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Concerned about my cart/pre pairing

Long story short..

I started with a Dyna DV20x2HIGH and a Dynaco PAS3x, then upgraded the pre to a Rogue RP-1. One day was cleaning my table and #%&%! up the needle, so I just coughed up the money for a new DV20x2LOW now that I had the Rogue's choice of higher gain setting for MC carts (58db). Purchased from a reputable local dealer. In reality when making the purchase I didn't know too much about how cart specs/phono stage gain, etc works (I'm just starting this HiFi journey), just went with what was suggested. Now, I notice that I really have to crank the preamp volume sometimes when listening to records and the output is definitely less than it was before. It still sounds good, but on the occasion I do crank the volume to near max (50-60 out of 60) I hear some noise in the upper ranges, maybe a little hiss. After doing some research about the subject I'm concerned that the 58db gain on the RP-1 might be too low for the 3mv rating on the cart, and I'm missing out on the best performance of the Dyna cart. Obviously when switching to my Bluesound NODE the volume output is WAY higher. 

So....at the end of the day I still enjoy the sound, but feel concerned about having to have the volume  so high, and wonder if I'm missing other things like detail, dynamics etc....or am I over thinking this?? Do I really have to invest in a new phono pre in the future? Was this not a good match?

Thanks in advance!
128x128jin78
jin78's avatar
jin78 OP
37 posts
 
Oh, and I tried to use a couple of the online calculators. Kinda steep learning curve for me right now but I believe the KAB calculator suggested 61db gain. Am I missing anything with a 58db to 61 db difference? I’m sure some of you more seasoned audiophiles have been down this road before!

If someone with more knowledge than me can help me out with the math: With my set up, is my TT plus Pre producing enough input V to the power amp? Do I have to crank the volume because there's not enough input?
lewm
13,052 posts
 
I thought I covered this in my earlier post.  We mentioned that 58db of gain applied to the 0.3mV output of your cartridge would yield a ~0.24V output from your phono stage.  Adding to that the 9.5db gain of your linestage would result in a net signal voltage output from your whole preamplifier of ~3 X 0.24V = 0.72V.  (9.5db translates to about 3X voltage gain.) The calculation gave a different result the first time, because I was working with a putative 7db gain from your linestage, as opposed to 9,5db.  Given that we now know the sensitivity of your amplifier is 1V and also given that you disclosed the fact you use powered subwoofers, which presumably relieves your main amplifiers of the power demands required for deep bass response, I would say you ought not to be suffering from lack of gain adequate to drive your speakers. 


"Faint background noise" can be what is known as "tube rush".  Sometimes that happens when you crank the gain on your tube preamp, which you are not really doing.  Maybe your tubes are going weak.  Also, was Chakster correct in stating that your phono stage uses two 12AU7 tubes, only?  If so, there has to be either a SUT built into the MC input stage OR there are solid state devices adding gain.  You cannot derive 58db of gain from two 12AU7s alone. Below is a useful website.

http://www.sengpielaudio.com/calculator-gainloss.htmhttp://

jin78's avatar
jin78 OP
37 posts
 
@lewm 

Thanks for breaking that down for me! So sounds like everything from the cartridge through to the power amp matches up well. Could there be any improvement by getting closer to the full 1 volt rating? By the way, I use a powered sub, but the mains are still running full range off the power amp. The sub is being fed by the preamp. You probably already realize this just wanted to point it out. It's my understanding that to relieve the mains of the work of producing deep bass you need to add a crossover or filter? Again, still learning all the different setups. If I remember correctly the RP1 uses a tube output stage, the phono stage may be solid state, I'll have to look into that. 
lewm
13,052 posts
 
I assumed that if you are using powered subs, usually those products have built-in electronic crossovers.  I guess I also assumed that the crossover is also driving the main amplifier you use for upper frequencies.  That's very worth doing if you don't mind spending the money.  As it is, then of course your main amplifier is working full range and the power demands on it are greater than I thought.  What you say about the RP1, which I know zero about and which I cannot even find on the internet (albeit I did not look very hard), makes more sense, if the phono section is solid state.  Technically, I think you should be OK so far as driving your amplifier to power the speakers, but the proof of the pudding is in your listening.  The symptoms you describe do fit the description of a lack of adequate gain somewhere in your chain.  Maybe try to borrow a preamplifier with more overall gain from phono input to linestage output, and see what that gets you.  Or borrow a 1:20 SUT.
lewm
13,052 posts
 

If you try using a SUT to solve your problem, keep in mind that you need to attach it to the moving magnet inputs of your phono stage, not the MC inputs..
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