like this.
  21. Bob_in_OKC

    Bob_in_OKC Forum Resident

    Location:
    Dallas
    With 23,5 dB gain in the phono preamp, the 0.4 mV Koetsu, and the 1:40 SUT - it's only at 240 mV.

    Leben Hi-Fi Stereo Company

    1.6 mV from the Denon and 50 dB gain is 505 mV.
     
  22. russk

    russk Forum Resident

    Location:
    Syracuse NY
    :laugh:
     
  23. russk

    russk Forum Resident

    Location:
    Syracuse NY
    The question is what is the method that KAB is using? The formula in the Absolute Sound article is the only one I have ever heard of and it's been commonly used since at least the 70s
     
    punkmusick likes this.
  24. Bob_in_OKC

    Bob_in_OKC Forum Resident

    Location:
    Dallas
    KAB's web page says, "The optimum gain is based on achieving 325mV rms output at 5 cm/s." The formula is the same. It's the desired output level that is different.
     
    punkmusick likes this.
  25. Benzion

    Benzion "Cogito, ergo sum" Forum Resident

    Location:
    Brooklyn, NY
    .24 V output from the phono to the preamp/integrated? Isn't it a bit on the low side? Or it depends on the input sensitivity?

    Same question for .5V of my Denon.

    Edit: I think I just answered the second question, the input sensitivity of my Yamaha receiver is 500 mV - right at the lowest acceptable threshold. So, I quess it will work. Not so sure with 45/46 dB gain now, it may dip below 500 mV.

    Can you calculate the output of my Denon 103 at 0.3 mV into 60 dB gain? And also the DL-110's 1.6 mV into 46 dB?
     
    fldveloce likes this.

Share This Page