Jtm 45/100 upgrade advice please....

[StuartC]

Hi, new here!

Just bought myself a Ceriatone JTM45/100 amp which is great, but after reading various posts on here I thought I might try to upgrade some components.
Other than valves, where should I start to make it even better sounding? Sozo caps?

Any opinions welcome!!!

[neikeel]

The components on a Ceriatone amp are pretty good. Tweaking it for better components will not necessarily yield a lot of bang for your buck.
Usually some decent valves really deliver best value, IMO.
May I suggest some NOS preamp valves (or good tested, guaranteed 'pulls').
I generally use Mullards but Telefunken, GE and others are really popular too.
For me the Gold Lion KT66s are excellent subs for GEC KT66s (I have x4 in my 45/100, x2 in my JTM45 and 2 spares waiting for an original JTM45 when I find one I can afford!) the Gold Lions I have used/installed for people really are excellent.
If you want more smoothness then phillips mustard caps do help and the sozos (I am lead to believe) are a good substitiute. I tried some in an early build and did not really rate them (although I did not wait for them to break in!) and replaced with mustards. You can get 18nF 400v mustards at reasonable prices. After that you are looking at OT replacement and/or filter caps and resistors which is fun if you want to play but not a great way to spend lots of $ or £ wherever you happen to be.
Having a sound in your head and knowing where you are now in relationship to that tone helps (as does a really good set of speakers, like some original Celestion pre rolas or broken in Heritage 20s, or if in the US some Scumbacks).
Oh and welcome

Edited for typos!

[Coot Boy]

I have a Ceriatone 45/100, I took all the CC resistors out and put in CFs. I have old pre tubes and shuggy power tubes, as Neil says, the amp is pretty good from the start. I put the sozos in and I put a Marstran OT in. I must say, I didn't hear any improvement with the OT swap. All things considered, again as Neil said, speakers make the biggest difference, with any amp really. I took to mine with the iron when I was pretty green and was going through the mod stage as a journey of discovery. These days I leave my Marshall circuits pretty much stock, I see nothing wrong with the Mallory 150 caps either and actually built a JTM45 for a friend and used the Mallories and thought that amp had something my 45 with sozos didn't and that amp also had a Ceriatone OT from when I "upgraded" mine. In the end, there's only one way to find out what's what and that's to just do it. The search for better tone will force you into it unfortunately

[StuartC]

Thanks for the replies!

I've only had the chance to plug it in once so far which is really frustrating!!

Had a look inside and noticed the pre-amp valves were a mixed bag- V1 was a Electro Harmonics 12AY7, V2 a JJ 12AX7, and V3 a Groove Tubes 12AX7r. I've left the JJ in there as I read somewhere on here that they are a good V2 valve, but now have Tung-Sol 12AX7's in V1 and V3, so I shall find out on thursday night how is now sounds! The only other thing I will do when I can is to get my amp building friend to check the bias and adjust if neccessary- I heard that the Shuguangs sound better a bit hotter.
I won't be changing speakers- currently run a 1960B with Vintage 30's split top and bottom for two amps- an AFD100, and now this beauty- they look very cool on top of each other!!

Oh, I'm in Lincolnshire/Cambs UK by the way.

[neikeel]

I may be wrong but I suspect the V30s will sound better with the AFD100 than the 45/100. I ditched my V30s a long, long time ago.
The sweetest singing tones with a 45/100 are prerola 20watters, next best thing would be a pair of 65s in the other half of your 4x12

[StuartC]

65's?

Excuse my lack of knowledge, but what exact speakers are they ?

[neikeel]

Hi these are the 65w rated G12M speakers. IIRC introduced in late 70s as high power greenback equivalents. Not quite as sensitive as the V30s or (97db vs 100db) as spiky and in your face, IMO.
They are smoother and less modern than either the G12-T-75 or the V30s and two will handle a 45/100 pretty well. Marshall used them in a lot of their 2x12 combos in the 1980s so they are around and available.
The lead ones which are preferred were stamped 3120 these have the 1777 lead cone. There others with 444 cone which are ok but a bit darker.
These speakers need to be pushed a little to sound their best IMO and the 80 odd watts of a 45/100 can do that.
If you like the tone of the amp with V30s then great but I think that a higher rated M equivalent sounds better.

BTW did you buy the amp off ebay uk recently from the guy with the sound clips? That amp had a master volume fitted and, if so, that amp already has Marstran transformers

[StuartC]

Yes, that's the one I bought!!!

Thanks for all the info, my first impressions were exactly what you said- a bit spiky.

I'm having a proper gig volume test with it on thurs so will see how the new valves sound in it....

[neikeel]

Yes, that's the one I bought!!!

Thanks for all the info, my first impressions were exactly what you said- a bit spiky.

I'm having a proper gig volume test with it on thurs so will see how the new valves sound in it....

Good, it looked like a neatly put together amp with good iron in it.

I have tried most common speaker combinations and to give you an idea I have kept a 68 pinstripe A cab with 20w G12Ms a 67 pinstripe B cab with 25w G12Hs, a 69 basketweave A cab with 25w G12Ms a 69 baslet weave B with 30w G12Hs and a 4x12 B cab with 65s, plus x4 2x12 combos with Golds, Blues, G12Ms and Hs respectively, a few have come and gone. I like Blackback G12Hs too, particularly for classic rock tones as they cut through the mix in a band really well but unfortunately I have had to trim back in the interest of marital harmony . They are all a matter of taste and I was sceptical about the difference between original G12M20 prerolas and average G12Ms greenbacks from the mid 70s but the difference is very significant for the better. The 65s are a good compromise if you use 2 the way you want to.

[StuartC]

So tonight finally got to play the amp with the correct valves, and at volume ..........holy sh1t!!!! That amp is amazing. Sold my beloved jcm2555 to get it and don't regret it for a second. It has all the tone I could wish for, and cleans up really nicely.
Tried it through a pair of the vintage 30's in my 4 x12 and am stunned frankly. Also very glad I don't need to think about changing speakers or any amp components!!!!
I'll try to post a couple of clips if I can.

I'm a happy man!!!

[StuartC]

Here's a very rough clip of the amp from tonight.

Set up was:

JTM 45/100 into Marshall 1960B 4 x 12 with vintage 30's, just using two speakers @ 8ohms.

Gibson Les Paul Std PLus with SD Alnico 2's Vol 10 Tone 5/6

Settings

Pres: 5 Bass: 0 Mids: 8 Treble: 8 Vol 1: 8 Vol 2: 0 Master Vol: 4.5

Recorded with a SM57plugged into Zoom H4 (mono)

Sorry for the scrappy playing, it was just a last minute thought!!!

[StuartC]

That previous file seems really quiet on my computer, try this instead.....

[Jerry G]

[neikeel]

Nothing wrong with those tones!

Although it sounds you were plugged into Channel II hi input maybe your guitar rolls of a lot of highs at 5/6 on the tone?

[neikeel]

http://www.ebay.co.uk/itm/Marshall-JTM- ... _158wt_958