I have recently gone through a lot 6CG7 tubes and thought it may be helpful to give a review of the different tubes I have used. But first, I would like to tell about my most recent purchase.
I've finally found audio nirvana! I just bought a pair of nos Amperex 6CG7 tubes and placed them in my Ultra DAC and paired them with RCA Clear Tops in my Ultra Pre Amp with the stock opamps. From the very moment that I listened to that combination I was stunned by how good the sound is. I have been looking for quite a while for the right combination of tubes that would give me a sound that was on the warm side of neutral with good transparency, air,sound stage, bass,treble and resolution as well as a smooth mid range. I have found that combination with the Amperex and Clear tops. The Amperex tubes produce a lot of deep, tight and smooth bass. The treble is crystal clear and natural and the sound has great depth realism and detail. I am using Magnepan 1.6 speakers and a Parasound Halo SS A21 amp and the amperex tubes bring out every last bit of bass that the Maggies can produce and then some. You would also be hard pressed to tell that I'm using a solid state amp instead of a tube amp. I like the tubes so much that I just bought 4 more today for $70 off ebay. They will be the last tubes that I buy.
Now for the tube review.
Equipment used- Van Alstine Ultra DAC with stock opamps, Ultra Pre Amp, Parasound Halo A21 amp, Music Hall 25.2 CDP as a transport.
Music- Jazz, Vocal Jazz, Blue's, Classical and Rock.
Tubes tested in order of my personal favorites (all are NOS 6CG7's unless stated otherwise).-
Amperex
RCA Clear Tops
Tung Sol's
Mazda-Brimar's
1960's Sylvania's with the Yellow Lettering (the green lettering is from the 1950's and is supposed to be better sounding but they are hard to come by)
Sovtek 6N1P's
Electro Harmonix 6CG7's-worst of the bunch
Amperex tubes-
Smooth clean sound with great depth and presence to the music with excellent well controlled tight bass, clear clean treble and timbre (cymbals sounded very natural with good decay and the leading edge of piano notes was smooth with no ring) and a very sweet midrange. They lean to the slightly warmer side of neutral. Good sound stage, average to above average air and transparency when used in my DAC with the RCA Clear tops in my Preamp. I think that they present less air because of the depth of the music which really has a live sound to it. My only criticism is that they may produce too much bass for some tastes.
RCA Clear Tops-
Stregnths are very wide sound stage with tremendous air and transparency. Good bass and well balanced sound but they tend to lean on the brighter side of neutral and can be slightly ssssibilant. They pair well with other tubes and do well in a DAC and Pre amp.
When I used the RCA's paired together in both my DAC and Pre the sound stage appeared almost infinite and the music was the most transparent. Treble seems to have less resolution but it was pleasing. I really love the sound stage, air and transparency. With certain music and listening in the dark
the sound can be mesmerizing. If the sound was only a little warmer with less sibilance this would be may favorite combination. And at times I may switch back and forth with the Amperex tubes in my DAC.
Tung Sols-
These tubes could have ranked up there with the Amperex as they have excellent bass and midrange with a very smooth, liquid sound with good depth and realism but treble was slightly pushed back for my taste. They present a good sound stage but only average air and transparency. They would be a great choice if you like to listen to Rock and roll and older brightly recorded Cd's. They sounded equally good in both my DAC and Pre when paired with the RCA's.
Mazda-Brimar's
These tubes really are a funky tube. They do best in the DAC and need careful matching with other tubes. When used in my Pre they have too much bass and it seems too loose. But in my DAC they are warm and smooth sounding with a very natural sound, however they seem to lack bass when paired with the RCA's in the Pre. (note that I had upgraded to the Burr Brown Op Amps in my DAC for a while and the Mazda's had excellent bass in the DAC and boomy bass in the Pre, I have since removed the BB Op Amps and put back in the stock OA's.). The Mazda's would be great in my system if I used a sub.
Sylvania's
These tubes have a very neutral sound. They have very good resolution other than that they are average in all area's. I could live with these tubes but there are better out there. They seem more suited for my DAC. In my preamp the bass was just a little loose sounding with bass heavy music.
Electro Harmonix-
Where do I start! These are supposed to be exact copies of the RCA Clear tops but they sure don't sound like it. They had no sonically redeeming qualities in my system. They were way too bright with irritating sharp harsh treble and they lacked bass. Vocals sounded less natural and the midrange sounded dead. They were also very ssssibilant.
6N1P Sovteks-
Good overall sound as these were the stock tubes in both my DAC and Pre. But the 6CG7's just sound better with more depth and resolution to the music (except for the Elctro Harmonix tubes). If I had not heard the 6CG7's I could be perfectly happy with them.
I hope this helps some but every one has different equipment and tastes.
