JTM45 first build

[MBD115]

A month or so ago you guys helped me decide to build a Metro JTM45 kit so here it is. Working like a charm. Piece of cake ( )

It took me over 2 weeks working about 2-3 hours each evening to complete. The first startup went off good and it sounds great.

Thanks for your help. I love my new amp!!!!

[M Fowler]

Looks good to me now your hooked buddy.

Mark

[Jana]

Nice build. Especially nice for a first-timer.


Just a minor suggestion, I would change the orientation of a couple of your Sozo caps. Referring to the bottom picture, starting from the left, the first cap should have the band towards to tubes. Then caps 5 and 6, the .022 and .1 in the phase, they should have their bands down towards the controls.

Reason? The band is the outer foil connection, this should be connected to the lower impedance side of the circuit for better noise shielding.

It will work fine the way you have it and no harm will come. But, being totally anal about these things like I am, I would change them. Any normal and sane person would probably leave it alone and call it done.

But like I said, nice build.

[Cygnus X1]

Looks great!


Just how much gain does a JTM45 have?

[MBD115]

Looks good to me now your hooked buddy.

Mark

Addicted = yes

I work a tough job but I still found the time to work on my amp build every evening and I loved it. I know I made several mistakes, some of which I caught and fixed, some as Jana points out I need to do (and I will - I promise Jana) but I still had fun building it. And the smile it puts on my face when I play it is priceless man (the wife is getting tired of saying, "Yes dear, it sounds real good")

I do think I have a problem though. When I turn it on and let it warm up then switch it off Standby I can hear the caps charge though the speaker. I've tried tuning the volumes down but that doesn't change it. Once I come off standby for the first time I don't hear it after than when switching back to then off of Standby. Is this normal for these amps or is this something I have wired up wrong? Everything looks like the Metro layout and instructions but I can't find anything on their forum about it.

Again, thanks for the replies to my post and also for all the friendship I have found here!!!!!

D

[MBD115]

Looks great!


Just how much gain does a JTM45 have?

I'm not a good one to answer that question because I'm still trying to figure that out for myself. I have found it has a lot of clean headroom and is probably the most responsive amp I've ever played (response to pick pressure and guitar volume, pickup height, etc). I can hear the harmonics in there and they are out of this world. I've tried cranking it up but after about 5 its so loud I can't take it up higher. I had it on 10 this weekend (at home in my music room) and it was hurting my chest and my ears. Hay, its very loud!!!!

I'm waiting to go pickup my airbrake parts that are in and will have them this weekend when I get back home. So maybe next week I can answer this question better. I'm working away from home right now and living in a pretty large 5th wheel but if I crank it over about 1 with 1/2 guitar volume you can hear me from the city limits. I don't want run-out of here so I'm trying to mind my manners, but it sounds so good cranked up that is very hard not to do.

I've read that I should use an OD pedal and while shopping for one I just went ahead and ordered this monster

http://guitars.musiciansfriend.com/prod ... sku=150613

And here is a great tube demo of it with a Marshall setup

http://www.youtube.com/watch?v=OeSlnvYPYnU

I will have it week after next (again my week lag time from getting back home and picking up my orders) so I'm hoping with the airbrake, the JTM45, and the RP1000 effects pedalboard Its going to kick some serious arse!! At least I've got my fingers crossed anyway. I had it looped to my SV's effects this weekend and it kicked its butt hands down - with no doubts. If this RP1000 is as good as it sounds on the tube I can bet this 45 is going to be a sweet multi-tone setup for me.

Next - some speakers. I'm thinking a 2x12 G12H30 Avitar cab then maybe replacing one of them with my old broken-in V30 if it helps. I've been using a 112 closed back with a V30 and I also tried it with a G12K100 and an Eminence Ragin Cajin 110. It is making that V30 sound better than I've ever heard it sound before. The K100 was pretty bass heavy and the 10" Eminence sounded ok but was at the bottom of my list so far. I can say a closed back V30 sounds pretty good and full. I like it pretty well as is, but I think the G12H30s would sound better, at least one of them in a mix with the V30 ~~~?

Later guys

[M Fowler]

I find that I can't control the volume changes when switching between effects on those types of pedals so I went back to regular single stomp boxes on my pedal board for live gigs and reserve the fancy pedals for practise or recording only.

In fact I seldom use a pedal and the last two gigs brought them with but did not use them.

Mark

[Structo]

It's funny when you look up the JTM 45 at Schematic Heaven and a Fender Bassman shows up.

Yep, Jim Marshall copied the 5F6 Bassman for his first amp.

I'm not saying his sounded exactly the same as the Fender due to component choices and what was available to him.

The first JTM 45/100 was an interesting beast because I believe that Pete Townshend told Jim he liked the 45 but needed much more power than the 45 was putting out.
So Marshall doubled the output tubes (6L6's) but there were no 100 watt output transformers at the time so he installed two RS OT's for a short while.
Thus the Super Amplifier was born.
Starting around 1965, I think they went with the larger single Drake 100 watt OT
I think the fact that the amp used a cathode follower type tone stack which was used on a lot of later Marshall amps was a defining moment for the classic Marshall tone a lot of guys love.

And as they say, the rest was history.

I'm sure someone will correct me if I have any of that wrong.

[Firestorm]

The early history of Marshall is funny (in a charming sort of way). The first amps were such direct copies of the 5F6A that the controls were backwards (because Fender had the tubes hanging and Marshall had the tubes up). There's no European equivalent of a 12AY7, so Ken Bran used ECC83s, essentially doubling gain (and then some). The earliest transformers were surplus so two early JTM45s could sound totally different. 6L6s were way expensive in the UK, so they went to Genelex KT66s (imagine KT66s being cheap!) and then to EL34s when Mullard introduced them. The feedback on a 5F6A assumes a 2 ohm load, while Marshalls could be 4, 8 or 16. Over the years, they moved that tap around, sometimes changing the feedback resistor, sometimes not.

If you like old Marshalls, Michael Doyle's book is a must have. Great stories, lots of schematics, Ken Bran's recollections of his first circuit tweaks. Great stuff.

[mcrracer]

I find that I can't control the volume changes when switching between effects on those types of pedals so I went back to regular single stomp boxes on my pedal board for live gigs and reserve the fancy pedals for practise or recording only.

In fact I seldom use a pedal and the last two gigs brought them with but did not use them.

Mark

Pedals??? We don't need no stinkin pedals!!!!! We got TUBE AMPS!!!! Leave the pedals for the silly cone crowd!!!

[M Fowler]

Mcrracer,

I agree and I have been trying to keep away from using pedals lot faster setup and tear down.

Mark

[MBD115]

I just wanted to post a little follow up. I've been trying out my new pedal-board since Sunday evening, http://guitars.musiciansfriend.com/prod ... sku=150613 and I must say I find it quite amazing. I haven't went completely through all the presets or options it offers yet but of the many I have tried I have found several that will be very useful. I do find the Harmony function a little lacking as of yet though, but most others seem to work as expected. I find the Fender Rev and Fender Twin models really sound nice through this amp.

My new JTM45 sure sounds sweet and this new pedal board, IMHO, does add to its tone. I am considering getting an Avatar 2x12 closed back cab loaded with a Hellatone V30 and a Hellatone H30. My old 112 closed back V30 cab is sounding so sweet is why I'm considering this pair. Using the modeling pedal and the 45 I believe this would make a pretty nice setup for me. ~~~?

Later guys

[KT66]

Congradulations on your new amp, it looks great. As Mark said, you are hooked now weather you like it or not! Ha ha. So, here is a mod idea for you that I think you would like : Put a switch on the rear panel so that you can sepearate the cathodes of V1 and put one onto a 2.7K/.68U combo like later JMPs had. If you jumper the channels with this configuration, it's kind of like an active tone-stack, and to me IS the sound of rock. Of course, to make this complete you would need a switch to change the bright channel blocking cap to a .0022U, or you could just use a 3PDT switch. If you don't have a poweer attenuator and don't have the opportunity to dime your amp you might want to try a PPIMV, like the Ken Fischer type 2, or even a crossline. Again, great looking amp. Of course, you could also put a switch in to add a cathode cap to V2. Most Marshalls that did this had a .68U, but some had a big one like a 330U? If you used a SPDT on-off-on you could have both.

[MBD115]

Thanks KT66, and yes I am hooked. There is something about building your own amp that I don't think I can explain.

I have been playing it every day for at least 2 hours and I love the tone. I've been experimenting with my new stomp and trying some reverb, delay, etc, effects and all I can say is 'WOW'!!!! This 45 has some tone man and I love it.