# How to warm up an 18 watt Marshall



## JHarasym (Mar 27, 2007)

I have a Trinity 18 watt Marshall clone that's a little harsh sounding to my ear.
Where should I start to try to warm up the sound? 
Different tube in V1 (5751 or 12AT7)? 
Or am I peeing on the wrong fire hydrant? 
Suggestions?


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## TWRC (Apr 22, 2011)

I have an 18 Watt clone as well and I run mine pretty much full out with an attenuator. Personally, I love the 12AX7's in there, so I have no need to put a tube with less gain properties. However, the one thing that I did notice that made a huge difference in mine was the speaker. I have a vintage creamback in mine now (which came with the amp) but have tried a greenback, V30 and Weber silver bell and the creamback made the amp much more responsive, warmer and smoother to my ears. 

What speaker do you have in yours?


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## greco (Jul 15, 2007)

I have a 1 x 12" cab with a Cannabis Rex (hemp cone) that you could borrow and try... if the tube change "hydrant" doesn't work. 

Cheers

Dave


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## PulienJier (Dec 5, 2014)

As far as I know, putting an 12AT7 will reduce the bass, make you sound harsher (at least it's what it did in my Traynor Yba-1a and I like it).
How long have you had this amp? Maybe it's just the speaker that needs some time to break up.
Maybe change your tube for a different company?


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## Stratin2traynor (Sep 27, 2006)

I have a Greenback in mine. Works equally well with a WGS Reaper. I like running mine hot with an attenuator. Tonal bliss. My tube compliment is TungSols in the preamp (12ax7) and JJ power section. Best amp ever for that Marshall Plexi sound. Love it.


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## sj250 (Oct 26, 2010)

I have to agree completely with all the speaker suggestions but to take it one step further the speaker cab itself can also have just as much if not more impact. I have a 2x12 I bought that sounds lifeless, dull and flat with very little bottom end no matter the speakers or amp and then my favorite 1x12 sounds incredible with almost every speaker and all 5 amps I've run through it so far.


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## gtone (Nov 1, 2009)

What have you been running in V1 and V2 so far? What cab/speaker config are you using? What kind of guitar/pu's?


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## greco (Jul 15, 2007)

sj250 said:


> I have to agree completely with all the speaker suggestions but to take it one step further the speaker cab itself can also have just as much if not more impact. I have a 2x12 I bought that sounds lifeless, dull and flat with very little bottom end no matter the speakers or amp and then my favourite 1x12 sounds incredible with almost every speaker and all 5 amps I've run through it so far.


Not wishing to derail the thread, but don't you wish you could determine why one cab will sound better no matter which speaker(s) or amp(s). 

Cheers

Dave


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## copperhead (May 24, 2006)

What settings do you use ? & what tones are you after 
& what are your channels ...plexi channel & 1974x channel ? without the tremolo ..& is there a vrm.....or master volume 
I run mine on the tbm channek 
Max gain 
bass on 0 to 3 
mid on 7 
treble on 8 
gain almost maxed ,vol almost maxed


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## parkhead (Aug 14, 2009)

sj250 said:


> I have to agree completely with all the speaker suggestions but to take it one step further the speaker cab itself can also have just as much if not more impact. I have a 2x12 I bought that sounds lifeless, dull and flat with very little bottom end no matter the speakers or amp and then my favorite 1x12 sounds incredible with almost every speaker and all 5 amps I've run through it so far.


not to derail the thread here but this 2-12 problem is caused by two out of phase speakers...period 
do not pass go ... do not collect $200 


is there one channel you don't like or both ? 

check the amp for the following 
is the filter cap that feeds the screens 16mfd or is it a higher value ? to much screen filtering makes an amp more aggressive in the transients and piercing 
check the choke/screen resistor the marshall schematic calls for 1.5k* shifting it up to 3-5 k would warm things up considerably 
the screen resistor has a similar effect so a larger resistor makes the power amp slower on transients 
* while the original schematic may call for particular values a different (ie modern) power transformer will alter (increase) the available current possibly necessitating a change in screen cap and choke resistor 
to recover the original sound 
most modern clone power transformers have extra current capacity so they are less stressed maintaining voltages ... this changes the SAG characteristics through the entire amp 

find the pull down caps in the tone networks one channel uses .01 the other channel .0047 
#1 make sure neither of these is a disc cap 
#2 consider doubling their values ie .01 becomes .02 and .0047 becomes .01 
#3 if possible use a vintage cap in these positions or a russian PIO for these spots 

disc caps sound harsh because they are more efficient at higher frequencies 
so as you rotate the tone control you are cutting too much or not enough
they act like an on off switch, they are too peaky in either tonal direction 

doubling the value will darken and clean up the eq sweep of the tone network
the larger cap value will pull out more midrange during its sweep providing better cleans 

conversely if you want more dirt and mids lowering the bass cap value will provide this effect

using a PIO type cap works the opposite of the disc cap the pio cap has decreasing efficiency at higher frequencies 
so there is more of a rainbow of tonal colors as you sweep the control (this is why les paul guys swear by them in their guitars) 

these tweaks should warm up the amp 

p


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## High/Deaf (Aug 19, 2009)

parkhead said:


> not to derail the thread here but this 2-12 problem is caused by two out of phase speakers...period
> do not pass go ... do not collect $200


+1 

I put together a 212 from an old 412 cut in half (the 'owner/cutter' kept the better half, I had the one that need the major cosmetics) and, although the speakers were wired in phase as per the colored marks on the drivers, the were not acoustically in phase. I had to wire them 'incorrectly' according to the red dots on the devices. Sounded pretty good after that. 

That one device labelled and wired wrong may explain why the 412 wasn't loved by the original owner. Don't want to say who made the box but they are currently moving production from NA to Asia and that's peaving some people off.


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## JHarasym (Mar 27, 2007)

Thanks for all the input.
The amp is a 1x12 combo with a Celestion Rola G12H 30 watt speaker. 
I have a few other speakers around I'll try out before exploring the circuit.
I don't have a particular sound in mind. I usually prefer an amp with a bit of versatility as I end up playing a variety of music.
Will let you know how I make out.


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## Roryfan (Apr 19, 2010)

JHarasym said:


> Thanks for all the input.
> The amp is a 1x12 combo with a Celestion Rola G12H 30 watt speaker.
> I have a few other speakers around I'll try out before exploring the circuit.
> I don't have a particular sound in mind. I usually prefer an amp with a bit of versatility as I end up playing a variety of music.
> Will let you know how I make out.


Let us know how you make out, but a G12H30 is actually a great speaker for that amp. You may have hit the nail on the head when you said you want something versatile, 18 watters tend to be a one-trick pony. Oh, but what a trick!

P.S. Just noticed that we're neighbours. I'm also an 18W owner/fan (Newall clone & '69 JMP head) PM me if you want to meet up for a little A/B session sometime.


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## gtone (Nov 1, 2009)

I concur with Roryfan - many of the vintage Marshall circuits are one (or two) trick ponies. IME, they tend to smooth out as soon as you get the power tubes cooking - guess it's the natural compression that smoothes out the signal. If that's the case with yours, it may just be that you need to crank it up loud enough to get that happening. An attenuator may help if your situation doesn't allow for the volume levels that will result.

I used a Phaez Brink attenuator that worked brilliantly with my old '70 JMP 50W head. The combination of passive load/impedance mismatch that it uses for attenuation was good for knocking off about 6 db without choking off the tone like some others I tried. Great value too at $79 - hard to go too wrong there...

Also found that Fender single coils sounded brutally shrill/harsh thru my JMP - def got smoother and throatier with hum buckers, P90's or even mini HB's.


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## nonreverb (Sep 19, 2006)

The G12H30 is indeed a good speaker. However, it needs to be broken in. Speakers out of the box or even recently out of the box do not sound than same as when they've been played regularly for a couple of months. The compliance will change and hence the tone will change as well.



Roryfan said:


> Let us know how you make out, but a G12H30 is actually a great speaker for that amp. You may have hit the nail on the head when you said you want something versatile, 18 watters tend to be a one-trick pony. Oh, but what a trick!
> 
> P.S. Just noticed that we're neighbours. I'm also an 18W owner/fan (Newall clone & '69 JMP head) PM me if you want to meet up for a little A/B session sometime.


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## Steadfastly (Nov 14, 2008)

How warm did you want it?


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## sj250 (Oct 26, 2010)

parkhead said:


> not to derail the thread here but this 2-12 problem is caused by two out of phase speakers...period
> do not pass go ... do not collect $200
> 
> p


Sorry for the late reply but I just saw your response. I will reverse the wiring on one speaker and see what happens. Thanks for the heads up


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