[srclose]

I'm planning to build a Cornet phono stage, but why build the Octal version rather than the standard version?  Are there complete instructions available?  Advantages/disadvantages?

[RogueAngel]

srclose,

For me, having built the octal version, there is one disadvantage - the tube sockets can't be directly soldered to the PCB, you have to use jumper wires.

The advantage I think is the tubes. Do a search on the tubes involved and you will see a big difference in the way these tubes are constructed. It seems to me that the octal tubes may be a little less susceptable to vibration.

I have only built the octal version, so I can not comment if any of this translates into a sonic difference, but I can say I am extremely happy with the way mine turned out.

I know Jim has obviously built both, but has never really commented about any sonic differences between the two.

Jim, any comment? or is it influenced more by tube choice rather than which family of tubes you use?

Bobbi

[gurevise]

I'd like to know what cartridges could be used with Octal Cornet?
I think, any cart with more then 2mv output would probably work well. But, it would be great to hear what people actually use with octal version and what do they think.  
Octal has 38dB gain, which is not much.
I know, some people add step up transformers and are very happy with it.

I have build souped up standard version and VERY happy with it.
I did not use any expensive parts, but installed current source option and added extra power supply filtering (CLC filter).

Sergey

[hagtech]

I would offer that the greatest reason to build an "octal" is if you already own a stash of superb NOS 6SL7 and 6SN7.  That, and I think the larger tubes look nicer when you show off the machine to your friends.

Soundwise they a really close.  Technically, the best design would use X7 gain stages and an N7 follower.

jh

[Sprite]

Jim,
I haven't started soldering yet and the mixed version sounds very tempting.  Could you tell me which parts need to be replaced from the standard 9-pin version if I want to build the version with X7 gain stages and N7 follower?  Thanks, -David

[gurevise]

Yes,

What is the advantage of using SN7 in place of AU7?
Is it just more current drive or something else?

I could use 9-pin analog of SN7 (like 12BH7) and increase current of CCS. I'd have to tweak PS resistors too. This would give more "drive" to 9-pin version.

So whu would we use SN7 in place on AU7?

Thanks
Sergey

[Ivan303]

Really no comparison, IMHO

Octals just BLOW AWAY 9 pin tubes in most any circuit I have heard

Especially the really good 6SL and 6SN types.

There's really no 12AU7 that compares to the better 6SN7 types, and I have the 7316's running in my current pre amp.  

For the bit of extra work, I would go Octal all the way.

I have a about a dozen NOS NIB Tung Sol Black Glass 6SU7's, which are regarded by many as one of the best sounding 6SL7 types in the Cary Phono Preamp.  I am really looking forward to trying them in the Cornet Kit.   That is, as soon as I get to the 845 amp and 26 preamp that are in line first

[hagtech]

I think the 6SN7 makes the best cathode follower.  More current, better linearity, better voltage ratings.  I like the tube.  I also like the 12AX7 for high gain amplification.  

Keep in mind, a LOT of the sound has to do with topology and circuit design, not just tubes.  I can make no claim that octals are superior to novals, nor the other way around.  Each tube has to stand on its own merits.

And the "hybrid" was just a passing thought.

jh

[Ivan303]

Gee, might have to build two, just to prove my point

Jim, have you tried a 12BH7 in the cathode follower spot?  does use a bit more heater current than a 12AU7, but might work well.

[hagtech]

Haven't tried the 12BH7 yet, although it's another tube I like.  Then there's the 5687...  

The choice of X7 and U7 fell out of the Trumpet design, where I just happened to decide I would design around novals.  Just because.  Same reasoning I used to make it a one-box chassis.  It seemed right.

jh