Another JTM 45 Build

[tonelator]

Hi everyone , new member here what a great forum with very helpful people, most of my questions have been answered from reading the posts I'm sure I''l have a few in the future .
I have done two amp builds a ceriatone ods ford 50 w special and a HRM 100 w Bluesmaster which i sourced all the parts for the build,it certainly put a strain on the old grey matter putting the BOM together and ordering the parts. Makes me appreciate the Valve Storm site , I haven't finished the HRM yet but i am plotting [ showing signs of addictive behaviour ] to build the Metro jtm 45 everything i read is good and the instructions are a bonus.
I'll be ordering the iron from classic tone and the rest of the parts from Valve Storm minus the chassis as i make my own a couple of mates in the sign making trade are going make me the faceplates and it will save a few $'s on shipping to Oz.
I'm thinking of ordering the Sozo,s and the Allen Bradley resistor option, from what i read the stock caps and resistors are fine as well, plenty of pro's and con's here about the subject if anyone would like to chime in it would be appreciated but i guess the topic has been fairly well covered .

[Elad E]

hey,
first of all - good luck with the build, mine was the first and only (for now) amp I've built and it was a fun ride and went down quite smoothly considering the number of variables that could have gone wrong

I also got the Classic Tone iron, Sozo hand wound vintage caps and AB carbon comp resistors. I just recently switched the silver mica mixer caps which came in the ValveStorm caps kit with Lemco silver mica caps in the bright and normal channel (440 and 270 pF respectively instead of the 500/250).

I'm quite anal about tone and I knew I would eventually opt to get the Sozos and Allen Bradleys anyway so getting them right from the get go was actually the cheaper more reasonable way around.
I can't really tell you whether these components make a difference or not or whether it's a difference you'll prefer or care about but I'm pretty sure the affect of NOS and/or vintage correct components is of a culminating nature so I would stick with as much closest to vintage spec components as financially possible.

also take notice that the amp (at least mine) took some 60-90 hours of play time to reach the point where it sounds as good as it does now. I also suspect running it on 2-4 on both volumes isn't doing much in terms of burning the amp in as the biggest improvement happened after around 9-12 hours, total, of running it on standby with no power tubes, both volumes dimed and playing the Led Zep discography from my iPhone into the bright channel.

[tonelator]

Thanks for the reply Elad i'm going to take your advice on board and go the extra yard with the A/B's and Sozzo's, no point in doing it later when the amp is finished.
I'm really looking forward to the build it should compliment the other two dumble amps ' what is a man without a marshall '
Anyway i hope they sound good together, the neighbours are going to love me !
Tone is what it is all about i'm 100% with you on that subject.
What kind of change do the lemco caps make tone wise, i still have a lot to learn.
I need to break in my other amp so i'll take your advice on that one as well. the only change i'll make is to run a few drawn out live performances of dazed and confused
I didn't know you could load the amp without the tubes for the burn in.
Thinking about the master volume mod as well, for the few extra bucks why not.

[Elad E]

frankly I can't tell you what changes the Lemco caps made but I know they were standard for mixer caps on original Plexis. when I played the amp for the first time after putting them in I got more hum than usual which gradually died down after around 10-15 minutes of playing. at first it sounded like the amp became even more responsive to playing dynamics but today I played it again and felt the amp became a little harsher, like it was before the break in, so I'm going to give them some play time before I can conclude their full affect on overall tone (if at all), I guess they may need their own burning in period.

regarding the master volume mod - I was kin on keeping it as close to the original design as possible and take it from there if I didn't like what I heard so eventually I didn't implement it into my amp (I also heard it wears power tubes faster though that shouldn't be a factor if you need the cranked up sound at bedroom volume levels).

I followed George's advice from an old forum post about taking the power tubes out when burning in. the pros are you don't wear the power tubes. here's the link: http://forum.metroamp.com/viewtopic.php?t=2395" onclick="window.open(this.href);return false;

just remember to never run the amp with power tubes in and standby on without a speaker or a dummy load connected to the amps' output jack.

btw, how are you liking the Ceriatone Dumble clones? I'd love to build an OTS or HRM in the future...

[neikeel]

regarding the master volume mod - I was kin on keeping it as close to the original design as possible and take it from there if I didn't like what I heard so eventually I didn't implement it into my amp (I also heard it wears power tubes faster though that shouldn't be a factor if you need the cranked up sound at bedroom volume levels).

Neither of the MV types used here wear your power tubes out. Hammering a cranked amp into an attenuator does that.
You drive the PI harder with PPIMV so you need a good PI tube for that version. The Marshall style pre-PI MV uses V1 and V2 gain mainly, can sound good can sound fizzy if you rely on it.

The burn in method suggested is ok for the preamp components but you need signal in the OT to burn that in properly. I have never done it myself - just plug and play so cannot comment on the relative merits.

Worrying earl ysigns of addictive am building behaviour

[tonelator]

Finally ordered the jtm45 kit from Valve Storm and parts for an 18 watt build [ couldn't help it your honour ! ] a very handy place to find most of your parts, helps with the postage over to Australia . Decided to go with the Mallory 150's I'll try out the sozzo,s further down the road i did order the Allen Bradley's as a compromise. The transformers are on hold for the moment as i have found quite a few reels of enamelled copper wire !

[tonelator]

Elad I built a 2x12 dumble cabinet for the OTS but haven't taken it through it's paces yet i'll give you my take on it when i get home. [been away a long time]