400+ Users - Preamp Tube Mod

[tayste_2000]

Going to try this week the 12AU7 mod, apparently according to people on Talkbass it's less of a mod and more of a correction, removing a bottle neck from the design of the amp, giving it more headroom, more responsive volume controls and a more responsive mid control.

All you do is swap the 12AX7 in the drive section out for a 12AU7

I've just been finding with my 4x10 which due to being ported is a bit aggressive sounding, I'd almost go as far as saying angry that I can't get the 400+ past 3 with out it sounding overdriven. Also the 400+ is just not powering my Strategy 400 well (either of them) so this might fix all that.

So I thought I'd start a thread since there are 2 new 400+ owners this week I shall post my results and you can decide if you want to give it a go.

Cheers

[The Funk]

I've heard about people doing this in other amps as well. I wish I knew more about how this all works.

[onehappybunny]

[quote name='tayste_2000' post='605702' date='Sep 22 2009, 03:48 PM']Going to try this week the 12AU7 mod, apparently according to people on Talkbass it's less of a mod and more of a correction, removing a bottle neck from the design of the amp, giving it more headroom, more responsive volume controls and a more responsive mid control.[/quote]

fwiw Mark's new Mesa already has a Mullard 12AT7 in the drive position. I think it makes a great difference and made the EQ much more responsive. Good luck and look forward to hearing how you get on

[tayste_2000]

Damn will have to work it the other way round and ask him what he thinks, that's the second time an AT has been recommended over the AU

[Monz]

What you need is a decent valve amp

[onehappybunny]

[quote name='tayste_2000' post='606181' date='Sep 22 2009, 10:17 PM']Damn will have to work it the other way round and ask him what he thinks, that's the second time an AT has been recommended over the AU[/quote]

I went with an 12AT7 because I wanted a Mullard (from reviews on Finnbass) and that seemed the best mix of availability, price, quality and reduced gain level. Go with what you think is right - what works for my ears may not for you

[tayste_2000]

I have 6

[tayste_2000]

[quote name='onehappybunny' post='606208' date='Sep 22 2009, 10:39 PM']I went with an 12AT7 because I wanted a Mullard (from reviews on Finnbass) and that seemed the best mix of availability, price, quality and reduced gain level. Go with what you think is right - what works for my ears may not for you[/quote]

Yeah I'm going to borrow some from my tech and then buy like a £30 military spec one when I decide on the type.

[Monz]

[quote name='tayste_2000' post='606210' date='Sep 22 2009, 10:40 PM']I have 6 [/quote]

Smart arse

[stunbass]

Hi, which valve is the driver?... I run a 400+ and would be interested in trying this.

[tayste_2000]

I'm trying to get a picture with an arrow

As I don't know either....... yet

[tayste_2000]

The one closest to the power/standby switches apparently

But the more I research into it, with it being a lower gain all it's doing is giving you the same 400+ sound but neutering the amp so what I get at Master vol 3 I would then get at like 6-7 so I have more usable clean tones inbetween, but I have my volume at 3+ for a reason.

Hmmm no so sure about this

[umph]

[quote name='onehappybunny' post='605807' date='Sep 22 2009, 04:54 PM']fwiw Mark's new Mesa already has a Mullard 12AT7 in the drive position. I think it makes a great difference and made the EQ much more responsive. Good luck and look forward to hearing how you get on [/quote]
+1 on 12at7 type gain valves for drivers

[umph]

[quote name='tayste_2000' post='606463' date='Sep 23 2009, 10:22 AM']The one closest to the power/standby switches apparently

But the more I research into it, with it being a lower gain all it's doing is giving you the same 400+ sound but neutering the amp so what I get at Master vol 3 I would then get at like 6-7 so I have more usable clean tones inbetween, but I have my volume at 3+ for a reason.

Hmmm no so sure about this[/quote]
if you want more clean i'd recomend running 6550s(or kt88s if you actually wanna hit the 300watts) in it so it'll actually around 300watts as apposed to 180.

Edited September 23, 2009 by umph

[tayste_2000]

There is no way on earth the 400+ is only putting out 180w

As for filling it with KT88's essentially all your saying is buy a new amp.

[Guest johnzgerman]

[quote name='tayste_2000' post='606613' date='Sep 23 2009, 12:44 PM']There is no way on earth the 400+ is only putting out 180w

As for filling it with KT88's essentially all your saying is buy a new amp.[/quote]

that would depend on what impedance cab you are running it through

[tayste_2000]

[quote name='johnzgerman' post='606621' date='Sep 23 2009, 12:56 PM']that would depend on what impedance cab you are running it through[/quote]

I didn't think the wattage changed on tube amps depending on impedance, I know it certainly doesn't halve like solid state amps do.

[Guest johnzgerman]

[quote name='tayste_2000' post='606622' date='Sep 23 2009, 01:02 PM']I didn't think the wattage changed on tube amps depending on impedance, I know it certainly doesn't halve like solid state amps do.[/quote]

i think you might be right, ive just read something about that somewhere else:)

[Monz]

My amp puts out 200W clean into 4 and 8ohms not at the same though obv.

[umph]

[quote name='tayste_2000' post='606613' date='Sep 23 2009, 12:44 PM']There is no way on earth the 400+ is only putting out 180w

As for filling it with KT88's essentially all your saying is buy a new amp.[/quote]
edit;

sorry didn't realise how different 400's and 400+'s were. Don't put 6550s or kt88s in your 400+ or it'll explode and yes it wont be doing 180 it'll probably be doing somewhere around 300 - 360watts!

Edited September 23, 2009 by umph

[tayste_2000]

Apart from there are 12 in the 400+

[ped]

Lol ownage

[umph]

[quote name='ped' post='607110' date='Sep 23 2009, 09:14 PM']Lol ownage[/quote]
aye i feel like a chuff now ;o