12AX7 pre-amp valves

[NancyJohnson]

For some time I've been using a racked UK Ashdown ABM EVOIII; it runs superclean, so with this in mind, for the last couple of years I've been using a Sansamp RBI as my frontend and routing this into the effects return of the Ashdown.

The last couple of days, I've been reading a lot online about swapping out the 12AX7 preamp valve for something different. As far as I can ascertain, swapping the valve is simply a case of taking the old one out and inserting the new one. No calibration.

So, the question. Which valve?

The Ashdown has a valvedrive option that adds a bit of fuzz, but it's far from the fuzz/dirt that I would prefer; it's a far cry from the Sansamp. This could be down to the circuitry on the Ashdown, it could be that the valve isn't hi-gain enough. I'm up for a bit of experimentation, especially where it could benefit others.

Any help appreciated!

[casapete]

No personal experience of swapping preamp valves, but some good info here
in the test report section which may be useful.

https://www.watfordvalves.com/

[MoonBassAlpha]

Yeah, just plug n play with 12AX7/ecc83 types. I did this on my Trace guitar amp on Sunday which cured an odd after-note noise completely.

[NancyJohnson]

I decided to shoot Ashdown a quick email. They replied:

[color=#1F497D][font=Calibri , sans-serif][size=2][i]The Valve Drive feature is not at the end of the chain and is only there to warm the signal up somewhat and mix a bit of drive to the signal. You could try a different valve, but I’m afraid you will be disappointed with change, if any.. You can use any good 12AX7 valve.[/i][/size][/font][/color]

So I've shot Watford Valves a message. Change is as good etc.
P

[bigjohn]

I like Watford Valves and have bought from them before.

I do prefer Mullards though, which are only available NOS or used. Same as the old Phillips and GE ones.

The new ones just aren't as good and don't hold their resale value, which, if you're experimenting with different valves is surely a consideration.

Don't buy Cryo if you do go new. It's snake oil.

You'll get more of an idea using used valves with different gain.

Edited February 9, 2016 by bigjohn

[NancyJohnson]

Just had a conversation with Derek at Watford Valves. It's just brilliant talking to someone who knows their stuff. I've said he should join Basschat to impart some of his knowledge.

So I have two different 12AX7s incoming, which I'll test over the weekend.
P

[geoffbyrne]

If you want to read expert opinions about amp valves go here:

http://www.guitaramplifierblueprinting.com/

You can also ask Myles a direct question by going here:

http://forums.musicplayer.com/ubbthreads.php/topics/1351234/222

and joining the forum (which is to close shortly).

G.

[NancyJohnson]

I put a Tung Sol 12AX7 in. There's a distinctive growl to the pre-amp now at low volume. It's more defined. While it's nowhere near the tone of the Samsamp, it seems different tonally and there's seemingly more response from the tone-slider controls and the three bass/mid/treble pots. Interesting.
P

[iiipopes]

In the USA, there are two places that have a wide variety of 12AX7 - ECC83 valves and there are articles about how each of them compare. There are also articles about the gain structure of the various 12A_7 tubes, and how you can change out one of the family to get different gain characteristics. For example, Fender's classic Bassman "tweed" tone uses a 12AY7 instead of a 12AX7. The comment from Ashdown is a conclusion based on two principles: 1) most bass players desire or need the highest clean gain possible to support the band, which is what a 12AX7 - ECC83 is designed to do, and 2) they don't want any warranty claims from using other tubes that get overdriven to failure.

http://www.thetubestore.com/Resources/Guitar-Amp-Info/Gain-Factor
https://www.tubedepot.com/t/tubes/preamp-tubes/12ax7-ecc83-7025-cv4004

[bassmachine2112]

Hiho the other side of the coin is to go lower gain-ecc81 if your amp is a bit fruity.
Your Sansamp should be able to dial in what your after.

[geoffbyrne]

When I used valve amps, I was quite partial to the 5751 valves which gives roughly 70% of the gain of the 12AX7. Check them out.

G.

[2elliot]

[quote name='NancyJohnson' timestamp='1455365449' post='2978427']
I put a Tung Sol 12AX7 in. There's a distinctive growl to the pre-amp now at low volume. It's more defined. While it's nowhere near the tone of the Samsamp, it seems different tonally and there's seemingly more response from the tone-slider controls and the three bass/mid/treble pots. Interesting.
P
[/quote]

That sounds interesting. I may have to try a valve swap on my EVO iii. It may sort out the close but no cigar sound the head currently produces.

[NancyJohnson]

[quote name='2elliot' timestamp='1456000489' post='2984492']
That sounds interesting. I may have to try a valve swap on my EVO iii. It may sort out the close but no cigar sound the head currently produces.
[/quote]

One thing you need to bear in mind is this is a bit of experimentation on my part; I've been too reliant on the Sansamps (in various guises, into the effects return) and reached a point where I just wanted to try something else out. Ultimately (as posted elsewhere), I'll probably end up with an Orange OB-1 500/Korg DTR (or Pitchblack) in a 3U rack as an alternative.