Another JTM45 Build

[joeboo88]

Hi, I just finished this last week.
This is my last "ugly derelict barn door" chassis. ( I made an attempt of an Express last month)
I have learned so much, studying other builds and I enjoy just reading alot of the threads trying to figure out the language you all speak.
I took all that I learned so far from here and tried to implement it into this build.
I only made 3 small booboos building this and had them solved before I fired it up. When I fired it up i almost cried.....Wow this thing sounds sweet.
The Bass is what I had been looking for in an amp.
I used some 6l6's and a 5ar4 and and old Sylvania and NEC 12ax7's and a Shangwang (or what ever their callled...lol)

I employed the "Larry Grounding scheme" and with my Les Paul plugged in there is no noise, but when I plug my Tele and Strat in I hear some hiss...weird, Its probably the pickups?

Its ugly but it sounds so nice, I'm amazed with this one and I thank you all for teaching me so much.....and how helpful you guys are,thanks Mark Fowler

Next build will be either a Rocket or a Liverpool ( I like the SS rectifier sound, so probably a 2xel84 LP), I have the iron and parts, but need to get a chassis, I dont think my dad-in-law has anymore junk chassis's he wants to part with. Plus you probably dont want to see another build like this.
The Canadian buck is only worth about 20 cents to the American dough, so I'll have to wait, but there is a guy just North of my Igloo would can probably make me a chassis for 70 Canadian.

Try not to laugh too much, cheers.

[deeder]

Waou! This chassis is ugly to one's liking, but I love it.

About the noise with your axes, maybe you can try a star grounding, it works well with my Strats. This issue isn't coming from PU's.

Congrats for your build

[M Fowler]

Glad you got your amp together and are enjoying it.

Some guitars need help in the noise department.

[joeboo88]

Thanks guys, actually sitting in front of my speaker the single coils hiss, move away and all is quiet. Boy this amp is nice sounding. Now onto building a 2 hole rocket, from Mark's layout. how come we are never happy with what we got. Cheers brothers.

[JoeCon]

Joe

Once you build the Rocket you're gonna wanna try a Rockster build too!!
Don't ask me how I know...LOL

I plugged into the Rocket yesterday after using my Pool for a while and wow what a nice amp....you're gonna like it!

[joeboo88]

Thanks, Joe. I have all the parts for the Rocket, except the chassis....I'm in no hurry as this thing sounds so good....
I'm a pedal builder but I like this thing with only one of my home made Tonebender or homemade fuzz face..(building these things with finding the proper GE trannies was worse than building an amp, lots of hair pulling.

So the other distortion pedals just sit there, and I'm glad because I started building pedals to make up for what solid state amps couldnt do.

[JoeCon]

There is a Rocket chassis in the For Sale section right now.

I did just the opposite and built a few amps first and now have built some pedals. The Rocket works really well with them also. I've tried a Tonebender and Zen drive so far.

Also on my Rocket others here suggested a three position switch for the bypass caps on V1a, so I went with UP = 1uF, CENTER = none, and DOWN with a 10uF cap. Gives nice boost to the amp or lets you clean it up some.

Enjoy!

[lumox0013]

I do love this type of build.( saving money makes me happy )it looks good and if it sounds great thats the most important part , for sure. cheers

[Littlewyan]

I think it looks great, its got character!

[joeboo88]

Hey thanks for the kind words guys. I haven't been here much lately,my daughter had a baby girl,Emily, on St.Patty's day.
I'm a GRANDPA!!!! she is way cool....
This amp still sounds great, can't crank it much, will have to
Wait a bit. Thanks to you guys, talking about chassis builders, I found one up here in Canada. Our dollar isn't worth much, so I lucked out and only paid 88 bucks for 2chassis's including shipping. I will be taking my "ugly express" apart and housing it in a proper chassis when it comes, I will leave this JTM alone, as I like how it looks....again thanks guys.

[Littlewyan]

Congrats on becoming a grandad!

[joeboo88]

Hi: I have been reading Littlewyan's build thread. Good luck on your build, sir.
https://tubeamparchive.com/viewtopic.php?t=26720

there is a youtube link on the first page in that thread, the beginning of the video sounds just like mine does. But then at 2minutes on the video the
JTM45 cranks out while he is playing the raunchier stuff like AC/DC and that amp has this crunch/distortion…. my amp doesn’t do that?
He said he didn’t use pedals on the video, so I was wondering what the heck is wrong with my build.....
Unless he is lying…LOL, does anyone have a JTM45 and can say if yeah mine sounds like that too, then I have to figure what I did wrong.
My amp sounds great and I have all the proper voltages and is biased correctly for my 6l6's and I run the amp through a 25 watt greenback speaker, but I don’t have that much gain as his. My amp is nice and loud, and I love the bass, which I jump the channels and turn the bass way down
I went through my layout and it is correct as far as I can tell, but looking at different schematics and layouts, I see some things I don’t have.

1 – I don’t have a 220k resistor between the 2 poles on the 32uf/32uf cap can, that I saw on a Ceriatone layout…..what is the purpose of that resistor?

2- Pin 5 on the output tubes (again Ceriatone layout) each has a 5.6k resistor running to the 220/220k resistors, whereas my layout I used (triode) doesn’t use these 2 resistors
Both layouts are for KT66’s, what’s the purpose of those resistors? Would my 6l6’s need this too?

Also if I wanted to use EL34’s should I replace the 470ohm resistors which go to pin4 and 6 on the output tubes with 1K resistors that I have read about, I know the OT for a EL34 is 3.4k – and I have a 7.6K OT in my build, so I would have to use the 16ohm selection for my 8ohm speaker…..is this a good idea?

I realize I’m sounding like a windbag here, but any answers would be greatly appreciated.
Cheers guys

[Littlewyan]

The amp in that video is running a stock Marshall reissue PT and OT. So the voltages are quite low, with KT66s he will be seeing about 390VDC on the plates. Thats why the amp sounds quite mushy and breaks up easily (and is actually not the sound I want anymore tbh). I suspect you're running correct voltages in your amp so you have about 450VDC on the plates and I think 6L6s have a bit more headroom than KT66s anyway.

For more gain try jumping the channels, running bass at 0, treble at 8, middle at 10, presence at 8, high treble at 10 and normal at 5. Also what guitar are you using and what pickups?

https://www.youtube.com/watch?v=oWnZln1-qbk

This is a better example of a JTM45, notice how it has more clarity and sharpness when hes hitting open chords at the start?

1. The 220K is a bleeder resistor, this will drain the capacitors for you when you turn the amp off, its not a necessity it just means you don't have to do it when you work on the amp. Obviously still check to ensure the voltage has drained before working on it!

2. Those are grid stoppers, they are used to prevent oscillations and can prevent blocking distortion. Add them if you wish, you shouldn't in theory notice any difference unless you are getting blocking distortion or oscillation issues at the moment.

If you have the 1K flying resistor just before the 470R screen grid resistors then you might be ok with EL34s. Perhaps change the 470Rs to 1Ks just in case. With regards to the OT yes mismatch your load by running a 8ohm speaker/cab into the amp with the selector on 16ohms.

[joeboo88]

Hey thanks for all the answers Littlewyan

I believe we have the same Les Paul.Classic, also I have a tele and a
mexi-strat

my volatges are just shy of 450vdc

thats funny i was just listening to that you tube video while reading your reply.....

what tubes are you going to use on your build?

You guys on this site are awesome

[Littlewyan]

Ah well you shouldn't have any trouble getting decent gain with the LP Classic.

I might go for 6V6s first to try and keep the volume under control a bit more. Although it will only bring the wattage down to about 22W which is still pretty dam loud! So may just go straight for the KT66s and MAYBE fit a PPIMV.

Let us know how you get on with those settings on your amp.