2. amps-preamps
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Looking for preamp recommendations to go with First Watt J2 - Under $1K on used market

My system is: 

First Watt J2 Amp
Passive preamp (DIY but good quality - Goldpoint dual mono attenuators, Cardas connectors, silver wire, etc.)
VPI Classic 1 (JMW 10 arm) w/ Ortofon Rondo Blue and Denon DL-301 MkII
Coph Nia MC phono preamp (60dB gain)
Jolida Glass FX DAC
Yamaha CDP
Klipsch Cornwall speakers
Kimber speaker wires
DIY Belden 4312 interconnects

I love the transparency of the passive preamp, but I am investigating the possibility of adding a little more gain into the system with an active preamp.  I listen to vinyl 99% of the time, and I find myself pushing the limits of the J2 with the passive.  Before I think about replacing my phono preamp section, I thought I might give the active preamp route a go.  
The J2 has an input sensitivity of 1000kohm.  I'd like a pre that has a MM phono section, since the Coph Nia does not.  That would give me the ability to use a SUT at some point if I wanted to.  But it's not a necessity.

Suggestions/recommendations are appreciated, especially if you are currently using the J2 as well.  I want to make sure there is a good match between the J2 and whichever preamp I go with.  And I definitely have no problem buying off the used market to maximize my available audio funds!  To be clear, I have been using a passive pre for a long time, so I'm not really all that savvy about active preamps.  

Thanks!

Tom
128x128tlarwa
larryi
3,886 posts
 

Tom,


First Watt specifies the input impedance at 100k ohms, but does not give a sensitivity number.  When you play CDs, you achieve adequate volume without the amp distorting?  If that is the case, then you do indeed need more gain from your linestage or from the phono preamp.  If the phono stage does not have a MM input, putting a step up transformer in front of the phonostage might not work because even a modest amount of gain might cause overload problems.

An active stage with modest amount of gain probably is the answer, but, it would be hard to find something in your stated price range that would compare with a well done passive. 


As for an alternative phonostage, most MC phonostages deliver, at most, 60-66 db of gain, and if your phonostage delivers 60 db of gain and it is notably inadequate, you are probably looking for at least 66 db of gain or more.  The alternative is a phonostage with MM input and then using a high gain step up transformer to get you more than the 60 db of gain from your current stage.

A friend of mine had a J2, which I got to use in my system for about two weeks.  It is a very good amplifier. 

tlarwa's avatar
tlarwa OP
6 posts
 
Thanks, Larry.  Yes, I have plenty of gain with my DAC/CDP so the gain issue is definitely with the phono stage.  My passive is a very good build using top quality parts, so I agree that going to a lesser active pre may not be advisable, even though it would solve my gain issue.  It's looking like my best bet may be to buy/build a SUT tailored to my Rondo Blue, and replace my Coph Nia with a good quality MM phono stage.  
almarg's avatar
Ag insider logo xs@2x
almarg
9,670 posts
 
First Watt specifies the input impedance at 100k ohms, but does not give a sensitivity number.
The manual for the J2 indicates a sensitivity of 1.4 volts for full power, and a gain of 20 db.  20 db of power amp gain is relatively low.  For example many of the Pass Labs amps are spec'd at 26 db, and many others from other manufacturers are higher.

Best regards,
-- Al
 

djverne
77 posts
 
Light speed atenuator....
larryi
3,886 posts
 

Another possibility is a different form of passive that employs a transformer volume control.  Instead of attenuating by burning off the signal in a resistor, transformer volume controls (TVC) attenuate by converting voltage to current.  At lower volume levels (lower voltage and higher current), the sound seems to have more drive and vibrancy (passives tend to sound just a bit dull dynamically).  To me, most TVCs are not very practical because they are stepped attenuators with too large a volume change between steps, and most are not remotely controllable. 

But, there are a few exceptions.  MyEmia sells TVCs made by Dave Slagle that employ autoformers.  While not cheap, these offer 1 db steps and are remotely controllable.  Also, they offer 7 db of gain (again converting current to volume), which might be enough gain to cure your problem.  I would contact Dave Slagle at MyEmia or at his own site Intactaudio.com (a supplier to the DIY crowd).  He probably can offer ideas even if his stuff might not be your solution.

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