Hi there,
First of all, Dutch chap here so (please) excuse the grammar.
Newbie here from The Netherlands, 40ish Sound-Engineer, since fall ’19 very enthousiastic about the combi BottleHead Crack & AKG K340 both introduced by Tom-s (he actually bought my two 2xCV4079 to 6080 adapters which unfortunately were not working in my SpeakerAmp (DIY). A few months later I ordered another from
@Deyan 
to put in my freshly bought secondhand Crack.
So now powered with a lot of info and knowledge from Tom-s I’m cruising trough Tubie Wonderland to get my kicks and a lot of musical enjoyment!
This will be a review of some 6C5G tubes. Succesor of the 76 tube (27-37-56-76-6C5 etc).
Just for all of you who are interested in something else than 12AU7’s...
These tubes, supplied by Tom-s, will be put on pole position in a BottleHead Crack, normally filled with an ECC82 of some sort. Using an adapter (home-made) and Speedball.
Rest of the line-up:
-Source: Qobuz 16/44.1
-Streamer: M1CLIC Musical Fidelity (also used as pre-amp)
-Interconnect cable: SharkWire
-Headphone-amp: BottleHead Crack with 2x GEC CV4079 as output tube.
(Bottlehead upgrades: Speedball, Vishay 100uF MKP output caps, Choke, Cree Diodes, removed volumepot, removed RCA chassis and hardwired ‘interconnects’ from SharkWire, diy powerlead (from Linn K400).
-Headphone: AKG K340 (fed by Mogami StarQuad cable).
Yesterday I’ve rolled some 37-76 and 6J5G tubes, the musical favorite was Adzam 76.
So this tube will act as ‘reference’-tube.
Chosen music:
-Trondheimsolistene - Magnificat IV. Et misericordia
-Darondo - Didn’t I (Listen to my song: The Music City Session)
-Robert Miles - Loom (Miles Gurtu) ---with Trilok Gurtu---
Tubes:
-76: Adzam
-6C5G: Brimar, Sylvania, Fivre, RCA, KenRad
Starting of with Adzam’s 76 conclusion:
Very nice tube, neutral but with enough character to be exciting.
Warm sounding tube, full upperbass but a little recessed lowbass/sub, beautiful mids (very nice atmosphere and acoustics), somewhat recessed highs but very pleasing and with enough detail. Spacious presentation, pleasant unobtrusive sound.
Spoiler alert: this tube will actually fall into second place...
5. Brimar
Slightly narrow presentation, highmids-orientated therefore a little harsh sounding. ill low definition due to muddy lows. No common space/no interaction, seems disjointed. Pale, no layer definition.
4. Sylvania
Direct sounding tube. Cloudy due to strong midlows/lows. Feeling of a “digital cut-up” signal, due to little cohesion/transparency/dynamics. Absence of detailed highs, obscured. Restless image.
3. Fivre:
Beautiful acoustics, beautiful mids. A little harshness also caused by recessed lows, therefore little detail in bass/upper bass. Beautiful depth, good natural presentation.
2. RCA:
Medium direct, spatial presentation. Beautiful placement of instruments. A full sounding tube. Slightly withdrawn mid layer. Fine interplay, beautiful instrument separation. Slightly cloudy due to the abundance of bass/midbass. Musically tube.
1. Ken-Rad:
Unfortunately both tubes had a little humm (one more than the other).
Beautiful natural image, very good placement, clear acoustics. Beautiful bottom-end of voices and wooden instruments. Slightly unclear retracted basses. Great presentation. Musical! SPACE. Detailed upper bass, dry, involved tight sound. More details than all the others.
After this evenings runs I actually could live with any of them, they all outperform most 12AU7’s, and the top two ’ll even pale the best of them (and yess I’ve heard them).
The remarks are pointed out with very criticized “Engineers Ears”, and are sometimes a little over-exaggerated, but are used to explane the impressions of the tubes characters...
I'll find a way to add photo's later on...
