2. amps-preamps
  3. 134834-10953

Phono stage gain too high??? Should I return it??

Just purchased a used ARC PH-7 and am wondering if it is defective as the gain seems awfully high.  I have it running into an ARC LS-27, and it's fed by a Project RPM10 with Sumiko BlackBird Hi Output (2.5mV output, 47K ohm).  I was expecting it to be the lowest gain input in my system, but it's so loud, I cannot set the LS-27 anything over 7/8 (my digital input, Schiit Bifrost is in the 12-16 range), and it does not go soft enough for late night listening.  

The only way I can get it to a reasonable gain level is to set the load at the lowest setting (100 ohms), which totally squashes the dynamic range.

The seller gave me a 30-day return window.  I really like the PH-7 in terms of tone, but is something wrong with it??  It's rated at 57.5 db gain which is modest by most standards, I think.  I have other phono stages rated at 60+ db and in my system, they exhibit LESS gain.  How is this possible??
tswei99
salectric
747 posts
 
That is odd how your 60 dB gain phono stage has lower output than the 57 dB ARC.  My guess is that your other phono preamp has a low input resistance, perhaps 100 ohms or so, and the ARC has a 47K input load.  I am not familiar with your cartridge, but if if is intended to have a 47K load it may have much less output into a 100 ohm load.

That said I have always regarded the ARC phono preamps as an aberration in terms of gain.  They have far too much gain for a typical MM cartridge and barely adequate gain for a low output MC.  But gain suitability is very system-specific.  In my system right now I have a LOMC (.3 mv) feeding a SUT and phono preamp with a combined gain of 60 db with a passive attenuator (no gain) instead of an active linestage, and I have plenty of gain.  
tswei99 OP
17 posts
 
Thank you all so much for the thoughtful responses.  Just a couple more details:

1. I DO have the LS27 set on LOW gain for the phono input, and configured that way the Phono has higher gain than the Digital which is also set on LOW.

2. I am a relative noob and got the Blackbird in a package deal and am loathe to sell it, esp given how much cartridges of that caliber cost.

All that said, I am just loving the ARC tube sounds, it blows away everything SS I have tried.
jperry
2,430 posts
 
You have the wrong cartridge for your phono preamp. You need something with less output. I think .4 to .8 mv would be suitable.
tswei99 OP
17 posts
 
Arrrghhhhh....anyone interested in buying a low-mileage Blackbird??
dover
2,182 posts
 
@tswei99

I DO have the LS27 set on LOW gain for the phono input, and configured that way the Phono has higher gain than the Digital which is also set on LOW.

By changing the CD input to medium/high you can at least equalise the 2 inputs.

Are you running single ended or balanced interconnects between your LS27 & power amp ? If you are running balanced you can reduce the gain by changing to single ended interconnects.

Have you checked your power amplifier to see if it has adjustable input sensitivity to reduce the overall system gain. This is another way of getting your preamp volume into its optimal range, once you have equalised the inputs.



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