Preamp tubes: tonal differences

DrGonzo

hey, tube newbie here.

Just a enquiry... does anyone know what the differences in sound is between a 12ax7 and say a 12at7

I read that 12at7's are slighlty lower gain, how does this affect your sound/tone. Will your amp have a general cleaner sound, less break up different tone etc...?

Gearhead

I would expect there's more difference between different brands making these little tone bottles than there is between the types. Having said that - your amp will sound different depending on what amp type it is.

Let's first agree that with 12AT7 and 12AX7 the power of your amp is not going to change, since you're only affecting the input gain. You might not get to the maximum power because your input signal is not enough, but chances are it will be. Secondly, consider that a high-gain amp such as your .22 potentially has so much gain in the preamp that it will saturate the preamp tubes themselves already - have you ever tried turning down the bass AND the mids AND the treble while turning up the master? It changes the tone of drive channel to have less distortion. So changing to AT7's will be similar - less drive in the preamp makes for more clean tone, but nothing your amp can't already do.

DrGonzo

i gave that a try, not 100% sure wat u mean tho?? like turn all eq knobs down then turn up master and volume to desired level, then turn up bass mids and treble??? it didnt seem to make much difference??

its not really a issue tho, i just find the amp breaks up quite early (at like 4-5 on master with volume/gain at 2-3) and would be nice to get a bit more clean headroom at rehearsal levels. i would think it prob also cause of my emg active pickups...

Gearhead

Never mind the EQ - it is
On the .22 in clean channel the tone stack AND the volume come in between the first and second gain stage. The master comes after the second stage. You should imho get more clean headroom by turning down the volume to 1-2 and turning up the master to 7-9.
I wonder if the 12AT7 would have enough gain to drive the second gain stage unless you open up the volume+tone pots quite far.

Karel-Mars

I usually pop in a 12AU7 (ECC82) if I want clean sound + better tone. Did you know that all these miniature tubes have the same pinout? (12A_7 range mostly) You can interchange 12AX/Y/T/U7 without blowing up the amp. Just be carefull when you pull them out, or insert them. You don't want to destroy your valuable tube/socket. This way you can find the right tone for your playing.

DrGonzo

Thanks will give that a try when i have some extra cash lying around to spend on a tube!

Anyone have any opinions on the 5751 tubes (i think thats the number...)

AlanRatcliffe

DrGonzo wrote Anyone have any opinions on the 5751 tubes (i think thats the number...)

I love 5751's in place of a 12AX7 in V1 to tame the gain of an amp. IMO, doesn't neuter the tone of the amp like some of the lower gain 12A_7 valves - keeps the sparkle and tone and just brings the preamp gain down.

nicovlogg

Total tube newb here - but if I'm replacing 1 valve with a different model, say a 12AX7 with the 12AT7, how will that affect the other pre-amp tubes? Using a marshall jtm60, wondering which one of the four little glass things does what!

AlanRatcliffe

Some good info on the KCA site:
http://www.kcanostubes.com/content/newsletter_details.asp?ArticleID=5

Specifically Fender, but that applies to most tube amps.