shaka or mctube?

[turing]

at long last i've got round to startting my first valve pedals. been dithering and prevaricating for ages, but i etched the boards this afternoon. i'm going to throw myself in at the deep end and try both the real mctube, and the shaka tube. got paul marossy's layout for the latter, and the tonepad for the former.
it's destined to go in the same box as the efm vcf. and i was wondering if anyone had any strong opinions on which was better suited to complement the filter. i suppose it would be the preamp, going before the filter. which valve? i don't need extreme noise terror, rather just a bit of valve grit and punch. is the 12at7 or the 12au7 the cleaner?
in fact, are these suitable for what i have in mind at all? any mods/developments that have cropped up since those layouts were posted? i have checked quite a few threads on these pedals, and i see that builders with far more experiencee than me have had some problems, so any help would be much appreciated.

[aron]

i suppose it would be the preamp, going before the filter.

Are you sure you want the distortion before the filter? Unless you are sweeping the filter manually, the distortion might render the filter useless if the filter relies on volume peaks to activate it.

[Paul Marossy]

is the 12at7 or the 12au7 the cleaner?

The 12AU7 would be lower gain of those two.

[turing]

i'm doing it like a modular synth........a little patch panel at the side so you could have any order you liked. and the filter is cv controlled. but are those circuits suitable for putting line signals through? i notice paul marossy caseed his up like a guitar head.
and is there a page somewhere that lists the european equivalent valves? i think the 12ax7 is something like ecc83, but i'm not sure about the others

[aron]

Cool!

Just type in the tube in Google and the European equivalent usually comes out.

[Paul Marossy]

and is there a page somewhere that lists the european equivalent valves? i think the 12ax7 is something like ecc83, but i'm not sure about the others

Try viewing these pages:

12AU7 - http://tdsl.duncanamps.com/show.php?des=12AU7
12AT7 - http://tdsl.duncanamps.com/show.php?des=12AT7
12AX7 - http://tdsl.duncanamps.com/show.php?des=12AX7

[TryingToDo613]

You can download that tube finder from Duncans and it's great because it has links into several tube websites if you need more information. Nice (free) piece of software, especially if you're not always online. -ph

[transient]

This is what Bob from Eurotubes (www.eurotubes.com) has told me, when i was purchasing a tube for my ShakaTube:

An ECC83S ( 12AX7 ) is 100 mu or technically has a 100 times amplification
factor, an ECC81 ( 12AT7 ) is 60 mu and an ECC82 ( 12AU7 ) is only 17 mu...

...
emre

[mojotron]

is the 12at7 or the 12au7 the cleaner?

The 12AU7 would be lower gain of those two.

In pedals, I have found that the 12AU7 has a thinner sound than the 12AX7. Certainly most 12AU7s will distort and compress less than most 12AX7s. I actually have a pair of super hot chinese 12AT7s that blow away most 12AX7s wrt overdrive - but the type of tube and manufacture are more subjective than picking transistors and opamps.

I like a lot of NOS tubes, but except for the mid '60s Mullard 12AX7 I have not found a NOS tube worth spending more money on then a new tube in a pedal application - where you have just the 1 double triode.

Of the accesible tubes these days - the tubes I think are the most distinctive are:
- The JJ 12AX7 - really interesting compression and over drive - it has the more distinctive sound IMO - it's a great sound, but you have to like that sound because you get a whole lot of it. Great even clean sound.

- The GT 12AX7M - don't believe the hype about being reissues of Mullards - they just aren't wrt overdrive. But, after about 50-100 hrs of use they do have a great sound that is related to an old Mullard. I use these for every thing - 2nd only to the NOS Mullard 12AX7. The 12AX7Ms sound great clean, but have a great deal of power when you really want to move a lot of sound with compressed overdrive.

- The EI Elite 12AX7 is a great tube - this is likely the most balanced tube for taking the clean sound character thru being over driven. The 12AU7 is nice too - but a little too thin for me. But, only buy the EI Elite stuff - the regular EI tubes are way too variable in quality. These are great for getting bell like tones with med-overdrive - very cool sound.

- The NOS Mullard 12AU7 - these cost about what a new tube would cost, but you get some of the Mullard NOS magic with these - that is you get a very transparent full sound that is, warm with rich, very complex upper mids. The major difference from the NOS Mullard 12AX7, sound-wise, is that you just don't get the depth of sound complexity that you get with the Mullard 12AX7.

- The EH 12AX7 - this is a very good tube. These are just good all the way around. But, they are not as distinctive as other tubes - it's just a really nice middle of the road tube.

- The Sovtek 12AX7WTX - one sweet tube too!

Hope this helps  

[turing]

wow, thanks everybody for such comprehensive help.

my original idea was to get hold of a sovtek and an eh and compare them. in fact, my real original idea was to be able to switch between valves.
but i chickened out of that one, and i think ill just have a 'spare' port so i can 'hot-swap' (as i believe the kids call it) between 2.

ps. does anyone have any recommendations of a good source of valves in england? rs just seem to have the bog standard selection