JCM800 2204 build log! Criticism and feedback welcome!

[Champ_49]

Ok, so here it goes!

My second JCM800 build.  This time I thought I'd make a log like I did with the 5E3 for my records as well as hopefully get some constructive feedback/criticism.

Monday May, 04:  (preliminary tube socket wiring).

Today is the first day.  Finally got my power transformers and OT.  As well as other parts.  This PT has a lot of wires coming out and I already feel intimidated.
I used these 5W mills resistors which are quite expensive but they are really small so I thought I'd use them here.  1W 1ohm resistors from pin 1-8 to ground. 
100K across pins 1-6 and 7 on the preamp.  100pf capacitor on preamp tube on.  I bent pins 4-5 inwards as I have seen Rob Hull use this method on one of his instructional videos.  Really cool guy.

Sorry, if I'm overloading the forum with these logs.  Please let me know if I am posting too much here.

[Champ_49]

Preliminaries for preamp tubes.

[Champ_49]

I am having an issue trying to get a can capacitor to fit inside the chassis.  This is a JTM45 chassis so it doesn't have an extra hole for this.

Would this be an issue?  Having a can capacitor hanging over the PT like this?

[Champ_49]

Tuesday, May 5

Heater wiring finally done.  I feel like this is the hardest part.

Noticed the preamp socket holes are aligned differently on the JTM45.

Thanks for looking.

[Willabe]

Looking good!


         Brad   

[Champ_49]

Thanks Brad. 

The heater wiring was successful this time. This was probably the hardest thing to wire up At least for me.

Only thing I'm a little iffy about is how I mounted the power caps like that. One is hanging right over the power transformer. But I don't think this should cause any issues.  At least for now I hope.

[Willabe]

Heaters are a pain but ya gotta have them. Sometimes they go in 1st, like your build, sometimes they go in last, like in a Fender BF.

That cap should be fine as long as it doesn't get hot. Heat shortens the life of e-caps.


              Brad      

[Champ_49]

Thanks Brad. Supposedly this PT is an upgrade version with "m6 steel" that is supposed to help it run cooler.
Not sure but we'll see.

Also you noted the blackface heater wiring goes in last. Is this because of how they wire it? I notice that they elevate it above the tube sockets instead of running it along the chassis.

[Willabe]

Also you noted the blackface heater wiring goes in last. Is this because of how they wire it? I notice that they elevate it above the tube sockets instead of running it along the chassis.

Yes.

Although some guys still put them in 1st. I find it easier when running heater wires above tube sockets to hook them up last, that way you don't have to work around them while hooking up the other sockets pins.

             
                      Brad         

[Champ_49]

That's true. 

I can see also that elevating it above the sockets means shorter wire. 
Is it also easier to twist it all the way up to the pins?

I read a forum talking about heater wiring awhile back and someone mentioned that the heater wires should be twisted all the way to the pins.  Hence elevating above can help achieve this better?  when I see Marshall wiring they don't even twist the wires along the chassis.  Or they twist them very lightly.  Or not at all. I guess it was a matter of economy.

[sluckey]

I don't twist all the way to the tube. I even have a couple recent builds that I didn't twist at all.

[Willabe]

Like you said companies and other builders have wired up their heaters like you did for many years. And they can/do have a quite amp.

Valve Wizard link below, scroll down for a picture his take on wiring up heaters to socket;

http://www.valvewizard.co.uk/heater.html

I have done it his way but I can't say it made a difference, just trying to nip anything that could be a problem in the bud, good build practice.

Ed posted some pics where he used Teflon wire and ran the wires for pin 9 (on 12 _ _ 7) in between pins 4/5, looked real good. On my next build I'm going to try it.


                      Brad   

[Champ_49]

Yup. I've hears of people who say you t twist them and even twist it up to the pins. I had this though in mind when I first started the heater wiring on my last build. Which I gutted out anyways.

But twisting them up to the pins was a real PITA. add to that you have to try to get the leads into the pins and twisted wires are so much harder. So now I'm not even focusing on twisting them like that. Makes life so much easier. And I didn't notice too much hum or any issue like that so far.  So I guess yeah you don't have to.

[Champ_49]

Yup.  I figure I'm not going to stress to much about that anymore. if marshall did it I'll say I will to lol.

[Willabe]

HBP has said before he thinks that Fender wired up the Tweeds and BF/SF's like they did to because the chassis size/space/layout was different.

Tweeds had the tube sockets closer to their eyelet boards, specifically the grid wires/R's so they pushed the heater wires into the chassis corner away from them. The BF/SF sockets were/are on the same plain of the chassis and are further away from the eyelet board parts/wires.

If you look at some pictures of both types you'll see that if the tweeds were wired with the heater wires above the sockets they would be right above the eyelet board.

OTOH, Victoria tweed amp clones are wired up in a tweed style chassis with their heaters wired up like BF/SF amps and he sells a lot of amps.   


                    Brad         

[sluckey]

Most (if not all) of the original Fender tweeds only ran one wire for the filament string. They used the chassis for the other wire and just soldered a short wire from one filament pin to chassis. I don't recommend doing this but Fender did for about a decade. Then they figured out where the extra hum was coming from.   

Then there are amps that have the sockets oriented in such a way that you just run a straight buss wire along each side of a row of sockets, threading the buss thru the socket pins. Kinda like shish kabobs. That looks neat to me. I've been tempted but just never pulled the trigger yet.

[Champ_49]

For this build I had all those things in mind. Where you elevate the wires above the sockets.  I guess I didn't want the hassle as it was hard to do for me.  I did this before and it looked neat but I thought of it didn't make that much of a difference I'll just do it the way I did.

One thing I did  was run the wire to pin 9 on the very first tubr socket  so that it doesn't loop around but go straight over the tube socket And twisted it to the end.  Since I figured this is where a lot of noise is I did this for the first preamp tube.

[Champ_49]

Yes! I've seen the heater wiring  where they just use straight buss wire right through the socket pins. Looks really nice.  Soldano does it this way.  Definitely looks very optimal in terms of the length of wire used.

It just feels so unconventional maybe it's hard to just go and do it?
I'm wondering if you need a certain kind of tube socket for something like this as well as the orientation.  I think I heard on another forum that you can't just use Beltons for runs like this.

Also saw another guy build a marshall on the net somewhere with straight runs.  but it had insulation.  Unlike the bare buss wire soldano uses. Definitely look real cool though.


Looking at the soldano clones. One thing is for sure. I wouldn't even think of attempting something like this.  Looks really neat but probably really hard to do It right since it is a high gain amp.  Plus I can't read schematics very well. I know I should learn. 


Edit:  nvd. I think soldano uses insulated wires as well as bare for the runs

[Champ_49]

http://www.partsconnexion.com/acme-65007_img.html

found this.  CRYO treated. Didn't know even IEC sockets can be this expensive.

[Champ_49]

I had a quick question about how I should bunch the wires from the filter capacitors.  I am trying to follow this Triode layout.

http://site.triodestore.com/JCM8002204V.2NEWlayout.pdf

Question on the three big cans.......
My question is would there be a potential for some problems like parasitic oscillation.. if I grouped/bunched the wires from the main power capacitor with the wires coming off the screen/phase inverter cap as well as the preamp can capacitor? 

I apologize for such a basic question.  I figure it would be neater if I bunched those all together but of course I don't want to run into problems with the sound because of it.
I am trying to make sure I do the proper lead dress or best I can for this.


Thanks

[alerich]

I built a home brew 2204 with Classic Tone iron a few years ago and man I love it. Those are great transformers and the price just cannot be beat.

[Champ_49]

Yup Alerich.  I really wanted to try this amp with classictone trannys.  I always keep hearing good things about them.

[Champ_49]

Thursday May 7

OK.  This doesn't look like much but it took me forever. 
A couple of hours maybe.

I wired up the power switches, fuses, mains power socket. 
I am usually the type to stick with what I usually use.  Like the wire I always got from tube depot.  This time I decided to try the wires supplied to me from my last kit from Hoffman. 
So I used the 18 awg white and red for the runs to the power switches and fuses.  Man! Looks like I found a new favourite wire.  I was afraid the insulation would strip off the wire but it didn't at all.  Just like the tube depot wires the insulation formed along the wire so no stripping. 

One thing I like about these Alpha wires is the insulation is thick.  More so than the tube depot ones. This meant that when I used my automatic wire stripper the sire didn't nick at all.  The tube depot wires the insulation is a lot thinner and the wire would always and easily nick.   Someone mentioned these are very conservatively rated so I hope I got the gauge right.  And more importantly I hope I got the wiring right.

I will definitely be ordering more of these when I need more wire for the power section. I heated the joints up pretty good and the insulation didn't strip off or really melt off at all.   

[Champ_49]

Monday, may 11.

Ok. The build is starting to get more cluttered now. I was going to group the primary and secondary wires together but decided not to. I think it would be ok but just in case I separated them. Twisted the choke black lead with the OT center tap to the ht fuse.
Twisted the blue and white primaries to pin 3s of the output tubes.  Made sure I followed the color code for the primaries. The phasing should be right.

Still waiting for the 3 Pos switch from digikey to wire the secondaries.

Also did some work on the board. Decided to do the buss ground and diodes. I chose the 5408 larger diodes. unnecessary?  Maybe. But I like the nice thick leads. 

Lastly the input jacks.  This took me awhile. But it should be ok.


Please let me know if you guys see anything off.  Thanks!!

[Champ_49]

Ok! So here it is!  Am very very happy with this build and this is probably one of my best.
I was initially planning on writing every detail of the log but after awhile you just can't do that.  You have to get the amp to work and build it.

So I could say it is completed but it's never really completed.

I started from the stock JCM800 2204 but after reading and rereading the galactic grounding in Kevin O'conners's TUT3 I had to try this grounding concept.  And went as far as to apply the split filtering mentioned in his book.  I have to say that using this method yielded very very great results.  And any other build I will be using these concept detailed and learned in his book.  I even ended up contacting him directly.  Really cool guy!  I'd recommend his book TUT3 highly.

So the first pic is the fully "completed"  amp and this sounds incredible!  (Mostly thanks to Kevin and his TUT3 book).  Very low noise for a higher gain amp and it has incredible sustain with rich distortion. And I can do pinch harmonics with ease    The initial stock build had should I say crappy sound and feel.  It farted out with faster notes and very hard to sustain the notes and in general it just didn't sound full or "right".  After these changes it made a HUGE difference.  I didn't change the circuit entirely but in fact it was much MUCH improved.   In actuality the amp is not modded extensively for more gain (adding an extra preamp tube..  changing different component values etc.)  In terms of component values everything is pretty much stock except for the first V1 cathode resistor and the 68K instead of the 470K.

With the changes mentioned above and from these changes alone made a really big difference in sustain, noise and it sounds a lot richer.

Thanks for looking!!

[Champ_49]

Here is (was) the amp that was "stock"  with the stock grounding and no split filtering.