Low gain?

[delp]

I'm currently using a phono cartridge with a 2.5mv output into my C220, but to get a nicely loud volume level in a smallish room (MC 402 and 88db and 90db sensitive speakers) the noise floor on most LP's is much too high and very distracting especially on low-level passages. Does this seem normal, if not correct? This seems like very low gain for a MM phono stage. Does McIntosh only optimize the C220 for only very high-output cartridges? For example many cartridge makers consider even 1.5mv as "high-output" for certain moving coils. Any thoughts? Thanks.

p.s. The sound is very, very nice---excluding the noise!

 

[sully1801]

I'm using a Dynavector DV-10X5 MC cartridge, which has a 2.5 mV output.
Same pre (C220) and a MC500 amp. No problem with inadaquet gain.
I have swapped out the original tubes, I'm using a pair of Tung-Sols in the phono stage currently, as the originals began to develop a rushing air backgound sound, the tung-sols are much more quiet.

 

[nsgarch]

Yes, it may be the McToobs from China are adding noise to the signal. You could try swapping the line 12AX7's with the phono 12AX7's to try and isolate the offending tube(s), but if they're all noisy, that won't tell you anything. Doubt it's the cartridge -- 2.5mV is a fairly healthy output, even for a mm cartridge. Regular MC cartridges range from 0.2mV to 0.65mV by comparison.

 

[jwrosenthal]

Had the same question when I got my Sumiko BP#2, which is only 2.5mv. I am running a Thorens 124 (which is not the quietest table on earth), through a MA6200, which is essentially the same pre as the C32. Although I do have to turn the volume knob higher than most carts to get the volume I want, the phono stage is near quiet with only the slightest hint of "air". The phono pre in your C220 is light years better than the one in my 6200, so it should be DEAD quiet.

I did however have an issue with my Fisher 500c (here's the tube comparison) where I could hear the "hum" on a low output cart (had to turn th volume up like you). I swapped my Grado (4.5mv which is high but wasn't high enough to get over the noise) with a Pickering V-15 (5.5mv) and the noise was much quieter as I had that much more signal. I then later swapped the original Telefunken tubes with a set of new Mullards and the noise is now almost silent. The Tele's I had were microphonic and the new Mullards (I bought a matched/low micorphonic set from Tube Depot), solved the problem. I also got a set of vintage Mullard 12ax7's in another tube reciever and compared them with the new Mullards, and dare I say the new ones are pretty close for 1/10 the price.

I say you need to swap your factory Chinese tubes with a good set of NOS 12ax7's (I vote for the vintage Mullards as they are the sweetest phono tubes I have ever heard...at $150each!!) The new soviet tubes from companies like EH or Sovtek (own the new Mullard label) are very good if you get them from a US importer that screens them all for QC (like Tube Depot...no affil)....well worth the gamble at those prices IMO.

James R.