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Preamp Headroom Question

Just bought a "lowish" output MC cartridge -- Lyra Kleos.

Background info: The Kleos' rated output is .5 mV. My phono pre is an ARC PH-8 which has rated gain of 58 db. The PH-8 is tied into an ARC Ref 5 SE which has rated gain of 12 db.

In most cases when playing vinyl the rig produces plenty of gain when the Ref 5 cranked up to 65 to 75 clicks out of 104 maximum clicks. But in a few cases, usually when playing some classical LPs, I have to turn the Ref 5 up to 85+ clicks to achieve acceptable gain levels.

The question: If the Ref 5 is cranked up to 85+ clicks, will I lose headroom in cases when the music hits dynamic passages? Also, I think playing the Ref 5 at such high levels increases the noise floor. That is I hear a lot of record hiss. Does all of this make sense?

I suppose the only solution is to insert a SUT, but it will come with its own cost. Probably need only another 5 to 10 db.

Any thoughts or suggestions.

Thanks.

BIF
bifwynne

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
12,099 posts
 
The rule of thumb with any phono stage is not how much noise there is when you lift the tone arm off the LP, but how much noise there is when the needle is in a good silent groove.

In the latter case the noise should be less than that of the groove. If not you have a problem and you can disregard what is happening when the needle is lifted off the LP (although it is nice if its quiet there, but with LOMC that is always a bit of a trick). An SUT could help, but you may well pay a price of reduced detail and impact (loading on LOMC cartridges is not critical but it is really critical on SUTs- you want to get it right).
atmasphere's avatar
atmasphere
12,099 posts
 
Ralph, I'm not sure I understand your comment either, especially the part about "in the latter case the noise should be less than that of the groove." Can you clarify? Did you mean "in the former case"?

Also, why would playing an essentially silent groove say anything more about the noise performance of the phono stage than an assessment that is made with the stylus lifted off of the record?

In most cases the noise floor of the LP is going to be higher than that of the phono stage. Since the noise of the phono section will be masked by the LP surface, it is only important for the phono section to be quieter than the LP. That is why lifting the needle off the spinning LP surface really isn't telling you much.

Now if the phono section proves to be the noise you hear when you set the needle down in the spinning groove, that is when you know you have a problem.

Silent grooves can be found at the beginning of LPs, and also between cuts.
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