Early McIntosh C20 which tubes are for phono

[Pup]

Early McIntosh C20 ; which tubes are for phono. V1 and V2 maybe?

My phono output seems low. Want to verify which tubes do what. This is the earliest version with the brass divider between top and bottom sections on the face plate.

Thanks

Bob

 

[macyjrm]

I don’t have a direct answer to your question, but weak phono tubes will result in what you are experiencing. However, I have several vintage tube preamps (with good tubes installed) and each of them has reduced volume compared to the direct line inputs. This doesn’t seem to be uncommon.

 

[billjoye]

12AX7 V1 L phono pre-amp
12AX7 V2 R phono pre-amp
12AU7 V3 L Cathode Follower, L AF Amp
12AU7 V4 R Cathode Follower, R AF Amp
12AX7 V5 L AF Amp, L AF Amp
12AX7 V6 R AF Amp, R AF Amp
12AX7 V7 L Cathode Follower, R Cathode Follower
6X4 V8 Rectifier

 

[Pup]

Thankyou! I have been looking for that for quite a while!

BC

 

[Pup]

FYI,

I think the C20 just needed to be used after full recap and cleaning. It woke up yesterday after about 20 hours use. I may try the new JJ 803S/12ax7 tubes in it. I have heard some great things from folks with good ears about them!

Thanks all!